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.
We developed a new generation of high-power laser modules for laser drying in battery electrode fabrication. Low power densities and homogeneous heating with full system efficiencies ⪆50% is within the record system efficiencies offered today. Moreover, simple scalability of the illumination profile and highly standardized fabrication techniques are the game changer benefits from using VCSELs as light source.
Advancements to our VCSEL technology platform now allow to dynamically switch between two orthogonal polarization states on a single VCSEL-array chip. Here stable and linearly polarized emission is combined without change to the VCSEL optical characteristics. This is rendered possible by 90°-rotated surface-gratings for each channel to realize polarization locking in one of the two polarization directions. Similar high polarization extinction ratios, thresholds and output powers are attained for each channel. Furthermore, electrical routing enables the flexible definition of illumination zones consisting of sub-arrays of VCSELs with the same polarization orientation. Time-division polarization multiplexing is thus enabled by addressing different zones of the VCSEL array for dynamic illumination concepts.
Flip-chip VCSELs with backside emission and lenses directly etched into the GaAs substrate are the most compact way to integrate optics with the VCSEL (ViBO = VCSEL with integrated Backside Optics). Beam shapes with lens structures enabling collimation as well as the uniform illumination of a defined field of view have been realized. Superior to separate optical elements the integrated optics avoids the need for individual alignment of laser die and optics and makes them an irremovable part of the chip. The realization of both contacts on the epitaxy side enables flip-chip assembly without the need for wire bonds, thus enabling ultra-short pulse operation. VCSELs are preferred for LiDAR applications due to their thermal stability and reliability. The required high brilliance can be achieved by micro-optics. Scaling the power into the kilowatt range requires stacked junctions and multi-chip concepts. This paper presents a new LiDAR system concept exploiting the potential of VCSELs with integrated optics.
Flip-chip VCSELs with backside emission revolutionize 3D sensing systems. Etching lenses directly into the GaAs substrate is the most compact way to integrate optics with the VCSEL. Various lens structures can be implemented enabling collimation as well as the uniform illumination of a defined field of view. Superior to separate optical elements the integrated optics avoids the need for individual alignment of laser die and optics and makes them an irremovable part of the chip, which is beneficial for long-term laser safety. The realization of both contacts on the epitaxy side enables flip-chip assembly without the need for wire bonds. This facilitates thermal management compared to top-emitting VCSELS and reduces system impedance. Individually addressable zones can be easily implemented, contacting is done via fine-pitch copper pillars. Backside emitting VCSELs can be designed for a large emission area thus enabling a very high active area of the array. This is especially useful for operating schemes with low duty-cycle enabling ultra-high pulse power output per chip area. VCSEL chips with integrated flood illumination optics for time-of-flight applications with narrow or broad field of view will be presented. Addressability of multiple zones on a chip can be implemented for enhanced illumination and sensing schemes. The ViBO technology platform allows for a wide variation of VCSEL chip properties and a significant miniaturization of illumination systems.
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