Effectively modulating spatial vortex four-wave mixing in a diamond atomic system

Due to the spatial characteristics of orbital angular momentum,vortex fields can be applied in the fields of quantum storage and quantum information.We study the realization of spatially modulated vortex fields based on four-wave mixing in a four-level atomic system with a diamond structure.The intensity and spiral phase of the vortex field are effectively transferred to the generated four-wave mixing field.By changing the detuning of the probe field,the phase and intensity of the generated vertex four-wave mixing field can be changed.When the probe field takes a large detuning value,the spatial distribution of the intensity and phase of the vertex four-wave mixing field can be effectively tuned by adjusting the Rabi frequency or detuning value of the coupled field.At the same time,we also provide a detailed explanation based on the dispersion relationship,and the results agree well with our simulation results.

Influence of Waveguide Properties on Wave Prototypes Likely to Accompany the Dynamics of Four-Wave Mixing in Optical Fibers

In this article, we study the impacts of nonlinearity and dispersion on signals likely to propagate in the context of the dynamics of four-wave mixing. Thus, we use an indirect resolution technique based on the use of the iB-function to first decouple the nonlinear partial differential equations that govern the propagation dynamics in this case, and subsequently solve them to propose some prototype solutions. These analytical solutions have been obtained;we check the impact of nonlinearity and dispersion. The interest of this work lies not only in the resolution of the partial differential equations that govern the dynamics of wave propagation in this case since these equations not at all easy to integrate analytically and their analytical solutions are very rare, in other words, we propose analytically the solutions of the nonlinear coupled partial differential equations which govern the dynamics of four-wave mixing in optical fibers. Beyond the physical interest of this work, there is also an appreciable mathematical interest.

Wavelength dependence four-wave mixing spectroscopy in a micrometric atomic vapour

This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke- narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.

Influence of degenerate four-wave mixing on the performance of supercontinuum-based multiwavelength optical source

The influence of degenerate four-wave mixing （FWM） on the performance of supercontinuum-based multiwavelength optical source has been investigated in detail experimentally and theoretically. Numerical simulation results show that the degenerate FWM effect has a deteriorative influence on the spectral uniformity and the optical signal-to-noise ratio （OSNR） of supercontinuum-based optical source, and by suppressing degenerate FWM effect the performance enhancement of the supercontinuum can be achieved successfully. These results are also confirmed by our experiments. Experimentally, by suppressing degenerate FWM the crosstalk of adjacent channels to the filtered channel can be reduced by as much as 15 dB, and consequently the measured receiver sensitivity at 10 Gbit/s for the filtered optical source is improved from -1.7 to -17.8 dBm.

Phase-matching analysis of four-wave mixing induced by modulation instability in a single-mode fiber

Four-wave mixing induced by modulation instability in a single-mode fiber is analyzed from the phase-matching point of view. For the two-channel transmission, a method is proposed to select the four-wave-mixing-induced sidebands, which is based on the proper use of a continuous-wave and a pulse as light sources. We find that a mass of sidebands are generated in the modulation instability resonance region, and the power of the sideband increases with not only the peak power of the pump pulse but also the continuous-wave power which acts as a seed. The research will provide guidance for fiber communication and sensing systems using wavelength division multiplexing technology.

Characterize and optimize the four-wave mixing in dual-interferometer coupled silicon microrings

By designing and fabricating a series of dual-interferometer coupled silicon microrings, the coupling condition of the pump, signal, and idler beams can be engineered independently and then we carried out both the continuous-wave and pulse pumped four-wave mixing experiments to verify the dependence of conversion efficiency on the coupling conditions of the four interacting beams, respectively. Under the continuous-wave pump, the four-wave mixing efficiency gets maximized when both the pump and signal/idler beams are closely operated at the critical coupling point, while for the pulse pump case, the efficiency can be enhanced greatly when the pump and converted idler beams are all overcoupled. These experiment results agree well with our theoretical calculations. Our design provides a platform for explicitly characterizing the four-wave mixing under different pumping conditions, and offers a method to optimize the four-wave mixing, which will facilitate the development of on-chip all-optical signal processing with a higher efficiency or reduced pump power.

Analysis of Radio over Fiber system for mitigating four-wave mixing effect

In this paper,an efficient 8-channel 32Gbps RoF(Radio over Fiber)system incorporating Bessel Filter(8/32 RoFBF)has been demonstrated to reduce the impact of non-linear transmission effects,specifically Four-Wave Mixing(FWM).The simulation results indicate that the proposed 8/32 RoF-BF system provides an optimum result w.r.t.channel spacing(75 GHz),input source power(0 dBm)and number of input channels(8).In comparison with the existing RoF system,the proposed 8/32 RoF-BF system has been validated analytically and it is found that the performance of the proposed system is in close proximity particularly in FWM sideband power reduction of the order of 4 dBm for the 8-channel 32Gbps RoF system.

Dynamic and inner-dressing control of four-wave mixing in periodically-driven atomic system

Four-wave-mixing(FWM) process is examined by using density matrix formalism in a periodically-driven atomic medium. Numerical result shows that FWM signals can be controlled by selecting different dynamic parameters of the probe field and strengths of the inner-dressing fields. It is also shown that the controllable FWM process is dominantly influenced by the evolution of atomic population difference and two-photon coherence. This dynamic and inner-dressing control of FWM is probably used for optimizing the optical nonlinear process and information processing.

Photon statistics of pulse-pumped four-wave mixing in fiber with weak signal injection

We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal（idler） field g_（s（i））^（2） decreases with the intensity of signal injection. After applying narrow band filter in signal（idler） band, the value of g_（s（i））^（2） decreases from 1.9 ± 0.02（1.9 ± 0.02） to 1.03 ± 0.02（1.05 ± 0.02） when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose–Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results.Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network.

Electro-optomechanical switch via tunable bistability and four-wave mixing

We investigate the tunable bistable behavior of a hybrid nano-electro-optomechanical system(NEOMS) composed of S-shaped in the presence of two-level atoms, trapped inside a Fabry–Pérot cavity, and driven by a strong driving field and a weak probe field. The bistable behavior of the steady-state photon number and the mechanical steady-state positions are discussed. Further, we tune bistability by tuning all the coupling frequencies involved in the system and amplitude of the driving field. The present study provides the possibility of realization of a controllable optical switch depending on atom-field coupling, optomechanical coupling, electrostatic Coulomb coupling, and threshold power. In addition, we discuss that the non-linear effect of the hybrid NEOMS generates the four-wave mixing(FWM) process. Moreover, we show that the FWM process can be suppressed by the atom-field detuning and cavity-field detuning, which exhibits low photon transmission.

Online Inter-Modal Dispersion Monitoring Based on Four-Wave Mixing

A novel online Differential Mode Group Delay(DMGD)monitoring method based on four-wave mixing(FWM) in few mode fiber(FMF) transmission system is proposed, and the DMGD monitoring is achieved on the whole range of 15-50 ps/km. Detection principle is deduced and relationship of the power of idler waves and DMGD is analyzed. With various chromatic dispersion(CD)values, different line widths and different optical signal noise ratio(OSNR) values, the simulations are carried out. The simulation results show that this new DMGD monitoring method is less affected by different line widths and has a high tolerance for OSNR.

Phase dispersion of Raman and Rayleigh-enhanced four-wave mixings in femtosecond polarization beats

Based on color-locking noisy field correlation in three Markovian stochastic models, phase dispersions of the Raman- and Rayleigh-enhanced four-wave mixing （FWM） have been investigated. The phase dispersions are modified by both linewidth and time delay for negative time delay, but only by linewidth for positive time delay. Moreover, the results under narrowband condition are close to the nonmodified nonlinear dispersion and absorption of the material. Homodyne and heterodyne detections of the Raman, the Rayleigh and the mixing femtosecond difference-frequency polarization beats have also been investigated, separately.

Controllable optical mirror of cesium atoms with four-wave mixing

The controllable optical mirror is experimentally accomplished in a A-type three-level atomic system coupled with standing wave. It is shown that the reflection of probe light results from electromagnetically-induced-transparency-based four-wave mixing, therefore the reflection efficiency is highly dependent on the angle for phase matching condition between the probe and coupling fields. The measured reflection spectra show good agreement with dispersion compensation theory.

Characterization of the pairwise correlations in different quantum networks consisting of four-wave mixers and beamsplitters

We investigate the performances of the pairwise correlations（PCs） in different quantum networks consisting of fourwave mixers（FWMs） and beamsplitters（BSs）. PCs with quantum correlation in different quantum networks can be verified by calculating the degree of relative intensity squeezing for any pair of all the output fields. More interestingly, the quantum correlation recovery and enhancement are present in the FWM＋BS network and the repulsion effect phenomena（signal（idler）-frequency mode cannot be quantum correlated with the other two idler（signal）-frequency modes simultaneously）between the PCs with quantum correlation are predicted in the FWM ＋ FWM and FWM ＋ FWM ＋ FWM networks. Our results presented here pave the way for the manipulation of the quantum correlation in quantum networks.

Measurement of the carrier recovery time in SOA based on four-wave mixing on narrow-band ASE spectrum

Carrier recovery time is a key parameter that determines the performance of a semiconductor optical amplifier （SOA）. A measurement method of carrier recovery time in SOA based on a nearly degenerate four-wave mixing of narrowband amplified spontaneous emission （ASE） spectra is presented. The results show the carrier times are 50.2, 44.6, and 23.6 ps when the injected currents are 120, 180, and 240 mA, respectively, which are in agreement with the nominal values of the sample.

Enhancement and suppression of spatial splitting four-wave mixing in atomic medium

We experimentally report on the evolution from singly-dressed to doubly-dressed four-wave mixing （FWM） process by controlling the powers of the probe, the pump and the dressing fields respectively. The differences in the enhancement and the suppression of FWM signal between the two-level and cascade three-level atomic systems are observed and explained by the multi-dressed effect theoretically. Both the x direction and the y direction spatial splittings of the degenerate-FWM （DWFM） beams are obtained. We also investigate the switch between the enhancement and the suppression of the DWFM signals and between its spatial splittings in x direction and y direction. The spatial splittings in x direction and y direction can be controlled by the relative position and the intensity of the involved laser beams. Such a study can be useful for optimizing the efficiency of the FWM process and providing potential applications in spatial signal processing.

Enhancement of multiple four-wave mixing via cascaded fibers with discrete dispersion decreasing

Cascaded fiber geometry with the dispersion of each fiber decreasing is proposed to enhance the multiple four-wave mixing（FWM） generation. The first fiber with relatively large dispersion initiates and accelerates the expansion of multiple FWM, and the second fiber with small dispersion would allow the phase-matching process（thus the spectrum broadening）to keep going. Numerical and experimental results show that with this geometry not only multiple FWM expansion can be accelerated, but also the efficiency of multiple FWM products can be effectively improved with shorter fibers.

Coherent 420 nm laser beam generated by four-wave mixing in Rb vapor with a single continuous-wave laser

We demonstrate the generation of the coherent 420 nm laser via parametric four-wave mixing process in Rb vapor.A single 778 nm laser with circular polarization is directly injected into a high-density atomic vapor,which drives the atoms from the 5S1/2 state to the 5D5/2 state with monochromatic two-photon transition.The frequency up-conversion laser is generated by the parametric four-wave mixing process under the phase matching condition.This coherent laser is firstly certified by the knife-edge method and a narrow range grating spectrometer.Then the generated laser power is investigated in terms of the power and frequency of the incoming beam as well as the density of the atoms.Finally,a 420 nm coherent laser with power of 19μW and beam quality of Mx^2=1.32,My^2=1.37 is obtained with optimal experimental parameters.This novel laser shows potential prospects in the measurement of material properties,information storage,and underwater optical communication.

Multi-component optical azimuthons of four-wave mixing

We report the multi-component optical azimuthons of four-wave mixing （FWM） composed of several modulated vortex beams, the so-called azimuthons, in V-type three-level and two-level atomic systems. We analyze the formation mechanisms of the FWM azimuthons theoretically and experimentally. In addition, we illustrate the interactions between the co-propagating azimuthon components. Finally, we also compare the stabilities of azimuthons in V-type three-level and two-level atomic systems.

Enhancement of four-wave mixing process in a four-level double semiconductor quantum well

The time-dependent four-wave mixing（FWM） is analyzed in a four-level double semiconductor quantum well. The results show that both the amplitude and the conversion efficiency of the FWM field are enhanced with increasing the strength of two-photon Rabi frequency. Interestingly, when the one-photon detuning becomes stronger the control field corresponding to the maximum efficiency increases. Such a controlled enhanced FWM may be used to generate coherent short-wave length radiation, and it can have potential applications in quantum control and communications.