Voltage-controlled continuous tuning of the laser wavelength of an organic distributed feedback laser is demonstrated by incorporation of liquid crystals (LCs) in the top cladding layer. Orientation of the LCs and hence the modal refractive index are controlled by applying a lateral electrical field. Laser emission shifts by 4 nm at an applied voltage of 675 V. The device showed lasing thresholds of about 286 nJ per pulse. The tuning behaviour is analyzed by implementation of a voltage-dependent spatial LC director orientation profile in a slab waveguide model and solving the Bragg condition to obtain the voltage-dependent lasing wavelength.

In the growing field of pico-projectors, laser-based scanning systems may be advantageous over DLP- or LCoS-based imagers due to their potential for miniaturization, enhanced optical efficiency and cost reduction. The high energy density of a combined laser beam can, however, be hazardous to the human eye. Laser projection systems must therefore be identified with the laser class, depending on their maximum optical output power. This power limits the brightness of the displayed image, which is of particular interest for mobile applications. Various approaches to classifying laser devices by their wavelength and output power are described within the standards for laser safety. It is found that actual safety regulations cannot be directly applied to scanning systems. A detailed analysis of the optical conditions in terms of a two-dimensional extended light source is appropriate for the consideration of laser scanner devices. In this article, alternative ways of applying laser standards for scanning systems are discussed. The dependencies of maximum luminous flux from scanning system parameters are reviewed. It is shown that the evaluation of retinal light exposure in terms of existing laser regulations leads to an overestimation of the hazardous potential. Advanced investigations are proposed to support the definition of suitable criteria for the classification of laser scanning projectors.

Abstract-This article describes the revision of a lecture in optical engineering based on an evaluation of university teaching by students. Although this evaluation method is widely accepted and investigated, only few practically oriented reports on the deduction of teaching improvements from the evaluation's results on lectures are available. Our approach is the analysis of evaluation results by applying the principles of the explorative factor analysis (EFA). The changes that were derived from this analysis were mainly focused on a revision of the course structure and its presentation style.Finally, the impact of the modifications was measured by the evaluation of the lecture after the completed revision. The later evaluation showed improvements in all intended areas of interests illustrating the benefit of thorough revisions for the quality of teaching.evaluate optical components and simple systems with Zemax (widely-used optical ray tracing software) in ODL. During the period under consideration the quality index ratings for OE tutorials was 94.4 out of 100 (winter term 2011/12) and 92 out of 100 for ODL (winter term 2011/12). These evaluation results are quoted for the sake of completeness and to emphasize that there is no necessity to restructure the tutorials and ODL.Both are courses but influenced significantly by OE. Therefore, in the course of restructuring OE, care has to be taken that these do not suffer. III. EVALUATION PROCESSAt the Karlsruhe Institute of Technology (KIT) it is mandatory that every lecture is evaluated by students [9]. Students can rate a wide range of indicators (up to 40) affecting classroom teaching like the usage of black boards, clarity of the speaker, script quality and learning success among others, with an integer value from 1 (very good) to 5 (very bad). For each indicator an average (vI) is calculated. The university supports the lecturer with the averaged value of each indicator and its standard derivation but just a graphical depiction of the raw data.Therefore, it is hard to inspect dependencies from year to year, e.g. by t-test statistics.Five key indicators are taken as a base to calculate a teaching quality index called "Lehrqualitätsindex" (LQI). If the indicator's average is between 1.0 and 2.5, its quality value (sLQI) is judged as 100. Between 2.5 and 3.5 there is a 100 . If the average is between 3.5 and 5, its sLQI is 0. Five sLQIs are weighted with a number between 0 and 1 and then summed up for the calculation of the overall lecture's LQI. The LQI is usually calculated for lectures by the key indicators overall impression, work load, course structure, (perceived) dedication of the lecturer and his responsiveness (these indicators are applicable for our evaluation as well). It is flexible in a way that indicators used in computation of the quality index can be changed upon request to more fitting items. The calculation process is displayed in Fig. 1. The LQI is taken as a raw measuring tool for the departmental advisory boards to identify issues in teaching ...

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