PBS cube, or diode anomaly?? ML501P73

[JLSE]

I tried passing a 500mW mistu. diode through a PBS cube that was bought for 445nm.
Odd thing is, when I rotate the diode, within a full turn, the power does not drop and the
the beam goes straight through. I have never seen this and cannot find any info on it.

Theres a 10% loss through the cube but pointless if I cant combine.. Any thoughts?

*EDIT Forgot to add, ive tried various wavelengths on different cubes. Is the diode
causing this, or do some cubes behave this way? All optics I have fiddled with in the
past and over 7 or so years, not once have I seen this, until now that is.. :undecided:

 

[Bionic-Badger]

It may be that the polarized beamsplitting coating between the two prisms really is suited for only a specific range of wavelengths, not for broadband.

Try looking through the cube and see what wavelengths it reflects from a white light source.

 

[djQUAN]

same thing I experienced when I shone the 450nm pen to a PBS from a DVD burner. The cube doesn't seem to do anything to the beam. I haven't tried a red though.

 

[JLSE]

It may be that the polarized beamsplitting coating between the two prisms really is suited for only a specific range of wavelengths, not for broadband.

Try looking through the cube and see what wavelengths it reflects from a white light source.

Makes sense, and overlooked that. I guess playing with too many cubes from sled
optics put the confidence of broadband coatings in my mind. I shone a white light
and got a purple which looks close to AR for red lol :thinking:

 

[Bionic-Badger]

Yeah, I thought they were broadband-ish as well, but it makes sense that the polarization reflection layers are wavelength specific too. Maybe that blue/purple you see are the wavelengths it affects. There are some cheap ~635nm PBSes on eBay you can use too.

 

[Meatball]

How sure are we that the output of all of these blue diodes is polarized?

Sure, maybe some have been - but are just assuming they are?

 

[BShanahan14rulz]

Glan?Taylor prism - Wikipedia, the free encyclopedia

Just a guess here, but assuming our typical PBS cubes are these, or even the cemented variant, the refractive change at the gap is what splits the beam, and to make this suitable for a particular wavelength, that gap is what is adjusted by the prism manufacturer. They are somewhat wavelength specific, is a property of how they work.

 

[Cyparagon]

How sure are we that the output of all of these blue diodes is polarized?

I think all edge-emitting laser diodes are polarized.