Abstract
By finite difference time domain (FDTD) simulation, we report on the optical field distribution within edge coupled terahertz quantum well photodetectors (THz QWPs) in detail. The coupling efficiency of THz QWP structures are studied from three aspects, including the electrode geometry, the position of the active region and the coupling angle. According to the simulation results, proper electrode geometry is suggested in different frequency region, and the optimal position of active region and coupling angle are presented. These results provide a useful guidance for the design and fabrication of the edge coupled THz QWP.
Highlights
Due to the rapid development of terahertz science and technology, terahertz quantum well photodetectors (THz QWPs) have attracted more and more attention nowadays because of some unique advantages such as fast intrinsic response speed, wide wavelength coverage and the availability of a mature material and processing.[1,2] Though assumed to be a natural extension of the traditional infrared (IR) QWPs to the THz frequency, the study on THz QWP is far from mature
To obtain a high coupling efficiency, the active region should be located at some certain positions, which will be discussed in detail
It is seen that the entire THz radiation range could be divided into three zones, the low frequency zone (1-6.7 THz), the medium frequency zone (6.7-9.8 THz) and the high frequency zone (9.8-12 THz)
Summary
Due to the rapid development of terahertz science and technology, terahertz quantum well photodetectors (THz QWPs) have attracted more and more attention nowadays because of some unique advantages such as fast intrinsic response speed, wide wavelength coverage and the availability of a mature material and processing.[1,2] Though assumed to be a natural extension of the traditional infrared (IR) QWPs to the THz frequency, the study on THz QWP is far from mature. K. Choi pointed out that the 45◦ coupling angle is not the best one.[9] To obtain better performance, realization of the optical field distribution is necessary in addition to the conventional optimization of the detector parameters. 45◦ edge coupled geometry is commonly employed to obtain a detector performance.[1] The realization of the actual optical field distribution inside an edge coupled THz QWP is essentially needed and important for device optimization. There are two electrode geometries (solid and ring) that is widely used in practical application of the edge coupled THz QWPs. So we first discuss the optical field distribution and coupling efficiency of two different electrode geometries in the THz range, which gives a guidance of the electrode geometry application for the edge coupled THz QWPs. we study the effect of the location of active region on the performance of THz QWPs and give the best location of the active region for THz QWPs operating at different peak frequencies. We investigate the effect of coupling angle and reveal the appropriate coupling angle at different frequency
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