In this presentation we discuss a new type of optical microscope that is capable of obtaining spectral and spatial
information from biological tissue samples. The current system uses multiplexed volume holograms to probe multiple
depths of a tissue sample without the need for scanning. This greatly simplifies the instrument and should allow it to be
adapted for laproscopic applications. The technique can be combined with fluorescent dye markers to identify cancerous
A comparison of static and single-axis tracking holographic planar concentrator systems is made. Tracking is used as a
design parameter that can provide additional degrees of freedom in the spectrum and uniformity of the beam
illuminating the photovoltaic cell surface. These parameters impact the energy yield of the system. An overview of
these factors and an estimate of the cost differences for the two systems will be presented.
A volume holographic imaging system maps the spectral-spatial, four-dimensional data set to a two-dimensional image
array, allowing simultaneous imaging of multiple projections of the spatial and spectral content from different depths
within biological tissue samples. The volume holographic imaging system uses dispersion to increase the lateral field of
view. This results in spectral performance characteristics that are unique to volume holographic imaging systems. We
review the principle of operation of the volume holographic imaging system and aberrations due to the dispersive nature
of a volume hologram. We report our experimental results of spectral performance present in a volume holographic
In this paper we review volume holographic imaging techniques for 3D imaging. Our investigation focuses on
holographic imaging systems that operate with broadband illuminator sources. This type of imaging system has the
advantage of reducing or eliminating the need for scanning along lateral or axial direction. However, the utilization
of broadband illuminator source produces significant reduction in depth resolution. Modeling and experiments are
presented to describe the dependence of lateral and depth resolution on the hologram parameters.
A design methodology for low-concentration ratio holographic solar concentrators with one-axis tracking is investigated. This methodology maximizes the energy collected by cascaded holographic gratings and reduces diffracted beam cross talk between gratings. Several types of transmission gratings, optimized to work with single-axis tracking systems, are used in a cascaded configuration to concentrate a large fraction of the useable solar spectrum on the surface of photovoltaic cells. A model is developed that determines the energy yield of the holographic planar concentrator (HPC). Good agreement is found between simulation and measurement of a prototype system. Simulation of an optimized HPC design shows that 80% optical efficiency at 2X geometric concentration ratio is possible. The acceptance angle in the nontracking direction is ±65 deg, and a ±16-deg tracking tolerance is sufficient to maintain 80% of the maximum optical efficiency. Simulation also shows that the single-axis tracking HPC system has a 43.8% increase in energy yield compared to a nontracking holographic solar concentrator.
In this presentation we evaluate the energy collection efficiency and energy yield of different holographic planar
concentrator designs. The holographic planar concentrator replaces expensive photovoltaic cell material with
holographic collectors that cost approximately 1% of the photovoltaic material. An analysis is performed using a
combination of raytracing and coupled wave theory. Other loss factors such as Fresnel reflection and polarization are
also incorporated. The performance of single gratings is optimized to maximize the spectral and angular bandwidth that
matches the spectral responsivity of different photovoltaic devices. Multiple grating collectors are also modeled to
maximize energy collection over the course of a year accommodating the movement of the sun. The results show that
approximately half of the light illuminating the hologram can directly be collected by diffraction and directed to the
photovoltaic cell. A test system is evaluated and the experimental results compare well with the analysis.
The spatial-spectral holographic imaging system (S2-VHIS) is a promising alternative to confocal microscopy due to its capabilities to simultaneously image several sample depths with high resolution. However, the field of view of previously presented S2-VHIS prototypes has been restricted to less than 200 µm. We present experimental results of an improved S2-VHIS design that has a field of view of ~1 mm while maintaining high resolution and dynamic range.
Holographic elements have several unique features that make them attractive for solar collector and concentrator
systems. These properties include the ability to diffract light at large deflection angles, Bragg selectivity, grating
multiplexing, and angle-wavelength matching. In this presentation we review how these properties can be applied to
solar collection and concentrator systems. An algorithm is presented for analyzing the energy collection properties of
holographic concentrators in specific geometries and is applied to a planar collection format. Holographic elements are
shown to have advantages for low concentration ratio solar concentrator systems.
With the ever increasing bandwidth of optical communications systems, it is critical to allow multiple users to access the available bandwidth. Code division multiplexed access (CDMA) is especially attractive in local area networks due to the large number of subscribers possible, the security and the simple architecture. Here we presents novel encoding/decoding structures using anti-symmetric gratings with application in optical CDMA and optical encryption.
Optical add-drop multiplexers (OADMs) based on grating-assisted null couplers are excellent candidates for low-cost wavelength division multiplexed (WDM) systems. These devices potentially offer exceptional operating characteristics in a compact layout that does not require circulators. Optimization analysis has been already presented. However, inherent fabrication errors either in the null coupler or in the grating increase the crosstalk at the drop port. In this paper, a simple model that relates the optical signal-to-noise ratio (OSNR) of the OADM to the null-coupler and grating parameters is presented. Based on that model, we propose two new approaches to increase the OSNR at the drop at output ports, when fabrication errors are present. One approach optimizes the grating angle to minimize the noise produced by spurious reflection without mode conversion. The other shifts these reflections out of the bandwidth used by the WDM system. The advantages and limitations of these approaches are analyzed.
Optical add/drop multiplexers (OADM) based on asymmetric y-branches and tilted gratings can be easily fabricated using ion exchange techniques and photosensitive glasses. These devices offer excellent operating characteristics. However, optimum OADM performance depends critically on the angle of the tilted grating. In this paper, results from fabrication and modeling are compared for the ion exchange process using four different angles of the tilted grating. The transmission spectra for the fabricated and simulated OADMs show an excellent agreement.