A. P. Danilova

A tunable single-mode 3.2 μm laser based on an InAsSb/InAsSbP double heterostructure with drive-current tuning range of 10 cm−1

A new type of semi-conductor laser with composition InAsSb/InAsSbP is described. This laser was produced for the absorption spectroscopy of atmospherically important molecules in the 3100 cm(-1) region and tested using a closed-cycle He-cryostat in the temperature range 30-80 K. The optimal characteristics of the laser were found to be a heatsink temperature of 62 K and a drive current range of 50-350 mA. Under these conditions, the laser emits single-mode radiation in an exceptionally large wavenumber range of > 10 cm(-1). To test the laser, several experiments were carried out in which the rovibrational absorption spectra of CH3Cl, NH3, OCS and H2O were measured.

Two-mode diode-laser spectroscopy with a InAsSb/InAsSbP laser near 3.6 µm

The current dependence of the output frequency of InAsSb/InAsSbP diode lasers at wavelengths near 3.6 µm is studied. It is found that in these lasers the number of lasing modes can be reduced without introducing crystallographic defects. It is shown that the photon momentum aids in suppressing the spectral modes closest to the dominant mode. Two-mode laser spectroscopy is done over an interval of 2 cm−1 for two gases, N2O and CH3Cl.

Short-wavelength current tuning of InAsSb/InAsSbP heterostructure lasers caused by an injection nonuniformity

A reduction in the emission wavelength in the preferred mode of InAsSbP/InAsSb/InAsSbP heterostructure lasers by 50Å is observed when the current is raised from 1.8 to 5 times the threshold with dc and pulsed power. A comparison of the spectral and spatial distributions of the output as functions of current shows that this short-wavelength tuning is caused by a change in the distribution of the nonequilibrium charge carrier concentration over the strip width as the current is varied. This effect is modeled mathematically, taking into account the increase in the injection density and the drop in the output intensity from the middle to the sides of the waveguide. The results of the model calculation are in good agreement with experiment.

Rapid tuning of the generation frequency of InAsSb/InAsSbP diode lasers (λ=3.3 µm) due to nonlinear optical effects

A study has been made of wavelength tuning in double heterostructure InAsSb/InAsSbP-based diode lasers. A simple mathematical model, which takes into account the spatially homogeneous injection and the dependence of the dielectric constant on the charge carrier density, is discussed. The wavelength can be increased or decreased, depending on the pump current and diode structure parameters, as is observed experimentally. The process of wavelength tuning proceeds with virtually zero delay time since it is determined by the photon lifetime in the cavity and in part by the lifetime of nonequilibrium charge carriers.

InAsSb/InAsSbP diode lasers with separate electrical and optical confinement, emitting at 3–4 µm

Diode lasers based on InAsSb/InAsSbP with separate electrical and optical confinement, emitting in the wavelength interval 3–4 µm, are investigated. The lasers attain a higher operating temperature when electrical confinement is created by means of type-II heterojunctions. Interface Auger recombination is suppressed in lasers of this type, and the experimental current density is close to the theoretically calculated value for the case of predominant volume Auger recombination at a temperature of 180–220 K.

Single-mode InAsSb/InAsSbP laser (λ≈3.2 μm) Tunable over 100 Å

A report is presented on the development of a single-mode laser based on the InAsSb/InAsSbP double heterostructure and operating at wavelengths of 3.2–3.3 µm in a temperature range of 12–90 K. The single-mode regime is assumed to be realized due to a smooth optical waveguide formed across the laser cavity in which the radiation flux oscillates and maintains its oscillations and intensity. An analysis is made of the effect of the current-induced shifts of the lasing frequency and the peak of the gain spectrum on the probability of single-mode lasing. Experiments were made on the scanning of OCS, NH3, CH3Cl, and H2O gas media with radiation of the given laser in the frequency range with a record width of 10 cm−1 (104 Å).

InAsSb/InAsSbP heterostructure lasers with a large range of current tuning of the lasing frequency

The lasing spectra and the shift in the position of the modes in the current range (1–5)Ith with various methods of pumping the nonequilibrium charge carriers are analyzed. It is shown that the pumping method does not influence the character of the tuning of the radiation line. The large short-wavelength tuning range (up to 50 Å) is due not to the heating of the crystal lattice in the active-region material but rather the nonuniform nonequilibrium charge-carrier density distribution over the width of the stripe.

Fast tuning of 3.3 μm InAsSb/InAsSbP diode lasers due to nonlinear optical effects

Abstract InAsSb/InAsSbP double heterostructure diode lasers for the spectral range of 3.3 μm grown by liquid phase epitaxy have been investigated. Emission spectra, far-field patterns and wavelength tuning versus current have been studied in the wide current range from threshold value I th up to 3 I th , at the temperature of liquid nitrogen. Controlled by current wavelength tuning in single-mode lasing has been obtained both towards the shorter wavelengths (up to 4.56 cm −1 ) and towards the longer wavelengths (up to 0.9 cm −1 ) at the temperature T =77 K. Comparison of the emission properties of the lasers, driven by different types of current (short pulse current, sawtooth pulse current and in quasi cw regime) showed the same quantum-mechanical nature of current tuning. The theoretical model of this nonlinear optical phenomenon is proposed. The estimated times of current tuning defined mainly by the photon lifetime in the cavity are about 10 −9 –10 −12 s.

Spatial distribution of the radiation in the far zone of InAsSb/InAsSbP mesastrip lasers as a function of current

The far-zone directional pattern of diode mesastrip lasers with a 10 µm wide strip has been investigated as a function of the current. The directional pattern in the plane of the p-n junction contains one longitudinal mode, whose width depends on the current. It is shown by comparing the theoretically computed and experimentally measured spatial modes that this dependence is determined by the variation of the light flux intensity and the free-carrier density distributions over the strip width as a function of the current. In the case when the distributions are close to uniform the maximum narrow spatial longitudinal mode and a unimodal radiation spectrum are observed.

Tunable 3.3 μm InAsSb/InAsSbP diode lasers: a new concept of fast lasing due to nonlinear optical effects

InAsSb/InAsSbP double heterostructure diode lasers for the spectral range of 3.3 μm grown by liquid phase epitaxy have been investigated. Emission spectra, far–field patterns and wavelength tuning versus current have been studied in the wide current range from threshold value Ith up to 3Ith at the temperature of liquid nitrogen. Controlled by current, wavelength tuning in single–mode lasing has been obtained both towards the shorter wavelengths (up to 4.56 cm−1) and towards the longer wavelengths (up to 0.9 cm−1) at the temperature T = 77 K. Comparison of the emission properties of the lasers, driven by different types of current (short pulse current, sawtooth pulse current and in quasi–continuous–wave (CW) regime) showed the same quantum–mechanical nature of current tuning. The theoretical model of this nonlinear optical phenomenon is proposed. The estimated times of current tuning defined mainly by the photon lifetime in the cavity are ca. 10−9 to 10−12 s.