Influence of a NSOM probe shape on a photonic crystal microcavity mode coupling

PC-based microcavity can present a large quality factor (Q) while preserving a small modal volume (V), thus enabling the high Q/V ratio required for studying cavity quantum electrodynamics at the single source level. To analyze the coupling between the sources and the cavity, one must observe directly and locally the field distribution inside the cavity. Because of the small size of such a cavity, far-field techniques, which are usually diffraction-limited, fail to achieve the needed resolution. In the present work, we emphasize the influence of the probe on NSOM measurement of PC-cavity modes. The intensity near-field map showed that the coupling seems to be done preferentially along the direction of the long axis of the tip. We compared the experimental cartography to the computed intensity of the field component parallel to the long axis and showed that the agreement between them was correct.