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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.