Continuously tuneable single electrode pair liquid crystal optical vortex generators

In this work, we demonstrate the use of two-photon polymerization direct laser writing in the production of continuously tuneable optical vortex beam (OV) generators in a liquid crystal (LC) layer sandwiched between glass substrates. Results are presented that show how an OV generator can be inscribed into a 20 mu m-thick LC layer and how the order of the OV beam can be tuned with the application of a voltage. Importantly, only a single pair of electrodes is needed to tune the order of the vortex as the required phase profile is generated through the 3D structuring of the polymer network using the laser writing process. Following the design and fabrication of the LC-OV generator, a Mach-Zehnder interferometer is subsequently employed, in conjunction with polarizing optical microscopy, to characterize the devices to confirm the generation of OVs of different orders and to determine the corresponding chirality. The paper concludes by considering whether these LC-OV generators can function at a range of different operation wavelengths. Such devices would be of potential importance in applications ranging from optical communications to quantum physics.