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In the past decade, remarkable advances in integrated photonic technologies have enabled table-top experiments and instrumentation to be scaled down to compact chips with significant reduction in size, weight, power consumption, and cost. Here, we demonstrate an integrated continuously tunable laser in a heterogeneous gallium arsenide-on-silicon nitride (GaAs-on-SiN) platform that emits in the far-red radiation spectrum near 780 nm, with 20 nm tuning range, <6 kHz intrinsic linewidth, and a >40 dB side-mode suppression ratio. The GaAs optical gain regions are heterogeneously integrated with low-loss SiN waveguides. The narrow linewidth lasing is achieved with an extended cavity consisting of a resonator-based Vernier mirror and a phase shifter. Utilizing synchronous tuning of the integrated heaters, we show mode-hop-free wavelength tuning over a range larger than 100 GHz (200 pm). To demonstrate the potential of the device, we investigate two illustrative applications: (i) the linear characterization of a silicon nitride microresonator designed for entangled-photon pair generation and (ii) the absorption spectroscopy and locking to the D1 and D2 transition lines of 87Rb. The performance of the proposed integrated laser holds promise for a broader spectrum of both classical and quantum applications in the visible range, encompassing communication, control, sensing, and computing. 

Since the start of science operations in 1993, the twin 10-meter W. M. Keck Observatory (WMKO) telescopes have continued to maximize their scientific impact and to produce transformative discoveries that keep the observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided though collaborative partnerships with Caltech, the University of California, and the University of Hawaii instrument development teams, as well as industry and other organizations. This paper summarizes the performance of recently commissioned infrastructure projects, technology upgrades, and new additions to the suite of observatory instrumentation. We also provide a status of projects currently in design or development phases and, since we keep our eye on the future, summarize projects in exploratory phases that originate from our 2022 strategic plan developed in collaboration with our science community to adapt and respond to evolving science needs. 

Abstract High‐coherence visible and near‐visible laser sources are centrally important to the operation of advanced position/navigation/timing systems as well as classical/quantum sensing systems. However, the complexity and size of these bench‐top lasers are an impediment to their transition beyond the laboratory. Here, a system‐on‐chip that emits high‐coherence near‐visible lightwaves is demonstrated. The devices rely upon a new approach wherein wavelength conversion and coherence increase by self‐injection locking are combined within a single nonlinear resonator. This simplified approach is demonstrated in a hybridly‐integrated device and provides a short‐term linewidth of around 4.7 kHz (10 kHz before filtering). On‐chip converted optical power over 2 mW is also obtained. Moreover, measurements show that heterogeneous integration can result in a conversion efficiency higher than 25% with an output power over 11 mW. Because the approach uses mature III–V pump lasers in combination with thin‐film lithium niobate, it can be scaled for low‐cost manufacturing of high‐coherence visible emitters. Also, the coherence generation process can be transferred to other frequency conversion processes, including optical parametric oscillation, sum/difference frequency generation, and third‐harmonic generation.