| 摘要 |
PURPOSE:To fix the oscillation wavelength of semiconductor lasers by feeding part of laser light back to the laser semiconductors by using a composite diffraction grating of a concave surface. CONSTITUTION:If the grating constant in the central part 2 of a composite diffraction grating 1 is defined as (d), and that of a peripheral part 3 as 2d, and if plural pieces of semiconductor lasers (a), (b), (c)- of which the oscillation wavelengths differ with each other are disposed with Littrow configuration in such a manner that with respect to these lasers the diffracted beams of light by the diffraction grating in the central part return exactly to the respective light source points, the oscillation wavelengths of the respective semiconductor lasers are fixed at mlambdan=2dsinthetan. Here, (m) is the order of diffraction, and thetan is the incident angle of the n-th semiconductor laser. With such constitution, it results in that the beams of light from the semiconductor lasers (a), (b), (c)... of the fixed oscillation wavelengths are concentrated at a focus 6 by the diffraction grating in the peripheral part. |
