High-g-factor phase-matched second harmonic generation near photonic bandgap of polar cholesteric liquid crystals

ABSTRACT

The discovery of polar liquid crystals, such as ferroelectric and helielectric liquid crystals, provides fascinating platforms for designing and modulating polarisation structures that generate strong second harmonic generation. Here, we report that the helielectric nematics, i.e. the polar cholesteric liquid crystals, realise an unprecedented phase-matching condition for the second harmonic generation in the photonic bandgap. Like the circular dichroism in the linear optical regime, the phase-matched second harmonic generation generated in a helielectric nematic medium exhibits a circular polarisation selectivity in the nonlinear optical regime. The maximum g-factor for the second harmonic generation is over ~ 1.95.

GRAPHICAL ABSTRACT

KEYWORDS:

• Nonlinear optical phase matching
• second harmonic generation
• photonic bandgap
• helielectric nematic liquid crystal
• g-factor

Acknowledgments

S.A. and M.H. acknowledge the National Key Research and Development Program of China (No. 2022YFA1405000), the Recruitment Program of Guangdong (No. 2016ZT06C322), and the 111 Project (No. B18023). S.A. acknowledges the supports from the Research Fund for International Excellent Young Scientists (RFIS-II; No. 1231101194), the International Science and Technology Cooperation Program of Guangdong province (No. 2022A0505050006), General Program of Guangdong Natural Science Foundation (No. 2022A1515011026) and the Fundamental Research Funds for the Central University (No. 2022ZYGXZR001). M.H. acknowledges the support from the National Natural Science Foundation of China (NSFC No. 52273292).

Data Availability Statement

All data that support this study are available in the Manuscript and Supplementary Information. Additional information is available from the corresponding author upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/02678292.2024.2307447

Additional information

Funding

This work was supported by the Fundamental Research Funds for Central Universities of the Central South University [2022ZYGXZR001]; National Key Research and Development Program of China [2022YFA1405000]; National Natural Science Foundation of China [1231101194]; Natural Science Foundation of Guangdong Province [2022A0505050006].