High-speed oxide confined 850-nm VCSELs operating error-free at 47 Gbit/s at room temperature and 40 Gbit/s at 85°C

Abstract

Summary form only given. Optical links based on multimode fiber and 850 nm VCSELs are critical elements in high performance computing systems, datacenters, and other short reach datacom networks. These applications are driving the demand for high bandwidth and it is anticipated that serial bit-rates up to 40 Gbit/s will be required for the next generation standards. For minimized power consumption, footprint, and cost, these high-speed links must function without active temperature control or cooling, and are consequently required to operate error-free (defined as a BER -12 ) not only at room temperature (RT), but also under high temperature conditions. Here, we present results from our latest generation of high-speed VCSELs. The epitaxial material was grown by MOCVD at IQE Europe and is a further development of the VCSEL structure with a number of design improvements. The DBR grading and doping schemes have been optimized for low resistance and low free carrier absorption. These improvements are of benefit for both static and dynamic characteristics as they allow for reaching a higher photon density before thermal rollover sets in, thereby enabling a higher output power and modulation bandwidth. A 0.5-λ cavity is used for improved carrier transport and longitudinal optical confinement (the previous design utilized a 1.5-λ cavity), properties that both are critical for high-speed characteristics. We recently presented results using this VCSEL design where we were able to demonstrate a record high modulation bandwidth of 28 GHz for a 4 μm aperture VCSEL, and error-free data transmission at up to 44 Gbit/s using a 7 μm aperture device. Here, we take advantage of an improved photoreceiver to extend the results to higher bit-rates and temperatures (85°C).