Developed under NASA-JPL funding we have built a completely non-mechanical FTIR system; our prototype liquid crystal waveguide Fourier transform spectrometer (LCW-FTS).
While far from the ultimate potential of this technology, this prototype already has impressive performance for a completely non-mechanical system.
The instrument resolution is approximately 5 nm, with a near-IR spectral range of 1450 – 1700 nm.
Future versions will have a larger spectral range and improved resolution (possibly down to 0.1 nm).
A broadband super luminescent diode (SLD) light source is integrated into the system.
The ultimate potential attributes of this sensor:
i)
small size, comparable to a book of matches,
ii)
low mass, only tens of grams,
iii)
small energy consumption, < 10
-3
Watt-hours per measurement,
iv
)
high sensitivity, detectable chemical densities < 10
13
per cm
3
, and
v)
robust monolithic construction.
Such a sensor can be integrated and deployed with a variety of exploration platforms. A single device may provide identification and quantification of multiple compounds (e.g., biogenically important CH
4
, NH
4
,
NO
x
, H
2
O, and many more).
The ultimate potential attributes of this sensor: i) small size, comparable to a book of matches, ii) low mass, only tens of grams, iii) small energy consumption, < 10 -3 Watt-hours per measurement, iv ) high sensitivity, detectable chemical densities < 10 13 per cm 3 , and v) robust monolithic construction, are aptly suited for future NASA missions. Such a sensor can be integrated and deployed with a variety of exploration platforms. A single device may provide identification and quantification of multiple compounds (e.g., biogenically important CH 4 , NH 4 , NO x , H 2 O, and many more).
Example performance of the LCW-FTS prototype is shown in Figure 2 and 3. Shown in Figure 2 are interferograms for single frequency laser sources. The top interferogram is for two lasers. The beat pattern of the two lasers is clearly visible in the interferogram. The insets show the spectrum of the light sources. Figure 3 shows interferograms and FFT obtained spectra of a broadband SLD with some broadband spectral absorption features. First, on the top is a plot of the SLD spectra with no absorption features. Next, a 12 nm wide notch filter is placed between the LCW-interferometer and the detector. This 12 nm notch is then used as a mirror. Finally, the light is transmitted through an acetylene cell. The acetylene absorption is clearly visible. All of these spectra agree well with similar spectra recorded with a desktop sized optical spectrum analyzer. The corresponding interferograms for each spectra are shown on the right. The interferograms are only plotted out to 100 microns to highlight the differences, even though the actual data extend to about 400 microns.