Micro Optical Components Fabrication by Laser Processing

Micro-optical components – like lenses, diffraction gratings, and photon sieves find many applications in optoelectronics devices such as display, scanners, imaging, and information storage. In this thesis, we describe the design, fabrication and characterization of the micro-optical components fabricated by laser processing method and using Zemax ray-tracing simulations, measurement of optical beam profile, surface morphology and optical transmission efficiencies.

Plano-concave micro lenses were fabricated using a 355 nm wavelength pulsed picosecond laser and CW CO2 lasers. The plano-convex lenses were fabricated by picosecond laser micro patterning followed by reshaping the patterned area using a CO2 laser melting. Plano-concave, plano-convex and cylindrical lenses were fabricated, and their performance in terms of light transmission efficiency, focal length, and beam divergences was characterized. A comparative study of the micro lenses fabricated by different technique was also carried out.

Diffraction gratings were micro machined of about 10 μm period in sapphire using a 355 nm wavelength nanosecond pulsed laser and high NA objective lens. The fabricated gratings were characterized in terms of diffracted beam profile, optical diffraction efficiency, surface morphology, and depth profile of gratings when the laser was focused on the top surface and also at the bottom surface of the sapphire sample. We also demonstrate the fabrication of a photon sieve, a planar diffractive optical lens based on diffraction phenomenon on a sapphire substrate for operation at 632 nm wavelength, and characterized the output beam profile of the focused beam.

Microscale (200μm) glass sealing was achieved using a 1070 nm wavelength CW laser by melting glass frit between glass plates at room temperature. The optical transmission and strength of the glass bond was investigated and compared to the conventional furnace glass sealing process.

In summary, improved methods to fabricate micro-optical components with low cost, large area, and low process times have been demonstrated with laser processing.