Direct Doubling of 445nm /405nm diodes (cough cough)

[kecked]

Ok so its a dream to think you could double these guys but can you? I mean if I put 6w of 445nm in and get 10mw of 222 or 202 out of it that would be something. Looking for 200-210nm for a nitrate spectrometer and I dont want high voltage or gas discharge. Hoping for solid state as it goes in my fish tank. Thinking to use uncladded fiber as the sensor and measure the absorbance from the water.

There is a second peak at 305nm as well. Any ideas to get there solid state and low cost. (couple hundred max)

If I actual finish an idea I'd be dangerous :yabbem:

 

[CurtisOliver]

Possible but incredibly unlikely unfortunately. I would expect a very poor conversion rate if at all.
In order to match your desired range you would be using 405nm. You would need to opt more for single mode, limiting you to a 0.7-0.9W 405nm.
BBO has a phase matching range of >409.6nm. So you would be out of luck there. You also would definitely be out of luck with KTP.
LBO accepts anything over 160nm so you would be in luck. LBO is hygroscopic so careful handling is required, and care must be taken to avoid any moisture.
But it also would require a high threshold to get efficient doubling.
The only crystal that could possibly be viable would be BiBO. It has a phase matching range of 306.5nm onwards and has much higher efficiency than both LBO and BBO. It is the best shg crystal for the blue-uv spectrum.
It also doesn't suffer the problem of being hygroscopic. Sounds perfect right?
But the bad news is, it is a very expensive and hard to obtain crystal.
How much output could you expect? Very little I would imagine.
So I can't see your application being worth the time, effort and money TBH.

 

[Singlemode Laser]

Ok so its a dream to think you could double these guys but can you? I mean if I put 6w of 445nm in and get 10mw of 222 or 202 out of it that would be something. Looking for 200-210nm for a nitrate spectrometer and I dont want high voltage or gas discharge. Hoping for solid state as it goes in my fish tank. Thinking to use uncladded fiber as the sensor and measure the absorbance from the water.

There is a second peak at 305nm as well. Any ideas to get there solid state and low cost. (couple hundred max)

You can, and there are several demonstrations for lab based systems. But you can't use the multi mode diodes for this. You need a spatial single mode and a narrow linewidth to couple into the doubling crystal. In addition, the uv light will ionize the oxygen on the air it passes (loosing power very quickly). People using vacuum chambers or flush the laser chambers with dry nitrogen to circumvent this.

Singlemode

 

[kecked]

Thanks to all for the reply. Yes its a hard problem. I only need a few mw to make it work. It will go directly to either a fiber or through a window to water. Path will be mm long.
In time the diodes will make it down there. Well no harm asking. That's why I added the cough cough to the title.

Could you imagine a 5W 200nm laser! It would be like star trek in terms of tissue damage. Not a laser pointer I'd want to own.

Anyone seen diodes for sale in the 200-210 range? I have seen article since 2015 but no place that makes them yet.

So on the discharge side, are there inexpensive say 200.00 deutrium lamps that are small in size like 1" by 1" or so that run cool? That might also work. Since I'm in water I have plenty of cooling and can run pulsed operation if that is possible. say once a minute or even less.

 

[CurtisOliver]

Put it this way, wanting a few mW out of ~0.9W would give a desired efficiency of ~0.3%. In reality you would be lucky if you get that.
Just a loose thought, but i'm wondering whether more luck could be achieved using a high power 808nm and 4HG? :thinking: Again expect low efficiency, but the 404nm would self double.
But this would also require BiBO I'd of thought.
Edit: May be confusing BBO 4HG properties with BiBO. Not too sure.

 

[Singlemode Laser]

Thanks to all for the reply. Yes its a hard problem. I only need a few mw to make it work. It will go directly to either a fiber or through a window to water. Path will be mm long.

You won't get anywhere close to 1mW without a resonant doubling bow-tie cavity. You will also need a special fibre (hollow core f.e) for the UV.

Singlemode

 

[steve001]

The current state of Deep UV lasers.
https://www.laserfocusworld.com/art...est-diode-lasers-in-the-deep-ultraviolet.html

 

[Encap]

Fish tank? With fish in it?
If so why bother--a nitrate test kit is simple easy to use and cost like $10?

 

[Cyparagon]

Could you imagine a 5W 200nm laser! It would be like star trek in terms of tissue damage.

I think you missed the part where it was mentioned that 200nm doesn't propagate through air, as oxygen is rather opaque at this wavelength. This range is called vacuum UV for a reason.

 

[Encap]

I think you missed the part where it was mentioned that 200nm doesn't propagate through air, as oxygen is rather opaque at this wavelength. This range is called vacuum UV for a reason.

details, details :crackup:

Excellent point.

Everything is possible in imagination, not so in the real word.

 

[kecked]

Doing it this way is real-time and you can measure very low levels. The test kits are kind of hard to read the color change. There is a unit that does this so it’s proven. I just need a light source.

https://www.sciencedaily.com/releases/2014/04/140422113237.htm