High-power 1.7–1.8 μm single-mode laser diodes

Separate confinement InGaAsP/InP laser heterostructures were grown by metalorganic-hydride vapor-phase epitaxy. High-power single-mode laser diodes of mesastripe design based on these heterostructures operate in a wavelength interval of 1.7–1.8 μm with a maximum continuous room temperature output power of 150 mW. The single-mode lasing regime is maintained up to an output power level of 100 mW.     

Studying the characteristics of pulse-pumped semiconductor 1060-nm lasers based on asymmetric heterostructures with ultrathick waveguides

High-power semiconductor lasers based on asymmetric quantum-dimensional separate confinement InGaAs/GaAs heterostructures with ultrathick waveguides were fabricated by means of metalorganic hydride vapor phase epitaxy technology. The laser characteristics were studied in a pulsed pumping regime, in which the emission was excited by current pulses of 100 ns duration at a repetition frequency of 10 kHz and an amplitude of up to 200 A. The passage to a pulsed lasing regime allowed the active region heating to be reduced and the output power to be increased to 145 W for a laser diode with a 100-μm exit aperture. The results obtained for the pulsed lasing regime show that saturation of the output power-current characteristic observed in the continuous-wave regime is fully determined by overheating of the active region of a semiconductor laser.     

SIMILARITY‐BASED RETRIEVAL WITH STRUCTURE‐SENSITIVE SPARSE BINARY DISTRIBUTED REPRESENTATIONS

We present an approach to similarity‐based retrieval from knowledge bases that takes into account both the structure and semantics of knowledge base fragments. Those fragments, or analogues, are represented as sparse binary vectors that allow a computationally efficient estimation of structural and semantic similarity by the vector dot product. We present the representation scheme and experimental results for the knowledge base that was previously used for testing of leading analogical retrieval models MAC/FAC and ARCS. The experiments show that the proposed single‐stage approach provides results compatible with or better than the results of two‐stage models MAC/FAC and ARCS in terms of recall and precision. We argue that the proposed representation scheme is useful for large‐scale knowledge bases and free‐structured database applications.     

Effect of the active region thickness on characteristics of semiconductor lasers based on asymmetric AlGaAs/GaAs/InGaAs heterostructures with broadened waveguide

The effect of the active region thickness on the basic characteristics of high-power semiconductor lasers based on AlGaAs/GaAs/InGaAs asymmetric separate-confinement heterostructures grown by MOCVD epitaxy has been studied. It is shown that the threshold current, temperature sensitivity of the threshold current density, internal quantum efficiency of stimulated emission, and differential quantum efficiency are improved as the active region thickness increases. It is demonstrated that the maximum attainable optical emission power of a semiconductor laser and the internal quantum efficiency of photoluminescence are the most sensitive to defect formation in the heterostructure and become lower as the critical thickness of the strained In_xGa_1–x As layer in the active region is exceeded.     

Resolution of Binary Coding of Real-Valued Vectors by Hyperrectangular Receiptive Fields

Schemes of binary coding of real-valued vectors are considered. Hyperrectangular receptive fields such as RSC and Prager randomly distributed fields and CMAC regular fields are analyzed. Theoretical and experimental estimations of resolving power (resolution) of codes and the comparative analysis of coding schemes are presented. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 5, pp. 3–15, September–October 2005.     

High-power laser diodes (λ = 808–850 nm) based on asymmetric separate-confinement heterostructures

Symmetric and asymmetric separate-confinement AlGaAs/GaAs heterostructures have been grown by MOCVD in accordance with the concept of design of high-power semiconductor lasers. High-power laser diodes with a 100-μm aperture, emitting in the 808–850-nm range, were fabricated from these structures. The internal optical loss in asymmetric separate-confinement heterostructures with broadened waveguide is reduced to 0.5 cm⁻¹. In the lasers with 1.7-μm-thick waveguide, the output optical power of 7.5 W in CW mode was achieved owing to reduction of the optical emission density at the cavity mirror to 4 mW/cm². Original Russian Text ? A.Yu. Andreev, A.Yu. Leshko, A.V. Lyutetskiĭ, A.A. Marmalyuk, T.A. Nalyot, A.A. Padalitsa, N.A. Ptkhtin, D.R. Sabitov, V.A. Simakov, S.O. Slipchenko, M.A. Khomylev, I.S. Tarasov, 2006, published in Fizika i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 628–632.     

Frequency–Time Method of Processing Phase Measurements in Geophysics

A frequency–time method is proposed for analyzing geophysical phase information whose implementation approaches the results of the operation of an ideal filter. The method is based on the principle of expanding an observed signal over a system of basis functions. The procedure developed makes it possible to determine the phase of the signal and to estimate the operational stability of the phase measuring system. The procedure can be used when designing geophysical measuring devices utilizing optical phase measurements.