In-plane displacement sensing unit and method based on simplified optical nano-resonant cavity

Abstract

The invention relates to an in-plane displacement sensing unit and method based on a simplified optical nano-resonant cavity. The in-plane displacement sensing unit comprises a laser device, an optical isolator, a movable sub-wavelength silicon grating and a silver film covering the grating, a sub-wavelength silver film grating covering a silicon substrate, an air gap, the substrate and a light-splitting prism. On the basis of the resonance enhancement principle of the near-field optical cavity, the structural parameters and relative positions of a grating group are designed and thus the reflected light intensity emitted from the resonant cavity is extremely sensitive to the in-plane displacement of the movable sub-wavelength silicon grating, thereby realizing ultra-high sensitivity in-plane displacement measurement. According to the invention, the two groups of silver films are used for replacing two groups of optical gratings in the ordinary optical nano-resonant cavity and the wholesensor unit is made of a silicon wafer on a single insulating body, so that the processing difficulty is reduced substantially; on the basis of the optimized structural parameters, the sensor unit hathe higher light intensity displacement sensitivity by being compared with the existing resonant cavity scheme, so that the high-integration high-reliability high-precision in-plane displacement measurement is realized.

Description

technical field [0001] The invention belongs to the field of displacement sensing units, and in particular relates to an in-plane displacement sensing unit and method based on a simplified optical nano-resonator cavity. Background technique [0002] The measurement principle of high-precision optical displacement sensors is usually based on the volatility of light, that is, the interference and diffraction effects of optical signals are used for displacement measurement. However, the displacement measurement based on the fluctuation of light cannot break through the diffraction limit of light, and the measurement accuracy is limited by the wavelength of light. Although the displacement measurement accuracy can be improved to λ / 100 or even higher through electronic subdivision, modulation and demodulation, etc., the introduction of various subdivision methods will also increase the complexity of the system and the cost of the displacement sensor, and for the displacement meas...

AI Technical Summary

Problems solved by technology

However, existing near-field optical resonant structures are usually composed of multilayer nanostructures of various materials, generally including three or more materials, and contain suspended complex structures

This makes its processing extremely difficult and the yield rate is not high; in addition, it is difficult to achieve ultra-sensitive displacement measurement

[0004] For example, the optical nanoelectromechanical displacement sensor proposed by Dustin [KEELER B E N, BOGART G R, CARR DW. Laterally deformable optical NEMS grating transducers for inertia sensing applications; proceedings of the Nanofabrication: Technologies, Devices, and Applications, F, 2005[C].] by two A movable nano-grating, an air gap and a substrate, wherein the material of the movable nano-grating is amorphous diamond, and the substrate material is silicon dioxide and silicon nitride; another example is the grating group displacement sensor proposed by Wang Chen et al. [WANG C ,LU Q, BAI J, et al.Highly sensitive lateral deformable optical MEMS displacement sensor: anomalous diffraction studied by rigorous coupled-wave analysis[J].Appl Optics,2015,54(30):8935-43. And the Chinese patent number is CN201410636890 The patent "combined grating micro-displacement sensor and its method of measuring displacement"], also consists of two groups of movable sub-wavelength gratings, air gaps and substrates, the material of the movable grating is single crystal silicon, and the substrate material is silicon dioxide and Silicon nitride; although the displacement sensor of the subwavelength grating group proposed by Rogers is relatively simple in structure, because the scheme only uses two sets of subwavelength gratings to be equivalent to a normal diffraction grating, the light intensity displacement sensitivity is only 0.5% / nm, Far from meeting the needs of ultra-sensitive displacement measurement[ROGERS A A A, KEDIA S, SAMSON S, et al.Verification of evanescent coupling from subwavelength grating pairs[J].Applied Physics B-Lasers and Optics,2011,105(4):833- 7.]

It can be seen that the scheme based on the near-field optical resonator has a complex structure or low sensitivity, and because the near-field optical resonance enhancement is sensitive to structural parameters, the existing scheme is difficult to process, has extremely high requirements on materials, and has high cost and disadvantages. Disadvantages of low reliability

Images