Zero field CW ODMR spectrum of a NV-diamond plate. Several important quantum parameters like zero-field splitting D, strain E, linewidth W and contrast can be extracted.

A zero-magnetic-bias CW-ODMR spectrum of a NV diamond plate with a long T₂ relaxation time (~450 µs) exhibits narrow linewidths that reveal a rich hyperfine structure from ¹⁴N and ¹⁵N, superimposed on the E-strain splitting.

Characteristic CW spectrum of a single crystal NV-diamond plate in bias magnetic field oriented along one of the NV center’s ⟨111⟩ crystallographic directions, which is confirmed by the characteristic resonance pattern shown in the spectrum. From the resonance separation distance, the strength of the magnetic field can be estimated, since the splitting rate at about 2.8MHz/Gauss is known (the gyromagnetic ratio of an electron). In our case we worked with fields at about 100-120 G. The resonance linces, such as the left most line at 2.5967GHz, can be saved and used for pulsed experiments.

Magnetic field vector analysis from a CW ODMR spectrum. In a single-crystal diamond, the lattice contains four distinct NV axis orientations. A magnetic field projected onto these axes causes Zeeman splitting, but the amount of splitting differs for each NV orientation. As a result, up to four pairs of resonance peaks can appear in a biased CW spectrum. From the splitting distances, the components of the magnetic field vector can be determined, allowing reconstruction of its spatial orientation relative to crystal lattice. The panel shows the reconstructed vector and its spherical coordinates for the Bias Field Spectra shown at the previous panel on the left.

Temperature dependence of the zero-field splitting parameter D enables real-time temperature monitoring. A dedicated mode within ODMR-base and ODMR-pulse utilized a fast algorithm based on frequency modulation extracts temperature across a wide range (~100 °C). With high-contrast and narrow-line samples—such as ADAMAS 3 μm temperature-annealed microdiamonds—temperature resolutions approaching ~10 mK can be achieved. In this example, changes in room temperature were monitored as the air conditioning unit engaged periodically, with a cycle of approximately 15 minutes.

A typical Rabi oscillation pattern for NV-diamond plate. Rabi oscillations represent the simplest experiment involving microwave pulses. The detection scheme is similar to that used in T₁ relaxation measurements, but with one key difference: a progressively longer microwave pulse is inserted between the initialization and detection pulses. The microwave frequency must be tuned to the resonance line identified in the CW spectrum. The primary purpose of this experiment is to determine the strength of the microwave field and calibrate the pulse time axis by linking the oscillation period to time units—specifically, to establish the duration of a π pulse in nanoseconds. From the damped harmonics simulation or simply position of the first dip the length of the typical π pulse can be estimated to be about 100ns.

Positive contrast Hahn echo of NV-diamond plate. Once the temporal calibration of the pulses is established, more complex pulse sequences can be performed. Here, we measured the Hahn echo signal using the standard [π/2−τ1−π−τ2−π/2] sequence. The purpose of this sequence is to eliminate static or slow fluctuations in the magnetic environment that contribute to spin dephasing, by refocusing the magnetization in the xy-plane. The echo was recorded with τ1=10 μs, while the position of the final π/2 detection pulse was swept around the refocusing point at 2*τ1 over a 1 µs range. The resulting signal exhibits a Gaussian-shaped echo, with the linewidth representing the inhomogeneous transverse relaxation time, T₂∗ . From the fit, we find T₂∗=0.08 μs. The magnitude of the echo signal is critical for a wide range of advanced experiments, making its optimization essential.

T₂ relaxation for an NV-diamond plate. This experiment is built on the Hahn echo sequence to investigate transverse decoherence by gradually increasing the evolution time. Even after magnetization is refocused—eliminating static or quasi-static inhomogeneous broadening—the echo amplitude still decreases with increasing τ due to the stochastic nature of the remaining magnetic noise. In an ensemble measurement, only a fraction of NV⁻ centers undergo state flips due to interaction with nearby ¹³C nuclei causing the total echo signal to contain both modulated and unmodulated components. T₂ relaxation curve decomposition into the modulation and relaxation envelopes is included into the software.

A typical T₁ relaxation curve NV-diamond plate. In the T₁ relaxation experiment the lifetime of the polarized state is estimated. This experiment can be performed at zero-field and without any microwave excitation involved. The light initialization and detection pulses are applied at progressively delayed intervals. The fluorescence signal recorded is proportional to the polarized state lifetime. Given the paramagnetic purity of the sample, long relaxation time with no substantial deviations is recorded.