Schematic of the tuneable IR source built for the imaging system. A laser, based on the transition, is configured to produce 100 ps pulses. After amplification these are intense enough to generate usefully intense “optical parametric generation” pulses after a double pass through a nonlinear crystal. The wavelengths of the OPG output pulses are determined by momentum-matching constraints inside the nonlinear crystal, so they can be selected at will by choosing its angle under computer control.
Upper plot: Pulse energy histogram of the laser set to a mean output of . Lower plot: Histogram of OPG idler pulse energies at a wavelength of and a nominal pulse energy of .
Schematic of the optical setup.
Plot of the variation in OPG linewidth as it is tuned through the mid-IR.
(a) The standard USAF 1915 resolution test sample used to calibrate the IR imager. (b) Transmission mode images of the chart recorded with the JASCO-IRT 30 microscope and the CEDIP FPA camera using illumination from the OPG laser source. (i) Picture is of line pairs in group 4 on the chart where elements 4, 5, and 6 (G4-E4,E5, and E6) are resolved by visual inspection. (ii) Picture is of line pairs in group 5 in the chart where elements 4, 5, and 6 (G5-E4,E5, and E6) are resolved by visual inspection. (iii) Picture is of line pairs in group 6 on the chart where elements 1 and 2 (G6-E1,E2) are resolved by visual inspection.
(a) Reflection mode image of a copper electron microscopy grid taken with a single 100 ps pulse from the OPG. (b) Intensity scan across the line in the image, evidencing an unsmoothed SNR of and diffraction-limited spatial resolution.
(a) Visible image of the test sample for chemical mapping tests. It consists of a variety of PMMA shapes deposited on a silicon substrate by photolithography which we were able to map in a single 100 ps shot of OPG light, in the specular reflectance mode (b). The line scan (c) reveals the degree to which the grid structure (with a pitch) in the upper left of the image has been spatially resolved.
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