3-D interference lithography for photonic crystal structure fabrication

The periodic alteration of dielectric constant throughout the structure leads towards periodic slow propagation of light and such modulation of light procedures photonic bandgap material known as a photonic crystal. It serves vast applications in light manipulation and led to different applications like wideband tuneable filters, optical switches, logic gates, compact Nano-lasers, light trapping & extraction, solar photovoltaics, and enhanced efficiency for LEDs display devices. The characteristics key parameter here is the period whose values compared to the wavelength of incident light entertain many optical phenomena. Here in our PRL lab, we are focusing on the fabrication of photonic crystal (period comparable to the wavelength of EMW) and metamaterial structure (period << wavelength) through the laser interference lithography method. Laser interference lithography offers a single shot, large area, and ease of complex structure formation compared to top-down and bottom-up existing techniques like e beam lithography, focused Ion beam lithography, and glancing angle deposition.

In our lab, we have set up laser interference lithography techniques to fabricate 1D, 2D, and 3D photonic crystal and Photonic metamaterial structures. The entire method is due to interference pattern form between the beams recorded on a photoresist (photosensitive material that degrades or becomes hard on exposure). Thus, recorded pattern assists as the mask can finally be etched or thermally evaporated as per requirement. The LIL technique can be further categorized for 1D,2D, and 3D structure formation. Lloyd's setup is used for fabricating a 1D grating structure. For different 2D periodic systems, a multi-exposure configuration has been used to rotate sample or recording medium and successfully designed 14 Bravais lattice formations. Lloyd's setup is further modified by establishing two mirror mounts for enlarging the exposure area for 2D hexagonal arranged dot patterning. We have designed and fabricated complex 2D and 3D photonic metamaterial structures with multiple beam phase-controlled laser interference lithography (PCLIL) with the aid of a spatial light modulator (SLM). The electronically addressed phase through SLM gets interfere at the sample plane. So, by designing an appropriate phase pattern, one can collect the diffracted orders coming from SLM and make them interfere at the recording plane. Different metamaterial basis structures like a hexagonally packed rectangular array, U shaped, L shaped, and C shaped triangular basis within a hexagonal lattice, dual lattice, quasi-periodic lattice, star-shaped periodic patterns have been transferred to photoresist successfully. The bio- mimic Photonic crystal show possibilities in realizing tuneable structural colours, chemical sensors, artificial antireflection coatings (ARCs), etc. The moth-eye structure has been fabricated in the large area using 4+4 double cone geometry with different tilt angles for 4 and 4 per umbrella beams configuration.

PCIL is further explored towards the optical realization of tuneable complex photonic chiral lattices and 3D chiral structures. The Chiral structure shows cross-coupling of the electric and magnetic fields when interacting with the electromagnetic light. It brings optical dichroism towards the circularly polarised light, resulting in different absorption with the left and right-hand circular polarised light. 3D chiral structures such as helix, double helix, and woodpile structure using Umbrella beam geometry with 6+1, 6+6 (double cone geometry), and 3+3 (double cone geometry) beam interference, respectively been fabricated following the umbrella geometry. Through the use of reconfigurable phase patterns, one can simulate as well as experimentally visualize these complex chiral helical structures with the generation of both periodic right-handed (RH) and left-handed (LH) lattices. Photonic woodpile chiral structure has also been fabricated using 4+1 beam geometry that exhibits an omnidirectional RGB filter application. In our lab, the fabricated periodic structures play significance in casting off the different ongoing working areas like guided-mode resonance (GMR) based Biosensors and filters, studies of chiral properties of metamaterial, and imaging.

Publications

Pandey, S., Samanta, K., Ahuja, J., Joseph, S., & Joseph, J. (2024). Designing a square periodic racemic helix photonic metamaterial using phase-controlled interference lithography for tailored chiral response. Optics & Laser Technology, 172, 110489.

S. Sarkar, K. Samanta, and J. Joseph, "Sub-micron Array of Split-Ring Resonators Through Polarization Incorporated Phase-Controlled Interference Lithography", in Frontiers in Optics / Laser Science, B. Lee, C. Mazzali, K. Corwin, and R. Jason Jones, eds., OSA Technical Digest (Optical Society of America, 2020).

Swagato Sarkar and Joby Joseph "Phase controlled interference lithography: a dynamic tool for large-area fabrication of nano-photonic structures", Proc. SPIE 11402, Three-Dimensional Imaging, Visualization, and Display 2020, 114020B (2020).

S. Sarkar, S. Behera, and J. Joseph, "Fabrication of Sub-micrometer Helical Photonic Structures using Top-Cut Hexa-Prism", in 13th International Conference on Fiber Optics and Photonics, OSA Technical Digest (online) (Optical Society of America, 2016), paper W4E.3.

Jolly Xavier, Sunil Vyas, P. Senthilkumaran, C. Denz, and Joby Joseph, "Sculptured 3D twister superlattices embedded with tunable vortex spirals", Opt. Lett. 36 (2011) 3512-3514.

Xavier, J., and Joseph, J., "Tunable complex photonic chiral lattices by reconfigurable optical phase engineering," Opt. Lett. 36, 403-405 (2011).

Xavier, J., Boguslawski, M., Rose, P., Joseph, J., and Denz, C., "Reconfigurable Optically Induced Quasicrystallographic Three-Dimensional Complex Nonlinear Photonic Lattice Structures," Adv. Mater. 22, 356- 360 (2010).

Xavier, J., Rose, P., Terhalle, B., Joseph, J., and Denz, C., "Three-dimensional optically induced reconfigurable photorefractive nonlinear photonic lattices," Opt. Lett. 34, 2625- 2627 (2009).

Dwivedi, A., Xavier, J., Joseph, J., and Singh, K., "Formation of all fourteen Bravais lattices of three-dimensional photonic crystal structures by a dual beam multiple-exposure holographic technique," Appl. Opt. 47, 1973-1980 (2008).