In this thesis, the author develops new high-power millimeter wave techniques for measuring the hyperfine structure of positronium (Ps-HFS) directly for the first time in the world. Indirect measurement of Ps-HFS in the literature might have systematic uncertainties related to the use of a static magnetic field. Development of the millimeter wave devices supports the precise determination of Ps-HFS by directly measuring the Breit-Wigner resonant transition from o-Ps to p-Ps without the magnetic field. At the same time, the width of the measured Breit-Wigner resonance directly provides the lifetime of p-Ps. This measurement is the first precise spectroscopic experiment involving the magnetic dipole transition and high-power millimeter waves. The development of a gyrotron and a Fabry-Pérot cavity is described as providing an effective power of over 20 kW, which is required to cause the direct transition from o-Ps to p-Ps. Those values measured by the newly developed millimeter wave device pave the way for examining the discrepancy observed between conventional indirect experiments on Ps-HFS and the theoretical predictions of Quantum Electrodynamics.

This book is for those who have some knowledge of optics, but little or no previous experience in interferometry. Accordingly, the carefully designed presentation helps readers easily find and assimilate the interferometric techniques they need for precision measurements. Mathematics is held to a minimum, and the topics covered are also summarized in capsule overviews at the beginning and end of each chapter. Each chapter also contains a set of worked problems that give a feel for numbers.The first five chapters present a clear tutorial review of fundamentals. Chapters six and seven discuss the types of lasers and photodetectors used in interferometry. The next eight chapters describe key applications of interferometry: measurements of length, optical testing, studies of refractive index fields, interference microscopy, holographic and speckle interferometry, interferometric sensors, interference spectroscopy, and Fourier-transform spectroscopy. The final chapter offers suggestions on choosing and setting up an interferometer.

Explains what spin is and how spins are polarized to study elementary particles, nuclei, atoms and molecular structures.