High Sensitivity Frequency Modulation Spectroscopy and the Path to Single Molecule Detection

Abstract

Advances in optical spectroscopy rely on improved detection techniques that reduce noise to fundamental detection limits. When properly applied, frequency modulation laser spectroscopy (FM spectroscopy or FMS) approaches the quantum limit for detection. Having demonstrated that double modulation FMS could achieve such sensitivity in absorption spectroscopy, researchers raced to the goal of measuring the absorption of an individual molecule. In 1989, Moerner and Kador performed the first optical detection and probing of single dopant molecules in solids, spawning the field of single-molecule spectroscopy. In this Perspective, we trace the development of FMS from its initial demonstration in 1979 to Moerner’s remarkable achievement with an emphasis on the double modulation methods needed to achieve high sensitivity measurement of very small absorptions.

Mapping the Optomechanical Coupling Mediated by Light among Mechanical Resonators Including Multilayer Cavity and Molecules

“…The mirrors establish symmetry, enabling the waves to travel within the cavity; in addition, because the mirrors have a modulus close to zero, the waves behave like standing ones. The Fabry–Perot cavity displays a high quality factor Q and a small modal volume V / V 0 , and for this reason, they play a decisive role in quantum electrodynamics investigation and light/matter interaction. − The high factor derives from a line width that is narrower than the vibrational frequency of the molecular species and imposes the crucial hierarchy in a resolved sideband regime where the mechanical frequency exceeds the optical line width as a fundamental condition . An important family of Fabry–Perot systems is constituted by the metal/dielectric/metal stack layer cavity, which is frequently used in cutting-edge plasmonics research.…”

“…9−11 The high factor derives from a line width that is narrower than the vibrational frequency of the molecular species and imposes the crucial hierarchy in a resolved sideband regime where the mechanical frequency exceeds the optical line width as a fundamental condition. 12 An important family of Fabry−Perot systems is constituted by the metal/dielectric/metal stack layer cavity, which is frequently used in cutting-edge plasmonics research. These systems display resonant behavior when the cavity thickness is comparable to the wavelength, while to optimize the quality factor, the metallic mirror thickness must be kept large.…”