It's never really a single wavelength, just a frequency with (originally) a very narrow bandwidth. Very large-bandwidth lasers were developed about 30 years ago, and few-wavelength pulses made using truly white light have been available for nearly 20 years. These are still incredibly useful, as their coherence times are huge, and with the appropriate phase profile over their spectrum they can make near-arbitrary waveforms on a femtosecond-picosecond timescale. The big benefit with this is the miniaturization, scalability, and potential application to imaging.
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I've got a CO2 laser you could look into :)
It's never really a single wavelength, just a frequency with (originally) a very narrow bandwidth. Very large-bandwidth lasers were developed about 30 years ago, and few-wavelength pulses made using truly white light have been available for nearly 20 years. These are still incredibly useful, as their coherence times are huge, and with the appropriate phase profile over their spectrum they can make near-arbitrary waveforms on a femtosecond-picosecond timescale. The big benefit with this is the miniaturization, scalability, and potential application to imaging.