  Advanced photonic probing techniques are of great importance for the
development of non-contact wafer-scale testing of photonic chips. Ultrafast
photomodulation has been identified as a powerful new tool capable of remotely
mapping photonic devices through a scanning perturbation. Here, we develop
photomodulation maps into a quantitative technique through a general and
rigorous method based on Lorentz reciprocity that allows the prediction of
transmittance perturbation maps for arbitrary linear photonic systems with
great accuracy and minimal computational cost. Excellent agreement is obtained
between predicted and experimental maps of various optical
multimode-interference devices, thereby allowing direct comparison of a device
under test with a physical model of an ideal design structure. In addition to
constituting a promising route for optical testing in photonics manufacturing,
ultrafast perturbation mapping may be used for design optimization of photonic
structures with reconfigurable functionalities.
