Optical Society of America
Founded in 1916, the Optical Society of America (OSA) was organized to increase and diffuse the knowledge of optics, pure and applied; to promote the common interests of investigators of optical problems, of designers, and of users of optical apparatus of all kinds; and to encourage cooperation among them. The purposes of the Society are scientific, technical, and educational.

SNLO
SNLO is a software package for calculating nonlinear optical parameters. It was written in Sandia National Laboratories, and can be downloaded at no charge through the internet.

The Materials Referral System & Hotline
This is a service provided by AMES National Laboratory. The referral service maintains a database of sources for materials, and will provide a list of sources for materials at no charge to the user.

The International Society for Optical Engineering
The website for optics, photonics and imaging.

RP Photonics Consulting GmbH
RP Photonics provides detailed technical advice on the use of nonlinear crystals. For example, it works out designs for nonlinear frequency conversion stages such as frequency doublers, sum and difference frequency generators, or optical parametric oscillators and amplifiers. Detailed calculations and simulations can be done as required.