The element–frequency acoustic intensity of a horizontal line array with a sufficient aperture exhibits interference striation patterns, which can be used for source range estimation without prior environmental information. Under multisource scenarios, the interference striations of the sources overlap with each other, leading to great difficulty in utilizing the information of striations. In this paper, the wavenumber filtering method is applied to each sensor of the horizontal line array to extract the surface-reflected–bottom-reflected modes and reconstruct the recognizable interference spectrogram for each source. Then, via beamforming along the striations, the source ranges can be estimated individually with little prior environmental information and without the long-time observation of moving sources. The required sensor spacing is analyzed, and the spatial filtering capabilities for a single source from different bearings and two sources for which azimuth angles are close to each other have also been investigated. The simulation results indicate that the proposed algorithm can estimate ranges of multiple sources within 25 km, with relative errors of less than 4%.

Based on the interference spectrogram in the element–frequency domain using the data measured by the horizontal linear array, the source range can be estimated through the striation-based beamforming (SBF) method and its variants. Estimation of the striation slope is the basis for these ranging methods. But in practical scenarios, the tonal interferences and other noise make it difficult to estimate the slope. In this paper, we proposed a two-dimensional low-pass filtering method after the two-dimensional discrete Fourier transform (2D-DFT) of the element–frequency domain spectrogram. The signals can be separated from the interference and noise using this filter. For the linear frequency-modulated signal without a known waveform, we also proposed an extraction and phase compensation method based on the time–frequency spectrogram, and the acoustic data obtained can be used for source ranging. The experimental results indicate that the methods proposed are feasible.

Cavity optomechanics in the photonic devices enables a light-matter interaction in the chip-scale systems via the optical force driven mechanical motion. In this paper, a pump-probe scheme consisting of dual optomechanical cavities is proposed for the first time, where one optical cavity driven by a high input power act as a pump channel and the other one is used as a probe channel to detect the dynamical motion of mechanical resonator. Moreover, modulation of the optical force in the pump channel is achieved to observe the amplification of mechanical motions. As the light input of the pump channel increases, the dynamical displacement of the mechanical resonator is theoretically actuated to 4.8 nm $/\!\sqrt {\text{Hz}} $ at the pump power of 0.75 mW. This all-optical amplification of mechanical motion based on the pump-probe scheme potentially paves the way for the development of optomechanical actuation and switch for the photonic integrated circuits.