Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

The revolution in low-cost consumer photography and computation provides fertile opportunity for a disruptive reduction in the cost of biomedical imaging. Conventional approaches to low-cost microscopy are fundamentally restricted, however, to modest field of view (FOV) and/or resolution. We report a low-cost microscopy technique, implemented with a Raspberry Pi single-board computer and color camera combined with Fourier ptychography (FP), to computationally construct 25-megapixel images with sub-micron resolution. New image-construction techniques were developed to enable the use of the low-cost Bayer color sensor, to compensate for the highly aberrated re-used camera lens and to compensate for misalignments associated with the 3D-printed microscope structure. This high ratio of performance to cost is of particular interest to high-throughput microscopy applications, ranging from drug discovery and digital pathology to health screening in low-income countries. 3D models and assembly instructions of our microscope are made available for open source use.

Pixelation occurs in many imaging systems and limits the spatial resolution of the acquired images. This effect is notably present in quantum imaging experiments with correlated photons in which the number of pixels used to detect coincidences is often limited by the sensor technology or the acquisition speed. Here, we introduce a pixel super-resolution technique based on measuring the full spatially-resolved joint probability distribution (JPD) of spatially-entangled photons. Without shifting optical elements or using prior information, our technique increases the pixel resolution of the imaging system by a factor two and enables retrieval of spatial information lost due to undersampling. We demonstrate its use in various quantum imaging protocols using photon pairs, including quantum illumination, entanglement-enabled quantum holography, and in a full-field version of N00N-state quantum holography. The JPD pixel super-resolution technique can benefit any full-field imaging system limited by the sensor spatial resolution, including all already established and future photon-correlation-based quantum imaging schemes, bringing these techniques closer to real-world applications.

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

The magnetic properties of the neptunium monopnictides, NpN, NpP, NpAs, and NpSb, have been examined by a variety of experimental techniques. All compounds have the NaCl structure. The present paper reports the results of magnetization, Mössbauer, electrical-resistivity, neutron-diffraction, and lattice-parameter (x-ray) measurements between 1.5 and 300 °K on polycrystalline samples prepared in this laboratory. Particular emphasis is placed on both the complementary information obtained by the different techniques, and how this helps to elucidate the microscopic magnetic behavior. Neptunium nitride is ferromagnetic with $T_C=87\mathrm{}$ °K. Neptunium phosphide orders antiferromagnetically at 130 °K with an incommensurate magnetic structure. At 74 °K the magnetic structure becomes commensurate with the lattice (repeat distance 3.0 unit cells) and at lower temperatures tends to form a 3+, 3- sequence. A complete solution for the magnetic structure at low temperature is obtained by combining the neutron and Mössbauer results. Neptunium arsenide becomes antiferromagnetic at $T_N=175\mathrm{}$ °K. At ∼ 160 °K, the high-temperature 4+, 4- structure transforms to the type-I arrangement (simple +,- sequence). The crystal lattice of NpAs becomes tetragonal at $T_N$, exhibits a first-order transition to cubic symmetry at 142 °K, and remains cubic at lower temperatures. The electrical resistivity increases by an order of magnitude on cooling from 142 to 141 °K. Neptunium antimonide is a type-I antiferromagnet with $T_N=207\mathrm{}$ °K. The variation of the ordered moments ($\frac{1.4{\mu }_B}{\mathrm{Np}}$ in NpN to $\frac{2.5{\mu }_B}{\mathrm{Np}}$ in NpSb), paramagnetic effective moment ($\sim \frac{2.5{\mu }_B}{\mathrm{Np}}$), and the Mössbauer parameters (hyperfine field, quadrupole interaction, and isomer shift) all suggest a trend toward ${\mathrm{Np}}^{3+}$, $5f^4$ free-ion behavior in progressing from the nitride to the antimonide.