V. K. Kononenko

Multiple-wavelength lasing in one-dimensional bandgap structures: implementation with active n–i–p–i layers

We study the optical localized states in a one-dimensional system of strongly coupled defect microcavities for the case when a tight-binding approximation is not valid. Transmission and electromagnetic mode density spectra as well as the distribution of light intensity inside the bandgap material are investigated. We report on the effect of splitting the fundamental coupled-cavity mode into several high-Q submodes to support perfect transmission of light at low group-velocity values. New types of laser microcavities that provide low-threshold lasing at multiple wavelengths and in opposite directions are proposed. Possible implementation of the laser systems with active n–i–p–i layers is discussed.

Temperature dependence of the threshold and Auger recombination in asymmetric quantum-well heterolasers

The temperature dependence of the lasing threshold in the GaInAs-GaInAsP-InP bi-quantum-well heterolasers with different widths of the quantum wells (4 and 9 nm) has been determined. Processes of non-radiative Auger recombination which occur in the active region of the quantum-well lasers have been included into consideration. The analytical approach for the evaluation of the characteristic temperature of the lasing threshold is presented. For described asymmetric quantum-well heterostructure lasers, it is shown that the influence of Auger recombination processes on the temperature behavior of the lasing threshold is not essential until the temperature of the active region is lower than 360 K and the cavity losses do not exceed 80 cm-1.

Photonic bandgap structures with n-i-p-i layers

Optical properties of one-dimensional heterostructures having optical forbidden gap are described and photonic structures with n-i-p-i superlattices are designed for laser applications.

Polarization of the radiation of a size-quantized heterojunction laser with a selective cavity

The effect of a selective cavity with a diffraction grating on the radiation polarization of a size-quantized heterojunction laser has been theoretically investigated. The variation of the degree of polarization as a function of the relationship of the optical loss factors is established for the TE and TM modes. Ways are determined for optimizing single-mode lasing of radiation of the required polarization.

Nonlinear Response of the Semiconductor Laser with Pump Current Modulation

The influence of tuning the lasing monochromatic radiation frequency νg within the amplification band on the nonlinear response of the semiconductor laser with harmonic modulation of pump current is investigated theoretically. It is established that the principal features of the behavior of the nonlinear amplitude-detuning characteristic (ADC) are determined by the relation between the current modulation frequency νm and the main resonance frequency of the laser νr. If νm ≥ νr, then with increase in νg the response decreases monotonically mainly due to the decrease of its dynamic component. The exception is provided by the spectral regions where peaks on the ADC appear because of the explicitly nonlinear lasing regimes (period doubling, chaos, etc.) When νm < νr, the resonance conditions for induced oscillations are satisfied only for definite spectral intervals within the amplification band and a dip appears on the low-frequency side of the ADC. With decreasing νm, the dip boundary shifts to a more high-frequency region of the band corresponding to smaller local resonance frequencies. The peaks on the ADC corresponding to the radiation period doubling shift to the region of smaller values of νg on increase in νm.

Radiative characteristics of a two-section laser structure based on a δ-doping superlattice

Spectral characteristics of a two-section laser structure with δ-doping active regions are studied theoretically. The wide range of tuning of the lasing wavelength is primarily related to specific characteristics of the gain spectra of n-i-p-i crystals: the dependence of the effective band-gap width of the superlattice on the level of excitation, the character of variation of the overlap integrals of the electron and hole wave functions, and broadening of the electronic spectra due to fluctuations of the electrostatic potential. Depending on the pumping currents in sections of the laser structure, the lasing wavelength can be tuned over a wide spectral range of the IR region in regimes of cw lasing, the transient regime, and the regime of regular pulsations. In the regime of self-sustaining pulsations, lasing is also possible at two wavelengths spaced well apart.

TUNABLE PHOTOLUMINESCENCE SPECTRA OF DOPED SEMICONDUCTOR SUPERLATTICES

Taking into account the density state tails appearing due to fluctuations of impurity concentrations, the spontaneous emission spectra of doped semiconductor superlattices are calculated. In the framework of the model developed, the explanation of the experimentally observed longwave edge and the shift of the photoluminescence spectra with increase in the excitation level and temperature is given. The role of the defects formed on α-irradiation is discussed, and the lifetime of current carriers is evaluated depending on the design parameters and excitation conditions of the GaAs doped superlattices.

Current carrier lifetime in doping superlattice crystals

It is shown, that the lifetime of nonequilibrium current carriers in the luminescence process in doping superlattice structures changes in a wide range with increasing the excitation level of the crystal. Two effects are important, i.e., (1) low-dimensional character of the carrier distribution and (b) change in the overlap of electron and hole wave functions. At low excitation, non-radiative recombination can play principal cause in the stabilization of the effective lifetime of current carriers. At high excitation, the effective lifetime of current carriers approaches the value in the bulk crystal. The major attention was given to the compensated GaAs doping superlattices with i -layers (n -i -p -i crystals) and to the structures with no i -layers (n -p -n -p structures). The layer thickness of n -, p -, and i -type were 20, 40, or 60 nm and the concentrations of the dopants Te and Zn made up to 1018 cm-3. Photoluminescence spectra and the decay time of the spontaneous emission intensity in the superlattices were measured at the temperature interval from 11 to 300 K. The influence of α-particle irradiation and thermal annealing on the luminescence spectra and the carrier lifetime was also investigated.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.