Time-gated filter for sideband suppression.

A time-gated filter is demonstrated that converts a double-sideband radio-frequency (rf) waveform on a pulsed optically chirped carrier into a single sideband (SSB) waveform. Electrical technology to produce SSB modulation is currently limited to rfs less than 20 GHz, while our filter operates up to the maximum frequency available from optical modulators. Application of the filter in photonic time-stretch analog-to-digital converters (TS-ADCs) mitigates severe frequency fading owing to the dispersion penalty that limits the rf input signal bandwidth and time aperture. Here we show that frequency fading owing to the presence of both upper and lower sidebands in the TS-ADC can be reduced by over 20 dB and that a TS-ADC using this filter can digitize electrical signals with rfs beyond 100 GHz.