We introduce a detailed study of a transverse magnetic mode excitation in an atomic mirror. It is easy to demonstrate that in this geometry, we have:
. There are two independant solutions of the Maxwell equations.1 One introduces a TE excitation (Ey, Bx and Bz). The other one gives a TM excitation (By, Ex and Ez) coupled between them.
Figure 1 Resonant dielectric structure: the waveguide (Ti02, refraction index n3=2.387 and thickness 2d=67.9nm) is separated from the glass prism (LaSFN18, refraction index n1=1.893) by a layer of low index, the gap, (SiO2, thickness a=700nm, refraction index n2=1.49). The dielectric layers are deposited by a laser beam at
=780nm. The fourth medium is vacuum (refraction index n4=1).
Maxwell equations:
The Maxwell equations [1, 3] give:
In order to introduce the right relationships, we present the electric field in the multi-layer system for a TE excitation.
For a transverse magnetic mode excitation, we give the two components of the electric field deduced from the Maxwell equations. The magnetic field By for the TM excitation has the same form as the perpendicular electric field Ey for the TE excitation.1 See the above equations.
The polarisation of the transmitted wave in the second medium is obtained from the Snell-Descartes law.
We give the continuity equations in the multi-layer system:
at each interface.
for i=1,2,3 for each interface in the multi-layer.
We extract some factors from the matrix and call them I, II, III, IV, V, VI and VII:
With:
: j* is the conjugate of j
with
with
The coefficients
are given by the following relationship:
Results:
We take an incidence angle close to the critical angle (optimum of transmission in the TE mode). See reference.1
=520
Figure 2 The perpendicular component EZ of the electric field (V/m).
Figure 3 The parallel component EX of the electric field (V/m).
Figure 4 The total electric field ET in the atomic mirror function of the transverse coordinate z.
We notice that the electric field is bigger in the gap and then decreases in the vaccum where it is smaller than in the prism.
The transmission factor is given by:4
Figure 5 The transmission factor in the atomic mirror.
We conclude that there is no enhancement in the vaccum for the electric field and there is no technological progress or advantage for this kind of excitation.1,5-7