Cold atom based quantum sensors require robust and miniaturized optical systems for applications on mobile platforms. A micro-integrated optical system (volume ∼25 mL) for trapping and manipulation of neutral atoms is presented. This setup focuses and precisely overlaps two high power laser beams (1064 nm, up to 2W total, wR = 34 µm) launched via a single-mode, polarization maintaining optical fiber, thereby realizing a crossed beam optical dipole trap (ODT). Adhesive bonding is qualified in application relevant geometries and material systems of micro-integrated optical systems for application on mobile platforms or space. Fused silica test blocks (bond area 2 × 4 mm2 ) are bonded with four different adhesives on silicon wafers. Theses samples are aged by thermal cycling (up to −55 °C to 150 °C) and/or gamma-radiation (10 000 mSv) and subsequently the bond strength is evaluated by die shear testing according to MIL-STD-883L. The influence of the environmental aging on the bond strength is presented, the failure mode and the influence of fillets discussed. In addition, the effects of plasma cleaning on the bond strength in this geometry is presented.
Employing compact quantum sensors in field or in space (e.g., small satellites) implies demanding requirements on components and integration technologies. Within our work on integrated sensors, we develop miniaturized, ultra-stable optical setups for optical cooling and trapping of cold atomic gases. Besides challenging demands on alignment precision, and thermo-mechanical durability, we specifically address ultra-high vacuum (UHV) compatibility of our integration technologies and optical components. A prototype design of an UHV-compatible, crossed beam optical dipole trap setup and its application within a cold atomic quantum sensor is described.
First qualification efforts on adhesive micro-integration technologies are presented. These tests are conducted in application-relevant geometries and material combinations common for micro-integrated optical setups. Adhesive aging will be investigated by thermal cycling or gamma radiation exposure. For vacuum compatibility testing, a versatile UHV testing system is currently being set up, enabling residual gas analysis and measurement of total gas rates down to 5•10-10mbar l/s at a base pressure of 10-11 mbar, exceeding the common ASTM E595 test.
Mode division multiplexing (MDM) could bring a technological progress in the field of optical telecommunication by increasing the data transmission bandwidth. A key challenge for enabling MDM lies in manufacturing of efficient and cost-effective mode–selective fiber couplers. The fiber grating based mode selective coupling approach is a method that is currently being under research in this context. In this work a novel process for manufacturing of asymmetric evanescent field polished couplers is presented which enables grating assisted mode selective coupling. In addition, we discuss the optical setup developed for characterization of these couplers.
Atomic layer deposition (ALD) has been widely studied in Micro-electronics due to its self-terminating property. ALD also grows film coatings with precise thickness and nodular-free structure, which are desirable properties for high power coatings. The depositing process was studied to produce uniform, stable and economic Al2O3 single layers. The layer properties relevant to high power laser industry were studied and compared with IBS Al2O3 single layers. ALD Al2O3 showed a stable growth of 0.104 nm/cycle, band gap energy of 6.5 eV and tensile stress of about 480 MPa. It also showed a low absorption at wavelength 1064 nm within several ppm, and LIDT above 30 J/cm2. These properties are superior to the reference IBS Al2O3 single layers and indicate a high versatility of ALD Al2O3 for high power coatings.
While automatic hot embossing systems are available for large- and small-scale productions of polymeric devices, one of the process challenges remains to be the manufacturing of precise, durable, and yet inexpensive hot embossing stamps. The use of metallic stamps manufactured by electroplating a photoresist pattern or by precision milling and their replication into silicone molds with UV-lithography, electroplating, and molding techniques is state of the art. Yet, there have been few, if any, thriving attempts to directly emboss polymers by means of bare photoresists, and in particular polyimide-based photoresists, without transferring the photoresist patterns into a different stamp material. We conduct a proof-of-concept by developing hot embossing stamps based on photosensitive polyimide. We focus primarily on the reliability of the aforementioned stamps throughout the hot embossing cycle and the fidelity of pattern transfer onto polymeric films for different microstructural patterns.
Transparent polymers with low glass transition temperatures are flexible materials and can serve as an optical waveguide or as substrates for the layer structure in applications such as humidity or temperature sensors. The background of this publication is the development of a laser-based process to bond silicon chips, which serve as emitter or detector in an optical system, on a substrate, without exposing the substrate to thermo-mechanical stress. Using transmission laser bonding of low-melting eutectic alloys, the necessary energy can be coupled into the fusion zone precisely to reduce the process time. In this paper, Si-chips with 52In48Sn and 66In34Bi layers are investigated to bond on rigid substrates. Experimental results are presented, which illustrate the mechanical stability of these compounds.
We investigated the impact of polymer substrates on the magnetic properties of soft magnetic thin films. Experiments were carried out to evaluate the performance of AMR (anisotropic magnetoresistive) sensors deposited on polymeric substrates and to give indications for the design of future sensors on flexible substrates. Sputtered permalloy (NiFe 81/19) was used as a soft magnetic thin film layer. As substrate materials, liquid polyimide precursors and DuPont Kapton® HN foil were examined. Surface roughness was determined for each substrate material. The dynamic of soft magnetic behavior of the permalloy thin films was observed in a homogenous alternating magnetic field. Resulting R-Hcurves were evaluated in regard to the magnitude of the magnetoresistive effect (ΔR / R0-ratio), as well as the resulting magnetic anisotropy of the tested samples. B-H-curves were obtained by means of a vibrating sample magnetometer (VSM).
This work addresses the design of an integrated energy harvesting system under production viewpoints. The system is developed to harvest energy from rotational movements. Therefore, a piezoelectric bending element – mounted on the rotational part - is actuated by magnetic force introduced by hard magnets installed in the fixed frame. This work concentrates on a high integration, the energy harvesting circuit, including rectifier, power management and storage is integrated in the structure of the bending harvester. Further the soft magnetic tip mass is equipped with a coil for electromagnetic energy harvesting; the necessary electronic is also integrated in the structure. The paper addresses the special systems demands for large scale production. The production technology for a small series of prototypes is explained in detail. Performance tests of the device conclude this study.
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