Pumping nonlinear crystals with 808?

[digital_blue]

Just a thought, if nonlinear crystals such as KTP double the frequency and halve the wavelength, would pumping 808nm or even 635nm through a crystal result in half the wavelength?

 

[likewhat]

yes, people do it all the time with Ti:sapphire lasers which are centered at 800 nm. Typically it is done in a cavity though in order to get high enough intensity for the doubling process to be efficient.

 

[diachi]

There are crystals that can double ANY frequency, I saw one on eBay a while ago, heurrusciences was selling it. KTP and double more than one frequency, but it needs a different coating.

-Adam

 

[tomcat]

ktp is a bit bitchy about what it will double e/g blues dont use ktp they use bibo or lbo

i think get a full set of nonliners would be your best bet for pumping 808-404 becuase not all crystals will have good losses at that frequency

 

[heruursciences]

KTP will double till about 528nm, above this in the blues you need Bibo (Bismeuth B-borate), BeBO (beryllium B borate) or KNbo3 (potassium Niobate) Of these BiBo is the most efficient, but is also the most easily damaged from optical power.

If doing hard UV you need LBO (lithium B-borate) or BBO (B-Barium Borate)

Really high power stuff uses the dihydrogen phosphate and Arsenate series crystals. Ie KDP, RbDP RbH2AsO4, NH4H2Po4 etc.

The last one you can grow from superphosphate fertilizer as easily as rock candy! Get a nice crystal, polish the sides with 1800- grit sand paper, clean with naphtha, place a drop of mineral oil and a microscope cover slip on each polished side, and you can get strong green pulses with a SSY-1 Q-switched yag laser without trying very hard.

The best all around nonlinear crystal is PPLN (periodically poled Lithium Niobate) for shorter wavelengths, and periodically poled KTP for longer wavelengths to about 4.2um.

An excellent example of this is the crystals MI Lasers is selling, it is optimized for 1.5um, however you can get 755nm light out by pumping with a varo q-switched erbium laser, and if you are really creative you can even get about 500nm stoplight led blue-green light out with one of these- not easy, but doable.

The mid to far IR is covered with exotic crystals such as BiCdTe, and PbTe as well as doped sulfides of cadmium, mercury and lead.

 

[disma]

"The last one you can grow from superphosphate fertilizer as easily as rock candy! Get a nice crystal, polish the sides with 1800- grit sand paper, clean with naphtha, place a drop of mineral oil and a microscope cover slip on each polished side, and you can get strong green pulses with a SSY-1 Q-switched yag laser without trying very hard."


Have any links or instructions on how to do this? Maybe an exact fertilizer brand, or a list of where to get the right stuff? I would love to try this. I will have to put my q-switch back in though.

 

[heruursciences]

Look for the kind with 12-61-0 on the label, it's chemically pure Ammonium dihydrogen phosphate H2Nh4PO4; If you want KDP instead, get the kind with 0 -34-52 on the lable- chemically pure Potassium dihydrogen phosphate KH2PO4.

 

[disma]

awesome, now how do you grow the crystals? :-? I take it that this still might be over my head.

 

[MacGyver404]

Might anyone have a chart of what crystals double or triple what frequencies?

 

[Benm]

One sidenote on all this: It is virtually impossible to get frequency doubling using a diode laser as the light to be doubled.

The problem is that the wavelength range produced from a diode laser is too broad: the doubling process requires 2 fotons very close in energy. Solid state lasers such as Nd:YAG have very narrow output ranges, and can also be operated pulsed to achieve higher energy densities. This helps because the nonlinear doubling process gets more efficient with rising energy density.

So if you grow one of those crystals yourself, you'd still need a solid state laser with pulsed operation to make it happen. If you tried CW, i wouldn't be surprised if you destroy the crystal before getting any green.

 

[Archane]

Awesome info heruursciences

I was looking for some of these crystal names for awhile but wasn't sure how to go about it. It's like you answered all my questions in one shot =)

thank you.

 

[jmgallego]

Just a thought, if nonlinear crystals such as KTP double the frequency and halve the wavelength, would pumping 808nm or even 635nm through a crystal result in half the wavelength?

I would be interested in testing my dilda (~200mW) on one of them crystals... hmmm that would be come out around the 320nm :thinking:

 

[Bluefan]

The crystals need to be cut at a proper angle too for the phase matching. For a good conversion efficiency you need a high power, so diodes are not possible. Inside a cavity of even a simple pointer is so much light circulating that the conversion get's better. A diode also mode-hops, which is irritating for phase matching. And the beam profile needs a lot of work. And for special wavelengths, you'd need special coatings. It can be done with diodes, but it would need a lot of work.
Pulsed Q-switched YAG lasers are very easy. The peak power is in megawatts, so just a single pass through a crystal is enough, even homegrown crystals can work (it has been done actually).