Abstract
Optical spectroscopy can be used to analyze matter in many contexts: clinical, environmental, industrial, and beyond. Typical light sources employed for this are either spectrally broad lamps and LEDs or monochromatic lasers. Supercontinuum (SC) “white light” lasers constitute a unique class of light sources that combine the beam quality of lasers with a very broad spectral bandwidth. In this thesis, we have explored the potential of these promising instruments in gas sensing applications, such as cavity enhanced absorption spectroscopy and differential absorption lidar. In addition to developing bright and broadband ultraviolet and infrared SC sources and utilizing them in spectroscopic techniques, we have dedicated one study to analyzing SC stability in the long-pulse regime, as these types of sources are efficient yet intrinsically unstable.
In the context of simultaneous ultra-sensitive detection of multiple molecular species in a laboratory, we have researched and improved upon a technique called incoherent broadband cavity-enhanced absorption spectroscopy in two studies. First, by using a custom near-IR SC, we have achieved the highest recorded detection sensitivity for this technique, which is in the ppb-range. Secondly, by using a mid-IR SC, we have demonstrated this technique for the first time in the molecular fingerprint region, with the broadest reported measurement bandwidth, spanning over 400 nm. In the industrial measurement context, we have developed a completely novel short-range SC lidar for remote measurements of temperature and concentration profiles in combustion units. This technique shows a lot of promise, even if the initial measurement accuracy leaves room for improvement.
Although all of these results are somewhat handicapped by the intrinsic instability of the long-pulse SC sources used, we have shown that custom-tailored SC sources can be used to greatly enhance the performance of suitable spectroscopic techniques. They can also enable completely new types of measurement technologies, like the SC lidar, which will hopefully inspire future research.
In the context of simultaneous ultra-sensitive detection of multiple molecular species in a laboratory, we have researched and improved upon a technique called incoherent broadband cavity-enhanced absorption spectroscopy in two studies. First, by using a custom near-IR SC, we have achieved the highest recorded detection sensitivity for this technique, which is in the ppb-range. Secondly, by using a mid-IR SC, we have demonstrated this technique for the first time in the molecular fingerprint region, with the broadest reported measurement bandwidth, spanning over 400 nm. In the industrial measurement context, we have developed a completely novel short-range SC lidar for remote measurements of temperature and concentration profiles in combustion units. This technique shows a lot of promise, even if the initial measurement accuracy leaves room for improvement.
Although all of these results are somewhat handicapped by the intrinsic instability of the long-pulse SC sources used, we have shown that custom-tailored SC sources can be used to greatly enhance the performance of suitable spectroscopic techniques. They can also enable completely new types of measurement technologies, like the SC lidar, which will hopefully inspire future research.
| Original language | English |
|---|---|
| Place of Publication | Tampere |
| Publisher | Tampere University |
| ISBN (Electronic) | 978-952-03-1743-0 |
| ISBN (Print) | 978-952-03-1742-3 |
| Publication status | Published - 2020 |
| Publication type | G5 Doctoral dissertation (articles) |
Publication series
| Name | Tampere University Dissertations - Tampereen yliopiston väitöskirjat |
|---|---|
| Volume | 330 |
| ISSN (Print) | 2489-9860 |
| ISSN (Electronic) | 2490-0028 |