We report on a polymer-waveguide-based temperature sensing system relying on switchable molecular complexes. The polymer waveguide cladding is fabricated using a maskless lithographic optical system and replicated onto polymer material (i.e., PMMA) using a hot embossing device. An iron-amino-triazole molecular complex material (i.e., [Fe(Htrz)_2.85(NH₂-trz)_0.15](ClO₄)₂) is used to sense changes in ambient temperature. For this purpose, the core of the waveguide is filled with a mixture of core material (NOA68), and the molecular complex using doctor blading and UV curing is applied for solidification. The absorption spectrum of the molecular complex in the UV/VIS light range features two prominent absorption bands in the low-spin state. As temperature approaches room temperature, a spin-crossover transition occurs, and the molecular complex changes its color (i.e. spectral properties) from violet-pink to white. The measurement of the optical power transmitted through the waveguide as a function of temperature exhibits a memory effect with a hysteresis width of approx. 12 °C and sensitivity of 0.08 mW/°C. This enables optical rather than electronic temperature detection in environments where electromagnetic interference might influence the measurements.

Advances in illumination technology in the automotive industry are heading toward the use of coherent sources for adaptable and high-resolution head lamps as well as interior and rear-end lights. We present a cost-effective method to fabricate and design laser-based lighting systems for the rear end in automobiles and other vehicles. The design relies on using binary gratings to generate a desired intensity distribution. For cost-effective fabrication, an optical maskless UV lithography system that employs a spatial light modulator (SLM) for projection of the desired structure onto photoresist is introduced. To replicate the structures onto polymers like poly(methyl methacrylate) (PMMA), we use polydimethylsiloxane soft stamps and a hot embossing system. The experimental results show that the proposed design and fabrication process is promising for high-resolution rear-end lights that might be employed to project symbols or information to guide road users in future.

Information projection using laser-based illumination systems in the automotive area is of keen interest to enhance communication between road users. Numerous work on laser-based front end projection employing refractive and reflective optics has been reported so far, while for rear end illumination efforts are more scarce and a different optical design concept due to limited volumetric size and field of view regulations is required. Here, we report on a new and versatile approach for a laser-based rear end lighting system for automotive application which enables projection of information or signals to support other road users. The design is based on thin diffractive optical elements projecting the desired patterns upon illumination. Also, for protection of the road users from the steering laser beam, a diffusive back projection screen is designed to project information while fulfilling both the field of view and safety requirements. The projection system is based on a periodic diffusive structure made of an array of biconic lenses with sizes in the millimeter range. The field of view (FOV) from the simulated lens arrays complies with the angular requirements set by the Economic Commission for Europe (ECE). As a proof of concept, the diffusive screen is fabricated using microfabrication technology and characterized. In future, the screen will be combined with thin diffractive optical elements to realize an entire integrated projection system.

Fabrication of desired micro structures in polymers is always of keen interest for applications in illumination optics, sensors and optical interconnects. The challenge is to fabricate structures in the sub-micron range but at low cost. Among other fabrication methods as described in [1], maskless lithography tends to be cost effective and can create sub-micron structures.

Highly-functional photonic sensor networks integrated in thin polymer foils offer great potential for versatile applications in the life sciences, medicine, environmental analytics or production technology. For their realization, suitable low-cost and high-throughput production techniques need to be developed. Here, we describe work towards this goal, i.e. the fabrication of multimode polymer waveguides through a combination of thermal imprint and doctor blading. For imprint master stamp fabrication, a combined Bosch and O₂ plasma etching process in silicon is utilized. We also demonstrate stamp fabrication by an additive manufacturing method, i.e. by employing maskless UV lithography, to enhance the flexibility and cost-effectiveness of our approach. We, thus, realize various all-polymer waveguide arrays, beam splitters, and grating couplers which serve as basic elements to create more complex photonic circuits. We also demonstrate polymer based transmission lines comprising semiconductor as well as organic light sources and detectors. We discuss both the integration of semiconductor light sources and detectors such as verticalcavity surface-emitting lasers (VCSEL) and photo detectors as well as organic light emitting diodes (OLEDs) and organic photo detectors. In first applications, we combine these elements to create sensor arrays for measuring temperature, strain or refractive index. We show results of various sensor types utilizing different measurement principles implemented in laboratory environments so far. For example, a waveguide array containing a linear discontinuity which serves as elongation zone for displacement, strain or tilt measurement by detecting the intensity variation of the transmitted light propagating inside the structure is presented. In future, we plan to create more powerful sensor photonics networks for reliable and robust applications in real life, e.g. for point-of-care testing or production monitoring.

Summary form only given. With the advancement of illumination technology in automotive industry, significant amount of interest has arisen for laser based light sources for both front and rear end. While numerous amount of work has been done to incorporate laser based illumination for front lights [1], less attention has been paid towards rear and brake lights. Use of lasers as sources of illumination allows utilization of diffractive optical elements (DOEs) which are smaller in size and diffract the incident light at larger angles as compared to their counterpart refractive optical elements.We present a simple and cost effective method to design and fabricate DOEs onto polymers for projection of incident light in a predefined intensity distribution. The fabricated DOE, i.e., combination of several grating structures, each grating structure diffracting incident light to contribute in the desired pattern are computed in MATLAB with the help of diffraction theory and coupled wave analysis [2]. Once the DOE design is complete, it is transferred to the photoresist coated on a silicon substrate to prepare a stamp with the help of a maskless lithographic optical setup employing digital mirror device and spatial light modulators for two dimensional and three dimensional structures, respectively. After patterning the structures onto the photoresist, the DOEs are coated with PDMS (Polydimethylsiloxane) for preparation of soft stamps and then transferred to the polymer PMMA (Polymethylmethacrylat) using a hot embossing system.