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Hydro-chemical erosion has a great effect on the micro-structure morphology and macroscopic mechanical properties of the rock mass. In this paper, direct shear test system was used to study the hydro-chemical effect on the shear strength characteristics of limestone fractures. Besides, morphology parameters of the fracture under different chemical solutions were also analyzed through three-dimensional laser scanning and electron microscope imaging. Experimental results showed that after hydro-chemical erosion, the profile mean square root deviation S q , the profile area ratio R s , the profile peak point density S pd increased, while the slope mean square root S dq decreased. Combined with scanning electron microscope (SEM) images, it is found that due to the hydro-chemical erosion, the roughness of limestone fracture surface, the discreteness of height distribution of the asperities and the JRC 2D values increased, but the slope of asperities decreased. There was a good exponential relation between the decrease percentage of limestone internal friction angle and soaking time, and a logarithmic relation between the decrease percentage of cohesion and soaking time. According to the gray correlation method, the influencing factors were ranked in descending order as follows: normal stress, soaking time and pH values. In addition, the JRC 2D value had a negative linear correlation with internal friction angle and cohesion of limestone fracture.

High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modern lidar and three-dimensional optical sensing systems, have recently attracted a lot of attention. In these types of systems, the time-of-flight (ToF) technique, based on the round-trip time of short optical pulses is usually adopted. Further enhancement of the ranging distance and depth resolution in these ToF driven systems by the incorporation of a VCSEL array with a high available power, high brightness (narrow divergence angle), and fast response time is highly desirable. However, a large number of light emission apertures (several hundreds) in the VCSEL array is usually necessary to raise the output power level to several watts. This leads to a large parasitic capacitance and the RC-limited bandwidth may become the dominant limiting factor of the speed of the high-power VCSEL array. In this work, Zn-diffusion and oxide-relief apertures are used to manipulate the optical modes and reduce the parasitic capacitance, respectively, in a unit device for a 940 nm VCSEL array. The demonstrated VCSEL array has a quasi-single-mode output, high available power (4 W; 1% duty cycle), narrow divergence angle ( ∼ 14 ∘ at 1 / e 2 ) under maximum output power, and a fast rise time ( <2018