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5 Jan 1998

Volume 72, Issue 1, pp. 1-133

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Advantages of ultraviolet Raman scattering for high temperature investigations

E. Zouboulis, D. Renusch, and M. Grimsditch

Appl. Phys. Lett. 72, 1 (1998); http://dx.doi.org/10.1063/1.121437 (3 pages) | Cited 23 times

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We show that UV Raman spectroscopy is eminently well suited for the in situ investigation of samples at high temperatures. Using sapphire as a test material, we have recorded Raman spectra from ambient temperature to 1700 K using different excitation wavelengths, both in the visible and near UV region of the spectrum. These spectra show that, because of the very rapid decrease of blackbody radiation in the short wavelength region, Raman spectra recorded in the near UV region of the spectrum are free from the blackbody radiation background, which typically hampers experiments in the visible. With 266 nm exciting radiation, we observe no thermal background even at 1700 K. We foresee that the method will become a powerful tool for in situ investigations of high-temperature materials. © 1998 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
78.30.Am Elemental semiconductors and insulators

6.1 W continuous wave front-facet power from Al-free active-region (λ=805 nm) diode lasers

J. K. Wade, L. J. Mawst, D. Botez, R. F. Nabiev, M. Jansen, and J. A. Morris

Appl. Phys. Lett. 72, 4 (1998); http://dx.doi.org/10.1063/1.120628 (3 pages) | Cited 19 times

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Al-free active-region diode lasers grown by low-pressure, metal-organic chemical vapor deposition and emitting at λ=805 nm have been optimized for high continuous wave output power. The 1-mm-long devices consisting of an InGaAsP/In0.5Ga0.5P/In0.5(Ga0.5Al0.5)0.5P laser structure have a threshold-current density, Jth, of 310 A/cm2 and relatively high values for the characteristic temperatures of the threshold current, T0 (135 K), and differential quantum efficiency, T1 (900 K). Lasers with 10%/90% coatings and a 100-μm-wide stripe provide a maximum cw output power of 6.1 W at a heatsink temperature of 10 °C. The devices fail due to catastrophic optical mirror damage (COMD), where the internal power density, mathCOMD, is 17.4 MW/cm2; that is, twice that for conventionally facet-coated, 810 nm emitting, AlGaAs active-region diode lasers. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Two-color corrugated quantum-well infrared photodetector for remote temperature sensing

C. J. Chen, K. K. Choi, W. H. Chang, and D. C. Tsui

Appl. Phys. Lett. 72, 7 (1998); http://dx.doi.org/10.1063/1.120629 (3 pages) | Cited 26 times

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A quantum-well infrared photodetector (QWIP) based on the corrugated light-coupling scheme has been fabricated and tested for remote temperature sensing. The QWIP consists of two stacks of multiple quantum wells (MQWs), each sensitive in one of the atmospheric infrared transmission windows and each with a separate readout circuit. High optical coupling efficiency is obtained in both wavelength ranges, demonstrating the use of the corrugated structure for two-color detection. By monitoring the ratio of the photocurrent generated simultaneously in each MQW stack, the temperature of the object emitting the radiation can be determined, regardless of its emissivity and the geometrical factors. This temperature sensing ability is tested by using a blackbody radiator with precision temperature control as the target. The agreement between the measured and the preset temperatures indicates that the corrugated QWIP is capable of precision thermometric measurements. © 1998 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Qx Range finders, remote sensing devices; laser Doppler velocimeters, SAR, and LIDAR
95.75.Rs Remote observing techniques
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics

Simultaneous optimization of membrane reflectance and tuning voltage for tunable vertical cavity lasers

F. Sugihwo, M. C. Larson, and J. S. Harris

Appl. Phys. Lett. 72, 10 (1998); http://dx.doi.org/10.1063/1.120630 (3 pages) | Cited 15 times

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Micromachined wavelength tunable vertical cavity lasers are attractive for applications ranging from wavelength division multiplexing to spectroscopy. An improved tunable structure that incorporates a partial anti-reflection coating to increase coupling between the air gap and the semiconductor cavity, and a more flexible micromachine process that enables independent optimization of the central reflector region and deformable membrane structure are described. This combination of structural and process modifications enables decoupling the tradeoffs between wavelength tuning rate and threshold current, as well as the tradeoffs between top mirror reflectance and tuning voltage. With these improved approaches, a 2.5 pair dielectric distributed Bragg reflector hybrid membrane top mirror produced singlemode devices with a 23 nm wavelength tuning range and multi-transverse-mode devices with a 30 nm wavelength tuning range. Threshold current, differential quantum efficiency, and lasing mode are characterized as a function of membrane bias. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.86.+b Optical workshop techniques
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
42.79.Wc Optical coatings

Red–green–blue light emission from hydrogenated amorphous silicon carbide films prepared by using organic compound xylene as carbon source

Tianfu Ma, Jun Xu, Kunji Chen, Jiafang Du, Wei Li, and Xinfan Huang

Appl. Phys. Lett. 72, 13 (1998); http://dx.doi.org/10.1063/1.120631 (3 pages) | Cited 14 times

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We fabricated hydrogenated amorphous silicon carbide (a-Si1-XCX:H) films by the plasma-enhanced chemical vapor deposition technique using organic compound xylene (C8H10) as the carbon source, which was initially attempted by W. A. Nevin H. Yamagishi, M. Yamaguchi, and Y. Tawada, Nature 368, 529 (1994). Here we used different preparation conditions from those authors to produce xylene-based a-Si1-XCX:H films, and a different light emission behavior of the films has been observed at room temperature. The light emission wavelength can be shifted from 630 nm to 450 nm by changing the optical band gap (Eopt) of the films from 2.3 eV to 3.5 eV, nearly covering the whole visible light range, which was never reported previously. Fourier transform infrared spectra showed that the configuration of the material was a combination of organic aromatic rings and inorganic SiC networks. © 1998 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Gc Amorphous semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
63.50.-x Vibrational states in disordered systems
78.35.+c Brillouin and Rayleigh scattering; other light scattering
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
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