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28 Dec 1998

Volume 73, Issue 26, pp. 3803-3961

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Buried heterostructure InGaAsP/InP strain-compensated multiple quantum well laser with a native-oxidized InAlAs current blocking layer

Zhi Jie Wang, Soo-Jin Chua, Fan Zhou, Wei Wang, and Rong Han Wu

Appl. Phys. Lett. 73, 3803 (1998); http://dx.doi.org/10.1063/1.122899 (3 pages) | Cited 3 times

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An InAlAs native oxide is used to replace the p-n reverse-biased junction in a conventional buried heterostructure InP-based laser. This technique reduces the number of regrowth steps and eliminates leakage current under high-temperature operation. The InAlAs native oxide buried heterostructure (NOBH) laser with strain-compensated InGaAsP/InP multiple quantum well active layers has a threshold current of 5.6 mA, a slope efficiency of 0.23 mW/mA, and a linear power up to 22.5 mW with a HR-coated facet. It exhibits single transverse mode with lasing wavelength at 1.532 μm. A characteristic temperature (T0) of 50 K is obtained from the NOBH laser with a nonoptimized oxide layer width. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes

Growth of nonlinear optical thin films of KTa1−xNbxO3 on GaAs by pulsed laser deposition for integrated optics

L. A. Knauss, K. S. Harshavardhan, H.-M. Christen, H. Y. Zhang, X. H. He, Y. H. Shih, K. S. Grabowski, and D. L. Knies

Appl. Phys. Lett. 73, 3806 (1998); http://dx.doi.org/10.1063/1.122900 (3 pages) | Cited 10 times

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We report successful deposition of epitaxial nonlinear KTa0.52Nb0.48O3 (KTN) films on (100) GaAs substrates. A buffer layer scheme consisting of epitaxial MgO and SrTiO3 buffer layers and a Si3Ni4 encapsulation of the substrate was developed to alleviate chemical and structural incompatibilities between the GaAs substrate and KTN film at the growth temperature (∼750 °C). The structure, composition, and preliminary optical properties of the KTN films were evaluated by four-circle x-ray diffraction, Rutherford backscattering spectrometry, and prism coupled optical waveguide mode measurements, respectively. We observed sharp and distinguishable transverse electric and transverse magnetic propagating modes in the KTN films, and measured the refractive index (n0) of the film at 488 nm to be 2.275 which is close to the bulk value of 2.35, all of which indicates a high structural and optical film quality. © 1998 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
42.65.Wi Nonlinear waveguides
42.82.Et Waveguides, couplers, and arrays
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Mp Nonlinear optical crystals
42.79.Wc Optical coatings

Large enhancement in quasiphase matched second-harmonic generation efficiency by an external temperature gradient

Ranjit D. Pradhan and Noureddine Melikechi

Appl. Phys. Lett. 73, 3809 (1998); http://dx.doi.org/10.1063/1.122901 (3 pages) | Cited 2 times

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We show that for continuous wave second-harmonic generation using quasiphase matching in periodically segmented waveguides, thermal loading caused by the fundamental and the generated beams degrades the quasiphase matching condition which corrupts the spectral quality of the second-harmonic field. We also show that a carefully designed external temperature gradient leads to an enhancement of the conversion efficiency and control of the spectral line shape of the output field. Compared to earlier work, our simple scheme yields an enhancement of the second-harmonic conversion efficiency by a factor of 2–4 depending on the input fundamental power. © 1998 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Effect of detuning on the angular emission pattern of high-efficiency microcavity light-emitting diodes

C. Dill, R. P. Stanley, U. Oesterle, D. Ochoa, and M. Ilegems

Appl. Phys. Lett. 73, 3812 (1998); http://dx.doi.org/10.1063/1.122902 (3 pages) | Cited 10 times

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Results on molecular beam epitaxy-grown microcavity light-emitting diodes with InGaAs/GaAs quantum wells and a hybrid top mirror are presented. An external quantum efficiency of 14.8% is achieved for a 400 μm diam light-emitting diode. The strong influence of the spectral overlap between the spontaneous emission spectrum and the cavity resonance mode on the radiation pattern is shown. The angular emission profile is compared with model predictions for different detunings, and a very good agreement is obtained when the asymmetric spectral broadening of the intrinsic spontaneous emission is taken into account. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.60.Jb Light-emitting devices
42.55.Px Semiconductor lasers; laser diodes
73.61.Ey III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.By Design of specific laser systems

Island size effects in nanoparticle-enhanced photodetectors

Howard R. Stuart and Dennis G. Hall

Appl. Phys. Lett. 73, 3815 (1998); http://dx.doi.org/10.1063/1.122903 (3 pages) | Cited 132 times

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We report the effect of metal-island size variation in nanoparticle-enhanced photodetectors. Nanoparticle size was controlled by varying the deposition and annealing conditions used to produce the metal-island films. Increasing the size of silver-island particles fabricated onto 165 nm thick silicon-on-insulator (SOI) photodetectors resulted in a dramatic increase in the observed photocurrent. A nearly factor-of-20 photocurrent enhancement was observed for light of wavelength 800 nm, a significant improvement over previously reported results. The improvement is linked to two physical effects: the increased scattering efficiency of the larger nanoparticles and a qualitative change in the resonance characteristics of the metal-island film due to radiative coupling to the SOI waveguide modes. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Bz Metals and metallic alloys
78.40.Kc Metals, semimetals, and alloys
73.50.Mx High-frequency effects; plasma effects
73.40.Sx Metal-semiconductor-metal structures

Saturation of intraband absorption and electron relaxation time in n-doped InAs/GaAs self-assembled quantum dots

S. Sauvage, P. Boucaud, F. Glotin, R. Prazeres, J.-M. Ortega, A. Lemaître, J.-M. Gérard, and V. Thierry-Flieg

Appl. Phys. Lett. 73, 3818 (1998); http://dx.doi.org/10.1063/1.122904 (4 pages) | Cited 23 times

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We have observed the saturation of intraband absorption in InAs/GaAs self-assembled quantum dots. The investigated n-doped self-assembled quantum dots exhibit an intraband absorption within the conduction band, which is peaked at an 8 μm wavelength. The saturation of the intraband absorption is achieved with an infrared pump delivered by a pulsed free-electron laser. The saturation of the transition is observed for an intensity around ≈0.6 MW cm−2. The electron relaxation time under intraband excitation is measured by time-resolved pump–probe experiments. An electron relaxation time T1 ≈ 3 ps is reported. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Simultaneous sampling of optical pulse intensities and wavelengths by four-wave mixing in a semiconductor optical amplifier

S. Diez, C. Schmidt, D. Hoffmann, C. Bornholdt, B. Sartorius, H. G. Weber, L. Jiang, and A. Krotkus

Appl. Phys. Lett. 73, 3821 (1998); http://dx.doi.org/10.1063/1.122905 (3 pages) | Cited 5 times

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An all-optical sampling technique that allows the simultaneous measurement of optical pulse intensities and wavelengths with a temporal resolution of about 1 ps is introduced. Using four-wave mixing (FWM) in a semiconductor optical amplifier, the optical signal under test is cross correlated with nearly transform-limited 1.4 ps optical sampling pulses. While the intensity of the generated FWM signal is used to determine the temporal shape of the signal intensity, the wavelength of the FWM signal yields time-resolved information about the signal wavelength (i.e., the frequency chirp). Using this technique, the correlation of intensity and wavelength dynamics of pulses generated by a self-Q-switched distributed-feedback laser is determined directly. © 1998 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers

Generation and detection of coherent terahertz waves using two photomixers

S. Verghese, K. A. McIntosh, S. Calawa, W. F. Dinatale, E. K. Duerr, and K. A. Molvar

Appl. Phys. Lett. 73, 3824 (1998); http://dx.doi.org/10.1063/1.122906 (3 pages) | Cited 78 times

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A general technique has been demonstrated at microwave and submillimeter-wave frequencies for photoconductive sampling in the frequency domain using photomixers and continuous-wave laser diodes. A microwave version in which two photomixers were coupled by a transmission line was developed to quantitatively test the concept from 0.05 to 26.5 GHz. A quasioptical version using antenna-coupled photomixers was demonstrated from 25 GHz to 2 THz. Such a system can outperform systems based on time-domain photoconductive sampling in frequency resolution, spectral brightness, system size, and cost.
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84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.40.Ba Antennas: theory, components and accessories
72.40.+w Photoconduction and photovoltaic effects
85.60.Gz Photodetectors (including infrared and CCD detectors)

Single-wall carbon nanotubes synthesized by laser ablation in a nitrogen atmosphere

Y. Zhang, H. Gu, and S. Iijima

Appl. Phys. Lett. 73, 3827 (1998); http://dx.doi.org/10.1063/1.122907 (3 pages) | Cited 27 times

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The products of laser ablation of graphite in a nitrogen atmosphere have been studied by transmission electron microscopy and electron energy-loss spectroscopy. Using nickel and cobalt as catalyst, single-wall carbon nanotubes can be produced with a yield similar to that obtained in an inert gas. Nitrogen has not been found in the nanotubes and crystallized fullerenes although it has been detected in amorphous carbon. A growth model has been proposed to explain the experimental results. © 1998 American Institute of Physics.
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81.05.ub Fullerenes and related materials
81.15.Fg Pulsed laser ablation deposition
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
79.20.Kz Other electron-impact emission phenomena

Noncascaded intersubband injection lasers at λ ≈ 7.7 μm

Claire Gmachl, Federico Capasso, Alessandro Tredicucci, Deborah L. Sivco, Albert L. Hutchinson, S. N. George Chu, and Alfred Y. Cho

Appl. Phys. Lett. 73, 3830 (1998); http://dx.doi.org/10.1063/1.122908 (3 pages) | Cited 10 times

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The realization of the first noncascaded intersubband injection lasers based on a single optical transition is reported. The unipolar lasers are based on an active region consisting of three InGaAs quantum wells closely coupled by thin AlInAs barriers. The lasers emit at λ ≈ 7.7 μm wavelength and operate in pulsed mode up to 110 K. Peak power levels of 20 mW at 10 K and 4 mW at 110 K are obtained. The low-temperature threshold current density is 25.6 kA cm−2 in good agreement with calculations. Several advantages arise from this novel type of intersubband laser. First, only few layers are necessary to build the active region, simplifying sample preparation. Second, low operating voltages can be achieved, which is essential for many applications. Finally, the noncascaded intersubband laser allows studying fundamental properties of quantum cascade lasers without possible artifacts introduced by the sequential stacking of many active regions. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Above-room-temperature optically pumped midinfrared W lasers

W. W. Bewley, C. L. Felix, E. H. Aifer, I. Vurgaftman, L. J. Olafsen, J. R. Meyer, H. Lee, R. U. Martinelli, J. C. Connolly, A. R. Sugg, G. H. Olsen, M. J. Yang, B. R. Bennett, and B. V. Shanabrook

Appl. Phys. Lett. 73, 3833 (1998); http://dx.doi.org/10.1063/1.122909 (3 pages) | Cited 44 times

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We report temperature-dependent pulsed lasing performance, internal losses, and Auger coefficients for optically pumped type-II W lasers with wavelengths in the range of 3.08–4.03 μm at room temperature. All lased to at least 360 K, and produced 1.5–5 W peak power at 300 K. Internal losses at 100 K were as low as 10 cm−1, but increased to 90–360 cm−1 at 300 K. Room temperature Auger coefficients varied from 5×10−28 cm6/s at the shortest wavelength to 3×10−27 cm6/s at the longest. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
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