Proton bombardment for enhanced four-wave mixing in InGaAsP-InP waveguides

A model for the transmission and four-wave mixing (FWM) conversion efficiency of InGaAsP-InP passive quantum-well (QW) waveguides which includes the effect of an additional nonlinear loss due to the accumulation of photogenerated free carriers is introduced and compared to experimental measurements. The model accurately describes the observed loss at high average powers and predicts that a reduction in the carrier lifetime of 10-100 times should effectively eliminate free carrier effects. Proton bombardment was investigated as a means of reducing the carrier lifetime, and both the conversion efficiency and relative transmission of proton bombarded single QW and multiple QW devices were significantly improved compared to unbombarded devices.