Study of characteristics of single-frequency GaAs/AlGaAs semiconductor lasers

Abstract

The whole-body dose from inhaled radionuclides is a complex function of factors that describe exposure and physiology. Exposure-related factors may be estimated by considering likely emission rates combined with measured time-varying meteorological (transport) parameters and estimated exercise patterns. Physiological factors, which strongly influence radionuclide intake and the consequent radiation dose, have been catalogued as functions of age and activity level. Both exercise patterns and physiological factors are related to the age of the exposed individual. Combining these factors permits estimates to be made of the span of exposures that may be expected in a typical population. The ratio of highest to lowest radionuclide intake is predicted to be of the order of 40, suggesting that specification of an 'average' value may be misleading if this value approaches regulatory limits. Individuals exposed to maximal risk may be identified, and these individuals are likely to be active children. Activity pattern (lifestyle) is a primary determinant of risk.

Spectral line broadening in quantum wells due to Coulomb interaction of current carriers

“…As it was concluded in work [1], at the non-equilibrium carrier concentration of 10 12 cm À2 the carrier intraband relaxation time increases and, therefore, the emission linewidth has to decrease. The former feature has not been observed experimentally [3,2,17]. In this case, the probability of optical transitions is nearly equal in a wide energy range and in the central part of the spectrum the optical transitions can be considered as recombination with no k-selection rule [18].…”

“…The exponent of the exponential multiplier, which is due to statistical factor (15), includes the minimum sum of the energies of interacting carriers at which the difference between the energies of the initial and final many-particle states (with regard to the quasi-momentum conservation) corresponds to the specified energy detuning from the center of the emission line, D_o 0 . In the other multiplier, the part with the exponent of 2 is due to the use of perturbation theory, while the remaining part is related to the form of matrix element of the Coulomb interaction (17). Thus, the spectral-line tails calculated by the above method would formally coincide with the Lorentzian function if the matrix element was assumed to be constant and the quasi-momentum conservation law was disregarded.…”

Modulation response of dynamic single-mode quantum-well heterolasers in the 1.5 μm range

“…For GaInAsP-InP lasers the half width of the laser output spectrum with a fiber Bragg grating is no more than 0.1 nm with pulsed modulation of the pump current at a frequency of up to ≈5 GHz. Other features of the output parameters of single frequency semiconductor lasers are discussed in [6][7][8][9][10][11]. Methods of creating dynamic single-frequency semiconductor lasers that operate stably to generate a single longitudinal mode even with high speed direct modulation and are used in fiber-optic communications have been examined in [12,13].…”

Semiconductor Lasing Wavelength in Heating Charge Carriers by Short Current Pulses

“…Moreover, we could not use the expression for the amplification coefficient [5], which depends only on the density and temperature of the carriers. The amplification coefficient, the rate of spontaneous transitions, and the rate equation for the photon density, with allowance for the spectral burning of carriers, are borrowed from [9], since the lasers under investigation have an undoped active region. Because of this, to perform calculations we have selected a model of emission transitions, wherein the rule of selection in the wave vector is fulfilled.…”