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Optical methods allow a particularly precise distance measurement in which the wavelength of the light itself is used as the basic distance scale. One elegant way of measuring distance is, for example, via the position-dependent intensity of a standing wave (standing wave interferometer).

Here, the CiS Research Institute has developed tandem diodes that significantly simplify the design of the well-known Michelson interferometer, a high-precision measurement method for determining the length and position of precision machines.

The scientists at the CiS Research Institute have succeeded in developing transparent detectors for this purpose, whose active layers are made of doped silicon or polysilicon. These transparent photodiodes absorb only a very small part of the incident light in extremely thin silicon layers. The unabsorbed part of the light passes through the detector and can be used for sensory applications.

In a double configuration (tandem), two such partially transparent diodes are stacked in a multi-layer chip with a high degree of spacing accuracy. This makes it possible to realize standing-wave interferometers with direct resolution of the direction of movement. The usual division into reference and sample beams via beam splitters becomes superfluous and the system can be realized much more simply and compactly.