A half-ring resonator design of a 7-8 μm range quantum-cascade laser with different radius values has been proposed and implemented. For a quantum-cascade laser with a radius of a half-ring resonator of 191 μm, lasing with a radiation spectrum width of 474 nm (82 cm^-1) was demonstrated at low temperatures. The FSR in such lasers was determined by the whispering gallery modes typical for ring resonators. At room temperature, the width of the lasing spectrum was 190 nm (31 cm^–1), which is caused by a decrease in gain and a possible increase in internal losses with increasing temperature. An increase in the cavity radius up to 291 μm made it possible to realize room temperature lasing with whispering gallery modes with a radiation spectrum width of 249 nm (40 cm^-1), by reducing losses on the mirrors.

A cavity scheme based on a half-ring with different radii is proposed and fabricated for 7–8 μm quantum-cascade lasers. A quantum-cascade laser with a half-ring cavity radius of 191 μm demonstrated lasing with a spectral width of 474 nm (82 cm–1) at low temperatures. The free spectral range in these lasers was determined by the whispering gallery modes typical for ring cavities. The laser bandwidth at room temperature was 190 nm (31 cm–1), which may be related to an increase in the internal losses with increasing temperature. An increase in the cavity radius to 291 μm made it possible to achieve room-temperature lasing with whispering gallery modes and a bandwidth of 249 nm (40 cm–1) by reducing losses on the mirrors.

Spectral redistribution of the intensity of short- and long-wavelength emission components within gain bandwidth of a 7- to 8-μm quantum-cascade laser under the action of control voltage is demonstrated. As the voltage was increased from 10.5 to 18.2 V, the wavelength of maximum laser emission intensity shifted by approximately 200 nm. The maximum bandwidth of laser gain was about 300 nm (at a temperature of 80 K). The quantum-cascade laser heterostructure was grown by molecular beam epitaxy. The laser active region design was based on double-phonon depopulation of the lower level as implemented on In0.53Ga0.47As/In0.52Al0.48As heteropair of solid alloys lattice-matched with an InP substrate.

The heterostructure of a quantum-cascade laser based on In0.53Ga0.47As/Al0.48In0.52As heteropair lattice matched with the InP was grown by molecular beam epitaxy. InP layers was used to form the optical waveguide. Room temperature lasing in the spectral range of 8 μm in the standard ridge geometry of a Fabry-Perot cavity formed by cleaved facets with peak output optical power of 0.45 W was obtained.

AbstractSingle-mode lasing at room temperature in quantum-cascade lasers (QCLs) with arched cavity design has been demonstrated. The output optical power in single-mode lasing regime at ~7.7-μm lasing wavelength was above 6 mW with a side-mode suppression ratio of up to 25 dB. The QCL heterostructure for the arched cavities was grown by molecular-beam epitaxy (MBE) based on a heterojunction of In_0.53Ga_0.47As/Al_0.48In_0.52As solid alloys, lattice-matched with InP substrate, and InP layers performing the function of waveguide claddings.

The generation of radiation in 7-8 μm spectral range quantum-cascade lasers with the design of the active region based on a two-phonon resonance design is demonstrated. The wavelength of radiation tuning range under the action of the control voltage was 35 cm-1. The heterostructure of a quantum-cascade laser was grown by molecular beam epitaxy based on a In0.53Ga0.47As/Al0.48In0.52As heteropair, matched by lattice parameter with an InP substrate, and InP layers, which functioned as waveguide claddings.

Molecular beam epitaxy techniques were used to grow a quantum-cascade laser (QCL) heterostructure based on an In 0.53 Ga 0.47 As/Al 0.48 In 0.52 As heteropair lattice-matched with an InP substrate. InP layers were used to form an optical waveguide. The obtained QCL heterostructure ensured room-temperature lasing in the 8-μm wavelength range at a maximum output optical power of 0.45 W from one facet in a standard ridge geometry of the Fabry–Pérot cavities formed by cleaved facets.

An active region design based on the InGaAs/InGaAlAs superlattice for laser diodes of 1535-1565 nm spectral range was proposed and experimentally realized. It has been shown that the use of active region design based on superlattice allows increasing the modal gain at equal values of the pump current density in comparison with a common used active-region design based on a set of InGaAs quantum wells.

The results of experiments on the fabrication (by molecular-beam epitaxy) and investigation of the heterostructures of a two-frequency quantum-cascade laser produced on the basis of a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid solutions on an InP substrate are presented. The heterostructures contained quantum cascades emitting at a wavelength of 9.6 μm and cascades emitting at a wavelength of 7.6 μm. The high structural quality of the fabricated heterostructures is shown. The spontaneous emission and lasing spectra are investigated and the multimodal laser generation of stripe lasers at a wavelength of 7.6 μm is demonstrated.

Results of investigation of 1550 nm range stripe semiconductor lasers fabricated from heterostructures with different designs of the gain medium are presented. It is shown that the proposed designs of the gain medium allow obtaining the effective lasing at high level of total optical losses, comparable with the typical optical losses in the vertical-cavity surface-emitting lasers. The evaluation of modal gain in different types of the gain mediummade it possible to estimate the possible frequencies of the small-signal modulation of vertically emitting lasers and proposed the ways to increase them up to 20 GHz or more.

An active area based on InGaAs/InGaAlAs superlattice for laser diodes operating in the spectral range between 1535 and 1565 nm is proposed and realized practically. It is demonstrated that using a superlattice increases the mode gain at the same values of the pump-diode current density relative to a typical active-area design based on an array of InGaAs quantum wells.

Single-mode lasing at room temperature in quantum-cascade lasers (QCLs) with arched cavity design has been demonstrated. The output optical power in single-mode lasing regime at ~7.7-μm lasing wavelength was above 6 mW with a side-mode suppression ratio of up to 25 dB. The QCL heterostructure for the arched cavities was grown by molecular-beam epitaxy (MBE) based on a heterojunction of In 0.53 Ga 0.47 As/Al 0.48 In 0.52 As solid alloys, lattice-matched with InP substrate, and InP layers performing the function of waveguide claddings.

The results of the experimental study of stimulated emission of a quantum-cascade laser with a wavelength of 7.6 μm are presented in this paper. The dependence of the intensity of laser radiation on the duty cycle was obtained. The linearity of this dependence was maintained up to a duty cycle of 40%, thus achieving the quasi-continuous mode of operation of the quantum cascade laser at 110 K.

AbstractThe results of experiments on the fabrication (by molecular-beam epitaxy) and investigation of the heterostructures of a two-frequency quantum-cascade laser produced on the basis of a heteropair of In_0.53Ga_0.47As/Al_0.48In_0.52As solid solutions on an InP substrate are presented. The heterostructures contained quantum cascades emitting at a wavelength of 9.6 μm and cascades emitting at a wavelength of 7.6 μm. The high structural quality of the fabricated heterostructures is shown. The spontaneous emission and lasing spectra are investigated and the multimodal laser generation of stripe lasers at a wavelength of 7.6 μm is demonstrated.

This paper considers the influence of barrier doping on parameters of photoluminescence of 1550 nm range multi quantum well heterostructures grown by molecular beam epitaxy. The studied heterostructures consist of seven strained InGaAs quantum wells with delta p-doped InAlGaAs barriers. Photoluminescence studies show that p-doping increases the photoluminescence intensity of heterostructures at low pumping levels and decrease the changing of the width of photoluminescence spectra with change of pumping levels.

The paper demonstrates the generation of multistage quantum-cascade lasers (QCL) in the 7-8 mu m spectral range in the pulse generation mode. The active region structure we used is based on a two-phonon resonance scheme. The QCL heterostructure based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys was grown by molecular beam epitaxy and includes 50 identical stages. A waveguide geometry with top cladding with full top metallization (surface-plasmon quantum-cascade lasers) has been used. The developed QCLs have demonstrated multimodal generation in the 7-8 mu m spectral range in the pulse mode in the 78-250 K temperature range. The threshold current density for a 1.6 mm long laser and a 20 mu m ridge width amounted to similar to 2.8 kA/cm(2) at a temperature of 78 kappa. A temperature increase to 250 K causes a long-wave shift of the wavelength from 7.6 to 7.9 mu m and a j(th) increase to 5.0 kA/cm(2).

We present the results on growth, characterization and optical properties of quantum-cascade laser heterostructures grown by molecular-beam epitaxy. The double-phonon resonance design for forming of active region together with thick InP-based top cladding was used to increase the quantum-cascade laser performance. The results of electroluminescence studies of 4-cleaved samples are presented. The room temperature lasing at 8.0 um with threshold current density about 1.98 kA/cm2 was achieved.

A. V. Babichev, A. G. Gladyshev, E. S. Kolodeznyi, A. S. Kurochkin, G. S. Sokolovskii, V. E. Bougrov, L. Ya. Karachinsky, I. I. Novikov, V. V. Dudelev, V. N. Nevedomsky, S. O. Slipchenko, A. V. Lutetskiy, A. N. Sofronov, D.A. Firsov, L.E. Vorobjev, N. A. Pikhtin, A. Bousseksou, A. Yu. Egorov ITMO University, St. Petersburg, Russia, a.babichev@corp.ifmo.ru Connector Optics LLC, St. Petersburg, Russia Ioffe Institute, St. Petersburg, Russia Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia Center of Nanoscience and Nanotechnology (C2N), Universit ́e, Paris Sud and Paris-Saclay, Orsay cedex, France

AbstractThe photoluminescence of strained InGaAlAs/InGaAs/InP heterostructures with an active region consisting of nine In_0.74Ga_0.26As quantum wells and δ-doped In_0.53Al_0.20Ga_0.27As barrier layers grown by molecular beam epitaxy on an InP(100) substrate is investigated. Analysis of the photoluminescence spectra demonstrates that p -type doping leads to an increase in the photoluminescence efficiency at low excitation levels in comparison to a heterostructure with undoped barriers, and increasing the level of barrier doping to (1–2) × 10^12 cm^–2 results in the suppression of nonradiative recombination.