<p> Conversion of plane waves to surface waves prior to detection allows key advantages in changes to the architecture of the detector pixels in a focal plane array. We have integrated subwavelength patterned metal nanoantennas with various detector materials to incorporate these advantages: midwave infrared indium gallium arsenide antimonide detectors and longwave infrared graphene detectors. </p> <p> Nanoantennas offer a means to make infrared detectors much thinner by converting incoming plane waves to more tightly bound and concentrated surface waves. Thinner architectures reduce both dark current and crosstalk for improved performance. For graphene detectors, which are only one or two atomic layers thick, such field concentration is a necessity for usable device performance, as single pass plane wave absorption is insufficient. Using III-V detector material, we reduced thickness by over an order of magnitude compared to traditional devices. </p> <p> We will discuss Sandia’s motivation for these devices, which go beyond simple improvement in traditional performance metrics. The simulation methodology and design rules will be discussed in detail. We will also offer an overview of the fabrication processes required to make these subwavelength structures on at times complex underlying devices based on III-V detector material or graphene on silicon or silicon carbide. Finally, we will present our latest infrared detector characterization results for both III-V and graphene structures. </p>
Nanoantennas are an enabling technology for visible to terahertz components and may be used with a variety of detector materials. We have integrated subwavelength patterned metal nanoantennas with various detector materials for infrared detection: midwave infrared indium gallium arsenide antimonide detectors, longwave infrared graphene detectors, and shortwave infrared germanium detectors. Nanoantennas offer a means to make infrared detectors much thinner, thus lowering the dark current and improving performance. The nanoantenna converts incoming plane waves to more tightly bound and concentrated surface waves. The active material only needs to extend as far as these bound fields. In the case of graphene detectors, which are only one or two atomic layers thick, such field concentration is a necessity for usable device performance, as single pass absorption is insufficient. The nanoantenna is thus the enabling component of these thin devices. However nanoantenna integration and fabrication vary considerably across these platforms as do the considerations taken into account during design. Here we discuss the motivation for these devices and show examples for the three material systems. Characterization results are included for the midwave infrared detector.
Current infrared imaging systems monitor emission from a given scene over a broad spectral range, which results with "black and white" images. As a result, there is ever increasing emphasis on the development of new, on the pixel level, infrared imaging technology that can provide spectral information. Attempts at creating a robust imaging system with spectral information have been made through a network of external optics, which results with a high cost and large system package. Here, we propose a metamaterial design that resonantly couples to an infrared photodetector for enhanced performance.
We show simulation results of the integration of a nanoantenna in close proximity to the active material of a photodetector. The nanoantenna allows a much thinner active layer to be used for the same amount of incident light absorption. This is accomplished through the nanoantenna coupling incoming radiation to surface plasmon modes bound to the metal surface. These modes are tightly bound and only require a thin layer of active material to allow complete absorption. Moreover, the nanoantenna impedance matches the incoming radiation to the surface waves without the need for an antireflection coating. While the nanoantenna concept may be applied to any active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The addition of the nanoantenna to the photodiode requires changes to the geometry of the stack beyond the simple addition of the nanoantenna and thinning the active layer. We will show simulations of the electric fields in the nanoantenna and the active region and optimized designs to maximize absorption in the active layer as opposed to absorption in the metal of the nanoantenna. We will review the fabrication processes.
The angular sensitivity of guided mode resonant filters (GMRF) is well known. While at times useful for angle tuning of
the response, this sensitivity can also be a major detriment as angular changes of tenths of a degree can shift the
wavelength response in a narrow bandwidth device by an amount greater than the width of the resonance peak. We
identify geometries where the resonance is more angularly stable, demonstrating high reflectivity at the design
wavelength for several degrees in both azimuth and inclination angular directions with virtually no change in lineshape of the response. The investigation of GMRFs in both classical and conical mounts through simulation using rigorous coupled wave analysis reveals that there are preferred mounts for greater angular tolerance. We simulate a grating at telecom wavelengths using a design that we have previously fabricated. The identical grating placed in different mounts can exhibit angular tolerances that differ by well over an order of magnitude (60x). The most commonly used classical mount has a much more sensitive angular tolerance than does the conical mount. The lineshape of the resonant response shows only negligible changes across the angular band. The angular band for the sample grating is simulated to be several degrees in the conical mount as opposed to a tenth of a degree in the classical mount. We could thus expand the application space for narrow-band GMRFs into areas where angular tolerance cannot be controlled to the degree that we have believed required in the past.
We demonstrate the effects of integrating a nanoantenna to a midwave infrared (MWIR) focal plane array (FPA). We
model an antenna-coupled photodetector with a nanoantenna fabricated in close proximity to the active material of a
photodetector. This proximity allows us to take advantage of the concentrated plasmonic fields of the nanoantenna. The
role of the nanoantenna is to convert free-space plane waves into surface plasmons bound to a patterned metal surface.
These plasmonic fields are concentrated in a small volume near the metal surface. Field concentration allows for a
thinner layer of absorbing material to be used in the photodetector design and promises improvements in cutoff
wavelength and dark current (higher operating temperature). While the nanoantenna concept may be applied to any
active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The geometry of the
nanoantenna-coupled detector is optimized to give maximal carrier generation in the active region of the photodiode, and
fabrication processes must be altered to accommodate the nanoantenna structure. The intensity profiles and the carrier
generation rates in the photodetector active layers are determined by finite element method simulations, and iteration
between optical nanoantenna simulation and detector modeling is used to optimize the device structure.
We present a broadband, all-dielectric, diffractive optical element (DOE) for spectral beam combining with
optimized efficiency. We achieve maximal efficiency and polarization insensitivity for the sum of incident
wavelengths by varying grating etch depth and duty cycle of a rectangular profile grating realized with the precision
of ebeam mask definition. Design and fabrication considerations that maximize efficiency are quantified, including
material options, e-beam defined lithographic parameters such as grating periods and aspect ratios, tailored
wavelength dispersion, and polarization independence. These results are compared to published efficiency values of
>95% diffraction efficiency for a single polarization and single wavelength and polarization-independent efficiency
values of >98% also for a single wavelength.
We design and fabricate arrays of diffractive optical elements (DOEs) to realize neutral atom micro-traps for
quantum computing. We initialize a single atom at each site of an array of optical tweezer traps for a customized
spatial configuration. Each optical trapping volume is tailored to ensure only one or zero trapped atoms.
Specifically designed DOEs can define an arbitrary optical trap array for initialization and improve collection
efficiency in readout by introducing high-numerical aperture, low-profile optical elements into the vacuum
We will discuss design and fabrication details of ultra-fast collection DOEs integrated monolithically and coaxially
with tailored DOEs that establish an optical array of micro-traps through far-field propagation. DOEs, as mode
converters, modify the lateral field at the front focal plane of an optical assembly and transform it to the desired field
pattern at the back focal plane of the optical assembly. We manipulate the light employing coherent or incoherent
addition with judicious placement of phase and amplitude at the lens plane. This is realized through a series of
patterning, etching, and depositing material on the lens substrate. The trap diameter, when this far-field propagation
approach is employed, goes as 2.44λF/#, where the F/# is the focal length divided by the diameter of the lens
aperture. The 8-level collection lens elements in this presentation are, to our knowledge, the fastest diffractive
elements realized; ranging from F/1 down to F/0.025.
Resonant subwavelength gratings have been designed and fabricated as wavelength-specific reflectors for application as
a rotary position encoder utilizing ebeam based photolithography. The first grating design used a two-dimensional
layout to provide polarization insensitivity with separate layers for the grating and waveguide. The resulting devices had
excellent pattern fidelity and the resonance peaks and widths closely matched the expected results. Unfortunately, the
gratings were particularly angle sensitive and etch depth errors led to shifts in the center wavelength of the resonances.
A second design iteration resulted in a double grating period to reduce the angle sensitivity as well as different materials
and geometry; the grating and waveguide being the same layer. The inclusion of etch stop layers provided more accurate
etch depths; however, the tolerance to changes in the grating duty cycle was much tighter. Results from these devices
show the effects of small errors in the pattern fidelity. The fabrication process flows for both iterations of devices will be
reviewed as well as the performance of the fabricated devices. A discussion of the relative merits of the various design
choices provides insight into the importance of fabrication considerations during the design stage.
We describe the design of pixelated filter arrays for hyperspectral monitoring of CO<sub>2</sub> and H<sub>2</sub>O absorption in the
midwave infrared (centered at 4.25μm and 5.15μm, respectively) using resonant subwavelength gratings (RSGs), also
called guided-mode resonant filters (GMRFs). For each gas, a hyperspectral filter array of very narrowband filters is
designed that spans the absorption band on a single substrate. A pixelated geometry allows for direct registration of
filter pixels to focal plane array (FPA) sensor pixels and for non-scanning data collection. The design process for
narrowband, low-sideband reflective and transmissive filters within fabrication limitations will be discussed.
We present design, fabrication, and characterization results of a highly absorptive surface in the thermal
infrared that draws on concepts from the frequency selective surface and metamaterials communities. At
normal incidence this optically thin surface has an absorption of over 99%. Furthermore, it has a broad
angular range (over 90% absorption at 60 degrees from normal). The simple structure is composed of a
reflective metal layer, a roughly quarter-wave layer of lossy dielectric, and a top metal layer that is patterned
with an array of subwavelength apertures. The design of the aperture allows spectral and angular control of
the absorption/emission band. We will present simulation and measured results. Change in waveband and
polarization could easily be changed from pixel to pixel in a focal plane array.
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.
Resonant subwavelength gratings have proven to be excellent devices for producing narrow resonances useful for
filtering applications. In this paper we discuss the use of RSGs in a rotary position encoder intended for use in harsh
environments. To avoid problems with routing electrical signals to the encoder, a single fiber optic connection is used to
address the device with multiplexed wavelengths corresponding to position bits. Each wavelength has a corresponding
RSG that is patterned in the appropriate position locations. A demonstration device utilizing RSGs with TiO<sub>2</sub> and SiO<sub>2</sub>
films on a silicon substrate will be presented. The design and modeling effort provided several RSGs with resonances
addressable by a single tunable laser source. Since multimode fiber is used to route the optical signals, the gratings were
designed to be polarization insensitive. Additionally, the individual RSGs accommodate significant wavelength shifts to
simplify the integration of the encoder system. The fabrication of the devices was based on electron beam lithography
and details of this work will be presented. Measurements of the individual RSGs as well as a demonstration of the
determination of rotary position using these gratings will be shown.
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 BaTiO<sub>3</sub> 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
We show design, modeling, fabrication, and characterization results for high-transmission broad-angle frequency
selective surfaces (FSSs) in the mid-infrared. The single metal layer of a FSS allows its incorporation directly into focal
plane array (FPA) designs, thus allowing direct integration of the filtering and polarizing properties of the FSS into
sensors from single photodetectors to FPAs. In thin film filter designs the number of layers and film thicknesses may
vary pixel-to-pixel, making fabrication difficult. In contrast, changes in spectral passband or polarization state are easily
accomplished with changes to the FSS pattern.
We have designed, fabricated, and tested FSSs of patterned gold on a GaAs substrate. Designs include single metal
layers and a metal plus a dielectric layer. Design and modeling were performed using rigorous coupled wave analysis
(RCWA). Further simulations were performed using a 3D Helmholtz code. All simulations account for the loss and
dispersion of the metal at these wavelengths. FSSs with narrowband and broadband capabilities and for polarizing and
non-polarizing applications were designed.
We will show measured results of both reflection and transmission over a broad spectral (covering all of the mid and
thermal infrared) and angular (near normal to near grazing) range. These measurements compare favorably with the
In this paper, we describe progress towards a multi-color spectrometer and radiometer based upon an active resonant subwavelength grating (RSG). This active RSG component acts as a tunable high-speed optical filter that allows device miniaturization and ruggedization not realizable using current sensors with conventional bulk optics. Furthermore, the geometrical characteristics of the device allow for inherently high speed operation. Because of the small critical dimensions of the RSG devices, the fabrication of these sensors can prove challenging. However, we utilize the state-of-the-art capabilities at Sandia National Laboratories to realize these subwavelength grating devices. This work also leverages previous work on passive RSG devices with greater than 98% efficiency and ~1nm FWHM.
Rigorous coupled wave analysis has been utilized to design RSG devices with PLZT, PMN-PT and BaTiO3 electrooptic thin films on sapphire substrates. The simulated interdigitated electrode configuration achieves field strengths around 3×10<sup>7</sup> V/m. This translates to an increase in the refractive index of 0.05 with a 40V bias potential resulting in a 90% contrast of the modulated optical signal. We have fabricated several active RSG devices on selected electro-optic materials and we discuss the latest experimental results on these devices with variable electrostatic bias and a tunable wavelength source around 1.5μm. Finally, we present the proposed data acquisition hardware and system integration plans.
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 designed, fabricated, and tested surface-plasmon-based transmissive coatings in the MWIR (mid wave infrared) and
LWIR (long wave infrared). This method offers certain advantages over current coatings technologies such as thin-film
stacks and two-dimensional surface structuring (e.g. motheyes) while exploring an entirely different physical mechanism
for achieving transmission.
Thin-film stack technology relies on interference between layers of the stack, and often many layers are required for high
efficiency performance. Two-dimensional surface structuring can optimize transmission over a broad spectral and
angular domain<sup>1</sup>. Here the physical mechanism is an effective index matching between air and the substrate due to
subwavelength surface features, such as tall pyramids. These pyramids must have a high-aspect ratio, resulting in a
surface of many tall thin features, which may not be mechanically robust.
In this work, we created a transmissive surface out of a metal skin perforated with an array of subwavelength apertures.
The surface is the infrared analog of a frequency selective surface (FSS) common in the microwave regime. Such
perforated metal surfaces are predicted to have nearly 100% transmission over selected wavelength and angular ranges.
These ranges are determined by array geometry, period, and aperture size and shape, allowing the designer considerable
freedom. Array geometry and aperture shape were investigated for tailoring spectral features.
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.
We present the design and initial fabrication for a wavelength-agile, high-speed modulator that enables a long-term vision for the THz Scannerless Range Imaging (SRI) sensor. This modulator takes the place of the currently utilized SRI micro-channel plate which is limited to photocathode sensitive wavelengths (primarily in the visible and near-IR regimes).
The new component is an active Resonant Subwavelength Grating (RSG). An RSG functions as an extremely narrow wavelength and angular band reflector, or mode selector. Theoretical studies predict that the infinite, laterally-extended RSG can reflect 100% of the resonant light while transmitting the balance of the other wavelengths. Previous experimental realization of these remarkable predictions has been impacted primarily by fabrication challenges. Even so, we have demonstrated large-area (1.0mm) passive RSG reflectivity as high as 100.2%, normalized to deposited gold. In this work, we transform the passive RSG design into an active laser-line modulator.
In a similar manner to the frequency selective surfaces commonly used in the microwave regime, we have designed antireflective surfaces in the mid-infrared (2-5 μm). Translation of microwave designs to the infrared is not trivial for several reasons. Properties of applicable IR materials are significantly different than their microwave counterparts. Additionally, the required feature sizes need a completely different fabrication methodology. Our surfaces are metallic, yet have a high-transmission angular and frequency passband. We take advantage of photon-plasmon interaction to maximize transmission through holes in the metal surface. Simulations have been completed using both rigorous coupled wave analysis and method of moments codes. The design process has followed a path that insures that we are able to fabricate the designed structures considering cases of normal and off-angle incidence. We designed our surfaces to be compatible with shapes that we will etch in silicon and then coat in gold: this process allows the greatest flexibility in etching shapes for vias while maintaining a metallic layer for plasmon propagation on the surface. We anticipate over 90% transmission in the infrared passband. Our design methodology would also be applicable to the 8-12 μm band.
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.
We have designed, fabricated, and tested large sheets of photonic bandgap (PBG) material that have a "cubic array of cubes" structure. Structures with bandgaps in two wavebands have been fabricated: the thermal IR (8-12μm) and the visible/near IR (0.6-2.5μm). A thermal-IR PBG can modify the emission properties of structures for temperature control. Visible/near-IR PBGs can be used in photonic circuits and can improve illumination efficiency.
We report here on an effort to design and fabricate a polarization splitter that utilizes form-birefringence to disperse an input beam as a function of polarization content as well as wavelength spectrum. Our approach is unique in the polarization beam splitting geometry and the potential for tailoring the polarized beams' phase fronts to correct aberrations or add focusing power. A first cut design could be realized with a chirped duty cycle grating at a single etch depth. However, this approach presents a considerable fabrication obstacle since etch depths are a strong function of feature size, or grating period. We fabricated a period of 1.0 micron form-birefringent component, with a nominal depth of 1.7 microns, in GaAs using a CAIBE system with a 2-inch ion beam source diameter. The gas flows, ion energy, and sample temperature were all optimized to yield the desired etch profile.
We will discuss the fabrication of several diffractive optical elements (DOEs) for projects at Sandia National Laboratories, which highlight the relative importance of subwavelength surface texture in the componentsi’ performance. This surface texture is in addition to the larger, anisotropic DOE features that manipulate the propagating orders, and is commonly referred to as grass. Surface texture on amorphous or multi-crystalline material is readily apparent in a scanning electron micrograph and is often an unavoidable consequence of the reactive ion etch (RIE) process. Contributing factors are mask erosion, self-masking, and material non-uniformity. In this presentation, we describe and quantify the effects of unavoidable and deliberate surface texture through several projects in progress at Sandia National Laboratories.
With the goal of a portable diagnostic system in mind, we have designed a disposable platform for DNA detection. Surface micromachining using the SwIFT process at Sandia National Laboratories was used to make the new device, combining a waveguide, grating optics, heating structures, on-chip pumping, and microfluidics in a disposable package. PDMS microfluidic channels are integrated with the surface micromachined device to enable higher flow rates and added fluid complexity. Work on DNA hybridization under flow is presented, as applies to the function of the sensor. A description of the platform covering heating of the waveguide surface, laser coupling into the waveguide using grating optics, attachment chemistry for the sensor surface, and sealing of the PDMS microfluidic system to the device is given.
A current micro-optical system project at Sandia National Laboratories employs an array of resonant subwavelength gratings (RSGs). An RSG functions as an extremely narrow wavelength and angular band reflector, or mode selector. Theoretical studies predict that the infinite, laterally-extended RSG can reflect 100% of the resonant light while transmitting the balance of the other wavelengths. Experimental realization of these remarkable predictions has been impacted primarily by fabrication challenges. Even so, we will present large area (1.0mm) RSG reflectivities as high as 100.2%, normalized to deposited gold. Broad use of the RSG will only truly occur in an accessible micro-optical system. The program at Sandia is a normal incidence array configuration of RSGs where each array element resonates with a distinct wavelength to act as a dense array of wavelength- and mode-selective reflectors. Because of the array configuration, RSGs can be matched to an array of pixels, detectors, or chemical/biological cells for integrated optical sensing. Micro-optical system considerations impact the ideal, large area RSG performance by requiring finite extent devices and robust materials for the appropriate wavelength. Experimental measurements are presented that demonstrate the component response as a function of decreasing RSG aperture dimension and off-normal input angular incidence.
Resonant subwavelength gratings (RSGs) may be used as narrow-band wavelength and angular reflectors. Rigorous coupled wave analysis (RCWA) predicts 100% reflectivity at the resonant frequency of an incident plane wave from an RSG of infinite extent. For devices of finite extent or for devices illuminated with a finite beam, the peak reflectivity drops, coupled with a broadening of the peak. More complex numerical methods are required to model these finite effects. We have modeled finite devices and finite beams with a two-dimensional finite difference Helmholtz equation. The effect of finite grating aperture and finite beam size are investigated. Specific cases considered include Gaussian beam illumination of an infinite grating, Gaussian illumination of a finite grating, and plane wave illumination of an apertured grating. For a wide grating with a finite Gaussian beam, it is found that the reflectivity is an exponential function of the grating width. Likewise, for an apertured grating the reflectivity shows an exponential decay with narrowing aperture size. Results are compared to other methods, including plane wave decomposition of Gaussian beams using RCWA for the case of a finite input beam, and a semi-analytical techniques for the case of the apertured grating.
The design and on-going fabrication of an opto-electro- mechanical microsystem that acts as a four-function optical fiber switch will be presented. The four functions of the 2x2 optical switch include 1) Normal mode, where channel A and channel B pass light straight through, 2) Loopback mode, where light originating in channel A is detected in the B leg, 3) Monitor A mode, where a probe pulse is inserted into the channel B and any reflections are detected in the A leg, and 4) Monitor B mode, the compliment of 3) above. High spatial frequency gratings etched in fused silica configure the light beams through free-space substrate-mode propagation. The design for an OTDR-mode transmission grating that normally passes light from an incidence angle of 45 degrees within the silica substrate as well as passes light from a normal incidence straight through the silica will be discussed. A miniature commercial drive motor, positioned with LIGA alignment plates, rotates the optical grating disk into one of the four implemented function positions. The impact of required tolerances and packaging limitations on the optics, LIGA alignment plates, and the complete microsystem will be presented.