Multilevel quantization of optical phase in a novel coherent parametric mixer architecture

The exponentially increasing capacity demand in information systems will be met by carefully exploiting the complementary strengths of electronics and optics(1,2). Optical signal processing provides simple but powerful pipeline functions that offer high speed, low power, low latency and a route to densely parallel execution(3). A number of functions such as modulation and sampling(4-7), complex filtering(8) and Fourier transformation(9) have already been demonstrated. However, the key functionality of all-optical quantization has still not been addressed effectively. Here, we report an all-optical signal processing architecture that enables, for the first time, multilevel all-optical quantization of phase-encoded optical signals. A four-wave-mixing process is used to generate a comb of phase harmonics of the input signal, and a two-pump parametric process to coherently combine a selected harmonic with the input signal, realizing phase quantization. We experimentally demonstrate operation up to six levels.