Elimination of cross-talk in waveguide intersections of triangular lattice photonic crystals

Soon-Hong Kwon,Martin Kamp,Yong-Hee Lee,Alfred Forchel,Min-Kyo Seo

doi:10.1364/oe.16.011399

Abstract

We design an intersection for crossing waveguides in triangular lattice photonic crystals with cross-talk smaller than 10(-5). The cross-talk to the transverse waveguides is suppressed by symmetry mismatch between the cavity mode and the waveguide mode or by the mode-gap effect induced by air hole radius modulation of the waveguides. The transmission behavior of the crossing waveguides are illustrated by numerical simulations through finite difference time domain method.

Highlights

Owing to the ability of photonic crystals (PhCs) to manipulate photons in the wavelengthdimension, various PhC devices such as microresonators [1,2,3], waveguides [4,5], channeldrop filters [6,7,8,9,10], and optical switches [11,12] have been developed as building blocks for integrated photonic systems
We design an intersection for crossing waveguides in triangular lattice photonic crystals with cross-talk smaller than 10-5
The cross-talk to the transverse waveguides is suppressed by symmetry mismatch between the cavity mode and the waveguide mode or by the mode-gap effect induced by air hole radius modulation of the waveguides

Summary

Introduction

Owing to the ability of photonic crystals (PhCs) to manipulate photons in the wavelengthdimension, various PhC devices such as microresonators [1,2,3], waveguides [4,5], channeldrop filters [6,7,8,9,10], and optical switches [11,12] have been developed as building blocks for integrated photonic systems. It was reported that the excited mode from the input waveguides can be prevented by symmetry mismatch from decaying into the transverse ports, which was illustrated in a square lattice PhC [13]. Most of the two-dimensional (2D) PhC devices have been demonstrated in the triangular lattice because of the wider photonic bandgap (PBG) than in the square lattice, such a symmetry-based method can not be directly applied in the triangular lattice since the waveguides cross each other with 60 or 120 degrees and the cavity has C6v symmetry [14]. We propose a new design of an intersection for crossing waveguides without cross-talk in triangular lattice PhCs by combing both: the effects of the symmetry mismatch and the modegap, which can be generally applied to any waveguide-cavity coupled system.

Symmetries of quadrupole modes in a single cell cavity

Mode-gap of waveguides with different radii of air holes

Conclusion