Abstract

In the laser mode-locking technique, the higher harmonic acoustooptic modulators have been widely used. This method can use a thicker transducer to produce higher modulation frequency, which avoids the difficulty in thinning of the transducer. Especially, with the request of high modulation frequency for the pump laser, it is more difficult to generate a thinner transducer. But the conventional concept said that this kind of high harmonic modulator could only work on the odd harmonic.^1,2 It is impossible for the piezooscillator to work on the even harmonic. However, we find experimentally that the LiNbO₃ and dense flint glass acoustooptic modulator can work at the second harmonic for the first time as far as we know. We have made three modulators; all have the phenomena of the second harmonic. At the same time, we also prove theoretically that this kind of piezooscillator, which has one unfree end (this end is welded on the dense flint glass), may have non-odd harmonic. Using the second harmonic modulator, the second harmonic mode locking of an Ar⁺ laser has experimentally been demonstrated. Un-doubtedly, this will have important significance for the development of the acoustooptic mode-locking technique of an Ar⁺ laser.

© 1988 Optical Society of America