Temperature measurement in plasmonic traps is important because biological molecules and quantum emitters are sensitive to temperature. While other works have used ion pore currents, fluorescence emission variation, and fluorescent diffusion tracking to measure the temperature dependence of shaped nanoapertures in metal films, here we make use of a stable erbium (Er) containing NaYF4 nanocrystals that gives local temperature dependence. The local temperature variation is determined by a ratiometric analysis of the emission at different wavelengths.
Here we use optical trapping to isolate single Yb/Er-doped upconversion nanocrystals in plasmonic double nanohole apertures and show that the geometry of the aperture can be tuned to give high emission rate en- hancement. The double nanohole apertures show additional enhancement over the rectangular apertures that were previously demonstrated by our group, producing enough enhancement to observe emission at 400 nm and 1550 nm with 980 nm excitation—not seen in our group’s previous work with rectangular apertures. A facile method for tuning the geometry of double nanohole apertures by adjusting the plasma etching time in the colloidal lithography fabrication process is discussed. We find that a double nanohole with a cusp separation of 32 nm yields the greatest emission enhancement with multiple plasmonic resonances which enhance both the excitation and emission wavelengths. The emission enhancement for the DNH with 32 nm cusp separation was found to be a factor of 54, 44, and 31 greater than the rectangular apertures used in our group’s previous work, for wavelengths of 650 nm, 550 nm, and 400 nm. This result shows that double nanohole apertures can be tuned for emission enhancement as required by specific applications.
Single photon sources are desired for quantum computing and communication applications. Ideally, these sources would provide single photons on demand at the low-loss fiber optical communication wavelength of 1550 nm. Single Erbium ions provide a good candidate for such sources because they emit at the right wavelength and they are very stable, however, the challenges remain of isolating a single emitter, coupling its emission to optical fiber and enhancing its emission rate. Nanoaperture optical tweezers provide a pathway to solving these issues by trapping and identifying single emitters, enhancing their emission rate and providing efficient coupling to an optical fiber. Recently, we have made progress in each of these areas (trapping, enhancing and coupling), which will be reviewed in this talk.
Purpose: We present photon-counting computed tomography (PCCT) imaging of contrast agent triplets similar in atomic number (Z) achieved with a high-flux cadmium zinc telluride (CZT) detector.
Approach: The table-top PCCT imaging system included a 330-μm-pitch CZT detector of size 8 mm × 24 mm2 capable of using six energy bins. Four 3D-printed 3-cm-diameter phantoms each contained seven 6-mm-diameter vials with water and low and high concentration solutions of various contrast agents. Lanthanum (Z = 57), gadolinium (Gd) (Z = 64), and lutetium (Z = 71) were imaged together and so were iodine (Z = 53), Gd, and holmium (Z = 67). Each phantom was imaged with 1-mm aluminum-filtered 120-kVp cone beam x rays to produce six energy-binned computed tomography (CT) images.
Results:K-edge images were reconstructed using a weighted sum of six CT images, which distinguished each contrast agent with a root-mean-square error (RMSE) of <0.29 % and 0.51% for the 0.5% and 5% concentrations, respectively. Minimal cross-contamination in each K-edge image was seen, with RMSE values <0.27 % in vials with no contrast.
Conclusion: This is the first preliminary demonstration of simultaneously imaging three similar Z contrast agents with a difference in Z as low as 3.
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