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ArcticMyst Security by Avery

laser crystals bonded with q-switch

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Not sure I am tracking, what are these little black pieces "8X8X4 and 8X8X5mm with initial T = 10%-14%" ?
 





op37

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This is just Cr:yag crystals....I guess they are for skin treatment machines
 
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ND:Cr YAG?

From Wikipedia:

Nd:Cr:YAG
YAG doped with neodymium and chromium (Nd:Cr:YAG or Nd/Cr:YAG) has absorption characteristics which are superior to Nd:YAG. This is because energy is absorbed by the broad absorption bands of the Cr3+ dopant and then transferred to Nd3+ by dipole-dipole interactions.[5] This material has been suggested for use in solar-pumped lasers, which could form part of a solar power satellite system.

What wavelength, any idea? I've been googling but it depends if ND:Cr:YAG or some other Cr:YAG. I might want some of those.
 

op37

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IMG_3225a.jpg

The output from Q-switch as two peaks. What might cause the first smaller peak?
 
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Wish I knew the answer to that. I cannot get that link to work for me, anyone else?
 

op37

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OK they sell varies crystals, mirrors, lens, prisms and active Q-sw. I am quoting diffusion bonded crystals from them - for Q-switched DPSS. You could let me know what you want in mind, as I can ask the seller for you. I live in China.

QQ??20170112183601.jpg
QQ??20170112183615.jpg
QQ??20170112183637.jpg
QQ??20170112183732.jpg
 

CurtisOliver

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Wow, the prices are very good. Is there a minimum quantity to buy, or can you just buy one off? :beer:
 

LSRFAQ

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Two pulses, with the first one being small, is probably due to lensing from self adsorption in the CR:YAG. First starts to bleach, then heats up causing lensing, adsorption, diffraction, or scatter, then finally fully bleaches and lases.

It is not uncommon to see poorly designed Q-Switched lasers "ring" with multiple short pulses or fire two or three times if the pump lamp has a long duration or too much energy... If the lamp pulse can still saturate the rod every 250 uSeconds or so, the laser will fire again.

It can also come from issues with the Q-switch holdoff. That multi-pulsing used to cause me all sorts of problems with adjusting drive voltage and intra-cavity polarizer angle alignment on EO Q Switches in the field...

The mode issue suggests problems with thermal lensing, wrong external mirror radius, or you will need a mode limiting aperture intra-cavity... We solved that problem using optics that have a Gaussian reflectivity pattern across the mirror, aka a "Bullseye" coating. I'm not sure you can get those in China yet..

Try shaping your lamp pulse with a small series inductor, which is almost always an air-wound coil say 5-6 cM in diameter with anywhere from three to twenty turns. IF you can adjust the lamp current for "critical damping" with a sharp risetime, you will get optimal power transfer in most cases. In which case you will probably find you need less lamps or less energy. Monitor the lamp with a photodiode, you will learn a lot. (Once you figure out how to keep the PD from saturating in those conditions)

Our systems had up to three flashlamps in series. However, that required "series injecton" triggering using a thyristor, a series inductor, and/ or a shunt diode with return capacitor to keep the trigger pulse out of the storage capacitors.

This is worthwhile reading:

http://www.orcontech.com/data/Perkin_Elmer_Flashlamp_catalog.pdf

Congrats on getting these lasing, I feared you had bought some expensive paperweights...




Steve
 
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LASERFAQ said:
It is not uncommon to see poorly designed Q-Switched lasers "ring" with multiple short pulses or fire two or three times if the pump lamp has a long duration or too much energy... If the lamp pulse can still saturate the rod every 250 uSeconds or so, the laser will fire again.

It can also come from issues with the Q-switch holdoff. That multi-pulsing used to cause me all sorts of problems with adjusting drive voltage and intra-cavity polarizer angle alignment on EO Q Switches in the field...

This was what initially came to mind for me. Thanks for your input Steve...helpful as always.
 

op37

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Thank you Steve. I just measured the timing of the flash lamps (two lamps with same trigger)...

IMG_3227a.jpg

QQ??20170113124008.jpg

I am trying to adjust them and will post the results.

I haven't used external mirrors in this experiment. Just with the coatings of both sides of the rod (S1: HT@808, HR@1064; S2: PR=60% @1064)

To CurtisOliver:

I think I need to quote for the prices of items. For now I am quoting for a microchip of (Nd:Yag + Cr:Yag 0.4mm+0.2mm with coating mirrors)
 

op37

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I tuned the schematics and configs. The best result so far was using 4 caps of 240uF/330V each lamp, two caps connected in series to form 120uF/660V caps and two sets of them in parallel. So total caps in each lamp is 240uF/660V. Coil was added in series. It slowed down the rising edge a bit. But no big impact for lamp pulse width. In the following result the coil was not connected. Voltage added was 600V.

Lamp pulse:
lamp_??.jpg

Experiment config:
IMG_3292_??.jpg

with initial T=60% Cr:Yag rod
IMG_3293_??.jpg
IMG_3295_??.jpg

with initial T=55% Cr:Yag rod
IMG_3296_??.jpg
IMG_3299_??.jpg

The beam pattern shot on an undeveloped film:
IMG_3311_??.jpg

The transverse mode is still 11.
According to the Lidar equation, the PIN diode sensitivity and distance, the output beam power is estimated to be tens of kW.
 
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