| 摘要 |
PROBLEM TO BE SOLVED: To enable sorting of characteristics of semiconductor lasers, including discrimination of oscillation modes thereof, by a method wherein an optical filter of which the transmittance is dependent on a wavelength is provided on an optical path between the semiconductor layer and a photodetector. SOLUTION: A optical filter 4 is disposed between a semiconductor laser 1 and a photodetector 5 and made rotatable around the center 4a of a circle as the central axis by a motor 9. The filter 4 has a construction wherein sectorial filter elements A1 -An each passing light of a prescribed wavelength or above are juxtaposed adjacently and disposed circularly. In the case when wavelengths are so selected as to be between a wavelengthλ1 and a wavelengthλ2 (λ1 <λ2 ), the element A1 of the filter elements A1 -An ((n)>1) transmits the light of the wavelengthλ1 or above, while the element An transmits the light of the wavelengthλ2 or above, and they cut the light of the wavelengths below these ones. A current of an oscillation threshold value or above is supplied from a power source 2 to the semiconductor laser 1 and a laser light is emitted therefrom. The light is transmitted through the elements A1 -An and made to enter the photodetector 5 and a mode is sorted in a light signal processing circuit 6.
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