Zhang, X. P., Hebling, J., Kuhl, J., Rühle, W. W., & Giessen, H. (2002). Efficient Visible Light Generation in a Femptosecond PPLN Optical Parametric Oscillator Using an Uneven Poling Duty Cycle. In Technical Digest CLEO 2002 (pp. 418-419). Long Beach, CA, USA: Optical Society of America.