Implementation of on-chip multi-channel focusing wavelength demultiplexer with regularized digital metamaterials

Abstract

Adiabatic waveguide taper and on-chip wavelength demultiplexer are the key components of photonic integrated circuits. However, these two kinds of devices which designed by traditional semi-analytic methods or brute-force search methods usually have large size. Here, based on regularized digital metamaterials, we have designed, fabricated and characterized a twochannel focused wavelength demultiplexer with a footprint of 2.4 × 10 μm 2 . The designed demultiplexer can directly connect to a grating coupler under the absence of an adiabatic waveguide taper. The objective first method and modified steepest descent method are used to design the demultiplexer which splits 1520 nm and 1580 nm light from a 10-μm-wide input waveguide into two 0.48-μm-wide output waveguides. Experimental results show that the insertion loss of the upper (lower) channel of the demultiplexer is -1.77 dB (-2.10 dB) and the crosstalk is -25.17 dB (-12.14 dB). Besides, the simulation results indicate that the fabrication tolerance of our devices can reach ±20 nm in etching depth and ±10 nm in plane size changing. Benefit From the extensibility of our design method, we can design other types of ultra-compact 'focused' devices, like mode splitters, mode converters and power splitters, and we can also design devices with more complicated functionalities, for example, we have designed a three-channel focused wavelength demultiplexer.

Inverse design of higher-order photonic topological insulators

“…Topology optimization employs a robust numerical algorithm to seek the layout of materials within the design domain, so as to minimize or maximize the defined objective function [36]. Topology optimization has been proven to be an efficient and effective tool for the design of PCs [37][38][39][40][41][42][43][44][45][46]. Here, we will extend topology optimization to design the unit cell of nontrivial and trivial PCs for SPTIs.…”

Numerical and experimental demonstration of inverse designed low-index polarization-insensitive wavelength demultiplexer

“…By contrast, conveying different wavelengths to specific waveguides can be considered a great opportunity to redesign new compact and efficient optical communication systems. In this direction, in recent decades, WDMs have attracted significant attention with state-of-the-art nanophotonic design tools and approaches [5][6][7][8][9][10][11][12][13][14] . Optically conveying a light source with minimum loss is crucial in the design of efficient and integrable WDMs.…”

“…By contrast, the second approach is based on advanced algorithms and combined simulations to seek a solution that minimizes (or maximizes) a single objective or multi-objective related to the desired nanophotonics functionalities, also known as an "Inverse Design." Because non-heuristic methods provide an effective optimization of all structural parameters that are impossible with conventional methods, they have been used effectively in the design of nanophotonic devices [11][12][13][14][19][20][21][22][23][24][25][26][27][28][29][30][31] . One example of the first method is integrating a Mach-Zehnder interferometer (MZIs) and Si 3 N 4 on a silicon platform for the design of an on-chip polarization-insensitive WDM (PIWDM) device with a footprint of only 2.5 mm × 0.9 mm 10 .…”

Inverse-designed arbitrary-input and ultra-compact 1 × N power splitters based on high symmetric structure

“…At the same time, an accumulating number of advanced optimization methods have been applied to design complex nanophotonic devices, such as direct-binary-search (DBS) algorithm 2,4,5,9,13,18,21,27,30,34,35 , genetic algorithm 37,38 , objective-first design [39][40][41] , and fabrication-constrained nanophotonic inverse design 42 . Compared with traditional approaches which strongly depend on analytic theory and intuition of researchers, the biggest virtue of advanced optimization methods is that they can take full…”