An international research team at Nanyang Technological University has demonstrated the concept of a switchable microlaser controlled by the organic biomolecule DNA hybridization process. The study could lead to the development of programmable photonic devices at the subnanoscale. Optical switching is typically achieved through complex device fabrication, or through physical approaches, such as modifying the structure or refractive index of the lasing cavities. In contrast to artificially designed interfaces, stimuli responsive biointerfaces take advantage of biological system and biorecognition, ensuring that a higher level of functionality can be realized at the nanoscale. Professor Yu-Cheng Chen, who is corresponding author on the study, and his team incorporated DNA in a Fabry-Pérot optical microcavity. DNA, known for its controllable synthesis and specificity of base-pair interactions, is self-assembling and highly programmable, which offers versatility in constructing biointerfaces and tailoring optical responses for control. The optical microcavity consists of two dielectric mirrors in which dye-doped liquid crystals were introduced as optical gain to enhance the response of DNA binding events. The strong light-matter interaction induced by the microcavity enabled the amplification of subtle changes within the cavity and liquid crystal matrices. When the single-stranded DNA was adsorbed on the cationic monolayer of the matrix, the liquid crystal molecule changed from a homeotropic to planar alignment. That change in orientation resulted in a blue-shift of lasing wavelength with pronounced signal amplification. Upon binding with its complementary part through the DNA hybridization process, the lasing wavelength can be reverted. “We used this special DNA-liquid crystal interaction as the switching power to alter the liquid crystal’s orientation in the Fabry-Pérot microcavity so that laser emission switching among different wavelengths was achieved,” Chen said. By exploiting the complexity and self-recognition of DNA sequences, the scientists could fully manipulate and program laser light in the system. Beyond photonic device programing, the work could have applications in information encoding and data storage using laser light. “The significance of this study is to introduce the concept of using organic biomolecules to switch coherent light sources at different wavelengths. It represents a milestone in achieving biological-controlled laser,” Chen said. The research was published in ACS Nano (www.doi.org/10.1021/acsnano.0c08219).