Low-Phase-Noise Tenfold Frequency Multiplication based on Integrated Optical Frequency Combs

We experimentally demonstrate a low-phase-noise tenfold frequency multiplier based on a compact integrated optical frequency comb (OFC) generator. The Indium Phosphide (InP) monolithically integrated OFC is based on a flexible scheme using cascaded optical modulators. The extremely compact frequency multiplier is broadly tunable in wavelength and in OFC repetition frequency, making it interesting for high-spectral-purity mm-waves applications. OFC generation with a 2.6 GHz spacing and 19 tones within a 10 dB power range and an optical signal-to-noise ratio (OSNR) higher than 40 dB is reported. Using a 74 GHz-bandwidth photodetector, we achieve a set of 2.6 GHz phase-stabilized electrical tones, reaching carriers up to 39 GHz with a high signal-to-noise ratio (SNR). In particular, the OFC-based tenfold-multiplied signal (26 GHz) provides a remarkable low-phase-noise feature, equivalent to the commercially available radiofrequency (RF) generator used as a source at the same electrical power. At 26 GHz, phase-noise of -50 dBc/Hz and -80 dBc/Hz are reported for 10 Hz and 1 kHz offsets, respectively. The proposed system enables frequency multiplication up to 12-times without phase impairments, i.e., phase noise performance equivalent to a commercial RF generator, validating its potential to low-phase-noise and high-spectral-purity mm-wave applications.