Optoelectronic parametric oscillator

Oscillators are one of the key elements in various applications as a signal source to generate periodic oscillations.Among them,an optical parametric oscillator(OPO)is a driven harmonic oscillator based on parametric frequency conversion in an optical cavity,which has been widely investigated as a coherent light source with an extremely wide wavelength tuning range.However,steady oscillation in an OPO is confined by the cavity delay,which leads to difficulty in frequency tuning,and the frequency tuning is discrete with the minimum tuning step determined by the cavity delay.Here,we propose and demonstrate a counterpart of an OPO in the optoelectronic domain,i.e.,an optoelectronic parametric oscillator(OEPO)based on parametric frequency conversion in an optoelectronic cavity to generate microwave signals.Owing to the unique energy-transition process in the optoelectronic cavity,the phase evolution in the OEPO is not linear,leading to steady single-mode oscillation or multimode oscillation that is not bounded by the cavity delay.Furthermore,the multimode oscillation in the OEPO is stable and easy to realize owing to the phase control of the parametric frequency-conversion process in the optoelectronic cavity,while stable multimode oscillation is difficult to achieve in conventional oscillators such as an optoelectronic oscillator(OEO)or an OPO due to the mode-hopping and mode-competition effect.The proposed OEPO has great potential in applications such as microwave signal generation,oscillator-based computation,and radio-frequency phase-stable transfer.

Recent advances in optoelectronic oscillators

An optoelectronic oscillator(OEO)is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element.This type of oscillator is desired in various practical applications,such as communication links,signal processing,radar,metrology,radio astronomy,and reference clock distribution.Recently,new mode control and selection methods based on Fourier domain mode-locking and parity-time symmetry have been proposed and experimentally demonstrated in OEOs,which overcomes the long-existing mode building time and mode selection problems in a traditional OEO.Due to these mode control and selection methods,continuously chirped microwave waveforms can be generated directly from the OEO cavity and single-mode operation can be achieved without the need of ultranarrowband filters,which are not possible in a traditional OEO.Integrated OEOs with a compact size and low power consumption have also been demonstrated,which are key steps toward a new generation of compact and versatile OEOs for demanding applications.We review recent progress in the field of OEOs,with particular attention to new mode control and selection methods,as well as chip-scale integration of OEOs.

Microwave photonics: radio-over-fiber links, systems, and applications [Invited]

Microwave photonics(MWPs)uses the strength of photonic techniques to generate,process,control,and distribute microwave signals,combining the advantages of microwaves and photonics.As one of the main topics of MWP,radio-over-fiber(RoF)links can provide features that are very difficult or even impossible to achieve with traditional technologies.Meanwhile,a considerable number of signal-processing subsystems have been carried out in the field of MWP as they are instrumental for the implementation of many functionalities.However,there are still several challenges in strengthening the performance of the technology to support systems and applications with more complex structures,multiple functionality,larger bandwidth,and larger processing capability.In this paper,we identify some of the notable challenges in MWP and review our recent work.Applications and future direction of research are also discussed.

Dissipative microwave photonic solitons in spontaneous frequency-hopping optoelectronic oscillators

Dissipative solitons relying on the double balance between nonlinear and linear effects as well as cavity loss and gain have attracted increasing attention in recent years,since they give rise to novel operating states of various dissipative nonlinear systems.An optoelectronic oscillator(OEO)is a dissipative nonlinear microwave photonic system with a high quality factor that has been widely investigated for generating ultra-low noise single-frequency microwave signals.Here,we report a novel operating state of an OEO related to dissipative solitons,i.e.,spontaneous frequency hopping related to the formation of dissipative microwave photonic solitons.In this operating state,dissipative microwave photonic solitons occur due to the double balance between nonlinear gain saturation and linear filtering as well as cavity loss and gain in the OEO cavity,creating spontaneous frequencyhopping microwave signals.The generation of wideband tunable frequency-hopping microwave signals with a fast frequency-hopping speed up to tens of nanoseconds is observed in the experiment,together with the corresponding soliton sequences.This work reveals a novel mechanism between the interaction of nonlinear and linear effects in an OEO cavity,extends the suitability and potential applications of solitons,and paves the way for a new class of soliton microwave photonic systems for the generation,processing,and control of microwave and RF signals.

Large-scale coherent Ising machine based on optoelectronic parametric oscillator

Ising machines based on analog systems have the potential to accelerate the solution of ubiquitous combinatorial optimization problems.Although some artificial spins to support large-scale Ising machines have been reported,e.g.,superconducting qubits in quantum annealers and short optical pulses in coherent Ising machines,the spin stability is fragile due to the ultra-low equivalent temperature or optical phase sensitivity.In this paper,we propose to use short microwave pulses generated from an optoelectronic parametric oscillator as the spins to implement a large-scale Ising machine with high stability.The proposed machine supports 25,600 spins and can operate continuously and stably for hours.Moreover,the proposed Ising machine is highly compatible with high-speed electronic devices for programmability,paving a low-cost,accurate,and easy-to-implement way toward solving real-world optimization problems.

Observation of parity-time symmetry in time-division multiplexing pulsed optoelectronic oscillators within a single resonator

In recent years,parity-time(PT)symmetry in optoelectronic systems has been widely studied,due to its potential applications in lasers,sensors,topological networks,and other fields.In this paper,a time-division multiplexed pulsed optoelectronic oscillator(OEO)is proposed to study the dynamics of a PT symmetry system.Two microwave pulses are used to realize the PT symmetry in a single spatial resonator based on the temporal degrees of freedom.The gain and loss of the microwave pulses and the coupling coefficient between them can then be controlled.We first demonstrate the phase diagram from PT broken to PT symmetry in the OEO system.We theoretically prove that the perturbation of a coupling-induced phase shift larger than(2π)×10^(-2)causes the disappearance of the PT symmetry.In this experiment,the perturbation is less than(2π)×0.5×10^(-2);thus,the phase transition of PT symmetry is observed.In addition,multipairs of PT-symmetry pulses indicate that pulsed OEO could be used to implement complex non-Hermitian Hamilton systems.Therefore,it is confirmed that pulsed OEO is an excellent platform to explore the dynamics of PT symmetry and other non-Hermitian Hamiltonian systems.

Low-latency full-field temporal magnification based on spectral compression

Temporal magnification is an emerging technology for the observation of single-shot optical signals with irregular and ultrafast dynamics,which exceed the speed,precision,and record length of conventional digitizers.Conventional temporal magnification schemes suffer from transmission delay and large volume of dispersive elements.Because only the signal envelope can be magnified in the dispersion-based schemes,real-time full-field(phase and amplitude)measurement for a complex ultrafast optical signal remains an open challenge.Here,a bandwidth-compressed temporal magnification scheme for low-latency full-field measurements of ultrafast dynamics is proposed.Unlike the dispersion-based schemes,temporal magnification of a complex optical signal is achieved by bandwidth compression.The bandwidth is coherently compressed by the Vernier effect relying on the detuned free spectral range of a periodic optical filter and time lens.Experimentally,a temporal magnification factor of 224 is realized,and full-field measurements for picosecond pulses are demonstrated.The proposal eliminates the dependence on dispersive elements and shows great potential in integration,which may pave a new path toward full-field measurement for nonrepetitive and statistically rare signals.