Polarization selective devices, such as polarizers and polarization selective resonant cavities (e.g., gratings and ring resonators), are core components for polarization control in optical systems and find wide applications in polarizationdivision- multiplexing, coherent optical detection, photography, liquid crystal display, and optical sensing. In this paper, we demonstrate integrated waveguide polarizers and polarization-selective micro-ring resonators (MRRs) incorporated with graphene oxide (GO). We achieve highly precise control of the placement, thickness, and length of the GO films coated on integrated photonic devices by using a solution-based, transfer-free, and layer-by-layer GO coating method followed by photolithography and lift-off processes. The latter overcomes the layer transfer fabrication limitations of 2D materials and represent a significant advance towards manufacturing integrated photonic devices incorporated with 2D materials. We measure the performance of the waveguide polarizer for different GO film thicknesses and lengths versus polarization, wavelength, and power, achieving a very high polarization dependent loss (PDL) of ~ 53.8 dB. For GOcoated integrated MRRs, we achieve an 8.3-dB polarization extinction ratio between the TE and TM resonances, with the extracted propagation loss showing good agreement with the waveguide results. Furthermore, we present layer-by-layer characterization of the linear optical properties of 2D layered GO films, including detailed measurements that conclusively determine the material loss anisotropy of the GO films as well as the relative contribution of film loss anisotropy versus polarization-dependent mode overlap, to the device performance. These results offer interesting physical insights and trends of the layered GO films from monolayer to quasi bulk like behavior and confirm the high-performance of integrated polarization selective devices incorporated with GO films.
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 β ~ 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 β 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.
We experimentally characterize the third-order optical Kerr nonlinearity of BiOBr nanoflakes via Z-Scan technique. Strong nonlinear absorption as well as high Kerr nonlinearity (n2) are observed at both 800 nm and 1550 nm, with a large nonlinear absorption coefficient on the order of 10-7 m/W and a high Kerr coefficient on the order of 10-14 m2/W being measured.
We experimentally demonstrate integrated waveguide polarizers and polarization-selective micro-ring resonators (MRRs) incorporated with layered graphene oxide (GO) films. We achieve a high polarization dependent loss (PDL) of ~53.8 dB for the GO-coated waveguide and a high polarization extinction ratio of ~8.3 dB for the GO-coated MRR.
We experimentally demonstrate enhanced optical Kerr nonlinearity of hybrid integrated waveguides coated with layered graphene oxide (GO) films. Owing to the high Kerr nonlinearity of GO and strong mode overlap between GO and waveguide, up to ~9.5-dB enhancement of four wave mixing (FWM) conversion efficiency is achieved.
Owing to the ease of preparation as well as the tunability of its material properties, graphene oxide (GO) has become a rising star of the graphene family. In our previous work, we found that GO has an ultra-high Kerr nonlinear optical response - several orders of magnitude higher than that of silica and even silicon. Moreover, as compared with graphene, GO has much lower linear loss as well as nonlinear loss (two photon absorption (TPA)), arising from its large bandgap (2.4~3.1 eV) being more than double the photon energy in the telecommunications band. Here, we experimentally demonstrate enhanced four-wave mixing (FWM) in hybrid integrated waveguides coated with GO films. Owing to strong mode overlap between the integrated waveguides and the high Kerr nonlinearity GO films as well as low linear and nonlinear loss, we demonstrate significant enhancement in the FWM efficiency. We achieve up to ~9.5-dB enhancement in the conversion efficiency for a 1.5-cm-long waveguide with 2 layers of GO. We perform FWM measurements at different pump powers, wavelength detuning, GO film lengths and numbers of layers. The experimental results verify the effectiveness of introducing GO films into integrated photonic devices in order to enhance the performance of nonlinear optical processes.