All-optical Generation Research Articles

All-optical generation of Abrikosov vortices by the inverse Faraday effect

Within the framework of the time-dependent Ginzburg-Landau theory we show that circularly polarized terahertz or far-infrared radiation induces a dc supercurrent that influences the dynamics of vortex-antivortex pair formation in a mesoscopic superconductor undergoing rapid thermal quenching. The Lorentz force arising from the supercurrents promotes vortex-antivortex separation and allows survival of the vortex polarity defined by the helicity of light. Based on this idea, we propose a two-stage irradiation scheme that provides a powerful method for controlled all-optical generation of Abrikosov vortices.

All-optical generation of deterministic squeezed Schrödinger-cat states

Quantum states are important resources and their preparations are essential prerequisites to all quantum technologies. However, they are extremely fragile due to the inevitable dissipations. Here the all-optical generation of a deterministic squeezed Schr\"odinger-cat state based on dissipation is proposed. Our system is based on the Fredkin-type interaction between three optical modes, one of which is subject to coherent two-photon driving and the others are coherent driving. We show that an effective degenerate three-wave-mixing process can be engineered in our system, which can cause the simultaneous loss of two photons, resulting in the generation of a deterministic squeezed Schr\"odinger-cat state. More importantly, by controlling the driving fields in our system, the two-photon loss can be adjustable, which can accelerate the generation of squeezed Schr\"odinger-cat states. In addition, we exploit the squeezed Schr\"odinger-cat states to estimate the phase in the optical interferometer and show that the quantum Fisher information about the phase can reach the Heisenberg limit in the limit of a large photon number. Meanwhile, it can have an order of magnitude factor improvement over the Heisenberg limit in the low-photon-number regime, which is very valuable for fragile systems that cannot withstand large photon fluxes. This work proposes an all-optical scheme to deterministically prepare the squeezed Schr\"odinger-cat state with high speed and can also be generalized to other physical platforms.

Photonic Generation of a Windowed Phase-Coded Microwave Waveform With Suppressed Spectrum Sidelobes

An approach to photonic generation of a windowed binary phase-coded microwave waveform with suppressed spectrum sidelobes is proposed and demonstrated. An optical double sideband plus carrier signal with the carrier and the two sidebands being orthogonally polarized is generated by a dual-polarization quadrature phase shift keying (DP-QPSK) modulator, with the generated signal sent to a phase modulator (PM) where phase coding is performed. The PM can support phase modulation in two orthogonal polarization directions. The phase-modulated signals are projected to one polarization direction and detected at a photodetector (PD). Switching the polarity of the coding signal, a π phase shift is introduced. Since the amplitude of the generated signal is dependent on the amplitude of the input coding signal, a windowing function is applied to the generated waveform by using a windowed input phase coding signal, to suppress the sidelobes in the spectrum of the generated microwave waveform. The key features of the proposed waveform generator include all-optical generation without the need of electronic components and optical filters, thus ensuring a wide operating frequency range. The proposed phase-coded microwave waveform generator also has the ability to switch between the fundamental and harmonic carrier frequency by controlling the modulator bias voltages. Experimental results show that, using a windowed 64-bit Gaussian pseudo-random binary sequence coding signal, a phase-coded microwave waveform is generated with the sidelobes of the spectrum largely suppressed by 20 dB and a pulse compression ratio as large as 133. Generation of binary phase-coded microwave waveforms at the 2nd harmonic carrier frequencies is also demonstrated experimentally.

All-Optical Generation and Time-Resolved Polarimetry of Magnetoacoustic Resonances via Transient Grating Spectroscopy

The generation and control of surface acoustic waves (SAWs) in a magnetic material are objects of an intense research effort focused on magnetoelastic properties, with fruitful ramifications in spin-wave-based quantum logic and magnonics. We implement a transient grating setup to optically generate SAWs also seeding coherent spin waves via magnetoelastic coupling in ferromagnetic media. In this work we report on SAW-driven ferromagnetic resonance (FMR) experiments performed on polycrystalline Ni thin films in combination with time-resolved Faraday polarimetry, which allows extraction of the value of the effective magnetization and of the Gilbert damping. The results are in full agreement with measurements on the very same samples from standard FMR. Higher-order effects due to parametric modulation of the magnetization dynamics, such as down-conversion, up-conversion, and frequency mixing, are observed, testifying the high sensitivity of this technique.

All-optical, tunable, V- and W-band microwave generation using semiconductor lasers at period-one nonlinear dynamics with asymmetric mutual injection stabilization.

This study investigates an optically injected semiconductor laser operating at period-one nonlinear dynamics for all-optical microwave generation. A novel, to the best of our knowledge, all-optical stabilization scheme is proposed to greatly enhance the spectral purity of such generated microwaves, which sends a small fraction of the injected laser output back to the injecting laser, not the injected laser itself. Mutual injection with highly different injection power between the two lasers, i.e., highly asymmetric mutual injection, is thus formed. As a result, the microwave linewidth is reduced by up to at least 85 times, the phase noise variance is improved by up to at least 750 times, and a side-peak suppression ratio of more than 44 dB is achieved. Microwave generation that is tunable up to at least 110 GHz with a 3-dB linewidth down to below 2 kHz is realized.

Microring resonator-based all-optical parallel pseudo random binary sequence generator for rate multiplication.

In this paper, we design an all-optical Pseudo Random Binary Sequence (PRBS) generator in parallel configuration for operating rate multiplication purposes. The sequential circuit comprises of several clocked D flip-flops, XOR gates and multiplexers implemented using microring resonator (MRR)-based switches. The proposed design is demonstrated and validated through simulations for 500 Gb/s and 400 Gb/s rate doubling and quadrupling, respectively, of a 5-bit degree PRBS. The MRR critical operating parameters are also optimized against performance metrics through numerical investigation.

Nonlinear co-generation of graphene plasmons for optoelectronic logic operations

Surface plasmons in graphene provide a compelling strategy for advanced photonic technologies thanks to their tight confinement, fast response and tunability. Recent advances in the field of all-optical generation of graphene’s plasmons in planar waveguides offer a promising method for high-speed signal processing in nanoscale integrated optoelectronic devices. Here, we use two counter propagating frequency combs with temporally synchronized pulses to demonstrate deterministic all-optical generation and electrical control of multiple plasmon polaritons, excited via difference frequency generation (DFG). Electrical tuning of a hybrid graphene-fibre device offers a precise control over the DFG phase-matching, leading to tunable responses of the graphene’s plasmons at different frequencies across a broadband (0 ~ 50 THz) and provides a powerful tool for high-speed logic operations. Our results offer insights for plasmonics on hybrid photonic devices based on layered materials and pave the way to high-speed integrated optoelectronic computing circuits.

Tunable all-optical microwave signal generation based on period-one dynamics of an external optically injected distributed-feedback laser diode and feedback oscillation

A tunable all-optical microwave generator based on period-one (P1) dynamics of an external optically injected distributed-feedback laser diode (DFB-LD) is proposed and demonstrated. A DFB-LD implements the functions of light source, microwave frequency selection, and optical–optical modulation. To overcome the frequency drift in P1 oscillation process, a set of reference frequencies from a fiber ring laser (FRL) is introduced. Once the P1 oscillation signal and the modes of FRL are coupled, the whole system is closed and a stable frequency determined by P1 oscillation can be established. In the experimental verification, tunable photonic microwave signals with frequencies from 6.42 to 21.36 GHz are obtained. The measured single-sideband phase noise is −83 dBc / Hz at 10-kHz offset, which is operation frequency independent.

All-optical microwave waveform transformation based on photonic temporal processors.

An all-photonic approach of microwave waveforms generation and transformation is proposed and experimentally demonstrated. From the perspective of envelope function operation in time domain, an initial triangular waveform is transformed into square waveform and sawtooth (or reversed-sawtooth) waveform via two types of differentiators, respectively. In addition, by using a SOA as a multiplier, both bright and dark parabolic pulses are achieved, which are further transformed into sawtooth (or reversed-sawtooth) waveform by taking the first derivative operation. The feasibility of the system is verified by theoretical analysis and simulation. In experiment, all of the expected results are successfully demonstrated and agree with the theoretical analysis well. This scheme provides a novel access to implement all-optical microwave waveforms generation, transformation, signal processing and computing.

Laser-based ultrasound interrogation of surface and sub-surface features in advanced manufacturing materials

Structures formed by advanced manufacturing methods increasingly require nondestructive characterization to enable efficient fabrication and to ensure performance targets are met. This is especially important for aerospace, military, and high precision applications. Surface acoustic waves (SAW) generated by laser-based ultrasound can detect surface and sub-surface defects relevant for a broad range of advanced manufacturing processes, including laser powder bed fusion (LPBF). In particular, an all-optical SAW generation and detection configuration can effectively interrogate laser melt lines. Here we report on scattered acoustic energy from melt lines, voids, and surface features. Sub-surface voids are also characterized using X-ray Computed Tomography (CT). High resolution CT results are presented and compared with SAW measurements. Finite difference simulations inform experimental measurements and analysis.

All-optical quasi-monoenergetic GeV positron bunch generation by twisted laser fields

Generation of energetic electron-positron pairs using multi-petawatt (PW) lasers has recently attracted increasing interest. However, some previous laser-driven positron beams have severe limitations in terms of energy spread, beam duration, density, and collimation. Here we propose a scheme for the generation of dense ultra-short quasi-monoenergetic positron bunches by colliding a twisted laser pulse with a Gaussian laser pulse. In this scheme, abundant γ-photons are first generated via nonlinear Compton scattering and positrons are subsequently generated during the head-on collision of γ-photons with the Gaussian laser pulse. Due to the unique structure of the twisted laser pulse, the positrons are confined by the radial electric fields and experience phase-locked-acceleration by the longitudinal electric field. Three-dimensional simulations demonstrate the generation of dense sub-femtosecond quasi-monoenergetic GeV positron bunches with tens of picocoulomb (pC) charge and extremely high brilliance above 1014 s−1 mm−2 mrad−2 eV−1, making them promising for applications in laboratory physics and high energy physics.

Generation and Control of Terahertz Spin Currents in Topology-Induced 2D Ferromagnetic Fe3 GeTe2 |Bi2 Te3 Heterostructures.

Future information technologies for low-dissipation quantum computation, high-speed storage, and on-chip communication applications require the development of atomically thin, ultracompact, and ultrafast spintronic devices in which information is encoded, stored, and processed using electron spin. Exploring low-dimensional magnetic materials, designing novel heterostructures, and generating and controlling ultrafast electron spin in 2D magnetism at room temperature, preferably in the unprecedented terahertz (THz) regime, is in high demand. Using THz emission spectroscopy driven by femtosecond laser pulses, optical THz spin-current bursts at room temperature in the 2D van der Waals ferromagnetic Fe3 GeTe2 (FGT) integrated with Bi2 Te3 as a topological insulator are successfully realized. The symmetry of the THz radiation is effectively controlled by the optical pumping incidence and external magnetic field directions, indicating that the THz generation mechanism is the inverse Edelstein effect contributed spin-to-charge conversion. Thickness-, temperature-, and structure-dependent nontrivial THz transients reveal that topology-enhanced interlayer exchange coupling increases the FGT Curie temperature to room temperature, which provides an effective approach for engineering THz spin-current pulses. These results contribute to the goal of all-optical generation, manipulation, and detection of ultrafast THz spin currents in room-temperature 2D magnetism, accelerating the development of atomically thin high-speed spintronic devices.

All-optical pulse-train generation through the temporal analogue of a laser

We propose a novel scheme for the all-optical generation of pulse trains in optical fibers based on the reflection and refraction of pulses at a time boundary, and the temporal analogue of a laser cavity with gain. Furthermore, this scheme is shown to provide an original and simple way to measure distributed fiber parameters. In particular, we put forth an application of the temporal laser to the distributed sensing of the fiber group-velocity dispersion parameter.

An Investigation about All-optical Millimeter Wave Generation Technology for High-speed Communication

With the advent of the network information age, users have higher and higher requirements for the bandwidth and capacity of communication systems. Traditional cellular mobile communications can no longer meet the needs of modern communication systems. It is necessary to find a communication system with larger capacity, higher bandwidth and higher transmission rate. Millimeter wave (MMW) communication has high bandwidth, large capacity and high signal transmission rate. Nowadays, all-optical MMW technology generates high-frequency MMW signals in optical domain, which has become a research hotspot of MMW signal generation technology at home and abroad. In this paper, three typical all-optical MMW generation methods are discussed, including direct modulation method, optical heterodyne method and external modulation method. The advantages and disadvantages of each method are analyzed, and the development prospects of the all-optical MMW generation technology are prospected. It is helpful to research new optical MMW technology in the future.

Real-time all-optical random numbers based on optical Boolean chaos.

In this work, a method of generating all-optical random numbers based on optical Boolean chaotic entropy source is proposed. This all-optical random number generation system consists of a Boolean chaotic entropy source and an optical D flip-flop. The Boolean chaotic entropy source is composed of an optical XOR gate and two self-delayed feedback; meanwhile, the optical D flip-flop is composed of two optical AND gates and one SR latch. The optical Boolean chaotic signal possesses the dynamic characteristics of complexity and binarization, so random numbers would be generated only by extracted from chaotic signals with the optical D flip-flop. This all-optical random number generation system achieves the result of 5 Gb/s random numbers that is testable. The whole process of random number generation could be completed in the optical domain without photoelectric conversion, more importantly, the device could be integrated.

All-Optical Non-Inverted Parity Generator and Checker Based on Semiconductor Optical Amplifiers

An all-optical non-inverted parity generator and checker based on semiconductor optical amplifiers (SOAs) are proposed with four-wave mixing (FWM) and cross-gain modulation (XGM) non-linear effects. A 2-bit parity generator and checker using by exclusive NOR (XNOR) and exclusive OR (XOR) gates are implemented by first SOA and second SOA with 10 Gb/s return-to-zero (RZ) code, respectively. The parity and check bits are provided by adjusting the center wavelength of the tunable optical bandpass filter (TOBPF). A saturable absorber (SA) is used to reduce the negative effect of small signal clock (Clk) probe light to improve extinction ratio (ER) and optical signal-to-noise ratio (OSNR). For Pe and Ce (even parity bit and even check bit) without Clk probe light, ER and OSNR still maintain good performance because of the amplified effect of SOA. For Po (odd parity bit), ER and OSNR are improved to 1 dB difference for the original value. For Co (odd check bit), ER is deteriorated by 4 dB without SA, while OSNR is deteriorated by 12 dB. ER and OSNR are improved by about 2 dB for the original value with the SA. This design has the advantages of simple structure and great integration capability and low cost.

Self-Switching Kerr Oscillations of Counterpropagating Light in Microresonators.

We report the experimental and numerical observation of oscillatory antiphase switching between counterpropagating light beams in Kerr ring microresonators, where dominance between the intensities of the two beams is periodically or chaotically exchanged. Self-switching occurs in balanced regimes of operation and is well captured by a simple coupled dynamical system featuring only the self- and cross-phase Kerr nonlinearities. Switching phenomena are due to temporal instabilities of symmetry-broken states combined with attractor merging, which restores the broken symmetry on average. Self-switching of counterpropagating light is robust for realizing controllable, all-optical generation of waveforms, signal encoding, and chaotic cryptography.

Design of all-optical parity bit generator and checker using semiconductor material based devices

Design of all-optical parity bit generator and checker using semiconductor material based devices

All-optical flexible 5G signal generation and transmission for spectrum resource optimization

As available spectrum gets congested by different applications, spectral efficiency can be enhanced through spectrum sharing and coexistence. In this paper, we demonstrate the idea of spectrum sharing and coexistence by using optical heterodyning as a flex-spectrum photonic RF transmitter. Flexibility was achieved by tuning the RF carrier frequency from 1–5 GHz, frequencies around two spectra from a commercial telecom antenna and from a radio astronomy observatory area. We compared the spectrum of our adopted flex-spectrum photonic RF transmitter with these two practical spectra. This allowed us to demonstrate the feasibility of our adopted photonic RF transmitter to coexist with these distinct spectra. Results indicated that it is feasible to use these adopted photonic transmitters in different application environments for coexistence and spectrum sharing. Error-free 26 km fiber transmission was achieved at 2.1 Gbps and 8.5 Gbps. This further showed the feasibility of these photonic RF transmitters for controlled transfer of different data signals relating to different applications using the same RF channel.

Proposal for ultrafast all-optical pseudo random binary sequence generator using microring resonator-based switches

An all-optical pseudo-random binary sequence (PRBS) generator is designed and simulated employing micro-ring resonators (MRRs) as the core technology. The PRBS generator consists of serially connected D flip-flops realized with double-bus MRR-based switches that exploit two-photon absorption induced in a pump-probe configuration, and of a MRR-based feedback XOR gate whose design is simpler than previously reported. The expected operation is theoretically validated for 3-bit and 4-bit degree PRBS generators and can be extended to higher PRBS orders with the straightforward addition of extra MRR-based D flip-flops. The MRR critical parameters, including radius, coupling coefficient and detuning, are optimized against performance metrics through numerical simulation at 250 Gb/s. The selection of these parameters according to the derived specifications can render feasible the practical implementation of the scheme and its exploitation for all-optical signal processing purposes.