2019 Spectroscopy

New photonic platforms for the mid-infrared (Invited paper)
Milos Nedeljkovic1,*, Ahmed Osman1, Jordi Soler Penadés1, Tiantian Li2, Callum G. Littlejohns1,4, Zhibo
Qu1, Yangbo Wu1, Wei Cao,1 Alejandro Sanchez Postigo3, Alejandro Ortega-Moñux3, Gonzalo
Wangüemert-Pérez3, Robert Halir3, Íñigo Molina-Fernández3, Hong Wang4, Zhiping Zhou2, Graham T.
Reed1, and Goran Z. Mashanovich1
1 Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ United Kingdom
2 State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Electronics
Engineering and Computer Science, Peking University, Beijing, 100871 China
3Universidad de Málaga, Departamento de Ingeniería de Comunicaciones, ETSI Telecomunicación, Spain
4 Silicon Technologies Centre of Excellence, Nanyang Technological University, 639798 Singapore
*e-mail: m.nedeljkovic@soton.ac.uk

ABSTRACT
Mid-infrared (MIR) group-IV photonics has seen rapid development in recent years amidst interest in developing integrated photonic systems that could be used for applications in sensing and free-space communications. In particular there is a focus on mid-infrared absorption spectroscopy, since many gases,
chemicals, and biological molecules exhibit strong and unique absorption features in this part of the electromagnetic spectrum (approximately 3-16 𝜇m). To achieve this low loss waveguide platforms must be developed that span the MIR. To this end we have investigated suspended silicon, germanium-on-silicon, and
suspended germanium waveguides, which are expected to be transparent throughout the MIR range. Optical absorption and phase modulators may also be useful in a variety of integrated MIR systems, but modulation in Si and Ge in the MIR is not yet well understood. We have therefore fabricated and tested silicon-on-insulator free carrier injection modulators for 3.8 𝜇m, and germanium-on-silicon carrier injection modulators for 3.8 𝜇m and 8 𝜇m.
Keywords: silicon photonics, mid-infrared, waveguides

New photonic platforms for the mid-infrared


Nanophotonics Integration for Astrophotonics (Invited paper)
Mario Dagenais
Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742
e-mail: dage@ece.umd.edu

ABSTRACT
Astrophotonics is used to reject sharp emission lines in the earth atmosphere and allows for the observation of the spectrum of faint celestial objects using earth telescopes. An integrated filter is demonstrated that can reject 47 telluric narrow OH lines and that can reach high throughput. A new type of integrated optical filter is also demonstrated that would facilitate the detection of life in the atmosphere of exoplanets with much smaller telescopes.
Keywords: integration, photonics, Bragg gratings, exoplanets, OH lines

Nanophotonics Integration for Astrophotonics


On-chip surface enhanced Raman spectroscopy using ALD grown plasmonic nanotrenches integrated with a silicon nitride slot waveguide (’Student Paper’)
Ali Raza ; 1;2, St´ephane Clemmen 1;2;3, Michiel Van Daele 4, Jolien Dendooven 4,
Matthew B. E. Griffiths 5, Se´an T. Barry 5, Andre Skirtach2;6, Christophe Detavernier 4,
Roel Baets 1;2
1Ghent University – imec, Technologiepark 126, 9052 Ghent, Belgium
2Center for Nano- and Biophotonics, Ghent University, Belgium
3Laboratoire d’information quantique, Universit´e Libre de Bruxelles, 1050 Bruxelles, Belgium
4Department of Solid State Sciences, COCOON Research Group, Krijgslaan 281, 9000 Ghent, Belgium
5Department of Chemistry, Carleton University, 1125 Ottawa, Canada
6Department of Biotechnology, Ghent University, 9000 Ghent, Belgium
*e-mail: ali.raza@ugent.be

ABSTRACT
We present an enhanced Raman spectroscopy using sub 10 nm plasmonic nanotrenches directly grown on a silicon nitride slot waveguide using atomic layer deposition (ALD). A novel ALD process for gold deposition at 100 C is used, the precursor and reactant used for this process are Me3AuPMe3 and H2 plasma, respectively.
The fabricated Raman sensor exhibits  1.5  10􀀀8 pump to Stokes conversion efficiency for a monolayer of 4-Nitrophenol. This is at least an order of magnitude higher than the state of art nanoplasmonic waveguide based Raman sensors.
Keywords: Nanoplasmonics, Integrated Optics, Surface enhanced Raman spectroscopy, Waveguide enhanced Raman spectroscopy, Monolayer sensing, Atomic layer deposition

On-chip surface enhanced Raman spectroscopy using ALD grown plasmonic nanotrenches integrated with a silicon nitride slot waveguide


Mid-infrared absorption spectroscopy of protein aggregates using germanium on silicon waveguides
V. Mittal1, G. Devitt2, P.N. Bartlett3, H. M. H. Chong4, G. Z. Mashanovich1, S. Mahajan2 and J. S. Wilkinson1
1 Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ United Kingdom
2 Institute for Life Sciences, University of Southampton, Southampton, SO17 1BJ United Kingdom
3 School of Chemistry, University of Southampton, Southampton, SO17 1BJ United Kingdom
4 School of Electronics and Computer Science, University of Southampton, Southampton, SO17 1BJ United Kingdom
e-mail: v.mittal@soton.ac.uk

ABSTRACT
Proteins in human samples can be used to detect the onset of a group of neurodegenerative diseases such as Alzheimer’s and Parkinson’s by studying their conformational (shape and structure) changes that can cause cognitive impairment. Proteins form aggregates from normal state (monomers) to disease state (amyloid deposition and fibril formation in central nervous system) that is associated with disease progression. These changes can be diagnosed and monitored using mid-infrared (MIR) absorption spectroscopy by studying line shapes and relative absorbance of amide bands. We have demonstrated MIR spectroscopy of proteins in three stages of aggregation: monomers, oligomers and fibrils of Bovine Serum Albumin (BSA) protein on a germanium on silicon (GOS) waveguide in the MIR wavelength region of 5.2 – 10 μm (1900 – 1000 cm-1). The protein samples were also characterised by atomic force microscopy to confirm their structure.
Keywords: mid-infrared, spectroscopy, protein, waveguide, integrated optics, biosensing

Mid-infrared absorption spectroscopy of protein aggregates using germanium on silicon waveguides