From 9d8496be4cf2719c3dd7ca2a4b4de91ad4abeeb3 Mon Sep 17 00:00:00 2001
From: Blaise Thompson <blaise@untzag.com>
Date: Fri, 30 Mar 2018 13:54:43 -0500
Subject: 2018-03-30 13:54

---
 opa/chapter.tex | 141 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 138 insertions(+), 3 deletions(-)

(limited to 'opa/chapter.tex')

diff --git a/opa/chapter.tex b/opa/chapter.tex
index b92f62a..75459b5 100644
--- a/opa/chapter.tex
+++ b/opa/chapter.tex
@@ -1,4 +1,7 @@
-\chapter{A robust, fully automated algorithm to collect high quality OPA tuning curves}
+% TODO: DONALDSON HAS AUTOMATED OPA TUNING DOWN?
+
+\chapter{A robust, fully automated algorithm to collect high quality OPA tuning
+  curves} \label{cha:opa}
 
 \begin{dquote}
   Principle design features of the new EVV 2DIR optical delivery system include the following:
@@ -13,6 +16,138 @@
 
 \clearpage
 
-This chapter pasted from publication...
+In frequency-domain Multi-Resonant Coherent Multidimensional Spectroscopy (MR-CMDS), automated
+Optical Parametric Amplifiers (OPAs) are used to actively scan excitation color axes. %
+To accomplish these experiments, exquisite OPA performance is required. %
+During the experiment, motors inside the OPA move to pre-recorded positions to optimize output at
+the desired color. %
+Parametric conversion (``mixing'') strategies are now readily avalible, extending the 800 nm pumped
+OPA tuning range into the visible, near-infrared, and mid-infrared. %
+
+OPAs are very sensitive to changes in upstream lasers and lab conditions, so OPA tuning is
+regularly required. %
+Manual OPA tuning can easily take a full day. %
+Automated OPA tuning makes OPA upkeep easier, faster and more reproducible, facilitating frequency
+domain experiments. %
+The major challenges in automated OPA tuning are:
+\begin{enumerate}
+  \item Expensive to take high resoltion data.
+  \item Need smooth curves for interpolation, especially at edges where output is low.
+  \item Optimization metrics are not necessarily separable along motor dimensions.
+\end{enumerate}
+
+\section{Introduction}  % =========================================================================
+
+\section{TOPAS-C}  % ==============================================================================
+
+% TODO: introduction to the internal design of the OPA
+
+\section{Preamp}  % ===============================================================================
+
+\begin{figure}
+  \includegraphics[width=\textwidth]{opa/preamp}
+  \caption{
+    CAPTION TODO
+  }
+  \label{opa:fig:preamp}
+\end{figure}
+
+In TOPAS-C OPAs, a small portion of input light is used to generate a signal seed in a BBO crystal
+``C1''.  %
+A motorized delay stage ``D1'' is used to temporally overlap a particular color in chirped white
+light with 800 nm pump.  %
+C1 angle is tuned to optimize phase matching.  %
+Measured seed intensity and color for all combinations of C1 and D1 position are shown in
+\autoref{fig:preamp}.  %
+
+Output color and intensity are not separable along the preamp motor axes.  %
+We therefore use a multidimensional fitting strategy to find the best preamp motor positions, as
+shown below.  %
+
+% TODO: procedure
+
+\begin{figure}
+  \includegraphics[width=\linewidth]{opa/autotune_preamp}
+  \caption{
+    CAPTION TODO
+  }
+  \label{opa:fig:autotune_preamp}
+\end{figure}
+
+A representative preamp tune procedure output image is shown in \autoref{fig:autotune_preamp}.  %
+The thick black line is the final output curve.  %
+The dark grey lines are the contours of constant color.  %
+The colorbar shows the Delaunay-interpolated intensity values for each motor position.  %
+
+Preamp tuning takes less than 20 minutes, in large part due to a NIR array detector which collects
+the full spectrum at each motor position.  %
+
+\section{Poweramp}  % =============================================================================
+
+\begin{figure}
+  \includegraphics[width=\linewidth]{opa/poweramp}
+  \caption{
+    CAPTION TODO
+  }
+  \label{opa:fig:poweramp}
+\end{figure}
+
+Once generated, the seed goes on to be amplified in a second BBO crystal ``C2'' with the rest of
+the 800 nm pump.  %
+Optimizing this amplification step is primarily a matter of setting C2 angle.  %
+A small delay correction ``D2'' is necessary to account for dispersion in the seed optics.  %
+To fully explore poweramp behavior, we need to tak a C2-D23 scan for each seed color.  %
+Measured output intensity and color in this 3D space is represented in \autoref{fig:poweramp}.  %
+Note that the motor axes are scans about the previously recorded tuning curve value.  %
+
+The best position (zero displacement along both axes) is chosen to maximize output intensity while
+keeping the output color identical to the seed color.  %
+Optimizing for zero detuining rather than simply for output intensity has led to better OPA
+performance and stability.  %
+Like in the preamp case, color and intensity are not fully separable along the poweramp motor
+dimensions (this is especially true at the edge output colors).  %
+In the poweramp, the increased dimensionaity makes it too expensive to do a full multidimensional
+tuning procedure.  %
+Instead we emply an iterative procedure as diagrammed below.  %
+
+% TODO: procedure
+
+We always end the iteration(s) with C2 so that the OPA's color calibration is as good as
+possible.  %
+Typically only one iteration is required but multiple iterations may be necessary if dramatic OPA
+realignment has occurred.  %
+In total, poweramp tuning typically takes less than 1 hour. %
+Representative procedure output images for D2 (\autoref{op:fig:d2}) and C2 (\autoref{opa:fig:c2})
+are shown.  %
+
+\begin{figure}
+  \includegraphics[width=\textwidth]{opa/d2}
+  \caption{
+    CAPTION TODO
+  }
+  \label{opa:fig:d2}
+\end{figure}
+
+\begin{figure}
+  \includegraphics[width=\textwidth]{opa/c2}}
+  \caption{
+    CAPTION TODO
+  }
+  \label{opa:fig:c2}
+\end{figure}
+
+For the D2 figure, the lower panel shows the intensity of the data taken.  %
+Note the thick grey line, which represents the chosen points before the final spline step.  %
+The top panel compares the old tuning curve (thin) with the output tuning curve (thick).  %
+For the C2 image, the bottom panel represents the color of each fit mapped onto detuning.  %
+Each separate marker color represents a different setpoint.  %
+As with D2, the C2 upper panel compares the old tuning curve (thin black) with the output tuning
+curve (colored X's).  %
+
+\section{Mixers}  % ===============================================================================
+
+\section{Generalizability}  % =====================================================================
+
+\section{Future directions}  % ====================================================================
 
-% DONALDSON HAS AUTOMATED OPA TUNING DOWN?
\ No newline at end of file
+% TODO: discuss Attune
\ No newline at end of file
-- 
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