Passive Polarization Rotator Research Articles

Design of an X-cut thin-film lithium niobate waveguide as a passive polarization rotator

The transverse-electric and transverse-magnetic modes of an X-cut thin-film lithium niobate waveguide vary in effective indices and exchange power when the waveguide makes an oblique angle with its crystallographic Z-axis, i.e. its optics axis. We leverage this phenomenon to design a passive fundamental-mode polarization rotator. In our design, the lithium niobate waveguide is tilted at an optimum angle with respect to its Z-axis, such that material anisotropy induces phase-matched polarization conversion. We discuss the rotator’s ideal-device length, crosstalk, and bandwidth. The proposed design yields compact (shorter than 1 mm), low-loss, passive polarization rotators for telecom wavelengths.

Highly efficient passive InP polarization rotator-splitter.

Monolithically integrated polarization beam splitters (PBSs) are needed to reduce the form-factor and assembly cost of optical coherent receivers. A highly efficient passive polarization rotator and splitter based on mode-evolution is demonstrated. The device is fabricated on InP substrate with a single etch-step and uses an adiabatic mode-converter and an asymmetric Y-coupler. Despite its simple fabrication process, the device shows a polarization extinction ratio (PER) better than 19 dB over 1520 nm to 1620 nm, thus covering both C- and L-band. The peak value of 24 dB is obtained for TE and TM polarizations. Its fabrication tolerance is large, so that even under a width variation of +/- 200 nm the PER remains above 17 dB over the entire C- and L-band.

Optimization of Photonic Crystal Polarization Handling Devices Using Trust Region Algorithms

In this paper, the trust region optimization techniques are used for the design of photonic crystal polarization handling devices. The trust region algorithms are based on quadratic surrogate models with no derivative requirements to replace the objective function in the optimization process. A new box constrained trust region algorithm is employed for the first time to the best of our knowledge along with full vectorial finite difference methods to optimize a passive polarization rotator (PR) based on silica photonic crystal fiber (PCF). The reported PCF PR has a device length of 204 μm with nearly 100% polarization conversion ratio at operating wavelength λ of 1.55 μm. Further, an unconstrained trust region (UTR) algorithm is used for optimizing the coupling characteristics of a soft glass nematic liquid crystal (NLC) PCF coupler. The optimized coupler can separate the two polarized beams with compact length of 380 μm and low crosstalk at λ = 1.55 μm. Furthermore, a polarization independent NLC-PCF multiplexer–demultiplexer is proposed for wavelengths of 1.3 and 1.55 μm using the UTR technique with a compact device length of 475 μm and low crosstalk for the two polarization states.

Passive polarization rotator based on silica photonic crystal fiber for 1.31-μm and 1.55-μm bands via adjusting the fiber length

A new polarization rotator based on the silica photonic crystal fiber is proposed. The proposed polarization rotator photonic crystal fiber (PR-PCF) possesses a triangle jigsaw-shape core region. The full-vector finite-element method is used to analyze the phenomenon of polarization conversion between the quasi-TE and quasi-TM modes. Numerical simulations show that the wavelengths of 1.31 μm and 1.55 μm are converted with a nearly 100% polarization conversion ratio with their matched coupling length and has a relatively strong realistic fabrication tolerance −100 nm on the y axis and 50 nm on the x axis. The full vectorial finite difference beam propagation method is used to confirm the performance of the proposed PR-PCF.

Novel Passive Polarization Rotator Based on Spiral Photonic Crystal Fiber

In this letter, a novel design of a passive ultra-compact polarization rotator based on soft glass equiangular spiral photonic crystal fiber (ES-PCF) is proposed and analyzed using full vectorial finite difference approaches. The suggested ES-PCF has eight arms with a central elliptical air hole, which can be shifted in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$x$</tex> </formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$y$</tex> </formula> directions to achieve complete polarization conversion. In addition, the major axis of the elliptical hole is rotated by 45 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{\circ}$</tex></formula> , which offers 99% polarization conversion ratio with ultra-compact device length of 96 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\mu{\rm m}$</tex></formula> . It is also evident from the numerical results that the polarization rotation would be more than 98% over the 1.5–1.6 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> wavelength range.

Design Consideration of Polarization Converter Based on Silica Photonic Crystal Fiber

In this paper, the performance of a novel design of passive polarization rotator (PR) based on silica photonic crystal fiber is studied and analyzed using the full vectorial finite difference method along with the full vectorial finite difference beam propagation method. The proposed design has a rectangular core region with a slanted sidewall. The influence of the different structure geometrical parameters and operating wavelengths on the PR performance is investigated. At a wavelength of 1.55 μm, nearly 100% polarization conversion ratio is obtained, with a device length of 2839 μm. In addition, it is expected that over the 1.5 to 1.6-μm wavelength range, polarization conversion would be more than 99%.

Passive Polarization Converters Based on Photonic Crystal Fiber With L-Shaped Core Region

In this paper, novel designs of single and multiple sectioned passive polarization rotators (PRs) based on silica photonic crystal fiber (PCF) are studied and analyzed. The suggested PCF PRs have an L-shaped core region which offers nearly 100% polarization conversion ratio. The simulation results are obtained using the full vectorial finite difference method along with the full vectorial finite difference beam propagation method. The influence of the different waveguide parameters and operating wavelength on the PRs performances are investigated in order to obtain optimum PR designs. The single and multiple sectioned PCF PRs offer nearly 100% polarization conversion ratio with device lengths of 1743 μ m and 1265 μ m, respectively.

Design of passive polarization rotator based on silica photonic crystal fiber

We propose and analyze a novel (to the best of our knowledge) design of a polarization rotator (PR) based on silica photonic crystal fiber. The proposed design has a rectangular core region with a slanted sidewall. The simulation results are obtained using the full vectorial finite difference method as well as the full vectorial finite difference beam propagation method. The numerical results reveal that the suggested PR can provide a nearly 100% polarization conversion ratio with a device length of 3102 μm.

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.

Genetic algorithm and finite-element design of short single-section passive polarization converter

A very short passive polarization rotator is proposed, consisting of a single-section asymmetric waveguide. The use of a genetic algorithm together with the finite-element method was crucial to achieve a structure with 99% polarization conversion and a length of 90 μm. This optimum structure exhibits a low total insertion loss: 1.16 dB.

Full vectorial finite element modeling of novel polarization rotators

In this paper, the numerically efficient finite element based full vectorial modal and propagation approaches are used in order to analyze and design single and multiple sectioned passive polarization rotators (PRs). The effects of different waveguide parameters, such as the waveguide width, etching depth, sidewall slant angle and refractive index contrast on the PR performance in terms of polarization conversion efficiency, section length and losses are investigated in detail in order to obtain optimum PR designs. Moreover, a thorough sensitivity study of the fabrication tolerances and the operating wavelength on the performance of the PRs has also been carried out.

Polarization-selective switching in holographically formed polymer dispersed liquid crystals

We have developed an optical stack of holographically formed polymer dispersed liquid-crystal (H-PDLC) devices that is fully operational with nonpolarized light sources. The device consists of two H-PDLC transmission gratings separated by a passive polarization rotator that can output a diffracted s-polarized, p-polarized, or s- and p-polarized beam simultaneously.

Fabrication tolerance study of a compact passive polarization rotator

In this paper, the expected performance of a compact low-loss passive polarization rotator is reported by using rigorous numerical approaches. The effects of waveguide width, slant angle, etch depth, and refractive index variations during its fabrication on the overall polarization conversion and polarization crosstalk are reported. It is also expected that over the 1.53to 1.61-/spl mu/m wavelength range, polarization conversion would be more than 99% and polarization crosstalk would be better than -20 dB.

Design and characterization of compact single-section passive polarization rotator

In this paper an improved design for a short and low-loss polarization rotator is proposed, consisting of a single-section asymmetrical waveguide butt-coupled between two standard rib waveguides. At a wavelength of 1.55 /spl mu/m, nearly 100% polarization conversion ratio is obtained, with a relatively short (320 /spl mu/m) device length and an extremely low 0.5 dB total insertion loss. The simulation results are obtained using the full vectorial finite-element-based beam propagation, the junction analysis, and the modal solution approaches.

Passive Polarization Rotators for Nonlinear Optical Devices

AbstractInitial experiments of a passive polymeric TE-to-TM polarization converter that utilizes laterally offset upper and lower poling electrodes to induce a 45° optical axis in the core of a nonlinear optical polymer waveguide are reported. By optimizing the device length, we have demonstrated polarization conversion efficiencies greater than 95% in devices as short as 240 um with negligible insertion loss.