Microwave arbitrary waveform generation using a direct space-to-time optical pulse shaper

Abstract

Fourier transform optical pulse shaping [1] is now a well established technology for generating nearly arbitrarily shaped ultrafast optical pulses, with applications ranging from coherent control to high-speed communications. On the other hand, arbitrary waveform generation (AWG) capabilities for microwave electromagnetic signals are quite limited. Microwave arbitrary waveform generators could be important for a number of applications, including RF test and measurement instrumentation, secure and multiple-access wireless communications, and radar. Commercial AWG instrumentation is limited to the range below 1 GHz. The use of shaped optical pulses to drive a high-speed optical-to-electronic (O/E) converter offers the possibility to dramatically improve the state-of-the-art in microwave AWG. In previous work in our group, we used pulse sequences from a Fourier transform (FT) pulse shaper to drive a THz photoconductive antenna, resulting in generation of freely propagating phase- and amplitude-modulated THz radiation signals [2]. Another group recently used a wavelength-division multiplexing technique together with a series of optical fiber delay lines to produce a series of pulses suitable for generating a phase-modulated waveform in the low («6) GHz range [3]. Here we demonstrate for the first time to our knowledge microwave arbitrary waveform generation at center frequencies up to 50 GHz, thereby filling in the void between the previous results. Our work takes advantage of a novel direct space-to-time (DST) pulse shaper [4], which provides pulse shaping over a 100 psec temporal window, as required for waveform generation at tens of GHz.