Versatile Amplitude and Phase Filtering in an Optical Tapped Delay Line Structure

High repetition-rate optical pulse trains are widely used in high-speed optical communication, optical sampling, and microwave photonics. Pulse repetition-rate multiplication (RRM) outside laser cavity is of particular interest when the target rate is not readily available. RRM is generally achieved by spectral amplitude filtering, manifested by increased comb spacing of the spectrum, using pulse shaper or optical tapped delay line structure [1]. Another approach is spectral phase filtering, also known as temporal Talbot effect without altering the input spectrum. Typical methods include using linearly chirped fibre Bragg grating, or pulse shaper. Ring-resonator based filters [2] have been proposed to provide temporal Talbot condition, but need stringent control of both coupling coefficient and round-trip phase. Here, we show that temporal Talbot effect, as well as versatile combinations of amplitude and phase filtering can also be implemented in a simple tapped delay line structure, hence very promising for on-chip temporal Talbot multiplier.