[STM]

Hello everyone,

Is there a simple LED light (similar to the conventional white LED light in touch lights) that I can use for my experiment. I need a simple light source to irradiate rose bengal-treated filter at 550 nm (the excitation wavelength of rose bengal).

Is there a simple LED light source that can give this light? Nothing too complicated and expensive

[Arkcon]

Whenever someone needs a source for optics, whether advanced hobbyist or a one off technical need, I always send them to Edmund Scientific:  http://www.edmundoptics.com/illumination/led-illumination/

[Corribus]

If you have a good white light source already, you might consider just buying a good interference filter set to 550 nm. You could probably buy one for about 100$ (US) from any decent optics supplier. This also gives you flexibility because if you need a new wavelength you can just buy a new filter.

It really depends on the intensity of excitation source you need, though, and the specifics of your experiment.

[Enthalpy]

Traditional green leds (GaP with dopants deep in the bandgap) emit a good portion of their power around 550nm. Not the most efficient Leds, but they're dirt-cheap, and available from the Chinese grocer at the street corner.

Here a spectrum example where "G" is a green Led, this one happens to be a L-1002GB from Kingbright. Find more doc under:
"green led" datasheet
just cable hundred of them if needed.

Some material more recent than GaP provides better power and efficiency. The peak 525nm spread to 550nm. Here the datasheet for the Philips Lumileds LXHL-BM01
datasheet.octopart.com/LXHL-BM01-Lumileds-datasheet-500422.pdf
second spectrum appended.

A general introduction:
https://en.wikipedia.org/wiki/Light-emitting_diode

[STM]

Thank you all for your helpful information. I now have a better insight.