Single lithium niobate crystal for mode selection and phase modulation in a tunable extended-cavity laser diode

A 1540-nm external-cavity laser diode with an intracavity electro-optic wavelength tuner is demonstrated. Coarse- and fine-wavelength tuning is achieved with a single lithium niobate wavelength tuner. One section of the crystal is used as a tunable-wavelength filter to tune the wavelength by mode hopping. The other operates as a phase modulator to change the optical length of the cavity and to tune the wavelength continuously. Coarse tuning by mode hopping is obtained over a range of 5.3 nm with a tuning rate of 580 MHz/V. Continuous tuning is obtained over 82% of the free spectral range of the cavity. The wavelength switching time is 10 ns for the cavity used.