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Owing to the unique features in intensity and phase structures, optical vortex lattices (OVLs) have attracted intensive attention and promoted various applications. However, the power scaling of OVLs always presents a critical challenge. Here we take advantage of the brightness enhancement of coherent beam combining (CBC) technology and propose an architecture for creating OVLs based on the CBC system. In the experiment, by utilizing the stochastic parallel gradient descent algorithm, the dynamic phase noises were compensated. The desired piston phase shifting of each element for tailoring the structured wavefront was implemented by the liquid crystal. When the system in a closed loop, hexagonal close-packed OVL consists of spatially distributed orbital angular momentum, beams can be generated in the far-field. This work is an important step toward future implementation of high-power structured light beams.

A highly sensitive quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a custom quartz tuning fork (QTF) with a small-gap of 200 μm was demonstrated. With the help of the finite element modeling (FEM) simulation software COMSOL, the change tendency of the QEPAS signal under the influence of the laser beam vertical position and the length of the micro-resonator (mR) were calculated theoretically. Water vapor (H2O) was selected as the target analyte. The experimental results agreed well with those of the simulation, which verified the correctness of the theoretical model. An 11-fold signal enhancement was achieved with the addition of an mR with an optimal length of 5 mm in comparison to the bare QTF. Finally, the H2O-QEPAS sensor, which was based on a small-gap QTF, achieved a minimum detection limit (MDL) of 1.3 ppm, indicating an improvement of the sensor performance when compared to the standard QTF that has a gap of 300 μm.

The effects of the jet engine turbulence on a Gaussian Schell-Model (GSM) beam array propagating in a jet engine plume are studied theoretically. The analytical expressions of the cross-spectral density (CSD) function, the spectral degree of coherence (DOC) and the mean-squared beam width for a GSM beam array propagating through a jet engine plume region are derived based on the extended Huyens-Fresnel integral. It is found that the profile of spectral density and the DOC of a GSM beam array gradually transfer to an elliptical shape as the propagation distance increases, and the elliptical degree becomes greater with increasing source coherence length. Besides, as the source coherence length decreases, the effect of the jet engine turbulence on the beam broadening is smaller and the profile of the DOC appears sidelobes at short distance. It is also found that the values of effective coherence width nearly remain the same for different values of source coherence length after propagating a certain distance. Furthermore, the effects of the number of beamlets on the beam width and effective coherence width are investigated in detail.

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