We report a strain sensing approach that utilizes wrinkled patterns on poly (dimethylsiloxane) (PDMS) as an optical grating to measure thermally-induced strain of different materials. The mechanism for the strain sensing and the effect of PDMS grating on strain sensing are discussed. By bonding the PDMS grating onto a copper or silicon substrate, the coefficient of thermal expansion (CTE) of th...

We have developed a mask pattern transferred transient grating (MPT-TG) technique by using metal grating films. Transient thermal grating is generated by an ultraviolet light pattern transfer to nitrobenzene in 2-propanol solution, and the subsequent effect is detected through its diffraction to a probe beam. The thermal diffusion coefficient is obtained by the relationship between the grating ...

Based on the total internal reflection (TIR) under second Bragg incidence angle, polarization-independent two-port beam splitter grating etched in fused silica is described for the usual duty cycle of 0.5. There are three diffraction orders in the reflection: –2nd order, –1st order, and 0th order. The grating depth and period are optimized using the rigorous coupled-wave analysis (RCWA) in orde...

This paper introduces a novel approach to surface bioaffinity sensing based on the adsorption of nanoparticles onto a gold diffraction grating that supports the excitation of planar surface plasmons. A surface enzymatic amplification reaction is also incorporated into the detection scheme to enhance the sensitivity and utility of the nanoparticle-enhanced diffraction grating (NEDG) sensors. As ...

The formation of high-order Bessel beams by a passive acoustic device consisting of an Archimedes' spiral diffraction grating is theoretically, numerically, and experimentally reported in this paper. These beams are propagation-invariant solutions of the Helmholtz equation and are characterized by an azimuthal variation of the phase along its annular spectrum producing an acoustic vortex in the...

The need to improve sensing technology for widespread application in everyday life is fueling the development of diffraction-based sensing, an optical sensing technique. Selectivity and sensitivity issues must first be resolved. Both selectivity and sensitivity can be increased by using resonance conditions — that is, using a probe wavelength where the system absorbs. The resonance effects are ...

Large area, high resolving power spectroscopy in the soft x-ray band can only be achieved with a state-of-the-art diffraction grating spectrometer, comprised of large collecting-area focusing optics with a narrow point spread function, large-area high-resolving power diffraction gratings, and small pixel, order sorting x-ray detectors. Recently developed critical-angle transmission (CAT) gratin...

The research described in this thesis is a portion of a larger project within the Photonic Systems Group at MIT to design Compact Optoelectronic Integrated Neural (COIN) coprocessors [13]. The choice of photopolymers is critical in determining the performance of COIN processors as we look at ways to increase the diffraction efficiency. The focus of this research was to optically characterize Po...

A transmission-type surface plasmon resonance configuration with dielectric gratings regularly patterned on a silver film was investigated with the aim of enhancing the diffraction efficiency of radiative surface plasmons. The theoretical work was conducted using rigorous coupled-wave analysis in terms of first order diffraction efficiency and conversion efficiency (CE). The results show that p...

The use of double grating diffraction shearing for measurement of MTF is demonstrated. By superimposing two gratings optically we avoid the problem of grating contact and subsequent degradation. This simple and economical method is especially advantageous for optical systems with large pupil for which a rotating plate interferometer becomes prohibitively expensive.