We investigate spontaneous emission properties and control of the zero phonon line (ZPL) from a diamond nitrogen–vacancy (NV) center coherently driven by a single elliptically polarized control field. We use the Schrodinger equation to calculate the probability amplitudes of the wave function of the coupled system and derive analytical expressions of the spontaneous emission spectra. The numerical results show that a few interesting phenomena such as enhancement, narrowing, suppression, and quenching of the ZPL spontaneous emission can be realized by modulating the polarization-dependent phase, the Zeeman shift, and the intensity of the control field in our system. In the dressed-state picture of the control field, we find that multiple spontaneously generated coherence arises due to three close-lying states decaying to the same state. These results are useful in real experiments.

Laser-polarization-dependent spontaneous emission of the zero phonon line from single nitrogen–vacancy center in diamond

Absorption and refraction of the inner transition F2↔F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1↔F3 and F2↔F4 are resonantly interacted with drive field with frequency ωc and Rabi frequency Ωc, and saturation field with ωs and Ωs, respectively. For the suitable Rabi frequencies Ωc and Ωs, we obtain the Mollow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of Ωs. Finally, the refractive index enhancement is predicted for a wide spectral region.

Stimulated emission and multi-peaked absorption in a four level N-type atom

We present a scheme that provides a strong basis for precise localization of atoms, using superposition of two standing wave fields in a three level -type gain assisted model. We show how atomic interference and diffraction occur at a particular node or antinode region of the standing wave fields. Two, three, four and even single localized peaks of atoms are observed in both full-wavelength and sub-half-wavelength domains, with 100 percent localization probability in a single peak. Dark lines appearing in the node region of the standing wave fields show strong evidence for atomic destructive interference. The proposed scheme allows for efficient localization of an atom to a particular point.

Precise position measurement of an atom using superposition of two standing wave fields

A four-level atomic system with a closed interaction loop connected by two coherent driving fields and a microwave field is investigated. The results show that inversionless gain can be achieved on a higher frequency transition outside the closed interaction loop, and the gain behaviour can be modulated by the phase of the closed loop as well as the amplitude of the microwave field. The phase sensitivity property in such a scheme is similar to that in an analogous configuration with spontaneously generated coherence, but it is beyond the rigorous condition of near-degenerate levels with non-orthogonal dipole moments. Therefore this scheme is much more convenient in experimental realization.

Phase-dependent inversionless gain in a four-level atomic system with a closed interaction loop

We have investigated the two-dimensional (2D) atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.

https://iopscience.iop.org/article/10.1088/1674-1056/22/7/074203/pdf

Two-dimensional atom localization via probe absorption in a four-level atomic system

We propose a new four-level atomic model for achieving light amplification at a short wavelength, where direct incoherent pumping into the top level is avoided by the advantage of coherent pumping. In this model, the lower level of the probe transition is an excited state but not the usual ground state. By analytical as well as numerical calculations, we find that the probe gain, either with or without population inversion, which depends on the relation between spontaneous decay rates γ42 and γ21, can be achieved with proper parameters. We note that the Raman scattering gain always plays an important role in achieving the probe amplification.

Wang Deng-Pan

Papers

The probe gain with and without inversion in a four-level atomic model: light amplification at a short wavelength