Public defence in Measurement Science and Technology, M.Sc. Sucheta Sharma

Public defence from the Aalto University School of Electrical Engineering, Department of Information and Communications Engineering
Doctoral hat floating above a speaker's podium with a microphone

The title of the thesis: Applications of Interferometric Measurements and Photoacoustic Detection in Optical Metrology

Doctoral student: M.Sc. Sucheta Sharma
Opponents: Dr. Howard W. Yoon, National Institute of Standards and Technology, United States and Dr. Tom Kuusela, University of Turku, Finland
Custos: Prof. Erkki Ikonen, Aalto University School of Electrical Engineering, Department of Information and Communications Engineering 

Optical metrology represents the discipline of scientific and technical studies dealing with the measurements employing electromagnetic radiation. The field of optical metrology can be divided into separate research categories, e.g., spanning from optical power measurements using detectors to dimensional metrology employing interferometers. Hence, it can be observed that, three prime constituents — a source of electromagnetic radiation, a process which guides the measurement loop, and finally the detection of the resulting response of the source actuated measurement process — form the foundation of experimental studies in optical metrology. This dissertation focuses on the applicability of interferometric and photoacoustic techniques in order to contribute to new developments for the above-mentioned measurement and detection methodologies in the field of optical metrology. The interferometric methods, presented in this dissertation, can be applied for the quality control of optical components and for analyzing three-dimensional structures with improved measurement speed and accuracy. Because of enabling the non-contact measurements, the presented interferometric methods can offer excellent solutions by avoiding the possibility of surface damages. For the development of detector systems, photoacoustic detection method has been applied. With a cantilever pressure sensor and a suitable absorber material, wavelengths from ultraviolet to infrared spectral region have been detected. The detector response in the terahertz range has also been studied using this method. The detection system with the robust cantilever sensor is capable of providing good detection linearity, large dynamic range, and high damage threshold.

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