Photonic Laboratory, College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China.
Opt Lett. 2012 Oct 1;37(19):4107-9. doi: 10.1364/OL.37.004107.
The confinement of light within nanometer-scale regions may result in the significant enhancement of light-matter interactions. However, light confinement to nanometers is hindered by the diffraction limit of a dielectric material. For a dielectric cavity, if the material loss is negligible, reducing the cavity size usually causes a significantly increase in radiation loss. Surface plasmons show great promise for potential subwavelength light confinement. However, in most circumstances, light confinement by dissipative metallic materials can cause ohmic losses at optical frequencies. In such cases, the realization of light confinement with deep subwavelength mode sizes results in great losses and thus has low quality factors. In the present study, a three-dimensional light confinement with deep subwavelength mode sizes is achieved using dielectric spheres in metal cavities. Contrary to other mechanisms for subwavelength light confinement that are based on the use of dielectric or metal cavities, the nanometer-scale regions ensure that most of the light energy is confined away from the metal-dielectric interfaces, thereby decreasing light absorption in the metal cavity. In turn, the metal cavity decreases the radiation loss of light. Thus, high quality factors ranging from 2×10(2) to 6×10(2) can be obtained at room temperature. An effective electrical mode volume ranging from 7×10(-5)λ(0)(3) to 2×10(-4)λ(0)(3) (where λ(0) is the resonant wavelength in a vacuum) can be achieved. Therefore, this method of three-dimensional light confinement with deep subwavelength mode sizes using dielectric spheres in metal cavities may have potential applications in the design of nanolasers, nanophoton detectors, nonlinear optical switches, and so on.
光在纳米尺度区域的限制会导致光物质相互作用的显著增强。然而，由于介电材料的衍射极限，光限制在纳米范围内受到阻碍。对于介电腔，如果材料损耗可以忽略不计，那么减小腔的尺寸通常会导致辐射损耗显著增加。表面等离子体在潜在的亚波长光限制方面有很大的应用前景。然而，在大多数情况下，耗散金属材料的光限制会导致光频下的欧姆损耗。在这种情况下，实现具有深亚波长模式尺寸的光限制会导致很大的损耗，从而导致低品质因数。在本研究中，使用金属腔中的介电球实现了具有深亚波长模式尺寸的三维光限制。与基于使用介电或金属腔的其他亚波长光限制机制不同，纳米尺度区域确保大部分光能量被限制在远离金属-介电界面的区域，从而减少金属腔中的光吸收。反过来，金属腔减少了光的辐射损耗。因此，在室温下可以获得 2×10(2)到 6×10(2)的高品质因数。可以实现有效电模体积为 7×10(-5)λ(0)(3)到 2×10(-4)λ(0)(3)（其中 λ(0)是真空中的共振波长）。因此，使用金属腔中的介电球实现深亚波长模式尺寸的三维光限制的这种方法可能在纳米激光器、纳米光子探测器、非线性光学开关等的设计中有潜在的应用。
