The external cavity tunable mid-infrared emitters based on Littrow configuration and utilizing three stages type-I quantum well cascade diode laser gain elements were designed and fabricated. The free-standing coated 7.5-μm-wide ridge waveguide lasers generated more than 30 mW of continuous wave power near 3.25 μm at 20°C when mounted epi-side-up on copper blocks. The external cavity lasers (ECLs) utilized 2-mm-long gain chips with straight ridge design and anti-/neutral-reflection coated facets. The ECLs demonstrated narrow spectrum tunable operation with several milliwatts of output power in spectral region from 3.05 to 3.25 μm corresponding to ∼25 meV of tuning range.
Artificial spin ices are often spoken of as being realisations of some of the celebrated vertex models of statistical mechanics, where the exact microstate of the system can be imaged using advanced magnetic microscopy methods. The fact that a stable image can be formed means that the system is in fact athermal and not undergoing the usual finite-temperature fluctuations of a statistical mechanical system. In this paper we report on the preparation of artificial spin ices with islands that are thermally fluctuating due to their very small size. The relaxation rate of these islands was determined using variable frequency focused magneto-optic Kerr measurements. We performed magnetic imaging of artificial spin ice under varied temperature and magnetic field using X-ray transmission microscopy which uses X-ray magnetic circular dichroism to generate magnetic contrast. We have developed an on-membrane heater in order to apply temperatures in excess of 700 K and have shown increased dynamics due to higher temperature. Due to the ‘photon-in, photon-out' method employed here, it is the first report where it is possible to image the microstates of an ASI system under the simultaneous application of temperature and magnetic field, enabling the determination of relaxation rates, coercivties, and the analysis of vertex population during reversal.
High-energy x-rays from a synchrotron source are well suited for numerous applications, such as studies of
materials structure and stress in bulk or extreme environments. Some of these methods require high spatial
resolution. Planar kinoforms are shown to focus monochromatized undulator radiation in the 50–100 keV
range down to 0.2–1.5 μm beam sizes at 0.25–2 m focal distances. These lenses were fabricated by reactive ion
etching of silicon. At such high x-ray energies, these optics can offer substantial transmission and lens aperture.
A table top nanofabrication system which combines the classic Talbot imaging effect and a compact table top soft-x ray
laser is described in this paper. Periodic nanostructures on millimeter square are fabricated using this robust, simple and
defect tolerant fabrication method. Talbot lithography allows for a complete coherent extreme ultraviolet lithography
process in a compact table top system. Double exposure allowed for the reduction of the feature sizes.
We describe a table top nanofabrication system that utilizes the coherent Talbot imaging effect and a table-top soft x ray laser to implement a defect-free compact nanolithography tool. The Talbot lithography provides a robust and simple setup capable of printing periodic structures over millimeter square areas free of defects. Test structures were fabricated into metal layers showing a complete coherent extreme ultraviolet lithographic process in a table-top system.
We have evaluated the applicability of vertically-focusing kinoform lenses for tailoring the vertical coherence
length of storage-ring undulator x-ray beams so that the entirety of the coherent flux can be used for small
angle multi-speckle x-ray photon correlation spectroscopy (XPCS) experiments. We find that the focused beam
produced by a kinoform lens preserves the coherence of the incident unfocused beam and that at an appropriate
distance downstream of the focus, the diverging beam produces speckles nearly identical to those produced by
an equivalently-sized unfocused beam. We have also investigated the effect of imperfect beamline optics on the
observed coherence properties of the beam. Via phase contrast imaging and beam-divergence measurements,
we find that a horizontally-deflecting mirror in our beamline precludes us from seeing the true radiation source
point but instead acts as an apparent source of fixed size at the center of our insertion device straight section.
Finally, we discuss how expected near-future optimization of these optics will greatly benefit XPCS measurements
performed at beamline 8-ID-I at the Advanced Photon Source.
While hard x-rays have wavelengths in the nanometer and sub-nanometer range, the ability to focus them is limited by the quality of sources and optics, and not by the wavelength. A few options, including reflective (mirrors), diffractive (zone plates) and refractive (CRL's) are available, each with their own limitations. Here we present our work with kinoform lenses which are refractive lenses with all material causing redundant 2π phase shifts removed to reduce the absorption problems inherently limiting the resolution of refractive lenses. By stacking kinoform lenses together, the effective numerical aperture, and thus the focusing resolution, can be increased. The present status of kinoform lens fabrication and testing at Brookhaven is presented as well as future plans toward achieving nanometer resolution.
This paper describes the use of a unique combination of an environmentally stable chemically amplified photoresist (UV113, Shipley) and a copolymer of methyl styrene and chloromethyl acrylate P(MS/CMA) resist (ZEP520, Zeon), without any additional intermediate layers, in the fabrication of micro- and nanochannels. The two resists used are innocuous to each other during the designed process flow, providing flexibility, high resolution, greater throughput and ease of use. We have also determined that the maximum channel length is limited by diffusion and mass transport effects, and that sub-100 nm nanochannels can be obtained with 30 micron lengths.
One application of Kinoform Fresnel Lenses is to generate small focal spots of hard X-ray photons with high gain for micro-diffraction experiments. A Kinoform lens can be obtained from a refractive lens by deleting material such that at the design photon energy, the deleted regions correspond to with modulo 2π phase-shifts in the phase front. At photon energies different from the design photon energy, the phase jumps are no longer 2π, and the diffractive properties of the kinoform become more significant. We present measurements and calculations of spot size versus photon energy.
Kinoform lenses avoid the absorption losses from a comparable refractive lens by removing all material causing redundant 2π phase shifts. Such optics allow high resolution imaging with a theoretical 94% focusing efficiency. While fabrication of kinoform lenses for two-dimensional focusing is difficult, standard lithographic processes can be utilized to fabricate optics in silicon which produce a line focus. By putting two single-dimension kinoform lenses in a crossed-pair arrangement, a two-dimensional spot is achieved. First attempts at imaging with a crossed pair of kinoform lenses are presented.
To image weakly absorbing materials (e.g. biological specimens, thin films, etc.) with hard x-ray photons, phase-contrast methods have to be applied to enhance the image contrast. Micro-fabricated Fresnel prisms in silicon have been manufactured to enable wavefront division of the incoming x-ray beam for phase-contrast applications. To maximize the efficiency and aperture of these optics, multiples of 2π phase-shifting regions in a conventional prism structure have been deleted, leading to structures that are arrays of micro-prisms. We show preliminary results of x-ray beam deflection using a variety of micro-prism arrays at the NSLS X13B undulator beamline at 11.3 keV.
Soft x-ray scanning transmission x-ray microscopy allows one to image dry and wet environmental science, biological, polymer, and geochemical specimens on a nanoscale. Recent advances in instrumentation at the X-1A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory are described. Recent results on Nomarski differential phase contrast and first results on investigations at the oxygen K edge and iron L edge of hydrous ferric oxide transformations are presented.