Abstract
In nonlinear microresonators driven by continuous-wave (cw) lasers, Turing patterns have been studied in the formalism of the Lugiato-Lefever equation with emphasis on their high coherence and exceptional robustness against perturbations. Destabilization of Turing patterns and the transition to spatiotemporal chaos, however, limit the available energy carried in the Turing rolls and prevent further harvest of their high coherence and robustness to noise. Here, we report a novel scheme to circumvent such destabilization, by incorporating the effect of local mode hybridizations, and we attain globally stable Turing pattern formation in chip-scale nonlinear oscillators with significantly enlarged parameter space, achieving a record-high power-conversion efficiency of 45% and an elevated peak-to-valley contrast of 100. The stationary Turing pattern is discretely tunable across 430 GHz on a THz carrier, with a fractional frequency sideband nonuniformity measured at . We demonstrate the simultaneous microwave and optical coherence of the Turing rolls at different evolution stages through ultrafast optical correlation techniques. The free-running Turing-roll coherence, 9 kHz in 200 ms and 160 kHz in 20 minutes, is transferred onto a plasmonic photomixer for one of the highest-power THz coherent generations at room temperature, with 1.1% optical-to-THz power conversion. Its long-term stability can be further improved by more than 2 orders of magnitude, reaching an Allan deviation of at 100 s, with a simple computer-aided slow feedback control. The demonstrated on-chip coherent high-power Turing-THz system is promising to find applications in astrophysics, medical imaging, and wireless communications.
- Received 9 August 2016
DOI:https://doi.org/10.1103/PhysRevX.7.041002
Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
As data networks expand to support ever-increasing demand, communication devices that can handle vast amounts of information are essential. While the bulk of this information is shuttled via fiber-optic networks that support terabits per second, the final connection to the end user is often via a wireless link. To keep up with fiber-optic data rates, this link must operate at frequencies of around 1 THz. But long-distance, high-capacity, THz wireless communication is limited by insufficient transmitter power and instabilities in the electromagnetic carrier signal. As a step toward solving these issues, we have developed a stable THz transmitter that operates on a microchip at room temperature.
We combined a microscale cavity, which generates a coherent set of THz frequency lines known as a frequency comb, with a photomixer, a device that generates THz radiation by combining two frequency lines. This generates stable, coherent, near-milliwatt-level THz radiation on a single chip at room temperature. Modal interactions in the microcavity stabilize the pattern of frequency lines across a broad spectrum and parameter space. The stationary pattern is discretely tunable across 430 GHz. We observed record-high power-conversion efficiency between the pump and primary frequency lines at 45%, with an elevated peak-to-valley contrast of 100.