Peter Giesen

Design guidelines for thermal stability in optomechanical instruments

Opto-mechanical instruments are sensitive to temperature effects. The optical performance will be influenced by temperature variations within an instrument. Temperature variations can occur due to environmental or internal heat sources. Assembly at a different temperature than eventual operation of the instrument can also influence the performance. This paper describes principles to minimize thermal disturbance of optical performance. The thermal behaviour of a system can area-wise be divided in heat source, heat transfer area and place where the optical performance is affected. Placement of the heat source is critical. Using a large thermal capacity, the influence of the source will be minimized. Heat transfer can be controlled by insulation or by good conduction, the latter minimizing the thermal gradient along the thermal path. Thermo mechanical effects on the optical performance can be controlled using a thermal centre, a combination of materials with different expansion properties, low thermal expansion materials and scaling effects of the optical design. TNO TPD designs and manufactures opto-mechanical instruments for space and astronomy. The design guidelines described are commonly used in these instruments. Several examples of the application of these design guidelines are presented in this paper.

Polymer substrates for flexible electronics: achievements and challenges

Flexible electronics technology can potentially result in many compelling applications not satisfied by the rigid Si-based conventional electronics. Commercially available foils such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) have emerged as the most suitable polymer materials for wide range of flexible electronics applications. Despite the enormous progress which has been recently done on the optimization of physical and mechanical properties of PET and PEN foils, their dimensional stability at the micro-scale is still an issue during patterning of wiring by means of lithography. Consequently, the measurement of in-plane micro-deformation of foil is of great importance for understanding and predicting its thermal, hydroscopic and mechanical behaviour during processing.

Delft testbed interferometer: layout design and research goals

The Delft Testbed Interferometer (DTI) will be presented. The main purpose for the DTI is to demonstrate the feasibility of homothetic mapping, both fixed and under scanning conditions. The driving design issues behind the DTI will be presented together with a list of experiments to be conducted with the DTI system in the field of wide field imaging.

Submicron patterning on flexible substrates by reduction optical lithography

In this paper we report the use of projection optical lithography to pattern micron-sized features on 100 μm thick PEN foils. A foil-on-carrier lamination process was developed to ensure a good dimensional stability during the lithographic processing and imaging of the foil. A stepper based leveling metrology was used in characterizing the surface flatness of the foil-on-carriers. A lithography process was developed to image micron and submicron patterns on foil substrates. The process window for 1-10 μm features was determined from focus and exposure energy experiments. The lithographic study indicated a reproducible and excellent imaging accuracy for patterning micron-sized features on flexible substrates. This makes the technology very suitable for the manufacturing of electronic devices with critical dimensions in the micron and submicron range. In addition, we made transistors-on-foil demonstrators with the developed foil-on-carrier lamination and imaging technology.

Advances in maskless and mask-based optical lithography on plastic flexible substrates

Organic flexible electronics is an emerging technology with huge potential growth in the future which is likely to open up a complete new series of potential applications such as flexible OLED-based displays, urban commercial signage, and flexible electronic paper. The transistor is the fundamental building block of all these applications. A key challenge in patterning transistors on flexible plastic substrates stems from the in-plane nonlinear deformations as a consequence of foil expansion/shrinkage, moisture uptake, baking etc. during various processing steps. Optical maskless lithography is one of the potential candidates for compensating for these foil distortions by in-situ adjustment prior to exposure of the new layer image with respect to the already patterned layers. Maskless lithography also brings the added value of reducing the cost-of-ownership related to traditional mask-based tools by eliminating the need for expensive masks. For the purpose of this paper, single-layer maskless exposures at 355 nm were performed on gold-coated poly(ethylenenaphthalate) (PEN) flexible substrates temporarily attached to rigid carriers to ensure dimensional stability during processing. Two positive photoresists were employed for this study and the results on plastic foils were benchmarked against maskless as well as mask-based (ASML PAS 5500/100D stepper) exposures on silicon wafers.

Delft Testbed Interferometer: a homothetic mapping test setup

The Delft Testbed Interferometer (DTI) will be presented. The basics of homothetic mapping will be explained together with the method of fulfilling the requirements as chosen in the DTI setup. The optical layout incorporates a novel tracking concept enabling the use of homothetic mapping in real telescope systems for observations on the sky. The requirements for homothetic mapping and the choices made in the DTI setup will be discussed. Finally the planned experiments will be discussed.

Mechanical setup for optical aperture synthesis for wide field imaging

Homothetic mapping is a technique that combines the images from several telescopes so that it looks like as though they came form a single large telescope. This technique enables a much wider interferometric field of image than current techniques can provide. To investigate the feasibility, a research testbed is build know as Delft Testbed interferometer (DTI). DTI simulates a configuration of three telescopes collecting light of a set of 3 stars. The stars are simulated by coupling light of a Xenon light source into three fibres, which illuminate a parabolic mirror. The light that is used has wavelengths of 500 nm - 800 nm. The light of the three telescopes will be combined in such a way that the beam arrangement in the pupil plane corresponds with the telescope arrangement and the Optical Path Difference (OPD) is minimized for the three beams. To achieve white light fringes with high visibility, the mechanical testbed that is 2 m x 1 m x 0.5 m in size, requires stable mounting of components. This paper describes the mounting of the diamond turned off-axis parabolic mirrors of 200 mm in diameter and 240 mm flat mirrors; furthermore, it describes components like the telescopes and the active controllable components for repositioning of the beam arrangement. Mechanisms were developed for alignment of piezo actuators and for delay lines. The delay lines can also be used to compensate pupil rotation. Test results demonstrate that the test setup is highly stable for temperature as well as for airflow, although the system is placed in a non-thermally controlled lab. This allows measurements of nm, in presence of μm disturbances.