Abstract-High-responsivity and polarization-discriminating terahertz photodetector based on plasmonic resonance

Applied Physics Letters

Yuanliao Zheng, Pingping Chen, Heming Yang, Jiayi Ding, Yuwei Zhou, Zhou Tang, Xiaohao Zhou, Zhifeng Li, Ning Li,  Xiaoshuang Chen, Wei Lu,

(a) The structure of the SPQWP device; (b) the schematic view of the periodic units for the SPQWP structure

https://aip.scitation.org/doi/abs/10.1063/1.5085813

In this paper, a high-responsivity terahertz quantum well photodetector based on plasmonic resonance is proposed and investigated theoretically and experimentally, and the polarization-discriminating detection of the device is demonstrated. With a one-dimensional metallic grating structure integrated on the top of the detector, a 6-fold enhancement of the peak responsivity about 0.82 A/W at 46 μm compared to that of the standard device has been achieved. The physical mechanism behind the enhanced responsivity can be attributed to the enhancement of the intersubband absorption resulting from the surface Plasmon polariton mode, which can be explored from the theoretical simulation results. The polarization extinction ratio of the plasmonic-enhanced device reaches 56, and the measured signal intensity at each polarization angle satisfies Malus' law. In addition to the above advantages, the structure is simple in fabrication and compatible with the preparation process of the focal plane array. The results open up an effective method for the application of surface plasmon in terahertz detection.

Abstract-Terahertz master-oscillator power-amplifier quantum cascade laser with a grating coupler of extremely low reflectivity

Huan Zhu, Haiqing Zhu, Fangfang Wang, Gaolei Chang, Chenren Yu, Quan Yan, Jianxin Chen, Lianhe Li, A. Giles Davies, Edmund H. Linfield, Zhou Tang, Pingping Chen, Wei Lu, Gangyi Xu, and Li He

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-2-1942

A terahertz master-oscillation power-amplifier quantum cascade laser (THz-MOPA-QCL) is demonstrated where a grating coupler is employed to efficiently extract the THz radiation. By maximizing the group velocity and eliminating the scattering of THz wave in the grating coupler, the residue reflectivity is reduced down to the order of 10−3. A buried DFB grating and a tapered preamplifier are proposed to improve the seed power and to reduce the gain saturation, respectively. The THz-MOPA-QCL exhibits single-mode emission, a single-lobed beam with a narrow divergence angle of 18° × 16°, and a pulsed output power of 136 mW at 20 K, which is 36 times that of a second-order DFB laser from the same material.

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