Fluorescence detectors are applied for various applications in biomedical research, e.g. for pH-sensoring or single-cell
detection. Free space optical systems offer the advantage of compact and efficiently integrated systems with benefits in
the terms of systems alignment and optical functionality. On the other hand, due to the lab-on-a-chip character many
fluidic systems, such as segmented flow systems, are very compact and thus compatible with integrated optical systems.
We discuss the potential of the integration of the segmented flow approach in complex free space optical microsystems.
The design and realization of a highly integrated fluorescence detector is demonstrated. The system is fabricated by ultra
precision micromilling which allows one to monolithically integrate freeform optical elements for optimized optical
Planar microoptical systems integration is a powerful approach for the fabrication of optical systems and has been
demonstrated for a large variety of applications. The folded optical axis in combination with planar fabrication
technologies enables highly integrated and rugged optical systems. In this geometry, however, specific care is necessary
to avoid aberrations resulting from the oblique optical axis. A purely diffractive implementation of these systems
generally leads to an efficiency of only a few percent. Combining classical refractive optics with diffractive correction
elements increases the overall efficiency. However, the purely refractive implementation suffered from the lack of
fabrication technologies for freeform microoptical elements. We present the results of the first fabrication of freeform
refractive correction elements combined with standard off-the-shelf refractive microlenses to form a completely
refractive planar integrated optical system using ultraprecision micromilling. Experiments confirm the increased optical
performance of the systems by integrating two micromachined reflective correction elements. Both elements have a size
of 2.4 x 2.4 mm2 with a peak-to-valley surface profile depth of 2.6 μm. They are fabricated with an average roughness
height < 40 nm and a surface tolerance < 400 nm.
Conventional microlens arrays consist of a repetitive arrangement of a unit cell on a fixed pitch. In a chirped array, the inflexibility of a regular structure has been overcome. Here, the array consists of individually shaped lenses which are defined by a parametric description of the cells optical function. We propose different fabrication methods for chirped microlens arrays and present experimentally obtained data. Reflow of photoresist is an established technology for the fabrication of microlenses with superior optical performance. For the generation of a chirped microlens array the photolithographic mask for patterning the resist to be melted has to be chirped. We present an algorithm for mask generation with an example of an ultra-thin camera objective. Inherent to the reflow process stringent limitations to viable surfaces apply. For achieving more arbitrary surfaces, laser lithography and also 2-photon polymerization are employed. In both methods the structures are decomposed into pixels. In laser lithography the local height is converted into an intensity value for the exposure. This variable dose writing locally changes the solubility of the resist in the development process leading to the required surface profile. We propose a writing scheme enabling structure heights of several ten microns with sufficient height discretization. 2-photon polymerization is a rapid prototyping method. Here, a small volume of a UV-curing organic-inorganic co-polymer is hardened in the tight focus of the writing beam. The volume pixel to be exposed is addressed by piezoelectric translation stages. Experimentally obtained structures and performed tests of the optical quality are presented.
Planar integrated microoptical systems have been demonstrated for a variety of applications such as optical interconnects, sensing and security applications. Diffractive optical elements provide the necessary design freedom to optimize the optical performance of such systems along the folded optical axis. For enhanced optical efficiency it is necessary to combine diffractive and refractive elements within such systems. Hereby the refractive components provide most of the optical power while the diffractive elements are used as correction elements for optimized system performance. The integration of refractive components has significant consequences on the geometry of planar integrated optical systems as well as on the optical systems design. Based on this approach we present various designs for efficient planar-optical (phase-contrast) imaging systems. We compare various possibilities for the simulation of diffractive and holographic optical components and their integration in the design of planar microoptical systems. To this end we apply commercial design software (e.g. ZemaxTM, ASAPTM) as well as self programmed tools.