Terahertz modulator based on silicon-based microstructure on SOI, system and method

Abstract

The invention provides a Terahertz modulator based on a silicon-based microstructure on SOI, a manufacturing method and a modulation system. The Terahertz modulator successively comprises an Al2O3 substrate of a bottom layer, a SiO2 isolation layer, the silicon-based microstructures, and an Al2O3 passivation layer from bottom to top. The silicon-based microstructures are periodically arranged on the SiO2 isolation layer. Each silicon-based microstructure comprises a two-layer square Si-based step structure. The modulation system comprises a semiconductor laser, a laser modulator, the Terahertzmodulator, a Terahertz radiation source, and a Terahertz detector. In the invention, a reflectivity which is lower than 22% is achieved for a Terahertz wave of 0.4 THz to 0.85 THz and a minimum of 18% can be reached at 0.82 THz so that the reflectivity of a modulation device to the Terahertz wave can be significantly reduced and a utilization rate of the Terahertz wave is improved. A 64.5% modulation depth can be achieved under 808 nm laser radiation with 1200 mw power. Compared with a traditional silicon-based Terahertz modulator, a Terahertz imaging diffusion area can effectively increase aresolution and make the resolution reach above 21.9% in an imaging system.

Description

technical field [0001] The invention belongs to the field of terahertz technology and application, and relates to a terahertz amplitude modulation device in a terahertz imaging system and related fields, specifically a terahertz modulator based on a silicon-based microstructure on SOI and a preparation method thereof, and a terahertz modulator based on a silicon-based microstructure on SOI. Optically controlled terahertz modulation system with silicon-based microstructures. Background technique [0002] Terahertz refers to electromagnetic waves with a frequency ranging from 0.1 THz to 10 THz and a wavelength ranging from 0.03 mm to 3 mm. Compared with X-rays, terahertz waves can penetrate many non-polar materials and dielectric materials well, and can perform perspective imaging on opaque objects; the photon energy of terahertz radiation is only on the order of millielectronvolts (meV), less than The bond energy of various chemical bonds cannot cause various harmful ionizat...

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Problems solved by technology

[0004] There are three main problems in traditional optically controlled terahertz modulators. One is that the insertion loss of terahertz waves is too high, and the reflection of terahertz waves by traditional high-resistance silicon terahertz modulators is as high as 30%. The power is generally low, and the sensitivity of the terahertz detector is relatively low, which is a great loss. In 2014, Yan Peng, XiaoFei Zang and others prepared a terahertz detector based on a double-layer doped silicon grating structure. The perfect absorber excites the air-gap mode resonance through a grating array. After a series of parameter optimization, it finally achieves an absorption rate of 95% for terahertz waves, that is, only 5% for terahertz wave reflections, effectively solving the problem of terahertz waves. The insertion loss problem in wave transmission; the second is the modulation depth problem. The modulation depth of the current traditional silicon-based optically controlled terahertz amplitude modulator is relatively low, which is difficult to meet the requirements of the current terahertz imaging system; the third is the carrier diffusion The problem is that when the modulated laser light of the optically controlled terahertz modulator is incident on the surface of the modulator, the photogenerated carriers will diffuse around the modulated laser signal, resulting in a larger corresponding area, which is not conducive to the improvement of terahertz imaging accuracy.

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