Abstract: Aperiodic clock generation with clock spur suppression is based on cascaded randomizers, such as for mixed signal devices. A clock generator circuit includes an input node to receive the input periodic clock signal having an input-clock frequency. A first randomizer circuit coupled to receive the input clock signal from the input node, to perform signal randomization to suppress spurious signal content associated with (a) the input clock signal, and (b) the first randomizer circuit, and to generate an intermediate clock signal. A second concatenated randomizer circuit is coupled to receive the intermediate clock signal, to perform signal randomization to suppress spurious signal content associated with (a) the intermediated clock signal, and (b) the second randomizer circuit, and to generate an aperiodic output clock signal having a pre-defined average output-clock frequency that is less than the input-clock frequency. Example randomizers are a delta-sigma divider and a pulse swallower (in any order).

Abstract: Quasi-phase matched (QPM) second-harmonic (SH) generation in the reflection geometry is described. The SH intensity can be strongly enhanced by spatially modulating the optical properties of the nonlinear medium. This type of quasi-phase matching is demonstrated using an Al.sub.0.8 Ga.sub.0.2 As/GaAs heterostructure designed for .lambda.=1.06 .mu.m incident light. The SH light intensity generated in reflection from the heterostructure is enhanced 70 times relative to the SH response of a homogeneous GaAs wafer. A Fabry-Perot resonant cavity design employs this structure to make thin films with extremely high SH generation efficiencies. This is of particular interest used in vertical cavity surface emitting lasers (VCSELs).