Study of the Retracing Behavior of the Phase-Matching Angle inSecond Harmonic Generation

The retracing behavior of the phase-matching angle (RBPA) in many nonlinear optical crystals for second harmonic generation (SHG) has been demonstrated by calculation. The generality of this phenomenon is successfully explained by a theoretical analysis based on classical optics. The wavelengths of the fundamental waves and phasematching angles for describing the RBPA of eight kinds of crystals are presented. Furthermore, we point out that RBPA exists generally in both uniaxial and biaxial crystals for both type I and type II SHG.