upper limit of the laser pulse frequency is determined by the delay through the internal feedback loop i 1 i 2 b 1 a 1 the frequency of the trig signal is the same as the pulse frequency of the pulsed laser it is advantageous that the jitter of the pulsed laser be in the order of about less than about 2 femto seconds or less allowing portions of conventional electrical clock distribution trees to be replaced by optical counterparts in one example delay circuit b 1 is implemented as a fixed delay in one example delay circuit b 1 is a programmable delay the advantage of a programmable delay is that the clock shape the ratio between clock high and clock low time durations in each clock cycle often this ratio is 1 as illustrated in fig2 may be tuned delay circuit b 1 may be implemented for example as wire delay e g longer then required wire lengths electrically programmable fuses e fuses a serial latch chain multiplexer selectable latch chains and even number serial buffer chains e fuses and latch chains depending on how they are multiplexed are examples of delay circuits in which the delay may be programmed after fabrication of circuit 100 see fig1 in order to avoid noise on adjacent circuits causing jitter on circuit 100 it is advantageous that circuit 100 be shielded as shown by the dashed line in fig1 examples of shielding include but is not limited to locating circuit 100 device structures away from structures of adjacent circuits avoiding running wires of circuit 100 parallel to wires of adjacent circuits using shielded wires in circuit 100 see fig5 using a dedicated power supply for circuit 100.