Monolithic wide wavelength tunable mid-IR laser sources

A method of characterizing a monolithic tunable mid-infrared laser comprising a heterogeneous quantum cascade active region together with at least a first and a second tunable integrated distributed feedback gratings, the method comprising operating the laser while tuning the first grating through its full tuning range, while holding the reflectivity function of the second grating constant, then operating the laser while tuning the second grating through its full tuning range, while holding the reflectivity function of the first grating constant:

• the method further comprising, during both steps of operating while tuning, simultaneously detecting the wavelengths output by the laser with a wavelength monitoring device;
• wherein the wavelength monitoring device comprises:
• a first power monitor;
• and
• a wavelength discriminator, the wavelength discriminator comprises a second power monitor and a transmissive or reflective wavelength-selective filter with an ever-increasing or ever-decreasing filter function over a tunable wavelength range.