A tunable laser, including: a laser resonant cavity; a laser gain medium; an intra-cavity collimating lens; an acousto-optic tunable filter; a device exciting sound waves in an acousto-optic crystal; a radio frequency signal source providing radio frequency energy for the energy transducer and adjusting the oscillation wavelength of the laser resonant cavity by changing radio signal frequency; an optical phase modulator disposed between the intra-cavity collimating lens and the acousto-optic crystal; an optical etalon disposed between the optical phase modulator and the laser gain medium; a wavelength locker disposed at one of zero-order diffraction optical paths of intra-cavity light; a pigtailed collimator coupling laser output light to an optical fiber; a pumping source exciting the laser gain medium; a phase modulator driver for driving the optical phase modulator; and a signal control processing circuit.