Broadband Electron Paramagnetic Resonance Using a Tunable Continuous-Wave Terahertz Photomixer Source

We developed a novel broadband electron paramagnetic resonance (EPR) technique using a tunable continuous-wave (CW) terahertz(THz) source. A photoconductive antenna (PCA) generates frequency-tunable THz waves in a wide frequency region of 0.05-1.1 THz as a beat frequency of two laser beams with different wavelengths. We successfully observed EPR signals of some samples at room temperature in a transmission setup. Advantages of this technique are its high dynamic range of homodyne detection and continuously tunable THz generation/detection. Thus, high-resolution EPR spectroscopy as well as frequency-swept EPR experiment will become possible using this technique.