High-precision optical scanning in the near and far field
Vladislav Tkachuk is a PhD student in the department Optical Sciences. Promotor is prof.dr.ir. H.L. Offerhaus from the faculty of Science and Technology.
Optical devices are present in most of the devices that we use over the course of the day. Bright, sharp, and colorful displays produce realistic images. Sensors capture photographs and measure our bodies and surroundings. Optical data communication sends our information with almost unprecedented precision and ease, both from the TV set to the stereo system and between continents and satellites. All these applications utilize the unique properties of electromagnetic waves to shape, confine, and steer them to carry information. Major discoveries are bringing us closer to performing computations using only light. Some bulky optical devices are already replaced by compact, tightly-integrated photonic circuits. The systematic study of electromagnetic waves has taught us how to produce and receive them, and the creation of such devices has been made possible to observe and measure electromagnetic waves to ensure they behave as intended.
One can liken light propagation in an optical chip to cars driving in a city, where some roads are straight, others are curved, lanes split and merge, and there are roundabouts too. These cars, with all their different colors, navigate through this network of pathways to reach their destinations. The roads aren't perfect: sometimes cars slip off the track, crash into one another, or bounce back and forth before taking off the surface. The tool described in this work, a Near-field Scanning Optical Microscope (NSOM), acts like a helicopter that can hover above these roads and report on the road conditions at any given point. Like a helicopter, it has limitations; it cannot peek into tunnels where the roads are deep underground. Although it can't move as swiftly as these cars, it reveals the traces they leave in its field of view. This insight is ample for us to determine where the traffic originates, how well it sticks to the lanes, and which road sections are problematic.
This dissertation addresses one of the tools used for measuring the properties of light in optical devices. This instrument can locally probe the light to assess its phase and amplitude at precise locations, providing critical information. The primary focus of this work is to enhance the height feedback for the probe's positioning, develop a procedure for the simultaneous measurement of orthogonal polarizations in free-space beams, and formulate an algorithm for the polarization-resolved assessment of guided modes in a bus waveguide-ring resonator system.
