Generation of Arbitrary Sequences of Ultrafast Pulses With Integrated-Optic Space-to-Time Optical Processors and Phase-Only Masks

We report a new approach to the generation of arbitrary sequences of ultrafast pulses using an integrated optics space-to-time optical processor. The processor combines a reflective arrayed waveguide grating multiplexer with a phase-only mask containing sets of pixels of constant phase separated by sets of pixels with phases alternating between 0 and $\pi$ rad.

The GENERATION of arbitrary sequences of femtosecond pulses at very high repetition rates, with its potential for applications in high-speed telecommunications systems, has been a subject of considerable interest in the last few years [1]–[3]. Integrated optics space-to-time optical processors are of particular importance in addressing this problem [3]–[6]. The integrated-optic approach offers advantages, compared to equivalent bulk-optic implementations, of reduced footprint, the absence of assembly and alignment, and the ease of integrating other passive or active components on the same platform. Prior demonstrations of arbitrary sequences of ultrafast pulses using integrated optics space-to-time optical processors relied on arrayed waveguide grating (AWG) multiplexers and amplitude masks, resulting in relatively high losses [5], [6]. In order to overcome this difficulty, we have recently demonstrated an integrated-optic processor based on reflective (R)-AWGs and binary phase masks [7]. However, that approach only allows for the generation of periodic sequences of ultrafast pulses. In order to generate arbitrary sequences of ultrafast pulses using space-to-time optical processor with phase modulation, a new approach is needed.