Showing papers on "Polarization rotator published in 2016"
TL;DR: In this article, a pseudo-high-order GVLVS with a two-humped pulse along one polarization and a single-hump pulse along the orthogonal polarization was obtained.
Abstract: Manipulation of group-velocity-locked vector solitons (GVLVSs) is numerically proposed and experimentally demonstrated. A pseudo-high-order GVLVS could be generated from a fundamental GVLVS with the help of a polarization-resolved system. Specifically, a pseudo-high-order GVLVS with a two-humped pulse along one polarization and a single-humped pulse along the orthogonal polarization could be obtained. The phase difference between the two humps could be 180°.
198 citations
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TL;DR: In this paper, the equivalence between normalized Stokes parameters and diffraction contrasts in appropriately designed phase-gradient birefringent metasurfaces was brought to the fore.
Abstract: Measuring light's state of polarization is an inherently difficult problem, since the phase information between orthogonal polarization states is typically lost in the detection process. In this work, we bring to the fore the equivalence between normalized Stokes parameters and diffraction contrasts in appropriately designed phase-gradient birefringent metasurfaces and introduce a concept of all-polarization birefringent metagratings. The metagrating, which consists of three interweaved metasurfaces, allows one to easily analyze an arbitrary state of light polarization by conducting simultaneous (i.e., parallel) measurements of the correspondent diffraction intensities that reveal immediately the Stokes parameters of the polarization state under examination. Based on plasmonic metasurfaces operating in reflection at the wavelength of 800 nm, we design and realize phase-gradient birefringent metasurfaces and the correspondent metagrating, while experimental characterization of the fabricated components convincingly demonstrates the expected functionalities. We foresee the use of the metagrating in compact polarimetric setups at any frequency regime of interest.
159 citations
TL;DR: This work presents the basic theory, simulated demonstration, and in-depth analysis of a high-performance broadband and invertible linear-to-circular (LTC) polarization converter composed of a single-layer gold nanorod array with a total thickness of ~λ/70 for the near-infrared regime that relaxation the high-precision requirements of the structure parameters in general metasurfaces while retaining the polarization conversion performance.
Abstract: The arbitrary control of the polarization states of light has attracted the interest of the scientific community because of the wide range of modern optical applications that such control can afford. However, conventional polarization control setups are bulky and very often operate only within a narrow wavelength range, thereby resisting optical system miniaturization and integration. Here, we present the basic theory, simulated demonstration, and in-depth analysis of a high-performance broadband and invertible linear-to-circular (LTC) polarization converter composed of a single-layer gold nanorod array with a total thickness of ~λ/70 for the near-infrared regime. This setup can transform a circularly polarized wave into a linearly polarized one or a linearly polarized wave with a wavelength-dependent electric field polarization angle into a circularly polarized one in the transmission mode. The broadband and invertible LTC polarization conversion can be attributed to the tailoring of the light interference at the subwavelength scale via the induction of the anisotropic optical resonance mode. This ultrathin single-layer metasurface relaxes the high-precision requirements of the structure parameters in general metasurfaces while retaining the polarization conversion performance. Our findings open up intriguing possibilities towards the realization of novel integrated metasurface-based photonics devices for polarization manipulation, modulation, and phase retardation.
121 citations
TL;DR: In this article, an ultra-wideband and high-efficiency polarization rotator based on a metasurface is proposed, which can rotate the polarization of linearly polarized electromagnetic (EM) wave to its orthogonal counterpart after reflection when the incident EM wave is y-/x-polarized.
Abstract: An ultra-wideband and high-efficiency polarization rotator based on a metasurface is proposed in this paper. The unit cell of the proposed polarization rotator consists of two pairs of L-shaped metallic patches printed on a substrate, which is backed by a metallic ground and covered by a superstrate. The superstrate is composed of a dielectric layer and a pair of L-shaped metallic patches printed on the dielectric layer. The proposed polarization rotator can rotate the polarization of linearly polarized electromagnetic (EM) wave to its orthogonal counterpart after reflection when the incident EM wave is y-/x-polarized. Simulated results show that the polarization rotator can perform 90° polarization rotation with very high efficiency at seven different frequencies and achieve a polarization conversion ratio higher than 0.9 in the frequency range of 7.8–34.7 GHz at normal incidence. Good agreement between the experimental results and simulated ones has been obtained.
94 citations
20 Apr 2016
TL;DR: In this paper, an impedance-matched polarization rotator with a subwavelength thickness of 1.56μm was designed using cascaded plasmonic sheets, which achieved an efficiency of 45% and extinction ratio of 115 (20.6 dB) at the operating wavelength of 0.56 µm.
Abstract: Controlling the polarization of light with efficient and ultra-thin devices is desirable for a myriad of optical systems. Bianisotropic metasurfaces offer a promising alternative to conventional optical components due to their ability to provide extreme wavefront and polarization control within a low profile. However, metasurfaces have typically suffered from poor efficiencies and extinction ratios due to the lack of systematic design procedures. Here, the first, to the best of our knowledge, impedance-matched polarization rotator with a subwavelength thickness that operates at optical frequencies is reported. The bianisotropic response needed for polarization rotation is systematically designed using cascaded plasmonic sheets. The metasurface is fabricated using straightforward nanolithography processes. Measurements demonstrate an efficiency of 45% and extinction ratio of 115 (20.6 dB) at the operating wavelength of 1.56 μm. This work experimentally demonstrates that a wide range of near-optimal bianisotropic responses can be designed and fabricated at optical frequencies. In the future, these surfaces could be utilized to develop high-performance, ultra-compact optical systems.
81 citations
TL;DR: In this paper, a high-efficiency and broadband reflective linear polarization rotator based on anisotropic metamaterial is proposed, which is verified by simulation and experiment, which can achieve 90° polarization rotation from 5.7 to 10.3 GHz with the relative bandwidth of 57.5%.
Abstract: In this paper, a high-efficiency and broadband reflective linear polarization rotator based on anisotropic metamaterial is proposed, which is verified by simulation and experiment. Simulated results indicate that our design can achieve 90° polarization rotation from 5.7 to 10.3 GHz with the relative bandwidth of 57.5 %, which is agreement well with experiment. The further simulated results indicate that our design can achieve linear polarization conversion or rotation by 90° under oblique incident angles with large range for both transverse electric and transverse magnetic waves. Finally, the amplitude and phase of reflective coefficients with different polarization, and surface current distribution of the unit cell structure are simulated to explain the physics mechanism of the high-efficiency and broadband polarization rotation. Our design will provide an important reference for the practical applications of the metamaterial in polarization manipulation.
74 citations
TL;DR: A polarizing birefringent NANF design that can achieve orthogonal polarization loss ratios as large as 30dB over the C-band while eliminating any undesirable polarization coupling effect thereby resulting in a single polarization output in a hollow core fiber regardless of the input polarization state is proposed.
Abstract: We systematically study different approaches to introduce high birefringence and high polarization extinction ratio in hollow core antiresonant fibers. Having shown the ineffectiveness of elliptical cores to induce large birefringence in hollow core fibers, we focus on designing and optimizing polarization maintaining Hollow Core Nested Antiresonant Nodeless Fibers (HC-NANF). In a first approach, we create and exploit anti-crossings with glass modes at different wavelengths for the two polarizations. We show that suitable low loss high birefringence regions can be obtained by appropriately modifying the thickness of tubes along one direction while leaving the tubes in the orthogonal direction unchanged and in antiresonance. Using this concept, we propose a new birefringent NANF design providing low loss (~40dB/km) and high birefringence (>10−4) over a record bandwidth of ~550nm, and discuss how bandwidth can be traded off to further reduce the loss to a few dB/km. Finally, we propose a polarization mode-stripping technique in the birefringent NANF. As a demonstration, we propose a polarizing birefringent NANF design that can achieve orthogonal polarization loss ratios as large as 30dB over the C-band while eliminating any undesirable polarization coupling effect thereby resulting in a single polarization output in a hollow core fiber regardless of the input polarization state.
69 citations
18 Nov 2016
TL;DR: In this article, the authors proposed and experimentally demonstrated an ultra-compact and highly efficient polarization splitter and rotator based on a silicon bent directional coupler structure, which achieved a peak TM-to-TE polarization conversion efficiency of 96.9%.
Abstract: We propose and experimentally demonstrate an ultra-compact and highly efficient polarization splitter and rotator based on a silicon bent directional coupler structure. The TM-to-TE cross-polarization coupling occurs between the two parallel bent waveguides, if the phase matching condition is satisfied. Efficient polarization splitting and rotating are simultaneously achieved. The device is fabricated by a single step of exposure and etching. The measured peak TM-to-TE polarization conversion efficiency reaches 96.9%. The TM-to-TE conversion loss is lower than 1 dB in the wavelength range of 1544 nm–1585 nm, and the insertion loss for the TE polarization is lower than 0.3 dB in the wavelength regime of 1530 nm–1600 nm. The cross talk values are lower than −20 and −18 dB for the TE- and TM-polarizations over a wavelength range of 70 nm, respectively. The coupling length of the polarization splitter and rotator is 8.77μm. To the best of our knowledge, our device achieves the shortest coupling length.
62 citations
Abstract: Spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) offer a high potential to overcome several limitations of conventional purely charged-based laser devices. Presumably, the highest potential of spin-VCSELs lies in their ultrafast spin and polarization dynamics, which can be significantly faster than the intensity dynamics in conventional devices. Here, we experimentally demonstrate polarization oscillations in spin-VCSELs with frequencies up to 44 GHz. The results show that the oscillation frequency mainly depends on the cavity birefringence, which can be tuned by applying mechanical strain to the VCSEL structure. A tuning range of about 34 GHz is demonstrated. By measuring the polarization oscillation frequency and the birefringence governed mode splitting as a function of the applied strain simultaneously, we are able to investigate the correlation between birefringence and polarization oscillations in detail. The experimental findings are compared to numerical calculations based on ...
61 citations
TL;DR: In this paper, a tunable fiber polarization filter by filling different index liquids into the central hole of photonic crystal fiber (PCF) is proposed and demonstrated, and the dispersion characteristics and loss spectra of the polarization filter are evaluated by finite element method (FEM).
Abstract: A tunable fiber polarization filter by filling different index liquids into the central hole of photonic crystal fiber (PCF) is proposed and demonstrated. The dispersion characteristics and loss spectra of the polarization filter are evaluated by finite element method (FEM). The gold wires are selectively filled into the cladding air holes of the PCF. When the phase matching condition is satisfied, the liquid-core mode couples to surface plasmon polaritons (SPP) mode intensely. The resonance wavelength varies with the change of the structural parameters and liquids. By adjusting the refractive index of the liquid, we realize the polarization filter at the wavelength of 1.31, 1.49, and 1.55 $\mu$ m, respectively, under the optimized structural parameters. This is the first time to propose the narrowband polarization filter at the communication wavelength of 1.31 $\mu$ m to our best knowledge based on the coupling between liquid-core mode and SPP mode, and the full width half maximum (FWHM) is only 16 nm. The loss of X-polarized mode is 44336 dB/m at $\lambda$ = 1.31 $\mu$ m, and the corresponding loss of Y-polarization mode is 224 dB/m. By comparison, we find the birefringence in our structure is further better than that in conventional structure. High birefringence is helpful to separate the resonance wavelength positions of the two orthogonal polarized modes. The result also reveals that resonance loss becomes small with increasing the distance between liquid core and gold wire.
TL;DR: In this article, a simple and broadband reflective polarization converter is realized at GHz frequencies by breaking the symmetry of the cross-shaped resonator in metamaterials, and the experimental results demonstrate that the polarization conversion ratio (PCR) over 0.8 is achieved from 8.3 GHz to 14 GHz for linearly polarized (LP) incident waves under normal incidence.
Abstract: Cross-shaped resonator (CSR) in metamaterial usually corresponds to adjust resonant characteristics. In this report, a simple and broadband reflective polarization converter is realized at GHz frequencies by breaking the symmetry of the CSR. The experimental results demonstrate that the polarization conversion ratio (PCR) over 0.8 is achieved from 8.3 GHz to 14.3 GHz for linearly polarized (LP) incident waves under normal incidence. The high polarization conversion efficiency can be sustained when the incident angle increases to 60 degrees. By taking advantage of surface current distribution and the interference theory, the physical mechanisms are elucidated in detail. Finally, the broadband polarization conversion can also be achieved by decreasing the geometrical parameters of the converter in the mid-infrared frequency range.
TL;DR: Three-dimensional (3D) head-mounted display (HMD) providing multi-focal and wearable functions by using polarization-dependent optical path switching in Savart plate is proposed and the integration of real world scene and high quality 3D images is confirmed.
Abstract: We propose three-dimensional (3D) head-mounted display (HMD) providing multi-focal and wearable functions by using polarization-dependent optical path switching in Savart plate. The multi-focal function is implemented as micro display with high pixel density of 1666 pixels per inches is optically duplicated in longitudinal direction according to the polarization state. The combination of micro display, fast switching polarization rotator and Savart plate retains small form factor suitable for wearable function. The optical aberrations of duplicated panels are investigated by ray tracing according to both wavelength and polarization state. Astigmatism and lateral chromatic aberration of extraordinary wave are compensated by modification of the Savart plate and sub-pixel shifting method, respectively. To verify the feasibility of the proposed system, a prototype of the HMD module for monocular eye is implemented. The module has the compact size of 40 mm by 90 mm by 40 mm and the weight of 131 g with wearable function. The micro display and polarization rotator are synchronized in real-time as 30 Hz and two focal planes are formed at 640 and 900 mm away from eye box, respectively. In experiments, the prototype also provides augmented reality function by combining the optically duplicated panels with a beam splitter. The multi-focal function of the optically duplicated panels without astigmatism and color dispersion compensation is verified. When light field optimization for two additive layers is performed, perspective images are observed, and the integration of real world scene and high quality 3D images is confirmed.
TL;DR: A single layer all-dielectric metasurface lens to simultaneously convert and focus an incident linear polarization into a radial beam with high efficiency and high numerical aperture (NA) is proposed.
Abstract: We propose a single layer all-dielectric metasurface lens to simultaneously convert and focus an incident linear polarization into a radial beam with high efficiency and high numerical aperture (NA). It shows a better focusing property compared with the linearly polarized metasurface lens for high NA. A tight spot size (0.502λ) is achieved for the NA = 0.94. Additionally, the emergent polarization can in principle be switched flexibly between radially and azimuthally polarized beams by the adjustment of incident polarization direction. It is expected that our scheme may have potential value in microscopy, material processing, medicine, particles accelerating and trapping, and so on.
TL;DR: An experimental set-up is presented, which generates a Bessel-type vector beam with a spatial polarization, oscillating along the optical axis, when propagating in free space.
Abstract: Bessel beams are widely used in optical metrology mainly because of their large Rayleigh range (focal length). Radial/azimuthal polarization of such beams is of interest in the fields of material processing, plasma absorption or communication. In this paper an experimental set-up is presented, which generates a Bessel-type vector beam with a spatial polarization, oscillating along the optical axis, when propagating in free space. A first holographic axicon (HA) HA1 produces a normal, linearly polarized Bessel beam, which by a second HA2 is converted into the spatial oscillating polarized beam. The theory is briefly discussed, the set-up and the experimental results are presented in detail.
TL;DR: In this article, the emergence of polarization singularities in the scattered fields of optical resonators excited by linearly polarized plane waves was studied, and it was shown that high refractive index spherical resonators present such topologically protected features.
Abstract: In this article, we study the emergence of polarization singularities in the scattered fields of optical resonators excited by linearly polarized plane waves. First, we prove analytically that combinations of isotropic electric and magnetic dipoles can sustain L surfaces, and C lines that propagate from the near-field to the far field. Moreover, based on these analytical results, we derive anomalous scattering Kerker conditions trough singular optics arguments. Secondly, through exact full-field calculations, we demonstrate that high refractive index spherical resonators present such topologically protected features. Furthermore, we calculate the polarization structure of light around the generated C lines, unveiling a Mobius strip structure in the main axis of the polarization ellipse. These results prove that high-index nanoparticles are excellent candidates for the generation and control of polarization singularities and that they may lead to new platforms for the experimental study of the topology of light fields around optical antennas.
TL;DR: In this paper, a new chiral spiral slot structure is proposed in the THz region and the chiral properties of the new spiral configuration are examined on the basis of the cross polarization conversion.
Abstract: A new chiral spiral slot structure is proposed in THz region. The chiral properties of the new spiral configuration are examined on the basis of the cross polarization conversion. The linearly polarized wave can be converted completely into its cross-polarized wave in dual-band. A numerical study was carried out, followed by an explanation of the cross-polarization conversion mechanism in the structure proposed in this work. A strong chirality can be caused owing to the cross coupling between the magnetic field and incident electric field. These novel properties can lead to new possibilities and solution in many valuable applications, such as communication system, polarization-insensitive devices and 90° polarization rotator.
TL;DR: In this paper, a 3D multilevel radiative transfer investigation about the solar disk-center polarization of the Ca Ω(sc ii) 8542 A line is presented, where the authors investigate the linear polarization due to the atomic level polarization produced by the absorption and scattering of anisotropic radiation.
Abstract: We highlight the main results of a three-dimensional (3D) multilevel radiative transfer investigation about the solar disk-center polarization of the Ca {\sc ii} 8542 A line. First, we investigate the linear polarization due to the atomic level polarization produced by the absorption and scattering of anisotropic radiation in a 3D model of the solar atmosphere, taking into account the symmetry breaking effects caused by its thermal, dynamic and magnetic structure. Second, we study the contribution of the Zeeman effect to the linear and circular polarization. Finally, we show examples of the Stokes profiles produced by the joint action of atomic level polarization and the Hanle and Zeeman effects. We find that the Zeeman effect tends to dominate the linear polarization signals only in the localized patches of opposite magnetic polarity where the magnetic field is relatively strong and slightly inclined, while outside such very localized patches the linear polarization is often dominated by the contribution of atomic level polarization. We demonstrate that a correct modeling of this last contribution requires taking into account the symmetry breaking effects caused by the thermal, dynamic and magnetic structure of the solar atmosphere, and that in the 3D model used the Hanle effect in forward-scattering geometry (disk center observation) mainly reduces the polarization corresponding to the zero-field case. We emphasize that, in general, a reliable modeling of the linear polarization in the Ca {\sc ii} 8542 A line requires taking into account the joint action of atomic level polarization and the Hanle and Zeeman effects.
TL;DR: An active meta-mirror is proposed to dynamically manipulate electromagnetic polarization state at a broad band using double-layered metallic pattern backed by a metallic flat plate to control the reflection phase difference between two orthogonal polarization modes.
Abstract: Polarization control of electromagnetic wave is very important in many fields. Here, we propose an active meta-mirror to dynamically manipulate electromagnetic polarization state at a broad band. This meta-mirror is composed of a double-layered metallic pattern backed by a metallic flat plate, and the active elements of PIN diodes are integrated into the meta-atom to control the reflection phase difference between two orthogonal polarization modes. Through switching the operating state of the PIN diodes, the meta-mirror is expected to achieve three polarization states which are left-handed, right-handed circular polarizations and linear polarization, respectively. We fabricated this active meta-mirror and validated its polarization conversion performance by measurement. The linearly polarized incident wave can be dynamically converted to right-handed or left-handed circular polarization in the frequency range between 3.4 and 8.8 GHz with the average loss of 1 dB. Furthermore, it also can keep its initial linear polarization state.
TL;DR: In this paper, the stability of self-injection locking with DFB laser coupled with an external fiber optic ring cavity was studied, and two regimes of mode hopping were observed; one of them is accompanied by polarization bistability involving two orthogonal polarization states.
Abstract: We study stability of self-injection locking realized with DFB laser coupled with an external fiber optic ring cavity. Polarization behavior of the radiation circulating in the feedback loop is reported. Two regimes of mode hopping have been observed; one of them is accompanied by polarization bistability involving two orthogonal polarization states.
TL;DR: In this paper, a multi-conductor transmission line (MTL) model is implemented to characterize how vertically and horizontally polarized waves are transmitted and reflected through the surface and to synthesize the desired tensor impedances, which comprise the array.
Abstract: Tensor impedance transmitarrays consist of tensor impedance surfaces, separated by dielectric spacers. In this paper, we present a design method for realizing tensor impedance transmitarrays that are capable of controlling the reflection and transmission of circularly polarized waves, referred to as chiral polarization control. To achieve this, we implement a multi-conductor transmission-line (MTL) model to characterize how vertically and horizontally polarized waves are transmitted and reflected through the surface and to synthesize the desired tensor impedances, which comprise the array. Using this MTL model, we show how to synthesize two different chiral transmitarrays. This includes a polarization rotator, which rotates any linear polarization by 90 $^{\circ}$ and a circular polarization selective surface (CPSS), which transmits one hand of circular polarization while reflecting the other. This is verified with full-wave simulation showing that our proposed model works. We also fabricate and measure the CPSS at X-band based on our design procedure. To measure the CPSS, we use a novel four-port quasi-optical system to characterize both the reflection and transmission of vertically and horizontally polarized fields off of the surface. We achieve a good agreement with our simulated results though we have $-{\hbox{1.7 dB}}$ more loss than expected due to the use of FR-4 as our substrate.
TL;DR: A novel chiral metamaterial consisting of double L resonators on two sides of the dielectric substrate is proposed in this paper, which can realize broadband asymmetric transmission and polarization conversion of a linearly polarized wave in the terahertz band.
TL;DR: In this article, a three-layered chiral structure is proposed and investigated, which consists of a split-ring resonator sandwiched between two layers of sub-wavelength gratings.
Abstract: In the paper, a novel three-layered chiral structure is proposed and investigated, which consists of a split-ring resonator sandwiched between two layers of sub-wavelength gratings. This designed structure can achieve simultaneously asymmetric transmission with an extremely broad bandwidth and high amplitude as well as multi-band 90° polarization rotator with very low dispersion. Numerical simulations adopted two kinds of softwares with different algorithms demonstrate that asymmetric parameter can reach a maximum of 0.99 and over than 0.8 from 4.6 to 16.8 GHz, which exhibit magnitude and bandwidth improvement over previous chiral metamaterials in microwave bands (S, C, X and Ku bands). Specifically, the reason of high amplitude is analyzed in detail based on the Fabry-perot like resonance. Subsequently, the highly efficient polarization conversion with very low dispersion between two orthogonal linearly polarized waves is also analyzed by the optical activity and ellipticity. Finally, the electric fields are also investigated and further demonstrate the correctness of the simulated and calculated results.
TL;DR: This work proposes a tunable reflective guided-mode resonant (GMR) filter that incorporates a 90° twisted nematic liquid crystal (TNLC) and acts as an optical resonator that reflects strongly at the resonance wavelength and as an alignment layer for LC.
Abstract: This work proposes a tunable reflective guided-mode resonant (GMR) filter that incorporates a 90° twisted nematic liquid crystal (TNLC). The GMR grating acts as an optical resonator that reflects strongly at the resonance wavelength and as an alignment layer for LC. The 90° TNLC functions as an achromic polarization rotator that alters the polarization of incident light. The resonance wavelength and reflectance of such a filter can be controlled by setting the angle of incidence and driving the 90° TNLC, respectively. The designed filter exhibits a very large spectral shift in resonance wavelength from 710 to 430 nm, which covers the entire visible spectrum. The transmittance can be tuned to within 10 V at various resonance wavelengths. The hybrid GMR - LC filter is compact, has a simple design, and is easy to fabricated. It can therefore be used in practical applications.
TL;DR: In this article, a dual-band and high-efficiency polarization converter in microwave regime was proposed, which can convert a linearly polarized wave to its cross-polarized wave for two distinct bands: Ku (11.5-20.0GHz) and Ka (28.8-34.0 GHz).
Abstract: We present a dual-band and high-efficiency polarization converter in microwave regime. The proposed converter can convert a linearly polarized wave to its cross-polarized wave for two distinct bands: Ku (11.5–20.0 GHz) and Ka (28.8–34.0 GHz). It can also convert the linearly polarized wave to a circularly polarized wave at four other frequencies. The experimental results are in good agreement with simulation results for both frequency bands. The polarization conversion ratio is above 0.94 for the Ku-band and 0.90 for the Ka-band. Furthermore, the converter can achieve dual-band and high-efficiency polarization conversion over angles of incidence up to 45°. The converter is also polarization-selective in that only the x- and y-polarized waves can be converted. The physical mechanism of the dual-band polarization conversion effect is interpreted via decomposed electric field components that couple with different plasmon resonance modes of the structure.
TL;DR: In this paper, a three-dimensional metamaterial was proposed to realize a broadband and efficient polarization conversion, which is composed of a pseudo-planar structure and a ground plane separated by a dielectric spacer.
Abstract: In this paper, a three-dimensional metamaterial was proposed to realize a broadband and efficient polarization conversion. The unit cell of the three-dimensional metamaterial is composed of pseudo-planar structure and a ground plane separated by a dielectric spacer. The linear polarization of incident waves can be converted to its orthogonal direction upon reflection. The simulated results show that the polarization conversion ratio of more than 95 % is observed in the broad frequency range from 7.39 to 13.87 THz. The novel pseudo-planar reflective polarization converter can improve the magnitude of the polarization conversion ratio compared to previous works. To explain the mechanism of the proposed structure, the surface current distributions are investigated. In addition, the right-hand circularly polarized incident waves can also be converted to left-hand circularly polarized wave with broadband and efficient polarization conversion. The proposed metamaterial provides an alternative platform to promote potential applications in the terahertz region.
TL;DR: In this paper, the authors proposed a compact silicon-on-insulator polarization splitter-rotator (PSR), which consists of an asymmetric bilevel lateral taper in an adiabatic directional coupler.
Abstract: We propose a compact silicon-on-insulator polarization splitter-rotator (PSR). The PSR consists of an asymmetric bilevel lateral taper in an adiabatic directional coupler and convert TM0 mode to TE0 mode directly without changing the input TE0 mode. Compared to the previously reported PSR based on TM0 –TE1 polarization rotator connected to a TE1–TE0 spatial mode order convertor in series, the proposed PSR has a one-step mode conversion, and is inherently more compact. Beside, since the conversion is fully adiabatic, it preserves the benefits of large fabrication tolerance and operation bandwidth. The simulation results show that the TM0–TE0 polarization conversion loss is less than 0.5 dB from 1500 to 1700 nm and even less than 0.2 dB over the whole C-band. The TE0 –TE0 insertion loss is less than 0.01 dB from 1450 to 1750 nm. The polarization crosstalk is below –35 dB within 300-nm bandwidth.
TL;DR: This work proposes specially designed double anisotropic polarization diffraction gratings capable of producing a selective number of diffraction orders and with selective different states of polarization.
Abstract: We propose specially designed double anisotropic polarization diffraction gratings capable of producing a selective number of diffraction orders and with selective different states of polarization. Different polarization diffraction gratings are demonstrated, including linear polarization with horizontal, vertical and ± 45° orientations, and circular R and L polarization outputs. When illuminated with an arbitrary state of polarization, the system acts as a complete polarimeter where the intensities of the diffraction orders allow measurement of the Stokes parameters with a single shot. Experimental proof-of-concept is presented using a parallel-aligned liquid crystal display operating in a double pass architecture.
TL;DR: In this paper, a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA) that evanescently interacts with light on a side-polished polarization-maintaining fiber (PMF) platform was implemented.
Abstract: We implemented a single-walled carbon nanotube (SWCNT)-based saturable absorber (SA) that evanescently interacts with light on a side-polished polarization-maintaining fiber (PMF) platform. A high-quality SWCNT/polymer composite was spin-coated onto a side-polished PMF embedded in a quartz block, where the slow optical birefringence axis of the PMF was perpendicular to the polished surface. The fabricated in-line SA had an insertion loss of –1.5 dB with a modulation depth of 0.5% for the polarization direction associated with the transvers magnetic mode. An all-PMF laser was built using the fabricated in-line SA to demonstrate self-starting, turn-key operation of Er-doped, all-fiber lasers delivering stable scalar soliton pulses. The measured 3-dB spectral bandwidth and pulse duration of the laser output were 5.1 nm and 510 fs, respectively, resulting in a time-bandwidth product of 0.320. We examined the polarization state of the soliton fiber laser output and found that the laser stably generated linearly polarized ultrashort pulses with a polarization extinction ratio of –18.4 dB.
TL;DR: In this paper, a simple design of an ultrabroadband and high-efficiency reflective linear polarization convertor is presented in the optical frequency region, where the polarization conversion ratio over 90% is achieved from 181 to 506 THz, which is equivalent to 94.6% relative bandwidth for y -polarized incident lights under normal incidence.
Abstract: A simple design of an ultrabroadband and high-efficiency reflective linear polarization convertor is presented in the optical frequency region. This ultrabroadband convertor is formed from the planar anisotropic metasurface using a meander wire structure. The numerical simulation demonstrates that the polarization conversion ratio over 90% is achieved from 181 to 506 THz, which is equivalent to 94.6% relative bandwidth for y -polarized incident lights under normal incidence. Further simulation results show that the high polarization conversion efficiency can be sustained well when the incident angle increases to 45 ${}^{\circ}$ for both transverse electric (TE) and transverse magnetic (TM) modes. By taking advantage of surface current distribution, the physical mechanisms are elucidated in detail. The further theoretical calculation results based on the interference theory are good agreement with the simualtion. Our design provides a unique approach in realizing the polarization manipulation with high performances in the optical frequency region.