Tunable laser and method to tune a wavelength of a light emitted by the laser

A tunable laser comprising:

• a cavity, the cavity including:
• a gain medium,
• an optical tunable filter,
• a first and a second mirrors, one of which is partially reflective, wherein:
• the first mirror is partially reflective and the second mirror is substantially totally reflective;
• the first mirror defines a mirror free spectral range and the optical tunable filter defines a filter free spectral range;
• and
• the mirror free spectral range is of the same order of magnitude of the filter free spectral range;
• and
• wherein the optical tunable filter includes:
• a first and a second electrodes,
• a liquid crystal, the liquid crystal being subject to an electric field created by the first and second electrodes, and
• a voltage generator to apply a voltage difference between the first and second electrodes, said voltage generator being programmed for:
• applying the voltage difference for at least a driving time interval lasting less than 1 μs;
• and
• varying the voltage difference applied between the first and second electrodes within the driving time interval so that a maximum applied voltage difference is reached and said maximum applied voltage is above 0.1 kV.

A method to tune a wavelength of a coherent light signal emitted by a tunable laser, the tunable laser comprising:

• a cavity, the cavity including:
• a gain medium,
• an optical tunable filter,
• a first and a second mirrors, one of which is partially reflective, wherein the optical tunable filter includes:
• a first and a second electrodes,
• a liquid crystal, the method comprising:
• applying a voltage difference between the first and second electrodes to apply an electric field to the liquid crystal;
• wherein applying a voltage difference includes:
• applying the voltage difference for at least a driving time interval lasting less than 1 μs;
• and
• varying the voltage difference applied between the first and second electrodes within the driving time interval so that a maximum applied voltage difference is reached and said maximum applied voltage is above 0.1 kV, wherein varying the voltage difference applied to the first and second electrodes within a driving time interval includes varying the voltage difference between a minimum and a maximum and wherein varying the voltage difference applied to the first and second electrodes within a driving time interval includes varying the voltage difference linearly with time.