Generation of high-repetition-rate WDM pulse trains from anarrayed-waveguide grating

We present what we believe to be the first demonstration of femtosecond pulse train generation from an arrayed-waveguide grating. Terahertz-rate bursts of femtosecond pulses are produced with the rate determined by the arrayed-waveguide delay spacing     

Femtosecond direct space-to-time pulse shaping

The direct space-to-time (DST) pulse shaping apparatus is investigated both theoretically and experimentally. The discussion shows how the operation of the DST pulse shaper may be understood in terms of the femtosecond response of a generalized spectrometer. A complete discussion of the advantages and tradeoffs of utilizing this pulse-shaping configuration is given, including the direct scaling between the masking function and the output temporal intensity profile, system efficiency, spectral resolution, and temporal window, compensation/cancellation of chirp, and generation of multiple output waveforms     

Fast Characterization of Dispersion and Dispersion Slope of Optical Fiber Links Using Spectral Interferometry With Frequency Combs

We demonstrate fast characterization ( $sim$1.4 $mu hbox{s}$) of both the dispersion and dispersion slope of long optical fiber links ( $sim$25 km) using dual quadrature spectral interferometry with an optical frequency comb. Compared to previous spectral interferometry experiments limited to fiber lengths of meters, the long coherence length and the periodic delay properties of frequency combs, coupled with fast data acquisition, enable spectral interferometric characterization of fibers longer by several orders of magnitude. We expect that our method will be useful to recently proposed lightwave techniques like coherent wavelength-division multiplexing and to coherent modulation formats by providing a real-time monitoring capability for the link dispersion. Another area of application would be in stabilization of systems which perform frequency and timing distribution over long fiber links using stabilized optical frequency combs.      

Programmable shaping of femtosecond optical pulses by use of128-element liquid crystal phase modulator

Programmable shaping of femtosecond pulses by using a 128-element liquid crystal modulator to manipulate the phases of optical frequency components which are spatially dispersed within a grating-and-lens pulse shaping apparatus is described. This apparatus makes possible gray-level control of the spectral phases and allows modification of the pulse shape on a millisecond time scale under electronic control. Refinements in the design of the multielement modulator result in pulse shaping fidelity comparable to that which can be achieved with microlithographically fabricated masks. Several examples of pulse shaping operation, including pulse position modulation, programmable pulse compression, and adjustable cubic phase distortion, are described     

Optical arbitrary waveform generation and characterization using spectral line-by-line control

This paper demonstrates optical arbitrary waveform generation (O-AWG) and its characterization using spectral line-by-line control with high-resolution grating-based pulse shapers. Such integrated capabilities are the enabling techniques for high-fidelity O-AWG.     

Synthesis of Millimeter-Wave Power Spectra Using Time-Multiplexed Optical Pulse Shaping

Millimeter-wave (MMW) electrical power spectra are flexibly synthesized by integrating fast wavelength switching, optical frequency comb generation, spectral line-by-line pulse shaping, and optical-to-electrical conversion. Control over generated RF power spectra is exercised through the choice both of the optical parent waveforms and of the wavelength switching patterns. Discrete or comb-like MMW power spectra are generated using periodic wavelength switching, while nearly continuous MMW spectra can be obtained when wavelengths are switched according to a pseudorandom bit stream.     

Femtosecond optical packet generation by a direct space-to-time pulse shaper

We demonstrate femtosecond operation of a direct space-to-time pulse shaper in which there is direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. We use this apparatus to generate trains of 20 pulses as an ultrafast optical data packet over an ~40-ps temporal window.     

High-efficiency blue generation by frequency doubling of femtosecond pulses in a thick nonlinear crystal

We have demonstrated highly efficient frequency doubling of femtosecond pulses in a thick, noncritically phase-matched KNbO(3) crystal under conditions of large group-velocity mismatch. At low power we observed a slope efficiency of ~300% nJ (-1) for harmonic conversion, and at higher powers we generated 170 mW of second-harmonic blue output for 300 mW of input light. Furthermore, we have shown that the focusing dependence for our conditions of large group-velocity mismatch is considerably different from that obtained for frequency doubling of continuous-wave light. We have also demonstrated that one can tune the spectral width of the generated blue light by varying the focusing conditions.     

Double-passed arrayed waveguide grating for 500-GHz pulse burst generation

500-GHz repetition rate pulse bursts on multiple wavelength shifted channels are generated via femtosecond readout of an arrayed waveguide grating (AWG). These bursts are combined onto a single channel by double-passing the AWG, resulting in a substantially increased number of output pulses.