Study Of Plasmonic Micro-cavity Light Coupling Based On The Quantum Well Infrared Photo-electric Detecting

Infrared detector is a kind of photoelectric conversion sensing device for infrared radiation. As one of the core technologies for infrared detection, it has been extensively applied in military and civil fields. In the past three decades, as III-V semiconductor technology becomes even more mature, infrared detector has got rapid development based on III-V semiconductor quantum well(QW) in material preparations and device applications. Its advantage is its good uniformity and high repeatability. Compared with Hg Cd Te(MCT) infrared detector, QW infrared detector is more suitable for low cost, high-performance and focal plane array detectors. The energy band engineering of the intersubband transition makes the detection wave band of the QW structure can extends from the infrared to the terahertz region. Particularly in the long wave infrared wavelengths, it has greater advantage. But because of the limitation of quantum selection rule, incident light cannot be directly absorbed, and the optical coupling structure is necessary to excite the intersubband transition. Now the low efficiency of the optical coupling has been one of the bottlenecks restricting the development of QW infrared detector.In this thesis, we propose a new type of plasmonic microcavity structure, with the integration of quantum well infrared detector. It plays an important role in improving performance of the quantum well:1. The plasmonic microcavity and quantum well integrated device shows strong optical coupling effect. In this hybrid structure of artificial metal structure-insulator-metal reflection layer, the photo response improvement benefited from the optical properties and the photoelectric conversion is discussed in details: a)the Localized Surface Plasmon(LSP) mode and the Surface Plasmon Polariton(SPP)mode of the plasmonic microcavity are observed simultaneous in the detection wavelength region. We discuss their excitation principle of the two modes, through the dependence analysis of the structure parameters and electromagnetic field simulation; b) The LSP mode under the Au strip forms transverse resonance.Considering light field and QW absorption in the resonant cavity, we construct the QW absorption model in the Fabry-Perot cavity, and put forward the optical response of the plasmonic microcavity devices; c) the experimental results show that the strongcoupling effect enhances the quantum well infrared photodetector’s response. Due to the new structure, compared with the conventional 45 degrees coupled quantum well photodetector, the peak response will increase by 33 times, and the enhancement factor is nearly 160 at the LSP mode wavelength.2. The high-polarization-discriminating capability of the integration device of the plasmonic microcavity and quantum well has been achieved. a) The analysis of the important role in integrated micro polarizer for real-time solid detection; b)Integrated device, through the dual control mechanism including polarization discrimination of the plasmonic microcavity and the QW polarization selection rules,achieves high polarization discrimination ability. Then we construct the scattering factor S perturbation model, and discuss the physical processes of the plasmonic microcavity devices and the polarization extinction ratio formula theoretically; c) The experimental results and related discussions are presented. Theoretical analysis and experimental results are very consistent, the structure achieves polarization extinction ratio as high as 65(polarization selectivity is 97%) in the very long wavelength infrared region(14.2-14.9 ?m).3. Plasmonic microcavity-quantum well devices have the red shift effect for the cutoff wavelength. The conventional methods of electronic states control realize the detection wavelength to long wave direction, but it will lead to the dark current violently increase. Here we achieve the red shift of the detection wavelength with the photonic mode control method. With the plasmonic microcavity structure, huge enhancement of the QW absorption has been achieved at weak absorption region and it can avoid the increase of the dark current. Experiments show that the cutoff wavelength can be extended by 8%.In addition to the enhancement of the optical absorption, the coupled plasmonic microcavity structures and devices can also realize the convergence of the light. The integration of the plasmonic microcavity together with In Ga As/In P avalanche photodiod(APDs) devices can achieve ultimate sized APDs(its diameter is less than 5μm). Comparing with the conventional APDs, the coupled devices shrink the size of nearly two orders of magnitude. We designed this ultimate size, low dark count APDs,while ensuring their quantum efficiency theoretically.