Leary C C, Baumgardner L A, Raymer M G
Oregon Center for Optics and Department of Physics, University of Oregon, Eugene, OR 97403, USA.
Opt Express. 2009 Feb 16;17(4):2435-52. doi: 10.1364/oe.17.002435.
We describe a mode sorter for two-dimensional parity of transverse spatial states of light based on an out-of-plane Sagnac interferometer. Both Hermite-Gauss (HG) and Laguerre-Gauss (LG) modes can be guided into one of two output ports according to the two-dimensional parity of the mode in question. Our interferometer sorts HG(nm) input modes depending upon whether they have even or odd order n+m; it equivalently sorts LG(l)(p) modes depending upon whether they have an even or odd value of their orbital angular momentum l. It functions efficiently at the single-photon level, and therefore can be used to sort single-photon states. Due to the inherent phase stability of this type of interferometer as compared to those of the Mach-Zehnder type, it provides a promising tool for the manipulation and filtering of higher order transverse spatial modes for the purposes of quantum information processing. For example, several similar Sagnacs cascaded together may allow, for the first time, a stable measurement of the orbital angular momentum of a true single-photon state. Furthermore, as an alternative to well-known holographic techniques, one can use the Sagnac in conjunction with a multi-mode fiber as a spatial mode filter, which can be used to produce spatial-mode entangled Bell states and heralded single photons in arbitrary first-order (n+m = 1) spatial states, covering the entire Poincar e sphere of first-order transverse modes.
我们描述了一种基于面外萨格纳克干涉仪的用于光的横向空间态二维奇偶性的模式分选器。根据所讨论模式的二维奇偶性，厄米 - 高斯（HG）模式和拉盖尔 - 高斯（LG）模式都可以被引导到两个输出端口之一。我们的干涉仪根据HG(nm)输入模式的阶数n + m是偶数还是奇数来进行分选；等效地，它根据LG(l)(p)模式的轨道角动量l的值是偶数还是奇数来进行分选。它在单光子水平上高效运行，因此可用于分选单光子态。与马赫 - 曾德尔型干涉仪相比，由于这种类型干涉仪固有的相位稳定性，它为量子信息处理中高阶横向空间模式的操纵和滤波提供了一种很有前景的工具。例如，几个类似的萨格纳克干涉仪级联在一起可能首次允许对真正单光子态的轨道角动量进行稳定测量。此外，作为众所周知的全息技术的替代方法，可以将萨格纳克干涉仪与多模光纤结合用作空间模式滤波器，它可用于产生空间模式纠缠的贝尔态，并在任意一阶（n + m = 1）空间态中产生预示单光子，覆盖一阶横向模式的整个庞加莱球。
