Near-Field Optics with Single Photon Detectors and a Photon Time-Tagger

Probing condensed matter systems with quantum light can provide direct measurements of coherence and entanglement among collective electronic excitations. Combining near-field microscopy with quantum light enables the measurement of these properties in real-space and at the collective excitation’s native length scales.

In traditional scattering-type scanning near-field optical microscopy (s-SNOM), the tip oscillation modulates the coupling between the incident light and the tip-sample interaction at integer multiples of the tip frequency. A lock-in detector can then eliminate any optical signal that does not oscillate at the desired multiple of the tip frequency, allowing for the extraction of the true near-field signal.

However, the single photon detectors needed for detecting quantum light output a pulse with constant amplitude to denote the photon count rate; demodulating the optical signal in this digital pulse regime with a lock-in amplifier is no longer feasible. In this talk, I will discuss alternative methods for extracting a near-field signal using single photon detectors and a photon time-tagger.