A tunable laser system utilizes a frequency shift compensated acousto-optic tunable filter. The wavelength accuracy and stability is achieved by a wavelength locker utilizing two separate intracavity light beams without the need to use beam splitters to significantly reduce the space typically needed by a conventional wavelength locker, and provide more stable operation and easy assembly. The acoustic optical tunable filter includes an acousto-optical crystal with a transducer coupled to the crystal to generate acoustic waves, and an optical mirror to reflect the diffracted light beam back to the acousto-optical medium again such that the frequency shift by two diffractions is compensated. By using different laser gain mediums, acoustic wave driving frequencies and acousto-optical crystals, this invention can be used to make tunable lasers in wide range of optical wavelengths for many different applications.