Enhancement of bright squeezing in the second harmonic by internally seeding the /spl chi//sup (2)/ interaction

Second-harmonic generation (SHG) and parametric amplification result from the same physical configuration of the /spl chi//sup (2)/ process, but with different input conditions for the interacting fundamental and harmonic waves. In the former, the input harmonic field is usually in the vacuum state whereas, in the latter, the fundamental is in the vacuum state (or a small-amplitude coherent state). A different set of input conditions can lead to a nonlinear phase shift in both the fundamental and the harmonic waves, while not affecting their relative magnitudes. In conjunction with SHG, we show that this configuration can be used to generate a bright (high-intensity) amplitude-squeezed (sub-Poissonian) field at the harmonic frequency. Large amounts of squeezing are possible. An integrated device with the above characteristics can be fabricated by utilizing the recently developed quasi-phase-matching techniques.