by Erik » Fri Oct 29, 2021 11:10 pm
Alright, two 10x12 (8x10 effective after edges are cut off) mold-coated sheets are in the refrigerator. I would usually make more for a weekend session but this is experimental, and I want my thick rain-X plates back to make regular DCGs for sale.
My 405 nm laser is a homemade ECDL which was operating well at the electronics bench, but became misaligned when bringing it into the laser room. Attempting to realign it was not immediately successful and I had limited time today so wanted to move on to making emulsion and plates. I also do not yet have a dichroic mirror for this wavelength yet (coming soon from ebay) to make it colinear with the other lasers and direct it through the same spatial filter. My table and especially the shutter depends on this so I want to complete it before using the 405.
I too suspect 405 is underrated for display work. My exposures in standard DCG with the 445 and 488 are easier to make bright gold than anything else, and this represents a rather large redshift from the recording wavelengths. It would seem that 405 would tend to produce great bright green replay under the same conditions. As we know, green is the most visible at equal power.
With that in mind, I have the 445, 488, and 568 all aligned and ready to go. The 445 is a commercial ECDL with an asymmetrical beam, but the other two are Sapphires and give excellent even (gaussian) exposure.
This brings me to a question I have had for a while - when beam exposures are quoted in mW/cm^2, how is this calculated with a beam intensity that is not uniform across the entire plate? Quote for a single point and measure the properties at that point in the finished hologram?
The emulsion and prep were as follows, largely following my typical DCG workflow:
11 g gelatin (Superclear 300 bloom, from Amazon)
80 mL DI H2O
Stir, soak until water is absorbed. Heat to 60 C with magnetic stirring. Keep beaker covered with new plastic sandwich bag to exclude dust.
Speedball diazo sensitizer - comes as a viscous dark liquid inside an empty-feeling bottle. Filled 3/4 full with DI water as per instructions.
Added 1.0 mL prepared diazo sensitizer. pH was almost unchanged upon addition of diazo sensitizer: 5.40 before, 5.35 after. Probably within the noise of my meter.
Added 1.0 mL of 1% safranin O - because the 405 was not going to be an option for this weekend, I wanted to have a higher chance of success. The absorption of safranin at 445 is relatively low, hopefully results will still allow some conclusions. pH still 5.35.
Turned off stirring to allow bubbles to rise
Cleaned 10x12 glass sheet with non scratch pad, hot water, and my favorite mix of laundry detergent, oxi-clean, and TSP. Rinsed with DI water, making sure the water break test passes. Applied two strips of tape to each long edge. Scotch transparent for one, Scotch "super hold" for the other. I prefer the "super hold" tape but nearly ran out on the first plate. ...think ahead next time...
Cleaned thick glass previously coated with rain-X following same procedure. Dried both sheets with microfiber cloth then wiped with lint-free cleanroom wipe.
Sheets into the (holography dedicated, filtered air) food dehydrator at 130 F. Loaded 20 mL emulsion into syringe.
Removed warmed plates, placed upon prepared paper towels on a level surface. Applied emulsion in a "T" pattern
Lowered upper plate (thick rain-X glass) onto lower (clean) plate. Allowed emulsion to fill the entire surface. Applied binder clips to the long edges.
Placed in (dedicated, non-food) refrigerator for overnight gelling. Stored diazo in the fridge as well.
I checked an aliquot of the emulsion after coating the first plate and noted it was fairly faintly colored. Added a second 1.0 mL of 1% safranin to the remaining emulsion and mold coated the second plate following the first. Plate 1 had the super-hold tape and so will be a thicker layer.
I used to add glycerol (around 1% of final volume) to my DCG emulsion but found I got much better storage if this was omitted. Plates would undergo quite a bit of dark reaction overnight, and be nearly unusable after two days dry at room temp, even in darkness. With so many possible variables, it's difficult to say this was certainly the cause but it seems likely at this point.
I work my regular job Tues-Sat but will have some time after work to demold, dry, and cut up the plates.
I'm thinking just making some plain gratings with each laser to begin with.
I will update with observations. Thanks for the collaboration, this is exciting!
Alright, two 10x12 (8x10 effective after edges are cut off) mold-coated sheets are in the refrigerator. I would usually make more for a weekend session but this is experimental, and I want my thick rain-X plates back to make regular DCGs for sale.
My 405 nm laser is a homemade ECDL which was operating well at the electronics bench, but became misaligned when bringing it into the laser room. Attempting to realign it was not immediately successful and I had limited time today so wanted to move on to making emulsion and plates. I also do not yet have a dichroic mirror for this wavelength yet (coming soon from ebay) to make it colinear with the other lasers and direct it through the same spatial filter. My table and especially the shutter depends on this so I want to complete it before using the 405.
I too suspect 405 is underrated for display work. My exposures in standard DCG with the 445 and 488 are easier to make bright gold than anything else, and this represents a rather large redshift from the recording wavelengths. It would seem that 405 would tend to produce great bright green replay under the same conditions. As we know, green is the most visible at equal power.
With that in mind, I have the 445, 488, and 568 all aligned and ready to go. The 445 is a commercial ECDL with an asymmetrical beam, but the other two are Sapphires and give excellent even (gaussian) exposure.
This brings me to a question I have had for a while - when beam exposures are quoted in mW/cm^2, how is this calculated with a beam intensity that is not uniform across the entire plate? Quote for a single point and measure the properties at that point in the finished hologram?
The emulsion and prep were as follows, largely following my typical DCG workflow:
11 g gelatin (Superclear 300 bloom, from Amazon)
80 mL DI H2O
Stir, soak until water is absorbed. Heat to 60 C with magnetic stirring. Keep beaker covered with new plastic sandwich bag to exclude dust.
Speedball diazo sensitizer - comes as a viscous dark liquid inside an empty-feeling bottle. Filled 3/4 full with DI water as per instructions.
Added 1.0 mL prepared diazo sensitizer. pH was almost unchanged upon addition of diazo sensitizer: 5.40 before, 5.35 after. Probably within the noise of my meter.
Added 1.0 mL of 1% safranin O - because the 405 was not going to be an option for this weekend, I wanted to have a higher chance of success. The absorption of safranin at 445 is relatively low, hopefully results will still allow some conclusions. pH still 5.35.
Turned off stirring to allow bubbles to rise
Cleaned 10x12 glass sheet with non scratch pad, hot water, and my favorite mix of laundry detergent, oxi-clean, and TSP. Rinsed with DI water, making sure the water break test passes. Applied two strips of tape to each long edge. Scotch transparent for one, Scotch "super hold" for the other. I prefer the "super hold" tape but nearly ran out on the first plate. ...think ahead next time...
Cleaned thick glass previously coated with rain-X following same procedure. Dried both sheets with microfiber cloth then wiped with lint-free cleanroom wipe.
Sheets into the (holography dedicated, filtered air) food dehydrator at 130 F. Loaded 20 mL emulsion into syringe.
Removed warmed plates, placed upon prepared paper towels on a level surface. Applied emulsion in a "T" pattern
Lowered upper plate (thick rain-X glass) onto lower (clean) plate. Allowed emulsion to fill the entire surface. Applied binder clips to the long edges.
Placed in (dedicated, non-food) refrigerator for overnight gelling. Stored diazo in the fridge as well.
I checked an aliquot of the emulsion after coating the first plate and noted it was fairly faintly colored. Added a second 1.0 mL of 1% safranin to the remaining emulsion and mold coated the second plate following the first. Plate 1 had the super-hold tape and so will be a thicker layer.
I used to add glycerol (around 1% of final volume) to my DCG emulsion but found I got much better storage if this was omitted. Plates would undergo quite a bit of dark reaction overnight, and be nearly unusable after two days dry at room temp, even in darkness. With so many possible variables, it's difficult to say this was certainly the cause but it seems likely at this point.
I work my regular job Tues-Sat but will have some time after work to demold, dry, and cut up the plates.
I'm thinking just making some plain gratings with each laser to begin with.
I will update with observations. Thanks for the collaboration, this is exciting!