Microwave Fluorescence Detection of Spin Echoes

Area of Science:

• Quantum Optics
• Solid-State Physics
• Spectroscopy

Background:

• Electron paramagnetic resonance (EPR) spectroscopy traditionally relies on inductive detection.
• Recent advancements in single microwave photon detectors enable new EPR detection methods.
• Radiative relaxation of electron spins can be used for sensitive EPR measurements.

Purpose of the Study:

• To report the detection of spin echoes in the spin fluorescence signal.
• To demonstrate a novel fluorescence-detected EPR spectroscopy method.
• To measure spin coherence times and nuclear spin couplings using this technique.

Main Methods:

• Utilizing a π/2_{X}-τ-π_{Y}-τ-π/2_{Φ} pulse sequence.
• Detecting spin echoes via spontaneous photon emission from electron spins.
• Experimentally implementing the method with Erbium (Er^{3+}) ions in a CaWO_{4} crystal.

Main Results:

• Successfully detected spin echoes in the fluorescence signal, modulated by relative phase Φ.
• Measured the spin coherence time of Er^{3+} ions.
• Observed echo envelope modulation due to hyperfine coupling with surrounding ^{183}W nuclear spins.
• Demonstrated a higher signal-to-noise ratio for fluorescence-detected echoes compared to inductive detection.

Conclusions:

• Fluorescence-detected spin echoes provide a sensitive method for EPR spectroscopy.
• This technique allows for detailed studies of spin coherence and hyperfine interactions.
• The enhanced signal-to-noise ratio makes fluorescence detection a promising alternative for EPR measurements.