High-resolution, ultrafast laser pulse shaping and its applications

Abstract

Publisher Summary It is now possible to generate laser pulses, with extremely sophisticated phase and amplitude modulation, or to generate complex laser pulse sequences, with well-defined phase relationships, between the pulses. This has been proved useful in a wide range of spectroscopic applications, such as nuclear magnetic resonance (NMR), which has evolved into an extraordinarily important technique for monitoring structure and dynamics and a diagnostic tool of outstanding clinical value and it is now possible to create staggeringly complex excitation sequences. Useful sequences do not require anything approaching state-of-the-art radiofrequency (rf) capabilities; commercially available arbitrary waveform generators (AWGs) can give possible voltage waveform with ≈1 ns rise time, covering the radiofrequency spectrum at one time. The nanosecond switching time of common digital components is far faster than NMR relaxation times, but far slower than optical relaxation times. The most commonly used laser pulse sequences work, because they do not require specific pulse shapes or bandwidths and are unaffected by phase shifting any individual pulse in the sequence. The rapid rise times of ultrafast laser pulses implies a far greater bandwidth than is conceivable at microwave frequencies. With the addition of a laser and a few optical components a commercial NMR spectrometer could shape femtosecond laser pulses. In this chapter, it is shown that this approach has advantages of rapid waveform update rates (100 kHz–1MHz), commercially available components, simplicity (the phase and amplitude modulation is encoded with a single rf pulse), and extremely high resolution pulse shaping ( ≈ 1000 independently adjustable amplitudes and phases). A variety of applications in quantum control and optical communications have been discussed in the chapter. The chapter discusses various optical modulation techniques, characterization of shaped laser pulses, effective resolution limits, with acousto-optic pulse shaping, and optimal design for maximum resolution without distortions.