A wide mode-hopping free and narrow linewidth tunable laser diode source with a Littman-Metcalf arrangement based on a diffraction grating is presented. Several experiments are carried out to demonstrate the tuning characteristics and spectral linewidth of the proposed external-cavity diode laser source. A wide no mode-hopping continuous wavelength tuning range about 59.13 nm in ultra-C-band with a narrow spectral linewidth of less than 100 kHz is obtained. An optical signal to noise ratio of more than 65 dB and an output power more than 14.8 dBm over the whole tuning range can also be realized in a long-term free running condition. The proposed tunable laser allows simultaneously mode-hopping free and narrow linewidth tunable radiation, thus opening a door for practical application such as coherent detection.

A high side-mode suppression ratio external-cavity wavelength-swept laser system with a wide mode-hopping free tuning range is developed. The proposed wavelength-swept laser is based on a single-angled facet gain chip in a classical Littman-Metcalf external-cavity configuration using a blazed diffraction grating as the feedback element. The output power, side-mode suppression ratio, and tunable range of the external-cavity wavelength-swept laser system are experimentally measured. Wide mode-hopping-free continuous wavelength tuning range about 100 nm in CL-band with a side-mode suppression ratio of more than 65.64 dB are realized. An output optical power of more than 14.12 dBm over the entire tunable region can also be achieved. The proposed external-cavity wavelength-swept laser system allows simultaneously high side-mode suppression ratio and no mode-hopping tunable radiation, thus opening a door for practical applications such as optical modulation schemes.