Switching of lasing direction in reconfigurable chiral photonic crystals

Abstract

In recent years, the development of lasers using photonic crystals as resonant cavities has emerged and continued to grow. These photonic crystal lasers offer the advantages of reduced threshold levels and compact dimensions. Chiral liquid crystals (CLCs) are self-assembled one-dimensional photonic crystals that enable a wide range of photonic crystal lasers to exhibit broad wavelength tuning capabilities. Our research exploits the uniform standing helix (USH) and uniform lying helix (ULH) states of CLCs as resonant cavities; therefore, the direction of laser emission of CLC lasers can be changed by switching between USH and ULH states. Both USH and ULH lasers in CLCs also exhibit wavelength tuning. The USH laser induces a blue shift in the laser wavelength by dielectric heating, while the ULH laser achieves a redshift of the laser wavelength by applying a vertical electric field to lengthen the helical pitch. Such a reconfigurable chiral photonic crystal laser based on the CLCs provides bidirectional switching of the laser direction while maintaining the ability to tune the wavelength, so it has the potential for use in photonic applications.