Seamless integrating cavity of monolithic fumed silica
Inventors
Moore, Thomas • Retherford, Kurt D. • Phillips-Lander, Charity
Assignees
Southwest Research Institute SwRI
Publication Number
US-12298235-B2
Publication Date
2025-05-13
Expiration Date
2041-04-30
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Abstract
A seamless fumed silica monolithic integrating cavity device tailored to analyzing a flowed sample. The device is configured to facilitate optical measurements taken from a sample flowed through a cavity of the device. The cavity is defined by a fumed silica monolith with the added feature of a fused quartz lining on the surface of the monolith. This provides an intermediate surface that allows for cleaning and reuse of the highly effective diffuse light scattering fumed silica monolith. The lining may be placed under pressure or vacuum to structurally enhance mechanical integrity of the underlying monolith. Thus, continued or reliably repeated use of the device may be appreciated as well as use in more industrial environments that are prone to vibration. Additionally, while well suited for flow-based sample analysis, a valve of the cavity may be utilized for holding a sample in a temporarily static state for measurement.
Core Innovation
The invention introduces a seamless integrating cavity device featuring a monolithic fumed silica core with a fused quartz liner to provide an optically effective and reusable system for measurement of samples. The device enables flowing or static samples to be analyzed as they move through, or are held within, a central cavity defined by the liner and surrounded by the fumed silica monolith. An outer housing and end caps enclose the monolith and liner, ensuring the assembly remains seamless and environmentally isolated.
This device addresses persistent problems in optical measurement accuracy and durability associated with integrating cavities. Existing systems are plagued by seams that act as light paths and introduce losses or by highly reflective surfaces like fumed silica that, though superior in reflectivity, suffer from contamination, short usable life, and structural fragility. By combining a seamless architecture and the use of a transparent, cleanable fused quartz liner, the device solves these issues by protecting the delicate, high-reflectivity fumed silica and enabling repeated cleanings and use in harsher environments.
The integrating cavity’s configuration—where the liner provides structural integrity and easy cleaning, and the monolithic fumed silica supplies enhanced diffuse reflectivity—means the device supports uniform light distribution and highly accurate optical characteristic measurements. The system is adaptable for both dynamic (flow-through) and static (valved) sample analysis, making it versatile for a range of optical test applications requiring high sensitivity and reliability.
Claims Coverage
The patent includes one independent claim, which describes a measurement system for optical sample analysis with several inventive features.
Seamless integrating cavity device with fumed silica monolith and fused quartz liner
The system uses a seamless integrating cavity defined by a liner of fused quartz covering a fumed silica monolith. The monolith is sandwiched in an air-tight manner between the liner and an outer housing. The device includes an inlet through the material leading to the cavity for receiving a sample item. This construction ensures the elimination of seams, provides enhanced reflectivity, and maintains environmental isolation.
Light source for optical scattering within cavity
The system incorporates a light source configured to supply light into the cavity for scattering by the monolithic fumed silica. This light source enables the measurement of scattered light resulting from the interplay between the sample and the diffuse reflective material.
Spectral detector for acquisition of scattered light readings
A spectral detector is arranged to acquire the scattered light readings from the cavity, facilitating analysis of the sample item. The detector enables optical characteristic analysis based specifically on the light scattered within the integrating cavity device.
In summary, the patent claims a seamless integrating cavity system leveraging a fumed silica monolith and a fused quartz liner, with integrated optical light-supplying and detecting components for precise analysis of a flowed or static sample.
Stated Advantages
The device can be cleaned and reused repeatedly without undue concern over impurities or damage to the fumed silica.
The seamless construction eliminates light path losses associated with seams, maximizing measurement accuracy.
Mechanical resilience and reliability are enhanced, allowing use in harsh or industrial environments prone to vibration.
The liner provides structural reinforcement to the fragile monolithic fumed silica, ensuring long lifespan.
Reflectivity exceeds 99.8% in the visible spectral range and remains high in UV and near-infrared ranges.
Uniform light distribution within the cavity results in more accurate and sensitive optical measurements.
Documented Applications
Optical spectroscopy applications such as iCAS (integrated cavity absorption spectroscopy), iCRD (integrating cavity ring-down spectroscopy), iCEFS (integrating cavity enhanced fluorescence spectroscopy), and iCERS (integrating cavity enhanced Raman spectroscopy).
Routine optical photometry and metrology, including radiance, emission spectral energy, and power measurements.
Quality control or rating of materials, such as reflective coatings or LEDs, by measuring optical characteristics.
Analysis of purity, characteristics, or identity confirmation of substances like amino acids or other powders, liquids, gases, or granular materials.
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