All passive photonic power divider with arbitrary split ratio

TL;DR

This paper presents an ultra-compact, nanostructure-based photonic power splitter capable of arbitrary split ratios, using a nonlinear search method to optimize a QR code-like design for efficient light distribution.

Contribution

It introduces a novel, highly functional nanostructure design for arbitrary split ratio power splitters in photonic circuits, optimized via a nonlinear fast search method.

Findings

Achieved 1x2 splitters with ratios 1:1, 1:2, 1:3

Demonstrated a 1x3 splitter with ratio 1:2:1

Device footprint is only 3.6um x 3.6um with ~80% efficiency over 30 nm

Abstract

Integrated optical power splitter is one of the fundamental building blocks in photonic integrated circuits (PIC). Conventional multimode interferometer based power splitter is widely used as it has reasonable footprint and is easy to fabricate. However, it is challenging to realize arbitrary split ratio especially for multi-outputs. In this work, an ultra-compact power splitter with a QR code-like nanostructure is designed by a nonlinear fast search method (FSM). The highly functional structure is composed of a number of freely designed square pixels with the size of 120nm x 120nm which could be either dielectric or air. The lightwaves are scattered by a number of etched squares with optimized locations and the scattered waves superimpose at the outputs with the desired power ratio. We demonstrate 1x2 splitters with 1:1, 1:2, 1:3 split ratios and a 1x3 splitter with the ratio of 1:2:1. The footprint for all the devices is only 3.6umx3.6 um. Well-controlled split ratios are measured for all the cases. The measured transmission efficiencies of all the splitters are close to 80% over 30 nm wavelength range.