Junjiang Hu

Experimental investigation of enhancing the subsurface damage threshold of Nd-doped phosphate glass

Experimental investigation was performed with a 1064-nm, 10-ns Nd:YAG laser to determine the effects of the surface hydrogen acid etching on laser damage, compared with damage of conventionally polished surface. The investigation was helpful for us to understand the negative effects of Nd-doped phosphate glass surface and subsurface damage (SSD) on laser induced damage threshold (LIDT). A set of samples was polished, and then chemically etched in a cool buffered 10%HF + 20%H2SO4 solution at different times. Another set of samples was ground and etched in the hot-buffered solution, and then polished. All the samples were irradiated with Nd: YAG laser and characterized by optical microscopy. Results of LIDT were obtained according to International standard ISO/DIS 11254-1.2. Chemical treatment can remove the contaminants in the polished re-deposition layer and the SSD for improving the laser damage resistance of Nd-doped phosphate glass surfaces. The method of using hot solution was more effective than that of using cool solution.

Effect of temperature on refractive index match of laser glass edge cladding

An Nd:glass disc requires an edge cladding to absorb the amplified spontaneous emission. The absorption is determined by reflections (R) from disc edges. R is primarily induced by the refractive index (n) mismatch. Thus, the temperature at the cladding interface increases due to absorption, and leads to the variation of n. In order to investigate the effect of temperature on the refractive index match, temperature coefficients (dn/dT) of the laser glass, adhesive polymer, and cladding glass are measured. The effect of temperature on the refractive index match is discussed. Results show that the indices match below 40°C.

Investigation on the temperature rise and thermal stress of edge-cladding

Absorption of edge-cladding Cu-glass for the strong amplified spontaneous emission of Nd-glass disk will produce a large rise for the temperature and thermal stress near the cladding interface between Cu-glass and Nd-glass. According to the calculation for amplified spontaneous emission of Nd-glass and thermal stress along the thickness of Cu-glass, which is produced in our lab, the relations among temperature rise, thermal stress, CuO doping concentration and thickness of cladding Cu-glass, are discussed in detail. If using 0.10% CuO doping instead of 1%, which was used in the previous time, the maximum temperature will decrease from 46K to 13K and the thermal stress will decrease from 4.0 MPa to 0.8 MPa. Our edges cladding experimental results, obtained by the low CuO concentration edge cladding glass, are consistent with the inferences and validated in the SG series laser systems.

Improvement for the surface damage resistance of Nd-doped phosphate glass

By determining LIDT, a few experiments, such as poshishing techinique, wet etching, which could improve the surface damage resistance of Neodymium-doped phosphate, were done and analyzed.