Analysis and design of external cavity, strong feedback, semiconductor lasers for use with coherent optical communication systems

Document Type

Conference Proceeding

Date of Original Version



External cavity, strong optical feedback, semiconductor lasers are analyzed using a rotated ellipse gain(REG) model. The model considers laser diode characteristics as well as the effects of optical feedback. Theoretical calculations on this strong feedback structure are developed in terms of amplification, injection locking, and mode ratio. Threshold current is expressed as a function of wavelength and temperature. Also various formulae for threshold current reduction, effective current, amplified output power, and reduced spectral linewidth are presented. From the amplified output power we calculate the spectral linewidth. We analyze in more detail the theoretical work of Patzak et al and show that spontaneous emission is reduced by frequency selective strong optical feedback. In designing external cavity lasers with strong feedback, mode ratio has to be larger than 100 for stable output power and frequency. It is possible to obtain many characteristic properties of the solitary laser diode with the help of the REG model. © 1987 SPIE.

Publication Title

Proceedings of SPIE - The International Society for Optical Engineering