SBIR-STTR Award

The NASA Constellation program has a need to non-destructively test (NDT) non-metallic materials (foams, Shuttle Tile, Avcoat, etc) for defects such as delaminations and voids. While imaging systems at terahertz frequencies (0.3 to 3 THz) have been demonstrated for 2D imaging of similar materials, they have not yet demonstrate full 3D volumetric imaging. To meet this need, LongWave Photonics proposes to use high-power, low-frequency terahertz quantum cascade lasers (QCLs) developed at MIT, to demonstrate 3D imaging using Laser Triangulation. By using high-power QCL sources, large signal to noise ratios (SNRs) are attainable, resulting in resolution of subtle defects at fast scan speeds. The shorter wavelengths emitted by QCLs, 60 to 250 µm, allow high lateral and depth resolution. The feasibility of a second system based on Swept-Source Optical Coherence Tomography will also be explored using a recently developed tunable THz QCL from MIT. In addition to the benefits of high SNR, this technique allows sub-wavelength depth resolution. The current generation of QCLs are compatible with a cooling package that is <1 Kg, with <100 W power consumption. Phase II work will package a second generation of QCLs in a compact system to meet NASA's portable 3D NDT needs.

Potential NASA Commercial Applications:
(Limit 1500 characters, approximately 150 words) The proposed Terahertz QCL based 3D Imaging system will be valuable in characterizing the voids and delaminations in materials used in the Constellation program (e.g. urethane based foams, silica based composites, etc). The high depth resolution enabled by this system will also allow measurement of thin non-conductive polymer layers, such as paints and compositions to verify thicknesses and integrity. Further application include inspection for corrosion damage under paint layers or foams.

Potential NON-NASA Commercial Applications:
(Limit 1500 characters, approximately 150 words) Pharmaceutical applications for this technology include in-process monitoring of thicknesses of polymer coatings in controlled release tablets. Numerous defects in the thin coatings can occur during processing affecting the performance of the tablet, leading drug complications and drug recalls. The use of QCL based 3D imaging technology could improve the uniformity in a batch tablet coating process. In the automotive and aerospace industry spray application of paint is both inefficient and environmentally unfriendly. In situ monitoring of sprayed paint thicknesses would allow reduced paint usage and reduced emissions of volatile organic compounds (VOCs). NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.

Technology Taxonomy Mapping:
Ablatives Ceramics Composites In-situ Resource Utilization Microwave/Submillimeter Optical Optical & Photonic Materials Semi-Conductors/Solid State Device Materials Testing Requirements and Architectures Thermal Insulating Materials

LongWave Photonics proposes a terahertz quantum-cascade laser based swept-source optical coherence tomography (THz SS-OCT) system for single-sided, 3D, nondestructive evaluation (NDE) of non-conductive materials. The THz SS-OCT system uses a frequency tunable QCL array to generate an interferometric signal between a reference mirror, and a sample. An algorithm is used to transform this signal into depth information of the interfaces within the sample. Phase I demonstrated the feasibility of measuring the interfaces of a dielectric on metal sample. In Phase II, we propose to demonstrate a complete scanning system for 3D imaging by upgrading the optics and mechanics. Improvements in the power levels and frequency bandwidth of the QCL source are expected to greatly improve the depth resolution and signal to noise ratio of the system. The milliwatt power levels of the QCL are expected to result in fast scan speeds. Operation of the SS-OCT system is expected to be relatively simple as the QCL is an electrically pumped, solid state source of terahertz radiation, capable of operation in a compact, high reliability crycooler as demonstrated in Phase I.

Potential NASA Commercial Applications:
(Limit 1500 characters, approximately 150 words) The proposed THz SS-OCT system will be useful for characterizing the voids and delaminations in materials used in space flight (e.g. urethane based foams, silica based materials, composites, etc). The high depth resolution enabled by this system will also allow measurement of thin non-conductive polymer layers, such as paints and compositions to verify thicknesses and integrity. Further application include inspection for corrosion damage under paint layers or foams.



Potential NON-NASA Commercial Applications:
:
(Limit 1500 characters, approximately 150 words) Pharmaceutical applications for this technology include in-process monitoring of thicknesses of polymer coatings in controlledrelease tablets. Numerous defects in the thin coatings can occur during processing affecting the performance of the tablet, leadingdrug complications and drug recalls. The use of QCL based 3D imaging technology could improve the uniformity in a batch tabletcoating process. In the automotive and aerospace industry spray application of paint is both inefficient and environmentallyunfriendly. In situ monitoring of sprayed paint thicknesses would allow reduced paint usage and reduced emissions of volatile organiccompounds (VOCs).

Technology Taxonomy Mapping:
(NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.) Composites Launch and Flight Vehicle Optical & Photonic Materials Photonics Portable Data Acquisition or Analysis Tools Semi-Conductors/Solid State Device Materials Testing Facilities