Other Lasers and Laser‐Like Sources

Some light sources generate laser‐like light but not by stimulated emission in an oscillator. This chapter describes these lasers and laser‐like sources and explains how they work. It covers some emerging laser concepts that may find important applications in the future. Dye lasers are based on a family of large organic molecules that get their bright colors from transitions between complex sets of electronic and vibrational energy levels. Tuning across a much broader wavelength range is possible with a family of nonlinear devices called optical parametric sources. Frequency combs are very attractive for spectroscopy and measurement applications because they contain many evenly spaced spectral lines, promising very accurate measurements of time and wavelength. Extreme‐ultraviolet lasers operate on electronic transitions, but they are very different than the electronic transitions of conventional lasers. Free‐electron lasers can operate across a wide range of electromagnetic spectrum, from microwaves to X‐rays, depending on the electron energy and the magnetic field.