A high-contrast preamplifier based on optical-parametric amplification with a short pump pulse is demonstrated. A gain larger than 10(5) and measurement-limited contrast higher than 10(11) are obtained over a large temporal range extending within less than 10 ps of the peak of the pulse, because of the high instantaneous parametric gain provided by a short pump pulse in a nonlinear crystal. The energy gain and high contrast of this preamplifier make it a good seed source for high-power laser systems.

The operation of a single-shot cross-correlator based on a pulse replicator is described. The correlator uses a discrete sequence of sampling pulses that are nonlinearly mixed with the pulse under test. The combination of a high reflector and partial reflector replicates an optical pulse by multiple internal reflections and generates a sequence of spatially displaced and temporally delayed sampling pulses. This principle is used in a cross-correlator characterizing optical pulses at 1053 nm. A dynamic range higher than 60 dB is obtained over a temporal range larger than 200 ps.

The influence of parasitic processes on the performance of ultra-broadband noncollinear optical parametric amplifiers (NOPA's) is investigated for walk-off and non-walk-off compensating configurations. Experimental results with a white-light-seeded NOPA agree well with numerical simulations. The same model shows that 10% of the output energy of an amplified signal can be transferred into a parasitic second harmonic of the signal. These findings are supported by quantitative measurements on a few-cycle NOPA, where a few percent of the signal energy is converted to its second harmonic in the walk-off compensating case. This effect is reduced by an order of magnitude in the non-walk-off compensating configuration. A detailed study of the phase-matching conditions of the most common nonlinear crystals provides guidelines for designing NOPA systems.

Abstract-A new circuit technique, the distributed waveform generator (DWG), is proposed for low-power ultra-wideband pulse generation, shaping and modulation. It time-interleaves multiple impulse generators, and uses distributed circuit techniques to combine generated wideband impulses. Built-in pulse shaping can be realized by programming the delay and amplitude of each impulse similar to an FIR filter. Pulse modulation schemes such as on-off keying (OOK) and pulse position modulation (PPM) can be easily applied in this architecture. Two DWG circuit prototypes were implemented in a standard 0.18 m digital CMOS technology to demonstrate its advantages. A 10-tap, 10 GSample/s, single-polarity DWG prototype achieves a pulse rate of 1 GHz while consuming 50 mW, and demonstrates OOK modulation using 16 Mb/s PRBS data. A 10-tap, 10 GSample/s, dual-polarity DWG prototype was developed to generate UWB pulses compliant with the transmit power emission mask. Based on the latter DWG design, a reconfigurable impulse radio UWB (IR-UWB) transmitter prototype was implemented. The transmitter's pulse rate can be varied from 16 MHz range up to 2.5 GHz. The bandwidth of generated UWB pulses is also variable, and was measured up to 6 GHz ( 10 dB bandwidth). Both OOK and PPM modulation schemes are successfully demonstrated using 32 Mb/s PRBS data. The IR-UWB transmitter achieves a measured energy efficiency of 45 pJ/pulse, independent of pulse rate.