Economic Ideas and Institutional Change: Evidence from Soviet Economic Discourse 1987-1991

In recent years, institutional and evolutionary economists have become increasingly aware that ideas play an important role in economic development. In the current literature, the problem is usually elaborated upon in purely theoretical terms. In the present paper it is argued that ideas are always also shaped by historical and cultural factors. Due to this historical and cultural specificity theoretical research must be supplemented by historical case studies. The paper analyses the shift in ideas that took place in Soviet economic thought between 1987 and 1991. This case study, it is argued, may contribute to our understanding of the links between ideas and institutions. More specifically, it sheds new light on the issue of whether the evolution of economic ideas is pathdependent, so that they change only incrementally, or whether their development takes place in a discontinuous way that can best be compared with revolutions

Effect of spatial hole burning on output characteristics of high power edge emitting semiconductor lasers:a universal analytical estimate and numerical analysis

Abstract The effect of longitudinal spatial hole burning on the performance of a semiconductor laser with a strongly asymmetric resonator is investigated numerically. The effects of spatial hole burning on, firstly, the non-stimulated recombination in the laser (quantified as an increased effective threshold current) and, secondly, the output efficiency are calculated and compared, and the latter is shown to dominate at high currents. It is shown that the output efficiency at high pumping levels in the presence of the spatial hole burning effect can be estimated using the standard expression as the ratio of output loss to total loss, but with the internal loss enhanced by a factor greater than one and independent on the injection level. A simple universal expression for this factor for a highly asymmetric cavity, as a function of the output mirror reflectance, is obtained and compared to numerical results, with good agreement

Strong doping of the n-optical confinement layer for increasing output power of high- power pulsed laser diodes in the eye safe wavelength range

Abstract An analytical model for internal optical losses at high power in a 1.5 μm laser diode with strong n-doping in the n-side of the optical confinement layer is created. The model includes intervalence band absorption by holes supplied by both current flow and two-photon absorption (TPA), as well as the direct TPA effect. The resulting losses are compared with those in an identical structure with a weakly doped waveguide, and shown to be substantially lower, resulting in a significant improvement in the output power and efficiency in the structure with a strongly doped waveguide

Increasing output power of pulsed-eye safe wavelength range laser diodes by strong doping of the n-optical confinement layer

Abstract A semi-analytical model for internal optical losses at high power in a 1.5 μm laser diode with strong n-doping in the n-side of the optical confinement layer is created. The model includes intervalence band absorption by holes supplied by both current flow and two-photon absorption. The resulting losses are shown to be substantially lower than those in a similar, but weakly doped structure. Thus a significant improvement in the output power and efficiency by strong n-doping is predicted

Optical loss suppression in long-wavelength semiconductor lasers at elevated temperatures by high doping of the n-waveguide

Abstract We show that strong n-doping of the n-waveguide layer substantially decreases the thermal carrier leakage from the active layer and the associated optical losses in III–V semiconductor lasers. The effect is particularly pronounced in devices operating at the wavelength region where the free hole absorption cross-section is much greater than that of free electrons. This is predicted to decrease the threshold current and improve the output efficiency of the lasers. An example of a bulk InGaAsP/InP pulsed lasers is used to demonstrate that lasers with highly doped n-InGaAsP side of the waveguide can retain high output powers at ambient temperatures substantially above room temperature

Asymmetric-waveguide, short cavity designs with a bulk active layer for high pulsed power eye-safe spectral range laser diodes

Abstract It is shown, by calculations calibrated against the authors’ recent experimental data, that an eye-safe wavelength range InGaAsP/InP high pulsed power laser design using a bulk active layer, which has a large refractive index step with respect to the optical confinement layer and is located close to the p-cladding, can provide substantial performance improvement compared to the best results achieved so far for this operating regime and wavelength. The dependence of the laser performance on the design parameters such as the thicknesses of the active layer and the waveguide, as well as the cavity length, are analysed. It is shown that the relatively thick bulk active layer in such InGaAsP/InP lasers allows the use of short cavity lengths (~1 mm or even shorter), for achieving high pulsed power while maintaining a low p-cladding series resistance (making for high efficiency) and a narrow far field (making for high brightness). A single-asymmetry structure with the asymmetric active layer location but symmetric optical confinement layer/cladding refractive index steps gives performance only marginally inferior to that of a double-asymmetric one including asymmetric refractive index steps

High Power 1.5 μm pulsed semiconductor laser design with a bulk active layer and an asymmetric waveguide

Abstract InGaAsP/InP high pulsed power lasers operating in the range of 1.3–1.6 μm have been intensely studied recently, with LIDAR technology being the primary application. We present and analyse a design with a bulk active layer which has a large refractive index step with respect to the optical confinement layer and is located close to the p-cladding. It is shown that such lasers can allow a noticeable performance increase over the state of the art. The dependence of the laser performance on the design parameters including the thicknesses of the active layer and the waveguide, the cavity length, and the waveguide asymmetry, is analysed. It is shown that short cavity lengths (~1 mm or even shorter) can be used in the design considered for achieving high pulsed power. Due to the significant waveguiding properties of the active layer, the use of both symmetric and asymmetric waveguide designs is possible, with only slightly higher output predicted for the asymmetric one. Both designs allow operation with a single, broad transverse mode enabling high brightness

Laser diode structures with a saturable absorber for high-energy picosecond optical pulse generation by combined gain-and Q-switching

Abstract The performance of gain-switched Fabry-Perot asymmetric-waveguide semiconductor lasers with a large equivalent spot size and an intracavity saturable absorber was investigated experimentally and theoretically. The laser with a short (~ 20 μm) absorber emitted high-energy afterpulse-free optical pulses in a broad range of injection current pulse amplitudes; optical pulses with a peak power of about 35 W and a duration of about 80 ps at half maximum were achieved with a current pulse with an amplitude of just 8 A and a duration of 1.5 ns. Good quality pulsations were observed in a broad range of elevated temperatures. The introduction of a substantially longer absorber section lead to strong spectral broadening of the output without a significant improvement to pulse energy and peak power

Double-asymmetric-structure 1.5 μ m high power laser diodes

Abstract Design considerations for high pulsed power and brightness 1.5 μm laser emitters for laser radar applications, based on comprehensive semi-analytical theory, are presented. A strongly asymmetric waveguide design with a bulk active layer positioned very near the p-emitter interface is chosen to minimize the current-induced losses at high power while maintaining a single, broad transverse mode. Moderate to high doping of the n-side of the Optical Confinement Layer and high p-doping of the p-cladding layer are used to reduce the residual current-induced losses and the electric resistance of the structure. For pulsed room-temperature operation, short laser resonators are found to be advantageous. First experimental results are presented. An as-cleaved sample with a stripe width of 90 μm and a resonator 2 mm long exhibits an output power of about 18 W at a pumping current amplitude of 80 A, with 1 mm long resonators showing higher power output. Further improvements are predicted by structure optimization as well as increase in internal quantum efficiency and thermal performance

Solid-state block-based pulsed laser illuminator for single-photon avalanche diode detection-based time-of-flight 3D range imaging

Abstract A laser diode illuminator for single-photon avalanche diode detection-based pulsed time-of-flight 3D range imaging is presented. The illuminator supports a block-based illumination scheme and consists of a 16-element custom-designed common anode quantum-well laser diode bar working in the enhanced gain switching regime and lasing at ∼810  nm. The laser diode elements are separately addressable and driven with gallium nitride drivers, which produce current pulses with a width of ∼2  ns; the current pulse amplitude was estimated from the supply voltage (90 V) as 5 to 10 A. Cylindrical optics are used to produce a total illumination field-of-view of 40  ×  10  deg2 (full width at half maximum) in 16 separately addressable blocks. With a laser pulsing frequency of 256 kHz and laser pulse energy of ∼8.5  nJ, the average optical illumination power of the transmitter is 2.2 mW