-
F. Capasso,
R. Paiella,
R. Martini,
R. Colombelli,
C. Gmachl,
T.L. Myers,
M.S. Taubman,
R.M. Williams, C.G. Bethea,
K. Unterrainer,
H.Y. Hwang,
D.L. Sivco,
A.Y. Cho,
A.M. Sergent,
H.C. Liu,
E.A. Whittaker
[show abstract]
[hide abstract]
ABSTRACT: Following an introduction to the history of the invention of the
quantum cascade (QC) laser and of the band-structure engineering
advances that have led to laser action over most of the mid-infrared
(IR) and part of the far-IR spectrum, the paper provides a comprehensive
review of recent developments that will likely enable important advances
in areas such as optical communications, ultrahigh resolution
spectroscopy and applications to ultrahigh sensitivity gas-sensing
systems. We discuss the experimental observation of the remarkably
different frequency response of QC lasers compared to diode lasers,
i.e., the absence of relaxation oscillations, their high-speed digital
modulation, and results on mid-IR optical wireless communication links,
which demonstrate the possibility of reliably transmitting complex
multimedia data streams. Ultrashort pulse generation by gain switching
and active and passive modelocking is subsequently discussed. Recent
data on the linewidth of free-running QC lasers (~150 kHz) and their
frequency stabilization down to 10 kHz are presented. Experiments on the
relative frequency stability (~5 Hz) of two QC lasers locked to optical
cavities are discussed. Finally, developments in metallic waveguides
with surface plasmon modes, which have enabled extension of the
operating wavelength to the far IR are reported
IEEE Journal of Quantum Electronics 07/2002; · 1.88 Impact Factor
-
R. Martini,
C. Gmachl,
J. Falciglia,
F.G. Curti, C.G. Bethea,
F. Capasso,
E.A. Whittaker,
R. Paiella,
A. Tredicucci,
A.L. Hutchinson,
D.L. Sivco,
A.Y. Cho
[show abstract]
[hide abstract]
ABSTRACT: The high-speed direct modulation response of mid-infrared quantum
cascade (QC) lasers is investigated up to a frequency of 2 GHz, showing
high-frequency data transmission capabilities. The application of QC
lasers to optical wireless communications is discussed and demonstrated
in a free-space television link over a distance of 70 m
Electronics Letters 03/2001; · 0.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Semiconductor lasers and detectors based on intersubband electron transitions are used to generate and measure high-speed pulses of mid-infrared radiation. In particular, we use a commercial comb generator to gain-switch a state-of-the-art 8-/spl mu/m quantum cascade laser mounted in a high-speed package. The output pulses of this device are then detected with a small-area quantum-well infrared photodetector, also packaged for high-speed operation. Pulse widths shorter than 90 ps are directly measured with this system. Accounting for the finite response time of the detection electronics, a deconvolved duration of approximately 45 ps is extrapolated.
IEEE Photonics Technology Letters 08/2000; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We demonstrated gain-switching of several 5 and 8-μm quantum
cascade lasers. In particular, these devices were driven with fast (- 90
psec) electrical pulses produced by a commercial step-recovery diode
(comb generator). The corresponding optical pulses were directly
measured with a high-speed quantum-well infrared photodetector (QWIP), a
photoconductive detector also based on intersubband transitions in
semiconductor quantum wells
Lasers and Electro-Optics Society 2000 Annual Meeting. LEOS 2000. 13th Annual Meeting. IEEE; 02/2000
-
[show abstract]
[hide abstract]
ABSTRACT: We develop a gain-switched quantum cascade (QC) laser to generate pulses with less than 200 ps duration at 8 μm gain switching is a simple technique for the generation of picosecond light pulses from injection lasers, which relies on the rapid depletion of the gain-medium population inversion following a short-lived electrical excitation
Lasers and Electro-Optics Society 1999 12th Annual Meeting. LEOS '99. IEEE; 02/1999
-
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate high-speed optical packet switching using a fast
broadband-tunable laser. The optical packets are modulated at 2.5 Gb/s
and may be switched among 4 wavelength channels in less than 1 bit
period, thereby requiring no significant guardband. The data packets are
transmitted through 200 km of non-DSF and yield open eye diagrams
Integrated Optics and Optical Fibre Communications, 11th International Conference on, and 23rd European Conference on Optical Communications (Conf. Publ. No.: 448); 10/1997
-
W. Fang,
T. Tanbun-Ek, C.G. Bethea,
P. Wisk,
P.J. Sciortino,
A.M. Sergent,
S.N.G. Chu,
R. Pawelek,
R. People,
G. Nykolak,
Y.K. Chen,
W.T. Tsang
Lasers and Electro-Optics, 1997. CLEO '97., Summaries of Papers Presented at the Conference on; 06/1997
-
[show abstract]
[hide abstract]
ABSTRACT: A consistent method to characterize the temperature dependence of bulk InGaAsP semiconductor laser diodes is presented. Independent measurements of the gain and spontaneous emission spectra are conducted, and the spectra are calibrated using their fundamental relationship. This procedure will provide a unique approach to extract precise values for laser diode parameters such as quasi-Fermi level separation, peak modal gain, and total loss. The radiative and nonradiative current densities can then be calculated as a function of temperature and injection current. By comparing the measured data with a theoretical model, the carrier density is calculated. Important phenomena contributing to the strong temperature dependence of long-wavelength bulk InGaAsP/InP lasers are highlighted. © 1997 American Institute of Physics.
Applied Physics Letters 02/1997; 70(7):796-798. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The first monolithically integrated DFB laser/Mach-Zehnder interferometric modulator fabricated by the selective area low pressure MOVPE growth technique is reported. A near 3-dB power divider at the Y-branches of the interferometer has been reproducibly achieved by a photolithographically defined dielectric mask used in the selective area growth technology and confirmed by an infrared near field imaging technique. A modulation depth of over 12 dB was achieved both in the forward and reverse bias to the arms of the phase modulator.< >
IEEE Photonics Technology Letters 10/1995; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Spectrally and spatially resolved infrared microscopy has been used to study the steady state internal physics of semiconductor laser diodes. By imaging the longitudinal intra-cavity spontaneous emission profiles of both long wavelength bulk and MQW CMBH Fabry-Perot InGaAsP/InP lasers lasing at 1.48μm, we observed the longitudinal spatial hole burning above the lasing threshold
Device Research Conference, 1995. Digest. 1995 53rd Annual; 07/1995
-
[show abstract]
[hide abstract]
ABSTRACT: We have demonstrated the first monolithic integration of a DFB
laser with a Mach-Zehnder type modulator fabricated by the selective
area MOVPE growth technique and operating at 1.55 μm. A spatially
resolved micro photoluminescence setup was used to characterize the
crystal quality. We have achieved a low loss and near 3 dB Y-branch
power divider in the structure with the modulator achieving an
attenuation up to 17 dB and a π phase shift voltage of 2 V
Indium Phosphide and Related Materials, 1995. Conference Proceedings., Seventh International Conference on; 06/1995
-
[show abstract]
[hide abstract]
ABSTRACT: Performance characteristics of a pseudomorphic p‐type, normal incidence, Ge 0.25 Si 0.75 /Si strained‐layer quantum well infrared photodetector on (001) Si is described for 20≤T≤77 K. The device shows broadband photoresponse (8–14 μm) which is attributed to strain and quantum confinement induced mixing of heavy, light, and split‐off hole bands. Typical device responsivity at λ=10.8 μm is ∼0.04 A/W over the 20–77 K temperature range. A detectivity D<sup>*</sup> λ =3.3×10<sup>9</sup> cm √Hz/W was measured at a bias of -2.4 V for a temperature of 77 K at λ=10.8 μm and no cold shield. Room temperature FTIR measurements yield a quantum efficiency η≊3.1% at λ p ≊8 μm at 300 K.
Applied Physics Letters 09/1992; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A long-wavelength infrared imaging camera that uses a
GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>As quantum-well infrared
photodetector (QWIP) array is demonstrated. Excellent noise equivalent
temperature difference sensitivity
( NE Δ T <0.1°C) has been achieved. The
long-wavelength cutoff for the QWIP used in this camera is at λ
<sub>c</sub>=10.7 μm with the peak response being at λ<sub>p
</sub>=9.8 μm. A peak detectivity of 2×10<sup>10</sup>
cm√Hz/W has been achieved at 77 K as well as an excellent
pixel-to-pixel uniformity of 2%. Since GaAs has a more mature growth and
processing technology as well as higher uniformity than HgCdTe, it shows
great promise for the fabrication of large two-dimensional arrays
IEEE Transactions on Electron Devices 06/1991; · 2.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We discuss a new design for a voltage tunable graded barrier multiquantum well infrared detector. The tunability of this detector is significantly better than previous designs. It has large shifts in peak position, spectral width, and long‐wavelength cutoff.
Applied Physics Letters 08/1990; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Intersubband absorption in GaAs/AlGaAs multiple quantum wells (MQW) is measured using a novel integrated detector‐waveguide structure. The responsivity spectra of MQW infrared photodetectors is demonstrated to follow exactly the intersubband absorption spectra at various temperatures and bias. The blue shift of the bound‐to‐continuum state intersubband absorption peak with lowering of temperature is observed to track the change of the conduction‐band offset. The absorption peak showed only a slight Stark shift since the field in the wells is small in these narrow‐well/thick‐barrier structures and partly screened by the high doping.
Journal of Applied Physics 06/1990; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: By increasing the quantum well barrier width, we have dramatically reduced the tunneling dark current by an order of magnitude and thereby significantly increased the blackbody detectivity D<sup></sup> BB . For a GaAs quantum well infrared detector having a cutoff wavelength of λ c =10.7 μm, we have achieved D<sup>*</sup> BB =1.0×10<sup>1</sup><sup>0</sup> cm (Hz)<sup>1/2</sup>/W at T=68 K, a temperature which is readily achievable with a cryogenic cooler.
Applied Physics Letters 03/1990; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have studied the origin of the dark current in λ=8 μm peak wavelength 40‐Å GaAs/300‐Å Al 0.3 Ga 0.7 As multiple quantum well photodetectors. By carefully controlling the experimental conditions we have measured the dark current for temperatures in the range 4–120 K. The experimental characteristics are explained by thermionic emission for low biases and tunneling for high biases.
Journal of Applied Physics 01/1990; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We have measured the response time of a GaAs/Al x Ga 1-x As multiquantum well infrared detector (at a wavelength of λ=6.4 μm). The intrinsic rise time is determined to be less than 300 ps.
Journal of Applied Physics 08/1989; · 2.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Efficient coupling of long‐wavelength infrared (LWIR) radiation to a two‐dimensional (2‐D) array of GaAs/AlGaAs multiple quantum well detectors is achieved by illumination through chemically etched diffraction gratings. Gratings were fabricated on the back surface of the GaAs substrate as well as selectively on the top contact of the detector mesas. Both top and bottom illumination schemes were employed. In all cases, high coupling efficiency (≫90%) of the gratings was observed as measured by comparing the responsivity to that of an identical detector illuminated through an angle‐polished facet. The results demonstrate the feasibility of high‐sensitivity GaAs LWIR imagers.
Applied Physics Letters 07/1989; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Broadband GaAs/Al x Ga 1-x As quantum well infrared detectors grown by molecular beam epitaxy have been demonstrated which are sensitive over the λ=8–12 μm atmospheric window spectral region. These are the first high‐detectivity bound state to extended state quantum well detectors which are peaked at λ=10 μm. The spectral bandwidth (Δν/ν) of these devices is three times larger than our earlier λ=8 μm device. The detectivity D* is background limited at T=50 K with D*=1×10<sup>1</sup><sup>0</sup> cm (Hz)<sup>1/2</sup> /W, and a noise equivalent temperature change of NEΔT=0.01 K.
Applied Physics Letters 07/1989; · 3.84 Impact Factor
