SST is developing a new Dish CPV dense array system that overcomes the flux uniformity requirement of previous
designs. The ability to operate without flux uniformity relaxes the precision requirements of primary collector optics and eliminates homogenizing optics previously required for dense array CPV. Array design can be configured for dish and tower/heliostat systems developed for thermal CSP applications. The design uses industry standard CPV cells and
manufacturing materials and methods for minimum cost and high reliability. Nominal input flux to the array for full
power is about 250 suns. Internal array optics increase flux to the cells to about 1200 suns. Linear optics provide
additional concentration, permit novel use of commercial glass production methods and facilitate power collection
design that is integrated with dynamic power conversion and maximum power point tracking (MPPT). Efficient power
hybrid packaging methods are used along with advanced liquid cooling “cold-plate” thermal management. Byproduct
“waste heat” can be provided for on-site CHP use. We report on the design approach and status of development with the
beginning of on-sun alpha testing of the first of 50 kW of CPV modules being produced.
Yb:YAG ceramic laser materials, fabricated by vacuum sintering technology, were
optically investigated within different laser set-up configurations. The established nanopowder
vacuum sintering process shows good potential for mass fabrication of multicomposite
ceramic laser materials with different dopant concentrations. 5%, 7%, 10%
single dopant and 7%/20% core-cladding multi-composite Yb:YAG materials were
fabricated and investigated. The highest measured slope efficiency, for the composite
ceramic laser materials was 81%, at 1030 nm emission wavelength, similar to Yb:YAG
This paper discusses the use of diffractive optical elements (DOEs) and micro-optics
fabricated by precise pressing in glass for beam shaping of high-power diode lasers.
The DOEs are used to diffract the light into the point of interest and to improve the laser
beam quality. We have realized circular, flat-top and multi-beam intensity profiles. The
highest measured diffraction efficiency was higher than 95 %. The new established
fabrication process has potential for mass production of DOEs. SCHOTT's precision
glass molding process guarantees a very constant quality over the complete production
This paper discusses the precise pressing technology for the fabrication of diffractive optical elements (DOEs). The new established fabrication process allows mass production of DOEs in high homogeneous optical glasses. Our precise pressing process guarantees a very constant quality over the complete production chain. Glass DOEs made by SCHOTT AG are planar optical phase elements with highly accurate shape and efficiency. The blazed profile of the diffractive optical elements was approximated by a stepped profile with up to sixteen phase levels. The highest measured diffraction efficiency for sixteen level gratings was 95%.
Fluorescence techniques are known for their high sensitivity and are widely used as analytical tools and detection
methods for product and process control, material sciences, environmental and bio-technical analysis, molecular
genetics, cell biology, medical diagnostics and drug screening. According to DIN/ISO 17025 certified standards are
used for fluorescence diagnostics having the drawback of giving relative values for fluorescence intensities only.
Therefore reference materials for a quantitative characterization have to be related directly to the materials under
investigation. In order to evaluate these figures it is necessary to calculate absolute numbers like absorption/excitation
cross section and quantum yield. This can be done for different types of dopants in different materials like glass, glass
ceramics, crystals or nano crystalline material embedded in polymer matrices. Here we consider a special type of glass
ceramic with Ce doped YAG as the main crystalline phase. This material has been developed for the generation of white
light realized by a blue 460 nm semiconductor transition using a yellow phosphor or converter material respectively.
Our glass ceramic is a pure solid state solution for a yellow phosphor. For the production of such a kind of material a
well controlled thermal treatment is employed to transfer the original glass into a glass ceramic with a specific
crystalline phase. In our material Ce doped YAG crystallites of a size of several µm are embedded in a matrix of a
residual glass. We present chemical, structural and spectroscopic properties of our material. Based on this we will
discuss design options for white LED's with respect to heat management, scattering regime, reflection losses, chemical
durability and stability against blue and UV radiation, which evolve from our recently developed material. In this paper
we present first results on our approaches to evaluate quantum yield and light output. Used diagnostics are fluorescence
(steady state, decay time) and absorption (remission, absorption) spectroscopy working in different temperature regimes
(10 - 350 K) of the measured samples in order to get a microscopic view of the relevant physical processes and to prove
the correctness of the obtained data.
Properties of a new rare-earth doped heavy metal oxide containing silicate glass are presented. The glass has potential for fabrication of ultra-short wideband fiber and planar waveguide amplifiers. We report specific results for a fiber amplifier geometry, discussing achieved improvements in device compactness (Giles gain g* = 210 dB/m allowing up to 100 times shorter fiber) and amplification bandwidth (50% more bandwidth in C-/L-band) compared to the conventional EDFA. We also access the potential of this material for fabrication of active planar integrated waveguide devices.
A novel optical pickup based on DOEs is proposed and first optical key elements are designed and fabricated. The DOE- pickup enables multi-focus imaging and speeds up the data transfer rate. Parallel reading of many tracks and two or more superimposed memory layers is possible. Our measurements revealed, that the efficiencies and the optical performances of the DOEs are suitable for the implementation in an optical DVD-pickup.
A programmable arrayed-waveguide grating demultiplexer is presented. The device shows new functionalities, like a tunable center frequency and a variable transmission characteristic. The measured crosstalk was lower than -30 dB.
We report on a new integrated optical pickup for double layer DVD's. The optics is almost integrated by means of diffractive optical elements. Dual focus as well as focal control is done by a liquid crystal cell.
A new type of wavelength division demultiplexer (DEMUX), which consists of a pair of diffractive optical elements integrated on one substrate, is presented. The 3 dB-resolution of the DEMUX is about 2 nm and the measured losses are about -3.5 db at 1.55-micrometers wavelength. To simplify the fabrication process of the integrated diffractive optical elements, a new 3D structure replication technique is proposed.
The use of thin-film deposition in the fabrication of antireflection-coated diffractive optical elements is discussed. The antireflection coatings for these diffractive elements are optimized on the basis of an angular spectrum approach and the method of characteristic matrices. A minimum reflectivity as low as 1 x 10-4 is realized using in situ controlled multilayers of TiO2 and SiO2. The blazed profile of the diftractive optical elements is approximated by a stepped profile with up to 32 phase levels. The highest measured diffraction efficiency for 32-level Fresnel zone lenses was 97%.
Multi-level approximated Fresnel zone lenses with reduced level numbers in the outer zones are investigated and compared with Fresnel zone lenses of unique level numbers over the whole lens. Calculations of the fabrication error effects on diffraction efficiency for both lens types are performed. Measurements of focussing efficiency show that. especially for Gaussian beam illumination, segmented Fresnel zone lenses can reach nearly as high focussing efficiencies as normal Fresnel zone lenses. Arrays of segmented lenses can be fabricated using only one binary Fresnel zone lens mask with the aid of a modified optical stepper with fixed scaling down factors in the ratio of 1: 1/(root)2 from one to the next step of pattern transfer in the lithographic process. The fabrication of such lenses could be advantageous because the generation of precise e-beam written masks with a large number of binary ring zones is time consuming and expensive.
A new integrated device for coupling light into waveguides or deflecting and focusing the light from waveguide elements is proposed. The device shows flexible design possibilities and compact dimensions. It consists of a combination of a refractive cylindrical microlens and an integrated planar Fresnel zone lens. High coupling efficiencies can be expected by approaching a kinoform profile with multiphase steps. The Fresnel zone lenses and the cylindrical microlenses were fabricated by thin film deposition of SiOx-multilayers. The measured spot-sizes of the fabricated microlenses are close to the diffraction limited values. A theoretical analysis of coupling tolerances indicates that integrated planar Fresnel zone lens couplers are useful for optical free space interconnects.
Blazed Fresnel zone lenses for the 1.5-μm wavelength were fabricated in quartz glass by means of microstructuring technology. The blazed profile in each zone of the lenses was approximated by two, four, and eight discrete levels. The effects of fabrication errors, such as depth and alignment errors, on the diffraction efficiency of the different Fresnel zone lenses were investigated. Further the location and intensity of the parasitic foci appearing due to the discrete level approximation are calculated. Theoretical results along with experimental measurements are presented.
Two-dimensional arrays of Fresnel zone microlenses were fabricated and coated with antireflection layers by an ion beam sputter deposition technique. The reflection of these lenses was analyzed on the basis of an angular spectrum approach for different substrate materials. A minimum reflectivity as low as 2 x 10-4 was realized by means of in situ controlled multilayers of TiO2 and SiO2. The lenses have a circular aperture of 2 mm and different focal lengths for the wavelengths of 1.52 and 0.63 μm, respectively. The kinoform profile in each zone of the Fresnel zone lenses was approximated by an eight-level profile. Such stepped profiles were realized with several masks written with an electron beam and transferred by photolithographic technology. Our measurements reveal that the spot sizes of the fabricated microlenses are close to the diffraction-limited values, and the highest measured diffraction efficiencies for the eight-level structures are greater than 80%.
Arrays of two different sizes, each consisting of 16 by 16 blazed Fresnel zone lenses, were fabricated in quartz glass by means of microstructuring techniques. The lenses were designed for free space optical interconnection networks operating in the IR. In order to achieve high diffraction efficiencies the kinoform profile of the microlenses was approximated by a staircase-like profile. The fabrication of the lenses involved multiple steps of repeated pattern transfer by photolithography and successive reactive ion etching. We fabricated Fresnel zone lenses with 16 levels per zone and with different focal lengths. The individual elements of the two arrays have circular and square apertures with a diameter of 2 mm and 200 micrometers respectively and were designed to operate at a wavelength of 1.52 micrometers .
Blazed Fresnel zone microlens arrays were fabricated by Ion-Beam-Sputter deposition technique on different substrate materials. The lenses have circular and square apertures with the smallest width of 0.2 mm and different focal lengths for the wavelength of 1.52 micrometers and for the wavelength of 0.63 micrometers . The kinoform profile in each zone of the Fresnel zone lenses was approximated by a sixteen level profile. Such stepped profiles were realized with several masks, written with electron-beam and with photolithographic technology. The effects of fabrication errors, such as level heights, alignment and linewidths errors, on the diffraction efficiency were discussed. The microlenses were coated with an antireflection coating. The reflection of these lenses was analyzed on the basis of an angular spectrum approach. A minimum reflectivity as low as 2 X 10-4 was realized using in situ controlled multilayers of TiO2 and SiO2. Our measurements reveal, that the spot- sizes of the fabricated microlenses are close to the diffraction limited values, and the highest measured diffraction efficiency for the sixteen level structure is 96%.
Blazed Fresnel zone lenses for 1.5 micrometers wavelength were fabricated in quartz glass by means of microstructuring technology. The blazed profile in each zone of the lenses was approximated by 2, 4, and 8 discrete levels. The effects of fabrication errors, such as depth and alignment errors, on the diffraction efficiency of the different Fresnel zone lenses were investigated. Further the location and intensity of the parasitic foci appearing due to the discrete level approximation are calculated. Theoretical results along with experimental measurements are presented.
Holographic optical elements for interconnecting electronic switching stages with light of 1.5 micrometers wavelength are presented. These elements include deflection holograms recorded in dichromated gelatin for deflecting the light and diffractive spherical gratings fabricated by microstructuring for focusing and collimating the light. The diffraction efficiency of these elements can reach 90% and focused spot sizes can be within the diffraction limit.
Two dimensional arrays of Fresnel zone micro lenses were fabricated and coated with antireflection layers by ion-beam-sputter deposition technique. The thickness of the layers was controlled by a reflection-wideband-monitoring-system with high accuracy. The lenses have a circular aperture of 2 mm and focal lengths of 70 mm and 20 mm for the wavelength of 0.63 micrometers and focal lengths of 29 mm, 8 mm, and 5.6 mm for the wavelength of 1.52 micrometers . The blazed profile in each zone was approximated by an eight level profile. Such stepped profiles were recorded with several masks, written with e-beam and with photolithographic technology. Our measurements reveal that the spot-sizes of the fabricated microlenses are close to the diffraction limited values, and the diffraction efficiency for the eight level structure is 83 percent.