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

Today, most near-field nanoprobes consist of specially processed optical fi bres, which are difficult to fabricate with high reproducibility and in lar ge 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 princip le of detection. The other novelty is that the architecture of a compound-c avity VCSEL with a GaAs micromachined tip, offering a nanometer-scale resol ution of near-field probes, constitutes the first tentative to miniaturise an SNOM microscope. First, we investigate the effects of external optical f eedback on the threshold and spectral characteristics of VCSELs. Second, th eoretical analysis and experimental evidence demonstrate the practicability of VCSEL feedback as a detection principle for SNOM microscopy. Finally, w e propose a compact architecture of an SNOM sensor with a microtip integrat ed on top of the VCSEL and report the preliminary results of fabrication of the integrated device. (C) 2001 Elsevier Science B.V. All rights reserved.