Photonic Generation Research Articles

An X-rays-to-radio investigation of the nuclear polarization from the radio-galaxy Centaurus A

ABSTRACT Centaurus A is one of the closest radio galaxies to Earth. Its proximity allowed us to extensively study its active galactic nucleus but the core emission mechanism remains elusive because of local strong dust and gas obscuration. The capability of polarimetry to shave-off contaminating emission has been exploited without success in the near-infrared by previous studies but the very recent measurement of the 2–8 keV polarization by the Imaging X-ray Polarimetry Explorer (IXPE) brought the question back to the fore. To determine what is the prevalent photon generation mechanism to the multiwavelength emission from the core of Centaurus A, we retrieved from the archives the panchromatic polarization measurements of the central compact component. We built the total and polarized flux spectral energy distributions of the core and demonstrated that synchrotron self-Compton models nicely fit the polarized flux from the radio to the X-ray band. The linear polarization of the synchrotron continuum is perpendicular to the jet radio axis from the optical to the radio band, and parallel to it at higher energies. The observed smooth rotation of the polarization angle in the ultraviolet band is attributed to synchrotron emission from regions that are getting closer to the particle acceleration site, where the orientation of the jet’s magnetic fields become perpendicular to the jet axis. This phenomenon support the shock acceleration mechanism for particle acceleration in Centaurus A, in line with IXPE observations of several high-synchrotron peak blazars.

On-Chip Photonic Generation of Tunable Wideband Phase-Coded Linearly-Chirped Microwave Waveforms

On-chip photonic generation of tunable wideband phase-coded linearly-chirped microwave waveforms (PC-LCMWs) is proposed and experimentally demonstrated. The on-chip generation system consists of two main parts. One part is a hybrid Fourier-domain mode-locked opto-electronic oscillator (FDML-OEO) for a wideband linearly-chirped microwave waveform (LCMW) generation; the other part is a high-speed microwave photonic phase shifter (MPPS) to perform the phase-coding. By synchronizing the two parts, a PC-LCMW is finally generated. In the proposed chip, a thermally-tunable ultrahigh-Q micro-ring resonator (MRR) is a key component which is incorporated in the FDML-OEO loop to select the oscillation frequency, and an electrically-tunable micro-disk resonator (MDR), as another key component, is used to code the phase of the generated microwave signal while maintaining the amplitude by controlling the free carrier concentration in the lateral PN junction of the disk. With the use of the two key component chips, an experiment is performed and different PC-LCMWs are generated with a tunable center frequency from 12 to 16 GHz, a bandwidth from 2 to 6 GHz, and phase code of 7-bit and 13-bit Barker code. In particular, a PC-LCMW with a maximum bandwidth as wide as 6 GHz and an ultra-large time-bandwidth product (TBWP) as large as 1.96×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> is experimentally demonstrated. The proposed integrated PC-LCMW generation system holds great advantages including ultracompact configuration and fast tunability, which holds a high potential for applications in modern high-resolution multi-functional radar system.

Twisted moiré photonic crystal enabled optical vortex generation through bound states in the continuum

The twisted stacking of two layered crystals has led to the emerging moiré physics as well as intriguing chiral phenomena such as chiral phonon and photon generation. In this work, we identified and theoretically formulated a non-trivial twist-enabled coupling mechanism in twisted bilayer photonic crystal (TBPC), which connects the bound state in the continuum (BIC) mode to the free space through the twist-enabled channel. Moreover, the radiation from TBPC hosts an optical vortex in the far field with both odd and even topological orders. We quantitatively analyzed the twist-enabled coupling between the BIC mode and other non-local modes in the photonic crystals, giving rise to radiation carrying orbital angular momentum. The optical vortex generation is robust against geometric disturbance, making TBPC a promising platform for well-defined vortex generation. As a result, TBPCs not only provide a new approach to manipulating the angular momentum of photons, but may also enable novel applications in integrated optical information processing and optical tweezers. Our work broadens the field of moiré photonics and paves the way toward the novel application of moiré physics.

Deterministic photon source interfaced with a programmable silicon-nitride integrated circuit

We develop a quantum photonic platform that interconnects a high-quality quantum dot single-photon source and a low-loss photonic integrated circuit made in silicon nitride. The platform is characterized and programmed to demonstrate various multiphoton applications, including bosonic suppression laws and photonic entanglement generation. The results show a promising technological route forward to scale-up photonic quantum hardware.

A newly developed and verified transport capacity of Monte Carlo photon particles in RMC

In reactor shielding designs, deep-penetration shielding issues, and direct photon heating, photon transport physics is crucial. In the Reactor Monte Carlo (RMC) code, a state-of-the-art photon transport capacity is implemented in this research. For criticality and fixed-source calculations, pure photon and coupled neutron-photon transport are now simulated for four photon-atomic interactions, including Rayleigh scattering, Compton scattering, Photoelectric effect, and Pair production, as well as three major processes of the secondary photons generation (Atomic relaxation, Electron-positron annihilation, and Bremsstrahlung by electrons and positrons). In order to properly balance energy release and deposition during neutron-induced photon production, the yield of photons by neutrons is scaled by a correction factor to account for the delayed gamma radiation, and the effective multiplication factor keff is used in an uncritical system. Using an Automatic Library Generator (ALG) code, a new database for photon transport is processed with the ENDF/B evaluated nuclear data library. Numerous cases, such as a point source in an infinite geometry, a photon beam source in a cylinder geometry, and a fuel assembly in the VERA benchmark, are verified against the Monte Carlo (MC) code OpenMC. Despite some notable differences in the comparison of the photon flux at certain energy ranges, which are caused by differences in the database and also the physics implementation, the results of the energy and spatial distributions of photon flux, and the photon heating show generally good agreement and relative errors are nearly within a triple statistical standard deviation. RMC now offers advanced photon transport capacity for reaction core and shielding applications.

Photonic generation of frequency-doubling Nyquist pulses using external modulation.

In this paper, an approach to generate frequency-doubling sinc-shaped optical Nyquist pulses based on external modulation is proposed and demonstrated. First, four flat optical frequency comb (OFC) lines are obtained after optical carrier suppression modulation in a dual-electrode Mach-Zehnder modulator. Then an optical interleaver is introduced to split the phase-locked OFC into two paths, of which one is transmitted to a dual-parallel Mach-Zehnder modulator for quadrupling RF modulation and another is applied to the remodulated signal to acquire comb lines with equal intervals. Thus, a phase-locked 12-line flat OFC with equal frequency intervals and corresponding Nyquist pulses is finally obtained, and Nyquist pulses at 2.5GHz, 5GHz, 10GHz, and 15GHz are achieved.

Quantum Noise Secured Terahertz Communications

The terahertz communications display an important role in high-speed wireless communications, the security threat from the eavesdroppers in the terahertz communications has been gaining attention recently. The true randomness in the physical layer can ensure one-time-pad encryption for secured terahertz communications, however, physical layer security schemes like the quantum key distribution methods suffer from device imperfections that limit the desirable signal rate and link distance. Herein, we present the quantum noise secured terahertz wireless communications with photonic terahertz signal generation schemes. With the high-order diffusion algorithms, the signal is masked by the quantum noise ciphers to the eavesdroppers and cannot be detected because the inevitable randomness by quantum noise measurement will cause physical measurement errors. In the experiment, we demonstrate 16 Gbits <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> quantum noise secured terahertz wireless communications with the conventional optical communication realms and devices, operating at 300 GHz terahertz frequency. This quantum noise secured terahertz communication approach is a significant step toward high-security wireless communications.

Photonic Millimeter Wave Generation and Stabilization in Optically Injected Discrete-Mode Semiconductor Lasers Subject to Photonic Filter Feedback

Photonic millimeter wave signal generation and stabilization based on nonlinear dynamics of optically injected discrete-mode semiconductor lasers with photonic filter feedback are experimentally and numerically studied. The photonic filter is constructed by jointing two ports of a 2×2 optical coupler to form a ring cavity recirculation and is modelled as an infinite impulse response filter. The results show that >30GHz photonic millimeter wave signals can be obtained after optical to electrical conversion of the period-one oscillation output of the optically injected discrete-mode semiconductor laser. More importantly, the linewidth, side peak suppression ratio, as well as the stability of the generated millimeter wave, can be optimized using the photonic filter feedback. A fair comparison of the photonic filter feedback scheme and the single/double optical feedback schemes in terms of optimization performance has been made. The corresponding results demonstrate that the photonic filter feedback scheme has obvious superiority in millimeter wave side peak suppression and stability. The effect of the coupling coefficient as well as the phase variables in the ring cavity has also been discussed in the simulation work and the results qualitatively agree with the experimental observations.

Quantum dots for photonic quantum information technology

The generation, manipulation, storage, and detection of single photons play a central role in emerging photonic quantum information technology. Individual photons serve as flying qubits and transmit the relevant quantum information at high speed and with low losses, for example between individual nodes of quantum networks. Due to the laws of quantum mechanics, the associated quantum communication is fundamentally tap-proof, which explains the enormous interest in this modern information technology. On the other hand, stationary qubits or photonic states in quantum computers can potentially lead to enormous increases in performance through parallel data processing, to outperform classical computers in specific tasks when quantum advantage is achieved. In this review, we discuss in depth the great potential of semiconductor quantum dots in photonic quantum information technology. In this context, quantum dots form a key resource for the implementation of quantum communication networks and photonic quantum computers, because they can generate single photons on demand. Moreover, these solid-state quantum emitters are compatible with the mature semiconductor technology, so that they can be integrated comparatively easily into nanophotonic structures such as resonators and waveguide systems, which form the basis for quantum light sources and integrated photonic quantum circuits. After a thematic introduction, we present modern numerical methods and theoretical approaches to device design and the physical description of quantum dot devices. We then introduce modern methods and technical solutions for the epitaxial growth and for the deterministic nanoprocessing of quantum devices based on semiconductor quantum dots. Furthermore, we highlight the most promising device concepts for quantum light sources and photonic quantum circuits that include single quantum dots as active elements and discuss applications of these novel devices in photonic quantum information technology. We close with an overview of open issues and an outlook on future developments.

Cold Atmospheric Pressure Plasma Jet and Plasma Lamp Interaction with Plants: Electrostimulation, Reactive Oxygen and Nitrogen Species, and Side Effects

Cold atmospheric pressure plasma (CAPP) treatment is a highly effective method of protecting seeds, plants, flowers, and trees from diseases and infection and significantly increasing crop yields. Here we found that cold atmospheric pressure He-plasma jet (CAPPJ) can also cause side effects and damage to plants if the plasma exposure time is too long. Reactive oxygen and nitrogen species (RONS), electromagnetic fields, and ultraviolet photons emitted by CAPPJ can cause both positive and negative effects on plants. CAPPJ can interact with biological tissue surfaces. The plasma lamp has no visible side effects on Aloe vera plants, cabbage, and tomatoes. A plasma lamp and a cold atmospheric pressure plasma He-jet cause strong electrical signaling in plants with a very high amplitude with frequencies equal to the frequency of plasma generation. The use of plasma lamps for electrostimulation of biological tissues can help to avoid side processes in biological tissues associated with the generation of RONS, UV photons, and direct interaction with cold plasma. CAPP technology can play an important role in agriculture, medicine, the food industry, chemistry, surface science, material science, and engineering applications without side effects if the plasma exposure is short enough.

Photonic generation of triangular waveform with tunable symmetry based on channelized frequency synthesis.

A symmetry tunable triangular waveform photonic generator based on channelized frequency synthesis is proposed and studied. The generator adopts a multichannel system architecture and harmonic amplitude control algorithm to physically isolate each subchannel. In a single subchannel, quadrature phase shift keying modulation and coherent dual-wavelength balanced detection are used to realize optical upconversion and suppress mixing interference in the process of frequency conversion. Therefore, the model has the characteristics of a high-order Fourier series fitting tunable function waveform output. The analysis results show that the Fourier series harmonic coefficients can be adjusted flexibly by the multivariable joint regulation algorithm. The relationship between the variables is analyzed and discussed. The feasibility of the scheme is verified by optical simulation; when the rms error (RMSE)≤0.03, a 20%-80% tunable symmetry triangular waveform can be obtained.

Interdimensional radial discrete diffraction in Mathieu photonic lattices.

We demonstrate transitional dimensionality of discrete diffraction in radial-elliptical photonic lattices. Varying the order, characteristic structure size, and ellipticity of the Mathieu beams used for the photonic lattices generation, we control the shape of discrete diffraction distribution over the combination of the radial direction with the circular, elliptic, or hyperbolic. We also investigate the transition from one-dimensional to two-dimensional discrete diffraction by varying the input probe beam position. The most pronounced discrete diffraction is observed along the crystal anisotropy direction.

On-chip generation of single-photon circularly polarized single-mode vortex beams.

Generation of single photons carrying spin and orbital angular momenta (SAM and OAM) opens enticing perspectives for exploiting multiple degrees of freedom for high-dimensional quantum systems. However, on-chip generation of single photons encoded with single-mode SAM-OAM states has been a major challenge. Here, by using carefully designed anisotropic nanodimers fabricated atop a substrate, supporting surface plasmon polariton (SPP) propagation, and accurately positioned around a quantum emitter (QE), we enable nonradiative QE-SPP coupling and the SPP outcoupling into free-space propagating radiation featuring the designed SAM and OAM. We demonstrate on-chip room-temperature generation of well-collimated (divergence < 7.5°) circularly polarized (chirality > 0.97) single-mode vortex beams with different topological charges (𝓁 = 0, 1, and 2) and high single-photon purity, g(2)(0) < 0.15. The developed approach can straightforwardly be extended to produce multiple, differently polarized, single-mode single-photon radiation channels and enable thereby realization of high-dimensional quantum sources for advanced quantum photonic technologies.

Frequency-angular spectrum of entangled photon pairs generated by focused pump

Spontaneous parametric down-conversion (SPDC) is a well-established method for generating entangled photon pairs, and their frequency-angular spectrum properties are of significant interest in various applications. Generally, the focused pump can increase the efficiency of single-mode photons generation, and lead to the asymmetric broadening of the SPDC emission cone relative to plane wave, while our analysis shows it will be further intensified when the pump divergence exceeds 1.3°. In this paper, we propose a theoretical model for accurately ascertaining the frequency-angular spectrum of entangled photon pairs produced by arbitrary pumps, then obtain complete spatial distribution and spectral properties of type I and II SPDC photons, and further demonstrate its validity referring to experimental results of other researchers. Our method is available for high-efficient generation of entangled photon pairs through optimizing crystal orientation, pump beam focus, and detection geometry.

Two-photon interference from silicon-vacancy centers in remote nanodiamonds

Abstract The generation of indistinguishable photons is a key requirement for solid-state quantum emitters as a viable source for applications in quantum technologies. Restricting the dimensions of the solid-state host to a size well below the wavelength of light emitted by a defect-center enables efficient external optical coupling, for example, for hybrid integration into photonic devices. However, stringent restrictions on the host dimensions result in severe limitations on the spectral properties reducing the indistinguishability of emitted photons. Here, we demonstrate two-photon interference from two negatively charged silicon-vacancy centers located in remote nanodiamonds. The Hong–Ou–Mandel interference efficiency reaches 61 % with a coalescence time window of 0.35 ns. We furthermore show a high yield of pairs of silicon-vacancy centers with indistinguishable optical transitions. Therefore, our work opens new paths in hybrid quantum technology based on indistinguishable single-photon emitters in nanodiamonds.

Photonic generation of multi-format chirped signals with a high switching rate.

A novel photonic method for multi-format chirped signal generation with a high switching rate based on a dual-polarization binary phase shift keying (DP-BPSK) modulator is proposed and demonstrated. An up-chirp signal and a binary code signal are used to drive one of the sub-dual-drive Mach-Zehnder modulators (sub-DDMZMs) integrated in the DP-BPSK modulator. Another integrated sub-DDMZM is driven by a down-chirp signal and another binary code signal. By carefully tuning the DC biases of the DP-BPSK modulator, the format of the output chirped signal is controlled by the binary code signals. A proof-of-concept experiment is performed and multi-format chirped signals with a high switching rate are generated. Due to the high switching rate, simple structure, and high adjustability, the proposed multi-format chirped signal generator may find potential applications in multifunctional radar systems, wireless communication systems, and dual-function radar-communication systems.

High-Speed and wideband multilevel Frequency-Hopping microwave signal generation based on a Sagnac loop

An approach for photonic generation of multilevel frequency-hopping (FH) microwave signal based on a Sagnac loop is proposed and investigated. In the Sagnac loop, several Mach-Zehnder Interferometers (MZI), driven by the coding signals, are connected in series to act as a tunable photonic filter. By carefully adjusting the coding signals, the photonic filter can select the specific frequency component from the input optical frequency comb (OFC), so as to generate multilevel FH microwave signal. Theoretical analysis and simulation works are performed to demonstrate a 7-level FH microwave signal generator, and the discussion about the impact of non-ideal factors is given. The approach features high FH speed, wideband and amenable to photonic integration. In addition, the Sagnac loop ensures the equal optical path for clockwise and counterclockwise lights, which can enhance signal performance due to the better phase stability.

Future Green Technology: A Freezing Water Micro-Droplet as an Optical Switch Based on a Time-Domain Photonic Hook.

This paper pays attention to the broader interest of freezing water droplets in mesotronics, particularly to their use as a new all-optical device platform. Here, we show that a freezing mesoscale water droplet with a low Bond number can behave as fully biocompatible natural microlense to form a photonic hook for application in a tunable temperature-controlled optical switch. We first introduced and demonstrated the basic concepts of an optical switch without changes in the wavelength of illumination of a particle or any moving parts being involved. The principle of the operation of the switch is based on the temperature-induced phase change inside the water droplet's refractive index. The simulation results show that the optical isolation of switched channels for an optical switch with linear dimensions of about 15 λ3 based on a freezing water droplet can reach 10 dB in the process of temperature variation at a fixed wavelength. The use of freezing mesoscale droplets acting as a time-domain photonic hook generator open an intriguing route for optical switching in multifunctional green electronics tools for sensing, integrated optics and optical computers.

Photonic generation of ASK microwave signals with SSB format.

Optical beating is the usual approach to generation of microwave signals. However, the highest frequency achievable for microwave signals is limited by the bandwidths of optoelectronic devices. To maximize the microwave frequency with a limited bandwidth of a photodetector (PD) and relieve the bandwidth bottleneck, we propose to generate microwave signals with the single sideband (SSB) format by beating a continuous wave (CW) light with an optical SSB signal. By simply adjusting the frequency difference between the CW light and the carrier of the optical SSB signal, the frequency of the generated microwave SSB signal is changed correspondingly. In the experiment, amplitude shift keying (ASK) microwave signals with the SSB format are successfully generated with different carrier frequencies and coding bit rates, and the recovered coding information agrees well with the original pseudo random binary sequence (PRBS) of 27 - 1 bits. The proposed approach can significantly relieve the bandwidth restriction set by optoelectronic devices in high-speed microwave communication systems.

Observing multiple processes of backward-phase-matching spontaneous parametric downconversion in a single-periodic crystal.

A nonlinear process based on backward quasi-phase matching (BQPM) can be used to realize mirrorless optical parametric oscillation, the generation of paired photons with a separable joint spectral amplitude and narrow wavelength bandwidth, and the preparation of counterpropagating polarization-entangled photons, which shows distinct advantages over some applications based on forward quasi-phase matching. In this work, three types of BQPM in a bulk periodically poled potassium titanyl phosphate crystal with a single period are theoretically analyzed. Experimentally, the harmonic wave generated by second-harmonic generation in type 0 and type I exhibits a narrow bandwidth of 15.5 GHz. Furthermore, photon pairs generated by spontaneous parametric downconversion in all types of BQPM (type 0, type I, and type II) at 7th order are observed and characterized. Their coincidence-to-accidental ratios are all greater than 5 × 103 in the pump power range from 10 mW to 500 mW. This research lays the foundation for further applications of BQPM in nonlinear optics, quantum optics, and quantum information processing.