Orthogonal Polarization Components Research Articles

Single chip simultaneous chiral and achiral imaging based on high efficiency 3D plasmonic metalens

Abstract We propose and experimentally demonstrate a single chip metasurface for simultaneous chiral and achiral imaging and polarimetric detecting using a high efficiency three dimensional plasmonic metalens (3D-PM) with capability of designed separation of different circular polarizations. The proposed 3D-PM combines both propagating and geometric phases so that two orthogonal circular polarization components of the incidence can be precisely separated and imaged into two channels and the incident polarization state can be detected with differentiation of the two channels. One single set of an array of Au layer covered anisotropic polymethyl methacrylate elliptical nanopillars is employed, in which height of each nanopillar is added as a new design degree of freedom to realize both full phase manipulation (0–2π) and high efficiency (>0.85) with coupled equivalent Fabry–Pérot cavity and localized surface plasmons. At design wavelength of 1550 nm, experimental results show that optical resolution of both chiral and achiral images approaches the diffraction limit, extinction ratio of circular polarizations in two channels is ∼33:1, and the energy efficiency reaches ∼63 %. The proposed 3D-PM provides a new and simple way for chiral/achiral imaging and polarimetric measurement, and can be applied in integrated optics, optical communication, and biomolecule detection.

Generation of a vector conventional soliton via a graphene oxide saturable absorber.

We have experimentally observed an ultrashort conventional vector soliton in an erbium-doped fiber laser. The few-layered graphene oxide (GO) is used as a saturable absorber (SA). It is found that the saturable absorption characteristic of GO is polarization independent. Therefore, vector solitons can be obtained without polarization control by using such SA. By using a polarization beam splitter to split the mode-locked pulse obtained in the oscillator, two orthogonal polarization vector solitons with equal intensity and consistent characteristics can be obtained. It demonstrates that the initial soliton consists of two orthogonal polarization components. It is worth noting that these two orthogonal polarization component solitons improve the signal-to-noise ratio (SNR) of 3dB compared with the initial soliton. The improvement in SNR is very significant and cannot be neglected. This phenomenon has not been reported before, to our knowledge. In addition, the conventional soliton generated by this mode-locked laser has a central wavelength of 1559nm with 1.1ps pulse duration. The mode-locking state of this laser can be self-started. After mode locking, the environmental stability is excellent. The experimental results indicate that GO as a broadband SA has great potential and application prospects in the field of vector soliton generation.

Linear polarization-separating metalens at long-wavelength infrared.

We designed and fabricated a linear polarization-separation metalens (PSM) made of single-crystal silicon (sc-Si) for long-wavelength infrared (LWIR) imaging. The PSM comprises sc-Si dielectric waveguide pillar meta-atoms with rectangular cross-sections, providing a full 2π phase delay range for two orthogonal linear polarization components with high transmittances (>70%). Electron beam lithography and deep reactive ion etching were used to fabricate the PSM. Polarization-separation imaging of elevated and ambient temperature objects was demonstrated with high extinction ratios of 21.8 dB and 12.8 dB for the x- and y-polarizations, respectively. Additionally, polarization-sensitive imaging was demonstrated by distinguishing the surfaces of a hand and toy windows. Our work enables the visualization of invisible information in the LWIR region and has widespread applications.

Implementation of a Quantum Memory Protocol Based on the Revival of Silenced Echo in Orthogonal Geometry at the Telecommunication Wavelength

An optical quantum memory protocol has been implemented on the basis of the revival of silenced echo at the telecommunication wavelength for signal light fields with a small number of photons. To this end, a long-lived (>1 s) absorption line has been initialized and the orthogonal geometry of the propagation of the signal and rephasing fields has been chosen. An efficiency of revival of (17 ± 1)% has been reached for the orthogonal polarization components of a signal pulse at a storage time of 60 μs. The input pulse contains ~38 photons on average, the revived echo signal includes ~6 photons, and the signal-to-noise ratio is 1.3.

Wideband ultra-low intensity noise reduction via joint action of gain saturation and out-of-phase polarization mixing effect from a semiconductor optical amplifier.

In this article, the vector dynamics of semiconductor optical amplifiers (SOAs) are systematically analyzed and developed to explore its mechanism of intensity noise suppression. First, theoretical investigation on the gain saturation effect and carrier dynamics is performed via a vectorial model, and the calculated result unravels desynchronized intensity fluctuations of two orthogonal polarization states. Particularly, it predicts an out-of-phase case, which allows the cancellation of the fluctuations via adding up the orthogonally-polarized components, then establishes a synthetic optical field with stable amplitude and dynamic polarization, and thereby enables a remarkable relative intensity noise (RIN) reduction. Here, we term this approach of RIN suppression as out-of-phase polarization mixing (OPM). To validate the OPM mechanism, we conduct an SOA-mediated noise-suppression experiment based on a reliable single-frequency fiber laser (SFFL) with the presence of relaxation oscillation peak, and subsequently carry out a polarization resolvable measurement. By this means, out-of-phase intensity oscillations with respect to the orthogonal polarization states are clearly demonstrated, and consequently enable a maximum suppression amplitude of >75 dB. Notably, the RIN of 1550-nm SFFL, suppressed by joint action of OPM and gain saturation effect, is dramatically reduced to -160 dB/Hz in a wideband of 0.5 MHz∼10 GHz, and the performance of which is excellent by comparing with the corresponding shot noise limit of -161.9 dB/Hz. The proposal of OPM here not only facilitates us to dissect the vector dynamics of SOA but also offers a promising solution to realize wideband near-shot-noise-limited SFFL.

Highly Birefringent and Low-Loss Hollow-Core Anti-Resonant Fiber Based on a Hybrid Guidance Mechanism

A highly birefringent and low-loss hollow-core anti-resonant fiber (HC-ARF) based on a hybrid guidance mechanism is proposed and investigated by using a finite element method. The hybrid guidance mechanism is caused by the anti-resonance effect and the total internal reflection effect. The proposed HC-ARF is obtained by employing twin symmetrical and mutually tangential elliptical arc anti-resonance layers (EA-ARLs) in a conventional 8-tube HC-ARF. Because of the anti-resonance mechanism and the total internal reflection mechanism in the EA-ARL, mode coupling appears between the core mode and the cladding mode. Simulation results indicate that the proposed HC-ARF can achieve birefringence as high as 10−2 in a near-infrared range of 1400 nm to 1600 nm and a low confinement loss (CL) of 7.74 × 10−4 dB/m (9.26 × 10−4 dB/m) for x- and y-polarization components of the fundamental mode (FM) at 1550 nm. In addition, the existence of the 8-tube anti-resonance structure in the cladding significantly suppresses the CL of the x-polarization component of the FM significantly, but the impact on the CL of the y-polarization FM can be ignored, which is determined mainly by the twin EA-ARLs. Furthermore, the performance of the birefringence and CL are also investigated by changing the values of other fiber structure parameters. Our proposed structure successfully shows the ability of the hybrid guidance mechanism in the application of CL manipulation of orthogonal polarization components.

Optical Anisotropy of Nanoporous Alumina Films as the Basis for Creation of Achromatic Phase Plates with a Variable Phase Difference of the Orthogonal Polarized Components of Transmitted Radiation

Optical Anisotropy of Nanoporous Alumina Films as the Basis for Creation of Achromatic Phase Plates with a Variable Phase Difference of the Orthogonal Polarized Components of Transmitted Radiation

Broadband Linear to Circular Polarizer Based on Multilayer Frequency-Selective Surface

In this work, a transmission polarizer is described by using a frequency-selective surface to transform linearly polarized waves into circularly polarized waves. The linear to circular (LTC) polarizer consists of four layers. Two types of unit cells are designed in the LTC polarizer to improve design freedom. As a result, two orthogonal polarized components of transmission waves display nearly 90° phase differences while maintaining nearly high transparency for the generation of CPWs. The less than 3 dB axial ratio with a fractional width of over 76.8% from 9.20 to 20.67 GHz for this LTC polarizer is obtained. Even when the incident angle reaches 20°, its operating frequency band covers 9.69 to 20.21 GHz. Compared with the converters proposed before, the one proposed in this paper has a wider bandwidth. In order to evaluate the design strategy, a prototype is manufactured and tested. The results of the simulation and the experiment are in good accord.

First-principle calculation of birefringence effects for in-ice radio detection of neutrinos

The detection of high-energy neutrinos in the EeV range requires new detection techniques to cope with the small expected flux. The radio detection method, utilizing Askaryan emission, can be used to detect these neutrinos in polar ice. The propagation of the radio pulses has to be modeled carefully to reconstruct the energy, direction, and flavor of the neutrino from the detected radio flashes. Here, we study the effect of birefringence in ice, which splits up the radio pulse into two orthogonal polarization components with slightly different propagation speeds. This provides useful signatures to determine the neutrino energy and is potentially important to determine the neutrino direction to degree precision. We calculated the effect of birefringence from first principles where the only free parameter is the dielectric tensor as a function of position. Our code, for the first time, can propagate full RF waveforms, taking interference due to changing polarization eigenvectors during propagation into account. The model is available open-source through the NuRadioMC framework. We compare our results to in-situ calibration data from the ARA and ARIANNA experiments and find good agreement for the available time delay measurements. This indicates a significant improvement of the prediction power of birefringence effects compared to previous models. Finally, the implications and opportunities for neutrino detection are discussed.

Polarization-Dependent Absorption and Transmission Metasurfaces for Linearly and Circularly Polarized Light in Terahertz Band

Polarization detection is an important part of many polarization applications such as polarization imaging, wireless communication, and circular dichroism spectroscopy. In this paper, two polarization-dependent terahertz wave absorption and transmission metasurface for linearly and circularly polarized light are proposed and proved by numerical simulations. Polarization filtering and polarization absorption are integrated on a single cell, and the orthogonal polarization component is transmitted and absorbed, respectively. The linearly polarization-dependent transmission and absorption structure can obtain a transmission extinction ratio of 11.5 dB and an absorption extinction ratio of over 270 dB at 3 THz. Moreover, the circularly polarization-dependent structure can obtain a transmission extinction ratio of 8.1 dB and an absorption extinction ratio of 4.66 dB at 2.8 THz. Our design facilitates the acquisition of full Stokes parameters and the high-resolution imaging.

Polarization and Torsion Insensitive Fiber Bragg Grating Written in Polarization Maintaining ZEBRA Fiber With Artificial Anisotropy

We present first fiber Bragg grating (FBG) inscribed in polarization maintaining (PM) optical fiber with artificially anisotropic core achieved by an appropriate distribution of discrete germanium-doped areas in nanoscale. We proved that this FBG reveals unique properties. Its single-resonance spectral shape, strain and temperature sensitivities are similar to that for grating written in cylindrically symmetrical optical fiber, which indicates that it behaves as the grating fabricated in a non-PM fiber, whereas it is written in the fiber that preserves the orthogonal polarization components of the mode. Moreover, due to the relatively low birefringence of the fiber, the FBG is insensitive to the excited polarization state and twist, and only a negligible shift of the spectrum is noticeable with no changes in its shape. Thus, FBG inscribed in ZEBRA fiber is a kind of hybrid structure that can be used for all-fiber lasers that generate polarized wave, as well as for polarization fiber sensors and components with spectral insensitivity to random or intentional twist.

Mapping partially polarized light to incoherent superpositions of vector beams and vortex beams with orbital angular momentum

Fully polarized light, cylindrical vector beams, and beams with opposite orbital angular momentum (OAM) and their superpositions are respectively represented as points on the Poincaré sphere (PS), the higher-order Poincaré sphere (HOPS) and the OAM Poincaré sphere (OAMPS). Here, we study the mapping of inner points between these spheres, which we regard as incoherent superpositions of points on the surface of their respective sphere. We obtain points inside the HOPS and OAMPS by mapping incoherent superpositions of points on the PS, i.e., partially polarized states. To map points from the PS to the HOPS, we use a q-plate, while for mapping points from the HOPS to the OAMPS, we use a linear polarizer. Furthermore, we demonstrate a new polarization state generator (PSG) that generates efficiently partially polarized light. It uses a geometric phase (GP) blazed grating to split an unpolarized laser into two orthogonal polarization components. An intensity filter adjusts the relative intensity of the components, which are then recombined with another GP grating and directed to a waveplate, thus achieving every point inside the PS. The proposed PSG offers advantages over other methods in terms of energy efficiency, ease of alignment, and not requiring spatial or long-time integrations.

Single shot and speckle free reconstruction of orthogonal polarization modes with a tuneable beam displacer

Imaging through a random scatterer is a challenging problem due to the spatial scrambling of the light wavefront and formation of the speckle pattern. Here, we present a new experimental configuration in holography with a two-point intensity correlation to reconstruct the orthogonal polarization modes from a single shot measurement of the speckle pattern. Speckle free orthogonal polarization modes are reconstructed by applying the ensemble averaging in the correlation analysis. Both orthogonal polarization components of the object are simultaneously reconstructed using an edge point referencing for holography with the coherence waves and with a specially designed tuneable beam displacer. This tuneable beam displacer supports independent recording of the orthogonally polarized speckles at different spatial locations, and hence supports simultaneous reconstruction of the orthogonal polarization components of object from the random light.

Flexible Method for Generating Arbitrary Vector Beams Based on Modified Off-Axis Interference-Type Hologram Encoding

A novel experimental setup for the generation of arbitrary vector beams is proposed. The system major includes two reflective liquid crystal spatial light modulators (RLC-SLM) and a polarizing beam splitting prism. Moreover, this method is not limited by the wavelength of light wave and the pixel size of SLM. Theoretical analysis shows that when Gaussian beam or a plane beam is illuminated on a computer-generated hologram (CGH) specially designed in this work, the complex amplitudes of the vector field’s two orthogonal polarization components may be changed by modifying the encoding parameters, resulting in a vector beam with arbitrary complex amplitude and polarization in the output field. The experimental results also show that the two independent coding channels of the device have good polarization-selective imaging ability, which greatly improves the flexibility of generating arbitrary vector beams.

A Single-Celled Metasurface for Multipolarization Generation and Wavefront Manipulation.

Due to their unprecedented ability to flexibly manipulate the parameters of light, metasurfaces offer a new approach to integrating multiple functions in a single optical element. In this paper, based on a single-celled metasurface composed of chiral umbrella-shaped metal-insulator-metal (MIM) unit cells, a strategy for simultaneous multiple polarization generation and wavefront shaping is proposed. The unit cells can function as broadband and high-performance polarization-preserving mirrors. In addition, by introducing a chiral-assisted Aharonov-Anandan (AA) geometric phase, the phase profile and phase retardation of two spin-flipped orthogonal circular polarized components can be realized simultaneously and independently with a single-celled metasurface via two irrelevant parameters. Benefiting from this flexible phase manipulation ability, a vectorial hologram generator and metalens array with spatially varying polarizations were demonstrated. This work provides an effective approach to avoid the pixel and efficiency losses caused by the intrinsic symmetry of the PB geometric phase, and it may play an important role in the miniaturization and integration of multipolarization-involved displays, real-time imaging, and spectroscopy systems.

Switchable in-phase and out-phase polarization rotation vector solitons in a birefringence-managed fiber laser

Nonlinear polarization evolution of vector solitons is an interesting subject in nonlinear science and laser dynamics. Here, we demonstrate two types of switchable multiple polarization rotation vector solitons (PRVSs) in a mode-locked fiber laser through birefringence management. It is found that due to the polarization evolution induced gain competition and mode-coupling effect, the intensities of the two orthogonal polarization components of neighboring solitons differ in each round-trip, manifesting as the out-phase PRVSs. By adjusting the polarization orientation of injecting pulses with respect to the principal axis of polarization-maintaining fiber, neighboring solitons can project equal weight of intensity in two orthogonally-polarized directions, thus switching the out-phase PRVSs to the in-phase PRVSs. Real-time spectral measurement results validate the formation of two PRVSs, and reveal the distinct evolution dynamics. This work provides an effective method to control the polarization state of each soliton in multi-pulses mode-locked fiber lasers, and a potential avenue to introduce polarization-coding in optical soliton communications.

Effect of Twisting Phases on the Polarization Dynamics of a Vector Optical Field

The effect of twisting phases on the polarization dynamics of a vector vortex beam with a spatially variant state of polarization (SoP) is investigated theoretically and experimentally. The twisted vector vortex optical field with the cross-phase modulation is experimentally generated and observed. The presence of the twisting phases on the vector optical field results in novel propagation dynamics and the evolution of polarization states. The optical field performs the process of compressing and stretching the orthogonal polarization components and the linear-circular polarization conversions during propagation. Different from the scalar twisted beams, the orthogonal polarization components of twisted vector beams can be compressed along the same azimuthal angle or the orthogonal azimuthal angles, depending on the signs of the twist intensity coefficients. For an anisotropic twisted optical field, the SoP and the optical field rotate, and the rotation behaviors are sensitively dependent on the twisting coefficients. Furthermore, the two vortex topological charges embedded within the orthogonal polarization component of a twisted vector vortex beam can be simultaneously identified by looking at the interference fringes of the twisting phases. This work reveals that a vector vortex beam and its SoP can be dynamically manipulated by twisting phases.

Single shot polarimetric characterization of the polymer based flexible polyethylene terephthalate substrate

AbstractConducting polyethylene terephthalate (PET) substrates used for the flexible electronics and photonics are birefringent in nature. Birefringence of the PET substrate increases with the external applied stress. In this paper, we have studied the state of the polarization of the light transmitted through the flexible PET substrate. Polarimetric characterization of flexible substrate was done for red and yellow wavelengths of light. Single shot three beams interference was recorded by the polarizing Mach–Zehnder interferometer. Interferograms were recorded without bending and different external bending applied to the substrate which increases the stress. The recorded interferograms was analyzed by the Fourier transform fringe (FTF) analysis method. The single shot interferograms have the information of the amplitude and phase of orthogonally polarized field components. Stokes parameters were calculated from orthogonal polarization component extracted from the single shot interferograms analyzed by FTF. Calculated Stokes parameters were plotted on the Poincare sphere to see the change in the state of polarization (SOP) of the light transmitted through these substrates. The change in the SOP of the transmitted light was observed without and with the external stress applied to the PET substrate due to its birefringence characteristic.

Anti-scattering light focusing by full-polarization wavefront shaping based on digital micromirror devices

Focusing light inside scattering media has many applications and can be realized by the iterative method optimizing the wavefront of incident light. However, this method often achieves a moderate contrast of focus, which compromises its performance. Here, we propose full-polarization iterative wavefront shaping (FPI-WS) in which we adopt two digital micromirror devices. By modulating the two orthogonal polarization components independently, this method adds one more degree of freedom shaping the wavefront. In comparison with the previous result, FPI-WS can increase the peak to background ratio of focus by a factor of two.

Guiding and polarization shaping of vector beams in anisotropic media

We investigate a scheme to guide a weak vector beam using optically written waveguides inside atomic vapor, while controlling its polarization rotation. The atoms are prepared in the four-level tripod configuration in the presence of an external magnetic field. The three transitions of the tripod system are driven by a strong control beam and the two orthogonal polarization components of a weak vector beam (VB). A suitable spatial intensity profile and the detuning of the control field facilitate the generation of an optical fiberlike refractive index gradient across the atomic vapor. This enables waveguiding of the weak VB for a couple of Rayleigh lengths. Further, the magnetic-field-induced anisotropy of the tripod system creates a difference in the refractive indices of its two components. This is the reason behind the polarization shaping of VB. The mechanism of efficient guiding of VB with controllable polarization may have important applications in high-density optical communication and quantum information.