过模矩形波导中硅芯片与基模亚毫米波的作用

Interaction of silicon sample with fundamental mode submillimeter wave in overmoded rectangular waveguide

模拟研究了过模矩形波导WR10中n型硅探测芯片对TE10模亚毫米波的响应。针对过模波导WR10中内置n型硅芯片的亚毫米波探测结构,推导了基模工作时的灵敏度表达式。采用三维电磁场时域有限差分方法,模拟计算了过模波导中300～400GHz频带的TE10模亚毫米波与硅芯片的相互作用,分析了探测结构中电压驻波比和芯片内平均电场随硅芯片参数变化的规律。结果表明,在相同的芯片参数下,过模探测结构并不影响电压驻波比和芯片内平均电场的大小,但两者随频率变化的波动程度增大。在300～400GHz工作频带内,优化得到了性能较优的过模探测结构,其电压驻波比不大于2.75(335～380GHz频带内不大于1.8),线性工作区的相对灵敏度约为0.127kW-1,频率响应的波动范围在±20.5%内,最大承受功率约为0.53kW,响应时间为100ps量级,满足亚毫米波大功率脉冲的直接探测需求。

Responses of n-Si detecting sample to TEl0 mode submillimeter wave in an overmoded rectangular waveguide are numerically investigated. Relative sensitivity under fundamental mode operation for the submillimeter wave detecting structure is derived. Using a three-dimensional electromagnetic finite-difference time-domain method, the interaction of the n-Si sample with submillimeter wave within 300-400 GHz in the overmoded waveguide is calculated, and the dependences of voltage standing wave ratio （VSWR） of the structure and average electric field strength in the sample on the parameters of n-Si detecting sample are ana- lyzed. Compared with the fundamental mode detecting structure with the same silicon sample, VSWR and average electric field strength in the sample change slightly in the overmoded detecting structure, while the fluctuations of their dependences on fre- quency increase. Selection of the structural parameters of the overmoded detecting structure is also studied. In working frequency range of 300-400 GHz, the optimized structure with VSWR less than 2.75 （no more than 1.8 within frequency range of 335-380 GHz） and response time of hundreds of picoseconds-level has a relative sensitivity around 0. 127 kW-a fluctuating within ＋ 20.5 and the maximum enduring power of about 0.53 kW. This detecting structure satisfies the demand of the direct detection of large power pulses at submillimeter wavelength.