| 摘要 |
PROBLEM TO BE SOLVED: To obtain a semiconductor laser module which can produce a stable output of laser light, even when a laser is oscillated at two modes of a wavelength determined by a fiber grating and a wavelength obtained by a semiconductor laser element. SOLUTION: Laser light which converge through a second lens 3 is focused at an end face of an optical fiber 5 and is propagated through the fiber 5. Then, part of the propagated light is reflected by a fiber grating 6, and the reflected laser light reverses its direction to return to a semiconductor laser element 1 via the lens 3, a bandpass filter 4 and a first lens 2, thus forming an external resonator between the back side of the element 1 and the grating 6. This permits a laser to oscillate at a wavelength band determined by a diffraction grating of the grating 6. Therefore, even when the laser is oscillated at two modes of a wavelength determined by the grating 6 and a wavelength provided by the element 1, stable laser light can be outputted.
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