Molecular-Chirality Sensor using an Electro-Optic-Polymer-Based Circular-Polarization Modulator

The proposed innovation is a miniaturized circular-polarization-state (CPS) modulator for producing a laser beam that alternates in time between left- and right-hand-circular (LHC/RHC) states of polarization, which would replace bulky photoelastic, liquid-crystal, and inorganic-crystal polarization modulators. Innovative is its use of a single-mode polymer waveguide with a controllable amount of birefringence, via the electro-optic effect, to adjust the polarization state of a laser beam. It has a very small mass, low power consumption, and very compact size. Other desirable attributes are its use of no moving parts, no expensive birefringent crystals (e.g., calcite), low voltages (~10 V), and a single high-speed driving-voltage source. Furthermore, it can operate at arbitrary speeds up to 101s of GHz and has an adjustable wavelength of operation (i.e., 700-1600 nm). The innovation will form the central portion of sensors for detecting chirality. A signature of chirality is natural optical activity, where light passing through chiral materials exhibits circular dichroism and optical rotatory dispersion. Related effects can also occur in reflected light, where for instance the magnitude of the reflectivity can be different for LHC and RHC light. Most biological material is chiral. Thus the proposed modulator would aid in target recognition, since a remote sensor based upon it would be able to discern biological materials from typically achiral man-made materials used in camouflage. Key to detecting chirality is a source of both LHC and RHC light of high purity, which the proposed innovation provides.