In the master's thesis, an optical fiber Mach–Zehnder interferometer with phase stabilization based on thermal optical fiber control was developed. Phase stabilization of the interferometer is crucial for eliminating mechanical and temperature disturbances from the environment. This enables measurements to be consistently performed in the area of maximum sensitivity, known as the quadrature point. We upgraded the interferometer with a free field in the measuring branch, where we inserted suspensions of nanoparticles in water. These were excited with laser pulses of various wavelengths, with an emphasis on green light due to its strong plasmonic absorption. Phase detection measurements showed that the system enables detection of laser-induced temperature changes caused by light absorption on particles of different sizes and concentrations. The results confirm that phase-stabilized optical fiber interferometers can be used to accurately and robustly detect nanoparticles in liquids, with significant potential for use in environmental monitoring and biomedical diagnostics.
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