Grajower Meir, Desiatov Boris, Goykhman Ilya, Stern Liron, Mazurski Noa, Levy Uriel
Opt Express. 2015 Oct 19;23(21):27763-75. doi: 10.1364/OE.23.027763.
In recent years, following the miniaturization and integration of passive and active nanophotonic devices, thermal characterization of such devices at the nanoscale is becoming a task of crucial importance. The Scanning Thermal Microscopy (SThM) is a natural candidate for performing this task. However, it turns out that the SThM capability to precisely map the temperature of a photonic sample in the presence of light interacting with the sample is limited. This is because of the significant absorption of light by the SThM probe. As a result, the temperature of the SThM probe increases and a significant electrical signal which is directly proportional to the light intensity is obtained. As such, instead of measuring the temperature of the sample, one may directly measure the light intensity profile. While this is certainly a limitation in the context of thermal characterization of nanophotonic devices, this very property provides a new opportunity for optical near field characterization. In this paper we demonstrate numerically and experimentally the optical near field measurements of nanophotonic devices using a SThM probe. The system is characterized using several sets of samples with different properties and various wavelengths of operation. Our measurements indicate that the light absorption by the probe can be even larger than the light induced heat generation in the sample. The frequency response of the SThM system is characterized and the 3 dB frequency response was found to be ~1.5 kHz. The simplicity of the SThM system which eliminates the need for complex optical measurement setups together with its broadband wavelength of operation makes this approach an attractive alternative to the more conventional aperture and apertureless NSOM approaches. Finally, referring to its original role in characterizing thermal effects at the nanoscale, we propose an approach for characterizing the temperature profile of nanophotonic devices which are heated by light absorption within the device. This is achieved by spatially separating between the optical near field distribution and the SThM probe, taking advantage of the broader temperature profile as compared to the more localized light profile.
近年来，随着无源和有源纳米光子器件的小型化与集成化，此类器件在纳米尺度上的热特性表征正成为一项至关重要的任务。扫描热显微镜（SThM）是执行这项任务的天然候选工具。然而，事实证明，在存在与样品相互作用的光的情况下，SThM精确绘制光子样品温度的能力是有限的。这是因为SThM探针会大量吸收光。结果，SThM探针的温度升高，并获得与光强成正比的显著电信号。这样一来，人们可能直接测量的是光强分布，而非样品的温度。虽然这在纳米光子器件热特性表征的背景下无疑是一个局限，但这一特性为光学近场表征提供了新机遇。在本文中，我们通过数值模拟和实验展示了使用SThM探针进行纳米光子器件的光学近场测量。该系统使用了几组具有不同特性和不同工作波长的样品进行表征。我们的测量表明，探针的光吸收甚至可能大于样品中光致热产生。对SThM系统的频率响应进行了表征，发现3 dB频率响应约为1.5 kHz。SThM系统的简单性消除了对复杂光学测量装置的需求，再加上其宽带工作波长，使得这种方法成为比更传统的孔径和无孔径近场扫描光学显微镜（NSOM）方法更具吸引力的替代方案。最后，鉴于其在纳米尺度热效应表征中的原始作用，我们提出了一种表征因器件内光吸收而受热的纳米光子器件温度分布的方法。这是通过在空间上分离光学近场分布和SThM探针来实现的，利用了与更局部化的光分布相比更宽的温度分布。
