Matching phase and group velocities in second-harmonic generation in finite one-dimensional photonic band-gap structures

One-dimensional photonic band-gap structures are shown to allow phase and g roup-velocity matching to be simultaneously achieved for second-harmonic ge neration involving ultrashort light pulses. When these conditions are satis fied, photonic band-gap frequency doublers permit the growth rate of the se cond harmonic intensity as a function of the nonlinear-optical interaction length to be increased as compared with quasi-phase-matched second-harmonic generation, opening new ways of improving the efficiency of frequency doub ling regardless of the coherence length in the bulk of a nonlinear material .