Abstract
We develop a nanoscopy method with in-depth resolution for layered photonic devices. Photonics often requires tailored light field distributions for the optical modes used, and an exact knowledge of the geometry of a device is crucial to assess its performance. The presented acousto-optical nanoscopy method is based on the uniqueness of the light field distributions in photonic devices: for a given wavelength, we record the reflectivity modulation during the transit of a picosecond acoustic pulse. The temporal profile obtained can be linked to the internal light field distribution. From this information, a reverse-engineering procedure allows us to reconstruct the light field and the underlying photonic structure very precisely. We apply this method to the slow light mode of an AlAs/GaAs micropillar resonator and show its validity for the tailored experimental conditions.
Highlights
Photonic nanostructures, in which light can be guided or confined, are fundamental for a wide range of applications ranging from information communication to cavity-quantumelectrodynamics and optomechanics
Often these techniques are not easy to access and to handle. In this case an established technique is to record the optical reflectivity spectrum and fit simulations based on a transfer matrix approach to the experimental data [5]. The drawback of this method in complicated multilayer structures is that it offers ambiguous in-depth information, since the reflectivity spectrum is an integrated measure determined by the whole structure
In the paper we present at first an analytical equation, which allows us to link the reflectivity modulation to the internal light field distribution along the propagation direction of the acoustic pulse
Summary
In which light can be guided or confined, are fundamental for a wide range of applications ranging from information communication to cavity-quantumelectrodynamics and optomechanics. This interplay has been comprehensively described in a number of publications [18, 19] It turns out, that the properties of (i) the acoustic pulse, namely its duration, the phonon spectrum, and the phonon dispersion in the photonic device, the (ii) light field distribution and (iii) the different mechanisms of light-matter-interaction, like phononphoton and phonon-electron scattering need to be considered for a complete understanding. The route to achieve this is to know all other parameters exactly such that they can be eliminated from the response How this condition can be fulfilled for a practical photonic device by a proper design of the acoustic pulse and choice of the studied light field, is discussed in the present paper. We show that the experimentally measured temporal evolution of the reflectivity allows us to precisely calculate the underlying light field distribution and to determine the geometry of the photonic resonator with in depth-resolution and an accuracy of a few nm
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