Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Photoacoustic Photon Meter And Process For Measuring Photon Fluence

Patent Number: 11,193,914


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.

patent description

This invention pertains a concept of a carbon nanotube (CNT)-based integrated sensor which can measure spatial and spectral photon fluence (energy per unit area or volume in the spatial or spectral domain), temperature, and pressure in turbid media and can evaluate performance of photoacoustic imaging devices.

In a light-diffusing and/or light-absorbing material, accurate local photon fluence measurement with varied wavelength is challenging because the spatial distribution of light-scattering and/or light-absorbing entities in the material are not uniform and the energy and/or propagating direction and depth of the traveling photons is not spatially homogeneous and are strongly wavelength dependent.

CNTs, either in a randomly distributed or a systematically aligned or ordered form, effectively absorb photons at a broad range of wavelengths and convert their energies to thermal and/or mechanical energy which can be measured by the changes in electrical conductivity and/or in ultrasound pressure.

A broad range of applications is expected. The sensors will enable measurements of local photon fluence for quantitative optical imaging of biological tissues, local temperature fluctuations in turbid materials during photothermal therapy which kills tumor cells by a light illumination. The sensor will also be instrumental in calibrating measurement results by photonic and optoeletronic devices when they are used in a turbid environment. The sensors can also be used as resolution and photon fluence measurement targets. The CNT sensor has a small variation in the absorption efficiency across a broad wavelength range, therefore it can be used as a calibration tool for quantitative multispectral measurements in a variety of optical imaging applications including optical microscopy, optical coherence tomography, photoacoustic microscopy and computed tomography, and multispectral imaging technologies in addition to others. Other non-imaging applications include calibration of ultrasound transducers and thermometers.

Created September 12, 2022, Updated February 27, 2024