WIDELY TUNABLE LASER CONTROL

A tunable laser has a first binary super grating (BSG), a second BSG, and a phase adjuster. The first BSG, the second BSG, and the phase adjuster are optically tuned by changing temperatures of respective heating elements. The tunable laser also includes three temperature sensors, a first sensor to measure the temperature of the first BSG; a second sensor to measure the temperature of the second BSG, and a third sensor to measure the temperature of the phase adjuster. A lasing frequency is determined by a set of values of the three temperature sensors. In some embodiments, instead of a third temperature sensor, a pilot tone is applied to the phase adjuster to lock to a maximum of an aligned pair of peaks.