Laser Diode Requirements And Limitations For VLSI Holographic Optical Interconnects

Abstract

Laser requirements and limitations for VLSI optical interconnect networks employing CGHs are discussed from a system point of view. For architectures with a collimating lens at the laser and a collector lens at the (on-chip) detector, the restrictions on laser wavelength stability are typically ± 10 A (thus requiring the laser's temperature to be regulated to approximately ± 5 - 10°C). Dif-fraction limitations are shown to restrict the density of interconnects to the 104 /cm2 range for many architectures (in particular, "space variant" architectures), rather than the 107 /cm2 to 108 /cm2 range frequently quoted for "space invariant" architectures. Archi-tectures with a mixture of space variance and invariance can lead to intermediate densities. Some architectures require low threshold, high efficiency lasers, whereas others require very high output power with much less concern for threshold and efficiency. A network with 3000 point-to-point interconnects/cm2, each transmitting at a 500 Mbit rate with a 10-11 Bit-Error-Rate is analyzed and the best system performance is obtained if very high power laser arrays (5 - 10 W) are available. Laser output pattern control is also con-sidered.