CW

https://doi.org/10.1351/goldbook.C01484
Abbreviation for continuous wave, i.e. non-pulsed source of electromagnetic radiation.
Source:
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2234 (https://doi.org/10.1351/pac199668122223)