405nm Dichro's

[kecked]

I did not know you were doing a run of 405nm pbs cubes plus the dichro.
I am already on order for the dichro. Please add me for the 405nm PBS.

[mophead]

I did not know you were doing a run of 405nm pbs cubes plus the dichro.
I am already on order for the dichro. Please add me for the 405nm PBS.

I'm in for 1 pbs cube too, please.

[bridge]

oh, Rob
here we received at least 15pcs order by others, please consider.thanks.
Best regards!
Bridge

[stanwax]

OK Bridge I will do
I have mailed my order of dichros to Sunbear and have added extra for myself for stock

Rob

[bridge]

OK Bridge I will do
I have mailed my order of dichros to Sunbear and have added extra for myself for stock

Rob

Hi Rob,
the 405nm dichroic had shipping to you today, please check it.
yes, all of you can received your orders soon.
sure, the 405nm PBS will finished next week.
Best regards!
Bridge

[mccarrot]

Are dichro affectde by polorsation of the lasers? in other word is there a up or down side on the dichro's?

I have seen in other forum where polisation is increasing the effincy from 75% to 95%

[kecked]

I just saw your question. Here is a possible answer. You AR coat one side so that you don't suffer from the reflection of the substate itself as the pass through beam enter the dichro.

Thus for the 405nm dichro, the AR coat would be 700nm-460nm and the reflect side would be coated to reflect 460nm-400nm. If you don't AR coat the back, then you will have some lose. How bad the lose is I can't really say.

[stanwax]

As far as Im aware the dichos should not be affected by polarisation or rather they do not care about the polarisation of the beam

Rob

[bridge]

Are dichro affectde by polorsation of the lasers? in other word is there a up or down side on the dichro's?

I have seen in other forum where polisation is increasing the effincy from 75% to 95%

if coating only consider one polarization, the laser polarization will much affect the effiency.
for this coating most are large inject degree, just like 60 degree not 45 degree, if we coating P polarization pass, and you need P polarazition laser to make best transmission.
but now, most laser are had both S,P polarizations(especially for combine with PBS), the coating should consider both S,P polarization, which is more difficult than only consider one, but transmission will be little lower than the only one polarization dichroic.
just say, only P polarzation consider dichroic maybe transmission P polarization >95%, S polarization maybe only 50% pass, so if you had one laser P:S>100:1, you transmission is about 95%, but if you had one S:P=1:1, oh, my god, maybe you loss 25%, for consider both S,P polarization, maybe both of S,P >90%, so whatever polarization laser you had, the total transmission are >90%, .
wish that will be help you understanding, thanks.
Best regards!
Bridge

[mixedgas]

Yes, dichroics are somewhat sensitive to polarization, if you go look at a major optics producer's catalog, a high quality broadband dielectric mirror (basicly a 0 transmission dichro in structure) will say some thing like 99.5% S incidence, , 98.2 % P or similar. Transmissive dichroic structures are worse in this respect.

Dichroics are by definition angle sensitive, and some times not being at the design angle can hurt you. Response shifts in wavelength as roughly the cosine of the error in angle. So a 635 nm dichro @ 10 degrees off axis shifts its center wavelength to 625 nm or so in one direction and 645 nm in the other direction. ie cosine 10 = .984 so .984 * lambda = new wavelength

As Bridge pointed out, they designed the dichro to be less angle sensitive, by changing some of the coating layers to slightly different design wavelength, and this is to your advantage. Remember folks your trying to cover almost a octave in frequency span from say 390 to 700nm, and that's not easy.

Also remember in a big coating run, the dichros are at the top of the vacuum tank, and the materials used in coating are at the bottom, forming a point source. The Dichros are usually on a spinning platter to try to even out the coatings , but a dichro blank on the outside of the platter might still get a little less material
for each of the 10-20 layers applied then one in the center,so there are slight differences in each final product. So there is some art in the chamber design and use. Dichros coated on one big blank use other techniques to even things out.

It costs the same to do a test run as it does to do a production run, and maybe you can only cycle the chamber twice a day, that's why these are so expensive to make in small quanities. 30$ for a prototype dichro is a steal.

The real loss on a low cost or surplus dichro is a lack of AR coat on the back side. For simple lead glass, thats a 4-5% fresnel (pronounced FRE-NELL) reflection at the air glass interface. A basic coat gets that down to 1.0 % or better. A really good multilayer ar coat gets that down to .01% or better.

So when launching a new dichro I try to both tilt and rotate it while watching a power meter or photocell, your eye isnt good enough to find the peaks. And yes, get out a protractor when laying out the new projector, and remember the mm1s dont pivot around their mounting points, they rotate around a point offset from the center of the mount. That can add cumulative error. I once had a split blue pass green that was coated for 45' that worked best at 36', so sometimes errors happen.

Steve