# Reduced Symmetric 2D Photonic Crystal Cavity with Wavelength Tunability

## TL;DR

This paper introduces a tunable 2D photonic crystal microcavity with adjustable modes and high quality factors, validated through numerical simulations and microwave experiments, demonstrating potential for advanced photonic applications.

## Contribution

It presents a novel design for a symmetric 2D photonic crystal cavity with wavelength tunability via rotational defect modifications, supported by comprehensive numerical and experimental validation.

## Key findings

- Frequency tuning achieved through defect rotation.
- Quality factor reaches up to 10^8 in simulations.
- Good agreement between numerical and experimental results.

## Abstract

In this paper, we propose a microcavity supported by a designed photonic crystal structure (PhC) that supplies both tunability of cavity modes and quality factor of cavity. Low symmetric defect region provides a trigger effect for the frequency shifting by means of rotational manipulation of small symmetry elements. Deviation of effective filling ratio as a result of rotational modification within the defect region results in the emanation of cavity modes at different frequencies. Here, we numerically demonstrate the frequency shifting for each obtained mode with respect to defect region architecture. In addition to wavelength tunability, quality factor, mode volume, and Purcell factors are analyzed for the slightly modified structures. Also, electric field distributions of each mode that emerge at distinct frequencies have been also studied at adjusted frequency modes which are observed for all rotational modification scenarios as $\theta_{rot} =[0^\circ,15^\circ,30^\circ, 40^\circ] $. After the investigations in 2D of silicon material ($\epsilon_r=12$), 3D simulations are performed and the collected data is used for the stacking approximation of 3D structures to get the 2D, thus the cross-checking of the quality factor that acquired from the 2D simulation can be executed by comparison with 3D. Limited 3D results are projected to approximate 2D ones step by step and get an exponential trend which reaches in the limit to the $10^8$ value for Q-factor. Besides, 2D and 3D simulations of alumina ($\epsilon_r=9.61$) in terms of mode analysis and quality factor have been repeated considering the microwave experiments. Therefore, experimental analysis is compared with the numerical results and good agreement between the two is found.

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Source: https://tomesphere.com/paper/1902.02590