# Laser for optics experiments

1. Jan 24, 2012

### luxor99

I'm looking for a good laser for optic experiments.

All the professional papers I've read show the use of a 351nm Argon Ion laser. A new 30 mW one of these is about $6,000, but I see used ones pop up on Ebay from time to to time. My question is, is there a difference between this laser used in university labs and one of those high-powered Wicked Lasers? I can get a 100mw 405nm laser there for about$100. The specs seem the same or superior...what am I missing?

Thanks!

2. Jan 24, 2012

### Cthugha

Ehm, that depends very strongly on the kind of experiment you want to perform. There are hundreds of laser manufacturers out there and for some experiments a simple laser pointer would suffice (e.g. double slit), for others you need slightly more expensive ones (e.g. PDC) or you might need extremely expensive ones (e.g. high power multi-beam femtosecond pump probe).

Do you need CW or pulsed? If pulsed, what pulse duration do you need? What powers do you need? Do you need a specific wavelength? Should the wavelength be tunable? Should the beams be spectrally broad or narrow? What about coherence times?

Also, you should be aware that most quality lasers require you to take some security measures to avoid harm to other people.

3. Jan 24, 2012

### luxor99

Thanks for the feeback! My main purpose is to experiment with entangled photons using a B-BBO crystal.

4. Jan 24, 2012

### Cthugha

So for which wavelength is your BBO crystal (or the one you are going to get) cut. These crystals are very picky as you need to get the phase matching right and will usually only work for a narrow range of wavelengths. Typically that would be around 351 nm which means Argon ion lasers which are not cheap. 405 nm lasers are usually semiconductor lasers which have rather low coherence. Anyway, it is best to check the available range of PDC crystals and crosscheck the range of available and affordable laser sources and see whether there is a wavelength at which you can get both.

5. Jan 24, 2012

### Dr Transport

The lasers you need usually run on three-phase power, unles you have that in your house or lab, you're gonna have troubles running those experiments.

6. Jan 25, 2012

### Cthugha

Maybe it would be easier to create entangled photons in the telecom range at around 1.55 micron with around 775 nm pump. That range should be accessible by cheaper lasers, however, detectors will get more complicated and expensive and I am not quite sure whether there are crystals for this range or you need more complex strategies based on cascaded quantum dot decays or such stuff. If there are crystals that might be realizable at home. Otherwise you are out of luck.

There are also turnkey solutions for this range. I know of Nucrypt and if I remember correctly also IDQuantique selling those (still far from cheap, though) and I do not know the specs.