Integrated vibrational spectroscopy enhanced by surface acoustics

Vibrational spectroscopy reveals the microstructural and mechanical properties of materials. It is a powerful tool for revealing molecular structures, dynamic characteristics of materials, and the biomechanical properties of cells or viruses. To enhance the sensitivity and overcome limitations in detecting vibrational signals from micro- and nanoparticles, researchers are exploring optical microcavities. Optical microcavities strongly confine light and localize optical evanescent fields at the subwavelength scale. This characteristic has primarily driven sensing research to focus on near-field interactions. However, near-field contact-based sensing results in surface contamination, increased losses, and reduced quality factor of the microcavity, making it challenging to maintain sensing performance during continuous measurements. Recent studies have shown promise in using acoustic waves to enhance the microcavity’s far-field detection capabilities. Further optimization in the acoustic dimension is required to improve sensitivity and broaden the detection range. Here, we demonstrate the manipulation of surface wave modes in an integrated photonic system. Utilizing the intriguing phenomenon of anticrossing, we achieve enhanced acoustic fields, enabling real-time detection of particle vibration spectra over a 300-μm far-field range. This integrated approach mitigates microcavity quality factor losses and significantly expands the sensing range, enhancing the application potential of vibration spectroscopy.