The FORTH group has worked towards finding the best method for measurement of ultrasensitive chiral optical rotation using a ring-cavity-based polarimeter. Three methods were identified in the 1st year, namely the: (a) amplitude modulation method, (b) CW-CCW phase-shift method, and (c) frequency beating method. Preliminary work showed that these methods are not good candidates for achieving the ultrahigh sensitivity goals of ULTRACHIRAL. Therefore, we have devised and implemented a 4th method, named Sideband Phase-Shift (SPS) method, which has recently shown all the qualities needed for ultrasensitive measurements. Overcoming such a large noise source is a huge challenge. In contrast, the SPS method involves beating sidebands of the same beam (CW and CCW separately), and avoids recombination optics and the recombination paths that cause large phase noise.
During the first year, the MAINZ group has developed a system of rotating permanent magnets that can invert the direction of the magnetic field within some seconds. In the second year, the group has moved rapidly towards creating a stand-alone prototype, and they have already demonstrated real-time inline measurements of chiral gasses and chiral gas mixtures using a chiral CRD apparatus. They have demonstrated sensitivities of a few μrad.
The main goal of the EPFL group is (in collaboration with the UOC-MS group) to devise nanophotonic structures that can enhance chiral signals (optical rotation). It is also an interest that these structures have sufficient transparencies which can allow them to be used inside optical cavities (while exhibiting vanishing chiroptical noise). This way, chiral measurements can be enhanced both by the number of passes inside the optical cavity and by the enhancement due to the photonic structures. The initial results on investigation of optical nanostructures for enhancing chiral sensing have been published in the journal ACS photonics [E. Mohammadi et al., ACS photonics 5 2669 (2018)].
The EXETER group is already at a stage where the plasmon-enhanced WGMM detector can detect single chiral molecules (though not yet with strong sensitivity to chirality). Some chiral signatures may be already suggested in their measurements. The UOC-MS group has synthesized polymers with giant Verdet constant (10^3 times larger than fused silica, ~30 time larger than TGG, the magneto-optic material used in the macroscopic cavities). This material is in the process of testing, and the next steps will be to coat one hemisphere of the WGM microresonator and measure the corresponding Faraday splitting, which will be the first measurement of an intracavity Faraday Effect in an WGMM.
The UOXF group has been tasked with developing two cavity-enhanced polarimeters. One of these operates in the near-IR and the other will operate in the mid-IR; both will be used for studies of interfaces and condensed phase samples. The group has already achieved cavity-enhanced pathlengths on the order 10 km at 1335 nm and they are developing a CAD designed holder for the TGG and permanent magnets which allows flipping the magnetic fields. The group is currently working in demonstrating the capabilities of their cavity-enhanced polarimeter using a calcite crystal.
The UOC-MD group has created protocols for the extraction and/or synthesis of chiral standards. They have extracted the chiral compounds Ilicic acid, costic acid, Verbascoside and Forsythoside B. They have measured the optical rotation of these compounds in solution, in various concentrations, using commercial polarimeters, and encountered problems related with the limitations of existing technology.
Plans for the development of new hardware were abandoned, as discussed at the first-year project review meeting, where it was agreed to purchase a newly available commercial device which met performance specifications for WGMM-CCP (WP5) and provides an integrated FPGA for development of analysis code needed for the precommercial CCP prototype (WP6).
The MPIC group, besides collaborating with the MAINZ group and giving input for the design of the portable CCP instrument, they have initiated the study of chiral compound emission in tempered forests (Bordeaux), in mixed Mediterranean forest and in a Tropical forest (Amazon) using automated sampling devices and adsorbent filled cartridges.
