Scalable passively mode-locked semiconductor lasers for microprocessor clocking

摘要

The integration of photonic clocking in microprocessors is anticipated to occur during the 2008-2012 high-volume manufacturing (HVM) cycle. Though photonic clocking can be achieved through electronic modulation or actively mode-locking a laser, a more cost-effective and better solution would be to use internal cavity passively mode-locked semiconductor lasers. Not only do these lasers offer low-cost, simplicity, and ease of integration, but prototypes that are amenable to HVM are currently available. We present such a laser that is scalable by design to clock rates of 9 to hundreds of GHz and wavelengths in the 800 to 1100+ nm range. These lasers utilize internal saturable absorber(s) to passively mode-lock a semiconductor laser with relatively high peak powers. Experimental results from these lasers show an RF spectrum signal peak that is at least 40 dB above the noise floor with a -10 dB width of <1 MHz. The RMS jitter as determined by an oscilloscope with a precision timebase module was found to be ～1 ps which is among the best for this type of laser. Autocorrelation was used to confirm mode-locking and pulse width. In addition to experimental data, a theory and discussion on how the different characteristics of these lasers can be tailored for various commercial applications such as microprocessor clocking will be presented.