Development of convenient, efficient, nonlinear optical materials to serve as "optical mixers" for optical synthesis. Emphasis here is on domain engineered materials such as periodically-poled lithium niobate (PPLN). In a collaborative effort with Norm Sanford’s group in EEEL, We have been using specially designed PPLN crystals for wavelength conversion. These devices can be used for second harmonic generation (SHG), difference frequency generation (DFG), Sum Frequency Generation (SFG), and third harmonic generation as the result of cascaded second-order mixing.

For further information, see O. Pfister, et al., Opt. Lett. 22, 1211-1213 (1997).

Diagram of periodically poled lithium niobate crystal. The poling period is exaggerated here for clarity, but typically ranges from 8 to 35 microns for the devices fabricated here at NIST for our applications. The nonlinearly generated output signals that we have observed from PPLN samples using low power CW laser sources are indicated here.

Besides the critical role they play in our optical synthesis effort there are a number of other applications of the wavelength converted radiation from these nonlinear crystals. One promising application is in high sensitivity spectroscopic measurements of atoms and molecules (see pages on ultra-sensitive spectroscopy and gas-phase spectroscopy).