Patent ID: 9711945
Date: 2017-07-18
CPC Classifications: H01S

Claim:
1. A method of designing a semiconductor laser device used for a pumping light source for Raman amplification and including: a semiconductor laser element including an optical cavity including a semiconductor light-emitting unit and a first reflection unit reflecting a light outputted by the semiconductor light-emitting unit; and a second reflection unit disposed at a laser-light-output side of the semiconductor laser element, wherein the first reflection unit includes an output-side reflection unit provided at the laser-light-output side and a rear-end-side reflection unit provided at an opposite side to the laser-light-output side, the method of designing comprising: controlling: a physical distance L (cm) between the output-side reflection unit and the second reflection unit; and an effective optical feedback κ(1/ps) to the semiconductor laser element, the effective optical feedback κ(1/ps) defined by a below-presented formula (1) including a circulating time τ of the light in the semiconductor laser element, a reflectivity R selecting the semiconductor laser device in which a Low Frequency Fluctuation (LFF) period is equal to or smaller than 20 ns as the semiconductor laser device in which a high speed switching occurs between a Fiber Bragg Grating (FBG) mode and a Fabry-Perot (FP) mode; and using the selected semiconductor laser device as a semiconductor laser device oscillating in a coherent collapse mode, wherein the controlling is performed while measuring a relationship between an intensity of the laser light outputted from the semiconductor laser device and time to perform the selecting by finding out the semiconductor laser device in which the high speed switching occurs between the FBG mode and the FP mode, when measuring the relationship between the intensity of the laser light outputted from the semiconductor laser device and the time to perform the selecting, the LFF period is defined as an interval between a reference peak at which a decrease in the intensity is greatest in a predetermined time period and a nearest adjacent peak of which absolute value of the intensity is equal to or greater than 60% of the reference peak, and the semiconductor laser device at a time the defined LFF period is equal to or smaller than 20 ns is determined and selected as the semiconductor laser device to be used