Position sensing using an integrated VCSEL and PIN photodetector microsystem

Compact, non-contact, and low operating power sensors are desirable for position sensing applications. Vertical-cavity surface-emitting lasers integrated monolithically with PIN photodetectors have been designed and fabricated for optical position sensing. This compound semiconductor component has in turn been integrated onto a Si-platform to form a microsystem. Using a metallic grating as a position gauge, the sensor microsystem can measure differences in reflected power from the grating as it travels parallel to the sensors. This measurement technique allows for a high spatial resolution. Calculations indicate that such a device can detect spatial changes on the order of the wavelength of light emitted from the laser. Measurements from the work described here show the potential to use VCSEL/PIN chips to determine position with an accuracy of sub-micron resolution.