Photonic microcavities (PMC) coupled through their evanescent field are used for a large variety of classical and
quantum devices. In such systems, a molecular-like spatial delocalization of the coupled modes is achieved by an evanescent tunnelling. The tunnelling rate depends on the height and depth of the photonic barrier between two
adjacent resonators and therefore it is sensitive to the fabrication-induced disorder present in the center of the
In this contribution, we address the problem of developing a post fabrication control of the tunnelling rate in photonic crystal coupled PMCs. The value of the photonic coupling (proportional to the tunnelling rate) is directly measured by the molecular mode splitting at the anticrossing point. By exploiting a combination of tuning techniques such as local infiltration of water, micro-evaporation, and laser induced non thermal micro-oxidation, we are able to either increase or decrease the detuning and the photonic coupling, independently. Near field imaging is also used for mapping the modes and establish delocalization.
By water micro-infiltration, we were able to increase the photon coupling by 28%. On the contrary, by
laser induced non thermal oxidation, we got a reduction of g by 30%. The combination of the two methods would therefore give a complete control of g with excellent accuracy. This could make possible the realization of array of photonic cavities with on demand tunnelling rate between each pair of coupled resonators. We believe that this peculiar engineering of photonic crystal molecules would open the road to possible progress in the exploitation of coherent interference between coupled optical resonators both for quantum information processing and optical communication.
Massimo Gurioli, "Imaging and tuning of coupled photonic crystal cavities
(Conference Presentation)," Proc. SPIE 9885, Photonic Crystal Materials and Devices XII, 98850L (Presented at SPIE Photonics Europe: April 06, 2016; Published: 26 July 2016); https://doi.org/10.1117/12.2225628.5042345215001.
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