WAVELENGTH-TUNABLE OPTICAL FILTERS WITH PHASE-SHIFTED DFB STRUCTURES

A new wavelength-tunable optical filter which is based on a phase-shif t-controlled distributed feedback structure with two phase shifts alon g its active layer has been studied, in particular, the effects of pha se shifts on tuning range, peak power transmissivity, and side-mode su ppression ratio (SMSR). The analysis indicates that when phi(1) = phi( 4) = pi/2, the filter wavelength tuning range is 22.1 Angstrom for the grating coupling coefficient kappa = 6/mm while maintaining almost co nstant transmissivity (gain) of more than 35 dB. The filter SMSR range s from 11.1 to 25.4 dB. The results for asymmetric values of phi(1) an d phi(4) are also given. (C) 1997 John Wiley & Sons, Inc.