How do white leds work then?A single "white only" laser is impossible. Is only possible in imagination where everything is possible.
"White" light we perceive is nothing but a mixture of all the wavelengths in the visible light spectra.
Thus, there isn't any specific value for the wavelength of white light. Rather, Its a resultant of superposition of all the wavelengths from 400 to 800 nanometers which is the visible spectrum
You can mix wavelengths to get various visual color effects but they do not create any new wavelengths nor conventional full spectrum "white"---white created still remains the wavelengths used-- if you split the created "white" apart with a prism you get the wavelengths used to create the illusion of white.
Many people using "Wavelength" and "Color" interchangeably, when in fact they are apples and oranges different.
Wavelength is a physical property. Wavelength is not a description of a color you perceive/see.
It is term independent of human observation -- a description of electromagnetic radiation.
The properties of 'Light" are very different from the properties of the human visual system and are independent of it.
See: Properties of Light | PVEducation and here: https://en.wikipedia.org/wiki/Photon
Color is not a physical property; it is merely the brain’s interpretation of different wavelengths of light based on input signal from the eyes. Color names are words/symbols for that brain activity.
Really you should Google that rather than ask here, in a few words“white” LEDs, they’re really just blue LEDs with a coating of a yellow phosphor . LEDs are not lasers in any case either. Start here: https://hackaday.com/2018/10/29/history-of-white-leds/How do white leds work then?
Or this Acebeam flashlight which high energy laser excitation phosphor produces white lightReally you sould Google is but in a few words “white” LEDs, they’re really just blue LEDs with a coating of a yellow phosphor . LEDs are not lasers either. Start here: https://hackaday.com/2018/10/29/history-of-white-leds/
Different but similar for a flourescent light --high energy UV excitation of a phosphor to produce "white" light.