Pumped 10 Watts into blue DPSS.

[blrock]

I bought this cool little blue DPSS module on ebay. It has all optics, TEC etc.

Problem is that I pumped 4 watts(recommended max input) and got no result.

Then I cranked it to 10 watts. This produced a little blue. Probably less than 3mw.

My million dollar question to my fellow LPF experts is:

The 808nm is coming out of a fiber, This I focus to a dot with a lens straight into the HR mirror. Do I first have to collamate the 808nm beam then focus it to a dot?

Thanks!!!!

 

[Prototype]

Huh. There are a few possibilities, and I'm going to go with the two nagging me the most:
1. The TEC isn't on or set to the proper temperature
2. Misalignment

Other than that, try moving the 'dot' from your 808 around on the crystal face, I'll think on this some more throughout today and let you know if I can think of anything else.

 

[blrock]

Thanks for the reply. I didn't connect the TEC as I was pulsing the 808nm laser to prevend heat build up. I moved the dot around the HR mirror(it has external mirrors) for about 30 minutes without much luck. The unit is pretty solid so I'm confident everything is still aligned.
I'll take some pics of the unit later and upload

 

[BKarim]

i'm not an expert but i think the 808nm pump must be focused on the middle of the crystal, not on the mirror

 

[blrock]

Hi BKarim,

If I were to focus on the crystal this would block the path. This is not a DPM module. as found in laser pointers. It has a HR and HT mirrors.
ie:
HR mirror, Nd:YAG, BBO, HT mirror


Anyother ideas?

 

[BKarim]

"this would block the path"
you mean that you must place the 808nm diode within the cavity?

if so, maybe you have to collimate the 808nm beam.
or perhaps you have spherical mirrors that acts like focusing lenses ?

 

[Things]

If you are running it through a fiber, you mess up the polarization of the diode completely. My understanding is you need polarization for the highest efficiency.

 

[bobhaha]

How trust worthy is the output of the 808? From what I have read, many crystals are very sensitive to shifts in wavelength and must have a very specific range in which the pump diode must operate, otherwise doubling will not occur. As far as I know the major shift is due to temperature, and can shift up to 0.5nm per degree +/-.

 

[goninanbl00d]

How trust worthy is the output of the 808? From what I have read, many crystals are very sensitive to shifts in wavelength and must have a very specific range in which the pump diode must operate, otherwise doubling will not occur. As far as I know the major shift is due to temperature, and can shift up to 0.5nm per degree +/-.

Not only that, YAG (which is used for DPSS blue) is extremely sensitive to wavelength.

The output of the diode has to be centred on 808nm exactly.

Even variations of 1nm or more will have an adverse effect on efficiency. They're already horribly inefficient to begin with, and a change in diode pump frequency will make a big difference.

Most cheap diodes and diode bars tend to vary quite a bit in wavelength, with some being as high as 820nm (which is garbage for DPSS pumping).

Also, as bobhaha said, the output frequency will go for a walk with changes to temperature. The pump should be TEC stabilized for optimal performance.

 

[ElektroFreak]

There are diode wavelength and crystal temperature sensitivity issues, as well as possibly polarization (although I'm not 110% certain of that and I'm not at home right now so no time to dig), and they will pose problems here, but I do think that if that laser was intended to be pumped from the rear the HR mirror should be HT@808nm. If rear pumping, the 808nm light should be focused to a point *just beneath* the rear surface of the YAG crystal. It sounds to me like your laser should be side-pumped... but what is really needed here are pictures of your cavity.

 

[FrothyChimp]

Linear resonator, end pumped SHG lasers require the 808nm pump diode to be focused within the Nd:YVO4 or Nd:YAG at a specific point based on the curvature of the OC mirror so that it is reflected back down through the waist. You will only use a small cross section of the lasing medium for stimulated emission. Generally the HR is flat but the OC mirror is curved to prevent walk off. Because of the curvature you not only have to align the mirrors but the distance between the mirrors and media has to be right along with the proper focal length into the media from the pump diode. My books on resonator design are at work so I can't give you the equations but you might be able to find info on the net about linear design.

Furthermore, you are using a using a minor lasing line to frequency double which is even more difficult to align and even generate. If the LBO or BBO is integrated you are set but if not you have to orient the NLO in a very specific angle and on the right face to phase match and generate blue.

 

[Prototype]

I'm more than 90% sure this is a crystal set from a 10mW APC regulated 473nm CNI labby, the ones rebranded by B&W Tek, eBay seller Holokidd has been selling them for a while. It's possible he bought the bad ones and parted them out? :thinking: In this setup, there is a 2W 808nm c-mount is pumped through a beam correcting prism set and then hits the HR mirror of the cavity. (I've seen one other person selling these sets, but I believe he only had one)

 

[blrock]

I'm more than 90% sure this is a crystal set from a 10mW APC regulated 473nm CNI labby, the ones rebranded by B&W Tek, eBay seller Holokidd has been selling them for a while. It's possible he bought the bad ones and parted them out? :thinking: In this setup, there is a 2W 808nm c-mount is pumped through a beam correcting prism set and then hits the HR mirror of the cavity. (I've seen one other person selling these sets, but I believe he only had one)

Actually you 100% correct.

Mmmm, this sounds like much more work to get this thing lasing than I thought. I pulsed 10watt into a DPM crystal and got HUGE amounts of green light. No fuss. Easy setup.

I have some c-mounts lying about too. The correcting part will no doubt be challenging.
If it wasn't for the many 1 watt 445nm blues I have, I probably would have been working on this 473 24/7

Thanks all for the input

 

[MarioMaster]

You may have already killed the coating on the crystals, IIRC a member over at PL did some power experiments with them and the coatings fried at about 6 watts or so.