Developments | SC-MPC

The development of this new type of optical cell has been driven by our stringent criteria for compactness, robustness, low volume, and easy-of-use in optical systems. The concept exploits the inherent properties of a circular geometry: seamless, strictly defined and still highly flexible and versatile. It is an ongoing development that was initiated in 2010. The timeline of these activities are shown below:

2010 | the circular concept

The first concept was meant to unify the requirements posed by direct absorption spectroscopy (DAS) and photoacoustics (PA).
The goals of the design are simplicity of alignment, small detection volume and high sensitivity. The latter is achieved with a two-dimensional multipass beam pattern, which also acts as a planar excitation for a longitudinal mode of the drum-like
PA resonator. The planar light distribution in the cell leads to a small detection volume with robust and easy optical alignment.



2012 | monolitichal toroid cell

We proposed an absorption cell consisting of a single optical element that by itself defines the optical cavity. The circular symmetry can be realized as a seamless toroidal ring. The number of passes and thus the optical path length is determined by the angle of incidence, which can easily be calculated from the regular star polygon geometrical rule.



2013 | absorption mask

A solution is found to suppress the optical noise created by stray and scattered light.



2015 | circular paraboloid reflection cell

Improving the alignment tolerance and versatility of the system by generalization of the inner surface curvature. A parabolic mirror shape in a confocal arrangement is found to be more suitable for long optical paths in a small volume. An off-axis in-coupling is also supported. and eventually found its way to a market ready solution.



2015 | IRsweep releases IRCell 4M

The ETH/Empa spin-off company IRsweep includes the mask enhanced toroidal cell into their product portofolio. (



2018 | segmented circular (SC) design

Breaking the circular rotational symmetry, i.e. shifting from concentric to confocal geometry. Relying on fundamental optical-cavity design principles and modern diamond turning techniques, we have developed a segmented circular MPC that allows highly efficient and interference-free beam folding.

No tedious beam shaping is required, and thus very compact setups can be realized.



2022 - now | iSC-MPC

Stay tuned. Coming soon!

  1.  Manninen, A. et al., Versatile multipass cell for laser spectroscopic trace gas analysis. Appl. Phys. B 109, 461–466 (2012). 
    Publication Link

  2.  Tuzson, B. et al., Compact multipass optical cell for laser spectroscopy, Opt. Lett. 38, 257–259 (2013). 
    Publication Link

  3.  Mangold, M. et al., Circular paraboloid reflection cell for laser spectroscopic trace gas analysis, J. Opt. Soc. Am. A 33, 913–919 (2016). 
    Publication Link

  4.  Graf, M. et al., Beam folding analysis and optimization of mask-enhanced toroidal multipass cells, Opt. Lett. 42, 3137–3140 (2017). 
    Publication Link

  5.  Graf, M. et al., Compact, circular, and optically stable multipass cell for mobile laser absorption spectroscopy, Opt. Lett. 43, 2434–2437 (2018). 
    Publication Link