14 research outputs found
Polarization effects in the nonlinear interference of down-converted photons
We study polarization effects in the nonlinear interference of photons
generated via frequency non-degenerate spontaneous parametric down conversion.
Signal and idler photons generated in the visible and infrared (IR) range, are
split in different arms of a nonlinear Michelson interferometer. The
interference pattern for signal photons is detected, and it is shown to be
dependent on the polarization rotation of idler photons, introduced by a
birefringent sample. Based on this concept, we realize two new methods for
measurement of sample retardation in the IR range by using well-developed and
inexpensive components for visible light. The accuracy of the methods meets
current industry standards. The developed IR polarimetry technique is relevant
to material research, optical inspection, and quality control.Comment: Submitted for publicatio
Measurement of infrared optical constants with visible photons
We demonstrate a new scheme of infrared spectroscopy with visible light
sources and detectors. The technique relies on the nonlinear interference of
correlated photons, produced via spontaneous parametric down conversion in a
nonlinear crystal. Visible and infrared photons are split into two paths and
the infrared photons interact with the sample under study. The photons are
reflected back to the crystal, resembling a conventional Michelson
interferometer. Interference of the visible photons is observed and it is
dependent on the phases of all three interacting photons: pump, visible and
infrared. The transmission coefficient and the refractive index of the sample
in the infrared range can be inferred from the interference pattern of visible
photons. The method does not require the use of potentially expensive and
inefficient infrared detectors and sources, it can be applied to a broad
variety of samples, and it does not require a priori knowledge of sample
properties in the visible range
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
Effect of Laser Heating Duration on Lubricant Depletion in Heat Assisted Magnetic Recording
Method for Measurement of Switching-Field Distribution of Heat-Assisted Magnetic Recording Media
Identifying key mononuclear Fe species for low-temperature methane oxidation
10.1039/d0sc06067dChemical Science1293152-316