Laser pointer discussion. Read/write reviews of laser pointers and laser pointer companies. Learn about all types of laser pointers and lasers

One laser store meets all your needs

 Laser Pointer Forums - Discuss Laser Pointers Little help to understand SHG

06-01-2015, 12:18 AM #17
 Class 4 Laser Join Date: Feb 2008 Location: Yellowknife, NT, Canada Posts: 8,391 Rep Power: 72156
diachi
Class 4 Laser

Join Date: Feb 2008
Posts: 8,391
Rep Power: 72156
Re: Little help to understand SHG

Quote:
 Originally Posted by Alaskan I liked this article: http://photos.imageevent.com/qdf_fil...roject/nlo.pdf I'm searching for information regarding what happens if you use 810nm, or to throw a number out there, 815nm instead of 808nm, how far from 808nm can the pump be off wavelength/frequency into the vanadate and then KTP before the 532nm output either doesn't work, or begins to drop off by 10 percent? Which crystal suffers the worse conversion efficiency when off freq, the YVO4 vanadate or the KTP, or do they both have similar off-wavelength inefficiencies? Maybe I'm looking at this wrong, for example, if you shoot 1070nm into a LBO or KTP crystal you just end up with half the wavelength out or 535nm? Are all "532nm" DPSS laser pointers really 532nm?
From the Laser FAQ:

Quote:
 The absorption curve of Nd:YVO4 (vanadate) is quite broad compared to Nd:YAG (YAG). The following is from a graph in "Solid State Laser Engineering" by Koechner. (This actually deals with output power, not absorption, but since that is the desired effect, the numbers should be similar): Nd:YVO4: Between 806 nm and beyond 813 nm, the output power is approximately constant. The corresponds to a temperature range of 20 °C for the pump diode. The output drops to 50 percent at about 801 nm. (The graph doesn't go higher than 813 nm.) Nd:YAG: The peak is between 809 and 810 nm with the output power down by 40 percent at 807 and 810 nm. For pumping with diodes, the wider wavelength range of vanadate is very significant because temperature tuning is a lot less critical and for low power DPSS lasers such as green laser pointers, thermal management isn't essential (though some variation may still be evident).
I was just going to say "Vanadate has a wider absorption band than YAG" but thought some numbers would be nice, so dug that out!

Edit: Just realized you were asking about Vanadate vs KTP - the thing there is that the Vanadate will always output at 1064nm (assuming you're using optics for 1064nm) so that will not be an issue for the KTP. The issue comes from the diode's wavelength shifting and then causing the output from your Vanadate to drop due to reduced adsorption. Temperature is the biggest concern for KTP, even if the temperature is a degree or two out you can see a large drop in efficiency. You can also run into thermal lensing in your Vanadate and possibly to some extent in the KTP which causes overall efficiency issues in many designs. That can also cause a reduction in beam quality.

Yes, all of the 532nm lasers are 532nm within a very small margin.

__________________

405nm | Banggood LT-850 | "5mW" | Review Unit | Review WIP
445nm | Sanwu Laser Pocket Series | 400mW Metered
445nm | NDB7242E Pen Build | 60mW Metered | >>Build Thread<<
450nm | LaserPointerStore - Thor H2 | 1W(?) | Review Unit | >>Review<<
473nm | B&W Tek BWB-10-OEM | Ordered
488nm | Spectra Physics 163 Argon | ~30mW Metered
515nm | PL515 Pen Build | 50mW Metered | >>Build Thread<<
520nm | Laserlands 520 | 5mW | Review Unit | 3mW metered | >>Review<<
532nm | Gearbest 303 Pointer | 50mW Metered
532nm | Gearbest JD-850 Pointer | 30mW Metered (I think, need to re-test).
633nm | HeNe | 6mW
633nm | Spectra Physics 155 HeNe | <1mW >>Thread<<
650nm | Sanwu Laser Pocket Series | 200mW Metered
808nm | Melles Griot 532nm Lab Unit | No Crystals >10W | X2

Check out my Reddit Subreddit! >>/r/laserpointers<<

Last edited by diachi; 06-01-2015 at 12:26 AM.

06-01-2015, 01:35 AM #18
 Class 4 Laser Join Date: Jan 2014 Location: Currently in Iraq. Posts: 7,541 Rep Power: 86416
Class 4 Laser

Join Date: Jan 2014
Location: Currently in Iraq.
Posts: 7,541
Rep Power: 86416
Re: Little help to understand SHG

Thank you, I've been reading a few parts of Sam's Laser FAQ and must have overlooked that, did a google search and my search terms must have been bad not to pick up on finding the FAQ... excuses, excuses.. Anyway, that mystery is solved, I've been wondering on the question for awhile but keep forgetting to ask anyone, so today I tailed the question on to this thread. I have some Vanadate, a nice piece 10mm X 10mm X 1mm someone gave me as a gift and a KTP crystal wrapped in gold leaf I bought from someone but before I start doing anything with it, needed to know how temperature affected the materials.
__________________

The forum costs more to run than donations received, if you wish to help click this link: http://laserpointerforums.com/donations.htm

Laser Safety: http://www.laserpointersafety.com/index.html

Sam's Laser FAQ: Sam's Laser FAQ: Welcome Page

RHD's Relative Perceived Brightness Calculator. Compare brightness @nm: http://lsrtools.1apps.com/relativebrightness

To shorten my signature I have moved most of my laser related web links to this forum page, the second post in that thread shows most of my builds... Alaskan's Laser Links: http://laserpointerforums.com/f44/al...ml#post1449395

Sincerely investigate any of these three short quotes as new concepts and you've taken your first step into a larger world:

"I regard consciousness as fundamental. I regard matter as derivative from consciousness..." - Max Planck. "Everything we call real is made of things that cannot be regarded as real" - Neils Bohr. "What we call physical things and events do not exist independently of subjective experience..." - Deepak Chopra.

Each of these three rabbit holes go deep, ending up in the same place.

Useless troll fighting.
.........................
http://imgbb.com

High resolution of my avatar: https://ibb.co/fWOhXF

Last edited by Alaskan; 06-22-2015 at 05:55 AM.

 Tags dpss, ktp, shg

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

All times are GMT. The time now is 12:24 AM.

 -- DarkShadows V5 -- Responsive LPF -2562016 -- Default Style Contact Us - Laser Pointer Forums - Archive - Top