Two-Photon Laser Lithography

Technology Description

Two-photon lithography (TPL) is an additive manufacturing method (laser 3D printing) that makes it possible to fabricate three-dimensional micro- and nanoscale structures with complex geometry. The method is based on the nonlinear optical effect of two-photon absorption, which initiates photopolymerization: the initially liquid photoresist solidifies strictly in the focal region of pulsed laser radiation. Subsequent movement of the focus within the material allows layer-by-layer formation of the desired structure. The key advantages of TPL — high spatial resolution (down to 100 nm), the ability to create complex 3D structures, and the functionalization of structures by doping the photoresist — make it a powerful tool for creating integrated photonic devices.

Research Focus in the Laboratory

The main research direction in our laboratory is aimed at the design, numerical modeling, and experimental fabrication of micro-optical devices for modern optical circuits and fundamental research. The work is carried out on a custom-built lithography setup with original software. This approach provides full control over the printing process and offers flexibility to modify the system for non-standard tasks, different types of substrates, and photoresists.

Key Achievements

To date, the following key results have been obtained within this area:

1. A method has been developed and active microstructures based on polymer doped with laser dye have been fabricated.
2. A full technological cycle for fabricating elevated waveguides above the substrate, including input-output radiation devices, has been implemented.
3. Optimization of input-outputs devices has been carried out through the use of second-order surfaces, which has improved coupling efficiency.

Current Tasks and Prospects

Current tasks of the direction include:

1. Developing a printing technology on silicon substrates for direct integration of polymer microstructures with semiconductor photonic chips.
2. Design, fabrication, and characterization of complex functional devices based on developed basic elements.
3. Exploring new ways of doping the photoresist to obtain devices with special properties.

Topics for Course and Diploma Projects

Students interested in research work are offered the following tasks:

1. Design and optimization of integrated photonics elements (waveguides, resonators, splitters) for two-photon lithography using the FDTD (Finite-Difference Time-Domain) method.
2. Modeling of resonance and mode characteristics of organic resonator structures of various geometries.
3. Fabrication of optical waveguide and resonator structures by TPL and subsequent study of their optical properties.