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% TODO: Rapid and economical data acquisition in ultrafast frequency-resolved spectroscopy using
% choppers and a microcontroller https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-16-18126
\chapter{Hardware} % -----------------------------------------------------------------------------
In this chapter I collect some of the specific hardware contribution details that do not belong in
the body of the dissertation. %
\section{Adjustable periscopes} % ----------------------------------------------------------------
OPAs output horizontal or vertical polarizations according to which tuning process is used. %
Our experiments are opinionated about polarization, so some strategy for aligning polarization is
necessary. % TODO: cite opinionated about polarization
In addition, it is useful to bring all excitation beams to the same height. %
To this end, I designed and constructed two adjustable periscopes. %
Each periscope is designed to bring OPA output to table height standard (5 inches) while either
keeping or switching polarization. %
Both polarization configurations take the same path length, so source polarization can be switched
without large changes to zero delay. %
All of this is done with just two (switched polarization) or three (kept polarzation)
reflections. %
A picture of these periscopes is shown in \ref{f:periscope}. %
\begin{figure}[htp!]
\centering
\includegraphics[width=\textwidth]{"hardware/periscope"}
\label{f:periscope}
\caption{CAPTION TODO}
\end{figure}
While these periscopes are easy to align, their unique design means that it is not necessarily
obvious what the correct strategy is. %
The following strategy will always converge:
\begin{enumerate}
\item use two ``magic'' apertures along the output beamline
\item in flipped polarization (two mirror configuration):
\begin{itemize}
\item use the stage (green X, Y) to align near aperture
\item use the upper mirror (yellow TA, TB) to align far aperture
\item iterate above
\end{itemize}
\item in kept polarization (three mirror configuration):
\begin{itemize}
\item use stage X (green X) and upper mirror height (yellow TC) to align near aperture
\item use lower mirror (pink SA, SB) to align far aperture
\item iterate above
\end{itemize}
\end{enumerate}
The kept polarization alignment is derivative of the fixed polarization alignment. %
One must ensure that the fixed polarization is correctly aligned at all times. %
Mirror B (aqua) is magnetically mounted to switch between polarization conditions. %
Ensure that the lower turning mirror (pink) does not bump into mirror B (aqua) in polarization
swtiching configuration. %
The lower turning mirror is on a rail (pink SC). %
This rail is a rough adjust for the same degree of freedom as pink SA. %
Adjust the rail only to ensure that the beam is roughly centered on the free aperture of the
turning mirror. %
The first reflection is often accomplished using a wedge, as OPA output may be strong enough to
damage downstream optics. %
This optic can and should be replaced if more of the OPA output is desired on the table (keeping
damage thresholds in mind). %
\subsection{Wedge polarization preference}
TODO: wedges will be more efficent at reflecting horizontal / vertical at 45 degrees
\section{Automated transmissive filters} % -------------------------------------------------------
TODO
\section{Electronics} % --------------------------------------------------------------------------
TODO
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