16:15 〜 16:30
▲ [15p-2C-10] Suppression of two-photon absorption in a high-Q SiC photonic-crystal nanocavity
キーワード：Silicon Carbide,photonic crystal nanocavity,two-photon absorption
High-Q nanocavities have so far been demonstrated with Si- (Eg ~ 1.1 eV) based photonic crystals. However, two-photon absorption occurs due to their small modal volumes and small electronic bandgap. Because carriers generated by two-photon absorption have various negative effects on cavity resonance, Si-based high-Q nanocavities are in general difficult to use when the input power increases. To address this issue, we previously proposed to use a wide bandgap semiconductor SiC (Eg ~ 3.2 eV) as a material of the photonic-crystal nanocavities. We developed SiC-based photonic-crystal nanocavities with Q factor of ~10,000, and showed that the multi-photon absorption can be substantially suppressed. As separately reported in this conference, we have just succeeded in developing much higher Q factor of SiC nanocavity with Q of >100,000. In this paper, we will report that two-photon absorption can be suppressed even with such a high-Q factor (>200,000) SiC nanocavity.
We prepared Si and SiC photonic crystal nanocavities having similar high Q factors (230,000 and 200,000, respectively). As seen in Fig. 1, an input waveguide is introduced nearby to couple light evanescently into the cavities. The resonance spectrum of each cavity was measured by the standard method for various input powers of CW laser. The input power was defined as the power inside the waveguide, and the radiation efficiency was defined as the ratio of the radiation power to the input power. As the input power increased, the radiation spectrum in the Si nanocavity became red-shifted even at 10mW, due to the two-photon absorption, the successive free-carrier effects and heat generation. On the other hand, the radiation spectrum in the SiC nanocavity does not change up to 460mW (measurement limit). It is clear that SiC nanocavity does not suffer from two-photon absorption even for almost mW input power level for the Q factor as large as 200,000. Such stable high-Q SiC nanocavities should be useful for various applications including add-drop filters, nonlinear frequency converters, and even Raman amplification devices. Further details will be presented at the conference.
We prepared Si and SiC photonic crystal nanocavities having similar high Q factors (230,000 and 200,000, respectively). As seen in Fig. 1, an input waveguide is introduced nearby to couple light evanescently into the cavities. The resonance spectrum of each cavity was measured by the standard method for various input powers of CW laser. The input power was defined as the power inside the waveguide, and the radiation efficiency was defined as the ratio of the radiation power to the input power. As the input power increased, the radiation spectrum in the Si nanocavity became red-shifted even at 10mW, due to the two-photon absorption, the successive free-carrier effects and heat generation. On the other hand, the radiation spectrum in the SiC nanocavity does not change up to 460mW (measurement limit). It is clear that SiC nanocavity does not suffer from two-photon absorption even for almost mW input power level for the Q factor as large as 200,000. Such stable high-Q SiC nanocavities should be useful for various applications including add-drop filters, nonlinear frequency converters, and even Raman amplification devices. Further details will be presented at the conference.