Unidirectional Light Emission In Pt-Symmetric Microring Lasers

Abstract

The synergetic use of gain and loss in parity-time symmetric coupled resonators has been shown to lead to single-mode lasing operation. However, at the corresponding resonance frequency, an ideal ring resonator tends to support two degenerate eigenmodes, traveling along the cavity in opposite directions. Here, we show a unidirectional single-moded parity-time symmetric laser by incorporating active S-bend structures with opposite chirality in the respective ring resonators. Such chiral elements break the rotation symmetry of the ring cavities by providing an asymmetric coupling between the clockwise (CW) and the counterclockwise (CCW) traveling modes, hence creating a new type of exceptional point. This property, consequently, leads to the suppression of one of the counter-propagating modes. In this paper, we first measure the extinction ratio between the CW and CCW modes in a single ring resonator in the presence of an S-bend waveguide. We then experimentally investigate the unidirectional emission in PT-symmetric systems below and above the exceptional point. Finally, unidirectional emission will be shown in systems of two S-bend ring resonators coupled through a link structure.

Publication Date

10-15-2018

Publication Title

Optics Express

Volume

26

Issue

21

Number of Pages

27153-27160

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1364/OE.26.027153

Socpus ID

85055025043 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85055025043

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