PBS cube uses

[kecked]

Ok I have a very simple question. I am almost embarrased to ask. If you have a pbs cube make for a certain wavelenght, does that only refer to the reflected beam? IE if I pass a red laser through a blue cube will it be passed and allow you to combine the blue laser with any other color? Thus it is only the right angle beam that is affected by the surface coating. This seems to be the case since most pbs cubes look clear when you look through them and show color only on two faces. I know this sounds simplistic but I really never thought about it.

[-bart-]

"Good" pbs cubes have ar coated out-sides for the specified wavelenght and a beamsplitting coating usually optimized for reflecting the TE component of the wavelenght.

TM transmission is "bad" for the specified wavelenght, and even worse for other colors.

[kecked]

I am still confused. So I do understand that all the good cubes are ar coated. Most likely MgF2 and that the inter 45 sufrace is coated to reflect the chosen wavelenght. All good so we know that the cube surface will pass most wavelenghts efficiently and that the 45 surface will reflect the beam out the from of the cube. So what I am asking is if you pass a beam of any other wavelenght straight through the cube and not on the 45 side coated for the reflect wvelenght will it pass through the cube except for the small absorption of the glass. The wavelenght that the center 45 is coated for must also pass the wavelenght it is coated for or no one could use it to combine beams. I also understand that the polariztion of the pass through beam must be so that it matches the cube.

Is this all ok or did I miss something. This is the staus of my understanding. Am I correct?

Here is why I ask. I have a dichro combined beam where I lined up the polartizations of both beams (638nm and 520nm) that I want to pass into a pbs cube to combine a wavelength(450nm) that I do not have a dichro( no dichro passes 520nm and 638nm while reflecting 450nm. The transisiton is right in the middle around 520nm and angle tuning doesn't work for my application) for but I do have a cube designed to reflect 445nm on the 45 surface. Will this work efficiently or will loss be very high. I did try it and it seems to work but I don't have a power meter so I don't know how bad my final loss is on the combined beam.

[-bart-]

If the cube is intended for 450nm, I would expect :
for 450nm reflection : 1-3% losses
for non 450nm transmission : 10-50% losses.

For a boadband PBS, I would expect :
for 450nm reflection : 5% losses
for non 450nm transmission : 10% losses.

[kecked]

That helps a lot. Anybody got 15mm broadband PBS cubes for sale? I had gotten some in a group buy but was too nice and gave them all away.

[-bart-]

15mm ??
You're all single mode, no beam should ever be bigger than 6mm.

You're sure you've taken a look at argon stock dichros? They should be designed for ~514nm.

[kecked]

The older dicro for argons combined the 632 with the already combined argon beam. Once I combine the red and green, a dichro the reflects the blue cuts off the green and passes the red. what I really wanted to do was put he red first then combine the blue and then add in the green to keep loss down on the precious green. Didn't work with any dichro I could find but I did have a special run that was suppost to work but did not the works well to combine the green and red. So now I have an issue of finding dichro that reflects blue and passes green and red. No go again so I am resorting to a PBS cube. I meant 10mm not 15mm. anything smaller is too small for my chunky fingers.

[swamidog]

how about these?

http://www.ebay.com/itm/Dichroic-Mir...item256f8a526c
http://www.ebay.com/itm/Dichroic-Mir...item483f36287b

I am still confused. So I do understand that all the good cubes are ar coated. Most likely MgF2 and that the inter 45 sufrace is coated to reflect the chosen wavelenght. All good so we know that the cube surface will pass most wavelenghts efficiently and that the 45 surface will reflect the beam out the from of the cube. So what I am asking is if you pass a beam of any other wavelenght straight through the cube and not on the 45 side coated for the reflect wvelenght will it pass through the cube except for the small absorption of the glass. The wavelenght that the center 45 is coated for must also pass the wavelenght it is coated for or no one could use it to combine beams. I also understand that the polariztion of the pass through beam must be so that it matches the cube.

Is this all ok or did I miss something. This is the staus of my understanding. Am I correct?

Here is why I ask. I have a dichro combined beam where I lined up the polartizations of both beams (638nm and 520nm) that I want to pass into a pbs cube to combine a wavelength(450nm) that I do not have a dichro( no dichro passes 520nm and 638nm while reflecting 450nm. The transisiton is right in the middle around 520nm and angle tuning doesn't work for my application) for but I do have a cube designed to reflect 445nm on the 45 surface. Will this work efficiently or will loss be very high. I did try it and it seems to work but I don't have a power meter so I don't know how bad my final loss is on the combined beam.

[kecked]

That looks interesting but I've been fouled before and the transition is right on the 520nm line. Cheap enough to try it though but if it works I can never be sure I can get more.

[mixedgas]

Kecked,

The cube I want you to try is in the car, at lot 54. I'll try to get it to you in the morning. My day is way behind because of all these alarms going off.

Steve