New SNOM sensor using optical feedback in a VCSEL-based compound-cavity

Abstract

Today, most near-field nanoprobes consist of specially processed optical fibres, which are difficult to fabricate with high reproducibility and in large number. To overcome this handicap, we propose a miniaturised near-field sensor. One of the novelties is to use the optical feedback properties of a vertical-cavity surface-emitting laser (VCSEL) cavity as an active principle of detection. The other novelty is that the architecture of a compound-cavity VCSEL with a GaAs micromachined tip, offering a nanometer-scale resolution of near-field probes, constitutes the first tentative to miniaturise an SNOM microscope. First, we investigate the effects of external optical feedback on the threshold and spectral characteristics of VCSELs. Second, theoretical analysis and experimental evidence demonstrate the practicability of VCSEL feedback as a detection principle for SNOM microscopy. Finally, we propose a compact architecture of an SNOM sensor with a microtip integrated on top of the VCSEL and report the preliminary results of fabrication of the integrated device.