In The Surface Plasmon Microcavity Optical Model And Its Application In Multicolor Quantum Well Detectors

Since the pioneering work of Ritchie in1957, there has been a great deal of interest in confining light strongly at the metal surface by surface plasmons polaritons (SPP). The SPP’s electric field is confined to the metal surface and decays exponentially with the distance away from the metal surface. Large number of photonic density-of-state at the metal dielectric interface is particularly attractive for enhancing light-matter interaction and for improving the performance of light emission and detection. In2004, Okamoto et al. successfully placed semiconductor quantum wells about20nm below a metal surface and observed an enhanced light emission. In2010, C. C. Chang placed quantum dots below a peforated metal surface and obtained an absolutely130%photo detector absorption enhancement. Except for those application in photo emission and detection, SPP has been widely studied for wave guide, super resolution imaging, suface enhanced Raman diffraction and fluorescence, etc. The SPP has become a hot spot in optoelectric or nanophotonics performance improvement applications.On the other hand, the traditional multicolor quantum well infrared photodetectors (M-QWIPs) faces low detectivity and complicated technology process, the reason is that the coupling efficiency is low when the grating couples the incident light into the light with polarization parallel to the quantum well growth direction, but the quantum well can only absorp the light with polarization parallel to the quantum well due to the polarization-selection rule. To meet multi wavelength detection at the same time, grating with different periods are needed and gathered. However, using the plasmonic cavity, by optimize the parameters, we not only improve the light coupling efficiency of light meeting polarization selection rule, but we also improve the quantum well absorption due to the high photonic density-of-state, and thus improve the detectivity. Meanwhile, the multi order and kinds resonances are just suitable for M-QWIPs multi wavelength detection. Therefore, there are several advantages in design new M-QWIPs based on plasmonic cavity.In this paper, we studied a Metal-Insulator-Metal (MIM) structure plasmonic cavity consisting of a perforated metal film and a flat metal sheet separated by a dielectric spacer. We studied the rich optical and plasmnic modes, and their interaction and electric field distribution. Through these studies, we find this cavity is particularly suitable for M-QWIPs application, then we studied the performance of this new design M-QWIPs by FDTD method, we take the two color QWIPs as an example, and achieved about20times absorption enhancement for both wavelength detection.1) There are three resonance modes in the cavity and the hybridized modes coming from them, they are propagating surface plasmon (PSP), localized surface Plasmon (LSP), and Fabry-Perot (FP) cavity mode, respectively. The FP couples weakly with PSP while strongly with LSP. By monitoring the electric field distribution of PSP, LSP, and FP, we find that FP and LSP have a same electric component which is important in both FP and LSP electric components, while the FP and PSP electric components are nearly orthogonal. Therefore, the coupling strength between different modes lies in not only the spatially overlapping but also in whether they share same electric components. The PSP, LSP and FP modes state can be tuned by changing geometric parameters of the cavity. and LSP plays an important role in coupling the incident light into plasmonic cavity.2) By studied the electric field enhancement and electric field distribution of SPP, LSP, FP, and their hybiridized modes of this cavity, we find this cavity is particular suitable for designing a new plasmonic M-QWIPs. We studied the wavelength matching for multicolor detection and found it was able to meet requirements for most cases, finaly, we take a two color QWIPs as an example, we calculate the quantum well absorption for both two wavelength with FDTD methods, and it shows about20times absorption enhancement for both color.Our study clearly shows the optical properties of this plasmonic cavity, and explored an application for M-QWIPs, we believe many other applications can be explored.