A simple, room-temperature, cavity- and vacuum-free interface for an efficient photon-matter interaction is implemented. In the experiment a heralded single photon generated by the process of spontaneous parametric down-conversion is absorbed by a single atom-like system, specifically a nitrogen-vacancy color center in diamond. Here phonon-assisted absorption solves the mismatch problem of a narrow absorption bandwidth in a typical atomic medium and broadband spectrum of quantum light. The source is tunable in the spectral range $452-575$ nm, which overlaps well with the absorption spectrum of nitrogen-vacancy centers. This can also be considered as a useful technique paving the way for development of novel quantum information processing and sensing applications.
A simple, room-temperature, cavity- and vacuum-free interface for an efficient photon-matter interaction is implemented. In the experiment a heralded single photon generated by the process of spontaneous parametric down-conversion is absorbed by a single atom-like system, specifically a nitrogen-vacancy color center in diamond. Here phonon-assisted absorption solves the mismatch problem of a narrow absorption bandwidth in a typical atomic medium and broadband spectrum of quantum light. The source is tunable in the spectral range $452-575$ nm, which overlaps well with the absorption spectrum of nitrogen-vacancy centers. This can also be considered as a useful technique paving the way for development of novel quantum information processing and sensing applications.
COSMA: Coherent Optics Sensors for Medical Application is an European Marie Curie Project running from 2012 to March 2016, with the participation of 10 teams from Armenia, Bulgaria, India, Israel, Italy, Poland, Russia, UK, USA. The main objective was to focus theoretical and experimental research on biomagnetism phenomena, with the specific aim to develop all-optical sensors dedicated to their detection and suitable for applications in clinical diagnostics. The paper presents some of the most recent results obtained during the exchange visits of the involved scientists, after an introduction about the phenomenon which is the pillar of this kind of research and of many other new fields in laser spectroscopy, atomic physics, and quantum optics: the dark resonance.
We describe our investigations aiming at the detection of the Bloch–Siegert effect (BSE) with nonlinear magneto– optical effects. Although theoretical aspects of the BSE were thoroughly investigated, there are still open questions concerning experimental demonstration of the effect. The most recent BSE experiment was performed in alkali–metal vapor, where atoms were pumped by electron collisions, but the results of those investigations were rather inconclusive. Here we propose to search for the BSE with optically pumped magnetometers (OPMs) and describe the preparation of a dedicated setup providing improved capabilities for observation of the effect in atomic vapor. As the main difficulty is the weakness of the effect and presence of other competing processes, we concentrate on identification and assessment of various systematic effects that may imitate and/or perturb the investigated effect.
Recently we have demonstrated that conventional (free-space) Faraday rotation spectroscopy (FRS) can be successfully transitioned into optical fiber-based sensing architectures using paramagnetic gas-filled hollow-core photonic bandgap fibers (HC-PCFs)1. Our measurements revealed that due to the birefringence properties of the HC-PCFs, behavior of the fiber-optic FRS signals is substantially different compared to free-space FRS systems. Furthermore, magnetic circular dichroism tends to have much higher influence on the FRS signals than in other systems. To explain this behavior we have developed a theoretical model, and shown that close agreement with the experimental data can be achieved. In this paper we focus attention on the detailed explanation and the in-depth discussion of the model and assumptions incorporated within it. This approach can be easily extended to account for parasitic effects that take place in real-world FRS sensor systems such as imperfect polarizers or birefringent gas cell windows.
In this paper, we report on our study of UV-VIS absorption spectroscopy in suspended-core optical fibres (SCFs) filled with organic-dye solutions. We compare two different dye classes, the anionic dye - bromophenol blue sodium salt (BB) and cationic dye - oxazine 725 perchlorate (OX). While the results obtained with BB are in a good agreement with the spectra measured in a standard reference cuvette, those obtained with OX are different and reveal much stronger absorption of light than in cuvettes. This stronger absorption indicates accumulation of the dye molecules on the short section of the core close to the end of the fibre. This observation demonstrates difference in physicochemical properties of the two dye classes and is important for the development of chemical sensors based on SCFs.
The small size of the core (about 1 μm) of the suspended-core optical fibres gives rise to evanescent wave in
the surrounding channels. That process allows efficient coupling between light and liquid introduced into the channels
and application of the fibre for analytic purposes. In the presented work, the channels of a suspended-core fibre were
filled with water and aqueous solutions of oxazine 725 perchlorate and their absorption spectra were measured. While
the spectra of the water-filled fibre were consistent with the Lambert-Beer law, the absorptivity of the fibre filled with
oxazine 725 perchlorate solution demonstrated an increased sensitivity caused by aggregation of the oxazine molecules,
independent on the fibre length.
We propose and analyze a scheme for creation of coherent superposition of meta-stable states in a multilevel
atom. The scheme is based on interaction of a frequency modulated (chirped) laser pulse and a pulse of a
constant carrier frequency with the atom having two meta-stable (ground) states and multiple excited states. The
negligible excitation of the atoms is a priority in the proposed scheme to eliminate the de-coherence processes
caused by the decay of the excited states. The scheme is applied to create coherent superposition of magnetic
sublevels of ground states of the 87Rb atom taking into account all allowed electric-dipole transitions between
magnetic sublevels of the 5 2S1/2
- 52P3/2 transition (D2 line).
In addition to the theoretical analysis we consider possible experimental realizations of the proposed
coherence creation scheme and discuss their feasibilities and constraints. We concentrate on a detection of the
superposition state in the Faraday-rotation experiment. Such detection reduces technical laser noise background
and offers high sensitivity of the coherence detection. Moreover, it allows extra control of the atomic sample and
the interaction dynamics by external magnetic field.
We demonstrate a magnetometric technique based on nonlinear magneto-optical rotation using amplitude modulated
light. The magnetometers can be operated in either open-loop (typical nonlinear magneto-optical rotation with
amplitude-modulated light) or closed-loop (self-oscillating) modes. The latter mode is particularly well suited for
conditions where the magnetic field is changing by large amounts over a relatively short timescale.
Cooling and trapping neural atoms with laser beams became a standard method of studying atom properties in temperatures close to absolute zero. Precise knowledge of physical parameters of the atomic sample is of prime importance in such studies, particularly the knowledge of the number of trapped atoms, their density and temperature. Diagnostics aiming at determination of these parameters has to be performed optically, mainly with the spectroscopic methods. In this paper, we present basic principles of obtaining ultra-cold atoms and methods used for their diagnostics. Some examples of quantum effects specific for low-temperatures, revealed by these methods, are also demonstrated.
In the experiment with barium vapor (close approximation of a two-level system) we found spectra of resonance fluorescence having the form of a pressure-broadened line with a narrow, not collisionally broadened, dip. They are interpreted as the result of collisionally-induced quantum interference among possible spontaneous emission channels of a dressed atom subjected to stochastic perturbation. Also, the analogy between these effects and the coherent population trapping in three-level systems is pointed out.
The paper reviews various schemes of lasing without population inversion with particular
emphasis on these which seem to be most promising from the practical point of view. It is shown that
in some cases one can attribute the lasing to the population inversion in an appropriate reference frame.
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