Nd³⁺-doped Calcium Fluoride Disordered Crystals Laser

Recently, the Nd-doped disordered crystals have attracted much attention because of their excellent spectral and thermal properties. Inhomogenerity of the disorderd crystal results in broader absorption and emission spectra, which is attractive for ultrashort pulse generation. Rare-earth?Y/La/Sc?, Nd-codoped CaF₂ crystal has the advantage of avoiding clustering effect which is deteriorating for lasing. As a result, it can be used for effective laser generation. In this theses, we studied passive mode-locking of Nd,Y:CaF₂ laser and investigated the laser properties of Nd,La:CaF₂ and Nd,Sc:CaF₂ lasers. The main research works and results are summarized as follows:?1? We studied LD pumped passively mode-locked Nd,Y:CaF₂ laser. With co-doping of 0.5 at.%Nd³⁺ and 10 at.% Y³⁺:CaF₂, We obtained 340 m W CW laser under the pump power of 3.5 W and a 0.8% output coupler, corresponding to an optical-to-optical efficiency of 9.7%. The central wavelength was at 1063 nm. By using a SESAM to start and sustain the mode-locking, stable laser Spectral width of 6.5 nm at a repetition rate 92 MHz were realized. The maximum average output power was 150 m W under the pump power of 3.5 W. The Nd,Y:CaF₂ disordered crystal with excellent ultrafast laser performance will be a promising candidate as gain medium to support high power and large energy operation of the laser.?2? We report what we believe the first laser operations with the Nd,La:CaF₂ and Nd, Sc:CaF₂ disordered crystals pumped by a 790 nm laser diode. Absorption and continuous wave laser performances were studied with different La- and Sc-doping concentrations. Under 5 W pump power, 1.1 W and 0.64 W laser power was obtained with 0.5 at.% Nd³⁺, 5 at.% La³⁺:CaF₂ and 0.5 at.% Nd³⁺, 3 at.% Sc³⁺:CaF₂, respectively, corresponding to 23% and 12.8% slope efficiencies, respectively. The laser threshold for both crystals was as low as 10 m W. The results show that the new co-doped crystals are promising laser mediums for high power and high efficiency diode pumped solid-state lasers.?3? A system of measurements has been designed for pore uniformity of polymer film. PET /PC films with different aperture size and density have important applications in the fields of aerospace, chemistry and other fields. So, accurate measurement the uniformity of the thin films with different sizes and densities is base. In this paper, we use laser to irradiation the polymer film and measure the power in different positions, so that the uniformity of the film can be determined quantitatively. The results are more consistent with the actual situation and the experimental scheme can be used as a standard method for the uniformity of film hole uniformity.