Tailoring Ultrashort Pulses for Surface Structuring and Characterizing Ultrashort Pulses PDF Download

Author: Billy Lam (Optics scientist)
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ISBN:
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Languages : en
Pages : 0

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Book Description
"This thesis is focused on the methods for tailoring ultrashort pulses for surface structuring and the methods for characterizing ultrashort pulses. In other words, the primary goal is to modulate as well as measure the spatio-temporal electric field E(x, y, t) = |E(x, y, t)|e i[phi](x,y,t) of an ultrashort pulse. Existing vector optical field (VOF) generators are either inefficient or require many optical elements with intensive alignment. I have demonstrated both a non-diffraction-based and a diffraction-based VOF-generator with a theoretical efficiency close to 100% using a spatial light modulator (SLM) to shape the focus of a femtosecond (fs) laser beam arbitrarily for surface structuring. Besides the beam focus, I have also fabricated curved laser-induced periodic surface structure (LIPSS) out-of-focus by controlling the polarization distribution of the beam. Both VOF-generators are compact with only a few optical elements and are easy to align for fs laser beams. These methods present an effective and energy-efficient way to shape the fs laser beam dynamically to create complex surface structures. For beam characterization, I have developed the wedged reversal shearing interferometer (WRSI), consisting of a single beam splitter cube (BSC), to retrieve the spatially resolved electric field E(x, y). The main advantages of the WRSI over existing techniques are its simplicity, stability, robustness, capability, and guaranteed zero-delay for ultrashort pulses. The WRSI can also be used together with a scanning Michelson interferometer, along with an additional temporal measurement using frequency-resolved optical gating (FROG), to measure the spatio-temporal field E(x, y, t). In addition, this thesis explores a new method to temporally characterize (E(t)) an ultrashort pulse with precise information on the carrier-envelope phase (CEP) in a single-shot operation. A feat unachievable by previous methods such as FROG and spectral phase interferometry for direct electric-field reconstruction (SPIDER), since spectrally resolved autocorrelation and spectral shear are insensitive to the CEP. The CEP is an important parameter of a few-cycle pulse because the CEP can vary from pulse to pulse and has a large impact on laser-matter interaction. The ability to measure the spectral phase and CEP of an arbitrary non-repeating ultrashort event is important for the study of ultrafast optical phenomena"--Pages xi-xii.