Weak value amplified optical activity measurements

Fraunhofer Institute for Physical Measurement Techniques, 79110 Freiburg,Germany.
Optics Express (Impact Factor: 3.49). 08/2011; 19(17):16508-17. DOI: 10.1364/OE.19.016508
Source: PubMed


We present a new form of optical activity measurement based on a modified weak value amplification scheme. It has recently been shown experimentally that the left- and right-circular polarization components refract with slightly different angles of refraction at a chiral interface causing a linearly polarized light beam to split into two. By introducing a polarization modulation that does not give rise to a change in the optical rotation it is possible to differentiate between the two circular polarization components even after post-selection with a linear polarizer. We show that such a modified weak value amplification measurement permits the sign of the splitting and thus the handedness of the optically active medium to be determined. Angular beam separations of Δθ ∼ 1 nanoradian, which corresponds to a circular birefringence of Δn ∼ 1 × 10(-9), could be measured with a relative error of less than 1%.

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    • "The same principle has been applied to identify the number of graphene layers of a sample [7]. Furthermore, WVA has been successfully implemented to measure angular deflections of a mirror down to 400 ± 200 frad and the linear travel of a piezo actuator down to 14 ± 7 fm [8], angular beam separations of ∼ 1 nanoradian, which corresponds to a circular birefringence of ∆n ∼ 1 × 10 −9 [9], to measure changes in optical frequency of a continuouswave , single-mode laser beam as small as 129±7 kHz [10], to detect temperature changes with a sensitivity of ∼ 0.2 mK with an easy-to-use laser-based thermostat [11], and to estimate a phase shift of ∼ 10 mrad using a commercial light-emitting diode [12]. "
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    ABSTRACT: Weak value amplification, a 25 five years old technique used in metrology applications, has proved to be highly successful for measuring extremely tiny changes of a variable of interest. In spite of this, in what sense the technique is useful is still a question of debate. Here we show, making use of simple results taken from quantum estimation theory, what is the main contribution of the idea of weak value amplification to metrology. On the one hand, since the technique makes use of linear-optics unitary operations, it cannot modify the statistics of photons involved, and therefore, it cannot be better than other standard techniques used. On the other and, the scheme enhances the overall sensitivity of the detection scheme, making possible the discrimination of smaller changes of the variable of interest than other standard techniques could allow.
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    ABSTRACT: In this letter, we investigate the circular differential deflection of a light beam refracted at the interface of an optically active medium. We show that the difference between the angles of deviation of the two circularly polarized components of the transmitted beam is enhanced manyfold near total internal reflection, which suggests a simple way of increasing the limit of detection of chiro-optical measurements.
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