Tough, EJ;
Fice, MJ;
Carpintero, G;
Renaud, CC;
Seeds, AJ;
Balakier, K;
(2022)
InP integrated optical frequency comb generator using an amplified recirculating loop.
Optics Express
, 30
(24)
pp. 43195-43208.
10.1364/OE.469942.
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Abstract
A novel realisation of photonically integrated optical frequency comb generation is demonstrated on indium phosphide (InP) using a generic foundry platform. The architecture, based on the amplified recirculating loop technique, consists of cascaded electro-optic phase modulators embedded within a short waveguide loop. While an injected continuous wave laser signal is recirculated by the loop, the modulators are driven with a modulation frequency corresponding to the round-trip loop length frequency. This results in many phase coherent, evenly spaced optical comb lines being generated. The choice of InP as an integration platform allows immediate optical amplification of the modulated signal by embedded semiconductor optical amplifiers, enabling loop losses to be compensated and expanding the comb across broad optical bandwidths. This approach reduces the requirement for external, high-power optical amplifiers, improving the compactness and power efficiency of the full system. The system was modelled to identify off-resonance behaviour, outlining limits in matching both the modulation frequency and seed laser frequency to the round-trip loop frequency for optimal comb line generation to be achieved. The experimental device occupied a fraction of the 6 x 2 mm2 InP chip and operated at round-trip loop frequencies of 6.71 GHz to produce 59 comb lines within a 20 dB power envelope. All comb lines exhibited strong phase coherence as characterised by low composite phase noise measurements of -105 dBc/Hz at 100 kHz. A second device is also presented with a shorter loop length operating at ∼10 GHz which generated 57 comb lines. Both loop configurations included short waveguide phase shifters providing a degree of tunability of the free spectral range with a tuning range of 150 MHz for small injection currents of < 2.5 mA.
| Type: | Article |
|---|---|
| Title: | InP integrated optical frequency comb generator using an amplified recirculating loop |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1364/OE.469942 |
| Publisher version: | https://doi.org/10.1364/OE.469942 |
| Language: | English |
| Additional information: | Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10160743 |
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