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FrozenGate by Avery

10W Q-switched 1064nm Fiber Laser

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r34p3rex

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Feb 2, 2008
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Just got this bad boy in at work. It's a NuFern Fiber laser.. 10W average power, 5kW peak power, Q-switched, 100kHz pulse repetition rate, 100ns pulse width. It's fitted with a 7mm beam expander to give it <0.5 mRad divergence. Just need to select an objective lens now!

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Can't wait to see what it can do!
 
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Is it really as simple as placing the KTP crystal in front of the 1064nm beam? I don't have too much experience with DPSS lasers. Does the crystal need to be actively cooled?
 
r34p3rex said:
Is it really as simple as placing the KTP crystal in front of the 1064nm beam? I don't have too much experience with DPSS lasers. Does the crystal need to be actively cooled?
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You should be able to get some 532nm out by focusing the beam into the crystal - KTP is sensitive to polarization, so you'd need to get the orientation right. I'd also start at a lower output on the 1064nm if you're doing that by hand - just to avoid any damage to the KTP or yourself. Of course, you're not going to be breaking any efficiency records with a setup like that.

As for temperature - you'll probably want to heat the KTP up, not cool it down. They generally like to be above ambient temperature for best efficiency- often 40-50*C. Although if you're hitting it with 10W of pump it might be an idea to use a TEC to control temperature, that way you can heat or cool to get the right temperature if needed.

Ideally KTP would be intra-cavity, not extra-cavity. However, not really something you can do without modifying the laser you have.

 
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Yea I'm not trying to break any efficiency records or anything.. just looking to learn a bit :p

Thanks for the info!
 
diachi said:
You should be able to get some 532nm out by focusing the beam into the crystal - KTP is sensitive to polarization, so you'd need to get the orientation right.
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That's where problems start. The laser most likely is random polarized. Some green will be generated but likely with a very unstable output.
 
lazeristasUVISIR said:
That's where problems start. The laser most likely is random polarized. Some green will be generated but likely with a very unstable output.
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Yes, I did some digging, looks like this is randomly polarized.

The high peak power from the Q-switching would certainly help with green output, but really you'd want something with a polarized output and a proper mount/temperature control for the KTP. Even then - the best efficiencies are generally achieved in intracavity designs as far as I've read, due to the higher power available at the fundamental frequency inside of the cavity.

Not to say you can't reach good efficiencies with an extracavity design - it's certainly possible, just much less practical - the power density required is insane. See below:

The output power of the SHG increased nonlinearly while the repetition rate of the fundamental IR laser decreased, as shown in Fig. 2. At the repetition rate of 60 kHz, 103.5Waverage power of green laser at 532 nm was achieved, corresponding to 154.5 W average power of the fundamental IR laser. The conversion efficiency from IR to green laser was about 67% at 60 kHz, corresponding to the diode-to-green optical conversion efficiency of 24%. Enhancement of the repetition rate of the IR laser yields to the widening of the pulse duration and the nonlinear decreasing of the peak power of the IR laser. Since the frequency conversion efficiency of the SHG is proportional to the power density of the fundamental frequency laser, therefore, the conversion efficiency of the SHG went down as the repetition rate increased, even though the average power of the IR laser increased to 170W at 500 kHz. 24W green laser was obtained at 500 kHz. The repetition rate of the IR laser wasn’t decreased lower than 60 kHz to prevent the damage of the dichromatic coating on LBO crystal.
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The LBO crystal was chosen as the frequency doubling crystal, because of its relatively large acceptance angle (acceptance angle×length~52 mrad·cm), good mechanical characteristics, especially for its high damage threshold. The damage threshold of the LBO crystal is as high as 2.5 GW/cm2 at τ=1.3 ns @1064nm [18], which is about 10 times as large as that of KTP crystal. Therefore, LBO is suitable for high power second harmonic generation, especially for high peak power pulse operation, even though its nonlinear coefficient is relatively small (~1.16×10-12m/V).
Click to expand...

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-16-19-14335&id=171557

Edit: Anyway, not entirely relevant to the thread ... carry on :D
 
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