VCSELs for Optical Mice and Sensing

Abstract

A real mass application for VCSELs is their use in optical mice and sensing. As illumination source for sensing applications VCSELs offer a better performance than LEDs. The even more advanced approach of laser self-mixing interference sensors allows a next step in integration, accuracy and new application fields. This chapter summarizes the major requirements towards VCSELs in illumination for sensing applications and gives typical specifications. A detailed description of the production process and the achieved reproducibility makes clear that these VCSELs are ideally suited for production in large quantities. In the second half of the chapter the self-mixing interference method is described in more detail and a highly integrated two axes laser Doppler interferometer is shown. This product is designed for a laser mouse but offers a number of other sensing applications.

Review on Single-Mode Vertical-Cavity Surface-Emitting Lasers for High-Speed Data Transfer

“…In terms of digital modulation, time-dependent rate equations (8,9) must be solved including lateral variations of Fig. 7.…”

“…Such devices do not suffer from light-current-voltage curve fractures as much as semiconductor lasers that switch to higher-order modes with a change in the pump current. The first commercial use of SM VCSELs was a computer mouse light source to increase tracking accuracy, due to the small beam divergence and symmetrical radiation pattern, and to reduce electricity consumption, compared to a LED based computer mouse [9]. Another application of SM VCSELs was atomic clocks for cesium and rubidium atoms [10].…”

Vertical-cavity surface-emitting laser technology applications with focus on sensors and three-dimensional imaging

“…Smart sensors have been another important early mass market for VCSELs with several tens of millions shipped pieces per year. Prominent applications include fingertip navigation, industrial displacement sensing, and laser computer mice, 7) where the latter significantly advanced early mass production of VCSELs. The sensors often require single-mode 20,21) and single-polarization emission.…”

“…Single-mode single-polarization VCSEL for sensor technologies Figure 5 indicates displacement sensing using self-mixing of laser light 27) in the rather compact Philips TwinEye sensor. 7,28) Key element of the sensor is a single-mode singlepolarization VCSEL with monolithically integrated photodiode. Light backscattered into the VCSEL from moving objects experiences a Doppler shift and generates difference frequency photodiode signals that are used to measure velocity.…”

“…Circular beam characteristics are nicely compatible with micro-optics and optical fiber technologies. VCSELs with emission wavelengths ranging from UV to blue, green, red, near-, and mid-infrared have been developed 3) for a variety of applications 4) in optical datacom, 5,6) sensing, 7) and imaging. From a commercial point of view, high-performance oxide-confined InAlGaAs VCSELs with emission wavelengths between 750 and 1200 nm certainly dominate the market.…”