Single Molecule Raman Detection with a Composite

Single Molecule Raman Detection with a Composite Microresonator and Metal Nanocavity System Xudong Fan (University of Missouri – Columbia) Ag nanoclusters Sample Target analyte

LCORR WGM field profile Raman signal

Laser light

Resonant surface plasmons

Concept: Raman signal is enhanced multiplicatively by both metal nanoclusters and a ring resonator LCORR: Liquid Core Optical Ring Resonator

Silver Nanoclusters

Fabrication of Liquid Core Optical Ring Resonator (LCORR) (A)

Preform

LCORR

Heating zone (C)

SEM image

5 μm

(C)

(B)

Experimental Setup

785 nm laser sample

Fiber probe

To spectrometer

Fiber taper

Fiber probe

200 μm Fiber taper or waveguide

LCORR LCORR

photodetector

(A)

Radiative scattering

(B)

400

1510 cm-1

500

1360 cm-1

600

1310 cm-1

Counts per minute

Experimental Results

300 200 1100 1200 1300 1400 1500 1600 1700

Wavenumber (cm-1) Analyte: R6G at 400 pM The Raman signal is likely from only a few hundreds of R6G molecules