I wanna make tonic water fluoresce with a laser pointer.

Yeah_man_405 · Mar 12, 2021

Is 405 nm the best for it? How high mW can I go without needing safety glasses? I want to be able to point a laser at a bottle of tonic water and see that nice cyan color, so I'm assuming light will reflect everywhere so it'll need to be low powered.

I would really appreciate any suggestions on what nm, what mW, and where to buy such a laser pointer. I'd be happy with something around $30 that takes AAA's or rechargeables.

Encap · Mar 12, 2021

A laser of any wavelength over 5mW is not considered eye safe however even 5mW or less can cause eye damage under certain circumstances.

See: https://www.lasersafetyfacts.com/classes-menu.html

For detailed information on safe laser use, laser hazards, and related see: https://www.laserpointersafety.com/

CurtisOliver · Mar 12, 2021

A <5mW 405nm would be more than sufficient to observe fluorescence. However it should be noted that a lot of cheap 405nm pointers online exceed 5mW despite claiming otherwise. As long as you don't do anything stupid they are relatively safe. It is easy to eliminate unknown reflections by keeping the laser to only entering at a low angle of incidence.

skijohn · Mar 12, 2021

CurtisOliver said:
A <5mW 405nm would be more than sufficient to observe fluorescence. However it should be noted that a lot of cheap 405nm pointers online exceed 5mW despite claiming otherwise. As long as you don't do anything stupid they are relatively safe. It is easy to eliminate unknown reflections by keeping the laser to only entering at a low angle of incidence.

And some have poor IR filtering...

CurtisOliver · Mar 12, 2021

405nm pointers are diode therefore produce no IR. You are correct for cheap 532nm DPSS pointers.

kecked · Mar 12, 2021

Or use an led....

FireMyLaser · Mar 12, 2021

kecked said:
Or use an led....

OP asked for a laser.

skijohn · Mar 12, 2021

kecked said:
Or use an led....

Isn't a laser diode technically an "led"?

CurtisOliver · Mar 12, 2021

The only similarity is the fact it’s a optical semiconductor. Laser emission and ordinary light emission have different characteristics.

skijohn · Mar 12, 2021

I learn something new here every day!

kecked · Mar 12, 2021

The absorption band is 250-350nm with emission at 450nm. The quantum efficiency at 405nm is stupid low. Even moving back to 375nm the resulting change is nearly 50% Thus an led will yield a much better result. There is also an emission cross over at 405nm so separating signal and source will be harder.

Here is a good discussion https://chem.libretexts.org/Courses/British_Columbia_Institute_of_Technology/Chem_2305/01:_Spectroscopy/1.02:_Photoluminescent_Spectroscopy

No an led is not a laser though a laser diode can exhibit non coherent properties below the threshold of lasing. The devices are different however.

FireMyLaser · Mar 12, 2021

OP stated, several times, he wants a laser, and even explains why he wants it. And a cheap 405nm laser will do what he wants, and using it with care and it will be fine. No need for hazmat suits or optimal efficiency.

Yeah_man_405 · Mar 12, 2021

FireMyLaser said:
OP stated, several times, he wants a laser, and even explains why he wants it. And a cheap 405nm laser will do what he wants, and using it with care and it will be fine. No need for hazmat suits or optimal efficiency.

Thank you and everyone who pitched in. I'm definitely going to get a 405nm ~5mW laser. I've checked a buyers guide that's on this site and none of the websites listed had a weak enough/cheap enough product. Maybe Ebay would be fine for my purposes?

CurtisOliver · Mar 12, 2021

eBay will get you the cheap >5mW ones I was talking about. It will meet your requirements. Just don't be reckless.

Arcygenical · Mar 22, 2021

Why not go with any ~400nm 3w LED source, usually comes with a driver too. Throw it on a heatsink, and put the bottle over top of it.. 5-10$ on ebay, with better dispersion (will light the whole bottle).

But, if you want to see the *line* of fluorescence in your tonic, obviously the 405nm diode is the way to go.

Unown (WILD) · Mar 23, 2021

FireMyLaser said:
OP stated, several times, he wants a laser, and even explains why he wants it. And a cheap 405nm laser will do what he wants, and using it with care and it will be fine. No need for hazmat suits or optimal efficiency.

Give it a rest. There's no need to get your panties in a bunch when people offer alternative suggestions.

I wanna make tonic water fluoresce with a laser pointer.

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