Study on time-frequency domain characteristics and cross-media communication of laser acoustic signals based on optical breakdown mechanism

Abstract Cross-media communication is a hot research issue at present. The use of sound waves generated by laser induced sound mechanism for cross-media communication is a new topic proposed in recent years. It is of great significance to study the characteristics of laser acoustic signal and the feasibility study for cross-media detection. The time-frequency characteristics and directivity of the laser induced sound signal are studied on the self-built experimental platform. The results show that the pulse duration of the laser acoustic signal is about 2 × 10 −4 s, and the peak frequency is about 14.9 ± 0.75 kHz. And the signal strength perpendicular to the water surface is the weakest, so it has a good horizontal distance transmission ability. This paper verifies the detection system of trans-air-sea interface communication and trans-air-sea interface communication based on laser sound and conducts the communication experiment of laser acoustic signal. By modulating laser energy, the underwater acoustic signal is modulated in time domain, and the signal communication with 0-bit error rate of 8 bps within the meter is realized. The detection threshold of acoustic signal is calculated to be 44.9 dB re 1μpa after horizontal transmission of 1 km. The analysis and simulation of water surface micro-motion based on laser induced sound are carried out. The results show that the wave crest of water surface generated by laser acoustic signal through underwater reflection reaches the order of micron and can be detected by radar. The surface wave intensity is little affected by the depth of detection, so it could work in deep water. This study provides a certain experimental and theoretical basis for laser communication across the air and sea interface.