The integrated space-air-ground-sea communication network has attracted increasing attention in recent years. Among its challenges, across air-sea medium communication remains a critical bottleneck due to its narrow bandwidth and severe attenuation. In this study, we investigate across-medium detection of acoustic-induced surface waves excited by encoded and modulated underwater acoustic signals, leveraging the characteristics of both underwater acoustic and millimeter-wave channels. Binary information carried by acoustic signals is used to generate surface waves at the water-air interface, which are directly detected in the air via millimeter-wave radar. After filtering under conditions of strong background noise and multi-source acoustic interference, the original acoustic information is accurately extracted. Experimental validation and simulation results demonstrate that the amplitude of 2FSK-modulated acoustic-induced surface waves detected across the air-sea interface ranges from 0.8522 μm to 1.0758 μm, with a bit error rate (BER) of 0. Out-of-band signal amplitudes are suppressed to 0.239 μm. Under identical symbol durations, the multi-channel scheme proportionally increases the across-medium communication capacity and data rate. In complex maritime noise environments, comparison of single-channel, dual-channel, and four-channel 2FSK schemes shows that even when the transmission rate is increased to 200 bps using four channels, millimeter-wave radar can still reliably detect the acoustic-induced surface waves with a BER below 3.2%. This study enables direct airborne detection and high-accuracy decoding of binary information encoded in underwater acoustic signals under complex sea conditions, demonstrating significant potential for practical implementation in high-speed uplink communication systems across the air-sea interface.

Wireless power transfer (WPT) via resonant laser beam from a spatially distributed laser resonator not only benefits the instinct safety but also has important potential of adaptive operation without positioning and aiming when retroreflectors are used to enable the alignment-free operation of the laser. Despite the intense theoretical modeling and experimental efforts with different laser schemes, the adaptive resonant beam WPT across large dynamic range, including both working distance and Field of View (FoV), has never been demonstrated, due to the absence of true alignment-free laser. In this work, we summarized the requirements on the dynamic range and discussed the optimization criteria of dynamic range and laser safety, including the telescope in the laser resonator, the resonator stability, coupled-resonator scheme, and influences of the optical aberrations. The analysis indicated that loss induced by optical aberrations is the main issue limits the dynamic range. In the experiment, alignment-free laser with large dynamic range for WPT application was demonstrated with improved resonator design and optical design to compensate the aberrations. Efficient multiwatt optical output was obtained across a working distance of 1–5 m, a receiver FoV of ±30°, and a transmitter FoV of 4.6°; and over 1.3-W electrical output was obtained via an InGaAs photovoltaic cell, with dc–dc WPT efficiency being 4%. Our work proved the feasibility of large-dynamic-range alignment-free laser with distributed resonator, which paves the way for practical resonant beam charging and communication applications based on it for the Internet of Things devices.