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Heavy fluorocarbon liquids were found to be an ideal medium for high-power stimulated Brillouin scattering experiments. Fluorinert FC-75 gives high reflectivity, near 98%, and excellent fidelity in phase conjugation of 14-J, 18-ns optical pulses. The complete removal of microparticle impurities was found to be essential for avoiding laser damage in a high-energy operation. A method of purification based on ultrafiltration has been developed.

As the first demonstration of Faraday effect in a TGG ceramics, its Verdet constant at 1053 nm is evaluated to be 36.4 rad/Tm at room temperature which is same as that of the single crystal. In addition, the temperature dependence of Verdet constant is obtained experimentally. At liquid helium temperature, it is 87 times greater than that at room temperature.

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The optical properties, Faraday effect and Verdet constant of ceramic terbium gallium garnet (TGG) have been measured at 1064 nm, and were found to be similar to those of single crystal TGG at room temperature. Observed optical characteristics, laser induced bulk-damage threshold and optical scattering properties of ceramic TGG were compared with those of single crystal TGG. Ceramic TGG is a promising Faraday material for high-average-power YAG lasers, Yb fiber lasers and high-peak power glass lasers for inertial fusion energy drivers.

Articles you may be interested inDesign of multipulse Thomson scattering diagnostic for SST-1 tokamak Rev. Sci. Instrum. 78, 043507 (2007); 10.1063/1.2724775 Detailed in situ laser calibration of the infrared imaging video bolometer for the JT-60U tokamak Rev. Sci. Instrum. 77, 10E515 (2006); 10.1063/1.2336471High-resolution ruby laser Thomson scattering diagnostic for the W7-AS stellarator Rev.A YAG laser Thomson scattering system has been developed to measure the time evolution of electron temperature (T e ) and density (n e ) profiles in the JT-60U. Presently this system provides T e and n e periodically every 100 ms ͑20 ms at the minimum͒ at 15 spatial channels. A six spectrum channel polychromator, which is a successive interference filter type, was designed to measure a wide T e range ͑20 eV-20 keV͒ by using five channels. The sixth channel is used for calibration by Rayleigh scattering. However, we also used the Rayleigh channel to measure T e and n e since the stray light level was very low. As a result, we were able to measure temperatures below 20 eV. The temperature of the silicon avalanche photodiode ͑APD͒ is stabilized by a Péltier element so that the gain is kept constant within Ϯ0.5%. The stable performance of the APD enables accurate T e and n e measurement. During plasma operation, the electron temperature is measured over a wide range from the low temperature plasmas in the runaway plasma current tail generated by a killer pellet to the high temperatures of high performance negative shear plasmas.

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Laser-induced-damage thresholds (LIDT's) with various types of vitreous silica at 1064, 532, 355, and 266 nm are investigated. At 1064 nm no difference in the LIDT was observed in any sample. At 1064-355 nm the wavelength dependence of the LIDT of synthetic fused silica (SFS) can be described well by the relation I(th) = 1.45lambda(0.43), where I(th) is the LIDT in J/cm2 and lambda is the wavelength in nanometers. At 266 nm, however, LIDT's were smaller than half of the calculated value from the relation above. This difference can be explained by the damage mechanism; at 266 nm two-photon absorption-induced defects lower the LIDT as in the case of KrF-excimer-laser-induced defects, whereas at longer wavelengths the two-photon process does not occur. LIDT's of fused quartz (FQ) at 532 and 355 nm and that of SFS containing approximately 1000 ppm of Cl and no OH at 355 nm were a little lower than those of the other SFS's. This lower LIDT may be related to the absorption of metallic impurities in FQ and dissolved Cl2 molecules in SFS. At 266 nm, on the other hand, LIDT's of FQ's were higher than those of most SFS's.