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The scintillation response of Lu0.7Y0.3AP:Ce and Bi4Ge3O12 scintillation crystals have been compared using photomultiplier tube readout for photon energies ranging from 22.1 to 1274.5 keV. Lu0.7Y0.3AP:Ce showed a light yield non-proportionality of about 20% upon lowering energy from 1,274.5 to 22.1 keV, which is better than that of about 39% obtained for Bi4Ge3O12. Lu0.7Y0.3AP:Ce showed the light yield of 13,400 ph/MeV and energy resolution of about 8 % for 662 keV gamma rays from a 137Cs source. The photofraction of Bi4Ge3O12 is better than that of Lu0.7Y0.3AP:Ce. The intrinsic resolution of the crystals versus energy of gamma rays has been determined after correcting the measured energy resolution for photomultiplier tube statistics.

High temperature phase transition of 3-BaB2O4 (BBO) and K3Li12XNb5O15+2X (KLN) crystals are studied in detail by using high temperature Raman scattering. The temperature increasing of the crystals due to the increasing ofthe incident laser power during the frequency doubling process and the influence on the structure ofthe crystals are analyzed. It is the first time that the relationship between the phase transition and the frequency doubling is studied by high temperature Raman spectra. The opinion of phase transition having effect on frequency doubling is given out.Key words: Phase transition, Frequency doubling, High temperature Raman scattering. 1. INTRODUCTIONNonlinear frequency conversion is the most popular method to obtain short wavelength laser and frequency doubling is the simplest and the most convenient one. How to increase the efficiency of frequency doubling is aninteresting problem. To increase the incident power is the most direct method. However it is often observed thatwhen the incident power was increased to a certain degree, the efficiency of frequency doubling was no longerincreased. This phenomenon occurred in the experiment ofthe frequency doubling of KLN.Usually there are different phases in a crystal, we think there is phase transition in the crystal and for a nonlinearcrystal there is a certain phase which has frequency doubling effect. When the condition such as the temperature

This paper reports the experimental results on using Langmuir—Blodgett (LB) films as spacer layers between molecules and metal surface to study electromagnetic enhancement mechanisms of Surface Enhanced Raman Scattering (SERS), and to measure the change of SERS intensity with spacer layer thickness. In pyridine + KCL/LB films/Ag films configuration, the experimental results indicate SERS effect exists when the spacer layer thickness is 5 nm, and eventually it becomes unobservable with 15 nm thickness. The experiments supported the idea that the enhancement arises from an electromagnetic mechanism

Preparation of diamondlike carbon films (DLC) from various kinds of organic Langmuir- Blodgett (LB) films by laser light irradiation is reported. The properties of DLC films is discussed. Using surface enhanced Raman scattering techniques, DLC films were analyzed during formation. These films are expected to be very promising for various applications.

We report synchronously mode-locked subpicosecond and continuous-wave color-center laser operation in the 1.8-2.4-microm wavelength range. For active materials we use (F(2)(+))(H) centers in KBr:O(2)(-) and (F(2)(+))(AH) centers in KBr:Na(+):O(2)(-) crystals. When the lasers are pumped with a continuous-wave or mode-locked NaCI (F(2)(+))(H)-center laser in a cascaded configuration, laser operation is obtained over the combined tuning range of 1.8-2.4 microm, with output powers as high as 150 mW. When synchronously mode locked with ~5-ps pump pulses, both KBr lasers yield typically ~1-ps pulse widths over the entire tuning range. Pulses as short as ~400 fs could be obtained at the expense of higher noise levels.