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Sep 23

Engineering photonics at FLAIR 2016

The FLAIR conference, now in its 5th edition, brings together industrial and academic researchers to explore and discuss field laser applications for sensitive and selective detection of molecular species. This edition was held for the first time in the beautiful French mountain resort town of Aix-les-Bains. With a particular interest in gas sensing applications, Jane, Sarah and Nick attended, presenting three posters describing their work on both the use of integrating spheres as gas cell and the use of specific lasers for methane detection.

Sarah, Jane, and Nick attending the FLAIR conference in Aix-les-Bains.

Sarah, Jane, and Nick visiting the Château de Menthon-Saint-Bernard near Annecy during the FLAIR conference.

 

The poster topics are as follows:

 

Methane detection using an external cavity Bragg grating stabilised laser at 1651nm

N.M. Davis, S.G. Lynch, J.C. Gates, J. Hodgkinson, P.G.R. Smith and R.P. Tatam

Typically, commercially available laser diodes in the near infrared have to be custom made at a particular wavelength, such as Distributed Feedback (DFB) lasers. This requires significant investment with potentially low yields. The latest results in the development of a new, external cavity, Bragg stabilised laser for tunable diode laser spectroscopy (TDLS) were presented. The design uses a silicon-on-silicon platform incorporating a UV written Bragg grating as the wavelength selective element of the laser cavity. Thus, custom wavelengths can be written “on demand” with relatively low capital investment.

 

High frequency modulation for pathlength calibration of an integrating sphere

S. Bergin, T. Kissinger, J. Hodgkinson, and R.P. Tatam

Pathlength calibration presents one of the major challenges for integrating sphere gas cells as the achievable pathlength is a sensitive function of the sphere wall reflectivity. The use of high frequency laser intensity modulation allows for the pathlength to be calculated in real time, and without the requirement for a reference gas cell.

Setup used for high frequency laser intensity modulation for integrating sphere pathlength calibration.

Setup used for high frequency laser intensity modulation for integrating sphere pathlength calibration.

ICL based TDLS instrument developed for airborne measurements of atmospheric methane.

ICL based TDLS instrument developed for airborne measurements of atmospheric methane.

Detection of methane at 3.3µm using an integrating sphere and Interband Cascade Laser for environmental applications

N.M. Davis, D. Francis, J. Hodgkinson and R.P. Tatam

Several platforms are used worldwide for airborne atmospheric monitoring of various gases, based on tunable diode laser spectroscopy (TDLS). For high signal-to-noise ratios multipass optical cells are used, which are difficult to align and increase the problem of optical interference fringes. On aircraft, high levels of vibration and large temperature fluctuations compromise performance compared with laboratory operation. We have developed a gas sensor for use on aircraft using an ICL, allowing for the detection of the fundamental absorption bands of methane at 3.3µm, and an integrating sphere as the gas cell. These cells are easy to align, insensitive to vibration and do not produce interference fringes.