Subscriber access provided by LIBRARY OF CHINESE ACAD SCI
Chemical Reviews is published by the American Chemical Society. 1155 Sixteenth
Street N.W., Washington, DC 20036
Upconversion and Anti-Stokes Processes with f and d Ions in Solids
Chem. Rev., 2004, 104 (1), 139-174• DOI: 10.1021/cr020357g • Publication Date (Web): 18 November 2003
Downloaded from http://pubs.acs.org on February 24, 2009
More About This Article
Additional resources and features associated with this article are available within the HTML version:
Links to the 29 articles that cite this article, as of the time of this article download
Access to high resolution figures
Links to articles and content related to this article
Copyright permission to reproduce figures and/or text from this article
Upconversion and Anti-Stokes Processes with f and d Ions in Solids
Franc ¸ois Auzel
GOTR, UMR 7574-CNRS, 1, Place A-Briand, 92195 Meudon Cedex, France
Received February 25, 2003
1. Introduction and Historical Background
2. Energy Transfers between RE Ions: Role of
Energy Diffusion in Up- and Downconversion
2.1. Recall of Basics of Energy Transfer with
Activator in Its Ground State
2.2. Upconversion Processes by Sequential
Energy Transfers (APTE or ETU Process):
Com parison with ESA and Typical Exam ples
3. Upconversion in a Single-Ion Level Description
for APTE (ETU) or ESA and in a Pair-Level One
(Cooperative Effects): Theoretical and
Experim ental Discrim ination
3.1. Three Different Kinds of Pair States
3.2. Fundam ental Difference for Transitions
between Single-Ion States, Dynam ical and
Static Pair States, and Cooperative Pair
3.3. Application of Cooperative Lum inescence;
Theory, and Exam ples
4. Experim ental Results and Their Im plications in
4.1. Recent Upconversion Studies in Lanthanide
(4f) and Actinide (5f) Ion-Doped Solids with
APTE (ETU) and ESA Processes
4.1.1. Pr3+(4f2) Ion
4.1.2. Nd3+(4f3) Ion
4.1.3. Gd3+(4f7) Ion
4.1.4. Dy3+(4f9) Ion
4.1.5. Ho3+(4f10) Ion
4.1.6. Er3+(4f11) Ion
4.1.7. Tm3+(4f12) Ion
4.1.8. Tm2+(4f13) Ion
4.1.9. U4+(5f2) Ion
4.1.10. U3+(5f5) Ion
4.2. Recent Upconversion Studies in
Transition-Metal (3d, 4d, 5d) Ion-Doped
Solids with APTE (ETU), ESA, or
4.2.1. Ti2+(3d2) Ion
4.2.2. Cr3+(3d3) Ion
4.2.3. Ni2+(3d8) and Mn2+(3d5) Ions
4.2.4. Mo3+(4d3) Ion
4.2.5. Re4+(5d3) Ion
4.2.6. Os4+(5d4) Ion
4.3. APTE (ETU) for Display and IR Detection
4.4. General Negative Roles Brought up by
Undesired APTE (ETU) Effects
4.5. APTE (ETU) and ESA Pum ped Lasers
5. Cross-Relaxation and the Photon Avalanche
5.1. Avalanche Process as a Positive Feedback
5.2. Conditions in Order To Observe an
5.3. Er3+−LiYF4as an Avalanche Model
5.4. Photon Avalanche in Er3+−Fluoride Glasses
in Fiber and Bulk Shape
5.5. Avalanche in Codoped System s
5.6. Upconversion Laser with
Multiphonon-Assisted Pum ping Schem e and
6. Perspectives and Future Advances
6.1. Upconversion UV-Tunable Lasers
6.2. NewMaterials for Low-Intensity IR Im aging
6.3. Upconversion Material Intrinsic Bistability
6.4. Hot Em ission and Avalanche Like Co-Doped
6.5. Biological Applications
8. Acknowledgm ents
1. Introduction and Historical Background
Before the 1960s, all anti-Stokes emissions, which
were known to exist, involved emission energies in
excess of excitation energies by only a few kT. They
were linked to thermal population of energy states
above excitation states by such an energy amount.
It was the well-known case of anti-Stokes emission
for theso-called thermal bands or in theRaman effect
for the well-known anti-Stokes sidebands. Thermolu-
minescence, where traps are emptied by excitation
energies of the order of kT, alsoconstituted a field of
anti-Stokes emission of its own. Superexcitation, i.e.,
raising an already excited electron toan even higher
level by excited-state absorption (ESA), was also
known but with very weak emissions. These types
of well-known anti-Stokes processes have been re-
viewed in classical textbooks on luminescence.1
All fluorescence light emitters usually follow the
well-known principle of the Stokes law which simply
states that excitation photons are at a higher energy
than emitted ones or, in other words, that output
photon energy is weaker than input photon energy.
This, in a sense, is an indirect statement that
efficiency cannot be larger than 1. This principle is
139Chem . Rev. 2004, 104, 139−173
10.1021/cr020357g CCC: $48.50©2004 Am erican Chem ical Society
Published on Web 11/18/2003
valid, of course, only when one excited ion system is
In this review wewill discuss anti-Stokes emissions
or upconversion processes for which emission is found
to exceed excitation energies by 10-100 times kT,
which is violating Stokes law in its basic statement.
It will be shown that coupled lanthanide and
uranide f ions and transition-metal d ions, when
embedded in solids, may deviate rather easily from
the above principle, producing upconversion emis-
sions of the anti-Stokes types under moderate to
strong excitation density.
A number of different mechanisms have been
recognized tobeinvolved in upconversion either alone
or in combination.
Besides multistep excitation due toclassical excited-
state absorption (ESA), there is the very efficient
process of upconversion by sequential energy trans-
fers which has been named by Auzel APTE effect (for
addition de photon par transferts d’energie;2this
effect was alsolater termed ETU for energy transfer
upconversion.3This last phenomenon has to be
distinguished from a third process, namely, coopera-
tiveupconversion either between twoions or between
a pair of ions and a third one. Though some aspects
of its theoretical behavior are rather analogous with
upconversion by energy transfers, its efficiency is
usually much weaker. This is because it involves
quasi-virtual pair levels between which transitions
havetobedescribed in a higher order of perturbation
due to their double-operator nature.
A fourth process will alsobeconsidered: thephoton
avalanche effect, also based on sequential energy
transfers but of the downconversion type (usually
called cross-relaxation), whereas the upconversion
step itself is due to ESA.
The various experimental techniques, which allow
distinctions between the behaviors of these various
processes, will be analyzed taking examples from the
With the advent of high energy density laser
sources, these processes have been observed in vari-
ous types of ion-doped solids such as crystals and
glasses in bulk, fiber, or waveguide form; the recent
advances will be encompassed and described there-
The whole field of upconversion in ion-doped sys-
tems can be traced back to an idea of Bloembergen
in 1959,4proposing that infrared (IR) photons could
be detected and counted through sequential absorp-
tion (ESA) within the levels of a given ion in a solid,
that is using superexcitation as a detector. This was
a short proposal for a detector called an infrared
quantum counter (IRQC). In fact, because there was
little chance with incoherent pumping that the same
single doping ion would receive two photons in
sequenceat its given position during thefirst excited-
statelifetime, theexperimental demonstration of this
effect had towait for laser excitations and fiber local
confinement. Some of the first experiments5have
been proved later to be due to energy diffusion
through energy transfers between identical ions.6
The role of energy transfers in upconversion pro-
cesses was not recognized until 1966, when it was
suggested by Auzel that energy transfers between RE
ions could take place between twoions, both of them
being in an excited stateat theenergy transfer initial
step.7Until then, all energy transfers were assumed
to take place from a first ion in an excited state to a
second onein its ground state.8Becauseupconversion
by sequential energy transfers or APTE effect is so
efficient, it could initially be obtained through black-
body excitation or spontaneous diode emission even
before laser sources became commonly available.2
Principles and applications of such upconversion
phosphors have already been presented in several
reviews up to the 1970s by Auzel,2Mita and Naga-
zawa,9Garlick,10and Wright.3Since then, laser
excitation in the IR and/or the use of fibers have
become so easy that upconversion has become a
pervading effect in all RE-doped materials under
high-density IR excitation. Also, another type of
upconversion, namely, the photon avalanche pro-
cess,11,12has been widely investigated in recent years.
Limited aspects of recent progress have partially
been reviewed through the 1980s and 1990s,13-18but
Francois Auzel, bornJuly5, 1938inRoanne(France), graduatedas both
anengineerfromISEP (InstitutSupereurd′ElectroniquedeParis) in1961
and a “Licencie ´ -es Sciences Physique” in 1962 fromthe University of
Paris. Hewas withFrance-TelecomResearchCenter(CNET) from1961
to 1999. There, in 1961, he started working on Nd-doped phosphate
glasses. In 1968, he received his Ph.D. degree fromthe University of
Otto Deutschbein and with Professor Alfred Kastler as adviser; as an
outcom e of this work, he proposed rare-earth-doped fluorophosphate
glasses as laser m aterials withweak OH interactions. During his thesis
(ETU) giving risetoupconversionofinfraredtovisiblelight, using Yb−Er
(greenem ission)andYb−Tm(blueem ission)couples.In1973, hereceived
the Foucault prize from the “Societe ´ Franc ¸aise de Physique" for his
discovery of upconversion processes by energy transfers (APTE ef-
fect)(1965−1966). In1989, the FrenchAcadem y ofScience grantedhim
dem onstration of the existence of Stokes and anti-Stokes m ultiphonon
sidebands fortrivalentlanthanides (1976), theproposalofascalarcrystal
fieldparam eterproportional tothe m axim umsplitting ofa J term(1979),
the first observation of superradiance em ission of a lanthanide (Er ions
at 2.7 µm at 10 K in weakly doped YLF crystals) (1986), the
room -tem perature avalanche effect of Er-doped glasses and crystals
(1993), andthesaturationeffectofm ultiphonondecays inglasses (1996).
He has been a part-tim e Professor at Ecole Centrale des Arts et
Manufactures (1971−99) andat Orsay University (DEA Ecole Polytech-
nique-Lab. Aim eCotton) (1990−99). Hecreatedandheadedthe“Groupe
d′OptiquedesTerresRares”, ateambelongingtobothCNRS andCNET,
until his retirem ent from CNET in 1999. He is currently a voluntary
researcher at CNRS and a consultant for active optical m aterials.
140 Chem ical Reviews, 2004, Vol. 104, No. 1Auzel
the general field has recently evolved from the rare-
earth (4f) consideration toward the use of actinide
(5f) and transition-metal (3d, 4d, 5d) ions with a
systematic use of laser excitation at precisely defined
This evolution justifies the present review.
Because it appears that the language in the up-
conversion field is still not completely fixed, possibly
inducing misinterpretation, the basic processes of
energy transfers, cooperative processes, and their
application toupconversion together with their more
recent evolutions and selected examples of applica-
tions will be presented in reference to the accepted
vocabulary proposed by the pioneers. Some of the
original papers in this field were reprinted in 1998
in a collective edition.19
2. Energy Transfers between RE Ions: Role of
Energy Diffusion in Up- and Downconversion
In the following, the mutual interactions between
ions are the key feature.
When the concentration of active ions is increased,
long before the appearance of new lines due to pairs
or modifications in radiative transition probabilities,
a migration of energy between the centers is found.
We are going to study this now, assuming that
multiphonon decays and the radiative transitions
remain one-center processes.
As single f and d ions properties are supposed to
be known, multiion processes, namely, energy trans-
fers, are now dealt with. Energy transfer occurs in a
system where absorption and emission do not take
place within the same center. It may occur without
any charge transport. Then one may distinguish
between radiative and nonradiative, resonant, and
phonon-assisted energy transfer. Theoretical ap-
proaches start from a microscopic point of view with
a macroscopic result averaged over all the centers in
the sample. In fact, an energy transfer between two
given ions cannot by itself increase efficiency; it can
only provide a new excitation wavelength range with
a reduced efficiency since it consists of the product
of twoprocesses with intrinsic efficiency less than or
equal to1. Overall efficiency improvement by energy
transfers is gained only from the spatial averaging
due to the macroscopic process of diffusion.
2.1. Recall of Basics of Energy Transfer with
Activator in Its Ground State20,21
In a schematic way, the different microscopic
energy transfer processes between two ions can be
presented as in Figure 1. Following the traditional
vocabulary of the phosphor field, the ion being first
directly excited is called a senzitizer (S); some people
would call it a donor, but because f and d ions may
alsobeimbedded in semiconductors, such vocabulary
leads to confusion and is not retained here. The ion
to which energy is transferred and which emits the
output photon is called an activator; in a synonymous
manner, it is some times termed an acceptor. To
avoid any ambiguity with the semiconductor field,
this vocabulary is not retained in the following.
One usually distinguishes radiative transfer (Fig-
ure1a), nonradiativeenergy transfer (Figure1b), and
multiphonon-assisted energy transfer (Figure 1c). S
and A may also be identical ions, and nonradiative
transfer may give rise to self-quenching by cross-
relaxation (Figure 1d).
When energy transfer is radiative (Figure 1a), real
photons are emitted by the sensitizer ions (S) and
are then absorbed by any activator ions (A) within a
photon travel distance. As a consequence, such
transfer depends on the shape of the sample.
Moreover, according to the degree of overlap be-
tween theemission spectrum of thesensitizer (S) and
the absorption spectrum of the activator (A), the
structure of the emission spectrum of the sensitizer
will change with activator concentration. Since pho-
tons are emitted anyway, the sensitizer lifetime is
independent of the activator concentration. These
three facts are the criteria used to distinguish
between radiative and nonradiative resonant energy
Probability for such transfer between two ions at
a sufficiently large distance R is found to be20
where τSis the sensitizer lifetime and σAthe absorp-
tion-integrated cross section. The integral represents
the spectral overlap between A and S. It should be
noted that thedistancedependencegoes as R-2. Such
resonant radiative transfer may permit long-range
energy diffusion between identical ions and gives rise
to photon-trapping effects of the same type as the
ones observed a long time ago in gases.22Trapping
effects increase the apparent experimental lifetime,
and τShas to be measured on thin and lightly doped
samples. These effects are particularly strong in Cr3+
Let us consider the simple case of two ions, each
with one excitable electronic state separated from its
electronic ground state by nearly equal energy; it is
the case described in Figure 1b. With suitable
F igure 1. Various basic energy transfer processes between
two ions considered before 1966: note that activator ion
(A) receiving the energy from the sensitizer (S) is initially
in its ground state. Cross-relaxation is the special case
where S is identical to A. Doubled arrows symbolize the
Coulombic interaction: (a) radiative resonant transfer; (b)
resonant nonradiative transfer; (c) phonon-assisted non-
radiative transfer; (d) cross-relaxation special case of
Upconversion and Anti-Stokes ProcessesChem ical Reviews, 2004, Vol. 104, No. 1 141
interaction between thetwoelectronic systems, which
is the case for nonradiative energy transfer, the
excitation will jump from one ion tothe other before
one is able to emit a quantum of fluorescence. The
mutual interactions are Coulomb interactions of the
van der Waals type between the two ions. Fo ¨rster,26
whofirst treated such a casetheoretically by quantum-
mechanical theory, considered the dipole-dipole
interaction. He assumed that the interaction is
strongest if for both transitions electric-dipole tran-
sitions are allowed.26The interaction energy is then
proportional to the inverse of the third power of the
interionic distance and the transfer probability is
HSA) electric dipole-dipoleinteraction Hamiltonian,
proportional tothe inverse third power of ion separa-
FE ) density of states provided by the vibrational
motion contributing to the line broadening of the
pSAis proportional tothe inverse sixth power of the
ion separation. The wave functions to be considered
for the matrix element describe an initial state of the
system with the sensitizer in its excited state and
the activator in its ground state, the final state
having the sensitizer in its ground state and the
activator in its excited state.
Therefore, the transfer probability can be written
whereτSis theactual lifetimeof thesensitizer excited
state, including multiphonon radiative decay, and R0
is the critical transfer distance for which excitation
transfer and spontaneous deactivation of the sensi-
tizer have equal probability.
However, Dexter pointed out27that this theory
should be extended to include higher multipole and
exchange interactions. In fact, for an isolated atom,
one can consider the transition probability as de-
creasing as (a0/λ)2n, where a0 is the Bohr radius, λ
the wavelength, and n an integer. However, in an
energy transfer process with a dependence on near-
zoneinteractions, thetransition probabilities drop off
as (a0/F)2n, whereF is theseparation of theinteracting
ions. F can be as much as 3 orders of magnitude
smaller than λ, so that the energy transfer effect
tends tobe more pronounced in systems with forbid-
den transitions.27This holds true for ions for which
transitions to first order are forbidden, such as
transition-metal and lanthanide ions.
The energy transfer probability for electric multi-
polar interactions can be more generally written as27
where s is a positive integer taking the following
s ) 6 for dipole-dipole interactions,
s ) 8 for dipole-quadrupole interactions,
s ) 10 for quadrupole-quadrupole interactions.
It should be noted that for dipole-dipole interac-
tions, the difference between radiative and nonra-
diative resonant transfer lies essentially in the fact
that for radiative transfer there is no critical R0
depending only upon concentration. The variation
goes as R-2instead of R-6, and the sensitizer lifetime
does not depend on the distance R.
Now, tobe able tocalculate effectively pSA(R), eq 4
is not very useful because R0 cannot be easily
obtained theoretically. Applying Racah’s tensorial
methods at thebeginning of thecalculation of Dexter,
eq 2, allows development of calculations analogous
to J udd’s theory for radiative transitions. The case
of themultipolar interactions was treated in this way
by Kushida28and extended by Pouradier and Auzel29
tomagnetostatic and exchange interactions, showing
that a single general formula could be used for all
types of energy transfers.
The general form obtained is then
where gS*(gA0) is the degeneracy of the S*(A0) level,
γS(E)(ΓA(E)) is the normalized line shape function of
emission (absorption) spectrum, U(l)are the tensorial
operators already seen for J udd’s theory. |Cl1l2|2can
be considered as a parameter analogous to J udd Tλ
(Ωλ) for oscillator strength.
This expression of the transfer probability has the
(1) Radial and orbital parts have been separated.
(2) Only a few reduced matrix elements need be
calculated. They are the same for the three interac-
tions we consider (for any interaction leaving spins
(3) Comparison between twodifferent interactions
can be made through comparison of Cl1l2coefficients.
They are independent of the states involved in the
transfer, and we call them El1l2, Ml1l2, and Xl1l2for
electrostatic, magnetostatic, and exchange interac-
(4) Forced electric-dipoletransitions, as calculated
by J udd’s method, can be included in eq 5.
(5) This expression also gives a single mathemati-
cal form regardless of the interaction, which is a
convenient result. The somewhat complicated ex-
pressions for the different Cl1l2of 4f electrons are
given in ref 29. However. we can note the following.
(a) For electrostatic interaction El1l2, the l1) 1 and
l2) 1 term, corresponding to dipolar-dipolar inter-
action, is zero in first order, which makes the
introduction of J udd’s Tλparameters necessary. The
El1l2values are typically between E22≈ 30 cm-1for
I )∫γS(E)ΓA(E) dE (6)
142 Chem ical Reviews, 2004, Vol. 104, No. 1 Auzel
quadrupole-quadrupole intensities and E66 ≈ 3 ×
10-1cm-1, but all contain some dipole-dipole part
due to the Tλ.
(b) For magnetostatic interactions (Ml1l2), only
terms with li ) 1, 3, and 5 are nonzero. They have
the order of magnitude M11≈ 1 cm-1and M55≈ 2 ×
(c) For exchange interactions (Xl1l2), we have 1 e l1
e 6, giving estimates of 1-10-1cm-1for the coef-
Theseresults show that exchangeor magnetostatic
interactions can be found in cases of small dipole-
dipoleand quadrupoleelectrostatic interactions if the
matrix elements allow them.
If now we consider two ions with excited states of
different energies (Figure 1c), the probability for
energy transfer should drop tozerowhen the overlap
integral ∫gS(ν)gA(ν) dν vanishes. However, it has been
experimentally found that energy transfer can take
place without phonon-broadened electronic overlap
provided that the overall energy conservation is
maintained by production or annihilation of phonons
with energies approaching kΘd, where Θd is the
Debye temperature of the host matrix.30Then for
small energy mismatches (100 cm-1), energy transfer
assisted by one or two phonons can take place.31
However, for energy transfers between rare earths,
energy mismatches as high as several thousand
reciprocal centimeters are encountered. This is much
higher than the Debye cutoff frequency found in
normally encountered hosts, so multiphonon phe-
nomena have to be considered here.
Miyakawa and Dexter32showed that it is still
legitimate towrite the probability of energy transfer
in the form of eq 2, where F(E) is taken as SSA, the
overlap of the line shape functions for emission by
ion S and absorption by ion A, including the phonon
sidebands in the line shape. It is necessary to
consider each partial overlap between the m-phonon
emission line shape of ion S and the n-phonon
absorption line shape of ion A. A physical meaning
tothis mathematical assumption, criticized in ref 31,
has been given by Auzel’s experimental demonstra-
tion33of the existence of multiphonon sidebands for
trivalent rare-earth ions. Their existence could be
revealed by laser excitation spectroscopy even though
they had not been seen by usual absorption spectros-
copy because of their very small electron-phonon
Along the same lines as for vibronic sideband
studies, SSA can be expressed as follows
where S0Sand S0Aare the respective lattice coupling
constants for the ions S and A, N is the order of the
multiphonon process with N ) ∆E/pωm, ∆E is the
energy mismatch between both ions, and pωmis the
phonon cutoff frequency. σSA (0,0;E) is the zero-
phonon overlap integral between S and A. Equation
7 contains a Pekar function of the Poisson type.20
The expression for SSA with an energy mismatch
of ∆E for small S0constants and for an occupation
number n j ) (exp(pω/kT) - 1)-1, not exceeding 1 at
theoperating temperature, can beapproximated with
Stirling’s formula by
where SSA(0) is the zero-phonon overlap between S
and A in the case where there is noenergy mismatch
between the two ions. ? is given by
? ) (pω)-1log N/S0(n j + 1) - log(1 +SOA
= RS- γ ≈ RS- log 2
involving RSthe nonradiative decay parameters and
assuming identical electron-phonon coupling for ions
A and S. This exponential dependence on energy
mismatch is well substantiated by experiments.34
Up to this point we have been dealing with the
microscopic case of two ions interacting with one
another. To discuss the case of real macroscopic
samples with many ions and to obtain a link with
experimental facts, a statistical analysis of theenergy
transfer is necessary.
We have then tothink about the overlap integrals
that arisein all transfers between twoions as already
seen. In the microscopic case we are sure that the
involved line shapes can be only due to some homo-
geneous broadening even for transfer between two
identical ions in different lattices sites.
In the macroscopic case, we can measure absorp-
tion and emission spectra taking into account all
broadening processes averaged over the whole sample;
for instance, the inhomogeneous broadening process
duetoemission and absorption at centers in different
lattice sites. Then the overlap integral measured
experimentally from the usual spectra is a measure
in excess of the real overlap since we take into
account emission and absorption of centers at any
distances, even those which cannot interact. The
error is the largest for the processes occurring at
shortest interacting distances (exchange) and a con-
trario is certainly negligible for radiative transfer,
since photons can travel a much larger distance than
the spread of the spatial disorder. The error is also
smaller for systems with small inhomogeneous broad-
ening and having centers in only one type of lattice
site, that is, without disorder.
Fluorescenceline-narrowing techniques (FLN) could
give some idea about the homogeneous part of an
emission line, but the statistical analysis for the
whole sample should still be performed. Supposing
only a sensitizer-activator interaction, an averaged
transfer efficiency can be calculated.27This has been
studied in some detail by Inokuti and Hirayama.35
They considered the number of activators located at
random in a spherearound a sensitizer in such a way
that the activator concentration is constant when the
volumeof thesphereand thenumber of activator ions
considered goes to infinity. Then the averaged prob-
e-(SOS+ SOA)(SOS+ SOA)N
SSA(∆E) ) SSA(0)e-?∆E
Upconversion and Anti-Stokes ProcessesChem ical Reviews, 2004, Vol. 104, No. 1 143
in avalanche systems (see section 5.3) has been
described within the framework of population rate
equations. Then it appears more in accordance with
physical reality not toconsider coherent field coupling
as the root of observed bistability. This is implicitly
recognized for Cs3Y2Br9:Yb in a later paper284point-
ing out the analogy with avalanche bistability and
describing the effect through population rate equa-
tions. As the temperature changes, sodothe overlap
integrals ruling the RE-RE energy transfers, which
provide the necessary nonlinear feedback effect.
Clearly, it can also be the only explanation for the
high-temperature (430 K) hysteresis loops that had
been initially observed in WO4Na0.5Yb0.5:2%Er.283
From this result and the fact that the hysteresis
behavior is produced at the Yb3+ion, it can be
predicted that all upconversion systems with Yb as
a sensitizer could show thermal hysteresis. For the
last 2 years, thethermal explanation has clearly been
retained as explained by Gamelin et al.285and said
to be due to the variable thermal absorption proper-
ties of Yb3+. It is described as a thermal avalanche
with a thermal cross-relaxation in analogy with the
photon avalanche described above in section 5.1.
According toFigure41, theequivalent of R1, theweak
ground-state absorption, is a nonresonant absorption
between2F7/2to2F5/2. The resonant absorption term
R2 is from a Stark level of2F7/2 to a Stark level of
2F5/2; the cross-relaxation term, Cn1n3of Figure 25,
is produced by the heat released within the Stark
levels of2F5/2by the phonon emission, which in turn,
by absorption of phonons, populates a higher Stark
excited state of2F7/2. This is the loop of this thermal
avalanche. An external thermal triggering term,
equivalent to σ0ΦIR of Figure 25, is provided by the
external temperature variable T of the experiment.
As seen in section 5.1, one can predict that the
threshold and the hysteresis will be steeper and the
time constant longer for weaker R1/R2 ratios. Con-
sequently, we can propose here that a large crystal
field should be better for higher temperature obser-
vations and that it should be the case for hard oxides
and YAG in particular.286
At any rate, the thermal avalanche convincing
explanation certainly describes in a correct way the
published observations including the one of 1967,283
which was was thought to be due to the thermal
behavior of theoverlap integral between coupled Yb-
Er ions and had been unexplained until now!
6.4. Hot Emission and Avalanche Like Co-Doped
Here, it is interesting to discuss a not yet com-
pletely elucidated new phenomena recently observed
by Bednarkiewicz and Strek287in an upconversion
study of Nd3+-Yb3+codoped YAG nanocrystallite
ceramics. Under laser diode pumping at 976 nm into
theYbabsorption, visibleorangeantiStokes emission
is observed at 300 K with broadened features at 579
nm from4G5/2-4G7/2, 690 nm from4F9/2, 757 nm from
4F7/2-4S3/2, and 813 nm from4F5/2-2H9/2, all transi-
tions tothe Nd3+4I9/2ground state. These emissions
decrease with decreasing temperature. Those visible
emissions are described by a, Pn, law for output
versus excitation with, n linearly depending on the
energy gap above4F3/2as shown in Figure 42 There
is alsoan establishing time constant increasing with
the order parameter, n, reaching 1.5 s for n ) 4. It
was recognized that because the metastable charac-
ter of4F3/2 is reduced by back transfer to Yb, the
multiphonon process shown which could have ex-
plained the result of Figure 42 cannot be retained;
moreover, dividing the energy gap between4F3/2and
emitting states by n provides virtual phonon energies
not existing in YAG.
No real explanation is presented in ref 287, and
this result is still a question. Though not mentioned
by theauthors, wethink, however, that thelong time
transient is the clear signature of avalanche pro-
cesses which have yet to be analyzed in detail.
6.5. Biological Applications
Very recently upconversion applications of the
APTE (ETU) systems Yb-Er and Yb-Tm have been
devised by Zilmans et al.288for detection of cell and
tissue surface antigens as luminescent bioassays.
Submicrometer-sized phosphor crystals (200-400
nm) of the usual oxysulfide, fluoride, gallate, and
silicate types doped with Yb-Er and Yb-Tm couples
are considered. The main advantage is that IR-
upconverting phosphors are excited by wavelengths
that cannot excite the natural biological materials,
soproviding a better detection contrast with respect
toautofluorescence than the more usual luminescent
bioassays working in the Stokes emission mode. The
F igure 41. Yb3+simplified energy scheme according to
the simplified three-level energy scheme of Figure 25 for
avalanche with a thermal cross-relaxation process explain-
ing the thermal hysteresis loop of 285. The external
triggering term corresponds to the temperature variable
of the experiment.
F igure 42. Upconversion power law indexes versus energy
gap between emitting states and4F3/2(Nd3+) in Yb,Nd:YAG.
(Reprinted with permission from ref 287. Copyright 2002
Institute of Physics Publishing.)
Upconversion and Anti-Stokes ProcessesChem ical Reviews, 2004, Vol. 104, No. 1 169
upconversion method overcomes many of the limita-
tions of the common reporters used in immunocy-
A still more recent result that could be connected
toprevious application is the dissolution of nanopar-
ticles (6-8 nm) of Yb-Er- and Yb-Tm-doped LuPO4
as colloids in chloroform solutions.289Because of the
inherent high efficiency of the APTE (ETU) effect,
such colloids can show green, red, and blue upcon-
version in the liquid phase for the first time.
The general principles of upconversion have been
presented in a self-contained way together with
typical examples. Because these effects are now so
generally observed with the general use of laser
excitations, it was thought tobe important todistin-
guish them in precise ways in order for future
researchers tostart from well-established definitions
and to speak a common language.
Besides a didactical approach, I tried to present
most of all the recent important results if not in an
exhaustive way at least in a complete way for all
important turning points.
If therewas somegeneral philosophy toderivefrom
this review, it would be that upconversion is an
endless field and that some features are becoming
as common as plain Stokes luminescence. Some
aspects of this reviewed field though not really
exploited at some time may become important with
more refined experiments and availability of new
technologies. Also, the implied processes may help
understand other aspects of optical processes in RE-
An example could be the presently considered
photon-cutting effect,84-88just the opposite of APTE
(ETU) upconversion, which may open the way tonew
efficient lighting systems. Theoppositeof cooperative
luminescence, cooperative quenching, recently dis-
covered, may explain some of the yet not understood
features of concentration quenching.83
From an applied point of view, it is observed that
with the general use of lasers and the easiness in
observing visible to the naked eye upconversion, too
few people have found it necessary to measure
efficiencies in order to be able to compare quantita-
tively the various proposed upconversion systems.
This should bedonetopush upconversion beyond the
qualitativeapproach that still toooften characterizes
it. Most of the recently proposed systems can be
observed only at low temperature and no efficiency
values are provided. One can alsoverify through this
review that, as is often in science, the most efficient
systems aretheones discovered at first, heretheYb-
Er and the Yb-Tm systems.7
It is a pleasure to acknowledge a number of
researchers who have kindly sent me their reprints
and havesohelped mein writing this review. I would
like to mentioned particularly Dr. J unichi Owaki
(NTT), Pr. Gu ¨nter Huber (Hambourg University), Pr.
J ohann Heber (Darmstadt University of Technology),
Drs.Valery Smirnov and Alina Man’shina (Russian
Center for Laser Physics), Pr. Georges Boulon and
Dr. Marie-France J oubert (Universite ´de Lyon), Pr.
Hans Gu ¨del (Bern University), Dr. Markus Pollnau
(Lausanne University), Pr. Wieslaw Srek (Low Tem-
perature Physic Institute, Wrawclaw), and Pr.
J oaquim Fernandez (Universidad del Pais Vasco,
Bilbao). I would like to thank also Dr. Marco Betti-
nelli (University di Verona, Italy) for kindly pointing
to me the bioassay application and Pascal Gerner
(Bern University) for providing me with the very
recent last reference. Many thanks also for my good
friend Peter Lewis for reading over the whole text.
Last but not least, thanks are due tomy wife, Odile,
for having accepted that I divert a lot of leisure time
for that work.
(1) Leverenz, H. W. Introduction to Luminescence of Solids; Dover
Publications: New York, 1968.
(2) Auzel, F. Proc. IEEE 1973, 61, 758.
(3) Wright, J . Up-conversion and excited-state energy transfer in
rare-earth doped materials. In Radiationless Processes in Mol-
ecules and Condensed Phases; Fong, F. K., Ed.; Topics in Applied
Physics; Springer: New York, 1976; Volume 15, p 239.
(4) Bloembergen, N. Phys. Rev. Lett. 1959, 2, 84.
(5) Brown, M. R.; Thomas, H.; Williams, J . M.; Woodwards, R. J . J .
Chem. Phys. 1969, 51, 3321.
(6) Auzel, F. J . Lumin. 1984, 31/ 32, 759.
(7) Auzel, F. C. R. Acad. Sci. (Paris) 1966, 262, 1016. Auzel, F. C.
R. Acad. Sci. (Paris) 1966, 263, 819.
(8) Van Uitert, L. G.; J ohnson, L. F. J . Chem. Phys. 1966, 44, 3514.
(9) Mita, Y.; Nagasawa, E. NEC Res. Dev. 1974, 33, 61.
(10) Garlick, G. F. J . Contemp. Phys. 1976, 17, 127.
(11) Chivian, J . S.; Case W. E.; Eden, D. D. Appl. Phys. Lett. 1979,
(12) Case, W. E.; Koch, M. E.; Kueny, A. W. J . Lumin. 1990, 45, 351.
(13) Auzel, F. Semiconductor Optoelectronics; Wiley and PWN: New
York and Warszawa, 1980; Chapter 10, p 233. Auzel, F. J .
Lumin. 1990, 45, 341. Auzel, F. In Luminescence: Phenomena,
Materials and Devices; Rao, R. P., Ed.; Nova Science Pub.: New
York, 1992; p 33. Auzel, F. In Nonlinear Spectroscopy of Solids;
Advances and Applications; DiBartolo, B., Bowlby, B., Eds.;
Plenum Press: New York, 1994; p 531.
(14) Huber, G.; Heumann, E.; Sandrok, T.; Petermann, K. J . Lumin.
1997, 72/ 74, 1.
(15) Gamelin, D. R.; Gu ¨del, H. U. Acc. Chem. Res. 2000, 33, 235.
(16) Hehlen, M. P.; Phillips, M. L. F.; Cockroft, N. J .; Gu ¨del, H. U.
Encyclopedia of Materials; Science and Technology; Elsevier
Science Ltd.: New York, 2001; p 9956.
(17) Gamelin, D. R.; Gu ¨del, H. U. Top. Curr. Chem. 2001, 214, 1.
(18) Auzel, F. SPIE 2001, 4766, 179. Auzel, F. In Spectroscopic
properties of rare-earths in optical materials; Liu, G. K., J acquier,
B., Eds.; Springer-Verlag: New York, 2003; Chapter 5.
(19) Selected papers on Photoluminescenceof Inorganic Solids; Weber,
M., Ed.; SPIE Milestone Series, Vol. MS150; SPIE: Bellingham,
(20) Auzel, F. Multiphonon processes, cross-relaxation and upcon-
version in ion activated solids, exemplified by minilaser materi-
als. In Radiationless Processes; DiBartolo, B., Goldberg, V., Eds.;
Plenum Publishing Co.: New York, 1980; p 213.
(21) Henderson, B.; Imbusch, G. F. Optical Spectroscopy of Inorganic
Solids; Clarendon Press: Oxford, 1989; p 445.
(22) Milne, E. A. J . London Math. Soc. 1926, 1, 1.
(23) Varsanyi, F.; Wood, D. L.; Schawlow, A. L. Phys. Rev. Lett. 1959,
(24) Auzel, F. Ann. Telecom. (France) 1969, 24, 363.
(25) Auzel, F.; Bonfigli, F.; Gagliari, S.; Baldacchini, G. J . Lumin.
2001, 94/ 95, 293.
(26) Fo ¨rster, T. Ann. Phys. 1948, 2, 55.
(27) Dexter, D. L. J . Chem. Phys. 1953, 21, 836.
(28) Kushida, T. J . Phys. Soc. J pn. 1973, 34, 1318.
(29) Pouradier, J . F.; Auzel, F. J . Phys. (France) 1978, 39, 825.
(30) Axe, J . D.; Weller, P. F. J . Chem. Phys. 1964, 40, 3066.
(31) Orbach, R. Optical Properties of Ions in Solids; DiBartolo, B.,
Ed.; Plenum Press: New York, 1975; p 445.
(32) Miyakawa, T.; Dexter, D. L. Phys. Rev. 1971, B1, 70.
(33) Auzel, F. Phys. Rev. 1976, B13, 2809.
(34) Yamada, N.; Shionoya, S.; Kushida, T. J . Phys. Soc. J pn. 1972,
(35) Inokuti, M.; Hirayama, F. J . Chem. Phys. 1965, 43, 1978.
170 Chem ical Reviews, 2004, Vol. 104, No. 1 Auzel
(36) Barthem, R. B.; Buisson, R.; Vial, J . C. J . Phys. 1985, 46, C7-
(37) Yokota, M.; Tanimoto, O. J . Phys. Soc. J pn. 1967, 22, 779.
(38) Weber, M. J . Phys. Rev. 1971, B4, 2932.
(39) Grant, W. J . C. Phys. Rev. 1958, 109, 648.
(40) Auzel, F. Mater. Res. Bull. 1979, 14, 223.
(41) Snitzer, E.; Woocock, R. Appl. Phys. Lett. 1965, 6, 5.
(42) Auzel, F.; Deuschbein, O. Z. Naturfosch. 1969, 24a, 1562.
(43) Ovsyankin, V. V.; Feofilov, P. P. Sov. Phys. J ETP Lett. 1966, 4,
(44) Hewes, R. A.; Sarver, J . F. Phys. Rev. 1969, 182, 427.
(45) Pollnau, M.; Gamelin, D. R.; Lu ¨thi, S. R.; Gu ¨del, M. Phys. Rev.
2000, B61, 3337.
(46) Rios Leite, J . R.; de Araujo, C. B. Chem. Phys. Lett. 1980, 73,
(47) Bonneville, R.; Auzel, F. Opt. Commun. 1976, 18, 51.
(48) Ovsyankin, V. V.; Fedorov, A. A. Opt. Spectrosc. 1981, 50, 565.
(49) Mita, Y.; Ide, T.; Katase, T.; Yamamoto, H. J . Lumin. 1997, 72/
(50) Goldner, P.; Pelle ´, F. J . Lumin. 1994, 60/ 61, 651.
(51) Auzel, F.; Pecile, D.; Morin, D. J . Electrochem. Soc. 1975, 122,
(52) Auzel, F.; Pecile, D. C. R. Acad. Sci. Paris 1973, 277B, 155.
(53) Silver, J .; Martinez-Rubio, M. I.; Ireland, T.G.; Fern, G. R.;
Withnall, R. J . Phys. Chem. 2001, B105, 948.
(54) Silver, J .; Martinez-Rubio, M. I.; Ireland G. R.; Withnall, R. J .
Phys. Chem. 2001, B105, 7200.
(55) Ovsyankin, V. V. Spectroscopy of Solids Containing Rare-Earth
Ions; Kaplyanskii, A. A., MacFarlane, R. M., Eds.; North-
Holland: Amsterdam, 1987; p 405.
(56) Orlovskii, Y. U.; Basiev, T. T.; Papashvili, A. G.; Voroev, I. N.;
Alimov, O. K.; Osiko, V. V.; Heber, J . SPIE 2001, 4766, 204.
(57) Gamelin, D. R.; Lu ¨thi, S. R.; Gu ¨del, H. U. J . Phys. Chem. 2000,
B104, 11045. Lu ¨thi, S. R.; Hehlen, M. P.; Riedener, T.; Gu ¨del,
H. U. J . Lumin. 1998, 76/ 77, 447.
(58) Auzel, F.; Dexpert-Ghys, J .; Gauthier, C. J . Lumin. 1982, 27, 1.
(59) Vial, J . C.; Buisson, R.; Madeore, F.; Poirier, M. J . Phys. (France)
1979, 40, 913.
(60) Dexpert-Ghys, J .; Auzel, F. J . Chem. Phys. 1984, 80, 4003.
(61) Nakazawa, E.; Shionoya, S. Phys. Rev. Lett. 1970, 25, 1710.
(62) Cockroft, N. J .; J ones, G. D.; Syme, R. W. G. J . Lumin. 1989,
(63) Varsanyi, F; Dieke, G. H. Phys. Rev. Lett. 1961, 7, 442.
(64) Van der Ziel, J . P.; Van Uitert, L. G. Phys. Rev. 1969, 180, 343.
(65) Stavola, M.; Dexter, D. L. Phys. Rev. 1979, B20, 1867.
(66) Livanova, L. D.; Saitkulov, I. G.; Stolov, A. L. Sov. Phys. Solid
State 1969, 11, 750.
(67) Ostermayer, F. W., J r.; Van Uitert, L. G. Phys. Rev. 1970, B1,
(68) Auzel, F.; Meichenin, D.; Pelle ´, F.; Goldner, P. Opt. Mater. 1994,
(69) Heber, J .; Nikitin, S. I.; Demirbilek, R.; Papashvili, A. G.;
Vorobev, I. N.; Alimov, O. K.; Orlovskii, Y. V.; Orlovskaya, E.
O. SPIE 2001, 4766, 218. Scha ¨fer, U.; Neukum, J .; Bodenschatz,
N.; Heber, J . J . Lumin. 1994, 60/ 61, 633.
(70) Noginov, M. A.; Loutts, G. B.; Steward, C. S.; Lucas, B. D.; Fider,
D.; Peters, V.; Mix, E.; Huber, G. J . Lumin. 2002, 96, 129.
(71) Blixt, P.; Nilsson, J .; Carlkna ¨s, J .; J askorzynska, B. IEEE Trans.
Photon Techn. 1991, 3, 996.
(72) Auzel, F. J . Lumin. 1984, 31/ 32, 759.
(73) Auzel, F. In Rare-Earth Spectroscopy; Trzebiatowska, B., Leg-
endziewicz, J ., Strek, W., Eds.; World Scientific: Singapore, 1985;
(74) Rand, S. C.; Lee, L. S.; Schawlow, A. L. Opt. Commun. 1982,
(75) Lee, L. S.; Rand, S. C.; Schawlow, A. L. Phys. Rev. 1984, B29,
(76) Valiente, R.; Wenger, O.; Gu ¨del, H. Chem. Phys. Lett. 2000, 320,
(77) Valiente, R.; Wenger, O.; Gu ¨del, H. Phys. Rev. 2001, B63,
(78) Gerner, P.; Wenger, O.; Valiente, R.; Gu ¨del, H. Inorg. Chem.
2001, 40, 4534.
(79) Valiente, R.; Wenger, O.; Gu ¨del, H. J . Chem. Phys. 2002, 116,
(80) Salley, G. M.; Valiente, R.; Gu ¨del, H. J . Lumin. 2001, 94/ 95,
(81) Salley, G. M.; Valiente, R.; Gu ¨del, H. J . Phys.: Condens. Matter
2002, 14, 5461.
(82) Strek, W.; Bednarkiewicz, A.; Deren, P. J . J . Lumin. 2001, 92,
(83) Dexter, D. L. Phys. Rev. 1957, 108, 630. Dexter, D. L. Phys. Rev.
1962, 126, 1962.
(84) Basiev, T.T.; Dorochenko, M. E.; Osiko, V. V. J ETP Lett. 2000,
(85) Vegh, R. T.; Donker, H.; van Loef, E. V. D.; Oskam, K. D.;
Meijerink, A. J . Lumin. 2000, 87/ 89, 1017.
(86) Wegh, T. T.; Donker, H.; Meijerink, A.; Lamminma ¨ki, R. J .;
Ho ¨lsa, J . Phys. Rev. 1997, B56, 13841.
(87) Wegh, R. T.; Donker, H.; Oskam, K. D.; Meijerink, A. J . Lumin.
1999, 82, 93.
(88) Wegh, R. T.; Meijerink, A. Acta Phys. Pol. 1996, A90, 333.
(89) Weegh, R. T.; Donker, H.; Oskam, K. D.; Meijerink, A. Science
1999, 283, 663.
(90) Strek, W.; Deren, P.; Bednarkiewicz, A. J . Lumin. 2000, 87/ 89,
(91) Strek, W.; Deren, P. J .; Bednarkiewicz, A.; Kalisky, Y., Bou-
langer, P. J . Alloys Compd. 2000, 300/ 301, 180.
(92) Orlovskii, Y. V.; Basiev, T. T.; Papashvili, A. G.; Vorobev, I. N.;
Alimov, O. K.; Osiko, V. V.; Heber, J . J . Lumin. 2002, 99, 223.
(93) Delevaque, E.; Georges, T.; Monerie, M.; Lamouler, P.; Bayon,
J . F. IEEE Photon Techn. Lett. 1993, 5, 73.
(94) Maurice, E.; Monnom, G.; Dussardier, B.; Ostrowsky, D. B. Opt.
Lett. 1995, 20, 2487.
(95) Auzel, F. J . Lumin. 1990, 45, 341.
(96) Goldner, P.; Pelle ´, F.; Meichenin, D.; Auzel, F. J . Lumin. 1997,
(97) Goldner, P.; Pelle ´, F.; Auzel, F. J . Lumin. 1997, 72/ 74, 901.
(98) Auzel, F.; Goldner, P. Opt. Mater. 2001, 16, 93.
(99) Schaudel, B.; Goldner, P.; Prassas, M.; Auzel, F. J . Alloys Compd.
2000, 300/ 301, 443.
(100) Remillieux, A.; J acquier, B. J . Lumin. 1996, 68, 279.
(101) Balda, R.; Fernandez, J .; Saez de Ocariz, I.; Voda, M.; Garcia,
A. J . Phys. Rev. 1999, B59, 9972.
(102) Fernandez, J .; Balda, R.; Mendorioz, A; Garcia-Adeva, A. J . J .
Phys. Condens. Matter 2001, 13, 10347. Balda, R.; Saez de
Ocariz, I.; Fernandez, J .; Fdez-Navarro, J . M.; Arriandaga, M.
A. J . Phys. Condens. Matter 2000, 12, 10623.
(103) J u, J . J .; Ro, J . H.; Cha, M. J . Lumin. 2000, 87/ 89, 1045.
(104) Kim, S. I.; Yun, S. I. J . Lumin. 1994, 60/ 61, 233.
(105) Malinovski, M.; J oubert, M. F.; J acquier, B. J . Lumin. 1994, 60/
(106) Hirao, K.; Higuchi, M.; Soga, N. J . Lumin. 1994, 60/ 61, 115.
(107) Deren, P. J .; Mahiou, R.; Strek, W.; Bednarkiewicz, A.; Bertrand,
G. Opt. Mater. 2002, 19, 145.
(108) Balda, R.; Sanz, M.; Fernandez, J .; Fdez-Navarro, J . M. J . Opt.
Soc. Am. 2000, B17, 1671.
(109) Fernandez, J .; Balda, R.; Mendorioz, A.; Sanz, M.; Adam, J . L.
J . Non-Cryst. Solids 2001, 287, 437.
(110) Fernandez, J .; Balda, R.; Sanz, M.; Lacha, L. M.; Oleaga, A.;
Adam, J . L. J . Lumin. 2001, 94/ 95, 325.
(111) Acioli, L. H.; Guo, J . T.; de Araujo, C. B.; Messaddeq, T.;
Aegerter, M. A. J . Lumin. 1997, 72/ 74, 68.
(112) Balda, R.; Sanz, M.; Mendorioz, A.; Fernandez, J .; Griscom, L.
S.; Adam, J . L. Phys. Rev. 2001, B64, 144101.
(113) Fernandez, J .; Sanz, M.; Mendorioz, A.; Balda, R.; Chaminade,
J . P.; Ravez, J .; Lacha, L. M.; Voda, M.; Arriandiaga, M. A. J .
Alloys Compd. 2001, 323/ 324, 267.
(114) Iparraguirra, I.; Al-Saleh, M.; Balda, R.; Voda, M.; Fernandez,
J . J . Opt. Soc. Am. 2002, B19, 1.
(115) Malinovski, M.; J acquier, B.; Bouazaoui, M.; J oubert, M. F.,
Linares, C. Phys. Rev. 1990, B41, 31.
(116) Pollnau, M.; Hardman, P. J .; Kern, M. A.; Clarkson, W. A.;
Hanna, D. C. Phys. Rev. 1998, B58, 16070.
(117) Pollnau, M.; Hardman, P. J .; Clarkson, W. A.; Hanna, D. C. Opt.
Commun. 1998, 147, 203.
(118) Bla ¨tte, M.; Danielmeyer, H. G.; Verich, R. Appl. Phys. (Germany)
1973, 1, 275.
(119) Wenger, O. S.; Gamelin, D. R., Gu ¨del, H. U. Phys. Rev. 2000,
(120) Holliday, K.; Russell, D. L.; Henderson, B. J . Lumin. 1997, 72/
(121) Zhang, X; Daran, E.; Serrano, C.; Lahoz, F. J . Lumin. 2000, 87/
(122) Deren, P. J .; Strek, W.; Krupa, J . C. Chem. Phys. Lett. 1998,
(123) Mahiou, R.; Metin, J .; Cousseins, J . C. J . Lumin. 1990, 45, 363.
(124) Wermuth, M.; Riedener, T.; Gu ¨del, H. U. Phys. Rev. 1998, B57,
(125) Pouradier, J . F.; Auzel, F. J . Phys. 1976, 37, 421.
(126) Mu ¨ller, P.; Wermuth, M.; Gu ¨del, H. Chem. Phys. Lett. 1998, 290,
(127) Ryba-Romanovski, W.; Deren, P. J .; Golab, S.; Dominiak-Dzik,
G. J . Appl. Phys. 2000, 88, 6078.
(128) Ryba-Romanovski, W.; Golab, S.; Dominiak-Dzik, G.; Solarz, P.
Appl. Phys. Lett. 2001, 79, 3026.
(129) Chamarro, M. A.; Cases, R. J . Lumin. 1988, 42, 267.
(130) Auzel, F.; Hubert, S.; Meichenin, D. Appl. Phys. Lett. 1989, 54,
(131) Ronac’h, D.; Guibert, M.; Auzel, F.; Meichenin, D.; Allain, J . Y.;
Poignant, H. Electron. Lett. 1991, 27, 511.
(132) Monerie, M.; Allain, J .-Y.; Poignant, H.; Auzel, F. In Fluores-
cence, Up-conversion, and lasing in Er-doped quasi-singlemode
fluorozirconate fibres, Proceedings of ECOC’89, Gothenburg,
Sweden, Sept 1989; paper TuB12-6.
(133) Pollnau, M.; Ghisler, C.; Bunea, G.; Lu ¨thy, W., Weber, H. P. Appl.
Phys. Lett. 1995, 66, 3564.
Upconversion and Anti-Stokes ProcessesChem ical Reviews, 2004, Vol. 104, No. 1 171
(134) Golding, P. S.; J ackson, S. D.; King, T. A.; Pollnau, M. Phys.
Rev. 2000, B62, 856.
(135) Silversmith, A. J . Lumin. 1994, 60/ 61, 636.
(136) Chen, X.; Nguyen, T.; Qui, L.; DiBartolo, B. J . Lumin. 1999, 83/
(137) Pollnau, M.; Heumann, E.; Huber, G. Appl. Phys. 1992, A54,
(138) Lu ¨thi, S. R.; Pollnau, M.; Gu ¨del, H.; Hehlen, M. P. Phys. Rev.
1999, 60, 162.
(139) Hehlen, M. P.; Kra ¨mer, K.; Gu ¨del, H.; McFarlane, R. A.; Schartz,
R. N. Phys. Rev. 1994, B49, 12475.
(140) Wenger, O; Gamelin, D. R., Gu ¨del, H. U.; Butashin, A. V.;
Kaminskii, A. Phys. Rev. 1999, B60, 5312.
(141) Riedener, T.; Egger, P.; Hulliger, J .; Gu ¨del, H. Phys. Rev. 1997,
(142) Riedener, T.; Gu ¨del, H. J . Chem. Phys. 1997, 107, 2169.
(143) Pollnau, M.; Lu ¨thy, W.; Weber, H. P.; Kra ¨mer, K.; Gu ¨del, H.;
McFarlane, R. A. OSA Topics on Advanced Solid State Lasers;
Payne, A., Polock, C., Eds.; OSA: Washington, DC, 1996; Vol.
1, p 493.
(144) Hehlen, M. P.; Frei, G.; Gu ¨del, H. Phys. Rev. 1994, B50, 16264.
(145) Zhang, X.; J ouart, J . P.; Mary, G.; Liu, X; Yuan, J . J . Lumin.
1997, 72/74, 983.
(146) Spinger, B.; Danilov, V. P.; Prokhorov, A. M.; Schwan, L. O.;
Schmid, D. SPIE 2001, 4766, 191.
(147) Felix, S. F.; Gouveia, E. A.; de Araujo, M. T.; Sombra, A. S. B.;
Gouveia-Neto, A. S. J . Lumin. 2000, 87/ 89, 1020.
(148) Tkachuk, A. M.; Razumova, I. K.; Malyshev, A. V.; Gapontsev,
V. P. J . Lumin. 2001, 94/ 95, 317.
(149) Dierolf, V.; Kutsenko, A. B.; von der Hosten, W. J . Lumin. 1999,
83/ 84, 487.
(150) Nunez, L.; Herreros, B.; Duchowicz, R.; Lifante, G.; Tocho, J .
O.; Cusso, F. J . Lumin. 1994, 60/ 61, 81.
(151) Herreros, B.; Lifante, G.; Cusso, F.; Towsend, P. D.; Chandler,
P. J . J . Lumin. 1997, 72/ 74, 198.
(152) Cokcroft, N. J .; Murdoch, K. M. J . Lumin. 1994, 60/ 61, 891.
(153) Chen, X. B.; Zhang, G. Y.; Mao, Y. H.; Hou, Y. B.; Feng, Y.; Hao,
Z. J Lumin. 1996, 69, 151.
(154) Wyss, C. P.; Kehrli, M.; Huber, T.; Morris, P. J .; Lu ¨thy, W.;
Weber, H. P.; Zagumennyi, A. I.; Zavartsev, Y. D.; Studenikin,
P. A.; Shcherbakov, I. A.; Zerrouk, A. F. J . Lumin. 1999, 82,
(155) Riedener, T.; Gu ¨del, H.; Valley, G. C.; McFarlane, R. A. J . Lumin.
1995, 63, 327.
(156) Gomes, A. S. L.; de Araujo, C. B. J . Lumin. 1991, 48/ 49, 876.
(157) Wu, X.; Denis, J . P.; O ¨ zen, G.; Pelle ´, F. J . Lumin. 1994, 60/ 61,
(158) Auzel, F.; Pecile, D. J . Lumin. 1976, 11, 321. Pecile, D. De
l’influencedela matricesur l’addition dephotons par transferts
d’energie (APTE) dans les couples Yb3+-Er3+et Yb3+-Tm3+;
The `se, Universite ´P.et M.Curie, Paris, 1976.
(159) J acquier, J . Lumin. 1994, 60/ 61, 175.
(160) Wenger, O. S.; Wickleder, C.; Kra ¨mer, K.; Gu ¨del, H. J . Lumin.
2001, 94/ 95, 101.
(161) Hubert, S.; Song, C. L.; Genet, M.; Auzel, F. J . Solid StateChem.
1986, 61, 252.
(162) Auzel, F.; Hubert, S., Delamoye, P. J . Lumin. 1982, 26, 251.
(163) Deren, P. J .; Karbowiak, M.; Krupa, J . C.; Drozdzynski, J . J .
Alloys Compd. 1998, 275/ 277, 393.
(164) Stump, N. A.; Murray, G. M.; Del Cul, G. D.; Haire, R. G.;
Peterson, J . R. Radiochim. Acta 1993, 61, 129.
(165) Deren, P. J .; Krupa, J . C.; Strek, W. J . Lumin. 1997, 72/ 74,
(166) Deren, P. J .; Feries, J .; Krupa, J . C.; Strek, W. Chem. Phys. Lett.
1997, 264, 614.
(167) Deren, P. J .; Krupa, J . C.; Yin, M.; J oubert-, M. F.; Strek, W.
Spectrochem. Acta (A) 1998, A54, 2105.
(168) Deren, P. J .; J oubert, M. F.; Krupa, J . C.; Mahiou, R.; Yin, M.
J . Alloys Compd. 2002, 341, 134.
(169) Deren, P. J .; Strek, W.; Zych, E.; Drozdzynski, J . Chem. Phys.
Lett. 2000, 332, 308.
(170) Cresswell, P. J .; Robbins, D. J .; Thomson, A. J . J . Lumin. 1978,
(171) Moncorge ´, R.; Breteau, J . M.; Auzel, F. Philos. Mag. 1985, B51,
(172) Wenger, O. S.; Gu ¨del, H. U. Inorg. Chem. 2001, 40, 5747.
J acobsen, S. M.; Gu ¨del, H. U. J . Lumin. 1989, 43, 125.
(173) Heer, S.; Wermuth, M.; Kra ¨mer, K.; Ehrentraut, D.; Gu ¨del, H.
U. J . Lumin. 2001, 94/ 95, 337.
(174) Heer, S.; Wermuth, M.; Kra ¨mer, K.; Gu ¨del, H. U. Phys. Rev.
2002, 65, 125112.
(175) Heer, S.; Wermuth, M.; Kra ¨mer, K.; Gu ¨del, H. U. Chem. Phys.
Lett. 2001, 334, 293.
(176) Lim, K., S; Lee, C. W.; Kim, S. T.; Seo, H. J .; Kim, C. D. J . Lumin.
2000, 85/ 89, 1008.
(177) Wenger, O. S.; Valiente, R.; Gu ¨del, H. U. High-Press. Res. 2002,
(178) Wenger, O. S.; Gu ¨del, H. U. Inorg. Chem. 2001, 40, 157.
(179) Wenger, O. S.; Valiente, R.; Gu ¨del, H. U. Phys. Rev. 2001, B64,
(180) Wenger, O. S.; Gamelin, D. R.; Gu ¨del, H. U. J . Am. Chem. Soc.
2000, 122, 7408.
(181) Gamelin, D. R.; Gu ¨del, H. U. J . Am. Chem. Soc. 1998, 120, 12143.
(182) Gamelin, D. R.; Gu ¨del, H. U. J . Phys. Chem. 2000, B104, 10222.
(183) Sugano, S.; Tanabe, Y.; Kaminura, H. Multiplets of Transition-
Metal Ions in Crystals; Academic Press: New York, 1970; p 109.
(184) Gamelin, D. R.; Gu ¨del, H. U. Inorg. Chem. 1999, 38, 5154.
(185) Wermuth, M.; Gu ¨del, H. U. J . Phys.: Condens. Matter 2001, 13,
(186) Wermuth, M.; Gu ¨del, H. U. Chem. Phys. Lett. 1997, 281, 81.
(187) Wermuth, Gu ¨del, H. U. J . Lumin. 2000, 87, 1014.
(188) Wermuth, M.; Gu ¨del, H. U. J . Am. Chem. Soc. 1999, 121, 10102.
(189) Wermuth, M.; Gu ¨del, H. U. J . Chem. Phys. 2001, 114, 1393.
(190) Wermuth, M.; Gu ¨del, H. U. Phys. Rev. 2001, B63, 245118.
(191) Page, R. H.; Schaffers, K. I.; Waide, P. A.; Tassano, J . B.; Payne,
S. A.; Krupke, W. F.; Bischel, W. K. J . Opt. Soc. Am. 1998, B15,
(192) Mita, Y.; Yamamoto, H.; Katayanagi, K.; Shionoya, S. J . Appl.
Phys. 1995, 78, 1219.
(193) Chamaro, M. A.; Cases, R. J . Lumin. 1990, 46, 59.
(194) Yeh, D. C.; Sibley, W. A.; Suscavage, M. J . J . Appl. Phys. 1988,
(195) Kermaoui, A.; O ¨ zen, G.; Goldner, P.; Denis, J . P.; Pelle ´, F. J .
Phys. Chem. Solids 1994, 55, 677.
(196) Auzel, F. French Patent No. 1.532.609, 1968.
(197) Tokin IR Catcher; Tokin America (155 Nicholson Lane, San J ose,
CA, 95134), 1987.
(198) Photo-Turkey-1; Sumita Optical Glass Inc. (4-7-25 Harigaya,
Urawa-City, Saitama, J apan), 1994.
(199) Breteau, J . M.; Ayral, J . L.; Micheron, F.; Auzel, F. J . Appl. Phys.
1990, 67, 1102.
(200) Downing, E.; Hesselink, L.; Ralston, J .; Macfarlane, R. Science
1996, 273, 1185.
(201) Auzel F.; Pecile, D. J . Lumin. 1973, 8, 32.
(202) Bril, A.; Sommerdijk, J . L.; de J ager, A. W. J . Electrochem. Soc.
1974, 121, 660.
(203) Quimby, R. S.; Drexhage, M. G.; Suscavage, M. J . Electron. Lett.
1987, 23, 32.
(204) Malta, O. L.; Santa-Cruz, P. A.; de Sa, G. F.; Auzel, F. J . Solid
State Chem. 1987, 68, 314.
(205) Malta, O. L.; Santa-Cruz, P. A.; de Sa, G. F.; Auzel, F. J . Lumin.
1985, 33, 261.
(206) Wang, Y.; Ohwaki, J . Appl. Phys. Lett. 1993, 63, 3268.
(207) Wang, Y.; Ohwaki, J . J . Appl. Phys. 1993, 74, 1272. Ohwaki, J .;
Wang, Y. J pn. J . Appl. Phys. 1994, 33, L334.
(208) Ohwaki, J .; Wang, Y. Appl. Phys. Lett. 1994, 65, 129.
(209) Auzel, F.; Santa-Cruz, P. A.; deSa, G. F. Rev. Phys Appl. (France)
1985, 20, 273.
(210) Kurochkin, A. V.; Mailibaeva, L. M.; Manashirov, O. Y.; Sattarov,
D. K.; Smirnov, V. B. Part 1. Opt. Spectrosc. 1992, 73, 442.
Kurochkin, A. V.; Mailibaeva, L. M.; Manashirov, O. Y.; Sattarov,
D. K.; Smirnov, V. B. Part 2. Opt. Spectrosc. 1992, 73, 447.
(211) Kurochkin, A. V.; Manshisrov, O. Ya.; Sattarov, D. K.; Smirnov,
V. B.; Tsyurupa, O. V. Svetotekhnika 1992, 5, 4 (Translated by
Allerton Press Inc., 1993).
(212) Danielmeyer, H. G.; Bla ¨tte, M. Appl. Phys. (Germany) 1973, 1,
(213) Deutschbein, O.; Auzel, F. In Quantum Electronics; Grivet, P.,
Bloembergen, N., Eds.; Dunod and Columbia University Press:
Paris and New York, 1963; p 851.
(214) Bagdasarov, K. S.; Zhekov, V. I.; Lobachev, V. A. J ; Murina, M.;
Prokhorov, A. M. Sov. J . Quantum Electron. 1983, 13, 262.
(215) Van der Weg, W. F.; Van Tol, M. W. Appl. Phys. Lett. 1981, 38,
(216) de Leeuward, D. M.; Hooft, G. W.'t. J . Lumin. 1983, 28, 275.
(217) Smith, D. J . Lumin. 1981, 23, 209.
(218) J ohnson, L. F.; Guggenheim, H. J . Appl. Phys. Lett. 1971, 19,
(219) Pollack, S. A.; Chang,D. B. J . Appl. Phys. 1988, 64, 2885.
(220) Tong, F.; Risk, W. P.; Macfarlane, R. M.; Lenth, W. Electron.
Lett. 1989, 25, 1389.
(221) Lenth, W.; MacFarlane, R. M. J . Lumin. 1990, 45, 346.
(222) Hebert, T.; Wannemacher, R.; Lenth, W.; Macfarlane, R. M. Appl.
Phys. Lett. 1990, 57, 1727.
(223) Macfarlane, R. M.; Tong, F.; Silversmith, A. J .; Lenth, W. Appl.
Phys. Lett. 1988, 52, 1300.
(224) Brede, R.; Heumann, E.; Koltke, J .; Danger, T.; Huber, G. Appl.
Phys. Lett. 1993, 63, 2030.
(225) Heine, F.; Heumann, E; Danger, T.; Schweizer, T.; Huber, G.
Appl. Phys. Lett. 1994, 65, 383.
(226) Mo ¨bert, P. E.-A.; Heumann, E.; Huber, G. Opt. Lett. 1997, 22,
(227) Auzel, F. Amplifiers and Lasers with Optical Fibers. In Defects
in Insulating Materials; Kanert, O., Spaeth, J .-M., Eds.; World
Scientific: Singapore, 1993; p 43.
(228) Mears, R. J .; Reekie, L.; Poole, S. B.; Payne, D. N. Electron. Lett.
1986, 22, 159.
172 Chem ical Reviews, 2004, Vol. 104, No. 1 Auzel
(229) Allain, J .-Y.; Monerie, M.; Poignant, H. Electron. Lett. 1990, 26,
(230) Allain, J .-Y.; Monerie, M.; Poignant, H. Electron. Lett. 1990, 26,
(231) Whitley, T. J .; Millar, C. A.; Wyatt, R.; Brierley, M. C.; Szebesta,
D. Electron. Lett. 1991, 27, 1785.
(232) Grubb, S. G.; Bennett, K . W.; Cannon, R. S.; Humer, W. F.
Electron. Lett. 1992, 28, 1243.
(233) Smart, R. G.; Hanna, D. C.; Tropper, A. C.; Davey, S. T.; Carter,
S. F.; Szebesta, D. Electron. Lett. 1991, 27, 1308.
(234) Selected papers on Upconversion Lasers; Gosnell, T. R., Ed.; SPIE
Milestone Series MS 161; SPIE Optical Engineering Press:
Bellingham, WA, 2000.
(235) Komukai, T.; Yamamoto, T.; Sugawa, T.; Miyajima, Y. Electron.
Lett. 1992, 28, 830.
(236) Krasutsky, N. J . J . Appl. Phys. 1983, 54, 1261.
(237) Lenth, W.; Macfarlane, R. M. J . Lumin. 1990, 45, 346.
(238) Oetliker, U.; Riley, M. J .; May, P. S.; Gu ¨del, H. U. J . Lumin.
1992, 53, 553.
(239) Ni, H.; Rand, S. C. Opt. Lett. 1992, 17, 1222.
(240) Auzel, F.; Chen, Y. H.; Meichenin, D., ICL’93, Storrs, CN, USA,
9-12 Aug 1993. Auzel, F.; Chen, Y. H.; Meichenin, D., J . Lumin.
1994, 60/ 61, 692.
(241) Chen, Y. H.; Auzel, F. Electron. Lett. 1994, 30, 323.
(242) Auzel, F.; Chen, Y. H. J . Non-Cryst. Solids 1995, 184, 57.
(243) Chen, Y. H.; Auzel, F. J . Phys. D: Appl. Phys. 1995, 28, 207.
(244) Auzel, F.; Chen, Y. H. J . Lumin. 1995, 65, 45.
(245) Pelletier-Allard, N.; Pelletier, R. Phys. Rev. 1987, B26, 4425.
(246) J oubert, M. F.; Guy S.; J acquier, B. Phys. Rev. 1993, B48, 10031.
(247) Kueny, A. W.; Case, W. E.; Koch, M. E. J . Opt. Soc. Am. 1993,
(248) Goldner, P.; Pelle ´, F. Opt. Mater. 1995, 5, 239.
(249) Brenier, A.; Boulon, G.; Madej, C.; Pe ´drini, C.; Lou, L. J . Lumin.
1993, 54, 271.
(250) Auzel, F. Acta Phys. Pol. 1996, 90, 7.
(251) Gomes, A. S. L.; Maciel, G. S.; de Araujo, R. E.; Acioli, L. H.; de
Araujo, C. B. Opt. Commun. 1993, 103, 361.
(252) Brenier, A.; Courrol, L. C.; Pe ´drini, C.; Madej, C.; Boulon, G. J .
Lumin. 1994, 58, 285.
(253) Dyson, J . M.; J affe, S. M.; Eilers, H.; J ones, M. L.; Dennis, W.
M.; Yen, W. M. J . Lumin. 1994, 60/ 61, 668.
(254) Brenier, A.; J urdyc, A. M. J . Lumin. 1996, 69, 131.
(255) Brenier, A.; Courrol, L. C.; Pedrini, C.; Madej, C.; Boulon, G.
Opt. Mater. 1994, 3, 25.
(256) Guy, S. L’avalanche de photons; application a ` l’ion Tm3+dans
differents mate ´riaux. The `se, Universite ´ Claude-Bernard-Lyon
I, 1995. Guy, S. S.; J oubert, M. F.; J acquier, B. Phys. Rev. 1997,
(257) J oubert, M. F.; Guy, B.; Linares, C.; J acquier, B.; Adam, J . L. J .
Non-Cryst. Solids 1995, 184, 98.
(258) J ouart, J . P.; Bouffard, M.; Klein, G.; Mary, G. J . Lumin. 1994,
60/ 61, 93.
(259) Bielejec, E.; Kisel, E.; Silversmith, A. J . Lumin. 1997, 72/ 74,
(260) Liu, G. K.; Chen, Y. H.; Beitz, J . V. J . Lumin. 1999, 81, 7.
(261) Gamelin, D. R.; Wermuth, M.; Gu ¨del, H. U. J . Lumin. 1994, 83/
(262) Hubert, S.; Meichenin, D.; Zhou, B.; Auzel, F. J . Lumin. 1991,
(263) Guy, S.; J oubert, M. F.; J acquier, B. J . Lumin. 1997, 72/ 74, 65.
(264) Case, W. E.; Koch M. E.; Kueny, A. W. J . Lumin. 1990, 45, 351.
(265) Goldner, P.; Fesquet, M.; Auzel, F. J . Opt. Soc. Am. 1998, B15,
(266) Ku ¨k, S.; Diening, A.; Heumann, E.; Mix, E.; Sandrock, T.; Sebald,
K.; Huber, G. J . Alloys Compd. 2000, 300/ 301, 65.
(267) Osiak, E.; Sokolska, I; Ku ¨k, S. J . Lumin. 2001, 94/ 95, 289.
(268) Pelletier-Allard, N.; Pelletier, R. J . Lumin. 1991, 48/ 49, 867.
(269) Deren, P. J .; Krupa, J . C.; Strek, W. J . Alloys Compd. 2000, 300/
(270) Koch, M. E.; Kueny, A. W.; Case, W. E. Appl. Phys. Lett. 1990,
(271) Chen, Y. H.; Auzel, F. Electron. Lett. 1994, 30, 1602.
(272) Scheps, R. IEEE 1994, QE30, 2914.
(273) Scheps, R. IEEE 1995, QE31, 309.
(274) Sandrock, T.; Scheife, H.; Heuman, E.; Huber, G. Opt. Lett. 1997,
(275) McGonigle, A. J . S.; Girard, S.; Coutts, D. W.; Moncorge ´, R.
Electron. Lett. 1999, 35, 1640.
(276) Nicolas, S.; Descroix, E.; Guyot, Y.; J oubert, M.-F.; Abdulsabirov,
R. Yu.; Korableva, S. L.; Naumov, A. K.; and Semashko, V. V.
Opt. Mater. 2001, 16, 233.
(277) Tverjanovich, A.; Grioriev, Y. G.; Degtyarev, S. V.; Kurochkin,
A. V.; Man’shina, A. A.; Tver’yanovich, Yu. S. J . Non-Cryst.
Solids 2001, 286, 89.
(278) Hehlen, M. P.; Gu ¨del, H. U.; Shu, Q.; Rai, S.; Rand, S. C. Phys.
Rev. Lett. 1994, 73, 1103.
(279) Heber, J . Z. Phys. B: Condens. Matter 1987, 68, 115.
(280) Heber, J . J . Alloys Compd. 2000, 300/ 301, 32.
(281) Bonifacio, R.; Lugiato, L. A. In Dissipative Systems in Quatum
Optics; Bonifacio, R., Ed.; Springer-Verlag: Berlin, 1982; p 2.
(282) Auzel, F.; Hubert S.; Meichenin, D. Europhys. Lett. 1988, 7, 459.
(283) Auzel, F. Document deTravail PCM.171, Utilisation du transfert
d’energie entre ions de terres-rares pour leur application even-
tuelles aux compteurs quantiques; addition de deux et trois
photons; CNET, Issy-les -Moulineaux (France), 1967; unpub-
(284) Hehlen, M. P.; Gu ¨del, H. U.; Shu, Q.; Rand, S. C. J . Chem. Phys.
1996, 104, 1232.
(285) Gamelin, J . Chem. Phys. 2000, B104, 11045.
(286) Auzel, F. J . Lumin. 2001, 93, 129.
(287) Bednarkiewicz, A.; Strek, W. J . Phys D. Appl. Phys. 2002, 35,
(288) Zijlmans, H. J . M. A. A.; Bonnet, J .; Burton, J .; Kardos, K.; Vail,
T.; Niedbala, R. S.; Tanke, H. J . Anal. Biochem. 1999, 267, 30.
(289) Heer, S.; Lehman, O.; Haase, M.; Gu ¨del, H. U. Angew. Chem.,
Int. Ed. 2003, 42, 3179.
Upconversion and Anti-Stokes Processes Chem ical Reviews, 2004, Vol. 104, No. 1 173