High-speed single-mode quantum dot and quantum well VCSELs

As the density of transistors in CMOS integrated circuits continues to roughly double each two years the processor computational power also roughly doubles. Since the number of input/output (I/O) devices can not increase without bound I/O speed must analogously approximately double each two years. In the Infiniband EDR standard (2011) a single channel bit rate of 26 Gb/s is foreseen. The maximum reliable and efficient copper link length shrinks at bit rates above 10 Gb/s to a few meters at best. At higher bit rates the length of a given multimode fiber link must also shrink, due to both modal and wavelength dispersions. Although the modal dispersion in modern multimode OM3 and OM4 fibers that are optimized for 850 nm vertical-cavity surface-emitting lasers (VCSELs) is reduced, the wavelength dispersion remains a serious issue for standard multimode VCSELs. An ultimate solution to overcome this problem is to apply single-mode VCSELs to extend and ultimately maximize the link length. In this paper we demonstrate recent results for single-mode VCSELs with very high relaxation resonance frequencies. Quantum well 850 nm VCSELs with record high 30 GHz resonance frequencies are demonstrated. Additionally single-mode data transmission at 35 Gb/s over multimode fiber is demonstrated. For comparison we also present specific device modeling parameters and performance characteristics of 850 nm single-mode quantum dot (QD) VCSELs. Despite a significant spectral broadening of the QD photoluminescence and gain due to QD size dispersion we obtain relaxation resonance frequencies as high as 17 GHz.