A while back, I got a 95mW Aries green handheld laser from LaserGlow. It worked great for several months, until I got it wet during a field training exercise (I'm in the US Army) and the key switch got some internal corrosion and died. I decided to disassemble and repair it myself, but during the process, I tweaked the crystals out of alignment and instead of a single beam I had a row of dots and a significant drop in power. After tweaking the set screw adjustments in the OC/crystal housing, I was never able to get rid of the "row of dots" effect and decided to bite the bullet and take the entire crystal housing apart and start from scratch. The problem I have now is that I can't get any green light output.
I have everything apart except the 2 screws that mount the brass plate holding the vanadate crystal to the pump diode heatsink--they are glued down and I'm afraid that I will strip the heads out if I torque them enough to break the glue. The position of the vanadate mounting plate was marked before I disassembled the laser, so I'm pretty sure it's where it was placed at the factory. All of the optical surfaces on the crystals, OC mirror, and expander lens/IR filter appear to be pristine, with no chips, cracks, gouges or missing chunks of AR coatings on any of the lasing components. I know the pump diode is still good--I get significant IR output through the vanadate that shows up on my cellphone camera. The only casualty of the disassembly process was the collimator lens, but it already had some chips in the AR coating and I intended on replacing it anyway.
Some questions:
1. The IR coming out of the vanadate (at least what's visible to my cell phone, presumably 808nm) is not a single spot or oval, it's a series of lines in a pattern sort of like a squarish bar code. Does this mean the alignment between the vanadate and pump diode needs adjustment, and if so, is that the cause of the multi-spot output? How would I fix this?
2. How can I tell the correct orientation of the KTP relative to the vanadate & pump diode. Everything I've read indicates that the KTP must be aligned with the polarization of the output from the vanadate, but I don't see any indication on the crystal or the mount that would identify the correct orientation.
3. I'd like to optimize the laser for minimum overall divergence rather than minimum short-range beam diameter. I would rather be able to see the spot from a greater distance than to ignite matches or pop balloons. Can I simply get a replacement collimator lens with a slightly different focal length and expand the beam a bit that way? I have a fair amount of slack in the focus adjustment available. Any recommendations for sourcing the lens?
I have everything apart except the 2 screws that mount the brass plate holding the vanadate crystal to the pump diode heatsink--they are glued down and I'm afraid that I will strip the heads out if I torque them enough to break the glue. The position of the vanadate mounting plate was marked before I disassembled the laser, so I'm pretty sure it's where it was placed at the factory. All of the optical surfaces on the crystals, OC mirror, and expander lens/IR filter appear to be pristine, with no chips, cracks, gouges or missing chunks of AR coatings on any of the lasing components. I know the pump diode is still good--I get significant IR output through the vanadate that shows up on my cellphone camera. The only casualty of the disassembly process was the collimator lens, but it already had some chips in the AR coating and I intended on replacing it anyway.
Some questions:
1. The IR coming out of the vanadate (at least what's visible to my cell phone, presumably 808nm) is not a single spot or oval, it's a series of lines in a pattern sort of like a squarish bar code. Does this mean the alignment between the vanadate and pump diode needs adjustment, and if so, is that the cause of the multi-spot output? How would I fix this?
2. How can I tell the correct orientation of the KTP relative to the vanadate & pump diode. Everything I've read indicates that the KTP must be aligned with the polarization of the output from the vanadate, but I don't see any indication on the crystal or the mount that would identify the correct orientation.
3. I'd like to optimize the laser for minimum overall divergence rather than minimum short-range beam diameter. I would rather be able to see the spot from a greater distance than to ignite matches or pop balloons. Can I simply get a replacement collimator lens with a slightly different focal length and expand the beam a bit that way? I have a fair amount of slack in the focus adjustment available. Any recommendations for sourcing the lens?
