Coherence Collapse Of The Dual Fiber Bragg Grating External Cavity Semiconductor Laser

The preconditions and controlling factors of coherence collapse (CC) are analyzed by the rate equations and dual fiber Bragg grating (FBG) couple mode theory based on the physical process of dual FBG external cavity semiconductor lasers. A method of achieving and controlling CC multi-mode stable state is put forward for dual FBG external cavity semiconductor lasers. When the dual FBG external cavity semiconductor laser operates at the multi-mode stable state under the CC regime, the CC length reduces. The spectrum of the laser is relatively stable within the CC length. The experimental results show the output power of the laser is stable while the laser with the 3% external reflectivity is operating under the CC regime. The side mode suppression ratio is more than 45 dB. The full wave at half maximum broadens from 0.5 nm to 0.9 nm dramatically as soon as the laser operates from the incoherence collapse regime to the CC regime. The wavelength shift is less than 0.5 nm at the operating temperature of 0 degrees C-70 degrees C. The minimum of the CC length is less than 0.5 m. The CC application of dual FBG external cavity semiconductor lasers is vital to improve the performance of optical fiber amplifiers and fiber lasers.