2018-03-30 13:54

1 files changed, 138 insertions, 3 deletions

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