The effects of working pressure on the properties of 355nm Al<sub>2</sub>O<sub>3</sub>/MgF<sub>2</sub> HR coatings were investigated. A series of
samples were deposited by electron beam evaporation using the same deposition process at different working pressure.
Transmittance of the HR coatings was measured by Lambda 900 spectrometer. Structure of the samples had been
characterized by X-ray diffraction (XRD).The stress was measured by viewing the substrate deformation before and after
coatings deposition using an optical interferometer, the stress results range from 223MPa to 315MPa. Laser-induced
damage threshold (LIDT) was measured by a 351 nm Nd:YAG laser with a pulse width of 7 ns, the LIDT results range
from 2.69 J/cm<sup>2</sup> to 11.03 J/cm<sup>2</sup> with the working pressure changing. It was found that working pressure has important
effects on the absorption, stress and LIDT of 355nm Al<sub>2</sub>O<sub>3</sub>/MgF<sub>2</sub> HR coatings. (351nm, 7ns).The working pressure was
no clear effect on the crystalline structure of the HR coatings.
A new method for side-pumping double-cladding fiber was researched. A quartz column of 3mm length was cut away from D-shape double-cladding fiber which has a transverse sectional dimension of 350μm×400μm. Then the column-fiber coupler was fabricated by gluing the column onto the side of inner cladding . The pumping light was coupled into the inner cladding from the end of the D-shape quartz column. When the output power was 1.3W from the forward end of the coupler, the optimum efficiency is 85%. This method can be suitable for pumping the fiber laser and amplifier of several watts output power.