Type II microcomb generation in a filter-driven four wave mixing laser

Andrew Cooper1, Hualong Bao1, Sai T Chu2, Dave J Moss3, Roberto Morandotti4, Brent Little5, Marco Peccianti1 and Alessia Pasquazi1 1 University of Sussex, UK, 2 City University of Hong Kong, Hong Kong, China, 3 RMIT... [ view full abstract ]

Andrew Cooper1, Hualong Bao1, Sai T Chu2, Dave J Moss3, Roberto Morandotti4, Brent Little5, Marco Peccianti1 and Alessia Pasquazi1

1 University of Sussex, UK, 2 City University of Hong Kong, Hong Kong, China, 3 RMIT University, Melboune, Australia, 4 INRS - Énergie, Matériaux et Télécommunications, France,
5 Xi’an Institute of Optics and Precision Mechanics of CAS, China


We report experimental results of generation of a type-II microcomb in a filter-driven four wave mixing laser based on a CMOS compatible microring resonator. These results represent steps toward a miniature and robust source of optical frequency combs. These combs consist of precisely spaced spectral lines, with potential to create ultra-fast and stable optical clocks that can be easily fabricated [1] and used for integrated optics applications.

In this work we present the behaviour of our laser in a variety of regimes producing stable frequency combs using a doped silica glass microring with a FSR of 50GHz. The system consists of an outer fibre loop cavity with a fibre amplifier as the gain medium. Combs form through passive mode-locking of the laser through filter-driven four wave mixing [2] and the four wave mixing process inside the high-Q, highly nonlinear microring. The system can be controlled by varying the polarization, main cavity path length and intra-cavity power.

We observe overtone oscillation and for higher powers the lines fill the comb at the free spectral range of the system. This behaviour is recalls the behaviour of type-II microcombs [3] excited with a coherent laser lines, but in stark contrast with these results we observe coherent oscillation.



[1] K. J. Vahala, “Optical microcavities”, Nature 424 (2003) pp. 839 - 846
[2] A. Pasquazi et al. “Self-locked optical parametric oscillation in a CMOS compatible microring resonator: a route to robust optical frequency comb generation on a chip”, Optics Express 21 (2013) pp. 13333-13341
[3] F. Ferdous et al. “Spectral line-by-line pulse shaping of on-chip microresonator frequency combs”, Nature Photonics 5 (2011) pp. 770-776