Two-dimensional (2D) photonic crystals offer strong control over the propagation of light through their photonic bands. Theoretical methods to compute the band structure in 2D are well-established and fast because 2D photonic crystals are homogeneous in the third dimension. Experimental verification is scarce, however, especially in the near-infrared (NIR) range including telecom ranges. The reason is that real photonic crystals and experimental methods cannot be homogeneous in the third dimension.

In a new paper, COPS scientists Timon Vreman et al report momentum-resolved reflectivity measurements on photonic crystals that are periodic in two dimensions and homogeneous over a thickness of 5 µm. The high-quality photonic crystals are made from silicon in the Twente Nanolab by CMOS-compatible means (lithography and deep reactive ion etching). Using Fourier spectroscopy, the COPS team carefully select wave vectors in the 2D plane of periodicity of the photonic crystal to experimentally map band structures.

Our experimental results agree excellently with 2D band structure calculations and with 2D finite-difference time-domain simulations. This confirms that our experimental methods truly pertain to nanophotonics in 2D. Our results provide a robust bridge between theory and experiment, and our techniques can be readily extended to other 2D structures, including those with functional defects.

The paper entitled “Momentum-resolved reflectivity of 2D photonic crystals in the near-infrared” is just out in Optics Express, a leading journal published by the professional society “Optica” (formerly Optical Society of America, OSA), see here: https://opg.optica.org/oe/fulltext.cfm?uri=oe-34-1-971. The paper is also available on the COPS website: https://nano-cops.com/publications/article/momentum-resolved-reflectivity-of-a-2d-photonic-crystal-in-the-near-infrared/.

Proud authors of the paper are COPS’ Timon Vreman (recently defended his PhD thesis!), Melissa Goodwin, Ad Lagendijk, and Willem Vos