Pulsed mode red VCSEL for high speed VLC communication

VCSELs (Vertical-cavity surface-emitting lasers) offer a number of unique advantages: a threshold current that is low and stable with temperature so that electricity is converted to light with a very high efficiency; the ability to be modulated at very high frequencies; a circular output beam with low divergence, simplifying the optical system. Lifetime parameters are not degraded when overdriving its normal operating current in a low duty cycle application. The mentioned properties of VCSELs makes them excellent for usage in high speed free space optical links. However till the end of the last decade 850 nm VCSEL dominated the high speed area. Because of the laser safety regulations, the power limits restricted the 850 nm VCSEL usage in free space optical links. The fabrication problems of visible light producing VCSEL has been solved recently, and high speed 650 nm (red) VCSELs are available on market. In this paper we will show how a pulsed mode laser driver can exploit the unique properties of VCSELs in low cost, low power and high speed visible light communication (VLC) links.