Light field

The coefficients a t) and b t) are subject to the constraint that + h(0P = 1 If we couple this system to a light field, represented as F= cosCot), then we may write tire TDSE in matrix fonn as... 

This representation is slightly inconvenient since Ey and 2 in equation (Al.6.56) are explicitly time-dependent. For a monocln-omatic light field of frequency oi, we can transfonn to a frame of reference rotating at the frequency of the light field so that the vector j s a constant. To completely remove the time dependence... 

Flere, is the static polarizability, a is the change in polarizability as a fiinction of the vibrational coordinate, a" is the second derivative of the polarizability with respect to vibration and so on. As is usually the case, it is possible to truncate this series after the second tenn. As before, the electric field is = EQCOslnvQt, where Vq is the frequency of the light field. Thus we have... 

Figure Cl.4.4. Schematic diagram showing how the two 2 levels of the ground state couple to the spatially varying polarization of the Tin-periD-iin standing wave light field (after 1171).

We assume that tlie light field is detuned to tlie red of tire J —> J atomic resonance frequency. 

Suominen K-A 1996 Theories for cold atomic collisions in light fields J.Phys.B At.Mol.Opt.Phys. 29 5981-6007... 

Altliough a complete treatment of optical phenomena generally requires a full quantum mechanical description of tire light field, many of tire devices of interest tliroughout optoelectronics can be described using tire wave properties of tire optical field. Several excellent treatments on tire quantum mechanical tlieory of tire electromagnetic field are listed in [9]. 

Given tire general description of tire electromagnetic field, let us explore the sources available for optoelectronics. The one primary light source for optoelectronic device and system architectures is tire laser. The laser [10] is tire source of choice simply because if we want to control light fields tliey need to be well defined at tire start and tire laser is tire most... 

Calculations within tire framework of a reaction coordinate degrees of freedom coupled to a batli of oscillators (solvent) suggest tliat coherent oscillations in the electronic-state populations of an electron-transfer reaction in a polar solvent can be induced by subjecting tire system to a sequence of monocliromatic laser pulses on tire picosecond time scale. The ability to tailor electron transfer by such light fields is an ongoing area of interest [511 (figure C3.2.14). 

As it stands, the picture of dynamics from Eq. (29) is derived from the interaction of molecules with a continuous light source, that is, the system is at equilibrium with the oscillating light field. It is also valid if the light source is an infinitely short laser pulse, as here all frequencies are instantaneously excited. 

Problems arise if a light pulse of finite duration is used. Here, different frequencies of the wave packet are excited at different times as the laser pulse passes, and thus begin to move on the upper surface at different times, with resulting interference. In such situations, for example, simulations of femtochemistry experiments, a realistic simulation must include the light field explicitely [1]. 

Doppler broadening arises from the random thermal agitation of the active systems, each of which, in its own test frame, sees the appHed light field at a different frequency. When averaged over a Maxwellian velocity distribution, ie, assuming noninteracting species in thermal equilibrium, this yields a line width (fwhm) in cm C... 

A polarimeter. The sample lube contains an optically active compound. The analyzing filter has been tuned clockwise to restore the light field and measure the rotation caused by the sample. 

Figure 2.2 Optical probe of surface-enhanced microscopy proposed byj. Wessel. A metallic nanoparticle attached to a glass substrate confines and enhances the light field.

Figure 2.5 A tip-enhanced near-field Raman microscope which we have developed. The microscope is based on AFM for control of the metallic nano-tip, an inverted optical microscope for illumination/collection of the light field and a polychromator for measurement of the Raman signal.

Rubinov AN, Tomin VI, Zhivnov VA (1973) A shift of fluorescence spectrum of molecules in nonresonance light field. Opt Spectros 35 778-781... 

---