Utilizing Broadband Light From a Superluminescent Diode for Excitation of Photonic Crystal High-Q Nanocavities

Because silicon photonic crystal (PC) high-quality factor (high-Q) nanocavities are useful for the development of novel optical devices with small sizes, they have been subject to intense research. In many of these research works, continuous-wave (cw) lasers were used as excitation light sources. However, cw lasers can be disadvantageous for certain applications. In this study, we report on the excitation of high-Q resonance modes of PC nanocavities by a superluminescent diode (SLD). Since the emission from the SLD has a broad spectrum that extends over several tens of nanometers, it is able to simultaneously excite many nanocavities with significantly different resonance wavelengths. Furthermore, the SLD is able to excite the high-Q resonance modes in a stable manner; SLD excitation achieves cavity emission intensities that are hardly influenced by resonance-wavelength shifts due to temperature changes or natural surface oxidization. We demonstrate that by using the SLD as excitation light source, the emission from a nanocavity with a Q of several tens of thousands can be clearly observed by a near-infrared InGaAs camera. In addition, we demonstrate the refractive-index change sensing using the SLD excitation of a nanocavity array as an application example.