Abstract-Basic phase-locking, noise, and modulation properties of optically mutual-injected terahertz quantum cascade lasers

Yuanyuan Li, Ning Yang, Yan Xie, Weidong Chu, Wei Zhang, Suqing Duan, and Jian Wang

Fig. 2 Time evolution of |EA|, |EB | (first column), the corresponding power spectral density (second column), and instantaneous frequency (third column) with different coupling strength κ and detuning frequency ΔΩ/2π. The coupling strength in the first three rows are set as κ = 9.87 × 10−3, which is the case of moderate coupling. (a)–(c) within the phase-locking regime, ΔΩ/2π = 0.5GHz, (d)–(f) out of the pahse-locking regime, ΔΩ/2π = 5GHz, (g)–(i) out of the pahse-locking regime, ΔΩ/2π = 0.55GHz. The fourth row is the case of strong coupling with κ = 0.247. (j)–(l) out of the pahse-locking regime, ΔΩ/2π = 0.2GHz. The effective injection current is 1.5Ith in all simulations.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-3-3146

The phase-locking, noise, and modulation properties of two face-to-face optically mutual-injected terahertz (THz) quantum cascade lasers (QCLs) are analyzed theoretically. In the phase-locking range, the two THz QCLs are in stationary states working at the same frequency. Outside the phase-locking range, the amplitude and the instantaneous frequency of the optical field oscillate with time, and the power spectrum shows a series of discrete peaks. For strong mutual injection, the optical field of the THz QCL array also exhibits oscillatory behavior. Coherent collapse or chaotic behavior is not observed within the range of the parameters used in this simulation. The spontaneous emission noise of phase-locked THz QCLs is higher than that of THz QCLs at free-running operation, and mutual injection may introduce additional modulation peaks in the noise spectrum. The modulation response of the mutual-injected THz QCLs to an individual modulation is investigated. It is found that the modulation bandwidth and the phase difference are significantly dependent on the modulation parameters. These results are helpful for further understanding the nonlinear dynamic behaviors of THz QCLs under optical injection and provide theoretical support for the development of THz QCL phase-locked arrays.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Four resonators based high sensitive terahertz metamaterial biosensor used for measuring concentration of protein

Yuanyuan Li, Xieyu Chen, Fangrong Hu, Dongxia Li, Huan Teng, Qi Rong, Wentao zhang, Jiaguang Han,  Huasheng Liang

http://iopscience.iop.org/article/10.1088/1361-6463/aaf7e9

A terahertz (THz) metamaterial biosensor based on four identical resonators is experimentally demonstrated, and high sensitivity is achieved by exciting four synchronous LC oscillations in a unit cell. The effect of geometries on the resonance frequency of the sensor is investigated using finite integration time domain (FIDT) method, and the simulated sensitivity is 85 GHz per refractive index unit (RIU). The biosensor sample is fabricated using a surface micromachining process and characterized by a THz time domain spectroscopy (TDS) system combined with bovine serum albumin (BSA) solution as anelyte. The experimental results indicate that the resonance frequency shows distinct redshift when increases the concentration of BSA solution. When the concentration is high up to 765μmol/L, the frequency shift reaches 50 GHz, and the measurable minimum concentration is low to 1.5μmol/L. The biosensor is small in shape, wide in measurable range, convenient in operation and rapid in detection, which is of great significance for rapid concentration measurement, biomolecules detection and disease diagnosis.

Abstract-Metamaterials-based terahertz sensor for quick diagnosis of early lung cancer

Xin Xu, Yan Wu, Tangyan He, Yuanyuan Li, Fangrong Hu, Huasheng Liang, Chunxia Yang, and Hong Zhong

https://www.osapublishing.org/col/abstract.cfm?uri=col-15-11-111703&origin=search

We experimentally demonstrate a metamaterials (MMs)-based terahertz (THz) sensor to quickly distinguish the cancer tissues from normal tissues. The MMs-based THz sensor has two strong resonance absorption peaks at about 0.706 and 1.14 THz, respectively. When the sensor is covered with cancer tissues, the redshifts at about 0.706 and 1.14 THz are 31 and 19 GHz, respectively. However, if normal tissue is attached to the surface of the sensor, the corresponding redshifts are only 15 and 12 GHz, respectively. This study proposes a new method for quick diagnosis of early lung cancer and other cancers.

© 2017 Chinese Laser Press