Optical Mode Field Research Articles

Number and phase: complementarity and joint measurement uncertainties

We show that number and canonical phase (of a single mode optical field) are complementary observables. We also bound the measurement uncertainty region for their approximate joint measurements.

Theoretical analysis on nonlinearity of optical fiber with uniaxial crystal material cladding

The effective mode area and nonlinearity of a proposed fiber with cladding made of uniaxial anisotropic crystal material are derived by fully vectorial method, the influence of kcl, the ratio of the extraordinary to the ordinary ray index, on optical field distribution and nonlinear coefficient γ is investigated theoretically. The results indicate that kcl has no impact on optical field distribution and nonlinearity at the wavelength of near 1330nm (crossing point of the curves), but at short wavelength of below 1330nm, the larger kcl is, the more scattering the optical mode field is. However, at the long wavelength, the conclusion is just contrary and kcl has more obvious impact on optical field distribution and nonlinearity than that at short wavelength. Thus the nonlinearity γ can be effectively modified by tailoring kcl at given other parameters of the fibers, and these results provide basis theory for designing optical communication components and optical sensors.

Coherent Atom-Phonon Interaction through Mode Field Coupling in Hybrid Optomechanical Systems.

We propose a novel type of optomechanical coupling which enables a tripartite interaction between a quantum emitter, an optical mode, and a macroscopic mechanical oscillator. The interaction uses a mechanism we term mode field coupling: a mechanical displacement modifies the spatial distribution of the optical mode field, which, in turn, modulates the emitter-photon coupling rate. In properly designed multimode optomechanical systems, we can achieve situations in which mode field coupling is the only possible interaction pathway for the system. This enables, for example, swapping of a single excitation between emitter and phonon, creation of nonclassical states of motion, and mechanical ground-state cooling in the bad-cavity regime. Importantly, the emitter-phonon coupling rate can be enhanced through an optical drive field, allowing active control of the emitter-phonon coupling for realistic experimental parameters.

Modeling the single-mode thermally guiding very-large-mode-area Yb-doped fiber amplifier

The very-large-mode-area (VLMA) fiber is of great importance for suppressing the nonlinear effects which are considered as main limitations to the power scaling-up of high-power fiber lasers and amplifiers. The thermally guiding (TG) VLMA fiber is a novel VLMA fiber, the waveguide of which is formed by the thermal lens effect. Then, a low numerical aperture can be realized, which is promising to achieve the expanding of mode area with a high-quality beam. In order to study the performance of TG VLMA fiber in a fiber amplifier, we present a rate-equation model of the single-mode ytterbium-doped TG VLMA fiber amplifier, which consists of the steady-state rate equations and thermal transferring equations. With this model, the forward-pumped single-mode TG VLMA fiber amplifier is numerically studied. It is found that the diameter of fundamental mode field rises with the increase of the signal power, which shows the superiority of the TG VLMA fiber in suppressing the nonlinear effect in the fiber amplifier. The optimum fiber length and pertinent physical mechanism are also investigated. It is revealed the optimum fiber length is related to the input pump power, and it decreases with the increase of input pump power. However, when the input pump power is large enough, such a variation of optimum fiber length will become weakened. The numerical results also illuminate that the thermal load at the optimum length of TG VLMA fiber should not change too much with the input pump power. Moreover, the mode of output optical field is also discussed. It is found that the thermal load at the optimum length may not be large enough to realize a core-confined mode. In order to ensure that the core-confined mode can be output, the thermal load at the end of the fiber amplifier should be larger. It requires that the fiber length used in the amplifier should be shorter than the optimum fiber length, which will induce the decrease of the output signal power to some extent. In spite of that, the numerical results reveal that the decrease of output signal power should not be much, and the pertinent slope efficiency is not obviously lowered, either. Thus, it is verified that the core-confined mode with a VLMA can be obtained from the TG VLMA fiber amplifier with high slope efficiency. The pertinent results have significant guidance in the design of TG VLMA fiber amplifier.

Data information transfer using complex optical fields: a review and perspective (Invited Paper)

Tailored complex optical fields, may find applications in optical manipulation, imaging, microscopy, quantum information processing, and optical communications. Here, we focus on data information transfer for optical communications using complex optical fields. We review recent research progress in complex optical field modulation, multiplexing, and multicasting for data information transfer on different platforms of waveguides, free space, and fiber. Challenges and perspectives are also discussed.

Entanglement of two hybrid optomechanical cavities composed of BEC atoms under Bell detection

In this paper, firstly, we consider bipartite entanglement between each part of an optomechanical cavity composed of one dimensional Bose-Einstein condensate (BEC). we investigate atomic collision on the behavior of the BEC in the week photon-atom coupling constant, and use Bogoliubov approximation for the BEC. Secondly under above condition, we propose a scheme for entanglement swapping protocol wich involves tripartite systems. In our investigation, we consider a scenario where BECs, moving mirrors, and optical cavity modes are given in a Gaussian state with a covariance matrix (CM). By applying the Bell measurment to the output optical field modes, we show how the remote entanglement between two BECs, two moving mirrors, and BEC-mirror modes in different optomechanical cavity can be generated.

Substrate surface patterning by optical near field modulation around colloidal particles immersed in a liquid.

Optical near field enhancements in the vicinity of particles illuminated by laser light are increasingly recognized as a powerful tool for nanopatterning applications, but achieving sub-wavelength details from the near-field distribution remains a challenge. Here we present a quantitative analysis of the spatial modulation of the near optical fields generated using single 8 ps, 355 nm (and 532 nm) laser pulses around individual colloidal particles and small close packed arrays of such particles on silicon substrates. The analysis is presented for particles in air and, for the first time, when immersed in a range of liquid media. Immersion in a liquid allows detailed exploration of the effects on the near field of changing not just the magnitude but also the sign of the refractive index difference between the particle and the host medium. The level of agreement between the results of ray tracing and Mie scattering simulations, and the experimentally observed patterns on solid surfaces, should encourage further modelling, predictions and demonstrations of the rich palette of sub-wavelength surface profiles that can be achieved using colloidal particles immersed in liquids.

Low Loss Fiber-to-Waveguide Converter With a 3-D Functional Taper for Silicon Photonics

We demonstrate a low-loss and broad-bandwidth fiber-to-waveguide converter with a 3-D functional SiO2 taper for silicon photonics. The converter is composed of a cantilevered SiO2 waveguide and Si nano-tapers. In order to reduce the loss from the cleaved fiber, a 3-D functional SiO2 taper is designed to compress the size of optical mode field. Using cleaved optical fibers with a mode field diameter of 10.5 $\mu \text{m}$ at 1550 nm, we characterized the optical performances of the converter. With an index-matching liquid, the lowest coupling loss of TE mode is 1.5 dB/facet and the lowest coupling loss of TM mode is 2.1 dB/facet. For both TE and TM modes, the 1-dB bandwidth is more than 100 nm, and the alignment tolerances for 1-dB excess loss are, respectively, ±2.5 and $\pm 2~\mu \text{m}$ in horizontal and vertical directions.

Tunable double resonance of silver nanodecahedron on the insulator/conductor film.

The generation of double resonance in a nanostructure, thus permitting the modulation of optical field at two frequencies simultaneously, offers new application opportunities for surface enhanced Raman scattering (SERS) and surface enhanced fluorescence (SEF). Here, we present a simple composite nanostructure of silver nanodecahedron (Ag ND)/silica spacer/gold film/glass substrate for achieving double resonance under the normal incidence of polarized light. The optical responses of the composite structure have been theoretically studied by varying the thickness of silica spacer layer from 5 nm to 35 nm for mediating the interaction between Ag ND and gold film. Results indicate that the extinction spectrum of the composite system is strongly dependent on the separation between Ag ND and gold film. The electric field and charge distribution during resonance have been investigated in order to obtain a detailed understanding on the coupling between these two objects. More importantly, due to the anisotropic geometry of Ag ND, double resonance with two plasmonic modes (dipole and gap modes) whose responses can be adjusted through varying the size of Ag ND and mediating its coupling with the gold film respectively, has been achieved in the composite structure under the excitation with polarization parallel to the Ag ND edge adjacent to the spacer surface. The knowledge gained through this work will benefit the development of applications based on local field enhancement.

Spin-exchange relaxation-free magnetometer with nearly parallel pump and probe beams

We constructed a spin-exchange relaxation-free (SERF) magnetometer with a small angle between the pump and probe beams facilitating a multi-channel design with a flat pancake cell. This configuration provides almost complete overlap of the beams in the cell, and prevents the pump beam from entering the probe detection channel. By coupling the lasers in multi-mode fibers, without an optical isolator or field modulation, we demonstrate a sensitivity of 10 f T for frequencies between 10 Hz and 100 Hz. In addition to the experimental study of sensitivity, we present a theoretical analysis of SERF magnetometer response to magnetic fields for small-angle and parallel-beam configurations, and show that at optimal DC offset fields the magnetometer response is comparable to that in the orthogonal-beam configuration. Based on the analysis, we also derive fundamental and probe-limited sensitivities for the arbitrary non-orthogonal geometry. The expected practical and fundamental sensitivities are of the same order as those in the orthogonal geometry. We anticipate that our design will be useful for magnetoencephalography (MEG) and magnetocardiography (MCG) applications.

Controlled Electromagnetically Induced Transparency and Fano Resonances in Hybrid BEC-Optomechanics.

Cavity-optomechanics, a tool to manipulate mechanical effects of light to couple optical field with other physical objects, is the subject of increasing investigations, especially with regards to electromagnetically induced transparency (EIT). EIT, a result of Fano interference among different atomic transition levels, has acquired a significant importance in many areas of physics, such as atomic physics and quantum optics. However, controllability of such multi-dimensional systems has remained a crucial issue. In this report, we investigate the controllability of EIT and Fano resonances in hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC), trapped inside high-finesse Fabry-Pérot cavity with one vibrational mirror, driven by a single mode optical field and a transverse pump field. The transverse field is used to control the phenomenon of EIT. It is detected that the strength of transverse field is not only efficiently amplifying or attenuating out-going optical mode but also providing an opportunity to enhance the strength of Fano-interactions which leads to the amplification of EIT-window. To observe these phenomena in laboratory, we suggest a certain set of experimental parameters. The results provide a route for tunable manipulation of optical phenomena, like EIT, which could be a significant step in quantum engineering.

基于空间光场调控技术的光学微操纵

基于空间光场调控技术的光学微操纵

硅基半导体多场耦合下的光传输及电调控特性分析

In order to study the silicon based semiconductor's electro-optic-thermal muti-field coupling characteristics and electric modulation problems,both the Poisson equation and the carrier continuity equation were introduced to calculate the carrier concentration distribution in the carrier transport procession. Drude Lorentz relation and K-K relation were also employed to discuss the effect of the carrier concentration on the refractive index and absorption coefficient. The heat deposited items were obtained by calculating electromagnetic dissipation. The coupled semiconductor basic equation,electromagnetic wave equation and energy equation were solved by using finite element method. With the effect of external voltage,initial concentration of carrier and heat transfer coefficient,the change of dielectric properties,optical transmission behavior of silicon based semiconductor were also analyzed by coupling solution and analysis. The results show that the reflective optical field mode of the semiconductor P area increases with the increasing of the applied voltage,and decreases with the increasing of the heat transfer coefficient. Using this mechanism,a scheme of electric thermal modulation for the space distribution of the reflection intensity was presented.

Temperature Effect of Measuring One of the Two Modes of a New Two-Mode Optical Field

We propose a new two-mode optical field which involves both squeezing and chaotic behaviour. We find that measuring one of the two modes of this new two-mode optical field (theoretically it is performed by partial tracing over one of the two modes of this optical field’s density operator) leads to different chaotic field with different temperature. This means that a different-mode measurement for the new optical field will cause a temperature effect which has been unnoticed before. Such kind of new photon field can be generated when a two-mode squeezed state is passing through a single-mode damping channel.

Generation of vectorial optical fields with slot-antenna-based metasurface.

A transmission-type metasurface composed of carefully designed rectangular slot antennas for the generation of vectorial optical fields is proposed and demonstrated. Acting as local linear polarizers, these slot antennas enable the spatial modulation of optical fields in amplitude, phase, and polarization for the cross-polarized component of the scattered field. As an illustration, a metasurface capable of forming a radially polarized scattered field with specific vectorial beam patterns with appropriate excitation at normal incidence is designed, fabricated, and tested. The radially polarized scattered field is designed to be further tightly focused by a high numerical aperture objective lens in order to obtain a uniform longitudinally polarized optical needle field along the propagation direction. Characterization experiments demonstrate that its overall extinction ratio satisfies the amplitude modulation requirement, and a corresponding π phase modulation is realized as proposed.

Theoretical and Numerical Study of the Threshold of Stimulated Brillouin Scattering in Multimode fibers

In this paper, we have studied theoretically and numerically the thresholds of stimulated Brillouin scattering in multimode fibers. With both the coupling among all optical modes and the effect of optical and acoustic mode field profiles on the Brillouin gain spectrums considered for the first time, we propose the corresponding transcendental equations for the Brillouin thresholds of continuous-wave signal under different conditions. Based on the theoretical results, it is concluded that Brillouin threshold in multimode fiber is determined by the constitution of the transverse modes in the signal. Moreover, the theoretical predictions are compared with the results obtained by numerically integrating the signal-Stokes power equations, and good agreements are achieved between them.

Tunable bistability in hybrid Bose-Einstein condensate optomechanics.

Cavity-optomechanics, a rapidly developing area of research, has made a remarkable progress. A stunning manifestation of optomechanical phenomena is in exploiting the mechanical effects of light to couple the optical degree of freedom with mechanical degree of freedom. In this report, we investigate the controlled bistable dynamics of such hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC) trapped inside high-finesse optical cavity with one moving-end mirror and is driven by a single mode optical field. The numerical results provide evidence for controlled optical bistability in optomechanics using transverse optical field which directly interacts with atoms causing the coupling of transverse field with momentum side modes, exited by intra-cavity field. This technique of transverse field coupling is also used to control bistable dynamics of both moving-end mirror and BEC. The report provides an understanding of temporal dynamics of moving-end mirror and BEC with respect to transverse field. Moreover, dependence of effective potential of the system on transverse field has also been discussed. To observe this phenomena in laboratory, we have suggested a certain set of experimental parameters. These findings provide a platform to investigate the tunable behavior of novel phenomenon like electromagnetically induced transparency and entanglement in hybrid systems.

Characterization of conditional state-engineering quantum processes by coherent state quantum process tomography

Conditional quantum optical processes enable a wide range of technologies from generation of highly non-classical states to implementation of quantum logic operations. The process fidelity that can be achieved in a realistic implementation depends on a number of system parameters. Here we experimentally examine Fock state filtration, a canonical example of a broad class of conditional quantum operations acting on a single optical field mode. This operation is based upon interference of the mode to be manipulated with an auxiliary single-photon state at a beam splitter, resulting in the entanglement of the two output modes. A conditional projective measurement onto a single photon state at one output mode heralds the success of the process. This operation, which implements a measurement-induced nonlinearity, is capable of suppressing particular photon-number probability amplitudes of an arbitrary quantum state. We employ coherent-state process tomography to determine the precise operation realized in our experiment, which is mathematically represented by a process tensor. To identify the key sources of experimental imperfection, we develop a realistic model of the process and identify three main contributions that significantly hamper its efficacy. The experimentally reconstructed process tensor is compared with the model, yielding a fidelity better than 0.95. This enables us to identify three key challenges to overcome in realizing a filter with optimal performance—namely the single-photon nature of the auxiliary state, high mode overlap of the optical fields involved, and the need for photon-number-resolving detection when heralding. The results show that the filter does indeed exhibit a non-linear response as a function of input photon number and preserves the phase relation between Fock layers of the output state, providing promise for future applications.

Experimental Demonstration of Reduced Light Absorption by Intracavity Metallic Layers in Tamm Plasmon-based Microcavity

We demonstrate experimentally a microcavity based on SiO2/TiO2 with two gold layers directly attached to the central base of the microcavity. The design of optical modes based on the peculiarities of Tamm plasmons provides reduced absorption due to the fixing of the node of the electric field of optical mode to metallic layers. Experimentally measured reflection and transmission spectra exhibits three features, corresponding to three hybrid modes of the microcavity. The widths of spectral features confirm that absorption of light by metallic layers is vanishing for optimized mode. The latter is confirmed by resonant transmission of light through the structure. In case of the laser structure, two intracavity metallic layers could serve as contacts for electrical pumping.

聚合物填充的狭缝波导定向耦合器的数值分析

In terms of Helmholtz equation and finite-difference time-domain method,a numerical approach for analyzing the directional coupling characteristics based on two SU-8filled slot waveguides was proposed.The mode eigen equation of the coupling slot waveguides was derived and solved,and mode optical field distribution and effective refractive index were achieved.By using the effective refractive indices of the highest-order even symmetric mode and the highest-order odd symmetric modes,the coupling length under TE and TM polarizations was calculated.Numerical simulation results show that when the coupling gap is less than 800nm,the coupling length is less than 100μm.The wavelength dispersion characteristics of the used materials were measured with an ellipsoidmeter,and then the wavelength dispersion of coupling length and mode loss of the coupling slot waveguides were investigated.The analytical results reveal that the coupling length decreases as the wavelength increases under both polarizations,and under the same coupling gap,the coupling length under TM polarization is larger than that under TE polarization.The coupling lengths under TM and TE polarizations are 28.2and 26.2μm,respectively,when wavelength is 1 550nm and coupling gap is 0.5μm.In addition,the mode loss also decreases as wavelength increases,and the mode loss under TE polarization is larger than that under TM polarization.The loss coefficients under TE and TM polarizations are 5.65 and 3.16 dB/cm,respectively,when the wavelength is 1 550 nm.