Studying the extremely short external cavity semiconductor laser with ray tracing method

Based on the ray tracing method, the implicit expression of the output spectrum of the extremely short external cavity semiconductor laser (ESECSL) is derived, and the output spectrum and P-I characteristic of the ESECSL are investigated. The results show that: when the length of external cavity is changed at the order of wavelength, the P-I characteristics of the ESECSL will undergo significant changes; with the variation of the external cavity length, the lasing wavelength of ESECSL will behave cyclical jump in the range of 10 nm. Especially, for the external cavity length changed within the range of 40-70 μm, the jump range of the lasing wavelength will reach the maximum. The simulations well agree with the experimental results reported.