Waveguide Polarization Splitter Research Articles

Polarization splitter based on a three waveguide directional coupler using quantum mechanical analogies

We propose a novel waveguide polarization splitter based on the optical analogue of two-photon Rabi oscillations and stimulated Raman adiabatic passage in a three waveguide directional coupler. Both these processes are borrowed from three level quantum mechanical atomic systems, in which an intermediate level is used to transfer the population from one state to another without any population occupation in the intermediate level. To show the practical feasibility of the device, simulations have been carried out on waveguides in lithium niobate and we show that two orthogonal polarizations can be separated at the output using the proposed three waveguide structures. We also show that the proposed structure is robust against changes in phase mismatch parameters, as well as wavelength of operation.

Ultracompact, broadband slot waveguide polarization splitter

In this letter, we demonstrate an ultracompact polarization splitter design leveraging the giant birefringence of silicon-on-insulator slot waveguides. The fabricated splitter device has a coupling length of only 13.6 μm, and shows average polarization extinction ratios of 21 dB and 17 dB for the TE and TM polarizations, respectively, over the entire C-band.

Design of miniaturized silicon wire and slot waveguide polarization splitter based on a resonant tunneling

We propose an ultra-small polarization splitter based on a resonant tunneling phenomenon. This polarization splitter consists of two identical horizontally oblong silicon wire waveguides separated by a vertical slot waveguide. The structural parameters of the central resonant slot waveguide are designed to couple only the TM-like mode between the left and right side silicon wire waveguides. Results from numerical simulation with the full-vectorial beam propagation method show that a 16-mum-long polarization splitter with extinction ratio better than -20 dB on the entire C-band is achieved.

Compact silicon slot waveguide polarization splitter

A compact slot waveguide polarization splitter based on the silicon (Si) material system is proposed and analyzed. The slot waveguide structure introduces significant beat-length differences for transverse electric and transverse magnetic polarizations at operation wavelength of 1.55 µm. The special self-imaging design with limited modes and weak second-mode excitation shortens the device length to <50 µm, while still delivering good performance. The polarization extinction ratio is 13 dB, and the excess loss is only 0.3 dB. The splitter also has a relaxed length tolerance of 550 nm. These attributes make it an excellent candidate for polarization diversity circuits and compact electronic-photonic integrated circuits.

Coupled Waveguide Polarization Splitter With Slightly Different Core Widths

A coupler-type transverse electric/transverse magnetic (TE/TM) polarization splitter, in which a metal-loaded core is slightly widened, is analyzed using the three-dimensional beam-propagation method. Before analyzing the splitter with the slightly different core widths, the performance of a splitter with two identical cores is evaluated. The use of the two identical cores results in a high crosstalk and a low extinction ratio due to the phase mismatch between the waveguides with and without the metal for the TE mode. Therefore, the core width in the metal-loaded waveguide is slightly widened so as to restore the phase-matching condition. In contrast to the conventional splitter with the two identical cores, the present splitter is found to offer a low crosstalk of less than -30 dB and a high extinction ratio of more than 30 dB with a coupling efficiency of more than 97% at a wavelength of 1.55 mum. In addition, the wideband operation is demonstrated over a wavelength range of 1.50 to 1.61 mum.

Design and fabrication of a three-dimensional polymer optical waveguide polarization splitter

We present a design and fabrication of a three-dimensional polymer optical waveguide polarization splitter by taking into consideration of the induced birefringence effect of the polymer. We show that it is not possible to couple TM light from one waveguide to the other but evanescent coupling for TE light is possible. Hence the polarization splitter can be designed by considering TE mode coupling alone. This has an advantage of short interaction length of the device. Based on this consideration, we fabricated a polarization splitter with a TE extinction ratio of 15 dB and TM extinction ratio of 21 dB.

Polymeric waveguide polarization splitter with a buried birefringent polymer

A waveguide polarization splitter is demonstrated based on a low-loss polymer waveguide and a birefringent polyimide. Crosslinkable fluorinated polymers with an excellent stability and a low absorption loss are utilized for the device. The polyimide is buried under one branch of the Y-branch waveguide to enhance the birefringence between the TE and TM modes. By the adiabatic mode evolution, the TE mode is coupled to the branch with the polyimide strip, while the TM mode propagates through the other branch without the polyimide. For the device with a branch angle of 1/400 rad, we obtained a crosstalk less than -20 dB and a fiber-to-fiber insertion loss of 3.8 dB.

Radiatively coupled waveguide polarization splitter simulated by wave-matching-based coupled mode theory

Coupled mode theory is applied to an arrangement of three raised strip waveguides with a multimode central strip. We use semivectorial numerically computed modes of the three single isolated waveguides as a basis for propagating supermode analysis of the entire structure. The pronounced polarization dependence of the raised strip guides allows for the design of a conveniently short polarization splitter. We discuss design guidelines and estimate the fabrication tolerances. The accuracy of the coupled mode approach is assessed by comparison with rigorously computed supermodes for comparable two waveguide couplers. Both types of structures indicate the limits in the applicability of the coupled mode model.

Patterned birefringence by photoinduced depoling in electro-optic polymers and its application to a waveguide polarization splitter

Photobleaching by ultraviolet light at 410 nm wavelength of selected electro-optic poled polymers leads to birefringence which can be patterned on a submicron scale. Measurements at 1310 nm of the effect in a azo dye attached to poly(methylmethacrylate) is presented along with data showing the effect is not present is hardened cross linked polymer hosts. An integrated optic polarization splitter using the patterned birefringence has crosstalk at the transverse electric and transverse magnetic outputs of −23 and −27 dB, respectively, and excess loss 0.2 and 0.3 dB at 1310 nm.

A 1.3 mu m directional coupler polarization splitter by ion exchange

A glass waveguide polarization splitter for operation in the 1.3 mu m wavelength region is reported. The device, which has a symmetric directional coupler configuration, exploits the stress-induced birefringence in K/sup +/-Na/sup +/, ion-exchanged waveguides, giving rise to an adequate difference in the coupling lengths for the two polarizations. Starting from the measured potassium concentration (refractive index) profile of the structure and utilizing a combination of the multilayer stack theory and the effective-index method, the normal mode propagation constants and mode field profiles are calculated to determine the polarization splitting length and the extinction ratio, and the results are compared with the experimental data. It is shown that in a given coupler, the splitting occurs at several wavelengths in the 1.0-1.45 mu m range. A 25 mm-long coupler, fabricated by thermal diffusion of K/sup +/ ions in BK7 glass, exhibits an extinction ratio of 18.2 dB at 1.32 mu m, in excellent agreement with the simulation results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>