Nitrogen-vacancy (NV) centers in diamond have been used as platforms for quantum information, magnetometry and imaging of microwave (MW) fields. The spatial distribution of the MW fields used to drive the electron spin of NV centers plays a key role for these applications. Here, we report a system for the control and characterization of MW magnetic fields used for the NV spin manipulation. The control of the MW field in the vicinity of a diamond surface is mediated by an exchangeable lumped resonator, coupled inductively to a MW planar ring antenna. The characterization of the MW fields in the nearfield is performed by an FFT imaging of Rabi oscillations, by using an ensemble of NV centers. We have found that the Rabi frequency over a lumped resonator is enhanced 22 times compared to the Rabi frequency without the presence of the lumped resonator. Our system may find applications in quantum information and magnetometry where a precise and controlled spin manipulation is required, showing NV centers as good candidates for imaging MW fields and characterization of MW devices.

We describe the realization of a homemade and portable setup to perform experiments of pulsed magnetic resonance of nitrogen-vacancy (NV) centers in diamonds. The system is fully implemented by using an Arduino Uno board equipped with an automatic voltage regulator microcontroller that is used as a transistor-transistor logic pulse sequencer to drive precise laser and microwave pulses with a resolution of 62.5 ns. The equipment is assembled with low-cost modules on a printed circuit board and placed in a compact box with a volume of 20 × 40 × 10 cm3. The detection system is based on a switched integrator and a photodiode in the vicinity of a diamond substrate and read by oversampling the analog-to-digital converter of Arduino Uno. We characterize a CVD diamond sample by performing the pulsed optically detected magnetic resonance and we show the possibility to perform a coherent manipulation of the electron spin of NV centers by driving Rabi oscillations up to 6 MHz with microwave powers within 1 W. We demonstrate different pulse sequences to study electron spin relaxation and dephasing. Finally, we propose additional modules and an antenna to perform the multifrequency manipulation of the electron spin by microwave and radio-frequency pulses. Compared to the previous studies, our system results in a low-cost setup with significantly reduced complexity, which finds application as a learning module for science education and enables a wider audience to access the magnetic resonance in diamond.

We investigated spectral-hole narrowing in optical transitions between hyperfine sublevels in isotopically purified erbium ions (167Er3+). The homogeneous broadening Γh of the optical transition was measured in purified and non-purified Er3+-doped crystals via spectral-hole burning. The measured Γh in the purified 167Er3+ exhibited a significant reduction of the hole width because the fluctuation of the local magnetic field induced by the electron spins of the surrounding Er3+ ions was eliminated. Because the narrowing of the Γh is equivalent to the prolongation of the coherence time, the isotopic purification is effective for the coherent manipulation of quantum states.

The four wave mixing (FWM) process is widely exploited for the generation of tunable ultrashort light pulses. Usually this process is driven in bulk materials, which are however prone to optical damage at high pump laser intensities. A tunable source of ultrashort 10 μJ level pulses in the visible spectral region is described here. In particular, we report on the implementation of FWM driven by a two-color ultrafast laser pulse inside a gas-filled hollow core fiber (HCF). Due to the high-damage threshold and the long interaction distance, the HCF-based FWM configuration proves to be suitable for high-energy applications. Moreover, this technique can be potentially used for ultrashort pulses generation within a wide range of spectral regions; a discussion on the possibility to extend our scheme to the generation of few-cycle mid-IR pulse is provided.