Light-Matter Interactions in Photonic Crystals

我们建议研究光子晶体和相关纳米结构中新颖的基本光-物质相互作用。这些材料的新颖性源于它们以独特的方式捕获光的能力，以及设计光子与物质中共振电子激发之间的超强耦合的能力。我们建议阐明这些材料在太阳能收集、光学信息处理、新型光源和光学生物传感方面的实际应用。我们将与领先的实验和纳米制造小组密切合作，以实现我们的理论和数值建模的预测。 我们建议在下一代光伏中开发用于光捕获、吸收和太阳光谱重塑的薄膜光子晶体结构。我们的工作将集中在改变亚波长尺度上基本光子-物质相互作用的光子体系结构的计算设计、合成和光学测试上。设计的架构提供了新的范例来控制、捕获和转换太阳能，并压缩太阳能电池内太阳光的频率带宽。我们增强的光捕获和太阳吸收的基本物理是通过将太阳光耦合到光子晶体的慢光模式，这些模式在横向于薄膜表面的方向传播。这对应于光子态密度相对于均匀材料的光子态密度增强的光谱范围。我们的方法包括将梯度减反射结构与基于光子晶体的光捕获和吸收相结合。这使得薄膜(500纳米)太阳能电池的光吸收能力可以与厚(~300微米)电池相媲美，并超过了之前提出的统计射线捕获限制。光子晶体在低于太阳能电池电子带隙的频率下，通过背镜附近的等离子体共振增强，实现了光子的非线性上转换。这种对太阳能光谱的光谱压缩为单结硅太阳能电池实现超过30%的太阳能发电转换效率铺平了道路。研究了随机结构无序在光子晶体太阳能电池中的作用及其对整体太阳能转换效率的影响。 我们提出了一条在室温或近室温下实现激子相干和玻色-爱因斯坦凝聚的新途径。这涉及到一种由三维光子带隙(PBG)材料实现的新型量子腔。这一提议的基本科学进展依赖于PBG材料的两个独特和基本的性质：(I)通过抑制激子在特定频率范围内的辐射复合，有可能将激子的寿命延长到远远超过在囚禁激子气体中建立热力学平衡所需的时间尺度。(Ii)3DPBG材料能够实现更强的亚波长限制和光聚焦(无损耗)，从而导致比以前研究的1D光腔实现更强的激子-光子耦合。我们将研究激子玻色凝聚体中量子多体关联的性质，并考虑凝聚体辐射衰变时类激光发光的性质。我们建议设计能够实现激子和光子之间的超强耦合的结构，以使平衡玻色凝聚温度接近室温。我们将与能够合成我们设计的光子晶体结构的制造小组以及在表征激子凝聚体方面经验丰富的实验光学小组密切合作。

We propose to study novel and fundamental light-matter interactions in photonic crystals and related nano-structures. The novelty of these materials results from their ability to trap light in unique ways and to engineer ultra-strong coupling between photons and resonant electronic excitations in matter. We propose to elucidate the practical applications of these materials to solar energy harvesting, optical information processing, novel light sources, and optical bio-sensing. We will work closely with leading experimental and nano-fabrication groups to realize the predictions of our theoretical and numerical modeling. We propose to develop thin-film photonic crystal architectures for light trapping, absorption and solar spectral reshaping in next generation photovoltaics. Our effort will focus on the computational design, synthesis, and optical testing of photonic architectures that alter fundamental photon-matter interactions at sub-wavelength scales. The designed architectures offer new paradigms to control, trap, and convert solar energy and to compress the frequency bandwidth of sunlight within the solar cell. The underlying physics of our enhanced light trapping and solar absorption is the through the coupling of sunlight to slow-light modes of the photonic crystal that propagate in directions transverse to the thin-film surface. This corresponds to a spectral range where the photonic density of states is enhanced relative to that of a homogeneous material. Our approach involves the integration of graded anti-reflection architectures with photonic crystal based light-trapping and absorption. This enables light absorption in thin-film (< 500 nanometer) solar cells to rival that of thick (~300 micron) cells and to surpass previously suggested statistical ray trapping limits. Strong light concentration by the photonic crystal, augmented by plasmonic resonances near the back mirror, at frequencies below the solar cell electronic band gap enable nonlinear up-conversion of photons. This spectral compression of the solar spectrum paves the way to solar-to-electricity power conversion efficiency by single junction silicon solar cells exceeding 30%. The role of random structural disorder in the photonic crystal solar cells and its influence on overall solar power conversion efficiency will be investigated. We propose to study a new route to the realization of excitonic coherence and Bose-Einstein condensation at or near room temperature in GaAs multiple quantum well (QW) structures. This involves a new type of quantum cavity enabled by a 3D photonic band gap (PBG) material. The essential scientific advance in this proposal rests on two unique and fundamental properties of PBG materials: (i) By inhibiting radiative recombination of excitons over a specific range of frequencies, it is possible to extend the exciton lifetime well beyond the time scale required to establish thermodynamic equilibrium in a trapped exciton gas. (ii) 3D PBG materials enable stronger, sub-wavelength confinement and focusing of light (without loss), thereby leading to much stronger exciton-photon coupling than achievable with previously studied 1D optical cavities. We will study the nature of quantum many-body correlations in the excitonic Bose condensate and consider the nature of laser-like light emission as the condensate decays radiatively. We propose to design structures that enable ultra-strong coupling between excitons and photons such that equilibrium Bose condensation temperature approaches room temperature. We will work closely with fabrication groups that can synthesize our designed photonic crystal architectures and with experimental optics groups with experience in characterizing excitonic condensates.