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 104 W/m2 ·K, and with slightly fluctuations in fully developed flow period.
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).
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.