The future need for more bandwidth forces the development of optical transmission solutions for rack-to-rack, boardto-
board and chip-to-chip interconnects. The goals are significant reduction of power consumption, highest density
and potential for bandwidth scalability to overcome the limitations of the systems today with mostly copper based
interconnects. For system integration the enabling of thin glass as a substrate material for electro-optical components
with integrated micro-optics for efficient light coupling to integrated optical waveguides or fibers is becoming
important. Our glass based packaging approach merges micro-system packaging and glass integrated optics. This
kind of packaging consists of a thin glass substrate with integrated micro lenses providing a platform for photonic
component assembly and optical fiber or waveguide interconnection. Thin glass is commercially available in panel
and wafer size and characterizes excellent optical and high frequency properties. That makes it perfect for
microsystem packaging. A suitable micro lens approach has to be comparable with different commercial glasses and
withstand post-processing like soldering. A benefit of using laser ablated Fresnel lenses is the planar integration
capability in the substrate for highest integration density. In the paper we introduce our glass based packaging
concept and the Fresnel lens design for different scenarios like chip-to-fiber, chip-to-optical-printed-circuit-board
coupling. Based on the design the Fresnel lenses were fabricated by using a 157 nm fluorine laser ablation system.
Using planar waveguides as a platform for optical biosensors allows an efficient and selective fluorescence excitation in
close proximity to the waveguide surface. Usually, the fluorescence light that is emitted in the space above the sensor
chip is collected and analyzed by suitable free space optics and a detector. Due to the vicinity of the fluorescent
molecules to the interface of the waveguide layer, a substantial part of the fluorescence light is coupled back into and
collected by the waveguide. The coupling efficiency depends on position, environment and orientation of the molecules.
The utilization of this signal for fluorescence detection and analysis can allow a significant simplification of the optical
instrumentation. We present a fundamental investigation of the fluorescence collection efficiency into the waveguide by
theoretical and experimental means.
Beam shaping at the output of optical fibers is required in a variety of applications including optical sensors, telecommunication devices and medical applications. We present a laser micro-machining technique for the fabrication of micro-lenses directly upon the end face of silica fibers using a F2-laser processing station. Ablation is performed in a mask projection arrangement with 25x demagnification. A mask with an occluded circular beam shape is imaged perpendicular to the fiber axis. The fiber is rotated axially while the laser cuts through the fiber, yielding a spherically shaped tip with radius defined by the mask dimensions. Strong 157 nm absorption by the silica glass facilitates precise structuring without micro-crack formation. The quality of the fiber-lenses is characterized by AFM, SEM and by analysing the beam profile at the fiber output.
The decorrelation of the characteristic speckle pattern, produced by the scattering of coherent light from a random rough surface, is used to monitor changes in the microtopography of the surface. In a basic optical setup minute alterations down to a few nanometers can be measured. To enlighten the basic relations between the speckle field decorrelation and the surface changes a theoretical model is developed, numerical calculations are carried out and comparisons with high resolution AFM measurements on two frozen states of a surface process are undertaken. Whereas the reproducibility of the AFM measurement turns out to be not precise enough to measure nanometer changes on a micrometer scale rough surface, the theoretical model is consistent with results gained from experimental variation of wavelength and angle of illumination and a-priori knowledge about the surface. It is then used to obtain information about magnitude, time constants and statistical parameters of a corrosion process.
A sensitized TV-holography system combined with acoustical object excitation is shown to be a new powerful tool for remote monitoring of detached plaster areas in historical murals. Some experimental results obtained in the laboratory and at historical sties will be presented and compared with results received with traditional percussion method.
Deterioration of historical murals often leads to partial detachments of the paint carrying plaster layers. To identify such regions an acousto-optical method is described. Loose portions of the plaster are excited by sound waves and the resulting vibrations are detected by sensitized analog TV-holography.
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