Bennett B. Goldberg

Optical sensing of biomolecules using microring resonators

A biosensor application of vertically coupled glass microring resonators with Q/spl sim/12 000 is introduced. Using balanced photodetection, very high signal to noise ratios, and thus high sensitivity to refractive index changes (limit of detection of 1.8/spl times/10/sup -5/ refractive index units), are achieved. Ellipsometry and X-ray photoelectron spectroscopy results indicate successful modification of biosensor surfaces. Experimental data obtained separately for a bulk change of refractive index of the medium and for avidin-biotin binding on the ring surface are reported. Excellent repeatability and close-to-complete surface regeneration after binding are experimentally demonstrated.

High spatial resolution subsurface microscopy

We present a high-spatial-resolution subsurface microscopy technique that significantly increases the numerical aperture of a microscope without introducing an additional spherical aberration. Consequently, the diffraction-limited spatial resolution is improved beyond the limit of standard subsurface microscopy. By realizing a numerical aperture of 3.4, we experimentally demonstrate a lateral spatial resolution of better than 0.23 μm in subsurface inspection of Si integrated circuits at near infrared wavelengths.

Label-free and dynamic detection of biomolecular interactions for high-throughput microarray applications

Direct monitoring of primary molecular-binding interactions without the need for secondary reactants would markedly simplify and expand applications of high-throughput label-free detection methods. A simple interferometric technique is presented that monitors the optical phase difference resulting from accumulated biomolecular mass. As an example, 50 spots for each of four proteins consisting of BSA, human serum albumin, rabbit IgG, and protein G were dynamically monitored as they captured corresponding antibodies. Dynamic measurements were made at 26 pg/mm2 SD per spot and with a detectable concentration of 19 ng/ml. The presented method is particularly relevant for protein microarray analysis because it is label-free, simple, sensitive, and easily scales to high-throughput.

Biaxial Strain in Graphene Adhered to Shallow Depressions

Measurements on graphene exfoliated over a substrate prepatterned with shallow depressions demonstrate that graphene does not remain free-standing but instead adheres to the substrate despite the induced biaxial strain. The strain is homogeneous over the depression bottom as determined by Raman measurements. We find higher Raman shifts and Gruneisen parameters of the phonons underlying the G and 2D bands under biaxial strain than previously reported. Interference modeling is used to determine the vertical position of the graphene and to calculate the optimum dielectric substrate stack for maximum Raman signal.

Micro-Raman measurement of bending stresses in micromachined silicon flexures

Micron-scale characterization of mechanical stresses is essential for the successful design and operation of many micromachined devices. Here we report the use of Raman spectroscopy to measure the bending stresses in deep reactive-ion etched silicon flexures with a stress resolution of /spl sim/10 MPa and spatial resolution of /spl sim/1 /spl mu/m. The accuracy of the technique, as assessed by comparison to analytical and finite-element models of the deformation, is conservatively estimated to be 25 MPa. Implications for the use of this technique in microsystems design are discussed.

Evidence of Skyrmion excitations about nu =1 in n-modulation-doped single quantum wells by interband optical transmission.

A dramatic reduction in the spin polarization of a two-dimensional electron gas in a magnetic field is observed when the Fermi energy moves off the midpoint of the spin gap of the lowest Landau level,

Toward nanometer-scale resolution in fluorescence microscopy using spectral self-interference

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High-throughput detection and sizing of individual low-index nanoparticles and viruses for pathogen identification.

. The spin polarization is measured by magnetoabsorption spectroscopy which distinguishes the occupancy of the two electron spin states. The rapid decay of spin alignment over small changes to both higher and lower magnetic field provides experimental evidence for the presence of Skyrmion excitations where exchange energy dominates Zeeman energy in the quantum Hall regime at

Theoretical analysis of numerical aperture increasing lens microscopy

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Screening of Excitons in Single, Suspended Carbon Nanotubes

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