it would be way cooler to have a portable full spectrum lamp (like a black body radiation based one), that you can then continuously filter to any wavelength with a dial. Ideally anything between microwaves and x-rays. like with a prism or something.
It would probably have to as large as the most powerful portable LED lamps, so you get a usable brightness out of all frequencies and still be dim lol.
Perhaps you could use tunable lasers, but as I understand it, they aren't that versatile yet.
biologists and geologists would love it