Microoptics at the Unversity of Hagen

The group for Optical Information Technology at the Fernuniversität Hagen works in the field of microoptics. We pursue work in different areas: 1. a novel approach for the integration of microoptic systems ("planar-integrated free-space optics" or PIFSO), 2. the use of modified Fresnel zone plates for high-resolution imaging in the UV-range and 3. the implementation of optical temporal filters based on the self-imaging phenomenon.

 

Planar-integrated free-space optics

With the adaptation of microfabrication techniques from semiconductor processing it has become possible to make a variety of refractive and diffractive microoptical elements [1]. We use the microoptics technology to build miniaturized integrated free-space optical systems in a planar configuration [2]. In the "planar optics" approach optical elements such as microlenses and beamsplitters are integrated on one or both surfaces of a transparent substrate (Fig. 1). The folding the 3-D optics into a 2-D geometry allows one to process all the optics simultaneously by using standard planar batch fabrication techniques. The positioning of the microoptic elements is achieved with lithographic precision (sub-micron range). Mechanical assembly, as required in conventional optics, is largely eliminated. Light propagation takes place inside the substrate along a zigzag path. The substrate, which is typically several millimeters thick, serves both as a medium for light propagation as well as a board onto which other components can be mounted. Optoelectronic chips like arrays of vertical cavity surface emitting microlasers and detector arrays can be bonded onto the substrate by using hybrid integration techniques such as flip-chip bonding.

Figure 1: Schematic of an integrated planar optical imaging system. Light signals travel inside a thick transparent substrate. Chips are mounted to the substrate by solder bump bonding.

 

Planar-integrated free-space optics is a technology that lends itself to build miniaturized, robust optoelectronic microsystems. It can be applied to various areas such as optical interconnections for computer communications, sensor technology, and optical data storage. Several demonstration experiments are described in ref. [3].

In our work, we consider theoretical, experimental and technological aspects of planar optics and investigate potential applications. Ongoing projects deal with the packaging of planar optics, imaging in planar optical systems, optical clock distribution, and the use of planar optics for optical correlation, interconnections and sensor applications, see, for example [4-6].

For the fabrication of the microoptics, we use a class 100/10 clean room which is furnished with equipment for optical lithography and reactive ion etching. For the work on packaging of planar optics we have a flip-chip bonder and a thermal-anodic bonder available.

Keywords:

microoptics, diffractive optics, planar-integrated free-space optics, lithographic fabrication, hybrid integration, flip-chip bonding, optoelectronic packaging, optical interconnection, optical sensors.

 

References:

[1] S. Sinzinger and J. Jahns, "Microoptics" 2nd ed., Wiley-VCH, Weinheim, 2003.
[2] J. Jahns and A. Huang, Appl. Opt. 28 (1989) 1602-1605.
[3] J. Jahns, Proc. IEEE 82 (1994) 1623-1631.
[4] M. Testorf, J. Jahns, J. Opt. Soc. Am. A 16 (1999) 1175 - 1183.
[5] M. Gruber, J. Jahns, S. Sinzinger, Appl. Opt. 39 (2000) 5367-5373.
[6] M. Gruber, Appl. Opt. 43 (2004) 463-470.