Searching for a process to generate SHG,
we have an ultra short laser pulse oscillator but needed a low cost process (Preferably a non linear crystal) to generate SHG
Just to add some info to the answer above - many setups use the nonlinear crystal LBO which is claimed to produce higher-quality SHG beams. Its drawbacks: 1. Since it's effective nonlinearity is weaker, a longer crystal than BBO is typically needed. 2. Its damage threshold is a bit lower than BBO (if I'm not mistaken...) - but that's relevant only in high-power operation.
You can check the free software SNLO (http://www.as-photonics.com/snlo) and learn about the cutting angles required for many nonlinear crystals depending on the wavelengths of your system.
I hope it helps,
Assaf
If you are looking for really chip way for SHG and do not care for efficiency(I.e. need it for pulse characterizations or so) you could use B-BBO powder spin coated on any glass. If you do it densely enough it works pretty well.
It would be helpful to know the pulsewidth, average power, wavelength and desired conversion efficiency. In general femptosecond lasers need very short crystals for efficient operation since their spectral bandwidth is so wide (sometimes 100's of nanometers). If output beam quality isn't too important, you could use a long BBO crystal and the output would just be more like a long rectangular like output but it would be very choppy looking and not uniform in conversion efficiency....but if a fair amount of power is needed but it doesn't matter what the SHG beam looks like; it would be sufficient.
Thank you all for your precious suggestions, I hope I have got the answer.
we have a Ti:sa, 100 fs, 3 W average power, tunable laser from 690 nm to 1040 nm. and we wanted to generate a UV spectrum from around 350 to 400 nm, as I was not sure at which point to start with I have posted this question and at this moment we are not interested about the efficiency.
For your reference and so you don't have to buy as many nonlinear crystals:
Over the tuning range you mentioned, BBO would be the better choice as the internal phase matching angle goes from 23.2 deg to 34.3 deg. (LBO is 12.2 deg - 44.8 deg). What you would do in practice is pick a BBO with a phase matching angle in the middle of the range (i.e ~ 28.7 deg). For tuning you would still have to tilt the crystal quite a bit since the external angle tuning goes up more than the internal angle. Make sure you buy a crystal with a large enough aperture for tilting purposes over 20+degrees.
Also, you will probably want to focus your beam. But I would have to do some calculations based on your numbers. Since you aren't too interested in high conversion at this point, you could probably just use the size out of your resonator, but the results won't be stellar.
A great freeware program for conversion processes like this is SNLO. You can google this and get it for free. I ran some numbers for you. If you focus your beam to a 1/e^2 beam diameter of 300 microns and put it through a 5 mm BBO crystal phasematched properly, then you can expect a conversion efficiency of about 27%. If you use a 10 mm BBO crystal, you can expect ~ 48%. However, both beams will be elliptical and also be stretched in time to 1.2 ps (for 5 mm BBO) and ~ 2 ps (for 10 mm BBO). You may not be able to "recompress the beams" to 100 fs (I'm not sure though....that is one are I don't have much experience in...that is temporal compression ).
again if you do not care of either efficiency or beam shape try to use powder. to have less problems with 350nm end i would use fused silica as substrate. BTW, what is your rep-rate? SHG depends on peak power. The "pros" of using powder is that you have randomly oriented grains, so less sensitive to phase matching. With long crystals this will be an issue - you will have to precisely adjust the angle of the crystal with respect to the beam.
the cons are as mentioned: conversion efficiency will be lousy, and beam quality will be rather poor as well. BUT, if your peak power is sufficient, and all what you would like to do is to measure say SHG spectrum it will be enough.