homemade 488nm direct doubled laser

[shrad]

I'm currently working on my 488nm direct doubled laser

I have made the diode mount so far, and I'm going to test collimation and beam correction

some pics to come tonight, and, I hope, the first blue photons!

[ElektroFreak]

What are you using for SHG?

[shrad]

a KNBO3 with AR coatings @ 976nm, 2*1.8*5mm

I have problems with the diode mount, I might need to machine one to my needs, as for the lens and cristal holders

I fear the moment when I'll mount the KNBO3, dur to its poor resistance and moisture sensitivity

my hairs are already starting to fall :P

[gogu]

Hi Shrad, how about a 3-axis stage, maybe 2 or 3 of them actually for the diode, kbo and oc.
You got an ir viewer to see the path, mode shape size etc?
good luck


Cheers

[shrad]

hi go!

I have a webcam which views IR nicely but it saturates when viewing the focused spot

anyway, I think the original focusing lens for the "dead" cristalaser unit (I kept all te components into gel-paks, don't worry ) is not of correct coatings for 980nm and I'll have to test a few lenses I have laying around

what worries me is my OC, as I have no clue what the ray of curvature might be, so that's not easy to set it up correctly

I think I'll have to get some mounts machined to have the diode well positioned and for everything to be in the correct axis

I also have to design a PSU for my little HeNe tube, to be able to align all these things correctly

if anyone has hints about how to measure ROC of an OC, please tell me, so I can lay up some drawings and see how I'll have to lay out things

[weartronics]

if anyone has hints about how to measure ROC of an OC, please tell me, so I can lay up some drawings and see how I'll have to lay out things

I think the most suitable technique is described in a paper: Maxim Spiridonov and David Toebaert, "Simple yet accurate noncontact device for measuring the radius of curvature of a spherical mirror," Appl. Opt. 45, 6805-6811 (2006). Sadly, I can't find my copy of this paper and I don't have access to the electronic journal any more, but I will try to describe the technique as best I can.

Take a digital camera (or a video camera) and point it directly at a plane mirror a known distance away. I attach the camera to a stand where the camera points vertically down and the mirror lies flat on the table, but you can use any rig in your shop. Zoom in the camera so that the mirror fills most of the image.

In the image from the camera, you will see the camera body reflected in the mirror. If you place a large diameter and high contrast ring around the camera lens, you will have a good target to measure in the image. I used a CD which has a white surface. Of course, It works best if you illuminate the target, not the mirror.

First, measure the diameter of the target in real life (millimeters), then measure the diameter of the target in the camera image (pixels). With this information, and the distance between the camera and the target (which is twice the distance between the camera and the mirror), you can calculate the scale factor of the camera system.

Then, replace the plane mirror with the unknown spherical mirror at the same distance, and measure the diameter of the same target in the image. With trigonometry, you can calculate the ROC of the mirror with good accuracy. From memory, the paper includes the equations to do the experiment without having to think about it very much!

Of course, this technique works best with broadband mirrors. But with good illumination, it can work with single-wavelength dielectric mirrors too. I even managed to measure 1064nm HR and OC mirrors this way. If the target has high contrast, you can still see the outline.

[weartronics]

I think I'll have to get some mounts machined to have the diode well positioned and for everything to be in the correct axis

If you do this, will you design the mount for a C-mount diode, instead of the CT-mount diode that CrystaLaser user? I know that the CT-mount has the screw on the top, but the C-mount diode is much easier to buy. I'm considering to make a similar mount too.

[sugeek]

If you do this, will you design the mount for a C-mount diode, instead of the CT-mount diode that CrystaLaser user? I know that the CT-mount has the screw on the top, but the C-mount diode is much easier to buy. I'm considering to make a similar mount too.

If you get these milled make a few extra, I know a few others would like one including me!

-Adam

[shrad]

ok, so these crystalaser are a top laser to design DPSS from scratch

the thing is I'll probably have to design everything myself, and there are many chances I don't use the beam axis height originally intended for the crystalaser setup

however, if someone has time and will to design some mounts, at crystalaser dimensions, for a c-mount laser diode, maybe some lenses (with dimensions set for thorlabs 5mm lenses would be a good choice I think) and standard OC mirror dimensions, I'll take some!

I might also go the way of the HeNe laser to get the OC ROC, pointing to the right and left sides of it and marking the point where the beams are crossing, and I should have a good measurement (anyway the ROC should be a round measure, metrics or inches, so the nearest round measure would be assumed to be the real one)

anyone has a hint on what to use to glue that KNBO3? it is 2*2*5 but highly hygroscopic, so what I did is pushing it into a mount with a copper foil and indium foil under it, but I'd like to be able to use that crystalaser KTP mount, as it is TEC-enabled

[mixedgas]

Get a diffuse green source, ie dpss aimed at card or a filtered mercury lamp. Set known optical flat on the mirror. Illuminate with the green, count the fringes.

I bullied Sam into posting the math in the FAQ.

Steve