Holographic gratings made with my 405nm diode on dcg
Holographic gratings
Holographic gratings
Danny, do a single beam reflection and I can tell you exactly what is happening but it looks to me like a mode hop.
Holographic gratings
ok i will make coat more plates and run test, thanks Colins, if i run current to the diode on the low side wount i get less chance of mode hopping?
Holographic gratings
What is the geometry of the set up? Can't rule out extremely short coherence yet, nor movement of the plate.
Holographic gratings
The photos show setup one, on setup 2 they are the same except the gaps or bands are closer together, and the color bands are larger
Holographic gratings
The banding might be from lack of coherence. Notice the reflected beam path is definitely longer than the staight through. Sometimes short coherence lengths repeat themselves, so that there is interference, then none, then back again. And this would sort of make sense in your two configurations, with the path length differences being smaller in the lower figure than the bottom.
Try putting the laser on a Michelson Interferometer and see what you get, and/or trying a geometry where path lengths can be easily equalized.
Try putting the laser on a Michelson Interferometer and see what you get, and/or trying a geometry where path lengths can be easily equalized.
Holographic gratings
yes i will do that, and get back to you EdEd Wesly wrote:The banding might be from lack of coherence. Notice the reflected beam path is definitely longer than the staight through. Sometimes short coherence lengths repeat themselves, so that there is interference, then none, then back again. And this would sort of make sense in your two configurations, with the path length differences being smaller in the lower figure than the bottom.
Try putting the laser on a Michelson Interferometer and see what you get, and/or trying a geometry where path lengths can be easily equalized.
thanks Ed good info, hope my spelling and grammar is getting better and easy to read and understand.
Holographic gratings
ED if it is a very short coherence length couldnt i use it for contact copies ?Ed Wesly wrote:The banding might be from lack of coherence. Notice the reflected beam path is definitely longer than the staight through. Sometimes short coherence lengths repeat themselves, so that there is interference, then none, then back again. And this would sort of make sense in your two configurations, with the path length differences being smaller in the lower figure than the bottom.
Try putting the laser on a Michelson Interferometer and see what you get, and/or trying a geometry where path lengths can be easily equalized.
Holographic gratings
Even with most mode hops a laser can be used for contact copies. It really takes a pretty wide line to erase a contact copy.