QUASI-PHASE-MATCHED 2ND HARMONIC-GENERATION - TUNING AND TOLERANCES

Quasi-phase matching is a technique for phase matching nonlinear optical interactions in which the relative phase is corrected at regular intervals using a structural periodicity built into the nonlinear medium. The theory of quasi-phase-matched second harmonic generation is presented in both the space domain and the wave vector mismatch domain. Departures from ideal quasi-phase matching in periodicity, wave-length, angle of propagation, and temperature are examined to determine the tuning properties and acceptance bandwidths for second harmonic generation in periodic structures. Numerical examples are tabulated for periodically poled lithium niobate. Various types of errors in the periodicity of these structures are then analyzed to find their effects on the conversion efficiency and on the shape of the tuning curve. This analysis is useful for establishing fabrication tolerances for practical quasi-phase-matched devices. A method of designing structures having desired phase-matching tuning curve shapes is also described which makes use of varying domain lengths to establish a varying effective nonlinear coefficient along the interaction length.