No abstract

Increasing the working optical bandwidth of a photonic circuit is important for many applications, in particular chemical sensing at mid-infrared wavelengths. This useful bandwidth is not only limited by the transparency range of waveguide materials, but also the range over which a waveguide is single or multimoded for predictable circuit behaviour. In this work, we show the first experimental demonstration of “endlessly single-mode” waveguiding in silicon photonics. Silicon-on-insulator waveguides were designed, fabricated and characterised at 1.95 µm and 3.80 µm. The waveguides were shown to support low-loss propagation (1.46 ± 0.13 dB/cm loss at 1.95 µm and 1.55 ± 0.35 dB/cm at 3.80 µm) and single-mode propagation was confirmed at 1.95 µm, meaning that only the fundamental mode was present over the wavelength range 1.95 - 3.80 µm. We also present the prospects for the use of these waveguides in sensing applications.

We present ring resonator (RR)-coupled Mach-Zehnder interferometers (MZIs) based on silicon-on-insulator rib waveguides, operating around the mid-IR wavelength of 3.8 μm. A number of different photonic integrated devices have been designed and fabricated experimentally to obtain the asymmetric Fano resonances in the mid-IR. We have investigated the influence of the coupling efficiency between the RR and the MZI as well as the phase shift between the two arms of the MZI on the Fano-type resonance spectral features, in agreement with theoretical predictions. Finally, wavelength-dependent Fano transmittances have been successfully measured with insertion losses up to ∼1  dB and extinction ratios of ∼20  dB. A slope of sharp Fano resonances as high as -574.6/μm has been achieved and estimated to be 35.5% higher than the slope of single RR Lorentzian-type resonances.

Beamsplitters are core components of photonic integrated circuits and are often implemented with multimode interference couplers. While these devices offer high performance, their operational bandwidth is still restrictive for sensing applications in the midinfrared wavelength range. Here we experimentally demonstrate a subwavelength-structured 2 × 2 multimode interference coupler with high performance in the 3.1 − 3.7 µm range, doubling the bandwidth of a conventional device.

The 16 th May 2018 marks the first annual International Day of Light (IDL). The steering committee of the IDL initiative encouraged grassroots activities to increase the awareness and understanding of the applications of light. One such undertaking is the program of events developed by the postgraduate students of the Optoelectronics Research Centre (ORC) at the University of Southampton (UoS). The program focused on engaging with the public and local schools with low levels of progression to higher education. Three events were designed: an outreach masterclass, combining activities and demonstrations from well-established workshops covering light in telecommunications, manufacturing and medicine; an art competition in a local school, for students to express scientific knowledge in a creative way; and a public panel, to explore the uses of light in a multitude of disciplines and open academic research to a broader audience. This paper explains how the events built on the ORC students' long history of outreach and the legacy of the International Year of Light. Each event is outlined in detail, explaining the objectives and the rationale behind the audience selection. The program outcomes are described, including the impact, the methods employed and the utilization of expert partners to increase the program reach (commercial media, local schools and UoS's diversity and inclusion outreach department), and the lessons learned from the program are assessed. These experiences can be used to recycle and adapt this format for other grassroots IDL programs. This project received funding through a SPIE IDL Micro Grant.