We present an optical spectroscopic study of InGaAs/AlInAs active region of quantum cascade lasers grown by low pressure metal organic vapor phase epitaxy combined with subwavelength gratings fabricated by reactive ion etching. Fourier-transformed photoluminescence measurements were used to compare the emission properties of structures before and after processing the gratings. Our results demonstrate a significant increase of the photoluminescence intensity related to intersubband transitions in the mid-infrared, which is attributed to coupling with the grating modes via so called photonic Fano resonances. Our findings demonstrate a promising method for enhancing the emission in optoelectronic devices operating in a broad range of application-relevant infrared.
Interband cascade lasers (ICLs) are highly efficient semiconductor lasers operating in the mid-infrared range. Their cascade structure of multiple quantum wells enables continuous operation at room temperature with low threshold current. This study explores the impact of tensile and compressive strain on W-QWs' electronic structure and carrier dynamics. Using transient absorption measurements on specific material structures, researchers investigated carrier lifetimes and fundamental transitions. Photoreflectance and photoluminescence measurements were also employed to study band structure and optical properties. The findings provide insights into optimizing ICL performance, improving their performance in application for gas sensing, spectroscopy, medical diagnostics, and communication.
The design of transparent conductive electrodes (TCEs) for optoelectronic devices requires a trade-off between high conductivity or transmittivity, limiting their efficiency. This paper demonstrates a novel approach to fabricating TCEs: a monolithic GaAs high contrast grating integrated with metal (metalMHCG). The technology and influence of fabricated different configurations of metalMHCG on the optical parameters will be shown. We will demonstrate above 90% absolute transmittiance of unpolarized light, resulting in 130% transmittance relative to plain GaAs substrate. Despite record high transmittance, the sheet resistance of the metalMHCG is several times lower than any other TCE, ranging from 0.5 to 1 OhmSq−1.
Monolithic subwavelength gratings integrated with metal (metalMHCG) enable nearly total transmission of light and can be fabricated with common semiconductor materials, however, they require a very high-aspect ratio between height and period of the metalMHCG stripes which is technologically challenging. This study aims the optimization of metalMHCG fabrication procedure by plasma etching taking into account the influence of process gas flow, their composition, pressure, power, and temperature on the wall shape of metaMHCG, etch rate, and etch selectivity. In the result, metalMHCG with high-aspect ratio and dimensions enabling nearly total transmission are fabricated.
Modern optical gas detection systems utilize the technique of tunable laser absorption spectroscopy for different applications in science, manufacture, or medicine. Superlattice structures composed of semiconductors from the 6.1 Å family enable type-II band alignments and have the potential to exceed state of the art figure of merits of widely used infrared detectors. In this study, InAs/GaSb and InAs/InAsSb type-II superlattices were grown using molecular beam epitaxy and characterized using Fourier-transform infrared spectroscopy and pump-probe transient absorption technique. Photoluminescence spectra were obtained for all samples in 10 to 300K temperature range and then complemented with photoreflectance measurements for characteristic temperatures to increase the sensitivity of the measurement for less optically active transitions. In addition, pump-probe measurements were performed to investigate the dynamics of carrier relaxation and recombination processes in proximity of transition energies observed in previous experiments.
We present result of optical studies on InAs/GaIn(As)Sb/InAs type II quantum wells predicted for the active region in interband cascade lasers, and further for laser-based gas sensors operating at room temperature in a broad wavelength range of mid infrared. Using photoreflectance spectroscopy supported by electronic structure calculations we determine the oscillator strength of the fundamental optical transition in structures with GaIn(As)Sb material of various compositions hole confinement layer. We show that incorporation of arsenic into this layer can affect several crucial properties significantly like transition wavelength and its probability, but also the structural material quality affecting the radiative efficiency. Also, by using photoluminescence we investigate one of the crucial parameters for the performance of interband cascade lasers, the spectral emission width of type II quantum wells constituting the laser active region.
There are reviewed the optical properties of two kind of active regions of mid infrared laser devices both grown on GaSb
substrates: GaInAsSb/AlGaInAsSb type I QWs for laser diodes and InAs/GaInAsSb type II QWs for interband cascade
lasers. There are presented their crucial optical properties and the related current challenges with respect to the device
performances. This covers such issues as spectral tenability of the emission via the structure parameters, the band gap
discontinuities, carrier loss mechanisms and oscillator strengths. For that, spectroscopic techniques have been used
(photoluminescence and its temperature dependence, and photoreflectance) and combined with the energy level
calculations based on effective mass approximation and kp theory. Eventually, the potential for further material
optimization and prospects for the improved device performances are also discussed.
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