Loading...
Please wait, while we are loading the content...
Similar Documents
Design of Plasmon Cavities for Solid-State Cavity QED Applications
| Content Provider | Semantic Scholar |
|---|---|
| Author | Gong, Yiyang Vučković, Jelena |
| Copyright Year | 2007 |
| Abstract | Research on photonic cavities with low mode volume and high quality factor garners much attention because of applications ranging from optoelectronics to cavity quantum electrodynamics (QED). We propose a cavity based on surface plasmon modes confined by metallic distributed Bragg reflectors. We analyze the structure with Finite Difference Time Domain simulations and obtain modes with quality factor 1000 (including losses from metals), reduced mode volume relative to photonic crystal cavities, Purcell enhancements of hundreds, and even the capability of enabling cavity QED strong coupling. The modification of the spontaneous emission (SE) rate of emitters has been a pressing topic in recent research. By enhancing or suppressing emission, we could increase the efficiencies of photon sources, reduce laser threshold, and tailor sources for cavity QED applications such as quantum computation and quantum communications. Some researchers have demonstrated the enhancement of emission rates (Purcell effect) in solid-state by modifying the local density of optical states with photonic crystal (PC) cavities [1]. However, such works face limitations in the mode volume of the cavity. One implementation that could produce smaller mode volumes, and hence higher Purcell factors, is the use of surface plasmon (SP) modes. Already, there have been reports of enhancement of photoluminesence by coupling emitters to regions of high SP density of states (DOS) [2]. Moreover, another group has proposed coupling emitters to metallic nanowires and nanotips to enhance Purcell factors [3]. By employing SP cavities in solid-state, we could attempt to achieve the same or even higher SE rate enhancement as with previous designs, but with simplified fabrication. Several authors have demonstrated decreased transmission by using periodic structures to manipulate SPs [4, 5]. These experiments confirm the existence of backscattering and a plasmonic band gap in metallic gratings. In addition, other groups have demonstrated that surface plasmons interfere as normal waves and set up standing waves under certain conditions [6]. Given such properties, it is easy to conceive of a cavity that is the marriage of the previous two devices, a cavity that contains the electromagnetic field of the plasmon mode with metallic distributed Bragg reflector (DBR) gratings on either side of the cavity. In this letter, we propose such a metallic grating cavity. The structure is shown in Figure 1(a) and is composed of gratings with thin slices of metals on either side of an uninterrupted surface, which forms the cavity. Such a grating will open a plasmonic band gap at a frequency to be determined by the grating periodicity (a). The periodicity of the 1 grating that opens a plasmonic band gap at frequency ω may be determined from the dispersion relationship of SPs at a metal-dielectric interface [7]: ksp = π a = ω c √ ǫdǫm ǫd + ǫm (1) In this work, we assume that the dielectric is GaAs, with permittivity ǫd = ǫGaAs = 12.25, and the metal is silver, with permittivity estimated from the Drude model as ǫm = ǫ∞ − ( ωp ω ), with ǫ∞ = 1 and the plasmon energy of silver as h̄ωp = 8.8eV (λp = 140nm). Setting an operation energy of h̄ω =1.2eV, we determined the grating periodicity to be a = 116nm. Although the metal is only 30nm thick, coupled modes between the air-metal interface and GaAs-metal interfaces have a negligible impact on the dispersion relation. Figure 1: (a) The proposed structure. (b)-(d) Mode profiles (|E|) with cavity lengths 216nm, 328nm, and 440nm, respectively. These correspond to 2, 3, and 4 peaks of the electric field intensity inside the cavity. 2D Finite Difference Time Domain (FDTD) simulations with discretization of 1 unit cell per 2nm were conducted with 5 periods of the DBR gratings on either side of a cavity and using the Drude model for the metal [8]. The depth of grooves in GaAs (filled with metal) and the metal slab layer thickness were both set at 30nm while the groove width was set at 20nm. Here, losses were also included in the Drude model with the damping energy of h̄η = 2.5 × 10eV to simulate low temperature conditions relevant for solid-state cavity QED experiments [1]. This damping factor is equivalent to decreasing the non-radiative losses by approximately a factor of 2000 from their room temperature values (η = ηRT /ξ), where ξ will be called the loss factor. The cavity length was then varied over multiple grating periods to determine its effect on the modes. Three prospective modes with their electric field profiles are shown in Figure 1 and the influence of cavity length on the mode quality factor (Q) and frequency is shown in Figure 2. First, we see that indeed the modes display standing wave patterns inside the cavities. Moreover, the peak quality factors of the modes are separated by grating periods, again supporting the idea that a standing wave is formed by the reflectors on either side of the cavity. The peak quality factor is approximately 1000, and losses are dominated by radiation |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://arxiv.org/pdf/quant-ph/0609169v2.pdf |
| Alternate Webpage(s) | http://arxiv.org/pdf/quant-ph/0609169v1.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
