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We present an experimental study of the turn-on delay in pulsed mid-infrared quantum cascade lasers. We report the unexpectedly long delay time depending on the pumping current, which does not agree with conventional theoretical predictions for step-like excitation. Similar behavior has been observed in InP- and InAs-based QCLs emitting near 8${\mu}$m. Numerical simulations performed using a model based on rate equations for excitation by current pulses with non-zero rise time provide fair agreement with our observations.

The spectral characteristics of a high-power semiconductor laser with an external cavity in which longitudinal-mode selection is implemented by means of a holographic volume Bragg grating recorded in photo-thermo-refractive glass are investigated. Mode selection leads to narrowing of the spectrum of the laser diode from an initial width of 6 nm to 5 A. In the narrowed spectrum, a fine structure representing a set of eigenmodes that correspond to the length of a laser chip is resolved. The number of these modes is limited by the width of the spectral selectivity curve of the grating. It is shown that insertion of the grating into the cavity leads to severalfold enhancement of the grating selectivity. It is demonstrated that the implemented external-cavity design makes it possible to smoothly tune the laser emission wavelength in a 10-nm range.

The process of charge carrier delocalization in high-power semiconductor lasers is examined under high current, pulse-pumped operation conditions. It is established that the carrier delocalization process is mostly determined by the injection of electrons (rather than holes) into the waveguide. Two methods of suppression of carrier delocalization are experimentally demonstrated, which are based on increasing the waveguide bandgap width and on using the waveguide containing a potential energy barrier for electrons in the p-region.

A new scheme of composite functional material based on an alloy exhibiting a shape-memory effect (SME) is proposed. The scheme provides for a giant reversible bending deformation with the use of only “one-way”-SME alloy. An experiment was performed with the use of actuator models manufactured by gluing together the rapidly quenched ribbons and electroplating the pseudoplastically predeformed ribbons of the alloy with nickel. It is shown that the theoretical estimates of the bending moment developed by the actuator and of the reversible deformations of the actuator are in good agreement with the results of the model experiments. The prospects for the use of the new scheme in micro- and nanomechanics are considered. Actuators with record small overall dimensions have been manufactured by the focused ion-beam technique.

New scheme of a functional composite material based on a shape memory alloy has been developed and experimentally tested. The proposed scheme ensures a giant reversible bending deformaion using only one-way shape memory. The scheme has been experimentally implemented on models manufactured by galvanic deposition of nickel onto preliminarily pseudoplastically deformed rapidly quenched Ti50Ni25Cu25 alloy ribbons. The proposed scheme is especially promising for applications in micro- and nanomechanics. In particular, prototype nanotweezers have been manufactured on this basis with record small dimensions of 12 × 3 × 1 μm and a 500-nm-thick shape-memory layer, which is capable of manipulating objects with sizes from 10 to 1000 nm. Controlled deformation of nanotweezers was achieved by heating them using semiconductor laser radiation in a vacuum chamber of scanning ion-probe microscope.

An approach to determine the optical modal gain spectra in multiple quantum-well semiconductor lasers based on InP in terms of the current at electrodes is presented. The link between the current at the electrodes and the density of carriers inside each quantum well was provided by rate equations with the inclusion of carrier transport effects. Description of hole dispersion is based on a 4 × 4 Luttinger–Kohn Hamiltonian and was done with the electrostatic effects of the carrier charges. Electrostatic effects were included via a self-consistent solution of electron and hole wave equations and the Poisson equation. The optical gain for the TE (transverse electric) mode has been determined with the inclusion of non-Markovian effects, Coulombic enhancement, and band-gap renormalization. The theoretical approach was compared with experimental measurements of the optical gain on a laser structure consisting of four quantum wells using the Hakki–Paoli method. The important role played by the leakage current was revealed when the results were compared. PACS No.: 73.63.Hs, 78.20.Bh, 78.20.Ci

Double heterostructure (DH) and quantum well (QW) EuSe/PbSe/Pb1−xEuxSe edge-emitting laser structures on Si substrates are grown by molecular-beam epitaxy. They operate up to 250 K when pumped with 870 nm low-cost laser diodes with peak powers of ∼7 W, and emit up to 200 mW peak output power at ∼5 μm wavelength. Differential quantum efficiencies are up to 20%. The threshold powers are limited by Shockley–Read recombination due to the high dislocation densities (108 cm−2) in the active layers. Nearly similar maximum operation temperatures were observed when employing (111)—instead of (100)—oriented layers, as well when using QW rather than DH structures. Reduction of dislocation densities to 107 cm−2 is feasible and will lead to nearly an order of magnitude lower threshold powers.

Dynamics of change of the laser heterostructure spectral characteristics under alternating strain caused by surface acoustic wave is investigated. The study of spectral distribution of the laser radiation intensity has been also fulfilled to reveal the interaction mechanisms in the studied structures. The interaction models are offered and the theoretical analysis of the obtained experimental data has been carried out. Is shown, that mainly acousto-electron interaction determines surface acoustic wave effect on spectral parameters of InGaAsP/InP laser radiation.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Power and spectral characteristics of Fabry-Perot semiconductor lasers based on at high excitation levels in pulsed lasing mode (200 A, 100 ns, 10 kHz) are investigated and double-band lasing is reached.

Investigations of stimulated recombination processes and reasons of output optical power saturation at superhigh pump levels (up to 0.1 MA/cm 2 ) of semiconductor lasers based on wide variety of quantum well heterostructures (l=980- 1900 nm) are presented for the first time.

The frequency modulation of the heterolaser radiation under the ultrasonic strain has been found out. The dynamic and static analysis of the spectral parameters change caused by the alternating strain has been fulfilled. A model is proposed for describing the experimental data, and their theoretical analysis is performed. It is demonstrated that the acousto-electron interaction is dominant under the action of surface waves in InGaAsP/InP laser heterostructures.

We report experimental study of generation of extracellular heat shock proteins (Hsp70) and ceramides under pulsed irradiation by quantum-well laser diodes. Our results are of great promise for applications in practical medicine such as protection against biopathogenes and abiotic stress factor challenges.

Experimental static and dynamic electro-optical characteristics of 905 nm high power mesa-stripe semiconductor laser diodes based on an AlGaAs/GaAs asymmetric heterostructure operating under Fabry–Perot cavity mode quenching have been investigated. We have shown that Fabry–Perot cavity mode reversible turn-off is due to the fulfillment of a high-Q closed mode threshold condition. The mode is propagating along both gain and passive areas of the laser diode and characterized by nearly zero output optical losses. We have demonstrated that fundamental reasons of closed mode threshold condition fulfillment are (i) gain spectra shift in the long wavelength region due to band gap shrinkage and thermal heating effects and (ii) the band gap absorption decrease in the passive area. It has been shown that the process of closed mode turn-on consists of two stages. In the first stage, Fabry–Perot cavity modes and closed modes are lasing simultaneously under high residual band gap absorption in the passive area. In the second stage, closed mode optical losses become lower than Fabry–Perot cavity mode optical losses due to a positive feedback between the residual absorption and closed mode photon stimulated generation rate. This results in an accumulation of photogenerated carriers in the quantum well active region of the laser diode passive area. As a result, the threshold concentration in the gain area decreases providing lasing emission switching from the Fabry–Perot cavity mode to the closed mode.