High-frequency microstrip cross resonators for circular polarization electron paramagnetic resonance spectroscopy

Area of Science:

• Microwave Engineering
• Materials Science
• Spectroscopy

Background:

• Precise control over microwave polarization is essential for advanced spectroscopic techniques.
• Existing methods may lack the required fidelity or frequency range for specific applications.
• High dielectric constant substrates are often used to miniaturize microwave components.

Purpose of the Study:

• To design and implement a novel microstrip resonator enabling absolute control of microwave polarization degree.
• To achieve high polarization fidelity for frequencies up to 30 GHz.
• To validate the resonator's performance using electron paramagnetic resonance (EPR) spectroscopy.

Main Methods:

• A cross-shaped microstrip resonator was designed using two perpendicular half-wavelength resonators on a GaAs substrate.
• Microstrip feed lines were coupled to the resonator arms to control microwave stimuli magnitude and phase.
• The resonator was tested at low temperatures, measuring transmitted signals via a dedicated output port.
• Electron paramagnetic resonance (EPR) spectra were recorded using an S=5/2 molecular magnet system.

Main Results:

• The microstrip resonator achieved absolute control over microwave polarization degree up to 30 GHz.
• A fidelity of 82% circular polarization was demonstrated over the central resonator area.
• The design facilitates measurements at low temperatures by minimizing signal masking from reflections.

Conclusions:

• The novel microstrip resonator offers precise polarization control for microwave frequencies.
• This technology is suitable for low-temperature spectroscopic applications like EPR.
• The design demonstrates a significant advancement in microwave sensing and control.