Optimised performance of non-dispersive infrared gas sensors using multilayer thin film bandpass filters

Pinggui Wang, Xiuhua Fu, Des Gibson, Lewis Fleming, Sam Ahmadzadeh, Cheng Li, Manu Muhiyudin, Shigeng Song, David Hutson, David Moodie, Calum Macgregor, Mathew Steer

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Abstract

In this work, performance improvements are described for a low-power consumption non-dispersive infrared (NDIR) methane (CH4) gas sensor using customised optical thin film bandpass filters (BPFs) centered at 3300 nm. BPFs shape the spectral characteristics of the combined mid-infrared III–V based light emitting diode (LED)/photodiode (PD) light source/detector optopair, enhancing the NDIR CH4 sensor performance. The BPFs, deposited using a novel microwave plasma-assisted pulsed DC sputter deposition process, provide room temperature deposition directly onto the temperature-sensitive PD heterostructure. BPFs comprise germanium (Ge) and niobium pentoxide (Nb2O5) alternating high and low refractive index layers, respectively. Two different optical filter designs are progressed with BPF bandwidths (BWs) of 160 and 300 nm. A comparison of the modelled and measured NDIR sensor performance is described, highlighting the maximised signal-to-noise ratio (SNR) and the minimised cross-talk performance benefits. The BPF spectral stability for various environmental temperature and humidity conditions is demonstrated.
Original languageEnglish
Article number472
Number of pages16
JournalCoatings
Volume8
Issue number12
DOIs
Publication statusPublished - 19 Dec 2018

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Keywords

  • NDIR
  • Methane
  • Sensor
  • Infrared
  • thin film
  • III-V
  • heterostructure
  • bandpass
  • microwave
  • sputter
  • MBE

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