Berlin, Germany and Urbana, IL--VI Systems and the University of Illinois at Urbana-Champaign have demonstrated a novel single-mode photonic-crystal (PC) vertical-cavity surface-emitting laser (VCSEL) suitable for error-free 25 Gbit/s data transmission over a 1 km length of multimode optical fiber at very low received optical power. The laser was demoed at SPIE Photonics West 2013 (Feb. 2-7, 2013; San Francisco, CA).
Target applications are data transmission inside large data centers, supercomputer clusters, and racks of telecom equipment at ultrahigh-bit data rates.
The PC, fabricated as a pattern of microholes in the top layers of the VCSEL, leads to high modulation bandwidth at a low current density. The single-mode operation of the laser, which emits at an 850 nm wavelength, leads to a reduced chromatic dispersion, lengthening the transmission distance as confirmed by measurements at the Technical University of Berlin.
The device was manufactured from a VI Systems wafer, which was processed at the University of Illinois at Urbana-Champaign with a defined photolithographic pattern of holes in the top mirror.
The laser operates at a current density of 5.4 kA/cm2, enabling a -3 dB bandwidth of 18 GHz. Error-free optical data transmission at 25 Gbit/s over 1 km of OM4 multimode fiber was realized at a received power of 70 µW using a high-speed photoreceiver module from VI Systems.
