Influence of condensation of the emission spectrum on intracavity laser spectral analysis

A model of condensation of the laser emission spectrum in the spectral ranges of the absorption lines of the substance being studied was developed on the basis of a frequency-dependent absorbing intracavity lens. This model can explain most spectral condensation effects. It was shown that condensation of the emission spectrum is generally observed experimentally as a deformation of the dip profile in the laser emission spectrum. An analysis is made of the possibility of determining the concentration of an absorbing substance by measuring the spectral position of the peak of the condensed line. Pis’ma Zh. Tekh. Fiz. 24, 36–43 (September 26, 1998)     

Photodynamic effects in laser Doppler anemometry

The first observations of photodynamic effects in laser Doppler anemometry are reported, consisting in the fact that the result of a measurement of the Doppler shift of the frequency of light scattered by a particle depends on the action of the probe light beams on the particle. Pis’ma Zh. Tekh. Fiz. 24, 53–58 (September 12, 1998)     

Two-section InGaAsP/InP Fabry-Perot laser with a 12 nm tuning range

Wavelength tuning over a 12 nm range is obtained for a two-section InGaAsP/InP Fabry-Perot laser (λ=1.55 μm). The method used to vary the gain profile of the laser allows one to predict the range of possible wavelength tuning. Pis’ma Zh. Tekh. Fiz. 23, 10–15 (March 26, 1997)     

Laser autodyne interferometry of the dynamic parameters of biological specimens

A method based on the use of autodyne detection effects in a semiconductor laser is proposed to analyze the dynamic state of biological specimens. The advantages of this method compared with conventional photoelectric methods are demonstrated. Results are presented of the use of the proposed method to investigate the heart beat frequency and amplitude of Daphnia as a function of the degree of toxicity of the aqueous medium. Pis’ma Zh. Tekh. Fiz. 24, 39–43 (March 12, 1998)     

Formation of quasisteady supersonic flow with a pulse-periodic plasma heat source

An analysis is made of experimental data on the influence of a pulse-periodic optical discharge in a supersonic argon stream on the aerodynamic drag of streamlined objects. The interrelation established between the parameters of the laser radiation and the stream is used to determine the threshold frequency of the laser pulses which determines the transition to quasi-steady-state flow. Pis’ma Zh. Tekh. Fiz. 24, 8–13 (August 26, 1998)     

Fiber ring laser with locked relaxation oscillations

An investigation is made of the locking of the relaxation oscillations in a fiber ring laser with an active medium of phosphorus aluminosilicate glass doped with erbium and ytterbium ions. It is shown that stable pulse-periodic emission in the 1.5 /gmm range can be achieved at a pulse repetition frequency between 80 and 160 kHz with a pulse length of 2–3 μs. A single-mode model is used to determine the laser parameters (the pumping rate and the photon lifetime in the cavity). Pis’ma Zh. Tekh. Fiz. 25, 24–28 (January 26, 1999)     

Picosecond semiconductor lasers with a multisection saturable absorber, fabricated by heavy ion implantation

A method of implanting high-energy heavy ions across the emitter layer of a semiconductor laser has been developed to create distributed regions of ultrafast saturable absorber integrated into the cavity of a quantum-well laser. This method was used to fabricate picosecond laser diodes having high average powers and to demonstrate colliding-pulse mode-locking of a diode laser with a multisection saturable absorber. Pis’ma Zh. Tekh. Fiz. 25, 4–9 (July 12, 1999)     

Some laws governing laser beam ignition of an ethylene stream in air

The process of laser beam ignition of an ethylene stream in air has been studied experimentally. It has been established that the ignition process has two stages and the threshold power of the igniting laser radiation is extremely low. Pis’ma Zh. Tekh. Fiz. 23, 46–50 (December 26, 1997)     

Polarization-induced curvature of a laser damage channel

Significant curvature of a laser damage channel in a metal has been observed and a correlation is reported between this effect and the polarization of the radiation. Pis’ma Zh. Tekh. Fiz. 23, 90–94 (May 26, 1997)     

Multiwell laser heterostructures fabricated by liquid-phase epitaxy

A methodology has been developed for growing InGaAsP/InP multiwell laser heterostructures by liquid-phase epitaxy. Depth profiling using a secondary ion mass spectrometer was used to investigate the distribution profiles of the composition of multiwell laser heterostructures. Liquid-phase epitaxy was used to fabricate InGaAsP/InP multiwell laser heterostructures with active regions having emission wavelengths of 1.3 and 1.55 μm and their radiative characteristics were studied. Pis’ma Zh. Tekh. Fiz. 24, 61–67 (November 12, 1998)     

A negative-feedback garnet laser

A reduction in the time taken to achieve cw lasing from milliseconds to microseconds is obtained in an actively mode-locked Nd:YAG laser when weak, slow-response, negative feedback was inserted. The laser is designed to illuminate the photoinjector cathode of an electron accelerator. Pis’ma Zh. Tekh. Fiz. 23, 86–88 (April 12, 1997)     

Pair production in counterpropagating electron and laser beams

An analysis is made of the collision between a high-energy electron beam and laser radiation. It is shown that when the electron energy is 800 GeV and the laser pulse has an intensity of 10²⁰ W/cm², a wavelength of 248 nm, and a duration of 300 fs, a single seed electron produces 60 electrons and positrons. Pis’ma Zh. Tekh. Fiz. 23, 72–75 (July 26, 1997)     

Laser cleaning of a surface: a method for increasing analytical precision in laser mass spectrometry

A method is proposed for increasing the precision of the analysis of the atomic composition of solid materials using the éMAL-2 laser energy-mass analyzer. The basic idea of the method is to clean the sample by laser desorption of adsorbed residual gases during the interval between two ionizing laser pulses. A scheme for technical implementation of the proposed method is presented. Pis’ma Zh. Tekh. Fiz. 24, 61–65 (April 12, 1998)     

Formation of a low-resistivity penetrating metal-Si layer under the action of CO2 laser radiation

Some characteristic features observed as a result of the action of CO₂ laser radiation on a metal-silicon layer are described, especially the formation of a low-resistivity penetrating layer. The assumption is put forward that this low-resistivity penetrating layer forms as a result of the solid-phase dissolution of metal in Si or by diffusion of the metal into defects formed by laser radiation. Pis’ma Zh. Tekh. Fiz. 24, 60–63 (February 12, 1998)     

Ti:Al2O3 laser pumped by radiation from a copper-vapor laser

A scheme enabling spatial matching of copper-vapor laser radiation, which pumps a mode of an Al₂O₃:Ti laser cavity, has been developed and implemented. It is shown that copper vapor lasers as pump sources for titanium-sapphire lasers are fully capable of competing with conventional pump sources. Pis’ma Zh. Tekh. Fiz. 25, 6–11 (September 26, 1999)     

Operating characteristics and their anisotropy in a high-power laser (1.5 W, 300 K) with a quantum-dot active region

Continuous-wave lasing has been demonstrated in a vertically coupled quantum-dot laser with a high output power (1.5 W) at room temperature. It was shown that anisotropy of the quantum dot profile leads to anisotropy of the laser operating characteristics. Pis’ma Zh. Tekh. Fiz. 24, 50–55 (May 12, 1998)     

Optical method of determining the components of the relative displacement vector

The theory of a laser interference method of determining in real time the relative displacement of two scattering objects in space is put forward and an experimental verification is described. Pis’ma Zh. Tekh. Fiz. 25, 88–94 (December 26, 1999)     

Modulation of the polarization of semiconductor laser radiation at constant output power

The degree of polarization of “doubly”-modulated (by the pump current and the optical confinement factor) laser radiation is analyzed by applying a method of analyzing the stability of the solutions of systems of Lyapunov differential equations to a system of rate equations. An analysis of the system of rate equations yielded its eigenvalues, also called stability coefficients, which are the characteristic time for a transition of the system from one state to another. The behavior of a doubly modulated laser was modeled mathematically and it was demonstrated that the polarization of the laser output radiation can be controlled with almost constant output power. Pis’ma Zh. Tekh. Fiz. 24, 84–90 (August 26, 1998)     

Calculating the electromagnetic wave generated by the interaction between an ultrashort laser pulse and matter

A self-consistent solution is obtained for the problem of electron flux generation by interaction between an ultrashort laser pulse and a metal target. Pis’ma Zh. Tekh. Fiz. 24, 84–88 (March 12, 1998)     

Electron dynamics during laser neutralization of negative ions

A hydrodynamic approach is used to study the electron dynamics when laser radiation acts on a negative ion beam. An analytic solution of the problem is obtained. Pis’ma Zh. Tekh. Fiz. 24, 38–42 (May 12, 1998)