We propose to advance the state of the art in multi-pass optical cell technology by bringing several novel, previously unpublished, cell architectures to better maturity and to the attention of other researchers. Optical multi-pass cells are devices that are fundamental to achieving high sensitivity in spectroscopic instruments for gas detection and measurement. The proposed project is a unique opportunity for NASA to advance multi-pass optical cell technology in several new directions at once, addressing multiple fundamental design advances with potentially large and lasting impact on the future design of optical instrumentation. The specific NASA SBIR solicitation technical topic that we address, S1.08 Suborbital instruments and sensor systems for earth science measurements, includes development needs for reduced volume multi-pass cell designs and optical subsystems for open path measurements. The solicitation topic also calls for small trace gas sensors suitable for UAV’s, which need low-volume multipas cells. The work we propose addresses stated needs for advances in optical absorption cells and related subsystems, both for open path as well as closed path (low volume) measurements. One of the cell designs we have conceived is specifically for open path measurements, where the base length may vary with the experimental circumstances. That design, the “Retro-Cat Cell” combines a remote retroreflector with an “inboard” mirror combination that acts like a variable focal length mirror, so it can adapt to variable base length. We present four different pathways for improving path-length per unit volume in multi-pass cells. These pathways range from simple filling of excess volumes, to re-injection systems to a new cell architecture. These development pathways are expected to yield results that improve existing commercial multi-pass cells, improve existing instrumentation and make new more compact instrumentation possible.
These multi-pass cell advances will positively impact NASA scientific endeavors that rely upon optical detection of gases, particularly in its Earth Sciences Division. Our new open-path cell design may be useful for increasing the path-length of measurement systems such as the NASA LaRC Diode Laser Hygrometer. New closed path cell designs may be of benefit to numerous NASA centers involved in trace gas measurements, such as: Goddard, Langley, JPL and Glenn. We note those centers because we previously sold then trace gas instruments or cells.
The new open-path cell design will have application to industrial settings with variable base paths, such as fence-line monitoring, or in environmental measurements where the measurement circumstances change. Closed path cells are integral to the set of trace gas instruments produced and sold by ARI, so new designs will enhance our products and capabilities.