I just found a great article on how frequency doubling works in nonlinear optics. This is the process that is used to create your 532nm lasers (among other colors.) Below is a brief summary of the article. Check out the links for more information.

One of the most commonly-used frequency-mixing processes is frequency doubling or second-harmonic generation. With this technique, the 1064-nm output from Nd:YAG lasers or the 800-nm output from Ti:sapphire lasers can be converted to visible light, with wavelengths of 532 nm (green) or 400 nm (violet), respectively.

Practically, frequency-doubling is carried out by placing a special crystal in a laser beam under a well-chosen angle. Commonly-used crystals are BBO (β-barium borate), KDP (potassium dihydrogen phosphate), KTP (potassium titanyl phosphate), and lithium niobate. These crystals have the necessary properties of being strongly birefringentorganic polymeric materials are set to take over from crystals as they are cheaper to make, have lower drive voltages and superior performance. (necessary to obtain phase matching, see below), having a specific crystal symmetry and of course being transparent for and resistant against the high-intensity laser light. However,

http://en.wikipedia.org/wiki/Nonlinear_optics

Also, be sure to check out this article. It contains information on one of the specific compounds which make our green lasers possible:

Potassium titanyl phosphate (KTiOPO₄) or KTP is a nonlinear optical material which is commonly used for frequency doubling diode pumped solid-state lasers such as Nd:YAG and other neodymium-doped lasers. The material has a relatively high optical damage threshold (~15 J/cm²), a great optical nonlinearity and excellent thermal stability. However, it is prone to photochromic damage (called grey tracking) during high-power 1064nm second-harmonic generation which tends to limit its use to low- and mid-power systems.

It is also frequently used as an optical parametric oscillator for near IR generation up to 4 µm. It is particularly suited to high power operation as an optical parametric oscillator due to its high damage threshold and large crystal aperture. The high degree of birefringent walkoff between the pump signal and idler beams present in this material limit its use as an optical parametric oscillator for very low power applications.

KTP is also used as an electrooptic modulator, optical waveguide material, and in directional couplers.

KTP has orthorhombic crystal structure. It is highly transparent for wavelengths between 350–2700 nm with a reduced transmission out to 4500 nm where the crystal is effectively opaque. Its second harmonic generationKDP. It has a Mohs hardness of about 5. (SHG) coefficient is about threfold higher than

Crack-free fibers of KTP can be prepared from suitable organometallic compounds (usually ethyl alkoxides of potassium and titanium, and butyl ester of phosphoric acid).

KTP crystals coupled with Nd:YAG or Nd:YVO₄ crystals are commonly found in green laser pointers.

Other such materials include KTiOAsO₄

http://en.wikipedia.org/wiki/Potassium_titanyl_phosphate