**11. References**

252 Advanced Photonic Sciences

nonmagnetic material. It turned out that the numerically converged spin density was a minimal 1.35 x 10-4 *μB*/atom, showing that the proposed procedure is robust against

Fig. 25. The optical *μr* spectrum of Fe crystal obtained from the proposed procedure.

the imposed EM wave in such a way that actually results in the Fresnel equations.

powers. This kind of microscopic approaches are called "dipole engineering".

This chapter contains a clear, yet rigorous, picture as to how the real physical causes behind all these macroscopic optical phenomena – i.e., the microscopic electric and magnetic dipoleswork to come up with such macroscopic results. Both the electric and magnetic dipoles react to

In arriving at the more intuitive "scattering form" of the Fresnel equations, microscopic EMinduced physical electric and magnetic dipoles were rigorously employed as the source of electromagnetic waves by Doyle et al. Motivated by such an approach, the authors started to speculate how the incorporation of permanent dipoles might affect many macroscopic optical phenomena, e.g., the Brewster angle of a specific optical material. Among its predictions, the traditionally fixed Brewster angle of a specific material now not only becomes dependent on the density and orientation of incorporated permanent dipoles, but also on the incident light intensity (more precisely, the incident wave electric field strength). Further, two conjugated incident light paths would give rise to different refracted wave

Theoretical elaboration and then IR experiments on poled polyvinylidene fluoride (PVDF) films were conducted to verify the emergence of asymmetric reflections at varying incident angles, as well as the inverse dependence of reflectivity upon the impinging light intensity. In addition, experiments on dipole-engineered PVDF films show that by way of adding/reducing permanent dipole density and varying orientations, the aforementioned theoretical predictions can be evidenced unambiguously in the visible light range. Further, effective polarization density can be quantified from the above experiments subjected to different dipole engineering processes. As a result, the traditionally elliptic contour of a slanted two dimensional section of the refractive index ellipsoid now manifests symmetric

erroneous initial conditions.

**10. Conclusion** 


**10** 

*1Bulgaria 2Armenia* 

**High Resolution Laser Spectroscopy of Cesium** 

David Sarkisyan2, Dimitar Slavov1, Petko Todorov1 and Kapka Vaseva1

*2Institute for Physical Research, National Academy of Sciences of Armenia, Ashtarak* 

High resolution laser spectroscopy of alkali vapor contained in conventional thermal optical cells with centimeter dimensions is widely used for various applications: among them wavelength references, atomic clocks, precise optical magnetometers, slow and stored light etc. For all these photonic sensors, the reduction of their dimensions is of significant importance. One of the main concerns is to keep the parameters of the photonic sensor when reducing its size. In this chapter are presented the obtained by authors experimental and theoretical results concerning high-resolution spectroscopy of Cs vapor layer with nanometric thickness. The thickness of the vapor layer varies from 100 nm to about 5000 nm. The practical importance of this study is accompanied by numerous new peculiarities of atomic spectra of 1 D confined atoms, when the nanometric dimension approaches the wavelength of the irradiating light. These peculiarities in the absorption and fluorescence

**2. Unique optical cells for confinement of Cs atomic layers with nanometric** 

In this chapter, the high resolution laser spectroscopy is concerned of alkali vapor confined in unique optical cell with nanometric thickness [Sarkisyan, 2001], further on called Extremely Thin Cell (ETC). The transversal and longitudinal dimensions of such cell (Fig.1) differ significantly. The distance between the high-quality ETC windows L varies from 100 nm to (1-3) μm. At the same time, the cell window diameter is about 2 cm (Fig.1b). Therefore, a strong spatial anisotropy is present for the time of interaction between atoms confined in the ETC and the laser radiation used for spectroscopy performed with such

Let us consider Cs atoms flying orthogonally to the cell windows (Fig.1a, atoms denoted by v┴), which average thermal velocity at room temperature is about 200 m/s. Those atoms

**1. Introduction** 

**thickness** 

optical cell.

spectra represent a basic importance as well.

**2.1 Main characteristics of atomic confinement** 

**Vapor Layers with Nanometric Thickness** 

Stefka Cartaleva1, Anna Krasteva1, Armen Sargsyan2,

*1Institute of Electronics, Bulgarian Academy of Sciences, Sofia* 

