To provide a light source that effectively and efficiently generates light energy at wavelengths of 213 nm or less, using materials that have been processed specifically to provide increased lifetimes, stability, and damage thresholds over designs previously available.

A method for generating light energy comprises: a step of generating fundamental frequency laser energy at a wavelength of about 998 nm; a step of converting a portion of the fundamental frequency laser energy to second harmonic frequency laser energy; a step of converting the second harmonic frequency laser energy to fourth harmonic frequency laser energy; and a step of mixing the fourth harmonic frequency laser energy with a portion of the fundamental frequency laser energy to produce laser energy at a sum frequency. Mixing is accomplished by non-critical phase matching in a crystal of Cesium Lithium Borate (CLBO).