Temperature dependence of the threshold current density in semiconductor lasers (λ = 1050–1070 nm)

The temperature dependences of the threshold current density and threshold concentration in semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with an extended waveguide have been studied (wavelengths ?? = 1050?C1070). It is shown that the temperature dependence of the threshold current density in semiconductor lasers becomes markedly stronger at above-room temperatures, which is due to temperature-induced carrier delocalization into the waveguide layers of a laser heterostructure. It was found that the sharp decrease in the thermal stability of the threshold current density with increasing temperature correlates with the coincidence of the Fermi level with the conduction-band bottom of the waveguide layer in the laser heterostructure. It is experimentally demonstrated that an increase in the energy depth and number of quantum wells in the active region of a semiconductor laser improves the thermal stability of the threshold current density. It is demonstrated that the characteristic parameter T ₀ attains a value of 220 K in the temperature range from ?20 to +70°C.     

850-nm diode lasers based on AlGaAsP/GaAs heterostructures

Laser heterostructures with waveguides and emitter layers made of AlGaAs and AlGaAsP alloys are grown by hydride metal-organic vapor-phase epitaxy on a GaAs substrate and studied. It was shown that the heterostructure containing AlGaAsP layers has a large curvature radius in comparison with the structure consisting of AlGaAs layers. Ridge waveguide lasers with an aperture of 100 ??m are fabricated based on the AlGaAsP/GaAs laser heterostructure and studied. The internal optical loss of the lasers is 0.75 cm^?1; the characteristic parameter T ₀ = 140 K in the temperature range of 20?C70°C. The maximum optical output power per mirror reached 4.1 W; cw lasing was retained at a heat sink temperature of 120°C.     

High-power laser diodes with an emission wavelength of 835 nm on the basis of various types of heterostructures

Optical and electrical characteristics of different high-power multimode laser diodes with an emission wavelength of 835 nm are compared; the diodes were obtained on the basis of three systems of solid solutions: AlGaAS/GaAs, AlGaAs/GaAsP, and (Al)GaInP/GaInAsP. An output continuous optical power of 5 W is attained in lasers with a stripe width of 80 μm irrespective of the chosen material system. The highest optical power, 7 W, is attained in the lasers based on the (Al)GaInP/GaInAsP system.     

850-nm diode lasers with different ways of compensating for internal mechanical stresses in an AlGaAs:P/GaAs heterostructure

MOS hydride epitaxy is used to grow AlGaAs/GaAs heterostructures both without compensation and with compensation for internal mechanical stresses by the introduction of phosphorus into different layers of the heterostructure; this compensation affects the lattice parameter of the layer and, thus, influences the value of internal stresses in the entire laser hetetrostructure. Multimode mesastripe laser diodes (with an aperture of 100 μm) emitting at a wavelength of 850 nm are fabricated on the basis of the above structures; the properties of these diodes are studied. It is shown that the structures with compensated internal mechanical stresses exhibit a linear power-current characteristic if the pump currents do not exceed those corresponding to the maximum of the output power. Such structures with compensated internal mechanical stresses exhibit larger values for the characteristic temperatures T ₀ and T ₁ in comparison with structures with uncompensated internal mechanical stresses.     

Acoustoelectron interaction in quantum laser heterostructures

The effect of ultrasonic deformation on the polarization properties of semiconductor quantum-well laser radiation is experimentally and theoretically studied at room temperature. It is shown that the observed rotation of the polarization plane is caused by mixing of the light- and heavy-hole levels in the quantum well. Data on the splitting energy of these levels are obtained. The unique capability of the ultrasonic technique for obtaining data on the value and distribution of technological strains in the heterostructure is shown.     

Temperature dependence of the threshold current density and external differential quantum efficiency of semiconductor lasers (λ = 900–920 nm)

Semiconductors - The temperature dependences of the emission characteristics of semiconductor lasers based on asymmetric separate-confinement heterostructures with a broadened waveguide fabricated...     

Laser-diode bars based on AlGaAsP/GaAs heterostructures emitting at a wavelength of 850 nm

Two types of laser heterostructures, i.e., those without internal mechanical stress compensation, with AlGaAs-alloy emitter and waveguide layers (type 1), and laser heterostructures with stress compensation, with AlGaAsP emitter and waveguide layers (type 2) are grown by metal-organic chemical vapor deposition (MOCVD). Laser-diode bars 5 mm wide with a fill factor of 24%, emitting at a wavelength of 850 nm are fabricated. Their power parameters in the continuous-wave (cw) and pulsed lasing modes are studied. It is shown that type-2 laser diode bars exhibit better linearity of the light-current characteristics in the cw and pulsed lasing modes in comparison with laser diode bars based on the type-1 structure.     

High-power diode lasers (λ = 1.7–1.8 µm) based on asymmetric quantum-well separate-confinement InGaAsP/InP heterostructures

Advantages of the concept of high-powered semiconductor nanoheterostructure lasers for the spectral range 1700–1800 nm, grown by MOCVD in the InGaAsP/InP solid solution system, have been experimentally demonstrated. It has been found that using an expanded waveguide enables reduction to 2 cm^?1 of the internal optical loss in quantum-well asymmetric separate-confinement double InGaAsP/InP heterostructures emitting at a wavelength of 1.76 µm. The heterostructures developed have been used to create multimode lasers with a room-temperature CW output power of 2.5 W in an aperture of 100 µm. It is shown that use of highly stressed quantum-well InGaAs layers as the active region makes it possible to obtain characteristic temperatures T ₀ = 50–60 K.     

On the Fabrication and Study of Lattice-Matched Heterostructures for Quantum Cascade Lasers

Semiconductors - The fabrication and study of the characteristics of a lattice-matched quantum cascade laser structure on an indium-phosphide substrate, designed for a wavelength of ~4.8 μm...     

Switching between the mode-locking and Q-switching modes in two-section QW lasers upon a change in the absorber properties due to the Stark effect

The passive Q-switching and mode-locking modes are implemented in two-section lasers with three quantum wells. It is demonstrated that raising the reverse bias on the absorbing section changes its spectral and dynamic properties and, accordingly, leads to a change from the Q-switching mode to mode-locking. The pulse-repetition frequency in the mode-locking mode is 75 GHz, with the product of the pulse duration by the spectrum bandwidth being 0.49, which is close to the theoretical limit. It is shown that, in structures with three quantum wells, strong absorption at the lasing wavelength gives rise to a photocurrent across a section of the saturable absorber, which is sufficient for compensation of the applied bias.