SBIR-STTR Award

Among different terahertz instruments, terahertz time-domain spectroscopy (THz-TDS) systems are the most effective tools for realizing terahertz imaging and sensing systems. Although THz-TDS systems offer many unique functionalities, their practical utilization for solving real-world problems has been extremely limited because of the absence of high-performance, multi-pixel detectors that can offer both high data quality and fast data acquisition over a broad frequency range. Existing THz-TDS systems consist of single pixel detectors and require two-dimensional scanning of either the scanned object or the detector. This prevents many potential applications of THz-TDS systems. Developing a broadband terahertz focal plane (THz-FPA) can address this problem; however, realization of a THz-FPA for THz-TDS systems has not been possible yet due to the design restrictions of conventional photoconductive terahertz detectors. To address the limitations of conventional photoconductive detectors and realize the worlds first broadband THz-FPA, Lookin, Inc. proposes the use of a novel terahertz detector design based on plasmonic nanoantennas, which are designed to maximize the interaction between the optical pump and terahertz beams. Our team has recently presented a single-pixel demonstration of this unique detector and achieved record-high sensitivity levels over a very broad terahertz frequency range. In addition, the detector structure is easily scalable to large areas without suffering from increased parasitics. This allows development of THz-FPAs with large filling factors, which utilize the majority of the incident optical pump photons and capture most of the incident terahertz radiation while providing a much easier optical/terahertz alignment compared to conventional photoconductive detectors. To further explore this technology and develop THz-FPAs consisting of more than 1 kilo-pixels, Lookin, Inc. plans to first build a 64-pixel prototype during the Phase I project. Our company will collaborate with Terahertz Electronics Laboratory at UCLA. The UCLA subcontractors extensive expertise in plasmonics and terahertz optoelectronics will help us boost the bandwidth and sensitivity of the terahertz detectors based on plasmonic nanoantennas. Our team will conduct critical feasibility studies that will clearly determine the possible achievable frame rate, signal-to-noise ratio, and detection bandwidth. Our initial calculations show that the 1 kilo-pixel THz-FPA can operate at video frame rates and each pixel of the proposed THz-FPA can offer high SNR levels (>50 dB) with a broad terahertz detection bandwidth (1-3 THz). In addition, the team will conduct research on novel nanofabrication techniques, such as nanoimprinting, for the realization of large pixel-count THz-FPAs with much lower cost and higher throughput. The company will also develop an image reconstruction software to capture real-time 3D images with the developed THz-FPAs.

Benefit:
As Lookin, Inc., we aim to be the pioneer of the transition of terahertz technology from research laboratories to industry and the consumer market. During our proposed project, we will develop a high-performance broadband terahertz focal plane array (THz-FPA) that can be used for multi-pixel terahertz time-domain spectroscopy (THz-TDS). The terahertz band lies between the radio and infrared frequencies in the electromagnetic spectrum. Waves in this frequency band offer many unique imaging and spectroscopy functionalities for quality inspection applications. For example, many chemicals have unique spectral signatures at terahertz frequencies, which makes terahertz spectroscopy a powerful means for chemical identification and material characterization. Terahertz waves offer higher-resolution imaging than radio frequencies; on the other hand, they can penetrate through many opaque materials at infrared frequencies. This makes terahertz imaging a potential alternative for ultrasound imaging and X-ray tomography. In addition, compared to ultrasound imaging, terahertz imaging does not require any coupler and, thus, enable a non-contact evaluation. Terahertz waves also do not pose any health hazard unlike X-rays. Although these unique functionalities of terahertz waves have been known for a long time, high-performance terahertz scanners have not yet been fully industrialized to facilitate human life in most application settings. One of the main limitations that has prevented the wide utilization of terahertz scanners is the low performance of existing terahertz detectors. Our proposed THz-FPAs will provide the first multi-pixel solution for high-speed, high-sensitivity, and broadband terahertz imaging. They would not only be of interest to many industries for non-destructive quality control, but also for basic science research facilities. With the unprecedented performance of our terahertz products, we are confident that our terahertz scanner technology would be widely used in various industrial settings within five years. Our team also looks for potential killer applications of terahertz systems. THz-TDS systems have unique potentials to be used for various non-destructive inspection, chemical identification, material characterization, and biomedical imaging applications. Our company has so far targeted two specific applications of THz-TDS. One application focuses on detecting aflatoxins in food products. The other application focuses on non-destructive evaluation of battery and fuel cell electrodes during roll-to-roll manufacturing. Our team is also exploring new applications of THz-TDS for several DoD missions, such as battlespace target assessment, surveillance in low-visibility conditions, and nondestructive evaluation of defects and corrosion in ship, aircraft, and vehicle components. For all of these applications, the proposed THz-FPA would enable high-throughput and accurate operation.

Keywords:
terahertz time-domain spectroscopy, terahertz time-domain spectroscopy, plasmonic nanoantenna, focal-plane arrays, : Terahertz detector

Terahertz time-domain spectroscopy (THz-TDS) and imaging systems offer unique functionalities for material characterization, non-destructive quality control (QC), chemical detection, and biomedical imaging. However, practical utilization of these systems for solving real-world problems has been limited because of the absence of high-performance, multi-pixel terahertz detectors that can offer both high data quality and fast data acquisition over a broad frequency range. Existing THz-TDS systems consist of single pixel detectors and require two-dimensional scanning of either the scanned object or the detector, which is not practical for many potential applications of these systems. Developing a broadband terahertz focal plane array (THz-FPA) can address this problem; however, realization of a THz-FPA for THz-TDS systems has not been possible yet due to the design restrictions of conventional photoconductive terahertz detectors. The plasmonic nanoantenna technology developed by the co-founders of Lookin, Inc. provides a unique solution for developing THz-FPAs. As proved by feasibility tests during the Phase I program, terahertz detectors based on plasmonic nanoantennas offer record-high sensitivity levels and, through their scalable architecture, they can be fabricated over large areas without introducing bandwidth-limiting parasitics. Encouraged by the results of the Phase I program, during which a 64-pixel THz-FPA prototype was successfully developed, Lookin, Inc. intends to further extend this advanced terahertz detector technology during the Phase II Base program to develop THz-FPAs consisting of 256256 pixels. The THz-FPAs will be designed to offer large field-of-view (FOV) and image acquisition rates up to 10 Hz. In addition to the THz-FPA development, Lookin, Inc. plans to build a multi-pixel terahertz imaging platform through a custom-made compact, fiber-coupled, and high-power femtosecond laser. The team also plans to design various terahertz lenses to offer different functionalities, such as adjustable FOV and line scanning with the THz-FPA and multi-pixel imaging system. After the development of the proposed large-pixel-count THz-FPAs and high-speed terahertz imaging systems, Lookin, Inc. plans to use the multi-pixel terahertz imaging systems as a transformative solution for a currently unmet need in lithium-ion battery (LIB) manufacturing, in-line QC of LIB electrodes. In-line QC of LIB electrodes can improve manufacturing capability to deliver high power batteries with better shelf life, increased safety, lower cost, and decreased production lead-time. During the Phase II Option program, Lookin, Inc. plans to modify the high-speed terahertz imaging systems to be installed in LIB manufacturing facilities for high throughput scanning of LIB electrodes and conduct extensive validation studies in collaboration with battery manufacturers.

Benefit:
As Lookin, Inc., we aim to be the pioneer of the transition of terahertz technology from research laboratories to industry and the consumer market. During our proposed project, we will develop a high-performance broadband terahertz focal plane array (THz-FPA) that can be used for multi-pixel terahertz time-domain spectroscopy and imaging. Realization of large-pixel-count THz-FPAs would be a huge milestone for terahertz science and technology and would transform terahertz time-domain imaging systems from a research tool to an industrial equipment that can be used in various real-world imaging and sensing applications. Creation of multi-pixel terahertz time-domain imaging systems with large field-of-view and high-speed frame rate will make terahertz technology a very useful instrument for quality control applications that require high throughput. One of these applications that no other technology could answer the need in industry is in-line quality control (QC) of lithium-ion battery (LIB) electrodes. LIBs offer many advantages for electronic vehicles, warfighters, unmanned aerial vehicles, unmanned underwater vehicles, naval ships, aircrafts, and military vehicles due to their increased energy, lower weight, and longer cycle life compared to other battery solutions. LIBs are still expensive and there is a growing concern of battery safety and quality as the number of LIB-powered systems increases, mainly due to the defects that are introduced during the roll-to-roll manufacturing of LIB electrodes. Previous studies have investigated the correlation between defects introduced during LIB electrode manufacturing and LIB electrochemical performance. The findings indicate a significant alteration in the electrochemical performance, diminishing the performance by aggravating cycle efficiency, lowering discharge capacity, and shortening the life span of LIBs. Current scrap rate in LIB electrode manufacturing is approximately 10%, causing a significant loss for LIB manufacturers. Therefore, an efficient quality control (QC) tool for early detection of the electrode defects during the LIB manufacturing is needed. Terahertz waves offer unique functionalities for QC of battery electrodes. They can penetrate through electrode coatings and provide 3D images of the battery electrodes. Terahertz waves do not pose a health hazard. Although these unique functionalities have been known for a long time, the low sensitivity and scanning speed of existing terahertz scanners have prevented their deployment. By enabling high-throughput and high-sensitivity detection of defects in battery electrodes at early stages of manufacturing through Lookins terahertz imaging systems based on THz-FPAs, our proposed instrument would be an indispensable tool for LIB manufacturers and would help them significantly to reduce their fabrication cost by reducing the scrap rates of electrode coatings and increase the LIB availability and safety.

Keywords:
focal-plane arrays, Terahertz detector, plasmonic nanoantenna, quality control., Lithium-Ion Battery, terahertz time-domain spectroscopy, Terahertz imaging, terahertz scanner