Rapid Fabrication of Glass Micro and Nanostructures via Laser-assisted Hot Embossing

The escalating demand for glass that exhibits various surface functions has encouraged efforts to develop more efficient and economical micro-/nano-patterning of glass substrates. We propose rapid hot embossing of glass micro-/nanostructures using an infrared transmissive mold assisted by CO2 laser irradiation. This resistless, etch-free technique utilizes the synergy of the silicon mold’s high transmittance and strong optical absorption of the glass at a 10.6-μm wavelength. Furthermore, this non-isothermal process requires preheating of the glass temperature below the glass transformation point (Tg) of the glass, eliminating the soaking time, and using a short contact pressing time and a lower pressing load to produce high-resolution space patterns. The method is capable of instantaneous high-resolution replication of various grating patterns from the nano- to microscale with a single laser scan. By controlling the scanning speed and ensuring sufficient pressure and heating depth on the glass surface, 250-nm to 50-μm line- widths and space patterns were embossed in a few seconds with excellent replication fidelity. The laser-assisted hot embossing methods developed in this study facil-itated high-throughput, energy-efficient, reproducible, and highly accurate micro-/nano-patterning of glass surfaces

Experimental and Numerical Simulation of Hot Embossing for Fabrication of Glass Microlens Array

In this work, a hot embossing process for replication of glass microlens array (MLA) on optical glass substrate is proposed. Both numerical simulation and experimental validation were employed to investigate the filling behavior of the glass material into the microstructure mold cavities. The finite element method (FEM) was carried out using Ansys software after the establishment of the model layout and boundary condition. For validation, the K-PG375 optical glass samples were pressed at a temperature above the glass transition temperature Tg, using a home-made hot embossing setup. Then, the correlation between two- dimensional (2D) FEM analysis and experiments were established, which provide a guideline for understanding of the glass filling behavior in the viscoelastic region. The replication quality of the embossed glass was confirmed using scanning electron microscopy (SEM) and atomic force microscope (AFM). Overall, the simulation result gave a very useful insight to predict the optimum processing condition for the thermal replication process primarily the temperature, pressure and holding time

Direct formation of periodic parallel microgrooves on glass using CO2 laser irradiation

Direct laser structuring is an interesting candidate for a rapid, large area and maskless method for formation of various microstructures pattern on glass substrates without the use of mold. Before the desired pattern shape and scale could be obtained, the relationship between the type of laser used, substrate material and laser irradiation parameters must be understood. In this work, direct formation of periodic parallel microgrooves on optical glass substrate using CO 2 laser irradiation is proposed. The effect of the laser scanning speed and initial glass temperature to the formation of periodic micro-grooves with various width and height was investigated. As a result, smooth and crack-free parallel microgrooves were successfully fabricated on KPSFN214-P optical glass with dimension ranging from 287μm to 456μm in width dimension and 4.2μm to 11.9μm in height

Laser-assisted thermal imprinting of glass guided mode resonant (GMR) optical filter

Laser-assisted thermal imprinting of glass nanostructures is demonstrated. Compare to the existing thermal imprinting, this method significantly reduced the contact imprinting time. The quality of the replicated glass nanostructures revealed by field emission scanning electron microscope ( SEM) and atomic force microscope ( AFM) exhibited a very smooth surface finish that closely matched the profile of the silicon mold. As proof-of-concept, the utility of laser-assisted, imprinted glass nanostructures as guided-mode resonant (GMR ) optical filter was evaluated. The peak spectral values obtained were satisfactory; which yielded an average FWHM and PWV of 4.6 nm and 691.39 nm respectively

Fabrication of glass microlens array using laser-assisted contactless hot embossing

Contactless hot embossing is one promising replication-based method for fabrication of high quality microlens array (MLA) with different sag height but suffers long thermal cycle. Herein, rapid fabrication of glass MLA using laser-assisted contactless hot embossing process is proposed.CO2 laser irradiation that passes through the micro holes mold promotes surface heating at the glass surface and speed up the formation of spherical MLA. The effect of the laser irradiation conditions, preheating temperature and holding time to the formation of MLA was discussed. Finally, high aspect ratio and smooth spherical glass MLA array with different sag height were successfully fabricated