Nanolayer characterization through wavelength multiplexing of a microsphere resonator.
We optically characterize nanolayer (<150 nm) formation in situ on a silica microsphere in an aqueous environment by simultaneously following the shifts of whispering-gallery modes at two wavelengths. This approach was inspired by layer perturbation theory, which indicates that these two measurements can be used to determine independently both the thickness and the optical dielectric constant. The theory is verified for extreme cases and used to characterize a biophysically relevant hydrogel nanolayer with an extremely small excess refractive index of 0.0012.
Noto
Mayumi
M
Microparticle Photophysics Laboratory, Polytechnic University, 6 Metrotech Center, Brooklyn, New York 11201, USA.
Vollmer
Frank
F
Keng
David
D
Teraoka
Iwao
I
Arnold
Stephen
S
D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods; D020099:Coated Materials, Biocompatible / Q000032:analysis / Q000737:chemistry*; D020100:Hydrogels / Q000032:analysis / Q000737:chemistry; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D008863:Microspheres; D049329:Nanostructures / Q000032:analysis / Q000737:chemistry*; D011107:Polylysine / Q000032:analysis / Q000737:chemistry*; D012031:Refractometry / Q000379:methods; D013057:Spectrum Analysis / Q000379:methods*
D020099:Coated Materials, Biocompatible; D020100:Hydrogels; D011107:Polylysine