Rolf Goering

Colorless gradient-index cylindrical lenses with high numerical apertures produced by silver-ion exchange

Colorless gradient-index cylindrical lenses with high numerical apertures in slabs 200-1000 µm thick have been fabricated by silver-sodium ion exchange in a specially developed glass. The lenses with numerical apertures of 0.6 are characterized by index profiles and by spherical and chromatic aberration. On-axis focusing properties and the application to the collimation of high-power laser diode bars are discussed.

Micro-optical beam transformation system for high-power laser diode bars with efficient brightness conservation

Most of the potential applications of high power laser diode bars and stacks need special beam transformation systems in order to create a much more symmetric output beam. We present a novel concept for single emitted beam reconfiguration of high power laser diode bars, which uses different types of microoptical components. A very compact and efficient beam shaping system has been built upon the base of this concept, forming a nearly circular output beam with minimum brightness reduction compared to the laser diode output radiation.

Potential of transmittive micro-optical systems for miniaturized scanners, modulators, and switches

The utilization of micro-optical components in systems for optical beam deflection and modulation offers the possibility for realization switches and scanners. As the required displacement of the micro-optical components for efficient beam manipulation is quite small, high speed actuators with small electrical power consumption can be used. We present a variety of micro-optical configurations and discuss their potential for the creation of different types of miniaturized scanners and switches. The combination of micro-optical components already available and semiclassical piezoelectric actuators leads to new types of switching and modulation systems for a very broad spectrum of applications.

Integration process optimization of a micro-optical 1xN fiber optic switch

A novel concept has been developed for a fiber optic switch. It is based on miniaturized prisms deflecting the nearly collimated beam from the input fiber. These prisms are moved by the use of piezoelectric bending actuators. The deflected beam is directed to the output fiber, there is one prism for each output fiber. Coupling of the deflected light beam into the output fibers is achieved by microlenses. In order to simplify the integration process regular arrays of both the output fibers and the coupling microlenses have been used. A special technique and setup has been developed for fast and accurate adjustment of the lens array with respect to the fiber array. Both arrays are subsequently fixe to each other by gluing. The second critical integration process is the mounting procedure of the prisms to the bending actuators. For this purpose a special vacuum gripper has been built. With the help of this gripper all microprism can be mounted in one step. Using the developed integration processes, fiber switch prototypes have been built up with excellent optical parameters.

Miniaturized piezoelectrically driven fiber optic switches with transmittive micro-optics

We have developed different concepts of fiber optic switches based on hybrid transmittive micro-optical system, where switching is achieved by piezoelectrical movement of one of the micro-optical components. The input fiber beam is either collimated and deflected by a piezoelectrically driven short focal length microlens or refocussed onto a microprism structure, which is also piezoelectrically driven and deflects the beam in a number of discrete directions. In all of our configurations after deflection the beam is redirected and coupled into one of N output fibers by the use of a microlens array. The output fibers are also arranged in regular array. The switch configuration with continuous deflection is ideally suited for a large number of output channels, however, the problem still unsolved is to achieve high output channel stability and reproducibility. At the opposite, the discrete beam deflection approach ensures high stability and reproducibility by the optical arrangement and does not require position sensing for the actuators. The latter concept, of course requires special microprism elements, which are not available commercially. They have been fabricated with sufficient high quality by gray-tone lithography. For both concepts switch prototypes have been built up, yielding excellent optical parameters with respect to insertion loss and cross-talk. Typical switching times of 1 ms have been achieved. Special experimental setups have been built up for system integration.

Micro-optical modulators and switches for multimode fiber applications

External modulators and switches for multimode fiber transmission systems are required for aplenty of applications in optical metrology and communication systems. We show that a confocal arrangement of microlens arrays with certain filter elements in the common focal plane of the arrays, which are moved with the help of piezoelectrical actuators, is a very simple and flexible concept to meet the needs of a number of very different applications. The focal length, lens pitch and width of the arrays have to be chosen properly. We discuss which optical elements are required for certain applications. We present experiments for an intensity modulator.

Miniaturized optical systems for beam deflection and modulation

A new configuration of three micro-optical elements has been proposed for the realization of miniaturized optical beam deflection and modulation modules: One element with a special surface corrugation profile is placed in the focal plane of two microlenses or microlens arrays, one for focussing the incoming beam(s) and the second for output beam collimation. When the middle element is moved in lateral direction with respect to the optical axis, the parameters of the optical beam(s) is/are influenced depending on the real micro-optic structure. The results of first experiments on optical beam deflection and phase modulation are demonstrated.

Multichannel fiber optic switches based on MOEM systems

Fiber-optic switches become more and more appealing components not only in the field of optical communication, but also in measurements systems, sensors and data storage. We have developed a number of concepts for fiber-optic switches, all based on different types of special micro-optical components, actuated by miniaturized mechanical systems, primarily piezoelectric actuators. We present micro-optical configurations and discuss their potential for the creation of different-types of miniaturized switches. Keywords: micro-optics, micro-optical switches, piezoelectric actuators

Miniaturized fiber optic switches for optical metrology and optical communication

The utilization of micro-optical components in systems for optical beam deflection and modulation offers the possibility for realization of miniaturized switches and scanners. As the required displacement of the micro-optical components for efficient beam manipulation is quite small, high speed actuators with small electrical power consumption can be used. We present micro-optical configurations and discuss their potential for the creation of different types of miniaturized switches. The combination of micro-optical components already available and semiclassical piezoelectric actuators leads to new types of switching and modulation systems for a very broad spectrum of applications.

Miniaturized optical switches based on piezoelectrically driven microprism arrays

Using the principle of focussing an incoming beam onto a plane with special optical microstructures, novel miniaturized switching elements can be built up for different applications. As switching is achieved by a lateral movement of the microstructures, only small displacements (about 10 micrometers ) are sufficient for efficient beam manipulation. In this paper, we present the results of both theoretical and experimental investigations on a concept of multichannel beam deflection by microprisms located in the focal plane of an incoming beam. This concept is suitable for singlemode fiber switches. It is shown that nearly aberration free operation can be achieved by choosing the right substrate thickness and the axial focal position with respect to the microprisms for the cases of placing them on the front or rear substrate surface. A trade-off must be made between the numerical aperture of the focussed beam, the prism angles and the number of output channels of the deflecting element in order to achieve sufficient angular separation of the deflected beams. Two different techniques have been tested for microprism fabrication: wet anisotropic etching in silicon and a new method of mask projection onto scanned photoresist layers. Microprisms with sufficient optical quality have been fabricated with both methods. In experimental investigations, we showed that for a singlemode fiber 1 X 9-switch low insertion loss (< 1 dB) and low cross-talk between the output channels (-50 dB) can be obtained.