We successfully transmitted a 40 Gbit/s PAM4 signal over 300 m at 980 nm using a two-mode VCSEL and standard single-mode fiber, exhibiting bi-modal behavior and high modal bandwidth at this wavelength.

VCSEL-based optical transceivers in data centers meet the increase in data traffic by increasing the data transmission rate. A single-channel PAM-4 data rate of >100 Gb/s is already in high demand. For 100Gb/s operation a low relative intensity noise (RIN) significantly gains importance. The challenge is to reduce the RIN without impeding the other static and dynamic VCSEL performance parameters. We demonstrate up to 20 dB/Hz RIN reduction of commercial VCSELs that are approaching the shot noise limit and give an outlook on datacom VCSELs for higher order modulation formats for single channel data rates of 100 Gb/s and beyond.

Transmission of 56-Gbps signals across a 500-meter 980 nm optimized multimode fiber with 14.2 GHz·km bandwidth using 980 nm multimode VCSEL is demonstrated. The results show promising performance within IEEE standards for short reach applications.

ViP stands for a VCSEL with integrated photodiode. It features a photodiode embedded in the VCSEL resonator. A single intra-cavity contact serves as VCSEL cathode as well as photodiode anode. The VCSEL is single-mode and a sub-wavelength grating on the output facet is used to stabilize the polarization of the emitted light. The ultra-compact chip has two separately addressable mesas. In addition, good production capability and reliability make the device ideal for mass products. Exploiting the principle of self-mixing interference (SMI), the ViP can be used in systems precisely measuring e.g., velocity, distance, quantitative particle concentration as a measure for air quality or fast eye-movements. The interferometric precision of velocity measurements enables demanding industrial applications like a new contactless encoder with high accuracy. ViP and the SMI principle make the detection almost insensitive for environmental background light. The functionality of the sensor has been demonstrated in bright sunlight and measuring speed over ground up to 250km/h in automotive applications. Low latency is ideal for the detection of fast eye movements. The miniature sensor fits into the frame of an AR/VR goggle and can detect eye-gestures. An ultra-compact air quality detector measuring PM2.5 as well as ultra-fine particles is described as well. The system does not require any enforced air flow nor openings in the body thus could be embedded in wearable consumer devices. With a size of a match head, it enables a precise, real-time, and personalized measurement.

The integration of gaze gesture sensors in next-generation smart glasses will improve usability and enable new interaction concepts. However, consumer smart glasses place additional requirements to gaze gesture sensors, such as a low power consumption, high integration capability and robustness to ambient illumination. We propose a novel gaze gesture sensor based on laser feedback interferometry (LFI), which is capable to measure the rotational velocity of the eye as well as the sensor’s distance towards the eye. This sensor delivers a unique and novel set of features with an outstanding sample rate allowing to not only predict a gaze gesture but also to anticipate it. To take full advantage of the unique sensor features and the high sampling rate, we propose a novel gaze symbol classification algorithm based on single sample. At a mean F1-score of 93.44 %, our algorithms shows exceptional classification performance.

The integration of gaze gesture sensors in next-generation smart glasses will improve usability and enable new interaction concepts. However, consumer smart glasses place additional requirements to gaze gesture sensors, such as a low power consumption, high integration capability and robustness to ambient illumination. We propose a novel gaze gesture sensor based on laser feedback interferometry (LFI), which is capable to measure the rotational velocity of the eye as well as the sensors distance towards the eye. This sensor delivers a unique and novel set of features with an outstanding sample rate allowing to not only predict a gaze gesture but also to anticipate it. To take full advantage of the unique sensor features and the high sampling rate, we propose additionally a novel gaze gesture classification algorithm based on single sample. At a mean F1-score of 93.44 performance at a negative latency between gaze gesture input and command execution.

The integration of eye-tracking sensors in next-generation AR glasses will increase usability and enable new interaction concepts. Consumer AR glasses emphasize however additional requirements to eye-tracking sensors, such as high integratability and robustness to ambient illumination. We propose a novel eye-tracking sensor based on the self-mixing interference (SMI) effect of lasers. In consequence, our sensor as small as a grain of sand shows exceptional robustness against ambient radiation compared to conventional camera-based eye trackers. In this paper, we evaluate ambient light robustness under different illumination conditions for video-based oculography, conventional scanned laser eye tracking as well as the SMI-based sensor.

VCSEL based sensors can measure distance and velocity in three dimensional space and are already produced in high quantities for professional and consumer applications. Several physical principles are used: VCSELs are applied as infrared illumination for surveillance cameras. High power arrays combined with imaging optics provide a uniform illumination of scenes up to a distance of several hundred meters. Time-of-flight methods use a pulsed VCSEL as light source, either with strong single pulses at low duty cycle or with pulse trains. Because of the sensitivity to background light and the strong decrease of the signal with distance several Watts of laser power are needed at a distance of up to 100m. VCSEL arrays enable power scaling and can provide very short pulses at higher power density. Applications range from extended functions in a smartphone over industrial sensors up to automotive LIDAR for driver assistance and autonomous driving. Self-mixing interference works with coherent laser photons scattered back into the cavity. It is therefore insensitive to environmental light. The method is used to measure target velocity and distance with very high accuracy at distances up to one meter. Single-mode VCSELs with integrated photodiode and grating stabilized polarization enable very compact and cost effective products. Besides the well know application as computer input device new applications with even higher accuracy or for speed over ground measurement in automobiles and up to 250km/h are investigated. All measurement methods exploit the known VCSEL properties like robustness, stability over temperature and the potential for packages with integrated optics and electronics. This makes VCSEL sensors ideally suited for new mass applications in consumer and automotive markets.

AbstractAktive Infrarot (IR)‐Beleuchtung wird in Kamerasystemen zur besseren Identifizierung von Zeichen, Objekten und Personen eingesetzt. IR‐Beleuchtung ermöglicht Aufnahmen mit hoher Geschwindigkeit oder von schnell bewegten Objekten (z. B. Lesen von Kfz‐Kennzeichen an fahrenden Fahrzeugen). Sie kann zudem Schatten und die Variabilität des Umgebungslichts reduzieren oder eliminieren. Gegenüber sichtbarem Licht verbessert IR‐Beleuchtung die Sichtbarkeit bei schwierigen Witterungsverhältnissen wie Nebel, Regen und Schneefall (Abb. 1). Eine passende aktive Lichtquelle erweitert den Einsatzbereich fast aller Kameraanwendungen.

There are many applications for non-contact measurement of the displacement and velocity of moving objects, especially when achieved at low cost. An optical displacement sensor has been developed that can be compared to expensive laser-interferometry sensors, however at a cost compatible with requirements for consumer products. This miniature Laser-Doppler Interferometer works on all light scattering surfaces. The first large-scale application is in PC-mice. The measurement principle employs so-called "Laser Self Mixing", which occurs when laser light scattered on a surface, within the coherence length, is coupled back into the laser cavity. When the object is moving, the back-scattered light is continuously shifting in phase relative to the laser light at the laser mirror. This results in a periodic perturbation of the feedback into the laser cavity, which causes modulations of the light intensity in the cavity. The frequency of these modulations is proportional the speed of the object. A VCSEL, optimized for this application, is used as light source, a photo-diode in the sensor measures the intensity fluctuations and, finally, an integrated circuit transfers the photo-diode signal into velocity or displacement information. To determine the direction of the movement, a triangle modulation of the laser-current is used, which modulates the laser-temperature and hence the laser frequency. Next to the applications in PC-mice a much wider range of applications as input device in consumer products can be envisaged. For instance menu navigation by finger movement over a sensor in remote controls, mobile phones and lap tops. Furthermore a wide field of applications is envisaged in the manufacturing of industrial equipment, which requires non-contact measurement of the movement of materials. The small form factor of less than 0.2 cubic centimeters allows applications previously considered impossible.

A dual-layer disc is developed for blue-laser phase-change recording. The two recording stacks are based on fast-growth phase-change materials (FGMs). Both layers show good recording performance at a total disc capacity of 46.6 GB and with a slightly high jitter at 50 GB. The thicknesses of both the cover and spacer layers are controlled such that the deviations from the reference thicknesses of both recording layers are less than 2 µm. This eliminates the need for dynamical spherical aberration correction in the drive. The absolute difference in transmission between the written and unwritten states of the upper layer is only 2%. It is shown that this transmission difference causes no problem for readout and writing of the lower layer.