The non-deterministic nature of photon sources is a key limitation for single-photon quantum processors. Spatial multiplexing overcomes this by enhancing the heralded single-photon yield without enhancing the output noise. Here the intrinsic statistical limit of an individual source is surpassed by spatially multiplexing two monolithic silicon-based correlated photon pair sources in the telecommunications band, demonstrating a 62.4% increase in the heralded single-photon output without an increase in unwanted multipair generation. We further demonstrate the scalability of this scheme by multiplexing photons generated in two waveguides pumped via an integrated coupler with a 63.1% increase in the heralded photon rate. This demonstration paves the way for a scalable architecture for multiplexing many photon sources in a compact integrated platform and achieving efficient two-photon interference, required at the core of optical quantum computing and quantum communication protocols.

Dielectric metasurfaces require high refractive index contrast materials for optimum performance. This requirement imposes a severe restraint; devices have either been demonstrated at wavelengths of 700nm and above using high-index semiconductors such as silicon, or they use lower index dielectric materials such as TiO2 or Si3N4 and operate in the visible wavelength regime.Here, we show that the high refractive index of silicon can be exploited at wavelengths as short as 532 nm by demonstrating a silicon metasurface with a transmission efficiency of 47% at this wavelength. The metasurface consists of a graded array of silicon posts arranged in a square lattice on a quartz substrate. We show full 2π phase control and we experimentally demonstrate

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Extensive diversity is evident in both the y and 8 chain junctional amino acids of the receptors of these cells, indicating that they may largely develop in the thymus of older animals or undergo peripheral expansion. Finally, we found that all such cells responding to both a putative self-antigen and to mycobacterial Hsp6O respond to a 17-amino acid synthetic peptide representing amino acids 180-196 of the Mycobacterium klprae Hsp6O sequence. This report demonstrates that a large subset of Hsp60-reactive peripheral lymphoid y8 T cells preexists in normal adult mice, all members of which respond to a single segment of this common heat shock protein.T cells bearing the y8T-cell antigen receptor (TCR) have been detected as a distinct lymphocyte subset in many mammalian species and in birds (1-6), suggesting that 'y8 T cells play a functional role worthy of evolutionary conservation. We have previously reported on a subset of y8T cells present in the newborn mouse thymus that responds to a mycobacterial heat shock protein (Hsp) Hsp6O (7) (9). These cells, when immortalized as hybridomas, produce interleukin 2 (IL-2) in the absence of any deliberate stimulation. This "spontaneous" IL-2 production may arise from stimulation of the cells by their own endogenous Hsp6O or a related protein because some of the cells also recognize a synthetic peptide representing the same region of mouse Hsp6O, as well as this region of Hsp6O from other disparate species (8). The subset thus shows a propensity to recognize a certain protein and always the same segment of that protein, despite some degree of junctional variation in both the 'yand 8 chains of the TCR and even occasional use of a different 8 chain. We considered whether such potentially autoreactive yS T cells are normally eliminated during thymic differentiation. However, in the study reported here, we have characterized similar cells that appear to exist as a large circulating subset in the adult mouse. These cells, showing the same pattern of Hsp6O reactivity, express a Vyl chain, and many express a V86 chain, as was seen in the newborn thymus y8 cells; moreover, extensive junctional diversity is evident. Unless these cells normally exist in an inactive state, a possibility that cannot be ruled out in an experiment involving hybridomas, our data suggest a functional role for Hsp60-reactive 'y3 T cells in the periphery.MATERIALS AND METHODS Hybridoma Generation. For each fusion experiment, adult spleen cells from =.10 C57BL/10 mice were enriched for y8 T cells by using a "panning" technique, as described (10), to remove B cells and a,8 T cells. For anti-af3 TCR panning, B cells were first removed on goat anti-mouse immunoglobulincoated dishes or with nylon wool. Monoclonal antibody (mAb) H57-597 (11) was applied at 4100 pg/ml in balanced salts solution, the blocking step was allowed to proceed for not more than 30 min at 370C, and the cells were allowed to bind during an incubation at 370C. These cell preparations were 20-to 60-fold enriched for y8 T cells and were thus s...

Different types of planar photonic crystal cavities aimed at optimizing the far-field emission pattern are designed and experimentally assessed by resonant scattering measurements. We systematically investigate the interplay between achieving the highest possible quality (Q) factor and maximizing the in- and out-coupling efficiency into a narrow emission cone. Cavities operate at telecommunications wavelengths, i.e. around approximately 1.55 microm, and are realized in silicon membranes. A strong modification of the far-field emission pattern, and therefore a substantial increase of the coupling efficiency in the vertical direction, is obtained by properly modifying the holes around L3, L5 and L7 type PhC cavities, as we predict theoretically and show experimentally. An optimal compromise yielding simultaneously a high Q-factor and a large coupling to the fundamental cavity mode is found for a L7-type cavity with a measured Q congruent with 62000, whose resonant scattering efficiency is improved by about two orders of magnitude with respect to the unmodified structure. These results are especially useful for prospective applications in light emitting devices, such as nano-lasers or single-photon sources, in which vertical in- and out-coupling of the electromagnetic field is necessarily required.

Dielectric metasurfaces support resonances that are widely explored both for far-field wavefront shaping and for near-field sensing and imaging. Their design explores the interplay between localised and extended resonances, with a typical trade-off between Q-factor and light localisation; high Q-factors are desirable for refractive index sensing while localisation is desirable for imaging resolution. Here, we show that a dielectric metasurface consisting of a nanohole array in amorphous silicon provides a favourable trade-off between these requirements. We have designed and realised the metasurface to support two optical modes both with sharp Fano resonances that exhibit relatively high Q-factors and strong spatial confinement, thereby concurrently optimizing the device for both imaging and biochemical sensing. For the sensing application, we demonstrate a limit of detection (LOD) as low as 1 pg/ml for Immunoglobulin G (IgG); for resonant imaging, we demonstrate a spatial resolution below 1 µm and clearly resolve individual E. coli bacteria. The combined low LOD and high spatial resolution opens new opportunities for extending cellular studies into the realm of microbiology, e.g. for studying antimicrobial susceptibility.

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Advanced biomedical diagnostic technologies fulfill an important role in improving health and well-being in society. A large number of excellent technologies have already been introduced and have given rise to the “lab-on-a-chip” paradigm. Most of these technologies, however, require additional instrumentation for interfacing and readout, so they are often confined to the laboratory and are not suitable for use in the field or in wider clinical practice. Other technologies require a light coupling element, such as a grating coupler or a fiber coupler, which complicates packaging. Here, we introduce a novel biosensor based on a chirped guided-mode resonant grating. The chirped grating combines the sensing function with the readout function by translating spectral information into spatial information that is easily read out with a simple CMOS camera. We demonstrate a refractive index sensitivity of 137 nm/RIU and an extrapolated limit of detection of 267 pM for the specific binding of an immunoglobulin G antibody. The chirped guided-mode resonance approach introduces a new degree of freedom for sensing biomedical information that combines high sensitivity with autonomous operation. We estimate that the cost of components is U.S. $10 or less when mass manufactured, so the technology has the potential to truly transform point-of-care applications.