Tunable lasers are systems with the ability to change the output wavelength, either within a few units or tens of nm, as well as broadly tunable lasers over the entire spectral range. They can be either continuous or pulsed (femtosecond, picosecond or nanosecond).
Today, tunable lasers are mainly used in spectroscopy, microscopy, physical chemistry, as well as in metrology and quantum physics.
Continuous tunable lasers
These are based on laser diodes with an external resonator, which allows for tuning in a relatively small range (units to tens of nm), or on a Ti:sapphire laser, which then allows for tuning in the range of about 700 nm to over 1000 nm. For the NIR region of the spectrum, continuous OPO lasers with a relatively wide tuning range up to about 4.5 µm are offered.
Pulsed tunable lasers
These allow retuneability over a relatively wide range, typically from the UV region up to the NIR. They are usually based on OPO lasers, Dye lasers, Ti:sapphire lasers or supercontinuum generation and are quite often supplemented with various multiplication or conversion units just to extend the tunability to the widest possible region.
