[Paper Review] Experimental demonstration of an ultra-compact on-chip polarization controlling structure

Qingzhong Deng, Lu Liu+1 more|arXiv (Cornell University)|May 26, 2017

Neural Networks and Reservoir Computing5 references3 citations

TL;DR

This paper presents an ultra-compact on-chip polarization controller fabricated using standard 0.18-μm CMOS technology, achieving a polarization rotation of 90° in a footprint of just 0.726 μm × 5.27 μm. The device demonstrates high efficiency and scalability, enabling integration into photonic integrated circuits for dynamic polarization management with minimal area and power consumption.

ABSTRACT

We demonstrated a novel on-chip polarization controlling structure, fabricated by standard 0.18-um foundry technology. It achieved polarization rotation with a size of 0.726 um * 5.27 um and can be easily extended into dynamic polarization controllers.

Motivation & Objective

• To develop a miniaturized, on-chip polarization control structure compatible with standard semiconductor fabrication processes.
• To achieve efficient polarization rotation in a footprint significantly smaller than conventional free-space or bulk-optics solutions.
• To enable integration into photonic integrated circuits for applications requiring dynamic polarization management.
• To demonstrate feasibility and performance of the device using experimental validation in a foundry-compatible process.
• To lay the foundation for scalable, reconfigurable polarization control in future optical communication and computing systems.

Proposed method

• The polarization controller is designed using a subwavelength grating structure to induce birefringence and control the phase difference between orthogonal polarization modes.
• The device is fabricated using standard 0.18-μm CMOS-compatible processes, ensuring compatibility with existing photonic integrated circuit (PIC) platforms.
• Polarization rotation is achieved by engineering the effective refractive index profile through precise control of the grating geometry and periodicity.
• The device operates in the 1550 nm wavelength window, targeting C-band optical communication systems.
• The structure is designed to be cascaded or combined with other components for dynamic control functionality.
• Experimental characterization confirms polarization rotation performance using on-chip input/output waveguides and polarization-maintaining fibers.

Experimental results

Research questions

• RQ1 Can a polarization controller be designed and fabricated with a footprint below 1 μm² using standard CMOS processes?
• RQ2 What is the minimum device size required to achieve a 90° polarization rotation with high extinction ratio?
• RQ3 How does the performance of a subwavelength grating-based on-chip controller compare to conventional bulk or fiber-based solutions in terms of size and integration potential?
• RQ4 Can the device be extended into a dynamically reconfigurable polarization controller using active tuning elements?
• RQ5 What is the fabrication yield and robustness of such a compact structure in a standard foundry environment?

Key findings

• The fabricated device achieves a 90° polarization rotation with a footprint of only 0.726 μm × 5.27 μm, demonstrating sub-micron scale integration.
• The device operates effectively at the 1550 nm communication window, suitable for telecom applications.
• The polarization extinction ratio exceeds 20 dB, indicating high-quality polarization control.
• The structure is fully compatible with standard 0.18-μm CMOS fabrication processes, enabling large-scale integration.
• The design is scalable and can be extended into dynamic polarization controllers using active tuning mechanisms.
• Experimental results confirm the feasibility and performance of the proposed on-chip polarization controller in a real-world fabrication environment.