Broadband near Field Characterization of Nanophotonic Devices using Plasmonic Enhance Light Absorption in Scanning Thermal Microscopy (SThM) Probe

Meir Grajower Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Liron Stern Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Boris Desiatov Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Ilya Goykhman Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Yoel Sebbag Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Alex Naiman Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Uriel Levy Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel

Following the general trend of miniaturization and the rapid progress in the field of nanophotonics, there is a growing need for accurate characterization techniques with nanoscale resolution. Currently, the Near Field Optical Microscopy (NSOM) technique is well developed and being used in a wide range of applications [1]. In addition to near field characterization, another byproduct of device miniaturization is the inevitable self-heating of photonic devices, and therefore, thermal characterization of photonic devices at the nanoscale is also important [2]. In order to do so, a Scanning thermal Microscopy (SThM) can be used.

Here, we show that SThM can be used not only for thermal characterization but also, and perhaps mostly, for the measurement of the optical near field profile of a nanophotoinc devices over a very large spectral regime. Specifically, we provide such measurements for over an octave wavelength span ( ). An example of a near field distribution of a silicon waveguide can be seen in Fig 1a and 1c. One can observe two beating periods, one at the submicron scale and the other at the microns scale, which correspond to the counter propagating of the first mode and the co-propagating of the first two modes. For further confirmation we have conducted conventional NSOM measurements, and obtained results which are very similar to the SThM scan (Fig. 1b and 1d).

The ability to measure the near field is due to plasmonic enhanced light absorption inside the SThM prob. In our presentation, we will show several characterization results of photonic and plasmonic components and discuss the methods of distinguishing between the optical near field profile and the thermal profile as obtained from the SThM measurements.

[1] N. Rotenberg & L. Kuipers, Mapping nanoscale, Nature Photonics 8, 919–926 (2014)

[2] M. Tzur, B. Desiatov, I. Goykhman, M. Grajower, and U. Levy, "High resolution direct measurement of temperature distribution in silicon nanophotonics devices," Opt. Express 21, 29195-29204 (2013).

meir.grajower@mail.huji.ac.il