Efficient Polarization Rotator Research Articles

Compact and efficient polarization rotator using laterally asymmetric rib waveguides on a lithium-niobate-on-insulator platform.

Photonic devices based on a lithium-niobate-on-insulator (LNOI) are current research hotspots; however, owing to the high refractive index contrast of the LNOI platform and inherent birefringence of lithium niobate itself, such photonic devices are generally polarization sensitive, affecting their further wide application. This paper proposes a simple, compact, and efficient polarization rotator (PR) based on a laterally asymmetric rib waveguide by depositing a layer of semi-infinite silicon nitride dielectric material on one side of the rib waveguide. The results show that a PR with a polarization rotation region length of 15.77µm is achieved, and the polarization extinction ratio (PER), insertion loss (IL), and polarization conversion efficiency (PCE) are 38.57/68.95 and 0.2/0.22dB, and 99.99%/almost 100%, respectively, for the fundamental transverse electric mode (T E 0) and transverse magnetic mode (T M 0) at a 1.55µm wavelength. The operation bandwidth is around 120nm for the T E 0 mode and T M 0 mode when the PER, IL, and PCE are greater than 20dB, less than 0.32dB, and more than 99%, respectively. Fabrication tolerances to the key structural parameters are investigated in detail. In addition, the evolution fields of the T E 0 mode and T M 0 mode along the propagation direction through the proposed device are presented.

Highly efficient and tunable polarization rotator based on lithium niobate on an insulator.

The lithium niobate on an insulator (LNOI) platform has greatly advanced the development of integrated photonics recently, where efficient polarization management components are indispensable. In this work, we propose a highly efficient and tunable polarization rotator based on the LNOI platform and the low-loss optical phase change material antimony triselenide (S b 2 S e 3). The key polarization rotation region is formed by a LNOI waveguide with a cross section of the double trapezoidal shape and a S b 2 S e 3 layer deposited atop the LNOI waveguide in an asymmetrical way, where an isolating layer of silicon dioxide is sandwiched between them to reduce the material absorption loss. Based on such a structure, we have achieved the efficient polarization rotation in a length of only 17.7µm, where the polarization conversion efficiency and insertion loss are 99.6% (99.2%) and 0.38dB (0.4dB) for the trans-electric (TE)-to-trans-magnetic (TM) rotation. If we further change the phase state of the S b 2 S e 3 layer, other polarization rotation angles besides 90° can also be obtained for the same device, revealing a tunable function. We believe that the proposed device and design scheme could offer an efficient method for realizing the polarization management on the LNOI platform.

Ultra-wideband efficient polarization conversion of terahertz wave in a planar metamaterial

We have investigated numerically and experimentally an ultra-wideband efficient polarization conversion of a linearly polarized terahertz wave in a planar metamaterial (MM) geometry comprising an array of C-shaped resonators. Both the co- and cross-polarization transmission spectra of the proposed MM configuration have been studied for numerous polarizations of incident terahertz starting from 0∘ to 90∘ in steps of 15∘. Our design promises a cross-polarization conversion of 40% from 1.22 to 2.75 THz with a maximum of 45% when the MM design is rotated by 45∘ with respect to the incident light. The change in rotation angle excites an electric dipole in the C resonator, which radiates an electric field in the co-and cross-polarization. The polarization conversion has been explained with induced electric field profiles as well as surface current profiles. It is shown that the change in dimension of the C-shaped resonator causes a shift in the transmission spectrum. Numerically simulated results are in good agreement with the experimental results. Our design eliminates the complexity of the fabrication of multilayer structures and opens avenues to design ultra-wideband and efficient polarization rotation devices in the terahertz frequency regime.

Compact Lithium-Niobate-on-Insulator Polarization Rotator Based on Asymmetric Hybrid Plasmonics Waveguide

We proposed a compact and efficient polarization rotator (PR) based on an asymmetric hybrid plasmonics waveguide (HPW) on the lithium-niobate-on-insulator (LNOI) platform. We focus on the design of rotation angle and balance between the two hybrid modes. The presented device exhibits a polarization extinction ratio as high as 59.58 dB and an insertion loss of 1.44 dB with the rotation length of only 13.7 μm. The fabrication tolerances and a suitable process are also discussed to meet the state-of-art technology.

Arbitrarily Directional and Tunable Polarization Rotating Effect with Coupled Metal Screens

Active polarization rotators are desirable for many applications in photonics. Metasurfaces based on phase-change or magneto-optical materials can do the job, but suffer from long response time or the need for a strong magnetic field. This study reports tunable and omnidirectional polarization rotation using a pair of coupled, perforated metal screens. Here the tuning originates from the near-field coupling of the screens and its dependence on lateral displacement. For millimeter-scale displacement, continuous and efficient polarization rotation from -90 to 90 degrees can be achieved in the microwave band, and the effect could also be extended to the terahertz regime.

Design of a silicon-on-calcium-fluoride-based compact and efficient polarization rotator for the mid-IR

We report the design of a chip-scale and highly efficient polarization rotator (PR) based on an asymmetric directional coupler geometry involving a horizontal slot waveguide (WG) and a strip WG on a silicon-on-calcium-fluoride (SOCF) platform for the mid-IR regime. In particular, we have optimized it for rotations of both the polarizations at the operating wavelength of 4.47 µm in two configurations, which relied on single and double-slot WG geometries. Power coupling through appropriate phase matching between the quasi-TM mode of a horizontal slot WG and the quasi-TE mode of a strip WG has been exploited for realizing polarization rotation. Numerical simulations demonstrate that achievable maximum power coupling efficiency (Cm) is as high as ~95% (with a device length of ~0.57 mm) for the single slot WG geometry and ~97% (with an even shorter device length of ~0.47 mm) for the PR based on double-slot WG geometry for both the polarizations. Both the designed PRs exhibit relatively large bandwidth of 50 nm with reasonably high Cm of ~80%. A study on fabrication tolerances show that Cm remains ~80% for variation in width Δw from -2 to +3 nm and -6 to +5 nm for single and double-slot based PRs, respectively.

Design of a promising silicon slot waveguide-based ultra-short low loss efficient polarization rotator for the mid-IR

We propose design of a promising ultra-short and highly efficient mid-IR polarization rotator (PR) on silicon-on-calcium-fluoride (SOCF) platform, whose rotation section is formed from an asymmetric slot waveguide for the working wavelength of 4.47 μm by exploiting mode coupling scheme. Numerical results demonstrate that within a conversion length of just ∼18 μm, the maximum achievable polarization conversion efficiency (PCE) for both the polarizations (TE-TM and TM-TE) is as high as ∼100% with significantly low loss of ∼ 0.15 dB. Achieved polarization extinction ratios (PERs) are as high as 43.3 dB and 34.9 dB for TE-TM and TM-TE polarizations, respectively. Furthermore, over a large bandwidth of 360 nm (4.29–4.65 μm), our designed PR exhibits very high PCE (> 98%) for both the TE-TM and vice versa with an appreciable PER of ∼18 dB and relatively low loss of ∼ 0.26 dB. Study on fabrication tolerances reveals that designed PR is robust to potential imperfections in fabrication. To the best of our knowledge, our designed PR is the shortest PR reported to date for the mid-IR wavelength regime with a healthy balance/compromise between PCE, PER, bandwidth, loss and fabrication tolerance.

Ultra-compact and highly efficient polarization rotator utilizing multi-mode waveguides.

An ultra-compact and highly efficient polarization rotator is proposed and experimentally realized on the silicon-on-insulator (SOI) platform. The polarization rotation (TM0-TE1) process is obtained by utilizing a straight multi-mode waveguide, while the mode conversion (TE1-TE0) process is realized by a bent multi-mode waveguide. For the proposed structure, only one etching step is required for the fabrication. The measured extinction ratio and insertion loss at the central wavelength are 19.8 and 0.86dB, which agree well with the simulations.

A near-transparent 90∘ polarization rotator with an array of L-shaped holes inside a glass cube

We report a near-transparent 90[Formula: see text] polarization rotator by using a single-layer microstructure. The co-polarization light has been suppressed by using destructive interference. At the same time, the transmission of cross-polarization light has been improved with inference effect between surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs). This efficient polarization rotation mechanism may be very useful in designing polarization rotators.

Integrated polarization rotator made of periodic asymmetric buried Ta2O5 / silica sol-gel waveguides

A ridge waveguide technology exhibiting high polarization dependency is developed for new efficient multi-section passive polarization rotator applications. In the presented configuration, the calculated mode coupling between the waveguide sections is very efficient and allows a polarization rotation with a high extinction ratio at lambda=1,55 mum. Experimental results show efficient polarization rotation with low cross-talk levels (-16dB) and no significant excess losses between sections. However, the overall transmission efficiency is limited by propagation losses and coupling losses to standard optical fibers.