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Start Over Author "Hu Qing" Journal applied physics letters
107 results on '"Hu Qing"'

2. We are 60!

Author

Borri, Paola, primary, Diez, Liza Herrera, additional, Hu, Qing, additional, Price, David L., additional, Zhao, Hongping, additional, and Cohen, Lesley F., additional

Published
2022
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3. 186 K Operation of Terahertz Quantum-Cascade Lasers Based on a Diagonal Design

Author

Kumar, Sushil, Hu, Qing, and Reno, John L

Subjects
Optics
Abstract

Resonant-phonon terahertz quantum-cascade lasers operating up to a heat-sink temperature of 186 K are demonstrated. This record temperature performance is achieved based on a diagonal design, with the objective to increase the upper-state lifetime and therefore the gain at elevated temperatures. The increased diagonality also lowers the operating current densities by limiting the flow of parasitic leakage current. Quantitatively, the diagonality is characterized by a radiative oscillator strength that is smaller by a factor of two from the least of any previously published designs. At the lasing frequency of 3.9 THz, 63 mW of peak optical power was measured at 5 K, and approximately 5 mW could still be detected at 180 K.

Published
2009

4. 1.9 THz Quantum-cascade Lasers with One-well Injector

Author

Kumar, Sushil, Williams, Benjamin S, Hu, Qing, and Reno, John L

Subjects
Lasers And Masers
Abstract

We report terahertz quantum-cascade lasers operating predominantly at 1.90 THz with side modes as low as 1.86 THz (lambda approx. equal to 161 micrometers, planck's constant omega approx. equal to 7.7 meV). This is the longest wavelength to date of any solid-state laser that operates without assistance of a magnetic field. Carriers are injected into the upper radiative state by using a single quantum-well injector, which resulted in a significant reduction of free-carrier losses. The laser operated up to a heat-sink temperature of 110 K in pulsed mode, 95 K in continuous wave (cw) mode, and the threshold current density at 5 K was approx. 140 A per square centimeters.

Published
2006
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7. A Low-noise Micromachined Millimeter-Wave Heterodyne Mixer using Nb Superconducting Tunnel Junctions

Author

DeLange, Gert, Jacobson, Brian R, and Hu, Qing

Subjects
Solid-State Physics
Abstract

A heterodyne mixer with a micromachined horn antenna and a superconductor-insulator-superconductor (SIS) tunnel junction as mixing element is tested in the W-band (75-115 GHz) frequency range. Micromachined integrated horn antennas consist of a dipole antenna suspended on a thin Si3N4 dielectric membrane inside a pyramidal cavity etched in silicon. The mixer performance is optimized by using a backing plane behind the dipole antenna to tune out the capacitance of the tunnel junction. The lowest receiver noise temperature of 30 +/- 3 K (without any correction) is measured at 106 GHz with a 3-dB bandwidth of 8 GHz. This sensitivity is comparable to the state-of-the-art waveguide and quasi-optical SIS receivers, showing the potential use of micromachined horn antennas in imaging arrays.

Published
1996
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8. Fabrication of high-quality superconductor-insulator-superconductor junctions on thin SiN membranes

Author

Garcia, Edouard, Jacobson, Brian R, and Hu, Qing

Subjects
Electronics And Electrical Engineering
Abstract

We have successfully fabricated high-quality and high-current density superconductor-insulator-superconductor (SIS) junctions on freestanding thin silicon nitride (SIN) membranes. These devices can be used in a novel millimeter-wave and THz receiver system which is made using micromachining. The SIS junctions with planar antennas were fabricated first on a silicon wafer covered with a SiN membrane, the Si wafer underneath was then etched away using an anisotropic KOH etchant. The current-voltage characteristics of the SIS junctions remained unchanged after the whole process, and the junctions and the membrane survived thermal cycling.

Published
1993
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