Left-handed light

The handedness of light is defined by the receiver i.e. light coming towards the observer), whilst the material handedness is defined by the chirality moving away from the observer. For this reason, left handed materials have opposite chirality to, and reflect, left-handed light. 

P.W. Milonni, Fast Light, Slow Light and Left-Handed Light (Taylor Francis, Abingdon, Oxford, 2004)... 

Pig. 5. Comparison of the qi expectation value of the uncoupled QCMD bundle ([g]e o) and full QD ( q)qd) for the test system for e = 1/100 (pictures on top) and e = 1/500 (below). Initial data as in Fig. 3. The shaded domain indicates the funnel between the two curves Qbo and geo (cf. Thm. 5). The light dashed line shows Hagedorn s limit solution qna and the dense lines (q )Qo (left hand pictures) and [ ]e s (right hand pictures). 

Enantiomers. Two nonsuperimposable structures that are mirror images of each other are known as enantiomers. Enantiomers are related to each other in the same way that a right hand is related to a left hand. Except for the direction in which they rotate the plane of polarized light, enantiomers are identical in all physical properties. Enantiomers have identical chemical properties except in their reactivity toward optically active reagents. 

Levorotatory (Section 9.3) An optically active substance that rotates the plane of polarization of plane-polarized light in a left-handed (counterclockwise) direction. 

When a material exhibits different indices of refraction for the right- and left-hand components of the circular vectors, the velocities in these directions are different and the plane of polarized light undergoes rotation. For the left- and right-hand vectors, the indices of refraction are... 

Photoluminescence (PL) in the polysilanes is well documented,34b,34c and for the poly(diarylsilane)s occurs typically with a small Stokes shift and almost mirror image profile of the UV absorption.59 This is due to the similarity of the chromophore and fluorophore structures in the ground and excited states, respectively, which is a result of the fact that little structural change occurs on excitation of the electrons from the a to the a orbitals. As PL is the emissive counterpart to UV, the emissive counterpart to CD is circularly polarized pho-toluminescence (CPPL). Where the fluorophore is chiral, then the photoexcited state can return to the ground state with emission of circularly polarized light, the direction of polarization of which depends on the relative intensities of the right-handed and left-handed emissions (/R and /l, respectively), which in turn depends on the chirality of the material, or more accurately, the chirality... 

Figure 9.9 Simulated normalized line shapes of -polarized (a-c) and p-polarized (if-/) second-harmonic signals for quarter waveplate measurements (a) and (if) hypothetical achiral surface (hs = 0.5 fp = 0.75, gp = —0.5), (b) and (if) hypothetical chiral surface with in-phase chiral coefficient (fs = 0.75, hs = 0.5 fp = 0.75, gp = —0.5, hp = 0.25), (c) and (/) hypothetical chiral surface with out-of-phase chiral coefficient ( fs = 0.75 0.25i, hs = 0.5 fp = 0.75, gp = —0.5, hp = 0.25z). Upper (solid line) and lower (dashed line) sign in expansion coefficients correspond to two enantiomers. Rotation angles of 45° and 225° (135° and 315°) correspond to right-hand (left-hand) circularly polarized light and are indicated for one of enantiomers with open and filled circles, respectively.

Figure 9.20 Intensity of s-polarized second-harmonic signal generated in transmitted direction for glass-side incidence as function of rotation angle of quarter waveplate. Note significant difference in response for right- (45° and 225°) and left-hand (135° and 315°) circularly polarized light. Points represent experimental data, solid line fit to the model described in Section 3 with nonvanishing g, and the dashed line the fit with vanishing g.

The first example of the deliberate separation of optically active molecules is appropriate as an example of physical separation in the clearest sense of the term. The molecules are referred to as optically active because polarized light interacts differently with right- and left-handed molecules. In the case of simple diastereomers the RR and SS forms are enantiomers while the RS and SR forms are not. The separation of the latter and former was first done under a microscope using crossed polarizers and the crystals which were seen were separated from those that caused little or no rotation of plane-polarized light by hand using tweezers. A truly physical separation of chemical species using a physical property of chemical origin ... 

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