arXiv subjects

R. A. Khabibullin

Publications and source records attributed to R. A. Khabibullin.

5 recordsLinked to original sources

arXiv2023

Phosphides-based terahertz quantum-cascade laser

Due to their high optical phonon energies GaInP/AlGaInP heterostructures are a promising active medium to solve the problem of creating compact semiconductor sources with an operating frequency range of 5.5-7 THz. In this work, the temperature dependences of gain and absorption at 6.8 THz have been calculated for a GaInP/AlGaInP-based quantum-cascade laser (QCL) with two quantum wells in the cascade and a metal-metal waveguide. We propose a laser structure that provides a mode gain of over 90 cm-1 with a maximum operating temperature of 104 K. The results of this study open the way to the development of a QCL for operation in a significant part of the GaAs phonon absorption band region, which is inaccessible for existing QCLs.

physics.optics↗

arXiv2021

8 x 8 Terahertz Photoconductive Antenna Array and Parallelized Signal Acquisition System for Fast Spatially Resolved Time Domain Spectroscopy

Terahertz (THz) technology is promising in several applications such as imaging, spectroscopy and communications. Among several methods in the generation and detection of THz waves, a THz time domain system (TDS) that is developed using photoconductive antennas (PCA) as emitter and detector presents several advantages such as simple alignment, low cost, high performance etc. In this work, we report the design, fabrication and characterization of a 2-D PCA array that is capable of detecting both the amplitude and phase of the THz pulse. The PCA array is fabricated using LT-GaAs and has 8 channels with 64 pixels (8x8). The infrared probe beam is steered and focused towards each pixel of the PCA array using a spatial light modulator (SLM). The measured photocurrent (amplitude and phase) from each channel is recorded separately and the frequencies up to 1.4 THz can be detected. Furthermore, the parameters such as directional time delay of the THz pulse, crosstalk between the channels etc., were characterized. Finally, we show that the proposed 2D PCA array design is flexible and can be used for accelerated THz spectral image acquisition.

physics.app-ph↗

arXiv2020

HgCdTe-based quantum cascade lasers operating in the GaAs phonon Reststrahlen band predicted by the balance equations method

HgCdTe-based quantum cascade lasers operating in the GaAs phonon Reststrahlen band with a target wavelength of 36 mkm are theoretically investigated using the balance equations method. The optimized active region designs, which are based on three and two quantum wells, exhibit a peak gain exceeding 100 cm(-1) at 150 K. We analyze the temperature dependences of the peak gain and predict the maximum operation temperatures of 170 K and 225 K for three- and two-well designs, respectively. At high temperatures (T > 120 K), the better temperature performance of the two-well design is associated with a larger spatial overlap of the weakly localized lasing wavefunctions as well as a higher population inversion.

physics.app-ph↗

arXiv2018

Strain-induced InGaAs/InAlAs superlattices for terahertz radiation

We study the influence of residual strain in InGaAs/InAlAs superlattice (SL) on the ultrafast photocarrier dynamics under femtosecond laser excitation. We propose and fabricate a novel-designed strained InGaAs/InAlAs SL which allows us to obtain an ultrashort photocarrier relaxation time of $τ\sim$ 1.5 ps without Be-doping of the InGaAs photoconductor. We assume two dominant mechanisms to be responsible for a sharp reduction of $τ$: photocarriers trapping by defect levels in InAlAs barriers and increased photocarriers scattering at InGaAs/InAlAs interface roughness due to residual strain in the SL. The THz time-domain spectroscopic measurements reveal an increase in both emitted THz waveform and spectrum amplitudes with an increase of residual strain in SL. The results might be of considerable interest for accommodating the needs of THz pulsed spectroscopy and imaging in fundamental and applied branches of THz science and technology.

cond-mat.mtrl-sci↗

arXiv2018

Shaping the spectrum of terahertz photoconductive antenna by frequency-dependent impedance modulation

In this paper, we report on an approach for shaping the spectra of THz pulse generation in photoconductive antennas (PCAs) by frequency-dependent impedance modulation. We introduce a theoretical model describing the THz pulse generation in PCAs and accounting for impedances of the photoconductor and of the antenna. In order to showcase an impact of frequency-dependent impedance modulation on the spectra of THz pulse generation, we applied this model to simulating broadband PCAs with log-spiral topology. Finally, we fabricated two different log-spiral PCAs and characterized them experimentally using the THz pulsed spectroscopy. The observed results demonstrate excellent agreement between the theoretical model and experiment, justifying a potential of shaping the spectra of THz pulse generation in PCA by modulation of frequency-dependent impedances. This approach makes possible optimizing the PCA performance and thus accommodating the needs of THz pulsed spectroscopy and imaging in fundamental and applied branches of THz science and technologies.

physics.app-ph↗