Frequency Doubling Broadband Light in Multiple Crystals

We compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk-off compensation and with doubling in five crystals adjusted for offset phase-matching frequencies. Using a plane-wave dispersive numerical model of frequency doubling, we study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance, the offset phase-matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second-harmonic bandwidth. The walk-off-compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single-crystal efficiency while maintaining a broad bandwidth.