Optical Media

Molecularlv Doped Thermotropic Liquid Crystalline Polymer. The idea of the nonlinear optical medium which is the subject of this paper results from a synthesis of the ideas of the discussion above and a few concepts from nonlinear optical molecular and crystal physics. As discusssed several places in this volume, it is known that certain classes of molecules exhibit tremendously enhanced second-order... 

A novel second-order nonlinear optical medium which should offer considerable fabrication flexibility has been described. The physics of alignment of the highly nonlinearly polarizable moiety was discussed. However, observation of complex dynamical and thermal behavior indicates that an important role is played by the polymer liquid crystalline host. Additional properties of modified members of this family of lc polymers were consequently investigated. The explanations of guest alignment stabilization and thermal dependence of the alignability remain unresolved issues. 

Figure 72. Simplified diagramm showing nearly normal incidence of a beam of light (Lfl from an optical medium with refractive index nl through a thin solid film of thickness d with refractive index n2...

Thus a plot of polarization as a function of the applied field is a straight line whose slope is the linear polarizability, a, of the optical medium (Figure lc). If the field oscillates with some frequency, (i.e., electromagnetic radiation, light), then the induced polarization will have the same frequency if the response is instantaneous (Figure la). Polarization is a vector quantity with both direction and magnitude. 

The oscillating electric field of light affects all charges in the optical medium, not only the electron. For materials that contain electric dipoles, such as water molecules, the dipole themselves stretch or reorient in the applied field. In ionic materials, the ions move relative to one another (Figure 3). Dipolar and ionic motions involve nuclear reorientation. 

Evaporated PDA(12-8) film was used as a nonlinear optical medium in a layered guided wave directional coupler. The directional coupling phenomenon happens in two adjacent waveguide by periodical energy transfer. The theory of linear directional coupler was exactly established [11]. It can be reduced to coupled mode equations ... 

The refractive index n is not regarded as a constant as in Fresnel s equation, but as an abbreviation for k c/co. This can be understood as follows in an optical medium the phase velocity of light is c/n, where c is the velocity of light in the vacuum. Now the phase velocity is connected with wavelength and frequency through the relation c/n = v. On the other hand k = 27t/A. This leads to c/n = u/k and finally... 

The previous paragraphs have been concerned with linear optical properties. Throughout the long history of optics, and indeed until relatively recently, it was thought that all optical media were linear. The assumption of linearity of the optical medium has far-reaching consequences ... 

Light cannot interact with light two beams of light in the same region of a linear optical medium can have no effect on each other. Thus light cannot control light. 

The refractive index, and consequently the speed of light in an optical medium, does change with the light intensity. 

Figure 4.20 A sinusoidal electric field of angular frequency u> in a second-order nonlinear optical medium creates a polarization with component at 2tn( second-harmonic) and a steady (dc) component...

The interference between a fundamental wave, and its SH, leads to the presence of a polar field, E t) = + El J t), inside the optical medium. 

Broad tuning range (0.4-5 j,m). This results from the dynamic grating formed by the acoustic wave in the acousto-optic medium. 

The optical medium must be homogeneous. Turbid solutions give deviations from Beer s law. Such deviations occur in two-phase systems insufficiently homogenized by protective colloids. 

At this juncture we have in place a formalism that fully accounts for the refractive and dissipative modifications of the fundamental fields due to the dispersive electronic properties of the optical medium. This has been achieved not by any phenomenological or other ad hoc approach, but from first principles, using the theoretical methods of molecular QED. As a result, the necessary local field corrections in condensed media naturally emerge from the detailed form of the auxiliary field operators, obviating the need to encompass them indirectly in terms of macroscopic bulk susceptibilities, as is necessary in the semiclassical theory. 

If the incidence angle of / -polarised radiation is equal to the Brewster angle aB, the reflectivity from the pure (i.e., slick-free) water surface is close to zero. As a consequence, the water surface appears to be dark. In the presence of a film-forming substance, however, the slick patches represent a different optical medium that gives rise to a measurable reflectivity, which in turn makes the slick domains visible by their lighter appearance. This effect can be recorded by a Charge-Coupled-Device [CCD]-camera. 

We consider a nonlinear optical medium, consisting of polyatomic molecules interacting with a classical external electromagnetic field by a dipolar interaction. The total Hamiltonian of the system is... 

When two laser beams (Eu nonlinear optical medium, the nonlinear dielectric polarization, PNL, exhibits the following forced oscillations,... 

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