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We report on the fabrication and characterization of planar waveguides in an Er-doped tungsten-tellurite glass by implantation of 3.5 MeV N+ ions. Implantations were carried out in a wide fluence range of 1 . 10(16) divided by 8 . 10(16) ions/cm(2). Waveguides were characterized by m-line spectroscopy and spectroscopic ellipsometry. Irradiation-induced refractive index modulation saturated around a fluence of 8 . 10(16) ions/cm(2). Waveguides operating at 1550 nm were obtained in that material using 3.5 MeV N+ ion implantation.
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MeV Energy N+-Implanted Planar Optical
Waveguides in Er-Doped Tungsten-Tellurite
Glass Operating at 1.55 µm
Volume 4, Number 3, June 2012
I. Bányász
S. Berneschi
M. Bettinelli
M. Brenci
M. Fried
N. Q. Khanh
T. Lohner
G. Nunzi Conti
S. Pelli
P. Petrik
G. C. Righini
A. Speghini
A. Watterich
Z. Zolnai
DOI: 10.1109/JPHOT.2012.2194997
1943-0655/$31.00 ©2012 IEEE
MeV Energy Nþ-Implanted Planar Optical
Waveguides in Er-Doped Tungsten-Tellurite
Glass Operating at 1.55 m
I. Ba´nya´sz,1S. Berneschi, 2;3M. Bettinelli, 4M. Brenci,3M. Fried, 5
N. Q. Khanh,5T. Lohner, 5G. Nunzi Conti, 3S. Pelli,3P. Petrik, 5
G. C. Righini,2;3A. Speghini, 4A. Watterich, 1and Z. Zolnai5
1Department of Crystal Physics, Wigner Research Centre for Physics,
Hungarian Academy of Sciences, 1525 Budapest, Hungary
2Museo Storico della Fisica e Centro di Studi e Ricerche BEnrico Fermi,[
00184 Roma, Italy
3MDF-Lab, BNello Carrara[Institute of Applied Physics, IFAC-CNR,
50019 Sesto Fiorentino (FI), Italy
4Laboratory of Solid State Chemistry, Department of Biotechnology, University of Verona, and INSTM,
University of Verona, 37134 Verona, Italy
5Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences,
1525 Budapest, Hungary
DOI: 10.1109/JPHOT.2012.2194997
1943-0655/$31.00 Ó2012 IEEE
Manuscript received March 12, 2012; revised April 3, 2012; accepted April 5, 2012. Date of publication
April17, 2012; date of current version May 4,2012. This work was supported by Hungarian NationalResearch
Fund (OTKA-NKTH and OTKA) underprojectsK 68688 and K 101223, as well as fromthe bilateral 2010-2012
CNR/MTA project. Corresponding author: I. Ba´nya´ sz (e-mail: banyasz@sunserv.kfki.hu).
Abstract: We report on the fabrication and characterization of planar waveguides in an
Er-doped tungsten-tellurite glass by implantation of 3.5 MeV Nþions. Implantations were
carried out in a wide fluence range of 1 1016 81016 ions/cm2. Waveguides were
characterized by m-line spectroscopy and spectroscopic ellipsometry. Irradiation-induced
refractive index modulation saturated around a fluence of 8 1016 ions/cm2. Waveguides
operating at 1550 nm were obtained in that material using 3.5 MeV Nþion implantation.
Index Terms: Integrated optics, planar waveguide, ellipsometry, m-line spectroscopy.
1. Introduction
Ion beam techniques are among the best methods for optical waveguide fabrication in crystalline
and amorphous materials. The first report on waveguide fabrication in fused silica using proton
beam was published by Schineller et al. in 1968 [1]. An important monograph of this field was
written by Townsend et al. [2]. A detailed review of ion-implanted waveguides in optical materials
has recently been published by Chen et al. [3].
Tellurite glasses have gained a widespread attention because of their potential as hosts of rare-
earth elements for the development of fiber and integrated optic amplifiers and lasers covering all
main telecommunication bands [4]–[6]. Er3þ-doped tellurite glasses in particular are very attractive
materials for the fabrication of broadband amplifiers in wavelength division multiplexing (WDM)
around 1.55 m, as they exhibit large stimulated cross sections and broad emission bandwidth.
Furthermore, tellurite glasses have low process temperature and nonlinear properties. Fabrication
and optical properties of bulk and planar waveguides obtained in such materials have been
extensively studied [7]–[9]. Only a few papers over the past few years reported on the possibility to
fabricate channel waveguides in these activated glassy materials by means of femtosecond laser
Vol. 4, No. 3, June 2012 Page 721
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writing [10] and reactive ion etching (RIE) process in pure TeO2thin films [11], [12]. In spite of the
relevant advancements in performance achieved by these approaches, still significant problems
persist toward the full exploitation of this material. In fact, RIE still lacks the necessary quality output
to allow the fabrication of waveguides fully embedded in the glass, which would enable more
flexibility in the optimization of the waveguides and of the pumping schemes. On the other hand,
laser writing does not induce high index contrast between waveguide and substrate, which would
permit a better field confinement and, consequently, a more efficient performance of the device.
Research interest in the field of Er3þ-doped tellurite materials is still going on, with the aim of
discovering the best combination of tellurite glass formulation and fabrication process in order to
reduce the cost and increase the performance of the devices so obtained. In this context, ion
implantation presents some unique advantages compared with other fabrication methods. It proved
to be a universal technique for producing waveguides in many optical materials and has good
controllability and reproducibility [3].
We have recently reported fabrication of channel waveguides in an Er-doped tungsten-tellurite
(Er:Te) glass via implantation of MeV Nþions [13]. Based on our experiences with the 2-D
waveguide structures, we carried out a systematic study of the implantation parameters for planar
waveguides, in order to better understand the nature of the guiding structure and realize waveguide
operation in the 1550-nm telecommunication band. We increased the ion energy from the 1.5-MeV
value used in those experiments to 3.5 MeV to achieve this goal by obtaining a broader guiding
layer. Nþions implantation has already been long demonstrated as a means to fabricate low loss
waveguides in other materials, hence our choice for the tests described in this paper [14], [15].
Moreover, we decided to use Nþions for the fabrication of the waveguides because of two reasons:
on the one hand ion mass in the accelerator was limited by ion mass energy selector magnet. On
the other hand, the higher the atomic mass the bigger the ion-solid interaction. If compared with He
ions, in the case of N, we expected three times bigger electronic stopping and more than ten times
bigger nuclear stopping in the MeV energy range. In fact, we succeeded in achieving the same
refractive index modulation in a Pyrex glass with Nþions of a dose of one order of magnitude lower
than with Heþions of the same energy [16].
2. Waveguide Fabrication
The composition of the glass developed for our experiments was 60 TeO2-25 WO3- 15 Na2O-0:5 Er2O3
(mol. %) with a density of 5.75 g/cm3. We fabricated planar waveguides in the Er:Te glass samples via
implantation of Nþions with 3.5-MeV energies. Irradiations were carried out with a collimated beam from a
Van de Graaff accelerator at the Research Institute for Particle and Nuclear Physics, Budapest, Hungary,
with normal incidence on the glass samples. Lateral homogeneity of the irradiation was assured by
defocusing the ion beam with a magnetic quadrupole and by scanning the sample under a 2 mm 2 mm
beam. Useful size of the implanted waveguides was 6 mm 6 mm. Irradiation was carried out at fluences
of 1, 2, 4, and 8 1016 ions/cm2.
3. SRIM Simulations and Ellipsometric Measurements
Structure of the ion implanted planar waveguides is determined mainly by the energy and fluence of
the implanted ions. Distribution of the implanted ions or that of the collision events along the depth
of the implanted sample can serve as a rough estimation of the refractive index profile of the
implanted waveguide. We used SRIM 2008 code (Stopping and Range of Ions in Matter) [17] to
simulate the fabrication of the waveguides. Full-cascade SRIM simulations were performed to
estimate the ion and damage depth distributions in the target. Maximum of the distribution of the
implanted Nþions was 2.5 m below the surface of the Er:Te glass sample in case of 3.5-MeV ion
energy, with a longitudinal straggling of 0.5 m. Maximum of the collision events (vacancy
production) distribution roughly coincides with that of the ion distribution, but it extends considerably
toward sample surface.
The ion-implanted waveguides were measured with a WOOLLAM M-2000DI spectroscopic
ellipsometer ð¼193ÿ1690 nmÞ. A three-layer optical model was applied in the evaluation of the
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spectroscopic ellipsometry (SE) data. The first layer, which is adjacent to the substrate, represents
the stopping region. The second layer is the region that the implanted ions traverse before they stop.
The third layer is a surface roughness film taken into account on basis of effective medium
approximation [18]. Dielectric functions of the first and second layers were described by the Cauchy
dispersion relation. Parameters of the Cauchy dispersion relations and layer thicknesses were
considered as free parameters. We applied the evaluation software WVASE32 created by J. A.
Woolam, Inc. [19] for the analysis of the spectroellipsometric data. The evaluation yielded 7.9
0.1 nm for the thickness of the surface roughness layer and 2.019 0.001 for the refractive
index of the nonimplanted glass substrate at ¼635 nm.
A graphical comparison of implanted Nþdistribution obtained by SRIM and barrier layer bound-
aries obtained by SE is shown in Fig. 1. Center of the barrier layer is slightly beyond the projected
range, while its width increases with the implanted fluence, as expected.
4. M-line Spectroscopic Measurements
For the characterization of the planar waveguides implanted in the tungsten-tellurite glass, we used
a semiautomatic m-line spectroscopic instrument (BCOMPASSO[), which was developed at IFAC.
Accuracy of the instrument is generally 110ÿ4and 410ÿ4on the effective refractive index and
bulk refractive index, respectively. In the case of the Nþ-implanted planar waveguides in the Er:Te
glass, due to the lower contrast in the measurement, the accuracy was lower: about 510ÿ4and
110ÿ3, respectively.
Due to the high refractive index of the bulk glass (around 2.0 at 635 nm), we used a rutile prism to
couple the light in the irradiated regions. Table 1 summarizes the values obtained from the m-line
measurements performed at 635 and 1550 nm. Each value is an average of three measurements.
Bulk refractive index was 2:041 110ÿ3. We observed modes with effective refractive index
below the corresponding value of the bulk refractive index, a clear indication of leaky modes.
Fabrication of the Er:Te glass waveguides with 3.5-MeV energy Nþions resulted in waveguides
able to support modes also at 1550 nm wavelength. We present here two examples of the results
obtained. The m-line spectrum (reflected relative intensity versus effective refractive index) with five
TE modes for the highest implanted fluence, 8 1016 ions/cm2, measured at 635 nm, is presented in
Fig. 2(a). Proof that the same waveguide supports modes at 1550 nm is shown in Fig. 2(b).
To analyze how the implantation parameters influence the characteristics of the waveguides, we
have carried out numerical fits based on the m-lines measurements. The model upon which the
numerical fit was based was rather simple but effective: The waveguide has been considered a
Fig. 1. SRIM simulation and SE fit of the waveguide structure.
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three layer step structure and the leaky nature of the waveguide has been neglected, using the
barrier layer as the substrate of the waveguide. Indeed, to justify the latter assumption it must be
stressed that, though propagation losses are obviously strongly influenced by how well the mode is
confined by the leaky structure or, in other terms, how well the leaky structure resembles a truly
confined mode, values of the effective indices are much less dependent from this factor, and the
approximation can be applied to the numerical fit used to assess only the physical characteristics of
the structure.
The availability of data at several wavelengths (635, 980, 1310, and 1550 nm) has allowed us to
obtain a more accurate and flexible data processing. Actually, assuming a Sellmeier-like law to
account for chromatic dispersion for all layers:
n2¼1þ2
A2þB(1)
Fig. 2. M-line spectra of waveguide. Fluence ¼81016 ions/cm2, E ¼3:5 MeV. (a) At 635 nm and (b) at
1550 nm.
TABLE 1
Effective refractive indices (average values) versus ion fluence measured at 635 and 1550 nm for Er:Te
glass. Error of the refractive indices is 510ÿ4
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and using it in the fit process, it was possible to obtain the thickness of the guiding layer and the
parameters A and B for the guiding and the barrier layers in a broad wavelength range.
As shown in Fig. 3 for the sample irradiated with 8 1016 ions/cm2, the fit process allowed us to
model through the A and B parameters the wavelength dependent refractive index of both the
guiding (nf) and barrier layers (ns) by means of the A and B parameters and (1). Moreover, the
effective indices of the modes were calculated with the values of the numerical regression results
and the same assumptions used in the fit process. The agreement between the experimental data
(dots in Fig. 3) and the calculated effective indices is very good. Thickness of the guiding layer was
assessed to be 2.2 m, in agreement with SRIM simulations [17].
Fig. 4 shows how the difference of the refractive indices of the guiding and barrier layers is
affected by the fluence, as obtained by the same fit procedure at 635 nm. The guiding layer index
shows a slight increase with higher fluences, whereas the barrier layer exhibits a saturating larger
decrease; combination of both effects produces the guiding properties of the structure.
Fig. 3. Reconstruction of the refractive index of the guiding and barrier layers as a function of the
wavelength. Sample irradiated with 8 1016 ions/cm2Calculated effective indices of the modes are also
shown.
Fig. 4. Refractive index difference of the guiding and barrier layers versus fluence at 635 nm.
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5. Discussion and Conclusion
In conclusion, planar waveguides were fabricated by irradiation with 3.5 MeV Nþions in a rare-
earth-doped tellurite glass. Fluences of the implanted ions ranged from 1 1016 to 8 1016 ions/cm2.
The experimental results and modeling reported here demonstrate the optical barrier nature of the
waveguide due to the nuclear interactions among the bombarding and target ions. Therefore, light is
confined in the layer comprised between the end of range or optical barrier (of lower refractive
index) and the surface of the glass. Nevertheless, with an increase of the ion fluence, we observed
an increase of effective indices of the leaky modes toward the bulk refractive index value. This
seems to partially justify the assumption, formulated in a previous work [13], for which some
ionization phenomenon along the path of the nitrogen ions induces a positive refractive index
change ðn90Þlocally in the region between the surface of the glass and the end of range. All
samples supported guided modes from 635 nm to 1550 nm. Saturation of the refractive index
change occurred in the 5 1016 1017 ions/cm2range of the implanted fluence. The fact that these
waveguides supported propagation also in the 1.55 m band envisages their application in the
telecom field to the fabrication of integrated optical amplifiers capable of exploiting the good
spectroscopic properties offered by using tellurite glasses as hosts for the rare earth dopants.
Refractive indices of the barrier and guiding layers and the thickness of the guiding layer have
also been characterized using the effective indices of the waveguide modes. These measurements
have evidenced that the waveguides obtained by ion implantation exhibit a large refractive index
contrast ðn0:09Þ, which will enable the fabrication of waveguides with small field size, provided
the barrier formation process is optimized.
Agreement with the experimental data and thickness assessment by SRIM modeling and
ellipsometric measurements was good. Next steps will include the fabrication of channel waveguides
with optimized irradiation and structural parameters based on the results of the characterization
described in this paper.
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... In some cases, an optical burrier structure is generated by the nuclear interaction among the incoming ions and those originally present in the bulk material. Light can be confined in the layer comprised between the " end of range " where the optical barrier is located (the zone at lower refractive index) and the surface of the specimen181920. Light propagation inside these structures occurs by means of leaky – modes. In other case, the waveguide has a typical " well " + " barrier " pattern distribution, characterized by a positive refractive index change in the near surface regions and a negative refractive index change in correspondence of the stopping regions at the end of the ions track. ...
... wavelengths, typically around 1.55 µm (in the C band of the telecommunication systems) where the erbium ions present their emission peak, making possible the optical amplification signal. In fact, we have previously demonstrated that Er 3+ : TeO 2 − WO 3 slab waveguides, implanted with N + ions at 3.5 MeV, supported single mode at 1.55 µm depending on the ion fluence [18,25].Figure 3 shows an interference microscopic microphotograph of a channel waveguide fabricated at N + energy of 3.5 MeV and 1 × 10 16 ions/cm 2 ion fluence, following the sketch reported in the previousFigure 1A. A green interference filter, centred at a wavelength of 551 nm, was used in the microscope. ...
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... In this work, we used the swift heavy ion irradiation , an efficient technique for modification of the refractive index of materials, to produce planar waveguides in Er 3+ :MgO:SLN crystal. This technique has been emerged to be a modifying mechanism with lower irradiation fluence and faster fabrication procedure , compared with the traditional ion implantation [21,242526272829303132. As to this technique, the planar waveguide region was generated with modification of the refractive index during the incident ions deposition in which the electronic stopping power (S e ) of the ions and the nuclear stopping power (S n ) of the ions play important roles in transferring the energy from the incident beams to the target material [31]. ...
... In terms of the application of ion implantation for 2D wave guide formation we note that the use of photoresist to define the guiding structure is impractical, because the ion irradiated photoresist layer is difficult to remove from the sample surface. Our results on the optimization of waveguide formation in an Er-doped tungsten–tellurite oxide glass via irradiation with 3.5 MeV N + ions were reported recently [12] Contents lists available at SciVerse ScienceDirect ...
... Both spectroscopic ellipsometric and m-line spectroscopic results suggest that planar waveguides irradiated in the sillenite type BGO crystal have a complicated refractive index profile as a result of the crystal damage and the presence of the implanted N + ions. Because of the low number of modes, instead of the common methods, a multispectral method [12] will be used to calculate the refractive index profiles of those waveguides. ...
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... Tellurite glasses are of great signicance in the eld of optics owing to their distinctive properties which marks them as outstanding materials for applications in third order harmonic generation, optical waveguides, and Raman ampliers. [1][2][3][4][5] TeO 2 forms glass only at a high melt cooling rate ($10 5 K s À1 ) by roller quenching 6 or by intermittent cooling techniques, 7 however, its glass forming ability (GFA) enhances considerably upon the addition of modier oxides such as alkali, alkalineearth and heavy metal oxides. [6][7][8][9] The basic structural units of the tellurite glasses are trigonal bipyramidal (TeO 4 ) and trigonal pyramidal (TeO 3 ) units. ...
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Keywords: Tellurite glasses Short-range structure Neutron and high energy X-ray diffraction RMC simulations XANES A B S T R A C T The structure of WO 3-TeO 2 glasses containing 15, 20 and 25 mol% WO 3 are studied by neutron diffraction (ND), high energy X-ray diffraction (XRD) and X-ray Absorption Near Edge spectroscopy (XANES). The short-range structural properties of glasses i.e. TeeO and WeO speciation, coordination number distributions, bond-lengths, and the OeTeeO, OeWeO and OeOeO bond angle distributions in the glass network are determined by the Reverse Monte Carlo (RMC) simulations of the ND and XRD data. RMC technique successfully determined all partial pair correlation functions and the coordination number distributions revealed that glass network consists predominantly of TeO 4 and WO 4 units with small amounts of triangular, penta and hexa coordinated units. The average WeO and TeeO bond lengths are in the ranges: 1.69-1.75 ± 0.01 Å and 1.99-2.00 ± 0.01 Å respectively. Both WeO and TeeO correlation peaks are asymmetrical, that indicate a distribution of their bond lengths in the respective structural units. The O-Te-O bond angle distribution has a peak at 107 ± 2°. Similarly the O-W-O bond angle distribution has a peak at 108 ± 5°. On increasing the WO 3 concentration from 15 to 25 mol%, the average TeeO coordination number decreases from 3.80 to 3.61 ± 0.02 due to the structural transformation: TeO 4 → TeO 3 , similarly the WeO coordination also decreases and is in the range: 3.79-3.67 ± 0.02. XANES studies found that the oxidation state of Te and W ions in the glasses are 4 + and 6 + respectively.
... Researchers have focused their attention towards the oxide glasses due to their wide-ranging properties in combination with their wide composition range of formation, which renders them good candidates for many practical applications such as the dielectrics for super-capacitors [3], electrolytes in the electrochemical devices [4] and as sealants for high temperature oxide fuel cells [5,6]. Tellurium dioxide based glasses are outstanding materials for non-linear optical devices, up-conversion lasers and optical waveguides [7][8][9][10][11]. Some of the remarkable features of tellurite glasses are high refractive index, low phonon energies, high transparency in the infrared region and very high third order non-linear optical coefficients [12][13][14]. ...
Article
Glass and anti-glass samples of Bi2O3-TeO2 and Bi2O3-Nb2O5-TeO2 were prepared by ice-water quenching and normal-quenching respectively. The bismuth tellurite system has poor glass forming ability (GFA) and forms a glassy phase at low Bi2O3 concentration of 2 to 5-mol%. On increasing Bi2O3 concentration to 10 mol%, a mixture of glass and anti-glass phases are formed by rapid quenching of the melt. A further increase in Bi2O3 concentration to 20 mol%, produces a sample consisting of entirely Bi2Te4O11 anti-glass upon melt-quenching. An anti-glass is a solid, which has long range order of cations (Te⁴⁺, Bi³⁺, Nb⁵⁺ etc.) but these are statistically distributed at their sites while the anion sites are partially vacant. Consequently the X-ray diffraction (XRD) patterns of bismuth tellurite and bismuth niobium tellurite anti-glass samples show sharp XRD peaks but the Raman spectra show broad phonon bands due to disturbed short-range order of the anions. The addition of Nb2O5 to the Bi2O3-TeO2 system significantly enhances the GFA. Samples from the system: xBi2O3-xNb2O5-(100-2x)TeO2 grow micro-inclusions or spherulites of size of several micron within the glass matrix on slow melt-cooling. Heat treatment of 7.5Bi2O3-7.5Nb2O5-85TeO2 sample show structural transitions from glass → anti-glass → crystalline phases.
... Alternative fabrication processes have been proposed and implemented, such as UV beam and femtosecond pulsed laser writing89101112. Ion beam irradiation is also a promising technique for waveguide fabrication in rare-earth doped glasses [13] and crystals [14]. The majority of the authors reporting fabrication of channel waveguides via ion beam irradiation used either proton151617 or helium [18] beams. ...
... Fabrication of multimode channel waveguides in an Er 3+ -doped tungsten–sodium–tellurite glass MeV energy nitrogen ion irradiation has recently been dem- onstrated [11]. Our results on the optimization of waveguide formation in an Er-doped tungsten–tellurite oxide glass via irradiation with 3.5 MeV N + ions were reported recently [12]. However, the greatest part of the observed guiding modes in those ion-implanted waveguides proved to be leaky. ...
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Ion implantation proved to be an universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er3+-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55 μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Calcium fluoride is an excellent optical material, due to its perfect optical characteristics from UV wavelengths up to near IR. It has become a promising laser host material (doped with rare earth elements). Ion implantation was also applied to optical waveguide fabrication in CaF2 and other halide crystals. In the present work first single-energy implantations at 3.5 MeV at various fluences were applied. Waveguide operation up to 1.5 μm was observed in Er:Te glass, and up to 980 nm in CaF2. Then double-energy implantations at a fixed upper energy of 3.5 MeV and lower energies between 2.5 and 3.2 MeV were performed to suppress leaky modes by increasing barrier width.
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Short-range structural properties of glasses of the system: xMoO 3 -(100-x)TeO 2 (x = 20, 30, 40 and 50 mol%) were studied by neutron diffraction. The diffraction data was modeled by Reverse Monte Carlo (RMC) simulations and the partial pair correlation distributions, Te-O, Mo-O, O-O bond-lengths/distances, Te and Mo speciation and the bond angle distributions were determined. It was found that TeO 3 , TeO 4 and TeO 5 are the major structural units and Mo ions exist in triangular, tetra, penta and hexa-units with the dominant fraction being that of MoO 4 and MoO 5 units in the glass network. Both the Te-O and Mo-O atomic pair distributions show peaks at same distances in the range: 1.970.02 to 2.000.03 and the Mo-O and Te-O structural units are found to have very similar dimensions and geometry. The O-Te-O and O-Mo-O bond angle distributions have peaks at 88.2°, which confirm that O eq -Te-O ax are the most abundant Te-O linkages in the glass network. The glasses do not show any systematic variation in the average Te-O and Mo-O co-ordinations on increasing MoO 3 concentration from 20 to 50 mol%, due to the dual character of MoO 3 as a network modifier and former.
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In this paper the authors describe the fabrication and characterisation of slab optical waveguides in eulytine BGO crystal obtained by N+ high energy ion implantation. Utilising heavier ions for the implantation process has been proved to produce the same refractive index change at smaller doses than when light ions such as He+ are used and therefore intended to assess the effects of N+ ions implantation in order to demonstrate the feasibility of this process and optimise it with the future aim of developing waveguide based optical devices.
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The fabrication of multimode channel waveguides in Er3+ -doped tungsten-tellurite glass is demonstrated, for the first time, using an high energy ion beam irradiation technique. Nitrogen ions with dose of 1.0 x 1016 ions/cm2 and 1.5 MeV energy were used for this aim. The waveguiding effect was investigated using the end-fire coupling technique. The propagation depth so measured shown to be wider than that simulated using SRIM. A possible explanation may be attributed to the additional ionization processes occurred under the unmasked region during the irradiation. A precise measurement of the refractive index change is still under investigation.
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This book is the first to give a detailed description of the factors and processes that govern the optical properties of ion implanted materials, as well as an overview of the variety of devices that can be produced in this way. Beginning with an overview of the basic physics and practical methods involved in ion implantation, the topics of optical absorption and luminescence are then discussed. A chapter on waveguide analysis then provides the background for a description of particular optical devices, such as waveguide lasers, mirrors, and novel nonlinear materials. The book concludes with a survey of the exciting range of potential applications.
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Second harmonic generation has been examined for 30ZnO⋅70TeO2 glass with a two-step poling procedure in order to understand the poling temperature dependence of second harmonic intensity. When the poling temperature increases, the second harmonic intensity increases, manifests a maximum at the temperature which we call an optimum poling temperature, and decreases drastically just below the glass transition temperature. The glass treated with two-step poling, which includes poling at 300 °C and subsequent poling at the optimum poling temperature, i.e., 280 °C, exhibits much smaller second harmonic intensity and more unambiguous Maker fringe pattern than that poled only at 280 °C. This fact suggests that the decrease in second harmonic intensity with an increase in poling temperature cannot be attributed to a reversible process like a thermal fluctuation of dipoles, but is governed by an irreversible one. Based on a linear relation between the optimum poling temperature and glass transition temperature, the irreversible process is deduced to consist of some oxidation reactions such as a migration of nonbridging oxide ions to and subsequent evaporation of oxygen gas at the anode side. Decay of the second harmonic intensity for 30NaO1/2⋅70TeO2 glass as well as 30ZnO⋅70TeO2 glass has also been examined at room temperature. Whereas the 30ZnO⋅70TeO2 glass does not show a decay, the second harmonic intensity of the 30NaO1/2⋅70TeO2 glass decays rapidly with an average relaxation time of 10 h. This relaxation behavior is explainable in terms of the difference in mobility between Zn2+ and Na+ ions. © 1999 American Institute of Physics.
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A technique for fabricating low‐loss (on the order of 0.1 dB/cm) integrated optical waveguides in amorphous SiO 2 ‐based material by nitrogen ion implantation is reported. By comparing the results of nitrogen implantation and oxygen implantation in SiO 2 , the mechanism of waveguide formation in the nitrogen‐implanted waveguides is shown to be chemical doping effect of the nitrogen dissolved in amorphous SiO 2 .
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Optical waveguides may be formed in silica by an increase in refractive index resulting from a compaction of the glass network caused during radiation damage. An additional index enhancement had been ascribed to chemical changes during nitrogen implantation. The present work confirms this higher level of index enhancement of up to 4%. Measurements of the refractive index profile before and after annealing suggest that whereas electronically generated damage is annealed by 450°C, the changes in the region of the implanted nitrogen are stable. In the region of maximum nitrogen concentration the presence of a glass phase resembling silicon oxynitride is proposed. However a comparison of the refractive index profile with computer simulations of impurity and defect profiles suggests that radiation damage induced by nuclear collisions contributes to the refractive index profile even in the annealed samples.
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Tellurite glasses were generally applied in rare earth optical materials due to their excellent physical and chemical properties. In this study, novel tellurite glasses composed of TeO2-TiO2-La2O3 were prepared by conventional melting-quenching method. Some basic physical parameters such as density, refractive indices, transition temperature and crystalline temperature were measured. The structure was analyzed by Raman spectra. The absorption, upconversion and fluorescence spectra were measured by UV-Vis-NIR spectrophotometer and spectrofluorimeter. Under 980 nm laser excitation, upconversion luminescence centered at 531, 545 and 657 nm corresponding to the transition 4H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 respectively, were observed. The effects of TiO2 concentration on structure and upconversion luminescence intensity were discussed. The result indicated that the upconversion intensity increased as the phonon concentration decreased. The fluorescence properties of Er3+ doped glass were also studied. The dominant peak centered at 1531 nm and full width at half maximum (FWHM) was 64 nm. The Er3+ stimulated emission cross-section was calculated on the basis of McCumber theory. The possible mechanism of upconvesion and fluorescence were proposed.
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As one of most efficient techniques for material-property modification, ion implantation has shown its unique ability for alteration of surface refractive index of a large number of optical materials, forming waveguide structures. The induced refractive index changes are materials related, and closely dependent on the species, energies and doses of the implanted ions. This paper reviews the results of recent research on the fabrication, investigation and applications of the ion-implanted optical waveguides in various optical materials, including crystals and non-crystalline glasses. As will be summarized, ion implantation offers a nearly universal solution for the waveguide fabrication in most existing optical materials to date, which opens up new possibilities of attractive optical applications.
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In this paper we discuss the connection between the microstructure of a heterogeneous thin film and its macroscopic dielectric response ε. Effective medium theory is developed from a solution of the Clausius-Mossotti problem from basic principles. The solution is generalized to obtain the Lorentz-Lorenz. Maxwell Garnett and Bruggeman expressions. The connection between microstructure and absolute limits to the allowed values of the dielectric response of two-phase composites is reviewed. The form of these limits for two-phase composites of known composition and two- or three-dimensional isotropy can be used to derive simple expressions for ε and also for the average fields within each phase. These results are used to analyze dielectric function spectra of semiconductor films for information about density, polycrystallinity and surface roughness. Examples illustrating the detection of unwanted overlayers and the real-time determination of nucleation growth are also given.
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Tungsten tellurite glasses doped with Er3+, Tm3+, Pr3+, and Ho3+ ions were prepared by melt quenching. The glass matrix was the same for all types of glasses and had a high sodium content in order to allow the fabrication of waveguides using an ion-exchange technique. The absorption spectra of the glasses were measured and the Judd–Ofelt parameters Ωq were obtained from the experimental oscillator strengths of the f → f transitions. Er3+ doped glasses showed a very high quantum efficiency when comparing the calculated radiative decay time with the measured lifetime of the 4I13/2 metastable level. Ag+ ↔ Na+ ion-exchanged planar waveguides were successfully obtained in all types of glasses and characterized by the prism coupling technique. It turned out that the diffusion constant values are very similar for glasses containing different rare-earth ions with the same concentration, while, at least for the Er3+ doped ones, the diffusion constant changes with the ions concentration.