While soliton microcombs offer the potential for integration of powerful frequency metrology and precision spectroscopy systems, their operation requires complex startup and feedback protocols that necessitate difficult-to-integrate optical and electrical components. Moreover, CMOS-rate microcombs, required in nearly all comb systems, have resisted integration because of their power requirements. Here, a regime for turnkey operation of soliton microcombs co-integrated with a pump laser is demonstrated and theoretically explained. Significantly, a new operating point is shown to appear from which solitons are generated through binary turn-on and turn-off of the pump laser, thereby eliminating all photonic/electronic control circuitry. These features are combined with high-Q Si3N4 resonators to fully integrate into a butterfly package microcombs with CMOS frequencies as low as 15 GHz, offering compelling advantages for high-volume production.

We control the electronic structure of the silicon-vacancy (SiV) color-center in diamond by changing its static strain environment with a nano-electro-mechanical system. This allows deterministic and local tuning of SiV optical and spin transition frequencies over a wide range, an essential step towards multi-qubit networks. In the process, we infer the strain Hamiltonian of the SiV revealing large strain susceptibilities of order 1 PHz/strain for the electronic orbital states. We identify regimes where the spin-orbit interaction results in a large strain suseptibility of order 100 THz/strain for spin transitions, and propose an experiment where the SiV spin is strongly coupled to a nanomechanical resonator.arXiv:1801.09833v2 [quant-ph]

Driven by narrow-linewidth bench-top lasers, coherent optical systems spanning optical communications, metrology and sensing provide unrivalled performance. To transfer these capabilities from the laboratory to the real world, a key missing ingredient is a mass-produced integrated laser with superior coherence. Here, we bridge conventional semiconductor lasers and coherent optical systems using CMOS-foundry-fabricated microresonators with record high Q factor over 260 million and finesse over 42,000. Five orders-of-magnitude noise reduction in the pump laser is demonstrated, and for the first time, fundamental noise below 1 Hz 2 Hz −1 is achieved in an electrically-pumped integrated laser. Moreover, the same configuration is shown to relieve dispersion requirements for microcomb generation that have handicapped certain nonlinear platforms. The simultaneous realization of record-high Q factor, highly coherent lasers and frequency combs using foundry-based technologies paves the way for volume manufacturing of a wide range of coherent optical systems.

Silicon nitride (SiN) waveguides with ultra-low optical loss enable integrated photonic applications including low noise, narrow linewidth lasers, chip-scale nonlinear photonics, and microwave photonics. Lasers are key components to SiN photonic integrated circuits (PICs), but are difficult to fully integrate with low-index SiN waveguides due to their large mismatch with the high-index III-V gain materials. The recent demonstration of multilayer heterogeneous integration provides a practical solution and enabled the first-generation of lasers fully integrated with SiN waveguides. However, a laser with high device yield and high output power at telecommunication wavelengths, where photonics applications are clustered, is still missing, hindered by large mode transition loss, non-optimized cavity design, and a complicated fabrication process. Here, we report high-performance lasers on SiN with tens of milliwatts output power through the SiN waveguide and sub-kHz fundamental linewidth, addressing all the aforementioned issues. We also show Hertz-level fundamental linewidth lasers are achievable with the developed integration techniques. These lasers, together with high-Q SiN resonators, mark a milestone towards a fully integrated low-noise silicon nitride photonics platform. This laser should find potential applications in LIDAR, microwave photonics and coherent optical communications.

Acquisition of laser frequency with high resolution under continuous and abrupt tuning conditions is important for sensing, spectroscopy and communications. Here, a single microresonator provides rapid and broad-band measurement of frequencies across the optical C-band with a relative frequency precision comparable to conventional dual frequency comb systems. Dual-locked counter-propagating solitons having slightly different repetition rates are used to implement a Vernier spectrometer. Laser tuning rates as high as 10 THz/s, broadly step-tuned lasers, multiline laser spectra and also molecular absorption lines are characterized using the device. Besides providing a considerable technical simplification through the dual-locked solitons and enhanced capability for measurement of arbitrarily tuned sources, this work reveals possibilities for chipscale spectrometers that greatly exceed the performance of table-top grating and interferometerbased devices.Frequency-agile lasers are ubiquitous in sensing, spectroscopy and optical communications 1-3 and measurement of their optical frequency for tuning and control is traditionally performed by grating and interferometerbased spectrometers, but more recently these measurements can make use of optical frequency combs 4-6 . Frequency combs provide a remarkably stable measurement grid against which optical signal frequencies can be determined subject to the ambiguity introduced by their equally spaced comb lines. The ambiguity can be resolved for continuously frequency swept signals by counting comb teeth 7 relative to a known comb tooth; and this method has enabled measurement of remarkably high chirp rates 8 . However, signal sources can operate with abrupt frequency jumps so as to quickly access a new spectral region or for switching purposes, and this requires a different approach. In this case, a second frequency comb with a different comb line spacing can provide a Vernier scale 9 for comparison with the first comb to resolve the ambiguity under quite general tuning conditions 9-11 . This Vernier concept is also used in dual comb spectroscopy 12,13 , but in measuring active signals the method can be significantly enhanced to quickly identify signal frequencies through a signal correlation technique 9 . The power of the Vernier-based method relies upon mapping of optical comb frequencies into a radio-frequency grid of frequencies, the precision of which is set by the relative line-by-line frequency stability of the two frequency combs. This stability can be guaranteed by self-referencing each comb using a common high-stability radio-frequency source or through optical locking of each comb to reference lasers whose relative stability is ensured by mutual locking to a common optical cavity.Here, a broad-band, high-resolution Vernier soliton microcomb spectrometer is demonstrated using a single miniature comb device that generates two mutuallyphase-locked combs. The principle of operation relies upon an optical phase locking effect observed in the generation of counter-pr...