Final Report Summary - TRICEPS (Time-resolved Ring-Cavity-Enhanced Polarization Spectroscopy: Breakthroughs in measurements of a) Atomic Parity Violation, b) Protein conformation and biosensing and c) surface and thin film dynamics)
The TRICEPS project aimed to make significant breakthoughs in the important optical methods of polarimetry (typically used to measure molecular chirality), and ellipsometry (typically used to probe the structure of thin films at interfaces, such as in the semiconductor industry), by finding ways to enhance the signals of these single-pass techniques through the multiple passes (of about 1000) afforded by optical cavities. The successful implementation of these goals is given below:
Chirality is a fundamental property of life, making chiral sensing and analysis crucial to numerous scientific subfields of biology, chemistry, and medicine, and to the pharmaceutical, chemical, cosmetic, and food industries, constituting a market of about 1$ billion and growing. The most widely used techniques for the analysis of chiral samples are the polarimetric techniques of optical rotary dispersion (ORD) and circular dichroism (CD). However, ORD and CD signals are typically very small and are limited by spurious birefringence and poor background subtraction procedures, which places severe constraints on detection sensitivity (~1 micro-g/ml, or ~0.1 micro-mol/dl), and time resolution (~1 min).
Through the project TRICEPS, the Rakitzis group at FORTH in Heraklion has introduced a new form of Chiral-Cavity-based Polarimetry (CCP) for chiral sensing, which has several advantages compared to commercial instruments: (a) The OR and CD signals are enhanced by the number of cavity passes (typically about 1000); (b) birefringent backgrounds are suppressed by a large applied intra-cavity Faraday Effect; (c) rapid signal reversals (effected by reversing the Faraday Effect) give absolute polarimetry measurements, not requiring sample removal for a null-sample measurement. We have demonstrated the power of these advantages by detecting the ORD signals of chiral samples in open air and in evanescent waves at prism surfaces, for the first time: “Evanescent-wave and ambient chiral sensing by signal-reversing cavity-ringdown polarimetry” Sofikitis et al. Nature 514, 76 (2014). The signal-reversing methods were able to isolate the small chiral signals from much larger non-chiral backgrounds. Steps towards commercialization of the TRICEPS polarimeter are proceeding with ongoing patent applications, a recently awarded Proof-of-Concept ERC grant, and direct interest from companies that construct polarimeters for the pharmaceutical industry. The TRICEPS polarimeter is expected to significantly improve polarimetric meaurements in numerous fields, including measurements of protein structure, lowering detection limits in analytical chemistry, and testing fundamental symmetries in physics (such as atomic parity nonconservation, for which an experiment on atomic iodine is in progress in our laboratories).
Ellipsometry is a widely used technique for thin-film characterization and biosensing, however commercial instruments typically require a few seconds to perform a measurement. We have developed cavity-based method that enhances the signal by about 1000 times, and is able to perform a measurement within a microsecond (about 6 orders of magnitude faster); furthermore, using a 1 MHz repetition rate laser and field-programmable-gate-array-based data acquisition, we have demonstrated running ellipsometric measurements with microsecond resolution, which allow the study of fast surface processes. The US patent “Intra-cavity ellipsometer system and method” (# 8941831) was awarded in January 2015.
Chirality is a fundamental property of life, making chiral sensing and analysis crucial to numerous scientific subfields of biology, chemistry, and medicine, and to the pharmaceutical, chemical, cosmetic, and food industries, constituting a market of about 1$ billion and growing. The most widely used techniques for the analysis of chiral samples are the polarimetric techniques of optical rotary dispersion (ORD) and circular dichroism (CD). However, ORD and CD signals are typically very small and are limited by spurious birefringence and poor background subtraction procedures, which places severe constraints on detection sensitivity (~1 micro-g/ml, or ~0.1 micro-mol/dl), and time resolution (~1 min).
Through the project TRICEPS, the Rakitzis group at FORTH in Heraklion has introduced a new form of Chiral-Cavity-based Polarimetry (CCP) for chiral sensing, which has several advantages compared to commercial instruments: (a) The OR and CD signals are enhanced by the number of cavity passes (typically about 1000); (b) birefringent backgrounds are suppressed by a large applied intra-cavity Faraday Effect; (c) rapid signal reversals (effected by reversing the Faraday Effect) give absolute polarimetry measurements, not requiring sample removal for a null-sample measurement. We have demonstrated the power of these advantages by detecting the ORD signals of chiral samples in open air and in evanescent waves at prism surfaces, for the first time: “Evanescent-wave and ambient chiral sensing by signal-reversing cavity-ringdown polarimetry” Sofikitis et al. Nature 514, 76 (2014). The signal-reversing methods were able to isolate the small chiral signals from much larger non-chiral backgrounds. Steps towards commercialization of the TRICEPS polarimeter are proceeding with ongoing patent applications, a recently awarded Proof-of-Concept ERC grant, and direct interest from companies that construct polarimeters for the pharmaceutical industry. The TRICEPS polarimeter is expected to significantly improve polarimetric meaurements in numerous fields, including measurements of protein structure, lowering detection limits in analytical chemistry, and testing fundamental symmetries in physics (such as atomic parity nonconservation, for which an experiment on atomic iodine is in progress in our laboratories).
Ellipsometry is a widely used technique for thin-film characterization and biosensing, however commercial instruments typically require a few seconds to perform a measurement. We have developed cavity-based method that enhances the signal by about 1000 times, and is able to perform a measurement within a microsecond (about 6 orders of magnitude faster); furthermore, using a 1 MHz repetition rate laser and field-programmable-gate-array-based data acquisition, we have demonstrated running ellipsometric measurements with microsecond resolution, which allow the study of fast surface processes. The US patent “Intra-cavity ellipsometer system and method” (# 8941831) was awarded in January 2015.