Hong-Ou-Mandel Interference for Multilayered AZO/ZnO Metamaterial

Aluminum-doped zinc oxide metamaterial emerged as a promising plasmonic material due to its low optical loss and high conductivity. The Hong-Ou-Mandel effect is a result of two photons interfering on a beam-splitter. The coincidence rate of the detectors will drop to zero when the identical input photons overlap perfectly in time which results in the Hong-Ou-Mandel dip. If the time delay is scanned, the position of the HOM dip can be measured with femtosecond precision. Therefore, this two-photon interference effect has the potential for applications in precision measurement of time delays. Here, we experimentally observed Hong-Ou-Mandel interference for multilayered AZO/ZnO metamaterial. The Hong-Ou-Mandel effect was observed using a biphoton source with a periodically-poled Potassium Titanyl Phosphate crystal and two single photon counting modules monitoring the output from a beam splitter at 810 nm wavelength. The coincidence probability for separable photons, as a function of time delay τ, was fitted using least square method. The multilayered AZO/ZnO sample (carrier concentration 1020 -1021cm-3) on quartz substrate was used for delay. Our measurements show that the extracted time delay τ=25 µm for multilayered AZO/ZnO was about two orders of magnitude larger than expected from the thickness of the sample.