Ultracompact Lab-on-a-Chip Device for Surface-Enhanced Coherent Anti-Stokes Raman Scattering

This paper introduces an ultracompact lab-on-a-chip device with a size of $8\times 0.8~\mu \text{m}^{\mathrm{ 2}}$ for surface-enhanced coherent anti-Stokes Raman scattering. This device comprises of a unique hybrid plasmonic-photonic vertical coupler, for light-coupling between the device and a light source, and a heptamer plasmonic nanotweezer for trapping and manipulation of nanoparticles. The coupler with its nanoscale size of $0.73\times 0.8~\mu \text{m}^{\mathrm{ 2}}$ offers maximum coupling efficiency and directivity of −4.2 dB and 17.8 dB with a 3 dB bandwidth across the wavelength range of $\sim {1} - {1}.{13} \, \mu \text{m}$ . Based on a finite element method, it is theoretically shown that the tear-drop based nanotweezer can empower the device to yield a very high Raman gain of $\geq {10}^{{17}}$ , making the detection at the single-molecule level possible. The proposed device can exhibit low damage to bioparticles through the use of near infrared wavelengths range with lower energy photons. Due to its short optical path, this device is expected to improve the Raman signal to noise ratio by reducing the level of background in-coherent Raman signals. Finally, thanks to its configuration, this device can enable the creation of parallel measurement channels, paving the way toward the development of high-throughput and mass-produced biosensors.