mcdonald@uxe.cso.uiuc.edu (09/23/88)
>I have heard of frequency doubling crystals; this is how solid-state lasers >are made to emit green light. I have no idea how the effect works, though. >A VISIBLE solid state laser? Please tell us more! >Who makes it? (or do you have to make it yourself?), >what is it used for?, cost?, efficiency? >Enquiring minds want to know. Not counting diode lasers, which of course can be made red if you so wish, there are rubies and alexandrites. Both are deep red. They are used for high power visible laser experiments. The alexandrite one is tunable. It used to be made by Allied (Chemical) but they sold it to some laser company. I can look up the sources in the Laser Focus buyer's guide if you wish. A typical cost is $50,000. Efficiency is low (except for ruby cooled to 77K). Doubler crystals are neat. They work as follows: normally the response of a material to an electric field is linear: D = aE where D is the response and E in incoming field. but lasers produce fields high enough that they enter their nonlinear response regions and the response becomes 2 3 D = aE + bE + cE + ... The squared term occurs only in certain non-centrosymmetric crystals. The nonlinear terms generate harmonic distortion, exactly like distortion in audio systems. The second harmonic of a neodymium laser at 1.064 microns is .532 microns, which is green. Doug McDonald