A wavelength-tunable InGaAsP/InP multiple-λ/4-shifted distributed feedback (MQS-DFB) laser was demonstrated for the first time. A DFB laser with three λ/4-shifts and five electrodes was fabricated and its fundamental characteristics, such as tunability, spectral linewidth and FM response, were investigated. The stable single mode operation with an excellent 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.
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