Abstract
Optical evanescent sensors can non-invasively detect unlabeled nanoscale objects in real time with unprecedented sensitivity, enabling a variety of advances in fundamental physics and biological applications. However, the intrinsic low-frequency noise therein with an approximately 1/f-shaped spectral density imposes an ultimate detection limit for monitoring many paramount processes, such as antigen-antibody reactions, cell motions and DNA hybridizations. Here, we propose and demonstrate a 1/f-noise-free optical sensor through an up-converted detection system. Experimentally, in a CMOS-compatible heterodyne interferometer, the sampling noise amplitude is suppressed by two orders of magnitude. It pushes the label-free single-nanoparticle detection limit down to the attogram level without exploiting cavity resonances, plasmonic effects, or surface charges on the analytes. Single polystyrene nanobeads and HIV-1 virus-like particles are detected as a proof-of-concept demonstration for airborne biosensing. Based on integrated waveguide arrays, our devices hold great potentials for multiplexed and rapid sensing of diverse viruses or molecules.
Highlights
We propose an ultralow-noise optical sensing scheme, which can effectively suppress the 1/f noise, via an integrated heterodyne interferometer and an up-conversion amplifying technique
When single nanoparticles are deposited into the joint area, due to the elastic scattering, a part of the probe light is collected by the local waveguide via evanescent-wave coupling, which interferes with the local light (Fig. 1b)
We have demonstrated a 1/f-noise-free sensing scheme with an integrated heterodyne interferometer
Summary
Beat-frequency envelop together with a reference light is subsequently detected by a balanced photodetector where the laser noise can be significantly suppressed[21] In this scheme, the scattered signal is boosted by a dual amplification strategy. 1 kHz that are introduced by the electrical elements FEM simulation, the power of probe light collected by the local waveguide Pcol is calculated as a function of particle size when the scatterer is placed in the joint sensing area. The ultralow-noise sensor is realized with the high-density integrated waveguide arrays via a commercial silicon photonics foundry process (Fig. 5a) This feature enables to explore multiplexed and rapid sensing. The 1/e decay time is 0.95 s (2.96 s) for the nine-waveguide (one-waveguide) configurations, which indicates a 3-fold enhancement in capture efficiency
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