2018-04-09 14:01

1 files changed, 42 insertions, 0 deletions

diff --git a/active_correction/chapter.tex b/active_correction/chapter.tex
index 6e773ec..f4447d0 100644
--- a/active_correction/chapter.tex
+++ b/active_correction/chapter.tex
@@ -44,8 +44,50 @@ I hope to show that active correction is a particularly useful strategy in MR-CM
 

 [FIBRILLATION]

 

+\clearpage

 \section{Spectral delay correction}  % ============================================================

 

+As a frequency domain technique, MR-CMDS requires automated tuning of multiple OPAs.  %

+These OPAs generate pulses, which are then manipulated and directed into a sample of interest.  %

+Crucially, the relative arrival time of each pulse must be carefully controlled in the context of

+the MR-CMDS experiment.  %

+Unfortunately, changing the output frequency also changes the optical path length, meaning that

+there is some unavoidable coupling between delay and frequency axes.  %

+Because we have full control over delay through delay stages, we can correct for this phenomenon by

+choosing a different zero delay \emph{offset} for each OPA output color.  %

+This strategy has been dubbed ``spectral delay correction''.  %

+

+Spectral delay correction (SDC) is certainly the longest running active correction strategy employed

+within the Wright Group.  %

+SDC was first implemented by Schuyler Kain within his COLORS acquisition software. [CITE]  %

+COLORS' implementation was hardcoded for one particular OPA / delay configuration---it wasn't until

+PyCMDS that fully arbitrary SDC became possible through the autonomic system (see section ...).  %

+Erin Boyle ``backported'' similar functionality into to ps\_control, although her implementation

+allowed only for a simple, first order linear correction.  %

+

+Sometimes, spectral delay can be corrected for after-the-fact.  %

+Post processed spectral delay correction can only be done if all relevant delays are scanned during

+the experiment.  %

+A common example is transient absorption, where the single delay axis is typically scanned at each

+color coordinate.  %

+A special method of \python{Data}, \python{Data.offset} is designed to do the necessary

+interpolation for \emph{post hoc} SDC.  %

+

+In many experiments spectral delay must be actively corrected for.  %

+Fully coherent experiments do 

+

+It has been found that SDC is necessary for each individual scanned OPA, and for each separate path

+when pulses from a single OPA are split.  %

+The difference between different paths is typically small, but enough to move pulses a noticeable

+amount relative to each-other.  %

+For this reason, SDC for split OPAs is a multidimensional problem, which in principle requires a

+multi-dimensional acquisition to fully record.  %

+In practice, however, these corrections are recorded iteravely.  %

+

+[ALTHOUGH ACTIVE, CAN SOMETIMES BE CORRECTED FOR IN POST: SEE WRIGHTTOOLS.OFFSET]

+

+[SDC IN CONTEXT OF WHITE LIGHT]

+

 \begin{figure}

 	\includegraphics[width=0.45\textwidth]{"active_correction/sdc_before"}

  	\includegraphics[width=0.45\textwidth]{"active_correction/sdc_after"}