The diffusion reflection and depolarization of material surfaces is closely relevant to the physical properties of materials. To investigate the connection between BRDF (binomial reflection distribution function) and depolarized capability of the typical surfaces (e.g., aluminium, epoxy, and F4 board), a multi-angular measurement device is established to quantify these two parameters. With an incident laser beanm of 650 nm, a series of incident and detector view angles is measured and the results show the significant variance in the parameters for different targets. A coincidence is proved between the evolution of the two parameters, which is also valuable in modeling pBRDF (polarized BRDF).
Thermal effect becomes more prominent in the laser gain medium, to overcome this problem, the forced convective heat transfer with reliability and durability is widely used. The hydro-structures of dimensions of the flow channel affect the thermal performance immediately and efficiently. In this paper, with proposed cooling configuration based on longitudinal forced convective heat transfer, the factors of flow rate, state of flow field and surface roughness are investigated. The results reveal that fully developed flow state, higher flow rate and rougher surface lead to a better cooling capability. In the simulation results with 30 L/min flow rate, the calculated averaged convective heat transfer coefficient is as high as 10<sup>4</sup> W/m<sup>2 </sup>·K, and with slightly fluctuations in fully developed flow period.
The forced convective heat transfer with the advantages of reliability and durability is widely used in cooling the laser gain medium. However, a flow direction induced temperature gradient always appears. In this paper, a novel cooling configuration based on longitudinal forced convective heat transfer is presented. In comparison with two different types of configurations, it shows a more efficient heat transfer and more homogeneous temperature distribution. The investigation of the flow rate reveals that the higher flow rate the better cooling performance. Furthermore, the simulation results with 20 L/min flow rate shows an adequate temperature level and temperature homogeneity which keeps a lower hydrostatic pressure in the flow path.
A new pump-shaping scheme for a LD face-pumped Nd:YAG slab laser amplifier is proposed, aiming to achieve uniform pump distributions. Plano-concave cylindrical mirror arrays are used to homogenize the pump distributions in the LD slow axes, and meanwhile optical-waveguide structures are used for the LD fast axes. Simulations based on ray tracing method indicate that the scheme effectively realizes uniform pump intensity distributions. The fluorescence distributions and small signal gains at different locations both verify the pump uniformity reaches higher than 90%.
The laser performance and thermal analysis of Nd:KGW laser continuously pumped by 808 nm and 877 nm are comparatively investigated. Output power of 670 mW and 1587 mW, with nearly TEM<sub>00</sub> mode, are achieved respectively at 808 nm pump and 877 nm pump. Meanwhile, a high-power passively Q-switched Nd:KGW/Cr<sup>4+</sup>:YAG laser pumped at 877 nm is demonstrated. An average output power of 1495 mW is obtained at pump power of 5.22 W while the laser is operating at repetition of 53.17 kHz. We demonstrate that 877 nm diode laser is a more potential pump source for Nd:KGW lasers.