Wavelength-tunable InGaAsP-InP multiple- lambda /4-shifted distributed feedback laser

A wavelength-tunable InGaAsP/InP multiple- lambda /4-shifted distributed-feedback (MQS-DFB) laser was demonstrated for the first time. A DFB laser with three lambda /4 shifts and five electrodes was fabricated, and its fundamental characteristics, such as tunability, spectral linewidth, and FM response, were investigated. Stable single-mode operation with a side-mode suppression ratio (SMSR) of more than 40 dB was confirmed. Continuous wavelength tuning under constant output power mode was obtained with a range of 1.7 nm. Minimum spectral linewidth was 3 MHz at an output power of 20 mW. Flat FM response up to 4 GHz with an efficiency of about 0.65 GHz/mA was also obtained.>