Photo-acoustic (PA) signals induced by Kr F laser irradiations on to the optical thin layers have been measured to detect the small absorptions and the damage thresholds of dielectric coatings. Extremely low absorption with the extinction coefficient of 10_-4 is detectable for the single-layer coatings with optical thickness of 1.5 wavelength at 248nm. The pre-damage detections have been studied with the assistance of laser scattering damage detection techniques. Thechanges of the slope and the variation of the PA signals have been observed at the irradiation of Kr F laser of lower fluence compared with the damage thresholdsby microscopic measurements. The pre-damage thresholds detected by the PA signaldetection agreed well with the laser scattering method for low index fluoridecoatings. Typical features of the laser induced damages related to the linear absorption and the refractive index will be discussed about the coating materials forshort wavelength lasers.

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Firstly, we have observed microscopic hillocks on tapered prismatic surfaces of a KDP crystal which has grown in the solution with bacteria. The generation mechanism of hillocks was investigated.
Secondary, we have succeeded in the measurement of organic material from bacteria in the KDP crystal by using chromogeniclimulus test, of which sensitivity was 10^-2ppb.

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For the investigation of a possible mechanism causing the bio-effect of low energy laser beam, this paper describes the influences of the laser beam irradiationon protein conformation (spatial structure of a protein) relating to biological activation. Measurements of the myoglobin conformation are made by using the circular dichroism (CD) spectra, and the variation of the conformation is examined with respect to the irradiation time. The results show that the low energy laserbeam could promote the time fluctuation of the conformation content and might result in affecting the bio-effect.

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