Xing-Fei He

Raman heterodyne detection of electron paramagnetic resonance

We report the detection of an electron paramagnetic resonance signal using Raman heterodyne spectroscopy, a rf -optical double-resonance technique. The signals are associated with the nitrogen-vacancy center in diamond, which has a spin-triplet ground state. A three-line spectrum associated with the nitrogen hyperfine structure is observed for various magnetic field strengths and crystal orientations.

Raman heterodyne detected electron-nuclear-double-resonance measurements of the nitrogen-vacancy center in diamond

We report two new applications of the Raman heterodyne detection technique. Raman heterodyne detected electron-nuclear double resonance and a double rf resonance technique are used to obtain the hyperfine structure of the nitrogen-vacancy center in diamond.

Autler-Townes effect of the photoexcited diamond nitrogen-vacancy center in its triplet ground state

The Autler–Townes effect in nuclear magnetic resonance (NMR) and electron paramagnetic resonance has been observed using recently developed Raman heterodyne techniques. The measurements were carried out on the nitrogen‐vacancy color center in diamond, where the 3A↔3E optical transition was driven by a single mode dye laser at 638 nm while the magnetic transitions in the 3A ground state were driven by two rf fields. The measured splittings in the NMR lines were found to be in good agreement with theoretical predictions. Using the Autler–Townes effect, the magnitude of the dipole moments of the mI=0↔±1 (mS=0) transitions in the ground state was determined, and found to be the same. Comparison of this latter result with the NMR spectra shows that Raman heterodyne signal intensities are determined by population factors.

Raman heterodyne studies of the nitrogen-vacancy centre in diamond

Abstract The Raman heterodyne detected EPR and NMR frequencies associated with the nitrogen-vacancy centre in diamond are found to be consistent with those for a spin-triplet ground state with the following spin-Hamiltonian parameters g = 2.0028, gn = 0.4036, D = 2.88 GHz, |A∥| = 2.3 MHz, |A ˔ | = 2.1 MHz and |P| = 5.04 MHz. The magnitude and sign of the Raman heterodyne signals are shown to be affected by optical pumping and the significance of these observations is discussed.

Application of the Raman heterodyne technique for the detection of EPR and ENDOR

Raman heterodyne detection is a coherent optical-RF double resonance technique where the optical and RF fields induce coherence within a three level system and a resultant Raman field is measured using heterodyne detection. This approach has been used previously to detect NMR and more recently EPR. In this paper the parameters that affect the amplitude and signal to noise ratio of the Raman heterodyne signals are considered. The power levels in relation to the oscillator strength and dephasing times, the amplitude and spectrum of the laser frequency jitter in relation to the optical homogeneous linewidths and holeburning rates, and the sample properties such as absorption strength and optical quality, are all factors that affect the Raman signal. The presentation is focused on the Raman heterodyne detected EPR of the nitrogen-vacancy pair centre in diamond making comparisons with Raman heterodyne detected NMR signals obtained for rare earth ion systems. RF-RF double resonance studies, RF holeburning and ENDOR, which give information about the hyperfine levels are also reported for the nitrogen-vacancy centre. The resonance frequencies are in agreement with those predicted from the spin Hamiltonian. The factors affecting the lineshapes and relative intensities of the double resonance signals are discussed.

Anomalous lineshapes in Raman heterodyne detected EPR

Abstract An unusual lineshape has been observed in the Raman heterodyne NMR and EPR signals associated with a nitrogen-vacancy centre in diamond. This lineshape is shown to result from power broadening effects and can be expected as a general result from any Raman heterodyne signal where the transition under study can be saturated by the applied RF field.

Zeeman quantum beat in nuclear quadrupole resonance probed by Raman heterodyne spectroscopy

Abstract The Zeeman quantum beat in nuclear quadrupole resonance of the diamond nitrogen-vacancy centre has been observed using Raman heterodyne spectroscopy — a coherent optical-RF double resonance technique. In the experiment, a magnetic field was applied and set corresponding to the level anticrossing regime, where the electron and nuclear spin states are strongly mixed and therefore the nuclear spin transitions are greatly enhanced. The 6380 A 3 A ↔ 3 E zero-phonon transition was driven by a single mode CW laser while the m I = 0 ↔ ± 1 ( m S = 0) magnetic transitions in the 3 A ground state were excited by an RF pulse. Beat modulation was observed to appear as superimposed on the total RF emission signal detected by a photodiode. The beat frequency was found to be in excellent agreement with the Zeeman splitting of the m I = ± 1 ( m S = 0) levels.