Optical-frequency synthesizers, which generate frequency-stable light from a single microwave-frequency reference, are revolutionizing ultrafast science and metrology, but their size, power requirement and cost need to be reduced if they are to be more widely used. Integrated-photonics microchips can be used in high-coherence applications, such as data transmission , highly optimized physical sensors and harnessing quantum states , to lower cost and increase efficiency and portability. Here we describe a method for synthesizing the absolute frequency of a lightwave signal, using integrated photonics to create a phase-coherent microwave-to-optical link. We use a heterogeneously integrated III-V/silicon tunable laser, which is guided by nonlinear frequency combs fabricated on separate silicon chips and pumped by off-chip lasers. The laser frequency output of our optical-frequency synthesizer can be programmed by a microwave clock across 4 terahertz near 1,550 nanometres (the telecommunications C-band) with 1 hertz resolution. Our measurements verify that the output of the synthesizer is exceptionally stable across this region (synthesis error of 7.7 × 10 or below). Any application of an optical-frequency source could benefit from the high-precision optical synthesis presented here. Leveraging high-volume semiconductor processing built around advanced materials could allow such low-cost, low-power and compact integrated-photonics devices to be widely used.
Optical microcavities are essential in numerous technologies and scientific disciplines. However, their application in many areas relies exclusively upon discrete microcavities in order to satisfy challenging combinations of ultra-low-loss performance (high cavity-Q-factor) and cavity design requirements. Indeed, finding a microfabrication bridge connecting ultra-high-Q device functions with micro and nanophotonic circuits has been a long-term priority of the microcavity field. Here, an integrated ridge resonator having a record Q factor over 200 million is presented. Its ultralow-loss and flexible cavity design brings performance that has been the exclusive domain of discrete silica and crytalline microcavity devices to integrated systems. Two distinctly different devices are demonstrated: soliton sources with electronic repetition rates and high-coherence Brillouin lasers. This multi-device capability and performance from a single integrated cavity platform represents a critical advance for future nanophotonic circuits and systems.Optical microcavities 1 provide diverse device functions that include frequency microcombs 2,3 , soliton modelocked microcombs 4-8 , Brillouin lasers 9-13 , bio and nanoparticle sensors 14-16 , cavity optomechanical oscillators 17 , parametric oscillators 18,19 , Raman lasers 20 , reference cavities/sources 21-24 , and quantum optical devices 25,26 . Key performance metrics improve with increasing Qfactor across all applications areas 1 . For example, higher Q factors dramatically reduce power consumption as well as phase and intensity noise in signal sources, because these quantities scale inverse quadratically with Q factor. Also, higher Q improves the ability to resolve a resonance for sensing or for frequency stabilization. Such favorable scalings of performance with Q factor have accounted for a sustained period of progress in boosting Q factor by reducing optical loss in resonators across a range of materials 27-31 . Likewise, the need for complex microcavity systems that leverage high-Q factors has driven interest in low-loss monolithically integrated resonators 28,29,[32][33][34][35][36][37][38] . For example, Q values in waveguide-integrated devices to values as high as 80 million 35 and 67 million 38 in strongly-confined resonators have been attained.Nonetheless, the highest Q-factor resonators remain discrete devices that are crystalline 39 or silica based 1,11,40,41 . These discrete resonators are moreover unique in the microcavity world in terms of overall per-formance and breadth of capability. This includes generation of electronic-repetition-rate soliton streams as required in optical clocks 42-44 and optical synthesizers 45 , rotation measurement at near-earth-rate sensitivity in micro-optical-gyros 46,47 , synthesis of high-performance microwave signals 48-51 , and operation as high-stability optical frequency references 21-23 and reference sources 24 . Functions such as these belong to a new class of compact photonic systems that rely upon ultra-high-Q fabrication m...
Frequency combs have applications that extend from the ultra-violet into the mid-infrared bands. Microcombs, a miniature and often semiconductor-chip-based device, can potentially access most of these applications, but are currently more limited in spectral reach. Here, we demonstrate mode-locked silica microcombs with emission near the edge of the visible spectrum. By using both geometrical and mode-hybridization dispersion control, devices are engineered for soliton generation while also maintaining optical Q factors as high as 80 million. Electronics-bandwidth-compatible (20 GHz) soliton mode locking is achieved with low pumping powers (parametric oscillation threshold powers as low as 5.4 mW). These are the shortest wavelength soliton microcombs demonstrated to date and could be used in miniature optical clocks. The results should also extend to visible and potentially ultra-violet bands.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.