Realization of Both High Absorption of Active Materials and Low Ohmic Loss in Plasmonic Cavities

摘要

Enhancing active material absorption and suppressing ohmic loss is desired by a lot of applications based on plasmonic structures. In this work, an effective photonic approach is presented to achieve this purpose in plasmonic cavities. Enhancing the absorption ratio of the active material to the metal (by properly increasing the volume of the active region), and meanwhile keeping the system close to a critical coupling status for perfect light trapping (by switching the resonance to a higher-order one or making real facets as the cavity boundaries) is proposed. As a photonic approach, this is generally applicable to different plasmonic materials. With the help of this approach, the absorption of the quantum wells in a plasmonic-cavity-integrated quantum well infrared photodetector operating in the longwave infrared range can be enhanced to 82% of the incident power and the ohmic loss can be suppressed to 18%. For plasmonic-cavity-integrated GaAs devices operating in the near infrared range, the approach can enhance the active material absorption to 78% of the incident power and suppress the ohmic loss to 20% at the wavelengths close to the bandgap. Also, it would improve the performance at a more extended wavelength.