  Accurate readout of low-power optical higher-order spatial modes is of
increasing importance to the precision metrology community. Mode sensors are
used to prevent mode mismatches from degrading quantum and thermal noise
mitigation strategies. Direct mode analysis sensors (MODAN) are a promising
technology for real-time monitoring of arbitrary higher-order modes. We
demonstrate MODAN with photo-diode readout to mitigate the typically low
dynamic range of CCDs. We look for asymmetries in the response our sensor to
break degeneracies in the relative alignment of the MODAN and photo-diode and
consequently improve the dynamic range of the mode sensor. We provide a
tolerance analysis and show methodology that can be applied for sensors beyond
first-order spatial modes.
