Wavelength Stabilization of a Semiconductor Laser in High-Speed Modulation Using Saturated Absorption Spectroscopy of Atomic Lines

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We stabilized the oscillation frequency of a semiconductor laser at 800 nm wavelength region under direct frequency shift keying (FSK) using the Rb absorption lines in this year. The better stability had already been observed in the peak-hold method in comparison with the traditional method of the unmodulated case. Therefore we investigated the stability under some different FSK conditions, i.e., some different frequency shifts and duty ratios in this year.1.We observed that the frequency stability in the peak-hold method was improved under all frequency shift conditions compared with the traditional method at duty ratio 50 per cent. The best stability was obtained at the frequency shift which was expected to be the best value by the theoretical estimation. 2.We observed that the stability obtained in the peak-hold method depended much less on the duty ratio than in the traditional method. This result means the peak-hold method is useful under the generalized modulation condition. 3.The wavelength reference point for the stabilization may be changed under the modulation in the traditional method. However, the stabilization point in the peak-hold method also depended much less on the duty ratio than in the traditional method.We investigated the peak-hold method instead of the method using the saturated absorption spectroscopy of atomic lines for the stabilization in this year. This is because we thought that the peak-hold method should be investigated thoroughly. We will investigate the better stability at the higher modulation frequency and then stabilize the wavelength by the method using the saturated absorption spectroscopy of atomic lines. The stabilization at the wavelength of 1.55 mum will be investigated in the peak-hold method, too.