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Definition: operation mode of a laser with continuous light emission
Continuous-wave (cw) operation of a laser means that the laser is continuously pumped and continuously emits light. The emission can occur in a single resonator mode (→ single-frequency operation) or on multiple modes.
The first continuous-wave laser was a helium–neon laser operating at 1153 nm [1]. A version working with the now common emission wavelength of 632.8 nm was demonstrated soon after that. Later on, many other types of lasers were developed which can also be operated continuously: other gas lasers, many types of solid-state lasers (including semiconductor lasers), and dye lasers.
Quasi-continuous-wave Operation
In continuous-wave operation, some lasers exhibit too strong heating of the gain medium. The heating can then be reduced by quasi-continuous-wave operation, where the pump power is only switched on for limited time intervals.
Continuous-wave Mode Locking
Some lasers are called continuous-wave mode-locked. This means that the laser is mode-locked, and the pulse energy (or average power) is constant, i.e. there is no Q-switched mode locking. Despite the emission of pulses, mode locking can be considered as a kind of continuous-wave operation in the sense that the resonator modes are excited with constant powers.
Bibliography
| [1] | A. Javan, W. R. Bennett Jr., and D. R. Herriott, “Population inversion and continuous optical maser oscillation in a gas discharge containing a He–Ne mixture”, Phys. Rev. Lett. 6 (3), 106 (1961) |
See also: modes of laser operation, quasi-continuous-wave operation, resonator modes
