Ultralow Loss and High Extinction Ratio TM-Pass Polarizer in Silicon Photonics

Nikhil Dhingra,Francesco Dell Olio

doi:10.1109/jphot.2020.3032847

Nikhil Dhingra, Francesco Dell Olio

Open Access

https://doi.org/10.1109/jphot.2020.3032847

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Abstract

TM-pass polarizers are pivotal components of photonic integrated circuits (PICs), especially those intended for biosensing applications. In the literature, several silicon TM-pass polarizers have been proposed, designed and experimentally demonstrated, but their insertion loss is not compatible with the current trend of silicon photonics aimed at exponentially increasing the component density within PICs. Herein, we propose and design a TM-pass polarizer whose insertion loss is carefully minimized to 0.05 dB at wavelength 1.55 μm by utilizing a combination of an asymmetric directional coupler and a mode evolution section. The adoption of appropriate technical solutions makes this record insertion loss value compatible with a high extinction ratio equal to 38 dB. With a device footprint of only 2.5 × 20 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the design exhibits an insertion loss less than 1.7 dB and extinction ratio better than 30 dB over a large bandwidth of 200 nm. The design assumes the constraints of a typical silicon photonics open-access technological process and a standard 220 nm silicon-on-insulator (SOI) wafer. A very low sensitivity of the achieved performance to reasonable fabrication inaccuracies is demonstrated, with a worst-case insertion loss of only 0.32 dB at wavelength 1.55 μm.

Highlights

In the last two decades, there has been a game-changing transformation of integrated microphotonics
By using the finite element method (FEM) [32] in Fimmwave, we carry out the modal analysis of the two waveguides forming the coupler
The inbuilt adaptive mesh algorithm generates the finite element mesh, which resolves the device cross-section very accurately resulting in highly accurate modal solutions

Summary

Introduction

In the last two decades, there has been a game-changing transformation of integrated microphotonics. Several SOI TM-pass polarizers have been proposed and experimentally demonstrated in the literature They are based on one-dimensional or two-dimensional photonic crystal waveguides [13]–[15], a silicon strip waveguide embedding a graphene/Si3N4/graphene multilayer [16], photonic/plasmonic hybrid grating waveguides [17]–[19], a silicon wire coupled to a highly doped silicon waveguide [20], a silicon wire with a VO2 film on the vertical sidewalls [21], subwavelength grating waveguides [22]–[25], a waveguiding structure with two tapered waveguides sandwiching a narrow waveguide only supporting TM mode propagation [25], plasmonic bends [26], and hyperuniform disordered structures [27]–[30].

Device Structure and Operating Principle

Results and Discussion

Conclusion