We propose and study, theoretically and experimentally, a new scheme of excitation of a coherent population trapping resonance for D1 line of alakli atoms with nuclear spin I = 3/2 by bichromatic linearly polarized light (lin||lin field) at the conditions of spectral resolution of the excited state. The unique properties of this scheme result in a high contrast of dark resonance for D1 line of 87 Rb.Great attention is drawn to the study of the coherent interaction of atoms with electromagnetic fields. Under specific experimental conditions coherent atom-field interaction result in what is called the coherent population trapping effect (CPT) [1]. Narrow-width CPT resonances ("dark resonances") induced by this effect are used in atomic clocks [2,3,4], precise magnetometers [5,6], laser cooling, spectroscopy, optical signal processing, etc. Most applications require CPT resonance with optimized parameters such as large amplitude, small spectral width and small background simultaneously. In addition minimized light shifts are needed in metrology.Most of theoretical and experimental studies of the CPT phenomena are made for alkali atoms. The CPT resonance is usually observed with a bichromatic field consisting of two resonant laser fields with the frequency difference changing in the vicinity of the hyperfine splitting of the ground state. At exact two-photon resonance atoms are optically pumped into a coherent nonabsorbing superposition of the ground states which is refereed to as a dark state. A variety of different excitation schemes of the CPT resonances were proposed. They differ by the choice of the isotope, excitation line (D1 or D2), the field characteristics (detuning, amplitude, and polarization of the field components). Different techniques increasing coherent atom-field interaction time also play an important role on the build up of the ground state coherence. These techniques include the use of a mixture of an alkali vapor with different buffer gases or/and use of cells with antirelaxation coating of the inner walls. Experiments [7,8] carried out with the cell containing a mixture of Cs and a buffer gas revealed a resonance with a linewidth as small as 50 Hz in the case of D2 line excitation. However, the contrast of the CPT resonance in these experiments was only a small fraction of a percent. In [9] it was shown that using the D1 line instead of D2 line for excitation significantly increases the contrast of the dark resonance. This fact was later confirmed by other authors [10]. In these experiments resonances were produced by circularly polarized light fields (σ-σ) which induced two-photon transitions between magnetic sublevels with the same quantum number m (m-m resonances). In atomic clocks the 0-0 transition is used because it is first order insensitive to the magnetic field. The D1 line provides better resonance than the D2 line since at exact two-photon resonance in D1 line a dark superposition state exists even when hyperfine components of the excited state are not spectrally resolved because of ...

We develop a generalized principle of electromagnetically induced transparency (EIT) vector magnetometry based on high-contrast EIT resonances and the symmetry of atom-light interaction in the linearly polarized bichromatic fields. Operation of such vector magnetometer on the D 1 line of 87 Rb has been demonstrated. The proposed compass-magnetometer has an increased immunity to shifts produced by quadratic Zeeman and ac-Stark effects, as well as by atom-buffer gas and atom-atom collisions. In our proof-of-principle experiment the detected angular sensitivity to magnetic field orientation is 10 −3 deg/Hz 1/2 , which is limited by laser intensity fluctuations, light polarization quality, and magnitude of the magnetic field.

We present a joint theoretical and experimental characterization of the coherent population trapping (CPT) resonance excited on the D 1 line of 87 Rb atoms by bichromatic linearly polarized laser light. We observe high-contrast transmission resonances (up to ≈25%), which makes this excitation scheme promising for miniature all-optical atomic clock applications. We also demonstrate cancellation of the first-order light shift by proper choice of the frequencies and relative intensities of the two laser-field components. Our theoretical predictions are in good agreement with the experimental results.

The electron spin of nitrogen--vacancy (NV) centers in diamond offers a solid-state quantum bit and enables high-precision magnetic-field sensing on the nanoscale. Implementation of these approaches in a fiber format would offer unique opportunities for a broad range of technologies ranging from quantum information to neuroscience and bioimaging. Here, we demonstrate an ultracompact fiber-optic probe where a diamond microcrystal with a well-defined orientation of spin quantization NV axes is attached to the fiber tip, allowing the electron spins of NV centers to be manipulated, polarized, and read out through a fiber-optic waveguide integrated with a two-wire microwave transmission line. The microwave field transmitted through this line is used to manipulate the orientation of electron spins in NV centers through the electron-spin resonance tuned by an external magnetic field. The electron spin is then optically initialized and read out, with the initializing laser radiation and the photoluminescence spin-readout return from NV centers delivered by the same optical fiber.

We demonstrate a scanning fiber-optic probe for magnetic-field imaging where nitrogen-vacancy (NV) centers are coupled to an optical fiber integrated with a two-wire microwave transmission line. The electron spin of NV centers in a diamond microcrystal attached to the tip of the fiber probe is manipulated by a frequency-modulated microwave field and is initialized by laser radiation transmitted through the optical tract of the fiber probe. The two-dimensional profile of the magnetic field is imaged with a high speed and high sensitivity using the photoluminescence spin-readout return from NV centers, captured and delivered by the same optical fiber.