OPTICS/OPTICAL MATERIALS

OPTICS/OPTICAL MATERIALS

The nonlinear material periodically poled lithium niobate (PPLN) from Deltronic Crystal Industries (Dover, NJ) and Gemfire (formerly Deacon Research; Palo Alto, CA) has received widespread attention since it became available in November 1996. Although lithium niobate itself has been long used for various applications, including second-harmonic generation (SHG) and optical parametric oscillation (OPO) via birefringent phase-matching, the periodic poling process gives it properties suited for much wider applications based on quasi-phase-matching (QPM). With QPM, crystals can be made appropriate for phase-matching of any optical interaction within the transparency range of lithium niobate (0.35 to 5.0 µm). Deltronic Crystal Industries supplies wafers to Gemfire/Deacon Research, which uses its electric-field poling process to effect a permanent change in its nonlinear properties. Because of its significance for visible and mid-infrared wavelengths, PPLN offers a number of application posibilities--wind-speed and wind-shear detection and trace-gas monitoring are a few OPO applications, while SHG applications include spectroscopy, semiconductor processing, medical diagnostics, and optical disk memory.