laser crystals bonded with q-switch

[op37]

Hi friends,

I am new here. I've got a few laser crystals bonded with cr4+:yag on hand.



wanna make something fun with them... such as xenon-lamp pumped laser or diode pumped laser, OPO to 1550nm sth...

I will try to do some calculations. before that, does anyone here have experience on the pumping power required or structure or any other funny ideas?

Thanks and will post the progress,,

Phy

 

[Alaskan]

Damn, how nice, with a Q-Switch too. What are the rod lengths and diameters.

Edit: I see the length and dia in the photo now. I wonder if these are 808nm end pumped rods... output of 1064nm from what I see, rear HR mirror and OC already coated on the rods.

 

[op37]

The ND:YAG part is 3x3x35mm, the CR:YAG part is 3x3x3mm.

Yes it is coated on both ends. However I tried to pump it with 5W 808+/-2nm C-mount diode/FAC and focus lens and nothing out...:thinking:

So I am thinking about if to pump it with flashlight from camera first

 

[Alaskan]

Don't understand why high transmission coated for 808nm on the end if it isn't meant to be end pumped. Probably good for a mJ or more of output power. How are you testing for output power? The flash will be very low average power, but a short nanosecond pulse of high intensity.

 

[ultimatekaiser]

It likely still needs mirrors. the coatings are probably AR coatings. and its very likely a passive Q switch. not an active one.

 

[Alaskan]

I've never seen a YAG with the mirrors coated on them, if they were there would be no cavity for gain outside of the crystal itself, maybe the marking on the container specify the mirrors which should be used with it.

 

[op37]

I used a PIN diode based detector(mainly for pulsed laser diode), and then connected to a 500MHz(4GSPS) oscilloscope. Maybe it is not suitable. AM looking for a used Ophir sensor for that.

They should be supposed to be end-pumped, with rear side coated with 808HT and 1064HR. I am not sure whether the pumping power was not enough, or the spectrum is biased from 808nm due to temperature rise..

 

[ultimatekaiser]

I used a PIN diode based detector(mainly for pulsed laser diode), and then connected to a 500MHz(4GSPS) oscilloscope. Maybe it is not suitable. AM looking for a used Ophir sensor for that.

They should be supposed to be end-pumped, with rear side coated with 808HT and 1064HR. I am not sure whether the pumping power was not enough, or the spectrum is biased from 808nm due to temperature rise..

you can't end pump a crystal that long realistically without spending huge amounts of money (if at all). These were likely made to be diode pumped by a bar from the side judging from the shape. you could flash pump them too. but no way you'll be end pumping them. and there are some rods that do have mirror coatings on the ends, but its uncommon on large crystals. many are even just left un-coated entirely. just depends on how you want the laser to function.

 

[diachi]

It likely still needs mirrors. the coatings are probably AR coatings. and its very likely a passive Q switch. not an active one.

Can't take external mirrors, HR@1064nm on one end and PR@1064nm on the other. The HR end is also HT@808nm.

 

[ultimatekaiser]

Can't take external mirrors, HR@1064nm on one end and PR@1064nm on the other. The HR end is also HT@808nm.

Yeah i just saw the labels on the boxes. but you'd need a hella powerful pump to make that work. prepping a huge 808 to keep it then enough along the whole crystal would be fairly hard. Most companies don't end pump anything bigger than a few mm usually, but it is doable.

 

[Alaskan]

I have an end pumped YAG and it is only a very few mm long, so that fits.

 

[op37]

Thank you all. So these seem to be side pumped rods. i'll try to use flashlight first.

I have used 40W diode bar from ebay. however designing the constant current power supply seems to be a lot work...

Yes I have a Coherent laser head and its main crystal is so 2-3mm tiny... already with 10mj output and 5ns pulse width

I will post results later :thinking:

 

[Alaskan]

I have been looking at some of those rods being sold on ebay by a guy in Israel, but most of his rods need repair. I wonder what they were used in. Fairly obvious it may be, but I'm still trying to get a handle on YAG technology, bought some small YAG's but they were sent home while I am in Iraq.

 

[op37]

Do you want YAG only or with Q switch crystal? What's the dimension?

for Nd:Yag rod there are plenty of sources...

Rework of the crystals is expensive... i would rather buy a new used one

 

[op37]

Have built a simple setup using a camera flash.

The energy sensor hasn't been arrived yet. Still don't know if there is laser pulse coming out

 

[LSRFAQ]

Doing a little quick math in my head, and based on 27+ years of experience. Since it says 60% T on the OC coating , the transmission is way too high for that length of crystal, at amateur pumping conditions. You may need an external OC as well. 6 to 15% would have been believable. 60% T suggests upwards of 50-100 watts 808 side pump.

if you can find it, Silfvast's book "Laser Fundamentals" is a good one for beginners on calculating DPSS gain and mirrors... However since you do not know all the Q-switch characteristics, anything you do is an educated guess. If you look, each Cr:YAG crystal has a bit different doping. Which means this was an attempt to "dial in" a new design. These were research items, not a production item.

A 500 Watt Second camera flash is unlikely to lase these, you could start with an external long focal length OC of a few percent transmission. That forms a three mirror cavity, which is likely to have interesting side effects.

The fact that each box has a measured "T" penciled in suggests either problems in coating or QC.
Steve