Photoacoustic photon meter and process for measuring photon fluence

Inventors

Hwang, Jeeseong • Yung, Christopher • Briggman, Kimberly Ann • Lehman, John Henry

Assignees

United States Department of Commerce

Abstract

A photoacoustic photon meter includes: a photoacoustic generative array including carbon nanotubes disposed in a photoacoustic generating pattern, such that the carbon nanotubes: receive photons comprising optical energy, and produce thermal energy from the optical energy; and a superstratum including a thermally expandable elastomer on which the photoacoustic generative array is fixedly disposed in position on the superstratum to spatially conserve the photoacoustic generating pattern, and such that the superstratum: is optically transparent to the photons; receives the thermal energy from the photoacoustic generative array; expands and contracts in response to receipt of the thermal energy; and produces photoacoustic pressure waves in response to the expansion and contraction, the photoacoustic pressure waves including a photoacoustic intensity and photoacoustic frequency that are based upon an amount of optical pressure applied to the carbon nanotubes by the photons, a spatial photon fluence of the photons, or a spectral photon fluence of photons.

Core Innovation

The invention disclosed is a photoacoustic photon meter comprising a photoacoustic generative array made of a plurality of carbon nanotubes disposed in a specific photoacoustic generating pattern. These carbon nanotubes receive photons containing optical energy and convert that optical energy into thermal energy. The array is fixedly disposed on a superstratum comprising a thermally expandable elastomer that is optically transparent to the photons. The superstratum receives the thermal energy, expands and contracts in response, producing photoacoustic pressure waves comprising intensity and frequency that depend on the optical energy applied, the spatial photon fluence, or the spectral photon fluence.

The problem solved addresses the limitations of conventional devices that fail to accurately measure local photon fluence in light-diffusing or light-absorbing materials, especially when the spatial distribution of scattering or absorbing entities is non-uniform and wavelength-dependent. Conventional sensors such as photomultipliers or photodiodes have issues with unknown reflectance, wavelength-dependent responsivity, and challenges embedding in bulk materials.

The photoacoustic photon meter overcomes these limitations by utilizing carbon nanotubes with known absorption coefficients arranged in desired patterns, which convert light energy into heat and subsequently into measurable photoacoustic pressure. The superstratum elastomer expands and contracts with the received thermal energy to generate photoacoustic pressure waves. The invention also encompasses processes for measuring photon fluence and local temperature rise, correlating photoacoustic signals to photon fluence quantitatively, and configurations that enable calibration of photoacoustic devices and multispectral measurements.

Claims Coverage

The patent includes three independent claims covering the apparatus and processes related to the photoacoustic photon meter.

The independent claims cover the photoacoustic photon meter device comprising carbon nanotube arrays on a thermally expandable elastomer superstratum producing photoacoustic pressure waves corresponding to photon fluence, apparatus extensions involving photon propagation medium and transducers, and processes using the device to measure photon fluence and local temperature changes through electrical resistance measurements.

Stated Advantages

Documented Applications