BiOBr 2D materials for integrated nonlinear photonics devices

TL;DR

This paper investigates the third-order nonlinear optical properties of BiOBr 2D nanoflakes, demonstrating their potential for integrated nonlinear photonics through experimental characterization and waveguide integration.

Contribution

It provides the first detailed characterization of BiOBr's nonlinearities and demonstrates their integration into silicon waveguides for photonic applications.

Findings

BiOBr exhibits large nonlinear absorption and Kerr coefficients.

The Kerr coefficient n2 reverses sign from negative to positive between 800 nm and 1550 nm.

Nonlinear properties increase as nanoflake thickness decreases.

Abstract

As a new group of advanced 2D layered materials, bismuth oxyhalides, i.e., BiOX (X = Cl, Br, I), have recently become of great interest. In this work, we characterize the third-order optical nonlinearities of BiOBr, an important member of the BiOX family. The nonlinear absorption and Kerr nonlinearity of BiOBr nanoflakes at both 800 nm and 1550 nm are characterized via the Z-Scan technique. Experimental results show that BiOBr nanoflakes exhibit a large nonlinear absorption coefficient = \b{eta} = 10-7 m/W as well as a large Kerr coefficient n2 = 10-14 m2/W. We also note that the n2 of BiOBr reverses sign from negative to positive as the wavelength is changed from 800 nm to 1550 nm. We further characterize the thickness-dependent nonlinear optical properties of BiOBr nanoflakes, finding that the magnitudes of \b{eta} and n2 increase with decreasing thickness of the BiOBr nanoflakes. Finally, we integrate BiOBr nanoflakes into silicon integrated waveguides and measure their insertion loss, with the extracted waveguide propagation loss showing good agreement with mode simulations based on ellipsometry measurements. These results confirm the strong potential of BiOBr as a promising nonlinear optical material for high-performance hybrid integrated photonic devices.