Analysis of the spontaneous emission of a tunable phase-shift-controlled DFB laser filter

Using a transfer matrix method, the results of analysis of the spontaneous emission spectrum of a three-section phase-controlled distributed feedback (DFB) laser for implementing a continuously tunable optical filter are presented. The influence of various parameters-net field gain, coupling coefficient, phase shift and reflection coefficients-on the spectrum behavior are studied theoretically. The main-to subtransmission peak magnitude ratio can be chosen while varying the frequency, which demonstrates the tunability of the three-section phase-controlled DFB laser filter. Analysis shows that a three-section DFB laser (a passive phase shift control region between two DFB structures) presents a single-mode spontaneous emission spectrum operating over a wide continuous tuning range of less than 1 nm