Showing papers on "Four-wave mixing published in 2019"

Anti-Parity-Time Symmetric Optical Four-Wave Mixing in Cold Atoms.

Abstract: Non-Hermitian optical systems with parity-time (PT) symmetry have recently revealed many intriguing prospects that outperform conservative structures. The previous works are mostly rooted in complex arrangements with controlled gain-loss interplay. Here, we demonstrate anti-PT symmetry inherent in the nonlinear optical interaction based upon forward optical four-wave mixing in a laser-cooled atomic ensemble with negligible linear gain and loss. We observe that the pair of frequency modes undergo a nontrivial anti-PT phase transition between coherent power oscillation and optical parametric amplification in presence of a large phase mismatch.

Effective four-wave mixing in the lithium niobate on insulator microdisk by cascading quadratic processes.

Abstract: Whispering-gallery-mode resonators can dramatically enhance the light-matter interaction, benefitting nonlinear optics in many ways. Here, we demonstrate effective four-wave mixing (FWM) in a lithium niobate on insulator (LNOI) microdisk via cascaded quadratic nonlinear processes of second-harmonic generation and difference-frequency generation (i.e., cSHG/DFG) in the telecommunication band. The effective FWM process can be used as an optical parametric amplifier and can mimic an effectively strong Kerr nonlinearity. This shows the great promise of an integrated LNOI platform for nonlinear frequency conversion.

Octave-wide phase-matched four-wave mixing in dispersion-engineered crystalline microresonators

Abstract: This erratum presents the corrections to the Letter published in Opt. Lett.44, 3146 (2019)OPLEDP0146-959210.1364/OL.44.003146.

Microwave-to-optical conversion via four-wave mixing in a cold ytterbium ensemble

Abstract: Interfacing superconducting qubits with optical photons require noise-free microwave-to-optical transducers, a technology currently not realized at the single-photon level. We propose to use four-wave mixing in an ensemble of cold ytterbium (Yb) atoms prepared in the metastable ``clock'' state. The parametric process uses two high-lying Rydberg states for bidirectional conversion between a 10 GHz microwave photon and an optical photon in the telecommunication E-band. To avoid noise photons due to spontaneous emission, we consider continuous operation far detuned from the intermediate states. We use an input-output formalism to predict conversion efficiencies of $\ensuremath{\approx}50%$ with bandwidths of $\ensuremath{\approx}100$ kHz.

Versatile and precise quantum state engineering by using nonlinear interferometers.

Abstract: The availability of photon states with well-defined temporal modes is crucial for photonic quantum technologies. Ever since the inception of generating photonic quantum states through pulse pumped spontaneous parametric processes, many exquisite efforts have been put on improving the modal purity of the photon states to achieve single-mode operation. However, because the nonlinear interaction and linear dispersion are often mixed in parametric processes, limited successes have been achieved so far only at some specific wavelengths with sophisticated design. In this paper, we resort to a different approach by exploiting an active filtering mechanism originated from interference fringe of nonlinear interferometer. The nonlinear interferometer is realized in a sequential array of nonlinear medium, with a gap in between made of a linear dispersive medium, in which the precise modal control is realized without influencing the phase matching of the parametric process. As a proof-of-principle demonstration of the capability, we present a photon pairs source using a two-stage nonlinear interferometer formed by two identical nonlinear fibers with a standard single mode fiber in between. The results show that spectrally correlated two-photon state via four wave mixing in a single piece nonlinear fiber is modified into factorable state and heralded single-photons with high modal purity and high heralding efficiency are achievable. This novel quantum interferometric method, which can improve the quality of the photon states in almost all the aspects such as modal purity, heralding efficiency, and flexibility in wavelength selection, is proved to be effective and easy to realize.

Supercontinuum generation by intermodal four-wave mixing in a step-index few-mode fibre

Abstract: We demonstrate broadband supercontinuum generation from 560 nm up to 2350 nm by coupling a simple Q-switched picosecond laser at 1064 nm into a normally dispersive step-index few-mode optical fiber designed to support five modes. It is further shown that multiple cascaded intermodal four-wave mixing and Raman processes occur in the fiber leading to the generation of new frequency components with far detuning up to 165 THz. The multimode properties of this fiber yield a number of intermodal nonlinear coupling terms, and we compare the generated parametric sideband wavelengths from the experiment with calculations from phase-matching conditions for intermodal four-wave mixing

Q-switching near-infrared multiwavelength generation by intracavity tungsten-oxide-induced four-wave mixing in an erbium-doped fiber laser.

Abstract: We report on the generation of a stable multiwavelength Q-switched erbium-doped fiber laser based on tungsten oxide nanoparticles (WO3 NPs) combined with an intracavity comb filter for the first time, to the best of our knowledge. The prepared WO3-PVA thin film has a modulation depth and saturable intensity of 20% and 100 MW/cm2, respectively. A spectrum of up to 15 peaks with a channel spacing of 0.48 nm has been obtained. In the Q-switching regime, a minimum pulse width of 4.24 μs and a maximum repetition rate of 52.49 kHz were achieved at a maximum pump power of 300 mW. The dual effect of WO3 NPs in saturable absorption and high optical nonlinearity has induced pulsed and four-wave mixing effects. Therefore, the intrinsic advantages of WO3 nanomaterial provide a promising source for the realization of a stable multiwavelength fiber laser.

Spatially dependent four-wave mixing in semiconductor quantum wells

Abstract: We propose a scheme to generate spatially dependent four-wave mixing (FWM) in an asymmetric semiconductor three-coupled-quantum-well nanostructure. By adjusting the detuning of the control field, one can effectively manipulate the FWM output field. Specifically, the vortex phase of the FWM field can be modulated. The detailed explanations based on the dispersion relation are given, which are in good agreement with our results. Furthermore, we perform the interference between the FWM field and the same-frequency Gaussian beam. Our results show that the interference patterns can also be modulated via the detuning of the control field, which may provide a way to observe helical phase modulation via the intensity measurement. This work may be useful for investigating the nonlinear optical phenomena based on orbital angular momentum light.

Ultraslow vortex four-wave mixing via multiphoton quantum interference

Abstract: Orbital angular momentum (OAM) light is nowadays an intriguing resource in classical and quantum optics due to the richness of physical properties it shows in interaction with matter. A key ingredient needed to exploit the full potential of OAM light is the control of quantum interference, a crucial resource in fields like quantum communication and quantum optics. Here, we study the vortex four-wave mixing (FWM) via multi-photon quantum interference in an ultraslow propagation regime. We find that the structured information can be manipulated via two-photon detuning and three photon detuning, which manifests itself as a spatial modulation. The detailed explanations based on the dispersion relation are given, which are in good agreement with our simulations. Furthermore, in order to clearly show the modulated mechanism, we perform the interference between the FWM field and a same-frequency Gaussian beam. It is found that the interference patterns are also manipulated by adjusting the multi-photon detunings. This work may have some potential applications in quantum control based on OAM light.

Enhanced Four-Wave Mixing in Doubly Resonant Si Nanoresonators

Abstract: Frequency conversion is one of the main applications of nonlinear optical processes in which a signal is produced at a different wavelength from the excitation wavelength. In particular, four-wave mixing (FWM) is a third order nonlinear optical process that allows, for instance, the generation of visible frequencies by tuning near-infrared laser pumps. Here, in order to augment the very weak FWM conversion efficiency, we design silicon Mie resonators that exhibit two resonances of the internal electric field intensity around the frequency range of the laser pumps. The linear extinction spectrum of the individual Si resonator is first measured by bright field spectroscopy and compared with numerical simulations to confirm the existence of the two resonances corresponding to electric and magnetic dipole excitations. The FWM signal is then measured for a single Si nanoresonator when the first pump is set to the electric resonance while tuning the frequency of the second pump across the magnetic dipolar resonance. We show that the FWM signal generated in the visible spectrum is maximum when the frequency of the tunable pump corresponds to the maximum of the internal electric field intensity. At this position, the FWM signal is enhanced by more than 2 orders of magnitude compared with the FWM signal generated by the unpatterned silicon film.

Wideband chaos from a laser diode with phase-conjugate feedback.

Abstract: We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase conjugation is obtained from four-wave mixing in a BaTiO3 photorefractive crystal. We demonstrate that the chaos bandwidth first increases linearly with feedback ratio but then saturates to relatively high values. With a single optical feedback, a chaos bandwidth up to about 18 GHz is achieved, which is about five times as large as the free-running laser diode relaxation oscillation frequency. Numerical simulations confirm our experimental observations and unveil that the finite depth penetration into the crystal is responsible for the observed saturation.

Generation of coherent mid-IR light by parametric four-wave mixing in alkali vapor.

Abstract: The parametric four-wave mixing (4WM) process responsible for the generation of coherent blue light in alkali vapors is a self-seeded process which starts by population inversion and amplified spontaneous emission (ASE). Lately, attention has been turned toward frequency up- and down-conversion in alkali vapors, using relatively low pump powers with CW diode lasers. In this Letter, we investigate the interplay between ASE and 4WM in rubidium (Rb) vapors by studying the mid-infrared (mid-IR) radiation emitted in the forward direction at 5.23 μm. We show that the ASE can be suppressed by 4WM in the CW regime. Thus, we demonstrate the generation of coherent mid-IR light at 5.23 μm in hot Rb vapors via parametric 4WM.

Bandwidth enhancement of inter-modal four wave mixing Bragg scattering by means of dispersion engineering

Abstract: Datasets supports Anjum, O. F. et al (2018). Bandwidth enhancement of inter-modal four wave mixing Bragg scattering by means of dispersion engineering. APL Photonics. DOI: 10.1063/1.5048495File descriptions are in 'Data.txt'

A Compact Four-Wave Mixing-Based Temperature Fiber Sensor With Partially Filled Photonic Crystal Fiber

Abstract: In this paper, a compact temperature sensor was constructed based on controllable four-wave mixing (FWM) achieved by a partially filled solid-core photonic crystal fiber (PCF). With the help of a hollow-core fiber, the air holes of the PCF were partially filled with one layer, two layers, and four holes, respectively, thereby realizing a controllable output of signal wave. The response to temperature was tested and analyzed in the experiment. A sensitivity of 0.61 nm/°C was obtained from the room temperature to 150 °C with a fiber shortened to 25.8 mm. Both experimental and theoretical results showed that the response to the temperature could be with great linearity for the one-layer filled PCF, and the sensitivity of FWM-based sensor was almost unchanged when the sensing fiber is shortened, which could be benefit for constructing compact or ultra-compact inline FWM-based sensors. Furthermore, the FWM-based temperature sensor also presented good stability against the fluctuation of the excited power.

Four-wave Mixing of Topological Edge Plasmons in Graphene Metasurfaces.

Abstract: We study topologically-protected four-wave mixing (FWM) interactions in a plasmonic metasurface consisting of a periodic array of nanoholes in a graphene sheet, which exhibits a wide topological bandgap at terahertz frequencies upon the breaking of time-reversal symmetry by a static magnetic field. We demonstrate that due to the significant nonlinearity enhancement and large lifetime of graphene plasmons in specific configurations, a net gain of FWM interaction of plasmonic edge states within the topological bandgap can be achieved with pump power of less than 10 nW. In particular, we find that the effective waveguide nonlinearity coefficient is about 1.1x10^13 1/(Wm), i.e., more than ten orders of magnitude larger than that of commonly used, highly nonlinear silicon photonic nanowires. These findings could pave a new way for developing ultra-low-power-consumption, highly-integrated and robust active photonic systems at deep-subwavelength scale for applications in quantum communications and information processing.

Active engineering of four-wave mixing spectral correlations in multiband hollow-core fibers.

Abstract: We demonstrate theoretically and experimentally a high level of control of the four-wave mixing process in an inert gas–filled inhibited-coupling guiding hollow-core photonic crystal fiber. The specific multiple-branch dispersion profile in such fibers allows both correlated and separable bi-photon states to be produced. By controlling the choice of gas and its pressure and the fiber length, we experimentally generate various joint spectral intensity profiles in a stimulated regime that is transferable to the spontaneous regime. The generated profiles may cover both spectrally separable and correlated bi-photon states and feature frequency tuning over tens of THz, demonstrating a large dynamic control that will be very useful when implemented in the spontaneous regime as a photon pair source.

Characterization and Optimization of Four-Wave-Mixing Wavelength Conversion System

Abstract: In this work, we present a comprehensive experimental and numerical investigation of the impact of system parameters on wavelength converters based on four-wave-mixing, with focus on practical system implementations in addition to the interaction within the nonlinear medium. The input signal power optimization is emphasized according to the trade-off between the linear and the nonlinear impairments, and the origin of the limitations at the optimum is studied. The impact of the input signal quality on the converted idler is discussed, and depending on the dominant noise contribution a varying conversion penalty is demonstrated. The penalty is also shown to scale with increasing number of WDM channels due to additional nonlinear cross-talk between them. Finally, by means of numerical simulations we extend the experimental characterization to high pump powers, showing the impact of parametric noise amplification, and different pump laser linewidths, which lead to increased phase-noise transfer. The experimental characterization employs an integrated AlGaAs-on-insulator waveguide, and the numerical simulations accompany the results to make the analysis general for $\chi ^{(3)}$ materials that satisfy the assumptions of the split-step Fourier method.

Optical angular momentum manipulations in a four-wave mixing process.

Abstract: We investigate the spatial and quantum intensity correlations between the probe and Stokes optical fields produced via four-wave mixing in a double-Λ configuration, when both incoming probe and control fields carry non-zero optical orbital angular momentum (OAM). We observed that the topological charge of the generated Stokes field obeyed the OAM conservation law. However, the maximum values and optimal conditions for the intensity squeezing between the probe and Stokes fields were largely independent of the angular momenta of the beams, even when these two fields had significantly different OAM charges. We also investigated the case of a composite-vortex pump field, containing two closely positioned optical vortices, and showed that the generated Stokes field carried the OAM corresponding to the total topological charge of the pump field, further expanding the range of possible OAM manipulation techniques.

Polarization-based truncated SU(1,1) interferometer based on four-wave mixing in Rb vapor.

Abstract: We propose and demonstrate a polarization-based truncated SU(1,1) interferometer that outputs the desired optical joint-quadrature of a two-mode squeezed vacuum field and allows its measurements using a single balanced homodyne detector. Using such a setup, we demonstrate up to ≈2dB of quantum noise suppression below the shot-noise limit in intensity-difference and phase-sum joint-quadratures, and confirm entanglement between the two quantum fields. Our proposed technique results in a better balance between the two ports of the detector and, consequently, in better common noise suppression for differential measurements. As a result, we are able to observe flat joint-quadrature squeezing and entanglement at a wide range of detection frequencies: from several MHz (limited by the photodiode gain bandwidth) down to a few hundred Hz (limited by electronic noises).

Photon-pair source working in a silicon-based detector wavelength range using tapered micro/nanofibers

Abstract: The development of quantum photonic information technology demands high-quality photon sources. Here we demonstrate a low-noise and high-speed photon source generated by the spontaneous four-wave mixing process in a micro/nanofiber (MNF). The pair generation in a MNF is tailorable by controlling its diameter and designed for creating signal and idler photons in the silicon-based detector wavelength range, yielding high detection efficiency and coincidence count rate. This MNF photon source can be coupled to other fiber systems with negligible coupling loss and can be efficiently exploited as fiber-based quantum light sources for quantum information applications.

Bloch oscillations in photonic spectral lattices through phase-mismatched four-wave mixing.

Abstract: Here we investigate the Bloch oscillations (BOs) in a photonic spectral lattice created with four-wave mixing Bragg scattering (FWM-BS). By injecting a signal and two pumps with different frequencies into a silicon nitride waveguide, a spectral lattice can be created for the generated idlers through successive FWM-BS. The phase-mismatch during FWM-BS acts as an effective force that induces BOs in the spectral lattice. Both the oscillation period and amplitude are determined by the magnitude of the effective force. With cascaded FWM-BS processes, the spectrum of idlers experiences a directional shift as the phase differences of pumps are modulated. Additionally, introducing long-range couplings in the spectral lattice will change the trajectory of BOs within each period. The pattern of BOs for a single frequency input can also be tailored. This Letter provides a new platform to realize BOs in the frequency dimension and paves a promising way for broadband frequency control with all-optical schemes.

Octave-wide phase-matched four-wave mixing in dispersion engineered crystalline microresonators

Abstract: In this Letter, we report phase-matched four-wave mixing separated by over one-octave in a dispersion engineered crystalline microresonator. Experimental and numerical results presented here confirm that primary sidebands were generated with a frequency shift up to 140 THz, and that secondary sidebands formed a localized comb structure, known as a clustered comb in the vicinity of the primary sidebands. A theoretical analysis of the phase-matching condition validated our experimental observations, and our results good agree well with numerical simulations. These results offer the potential to realize a frequency tunable comb cluster generator operating from 1 um to mid-infrared wavelengths with a single and compact device.

Stable L-band multiwavelength erbium-doped fiber laser based on four-wave mixing using nickel nanofluid.

Abstract: A simple continuous-wave multiwavelength erbium-doped fiber laser based on four-wave mixing has been successfully demonstrated utilizing nickel nanofluid (Ni-NF) for the first time, to the best of our knowledge. By fine adjustment of the laser diode pump power up to 196 mW and without any intracavity filtering, stable dual-, triple-, and quadruple-lasing lines in the L-band have been observed at 1595.6 nm, 1596.8 nm, 1598 nm, and 1599.2 nm, respectively, with a signal-to-noise ratio ∼43 dB. The induced L-band wavelengths showed high stability with wavelength shifts <0.07 nm and power fluctuation of <3 dB by monitoring the output spectra for a duration of 30 min at room temperature. Taking into account the superiority of Ni-NF in terms of compactness, low cost, and easy fabrication, this design can be practically used in a variety of nonlinear photonic applications.

Expansion and phase correlation of a wavelength tunable gain-switched optical frequency comb.

Abstract: A novel scheme for the expansion and phase correlation of a wavelength tunable gain-switched optical frequency comb (OFC) is presented. This method entails firstly combining two gain-switched OFCs and expanding them using a phase modulator. Subsequently, the phase correlation between all the comb lines is induced through four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). In this article, the generation of 42 highly correlated comb lines separated by 6.25 GHz, with an optical carrier to noise ratio (OCNR) of more than 50 dB, is experimentally demonstrated. In addition, the wavelength tunability of the scheme, over 30 nm within the C band, is shown. Finally, the degree of phase correlation between comb lines is verified through RF beat tone linewidth measurements. The results show a five orders of magnitude reduction in the beat tone linewidth, due to FWM in an SOA.

Hybrid InGaP nanobeam on silicon photonics for efficient four wave mixing

Abstract: We report the design, fabrication, and characterization of a photonic crystal microresonator exhibiting a constant free spectral range. More than 50 resonances with Q > 2 × 105 are observed in a 200 μm long and 650 nm wide III–V semiconductor cavity heterogeneously integrated on a silicon photonic circuit (Silicon on Insulator). We measured stimulated four wave mixing with a −12 dB signal to idler conversion. Two photon absorption is prevented owing to the wide electronic bandgap of the III–V semiconductor (indium gallium phosphide) enabling the possibility to use sufficiently large optical power densities for efficient nonlinear parametric interactions.

Four Wave Mixing control in a photonic molecule made by silicon microring resonators

Abstract: Four Wave Mixing (FWM) is the main nonlinear interaction in integrated silicon devices, which finds diffuse use in all-optical signal processing and wavelength conversion. Despite the numerous works on coupled resonator devices, which showed record conversion efficiencies and broadband operation, the possibility to coherently control the strength of the stimulated FWM interaction on a chip has received very limited attention. Here, we demonstrate both theoretically and experimentally, the manipulation of FWM in a photonic molecule based on two side coupled silicon microring resonators. The active tuning of the inter-resonator phase and of their eigenfrequencies allows setting the molecule in a sub-radiant state, where FWM is enhanced with respect to the isolated resonators. On the other hand, we can reconfigure the state of the photonic molecule to have energy equipartition among the resonators, and suppress FWM by making the two Signal waves to interfere destructively in the side coupled waveguides. This work constitutes an experimental demonstration of the control of a nonlinear parametric interaction via coherent oscillation phenomena in an integrated optical device.

Noise Filtering for Highly Correlated Photon Pairs From Silicon Waveguides

Abstract: We fabricate silicon waveguide spirals and a ring resonator to generate photon pairs based on a spontaneous four-wave mixing. The coincidence-to-accidental-ratio (CAR) of photon pairs from the silicon waveguides is measured up to 400 after a noise-filtering by using the combination of bandpass filters and pump-rejection filters. The CAR is enhanced up to 700 by adding on-chip pump-rejection MZIs. We observe the CAR of the photon pairs from a silicon spiral is highly depending on the wavelength detuning from the pump wavelength. We discuss the noise sources related to the degradation of the CAR based on our experimental results.

Enhanced four-wave mixing process near the excitonic resonances of bulk MoS 2

Abstract: Two-dimensional materials are generating great interest due to their unique electrical and optical properties. In particular, transition metal dichalcogenides such as molybdenum disulfide (MoS2) are attractive materials due to the existence of a direct band gap in the monolayer limit that can be used to enhance nonlinear optical phenomena, such as Raman spectroscopy. Here, we have investigated four-wave mixing processes in bulk MoS2 using a multiplex coherent anti-Stokes Raman spectroscopy setup. The observed four-wave mixing signal has a resonance at approximately 680 nm, corresponding to the energy of the A excitonic transition of MoS2. This resonance can be attributed to the increased third-order nonlinear susceptibility at wavelengths near the excitonic transition. This phenomenon could open the path to using MoS2 as a substrate for enhancing four-wave mixing processes such as coherent anti-Stokes Raman spectroscopy.