Dissertation Defense: Femtosecond Laser Written Volumetric Diffractive Optical Elements And Their Applications
CREOL 102 November 5, 2009
03:30 PM - 05:30 PM
Announcing the Final Examination of Jiyeon Choi for the degree of Doctor of Philosophy in Optics.
Since the first demonstration of femtosecond laser written waveguides in 1996, femtosecond laser direct writing (FLDW) has been providing a versatile means to fabricate embedded 3D microstructures in transparent materials. The key mechanisms are nonlinear absorption proceseses that occur when a laser beam is tightly focused into a material and the intensity of the focused beam is over the threshold for photo-induced structural modification. One of the most useful features that can be exploited in fabricating photonic structures is refractive index change which results from the localized energy deposition. The laser processing system for FLDW can be realized as a compact, desktop station, implemented by a laser source, a 3D stage and focusing optics. Thus, FLDW can be readily adopted for the fabrication of the photonic devices. For instance, it has been widely employed to various areas of photonic device fabrication such as active and passive waveguides, couplers, gratings, opto-fluidics and similar applications.
This dissertation describes the use of FLDW towards the fabrication of custom designed diffractive optical elements (DOE's). These are important micro-optical elements that are building blocks in integrated optical devices including on-chip sensors and systems. The fabrication and characterization of laser direct written DOEs in different glass materials is investigated. The design and performance of a range of DOE's is described, especially, laser-written embedded Fresnel zone plates and linear gratings. Their diffractive efficiency as functions of the fabrication parameters is discussed and the fabrication process optimized. The potential of the micro-DOEs and their integration shown in this dissertation will impact on the fabricaiton of future on-chip devices involving customized DOEs that will serve great flexibility and multi-functional capability on sensing, imaging and beam shaping.
Graduate Students
Dissertation Defense: Femtosecond Laser Written Volumetric Diffractive Optical Elements And Their Applications
