I just thought I would put this idea out there in case anyone was interested in commenting or trying it. I have been trying to get into the DCG holography but the long coherence green or blue lasers needed can be difficult to come by.
There are companies like Ondax (
www.ondax.com) that sell volume holographic gratings for frequency stabilizing laser diodes. I think mostly their stuff is used at 405, 635, 650, 800 nm, etc. typical diode laser wavelengths. You place them at the output facet of the laser diode, or in the collimated beam of the laser diode to reflect narrowband filtered light back into the diode cavity and enhances a narrow linewidth.
I wonder if this idea would work to some limited extent with a cheap 532 DPSS source. When I tested the coherence length of a DPSS laser pointer it was not too good (as compared to say, a red laser diode at a stabilized temperature). I was thinking that perhaps a weak dichromated gelatin hologram could act as a volume holographic grating.
The idea would be to create a very thick emulsion (250 to 500 microns thick) of gelatin with a low concentration of dichromate in it. The optical density of the dichromate would be low to have weak volume scattering and not absorb the green light too much. The emulsion could be placed between two thin glass plates.
Then one could place the emulsion in front of a green DPSS laser. The facets of the glass from the emulsion would not reflect the beam back in the diode. A cube corner and a neutral density filter would be placed after the emulsion to temporarily reflect some light back into the diode comparable to what the feedback would be when the grating is developed.
The interference between the light returning from the neutral density filter/cube corner and the light passing forwards through the emulsion would form a reflection grating. This reflection grating would become self-reinforcing after its diffraction efficiency became strong enough because the backscattered light would itself interfere with the illumination beam, and the corner cube and neutral density filter could be removed.
This hologram would not be developed using alcohol as it would be important to prevent shrinkage of the hologram and shifting of the wavelength. Perhaps it could be fixed with heat after the dichromate ions were given a chance to cross-link in the dark.
Anyways, this might be a way to use DCG to help stabilize the lasers to make a laser better for DCG use that is accessible to DCG hobbyists.
Dan
I just thought I would put this idea out there in case anyone was interested in commenting or trying it. I have been trying to get into the DCG holography but the long coherence green or blue lasers needed can be difficult to come by.
There are companies like Ondax (www.ondax.com) that sell volume holographic gratings for frequency stabilizing laser diodes. I think mostly their stuff is used at 405, 635, 650, 800 nm, etc. typical diode laser wavelengths. You place them at the output facet of the laser diode, or in the collimated beam of the laser diode to reflect narrowband filtered light back into the diode cavity and enhances a narrow linewidth.
I wonder if this idea would work to some limited extent with a cheap 532 DPSS source. When I tested the coherence length of a DPSS laser pointer it was not too good (as compared to say, a red laser diode at a stabilized temperature). I was thinking that perhaps a weak dichromated gelatin hologram could act as a volume holographic grating.
The idea would be to create a very thick emulsion (250 to 500 microns thick) of gelatin with a low concentration of dichromate in it. The optical density of the dichromate would be low to have weak volume scattering and not absorb the green light too much. The emulsion could be placed between two thin glass plates.
Then one could place the emulsion in front of a green DPSS laser. The facets of the glass from the emulsion would not reflect the beam back in the diode. A cube corner and a neutral density filter would be placed after the emulsion to temporarily reflect some light back into the diode comparable to what the feedback would be when the grating is developed.
The interference between the light returning from the neutral density filter/cube corner and the light passing forwards through the emulsion would form a reflection grating. This reflection grating would become self-reinforcing after its diffraction efficiency became strong enough because the backscattered light would itself interfere with the illumination beam, and the corner cube and neutral density filter could be removed.
This hologram would not be developed using alcohol as it would be important to prevent shrinkage of the hologram and shifting of the wavelength. Perhaps it could be fixed with heat after the dichromate ions were given a chance to cross-link in the dark.
Anyways, this might be a way to use DCG to help stabilize the lasers to make a laser better for DCG use that is accessible to DCG hobbyists.
Dan