Applications of Interferometric Measurements and Photoacoustic Detection in Optical Metrology

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2023-10-19
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Authors

Date

2023

Department

Informaatio- ja tietoliikennetekniikan laitos
Department of Information and Communications Engineering

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Mcode

Degree programme

Language

en

Pages

62 + app. 49

Series

Aalto University publication series DOCTORAL THESES, 169/2023

Abstract

Measurement loops and detectors are irreplaceable constituents of an experimental process in optical metrology. Interferometry and photoacoustic methods can be applied as key techniques for developing such measurement and detection systems. In this thesis, two interferometric measurement arrangements are presented. The phase modulation process in interferometry is important for the measurement speed. Mechanical phase modulation, in such cases, suffers from limitations with regard to driving voltage amplitude, increased modulation frequency and system noise. In this work, the potential of electro-optic phase modulation has been assessed for developing a multi-wavelength interferometric sensor to replace the mechanical phase modulation system. The results not only show the suitability of the electro-optic sensor to improve the measurement speed of the multi-wavelength interferometer, but the sensor is also able to operate at considerably low driving voltage. Another interferometric method driven by an optical system consisting of a mirror array has been presented in this thesis to measure the surface parallelism of step gauge faces. Contact methods are commonly used for this purpose. However, the research gap lies in the available options for non-contact methods to carry out such measurements. The alignment sensitivity is a major factor that controls the accuracy of the measurement with the presented array of mirrors which are arranged as a periscope and a triangular prism reflector-type configuration. Hence, in this work, methods to monitor the alignment sensitivity and estimate corresponding corrections have been presented. The theoretical and experimental studies on the performance of the custom-built optical system show that the system has the potential to serve as a suitable tool for non-contact surface parallelism measurement of step gauge faces. For the development of detection instruments, a silicon cantilever-based photoacoustic radiation detector is presented in this work. Photoacoustic detectors are widely employed for power meter applications, however, in most available cases, the pressure sensors have limitations on the highest detectable radiation power. The photoacoustic detector presented in this work, has shown radiation detection capability with a linear dynamic range of nearly six orders of magnitude and highest detectable power in the milliwatt level which can be further extended with suitable adjustments of the detection parameters. The spectral coverage of the system was initially tested from ultraviolet to infrared region, and in the latest work the radiation sensitivity has been successfully demonstrated in the terahertz range with proper absorber materials. A numerical model for designing the cantilever pressure sensor has also been developed to improve the detection sensitivity. It is concluded that the cantilever-based photoacoustic detector can be a good solution for power measurement applications which require a broad spectral coverage and large dynamic range with robust pressure sensing element offering high damage threshold.

Description

Supervising professor

Ikonen, Erkki, Prof., Aalto University, Department of Signal Processing and Acoustics, Finland

Thesis advisor

Manoocheri, Farshid, Dr., Aalto University, Finland

Keywords

interferometer, photoacoustics, terahertz, cantilever sensor, electro-optic, non-contact measurement, optical metrology

Other note

Parts

  • [Publication 1]: Sharma, Sucheta; Eiswirt, Peter; and Petter, Jürgen, "Electro optic sensor for high precision absolute distance measurement using multiwavelength interferometry", Optics Express 26, 3443-3451 (2018).
    DOI: 10.1364/OE.26.003443 View at publisher
  • [Publication 2]: Sharma, Sucheta; Nysten, Johan; Lassila, Antti; and Ikonen, Erkki, "Phasestepping interferometry for parallelism measurement of step gauge faces", Metrologia 60, 055004 (2023).
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202308305325
    DOI: 10.1088/1681-7575/ace7d5 View at publisher
  • [Publication 3]: Sharma, Sucheta; Laurila, Toni; Rossi, Jussi; Uotila, Juho; Vainio, Markku, Manoocheri, Farshid; and Ikonen, Erkki, "Electromagnetic radiation detection using cantilever-based photoacoustic effect: A method for realizing power detectors with broad spectral sensitivity and large dynamic range", Sensors and Actuators A: Physical 337, 113191 (2022).
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202203282689
    DOI: 10.1016/j.sna.2021.113191 View at publisher
  • [Publication 4]: Sharma, Sucheta; Ahmadi, Mohsen; Rossi, Jussi; Vainio, Markku; Sun, Zhipei; Steiger, Andreas; and Ikonen, Erkki, "Terahertz radiation detection with a cantilever-based photoacoustic sensor", Optics Express 30, 43417-43425 (2022).
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202211306722
    DOI: 10.1364/OE.469295 View at publisher

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https://urn.fi/URN:ISBN:978-952-64-1476-8

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[diss] Sähkötekniikan korkeakoulu / ELEC