Fig. 1. Schematic diagrams of structure of grating interferometric microphone. (a) Spatial layout; (b) 3-D image

Fig. 2. Two processes of optical path analysis of grating interferometer. (a) Reflection diffraction; (b) transmission diffraction

Fig. 3. Relationship between PD position design and VCSEL divergence angle. (a) Relationship between PD region and VCSEL divergence angle; (b) relationship between optimal placement coordinate of PD and divergence angle of VCSEL

Fig. 4. Curve of normalized light intensity of integrated grating interferometric microphone as a function of wavelength of VCSEL

Fig. 5. Performance simulation of grating interferometric integrated microphone. (a) Simulated frequency-domain response at 400 Hz for grating interferometric integrated microphone operating at point B shown in Fig. 4 (inset: corresponding time-domain response); (b) FF and SH amplitudes of grating interferometric integrated microphone response at 400 Hz as functions of operating wavelength

Fig. 6. Sample photo of diaphragm-grating double-layer structure

Fig. 7. Manufacturing process of grating interferometric integrated microphone. (a) Mounting and wire bonding of optoelectronic devices; (b) schematic diagram of assembly of microphone

Fig. 8. Physical photos of integrated device. (a) Microscopic photograph of integrated optoelectronic module; (b) physical picture of grating interferometric integrated microphone

Fig. 9. Schematic diagram of acoustic test experimental setup

Fig. 10. Results of operating point determination test. (a) VCSEL emission wavelength varies with current; (b) VCSEL emission power varies with current; (c) DC component output data of grating interferometric integrated microphone under different VCSEL driving currents; (d) FF component amplitude data of grating interferometric integrated microphone under different VCSEL driving currents

Fig. 11. Temporal responses of integrated microphone to acoustic signals with different frequencies and corresponding frequency-domain results obtained by Fourier transform processing. (a)(g) 50 Hz; (b)(h) 60 Hz; (c)(i) 70 Hz; (d)(j) 80 Hz; (e)(k) 90 Hz; (f)(l) 100 Hz

Fig. 12. Microphone frequency response test results. (a) Frequency response curve; (b) frequency response test points in low frequency region