Super-directional light emission and emission reversal from micro cavity arrays

Optical microdisk cavities with certain asymmetric shapes are known to possess unidirectional far-field emission properties. Here, we investigate arrays of these dielectric microresonators with respect to their emission properties resulting from the coherent behaviour of the coupled constituents. This approach is inspired by electronic mesoscopic physics where the additional interference effects are known to enhance the properties of the individual system. As an example we study the linear arrangement of nominally identical Lima\c{c}on-shaped cavities and find mostly an increase of the portion of directional emitted light while its angular spread is largely diminished from 20 degrees for the single cavity to about 3 degrees for a linear array of 10 Lima\c{c}on resonators, in fair agreement with a simple array model. Moreover, by varying the inter-cavity distance we observe windows of reversion of the emission directionality and super-directionality that can be interesting for applications. We introduce a generalized array factor model that takes the coupling into account.Comment: 5 pages, 5 figures, supplemental materia

Design method for zoom systems based on tunable lenses

It is well known that tunable lenses, with refractive power that can be varied, e.g., by changing the curvature of a membrane, can replace the motion of lens groups in zoom systems. Similar to classical zoom systems, the performance of these systems is heavily influenced by the fundamental first-order layout. Moreover, the first-order layout sets the most important requirements for the employed tunable lenses. In this contribution, we present a method for the analysis of a large number of possible first-order solutions for typical requirements and for the selection of the most promising layouts. The first-order solution space is mapped, allowing the layouts to be automatically filtered and plotted depending on pre-defined characteristics. Ray tracing of the marginal and chief rays combined with the traditional thin lens aberration theory provide efficient estimations of the expected installation space requirements and performance for each first-order layout. Using an example, we demonstrate good agreement between these estimations and the corresponding real lens layout, optimized by commercial raytracing software. The presented design method for zoom systems based on tunable lenses is compared with similar approaches for classical zoom lenses

Lau effect using LED array for lithography

Illumination with LEDs is of increasing interest in imaging and lithography. In particular, compared to lasers, LEDs are temporally and spatially incoherent, so that speckle effects can be avoided by the application of LEDs. Besides, LED arrays are qualified due to their high optical output power. However, LED arrays have not been widely used for investigating optical effects, e.g., the Lau effect. In this paper, we propose the application of an LED array for realizing the Lau effect by taking into account the influence of the coherence properties of illumination on the Lau effect. Using spatially incoherent illumination with the LED array or a single LED, triangular distributed Lau fringes can be obtained. We apply the obtained Lau fringes in the optical lithography to produce analog structures. Compared to a single LED, the Lau fringes using the LED array have significantly higher intensities. Hence, the exposure time in the lithography process is largely reduced

Das 9e Young Physicists' Tournament

Das International Young Physicists’ Tournament (IYPT) ist einer der großen internationalen Physikwettbewerbe. Das IYPT zeichnet sich in besonderer Weise dadurch aus, dass es nicht nur die erfolgreiche Bearbeitung einer großen Zahl sehr offen formulierter Forschungsaufgaben verlangt, sondern auch einen starken Fokus auf die Präsentation und die Diskussion der Ergebnisse legt.Im Rahmen eines Unterrichtsprojekts wurde der Versuch unternommen, das Wettbewerbsformat des IYPT auf den Einsatz in einer neunten Klasse eines Gymnasiums zu übertragen. Die Durchführung ergab neben den erwarteten positiven Effekten hinsichtlich der Motivation unter anderem sehr hilfreiche Beobachtungen hinsichtlich der Stärken und Schwächen des vorhergehenden Physikunterrichts

Optische Systeme im Phasenraumbild

Optical Microcavities are established model systems for non-linear dynamics. This motivates their description in phase space using Husimi-Functions, which give insight into the main radiation directions and the mode distribution at the dielectric interface. In this work, we generalize the application of Husimi-Functions to coupled microcavity systems

Resonant diffraction gratings with polarization-dependent efficiencies

Subwavelength-structures with different fill factors in the lateral dimensions result in unique phase shifts for the different polarization states of transmitted light.By using this additional degree of freedom for diffractive optical elements, we yield additional functionalities for compact optical systems with DOEs. As a fully operable example we present a binary subwavelength-grating which acts as a polarizing beamsplitter for TE- and TM-polarization over a wide range of incidence angles. We show our design approach, the manufacturing process with Soft-UV-Nanoimprint-Technology, as well as experimental results. We will also lay out possibilities for the design and application of multilevel polarization-functionalized gratings

Das 9e Young Physicists' Tournament

Das International Young Physicists’ Tournament (IYPT) ist einer der großen internationalen Physikwettbewerbe. Das IYPT zeichnet sich in besonderer Weise dadurch aus, dass es nicht nur die erfolgreiche Bearbeitung einer großen Zahl sehr offen formulierter Forschungsaufgaben verlangt, sondern auch einen starken Fokus auf die Präsentation und die Diskussion der Ergebnisse legt.Im Rahmen eines Unterrichtsprojekts wurde der Versuch unternommen, das Wettbewerbsformat des IYPT auf den Einsatz in einer neunten Klasse eines Gymnasiums zu übertragen. Die Durchführung ergab neben den erwarteten positiven Effekten hinsichtlich der Motivation unter anderem sehr hilfreiche Beobachtungen hinsichtlich der Stärken und Schwächen des vorhergehenden Physikunterrichts

Nano-imprinted subwavelength gratings as polarizing beamsplitters

Polarizing beamsplitters have numerous applications in optical systems, such as systems for freeform surface metrology. They are classically manufactured from birefringent materials or with stacks of dielectric coatings. We present a binary subwavelength-structured form-birefringent diffraction grating, which acts as a polarizing beamsplitter for a wide range of incidence angles -30°…+30°. We refine the general design method for such hybrid gratings. We furthermore demonstrate the manufacturing steps with Soft-UV-Nanoimprint-Lithography, as well as the experimental verification, that the structure reliably acts as a polarizing beamsplitter. The experimental results show a contrast in efficiency for TE- and TM-polarization of up to 1:18 in the first order, and 34:1 in the zeroth order. The grating potentially enables us to realize integrated compact optical measurement systems, such as common-path interferometers