Search

The ability to tune the wavelength of light emission on a silicon chip is important for scalable photonic networks, distributed photonic sensor networks and next generation computer architectures. Here we demonstrate light emission in a chip-scale optomechanical device, with wide tunablity provided by a combination of radiation pressure and photothermal effects. To achieve this, we develop an optically active double-disk optomechanical system through implantation of erbium ions. We observe frequency tuning of photoluminescence in the telecommunications band with a wavelength range of 520 pm, green upconversion lasing with a threshold of $340\pm 70 \; \mu$W, and optomechanical self-pulsing caused by the interplay of radiation pressure and thermal effects. These results provide a path towards widely-tunable micron-scale lasers for photonic networks., Comment: Main text 7 pages, 5 figures; Appendix 4 pages, 4 figures

An optomechanical system is formed when the resonance frequency of an optical cavity is linked to the position of a mechanical resonator. The study of optomechanical systems has exploded over the last few decades, with many geometries and applications arising from this coupling of light and mechanical motion. Among these, applications in optical and mechanical control have opened new avenues of study in the development of technologies, for example photonic circuit signal routing and creating networks of sensors, as well as fundamental studies such as mechanical many-body dynamics.In this thesis, we introduce an additional feature to the canonical optomechanical system, namely an electrical means to actuate the mechanical element, in the form of metal electrodes integrated directly on to the device. These electrodes generate a capacitive force upon the application of a voltage bias, which is used to control the device properties. We present in this work two geometries of such opto-electromechanical devices in silica, namely microtoroids and double-disks. In the microtoroidal geometry we demonstrate the use of capacitive actuation as a control knob to tune the optical resonances of the device by over 20 linewidths and a rate of 80 kHz, and to lock its mechanical motion over a range of 71 kHz.In comparison to microtoroidal structures, double-disks present a much less studied platform. Double-disks possess strong optomechanical coupling due to a hybridisation of optical modes between the stacked disk. Therefore we are able to demonstrate optical tuning over more than three free spectral ranges in this geometry, which allows the device to be set on resonance with any desired frequency in the material transparency window. Furthermore, the tuning mechanism requires a low power consumption of ∼400 pW to achieve and maintain tuning, while preserving the quality of the cavity across the entire tuning range. This promises many exciting applications, including wide-band operation of multi-frequency photonic circuits and on-chip spectrometry. We further investigate the inclusion of an active medium to a double-disk cavity and show photoluminescence in the telecommunications (∼1550 nm) and green (∼530 nm) optical bands. Incorporating this active optomechanics into the opto-electromechanical system, we propose its use as an on-chip tunable source of coherent light as an important step towards developing fully on-chip optical experiments.We lastly discuss utilising the electrical element of the system not simply as a forcing mechanism, but as a cavity similar to the optical whispering gallery modes, but for microwave light. In this system, the mechanical resonator is coupled to both the optical and microwave cavities, and can be used to transduce signals between the two regimes. In the quantum regime this would allow, for example, transportation of quantum states generated by superconducting qubits through room temperature, an important goal for the quantum computing community. We theoretically analyse the potential of our proposed system, based on a double-disk optomechanical geometry, and present progress towards its experimental implementation.

We report free-spectral-range tuning in a high-quality on-chip microcavity requiring less than 15 V and 1 nW of power to maintain optical resonance with an arbitrary frequency: an important component for achieving reconfigurable photonic circuits.

Reconfigurable photonic circuits have applications ranging from next-generation computer architectures to quantum networks, coherent radar and optical metamaterials. However, complete reconfigurability is only currently practical on millimetre-scale device footprints. Here, we overcome this barrier by developing an on-chip high quality microcavity with resonances that can be electrically tuned across a full free spectral range (FSR). FSR tuning allows resonance with any source or emitter, or between any number of networked microcavities. We achieve it by integrating nanoelectronic actuation with strong optomechanical interactions that create a highly strain-dependent effective refractive index. This allows low voltages and sub-nanowatt power consumption. We demonstrate a basic reconfigurable photonic network, bringing the microcavity into resonance with an arbitrary mode of a microtoroidal optical cavity across a telecommunications fibre link. Our results have applications beyond photonic circuits, including widely tuneable integrated lasers, reconfigurable optical filters for telecommunications and astronomy, and on-chip sensor networks., Comment: Main text: 7 pages, 3 figures. Supplementary information: 7 pages, 9 figures

The techniques of cavity optomechanics have enabled significant achievements in precision sensing, including the detection of gravitational waves and the cooling of mechanical systems to their quantum ground state. Recently, the inherent non-linearity in the optomechanical interaction has been harnessed to explore synchronization effects, including the spontaneous locking of an oscillator to a reference injection signal delivered via the optical field. Here, we present the first demonstration of a radiation-pressure driven optomechanical system locking to an inertial drive, with actuation provided by an integrated electrical interface. We use the injection signal to suppress drift in the optomechanical oscillation frequency, strongly reducing phase noise by over 55 dBc/Hz at 2 Hz offset. We further employ the injection tone to tune the oscillation frequency by more than 2 million times its narrowed linewidth. In addition, we uncover previously unreported synchronization dynamics, enabled by the independence of the inertial drive from the optical drive field. Finally, we show that our approach may enable control of the optomechanical gain competition between different mechanical modes of a single resonator. The electrical interface allows enhanced scalability for future applications involving arrays of injection-locked precision sensors., Comment: Main text: 10 pages, 7 figures. Supplementary Information: 5 pages, 4 figures

Electro-optomechanical systems are a platform for exploring rich physics such as frequency conversion and synchronization. Here we demonstrate the first case of inertial injection locking in a radiation pressure driven electro-optomechanical system.

We report on the design, fabrication and characterization of silica microtoroid based cavity opto-electromechanical systems (COEMS). Electrodes patterned onto the microtoroid resonators allow for rapid capacitive tuning of the optical whispering gallery mode resonances while maintaining their ultrahigh quality factor, enabling applications such as efficient radio to optical frequency conversion, optical routing and switching applications., Comment: 11 pages, 7 figures

This work considers how the properties of hydrogen bonded complexes, D-H....A, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (D) and acceptor (A) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H....O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 A, i.e., from strong to weak bonds. The position of the proton and its longitudinal vibrational frequency, along with the isotope effects in both are discussed. An analysis of the secondary geometric isotope effects, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of the bending modes in also considered: their quantum effects compete with those of the stretching mode for certain ranges of H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several experimental trends., 12 pages, 8 figures. Notation clarified. Revised figure including the effect of bending vibrations on secondary geometric isotope effect. Final version, accepted for publication in Journal of Chemical Physics