Manijeh Razeghi

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An ultra-sensitive and selective quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor platform was demonstrated for detection of carbon monoxide (CO) and nitrous oxide (N2O). This sensor used a state-of-the art 4.61 μm high power, continuous wave (CW), distributed feedback quantum cascade laser (DFB-QCL) operating at 10°C as the excitation source. For(More)
The dielectric functions of InP, IIla.53 Gao.47 As, and 1110.75 Gao.2S Aso.s P 0.5 epitaxial layers have been measured using a polarization-modulation spectroscopic ellipsometer in the 1.5 to 5.3 eV region. The oxide removal procedure has been carefully checked by comparing spectroscopic ellipsometry and x-ray photoelectron spectroscopy measurements. These(More)
We report on the demonstration of high-performance p-i-n photodiodes based on type-II InAs/ GaSb superlattices with 50% cut-off wavelength lc516 mm operating at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices show a(More)
A heterogeneous quantum cascade laser, consisting of multiple stacks of discrete wavelength quantum cascade stages, emitting in 5.9-10.9 µm, wavelength range is reported. The broadband characteristics are demonstrated with a distributed-feedback laser array, emitting at fixed frequencies at room temperature, covering an emission range of ~760 cm(-1), which(More)
The quantum cascade laser (QCL) is an important laser source in the mid-infrared and terahertz frequency range. The past twenty years have witnessed its tremendous development in power, wall plug efficiency, frequency coverage and tunability, beam quality, as well as various applications based on QCL technology. Nowadays, QCLs can deliver high continuous(More)
Research into III-Nitride based avalanche photodiodes (APDs) is motivated by the need for high sensitivity ultraviolet (UV) detectors in numerous civilian and military applications. By designing III-Nitride photodetectors that utilize low-noise impact ionization high internal gain can be realized—GaN APDs operating in Geiger mode can achieve gains exceeding(More)
Yanbo Bai received his M.S. degree in Physics and Ph.D. degree in Electrical Engineering from Northwestern University in 2005 and 2011. He is currently a research assistant professor at Northwestern. Since 2005, he has been with the Center for Quantum Devices. His research holds the current performance records of mid-IR quantum cascade lasers (QCLs) in(More)
A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν~1-5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based(More)
Research into avalanche photodiodes (APDs) is motivated by the need for high sensitivity ultraviolet (UV) detectors in numerous civilian and military applications. By designing photodetectors to utilize low-noise impact ionization based gain, GaN APDs operating in Geiger mode can deliver gains exceeding 1×10 Thus with careful design, it becomes possible to(More)
M-plane GaN avalanche p-i-n photodiodes on low dislocation density freestanding m-plane GaN substrates were realized using metal-organic chemical vapor deposition. High quality homoepitaxial m-plane GaN layers were developed; the root-mean-square surface roughness was less than 1 Å and the full-width-at-half-maximum value of the x-ray rocking curve for(More)