An engineered plasmonic gold surface, specifically designed to couple with 980 nm radiation, is shown to enhance near-infrared-to-visible upconversion luminescence from a monolayer of β-NaYF4: 17%Yb, 3%Er nanocrystals in poly(methyl methacrylate) on that gold surface. Confocal imaging of upconversion luminescence from the surface is used to characterize the nature of the enhancement. It is shown that the luminescence data were acquired below the so-called “high power limit” for excitation, but some saturation was evident, as the observed power dependence was less than quadratic. Over the range of excitation power densities used, the intrinsic enhancement factor for upconversion from the patterned surface was greater than a factor of 3 but decreased slowly with increasing excitation power. The red and green upconversion were enhanced by similar factors, which would support the intensification of the excitation field by the plasmonic surface as being the mechanism of enhancement. In the absence of other enhancement or quenching mechanisms, the data imply an approximate 2-fold magnification of the excitation field intensity relative to smooth gold.

We report on the development and utilization of a double split-ring microwave resonator for uniform and efficient coupling of microwave magnetic field into nitrogen-vacancy (NV) centers in a diamond over a mm(2) area. Uniformity and magnitude of delivered microwave field were measured using the Rabi nutation experiment on arrays of diamond nanowires with ensemble NV centers. An average Rabi nutation frequency of 15.65 MHz was measured over an area of 0.95 × 1.2 mm, for an input microwave power of 0.5 W. By mapping the Rabi nutation frequency to the magnetic field, the average value of the magnetic field over the aforementioned area and input microwave power was 5.59 G with a standard division of 0.24 G.

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Spectroscopic imaging and time-resolved spectroscopy are used to study the surface plasmon polariton (SPP) enhanced infrared to visible upconversion luminescence from NaYF 4 :Tm:Yb nanoparticles embedded in polymethyl methylacrylate (PMMA) supported on Au nanopillar arrays. The arrays have a lattice resonance associated with the SPP near 980 nm, near-resonant with the peak absorption of the Yb 3+ ion, while a local surface plasmon resonance (LSPR) associated with the individual pillars is seen to enhance the near-infrared emission of Tm 3+ ions near 780 nm. The two combined channels of enhancement result in a significantly higher enhancement of the near-infrared emission when compared to the visible upconversion lines of the Tm 3+ ion, consistent with the interpretation of sequential surface plasmon assisted absorption and emission at two separate and disparate energies. The presence of SPP and LSPR was confirmed by spectrally resolved reflectivity, and the mechanisms for luminescence enhancement were further confirmed by time-resolved measurements of the upconversion luminescence.

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