Fiber Front End With Multiple Phase Modulations and High-Bandwidth Pulse Shaping for High-Energy Laser-Beam Smoothing

Abstract

The design and performance of a fiber front end delivering temporally shaped, phase-modulated optical pulses to a large-scale, high-energy laser system to demonstrate beam-smoothing concepts are presented. High-bandwidth LiNbO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> (lithium niobate) Mach–Zehnder modulators and arbitrary waveform generators temporally shape the power of the optical pulses. High-bandwidth, three-section LiNbO <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> phase modulators precisely modulate the optical phase of the pulses at up to three microwave frequencies. Various calibration procedures and fail-safe systems are described. Sources of frequency-modulation-to-amplitude-modulation conversion, which can lead to unsafe operation of the high-energy laser system, are identified and compensated by amplitude and dispersion compensators.