A tunable laser operative to emit tunable radiation over an emission wavelength range having a center wavelength, with an output power spectrum over said wavelength range and an average emission power, said tunable laser comprising: an optical cavity including a first and second mirror (130, 140); a quantum well gain region interposed between said first and second mirrors (130, 140) and comprising at least one quantum well; a tuning region; and means for adjusting an optical path length of said tuning region; wherein: a free spectral range FSR of said optical cavity exceeds 5% of said center wavelength; said tunable laser operates substantially in a single longitudinal and transverse mode over said wavelength range; said means for adjusting an optical path length has a wavelength tuning frequency response with a 6-dB bandwidth greater than about 1 kHz, each of said at least at least one quantum well is substantially aligned with a peak in an optical standing wave pattern of said optical cavity; said means for adjusting an optical path length is a MEMS-actuation mechanism configured to adjust a physical length of an airgap; and said actuation mechanism comprising a deformable dielectric membrane transparent over said wavelength range and attached to a rigid support structure; said MEMS-actuation mechanism comprising a membrane stress in a range of 100-1000 MPa; the actuation mechanism geometry showing a central plate with supporting arms, a frequency response of said MEMS-actuation mechanism has damping substantially increased by squeeze-film damping effects through a central plate having a diameter that is greater than 50 μm. an optical cavity including a first and second mirror (130, 140); a quantum well gain region interposed between said first and second mirrors (130, 140) and comprising at least one quantum well; a tuning region; and means for adjusting an optical path length of said tuning region; wherein: a free spectral range FSR of said optical cavity exceeds 5% of said center wavelength; said tunable laser operates substantially in a single longitudinal and transverse mode over said wavelength range; said means for adjusting an optical path length has a wavelength tuning frequency response with a 6-dB bandwidth greater than about 1 kHz, each of said at least at least one quantum well is substantially aligned with a peak in an optical standing wave pattern of said optical cavity; said means for adjusting an optical path length is a MEMS-actuation mechanism configured to adjust a physical length of an airgap; and said actuation mechanism comprising a deformable dielectric membrane transparent over said wavelength range and attached to a rigid support structure; said MEMS-actuation mechanism comprising a membrane stress in a range of 100-1000 MPa; the actuation mechanism geometry showing a central plate with supporting arms, a frequency response of said MEMS-actuation mechanism has damping substantially increased by squeeze-film damping effects through a central plate having a diameter that is greater than 50 μm. a free spectral range FSR of said optical cavity exceeds 5% of said center wavelength; said tunable laser operates substantially in a single longitudinal and transverse mode over said wavelength range; said means for adjusting an optical path length has a wavelength tuning frequency response with a 6-dB bandwidth greater than about 1 kHz, each of said at least at least one quantum well is substantially aligned with a peak in an optical standing wave pattern of said optical cavity; said means for adjusting an optical path length is a MEMS-actuation mechanism configured to adjust a physical length of an airgap; and said actuation mechanism comprising a deformable dielectric membrane transparent over said wavelength range and attached to a rigid support structure; said MEMS-actuation mechanism comprising a membrane stress in a range of 100-1000 MPa; the actuation mechanism geometry showing a central plate with supporting arms, a frequency response of said MEMS-actuation mechanism has damping substantially increased by squeeze-film damping effects through a central plate having a diameter that is greater than 50 μm.