Wavelength Conversion Calculator

APE (standing for Angewandte Physik & Elektronik GmbH, a german company in Berlin) has a nice small (and free) wavelength converter on their homepage. It allows you to directly calculate the sum frequency and difference frequency generation, the wavelengths relations in an optical parameteric oscillator (OPO) as well as in coherent anti-stokes Raman scattering (CARS) spectroscopy. Furtermore, the conversion between wavelength, wavenumber, and frequency as well as different characterizations of pulses (dispersion) can be calculated.

The calculator page is in english and very userfriendly. Enjoy.