8 kHz linewidth, 50 mW output, full C-band wavelength tunable DFB LD array with self-optical feedback

We describe a 1.5 μm, narrow linewidth, high output power wavelength tunable LD that employs a self-optical feedback circuit. By incorporating an optical circulator-based feedback circuit in a DFB LD array, we have successfully reduced the oscillation linewidth from several MHz to less than 8 kHz over the full C-band range. A high output power of　approximately 50 mW and a low relative intensity noise of less than -130 dB/Hz were simultaneously achieved. Furthermore, by employing a partial reflection mirror as a self-optical feedback circuit, we have also realized a full C-band wavelength tunable LD with a linewidth of less than 11 kHz and a simple laser configuration.