OPTICAL HARMONIC MIXERS

Mixing of optical signals in a waveguide via the second-order nonlinea r effect in semiconductors was studied theoretically and experimentall y. The InP-based material system was the main focus of the investigati ons. Both the up-conversion leading to second-harmonic generation and the down conversion leading to optical rectification were analyzed and experimentally verified. Experiments in nonlinear optical waveguide s tructures at 1.55 mu m wavelength have shown the existence of both the quadratic second-harmonic signals as well as the linearly dependent o ptical rectification signals. Quantitative estimates confirmed a good agreement between the theory and the experiment. Some interesting appl ications for high-speed optical data processing required in transparen t optical telecommunication systems have been identified. Most attract ive functions proposed to be implemented with these types of devices a re, for example, flexible-to-bit-rate all-optical clock extraction in a transparent high-performance optical telecommunication network or ac curate and fast measurement of optical frequency for optical synchroni zation needs in wavelength-division multiplexing systems.