Soft Matter Macro and Micro-Photonics workshop

Microscale generation and control of nanosecond light by light in a photonic soft matter

Igor Muševič 1,2,*
1 Jožef Stefan Institute, Ljubljana, Slovenia

2 Faculty of Mathematics and Physics, University of Ljubljana, Slovenia
* igor.musevic@ijs.si

The all-optical control of light has been explored in hard matter, but to control light by light in soft matter is a major experimental and conceptual challenge that remains largely unexplored. First, we demonstrate a soft-matter photonic platform that integrates tuneable liquid-crystal micro-lasers and 3D laser micro-printed polymer waveguides [1]. We propose and verify experimentally and numerically that nanosecond light pulses can be controlled by light pulses using resonant stimulated-emission depletion in liquid-crystal optical cavities that act as nanosecond optical switches. This concept of resonant stimulated-emission depletion in a resonant micro-cavity is several orders more efficient than a single-pass STED method known from super-resolution imaging. In a second example, light-by-light control is realized in a micrometre-diameter droplet of fluorescent-dye-doped nematic liquid crystal that is submersed in an aqueous solution. Light is coupled in and out of the droplet via laser-printed optical waveguides that touch the surface of the droplet. While the Whispering Gallery Mode lasing is initiated in the droplet, it can be suppressed efficiently on a nanosecond scale by another, red-shifted light pulse before the lasing takes place [2]. Current developments will be discussed, including the alignment of LCs on 3D-printed vertical surfaces [3], the design and operation of CLC band-edge and defect-mode micro-lasers that bypass the problem of CLC laser bleaching and light-switching experiments in 3D Bragg-onion CLC micro-droplets.

[1] M. Vellaichamy, U. Jagodič, J. Pišljar et al. Microscale generation and control of nanosecond light by light in a liquid crystal. Nat. Photon. 19, 758–766 (2025).

[2] V. Sharma, J. Zaplotnik, M. Mur et al. Light control of lasing from liquid-crystal micro-droplet light switch, Adv. Photon. 8(2) 026009( 2026).

[3] U. Jagodič, J. Pišljar, A. Jelen et al. Three-Dimensional Planar Alignment of Nematic Liquid Crystal by Direct Laser Writing of Nanogratings. ACS Photonics 12 (11), 5970 -5977(2025).