Novel wavelength-tunable active-filter-type laser diodes

A wavelength-tunable laser diode which utilizes an active transmission filter of a lambda /4-shifted grating is proposed. 0.95-nm continuous tuning and 5.2-nm quasi-continuous tuning were achieved. Spectral linewidths ranged from 20 to 40 MHz during the tuning. The device structure and the operational principle are described. After a description of the fabrication, the device characteristics, including injection current versus light output, wavelength tuning, linewidth, and FM response, are presented. A flat FM response with large efficiency was obtained.>