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The green laser pointer contains much more than a simple diode as a red laser pointer does. Red pointers are a simple diode while green pointers contain a host of components. Because green diodes are not available (yet) the only way to make a green pointer, short of a small gas HeNe tube, is to use a frequency-doubled DPSS. First off, the laser rod is made from Nd:YVO4, not YAG. This material, called 'vanadate', is a more efficient material for DPSS lasers (it has a low threshold and so is suited to use with low-power pump lasers). It has a primary absorption peak at 808nm just barely in the infrared. The pump diode is hence selected to emit at this wavelength for optimal efficiency. The pump light at 808nm is fired at the crystal directly through the rear mirror of the laser. The rear mirror, although totally reflecting at the vanadate's emission wavelength of 1064nm (same as YAG - the Nd atom actually sets the lasing wavelength, YAG or vanadate are simply the host glasses used) are quite transparent to 808nm. This is possible because these are dielectric mirrors made of multiple alternating layers of thin-films and are reflective only at a single designed wavelength while transmitting other wavelengths. HeNe mirrors are also dielectric and you'll note that you can see blue light through an (unpowered) HeNe tube.
So, pump light at 808nm excites the vanadate crystal which then emits light at 1064nm in the infrared. To obtain green light intra-cavity second-harmonic generation is accomplished. To do this a crystal of potassium titanyl phosphate, or KTP, is put directly in the laser cavity between the front of the vanadate crystal and the front mirror (output coupler).
Via a non-linear optical process the 1064nm light is doubled to 532nm (green). The KTP crystal is inside the cavity itself where power levels are much higher than outside the cavity: this is required for efficient conversion of light. The front mirror or output coupler is another dielectric mirror allowing green light to pass through while reflecting infrared light at 1064nm (and excess 808nm pump light that makes it through the crystal) back into the vanadate to keep it lasing. This is evident from the photo in which the OC appears green. Note that the mirror was fabricated directly onto the surface of the KTP crystal (by thin-film deposition techniques) and was made into the shape of a circle to define the beam (otherwise the beam might have been square since the vanadate and KTP crystals are both blocks).
Info From technology.niagarac.on.ca/
So, pump light at 808nm excites the vanadate crystal which then emits light at 1064nm in the infrared. To obtain green light intra-cavity second-harmonic generation is accomplished. To do this a crystal of potassium titanyl phosphate, or KTP, is put directly in the laser cavity between the front of the vanadate crystal and the front mirror (output coupler).
Via a non-linear optical process the 1064nm light is doubled to 532nm (green). The KTP crystal is inside the cavity itself where power levels are much higher than outside the cavity: this is required for efficient conversion of light. The front mirror or output coupler is another dielectric mirror allowing green light to pass through while reflecting infrared light at 1064nm (and excess 808nm pump light that makes it through the crystal) back into the vanadate to keep it lasing. This is evident from the photo in which the OC appears green. Note that the mirror was fabricated directly onto the surface of the KTP crystal (by thin-film deposition techniques) and was made into the shape of a circle to define the beam (otherwise the beam might have been square since the vanadate and KTP crystals are both blocks).
Info From technology.niagarac.on.ca/
