48 research outputs found
Stochastic light concentration from 3D to 2D reveals ultraweak chemi- and bioluminescence
For countless applications in science and technology, light must be concentrated, and concentration is classically achieved with reflective and refractive elements. However, there is so far no efficient way, with a 2D detector, to detect photons produced inside an extended volume with a broad or isotropic angular distribution. Here, with theory and experiment, we propose to stochastically transform and concentrate a volume into a smaller surface, using a high- albedo Ulbricht cavity and a small exit orifice through cavity walls. A 3D gas of photons produced inside the cavity is transformed with a 50% number efficiency into a 2D Lambertian emitting orifice with maximal radiance and a much smaller size. With high-albedo quartz-powder cavity walls ( P = 99.94%), the orifice area is 1/( 1 - P) approximate to 1600 times smaller than the walls' area. When coupled to a detectivity-optimized photon-counter ( D = 0.015 photon- 1 s1/ 2 cm) the detection limit is 110 photon s- 1 L- 1. Thanks to this unprecedented sensitivity, we could detect the luminescence produced by the non-catalytic disproportionation of hydrogen peroxide in pure water, which has not been observed so far. We could also detect the ultraweak bioluminescence produced by yeast cells at the onset of their growth. Our work opens new perspectives for studying ultraweak luminescence, and the concept of stochastic 3D/2D conjugation should help design novel light detection methods for large samples or diluted emitters
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Nonuniform Liouville transformers for quasi-homogeneous optical fields. Final technical report, September 25, 1989--January 22, 1993
During the last two decades, there have been dramatic improvements in the development of optical sources. Examples of this development range from semiconductor laser diodes to free electron beam lasers and synchrotron radiation. Before these developments, standards for the measurement of basic optical parameters (quantities) were less demanding. Now, however, there is a fundamental need for new, reliable methods for providing fast quantitative results for a very broad variety of optical systems and sources. This is particularly true for partially coherent optical beams, since all optical sources are either fully or partially spatially coherent (including Lambertian sources). Until now, there has been no satisfactory solution to this problem. During the last two decades, however, the foundations of physical radiometry have been developed by Walther, Wolf and co-workers. By integrating physical optics, statistical optics and conventional radiometry, this body of work provides necessary tools for the evaluation of radiometric quantities for partially coherent optical beams propagating through optical systems. In this program, Physical Optics Corporation (POC) demonstrated the viability of such a radiometric approach for the specific case of generalized energy concentrators called Liouville transformers. We believe that this radiometric approach is necessary to fully characterize any type of optical system since it takes into account the partial coherence of radiation. 90 refs., 57 figs., 4 tabs
Polymer microstructure waveguides on alumina and beryllium oxide substrates for optical inteconnection
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Reconfigurable switching network for multimode fiber arrays
The authors report the first electro-optic switching device compatible with multimode fibers. A 1-to-many cascaded reconfigurable interconnection was built. A thin glass substrate was used as the guiding medium which provides not only higher coupling efficiency from multi-mode fiber to waveguide but also better tolerance of phase matching conditions. Involvement of a TIR hologram and multi-mode waveguide eliminates interface problems between fibers and waveguides. The DCG holographic material has proven to be reliable from -180 degree C to +200 degree C. Survivability of such an electro-optic system in harsh environments is further ensured
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Five-channel polymer waveguide wavelength division demultiplexer for the near infrared
A five-channel wavelength division demultiplexer (WDDM) fabricated in polymer gelatin waveguides and operating over a 100-nm bandwidth centered at 770 nm in the near infrared is discussed. The device has a maximum diffraction efficiency of 80% at 730 nm, has a spectral bandwidth of 17+or-3 nm per channel, and effectively utilizes a portion of the large optical transparency bandwidth ( approximately 2400 nm) of the photo-lime gelatin polymer material at laser diode wavelengths. High-channel-density WDDM devices at longer infrared wavelengths should be possible.<
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