Amplified measurement of weak optical activity using a spin-phase-gradient beam

Abstract

Development of alternate techniques to polarimetry for the measurement of weak optical rotation, with improved sensitivity, is becoming increasingly important as one understands the role of chirality in drug design and synthesis and the fundamentals of chiral light-matter interaction. We demonstrate here an optical amplification scheme using a spin-phase-gradient beam to measure ultra-small optical rotation angle (4 mdeg), with a sensitivity of 220 μdeg/μm, due to dilute (mg/mL) dextro-rotatory sugar solution. A Soleil-Babinet compensator is used to generate a tunable spin-phase-gradient beam which enables us to achieve high measurement sensitivities. Theoretical formalism of the technique leads us to the possibility to realize much higher measurement sensitivity of up to 10 μdeg/μm by tuning-in the experimental parameters.

Ultra-sensitive single-beam atom-optical magnetometer using weak measurement method

“…Here we refer the state of polarization of the Gaussian beam as the observable and its transverse momentum vector with canonical conjugate transverse position as the apparatus. The SBC is used to couple the polarization state and the momentum vector resulting in inhomogeneously polarized Gaussian beam, also known as spin-orbit beam and has been used to measure weak optical chirality [21,22].…”

“…2: Rotation angle measured as a function of longitudinal magnetic field using balanced polarimetry method and theoretical fit as the apparatus. The SBC is used to couple the polarization state and the momentum vector resulting in inhomogeneously polarized Gaussian beam, also known as spin-orbit beam and has been used to measure weak optical chirality [21,22].…”

Amplified sensing of optical phase difference through the phase of the resultant field

“…It should be kept in mind that, due to the limited time response of the available detectors in the optical regime of electromagnetic spectrum, we only measure the intensity or the energy of the field. The weak interaction is sensed through the shift in centroid of the intensity of the post selected state [8][9][10][11]. The phase of the output state is rarely looked upon.…”

“…In general, an optical beam of light is specifically synthesized whose centroid shift upon weak interaction is shown to enhance the sensing capability. The scheme requires only the detection of the intensity profile of the beam for calculating the centroid, leading to a variety of sensing applications [8,9]. At the same time, it should be noted that the scheme can be applied to situations where one could afford to use optical field having beam-like characteristics such as spatial coherence and spatial confinement within the sensor area.…”