Spotlight on “Comparison of raised-microdisk whispering-gallery-mode characterization techniques”

It is a common perception that the fabrication of nanoscale optical devices is often so challenging that it makes technology approach fine art. What is not so commonly recognized is that even the measurement of such devices often requires a master’s touch. Characterization techniques must be not only nondestructive, but also nonperturbative, i.e., the behavior of the device under test (DUT) must not be altered by the measurement apparatus. This sounds obvious, but the problem of test probes is critical in optics, where an equivalent of the probe pins available in electronics does not exist, and sometimes it is hard to evaluate how much manipulation is brought on by inspection.