The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions in surface
electrode ion traps is a key component to achieving scalability for quantum information processing. Diffractive optical
elements (DOEs) present a promising approach as compared to bulk optics because of their small physical profile and
their flexibility in tailoring the optical wavefront. The precise alignment of the optics for coupling fluorescence to and
from the ions, however, poses a particular challenge. Excitation and manipulation of the ions requires a high degree of
optical access, significantly restricting the area available for mounting components. The ion traps, DOEs, and other
components are compact, constraining the manipulation of various elements. For efficient fluorescence collection from
the ions the DOE must be have a large numerical aperture (NA), which results in greater sensitivity to misalignment.
The ion traps are sensitive devices, a mechanical approach to alignment such as contacting the trap and using precision
motors to back-off a set distance not only cannot achieve the desired alignment precision, but risks damage to the ion
We have developed a non-contact precision optical alignment technique. We use line foci produced by off-axis linear
Fresnel zone plates (FZPs) projected on alignment targets etched in the top metal layer of the ion trap and demonstrate
micron-level alignment accuracy.
Designing and integrating micro-optical components into atom and ion traps are enabling steps toward miniaturizing
trap dimensions in quantum computation applications. The micro-optic must have a high numerical aperture for precise
illumination of the ion and should not introduce scatter. Due to the extreme optical efficiency requirements in trapped
ion and atom-based quantum information processing, even slight losses from integrated micro-optics are detrimental.
We have designed and fabricated aspheric micro-lenses through grayscale transfer into a fused silica in an effort to
realize increased transmissive efficiency and decreased scatter compared to an equivalent diffractive optical element.
The fabricated grayscale lens profile matched the desired lens profile well, and the measured and predicted optical
performances were in good agreement. The pattern was transferred via coupled plasma reactive-ion etching smoothly
into the fused silica with a RMS roughness ~ 35 nm. The micro-lens had a diameter of 88 um and 14.2 um sag, with an
as-designed focal length of 149 um and spot diameter of 2.6 um. The maximum measured efficiency was ~80% (86% of
theoretical, possibly due to rms roughness). This realized efficiency is superior to the equivalent diffractive lens
efficiency, designed to the same use parameters. The grayscale approach demonstrated an increase in collection
efficiency, at the desired optical focal length, providing the potential for further refinement.
For practical quantum computing, it will be necessary to detect the fluorescence from trapped ions using microscale ion
trap chips. We describe the first design, fabrication and assembly of a set of diffractive optics for intimate integration
into the trap chip and for coupling this fluorescence into multimode fibers. The design is complicated by the constraints
of the ion trap environment. In addition, the choice of available materials is restricted to those compatible with ultrahigh
vacuum. The completed optics-ion trap assembly has successfully demonstrated ion trapping, as well as ion shuttling,
with no necessary modifications to the trapping and shuttling voltage levels.
We demonstrate a large area production of 3-D woodpile metallic photonic crystals using deep x-ray lithography and subsequent electroforming. These structures represent the 110 orientation of the 001 woodpile structures most commonly presented in the literature. This approach requires no alignment and is capable of generating a 3 unit cell thick photonic crystal in a simple three step process flow. Tilted woodpiles demonstrate band characteristics very similar to those observed from  woodpiles. Reflectivity tests show a band edge around 4 µm and good comparison well with numerical simulations.
In this paper, we describe our efforts to control the thermal emission from a surface utilizing structured surfaces with
metal/dielectric interfaces. The goal was not to eliminate the emission, but to control the output direction and spectrum.
We focus on methods that lead to high emissivity at grazing angles, with low emission near normal. We describe the
fabrication and measurement of large passive devices (15×15 mm) and arrays of smaller chips for thermal emission
control in the longwave infrared (8 to 12 micron) spectral region. All the devices consist of a metal base layer covered
with dielectric/metal posts or lines, 0.5 microns tall. The posts (0.9×0.9 micron) and lines (0.3 micron wide) are subwavelength.
One-dimensional and two-dimensional devices with a 3 micron pitch will be shown. The devices are
measured with both a hemispherical directional reflectometer and a variable angle directional emissometer. Both
simulated and experimental results show the thermal emission effectively limited to a small spectral region and grazing
angles from the surface (≥ 80°) in stark contrast to the typical Lambertian radiation seen from unstructured material.
Finally, the effect of this thermal emission control is illustrated using an infrared camera.
In this work, we describe the most recent progress towards the device modeling, fabrication, testing and system
integration of active resonant subwavelength grating (RSG) devices. Passive RSG devices have been a subject of
interest in subwavelength-structured surfaces (SWS) in recent years due to their narrow spectral response and high
quality filtering performance. Modulating the bias voltage of interdigitated metal electrodes over an electrooptic thin
film material enables the RSG components to act as actively tunable high-speed optical filters. The filter characteristics
of the device can be engineered using the geometry of the device grating and underlying materials.
Using electron beam lithography and specialized etch techniques, we have fabricated interdigitated metal electrodes on
an insulating layer and BaTiO3 thin film on sapphire substrate. With bias voltages of up to 100V, spectral red shifts of
several nanometers are measured, as well as significant changes in the reflected and transmitted signal intensities around
the 1.55um wavelength.
Due to their small size and lack of moving parts, these devices are attractive for high speed spectral sensing applications.
We will discuss the most recent device testing results as well as comment on the system integration aspects of this
Straightforward extension of canonical microwave metamaterial structures to optical and IR frequency dimensions is
complicated by both the size scale of the resulting structures, requiring cutting edge lithography to achieve the requisite
line-widths, as well as limitations on assembly/construction into final geometry. We present a scalable fabrication
approach capable of generating metamaterial structures such as split ring resonators and split wire pairs on a micron/sub-micron
size scale on concave surfaces with a radius of curvature ~ SRR diameter. This talk outlines the fabrication
method and modeling/theory based interpretation of the implications of curved metamaterial resonators.
We have developed a system to measure the directional thermal emission from a surface, and in turn, calculate its
emissivity. This approach avoids inaccuracies sometimes encountered with the traditional method for calculating
emissivity, which relies upon subtracting the measured total reflectivity and total transmissivity from unity. Typical total
reflectivity measurements suffer from an inability to detect backscattered light, and may not be accurate for high angles
Our design allows us to vary the measurement angle (θ) from near-normal to ~80°, and can accommodate samples as
small as 7 mm on a side by controlling the sample interrogation area. The sample mount is open-backed to eliminate
shine-through, can be heated up to 200 °C, and is kept under vacuum to avoid oxidizing the sample. A cold shield
reduces the background noise and stray signals reflected off the sample. We describe the strengths, weaknesses, trade-offs,
and limitations of our system design, data analysis methods, the measurement process, and present the results of our
validation of this Variable-Angle Directional Emissometer.
We will discuss a passive thermal emission management surface that can manipulate the direction and
wavelength bands of emission. We are designing and fabricating diffractive optics in materials that support
surface-polariton plasmons. We use a grating in this material to couple the thermally-generated plasmons to
photons. Grating parameters, such as grating depth and duty cycle, are varied to optimize the plasmon/photon
coupling efficiency. The grating configuration ensures a phased, radiative response if the plasmon decay length
along the surface traverses many grating periods. All of these parameters, material indices and dimensions,
determine the specular and angular "shape" of emission.
We present simulations and measurements of a technology that can manipulate thermal angular and wavelength
emission. This work is representative of Sandia National Laboratories' efforts to investigate advanced
technologies that are not currently accessible for reasons such as risk, cost, or limited availability. The goal of
this project is to demonstrate a passive thermal emission management surface that can tailor the direction of
emission as well as the wavelength bands of emission.
This new proposed technology enables thermal emission pattern management by structuring the surface. This
structuring may be in either the lateral or depth dimension. A lateral structuring consists of a shallow grating on
a metal surface. This air/metal interface allows photon/plasmon coupling, which has been shown to coherently
and preferentially emit at certain wavelengths.
The LIGA microfabrication technique offers a unique method for fabricating 3-dimensional photonic lattices based on the Iowa State "logpile" structure. These structures represent the  orientation of the  logpile structures previously demonstrated by Sandia National Laboratories. The novelty to this approach is the single step process that does not require any alignment. The mask and substrate are fixed to one another and exposed twice from different angles using a synchrotron light source. The first exposure patterns the resist at an angle of 45 degrees normal to the substrate with a rotation of 8 degrees. The second exposure requires a 180 degree rotation about the normal of the mask and substrate. The resulting pattern is a vertically oriented logpile pattern that is rotated slightly off axis. The exposed PMMA is developed in a single step to produce an inverse lattice structure. This mold is filled with electroplated gold and stripped away to create a usable gold photonic crystal. Tilted logpiles demonstrate band characteristics very similar to those observed from  logpiles. Reflectivity tests show a band edge around 5 μm and compare well with numerical simulations.