A. What is Terahertz? |
Terahertz (THz) refers to the electromagnetic spectrum that lies between microwave and infrared light, spanning frequencies from approximately 0.1 to 10 THz. A terahertz wave has a wavelength ranging between 30 micrometres and 3 millimetres, characterized by its unique ability to penetrate various materials without causing damage or harm. This spectral region has garnered immense attention due to its combination of non-invasive properties and its ability to unveil hidden structural, chemical, and electronic information.
Terahertz radiation is a relatively underexplored part of the electromagnetic spectrum. It occupies the frequency range between radio waves and infrared light, often referred to as the “terahertz gap” due to historical challenges in generating and detecting THz waves efficiently. Advances in ultrafast optics and semiconductor technology, enabled the development of terahertz systems that are now critical tools in scientific research and industrial applications.
The versatility of terahertz radiation enables its application across a wide range of fields. Some key areas include:
· Scientific Research
Terahertz systems are extensively used in exploring material properties at the molecular and atomic scales. THz-TDS has been instrumental in studying carrier lifetimes in semiconductors, low-energy vibrations, and rotational transitions in molecules, as well as phonon-polariton dynamics in crystalline structures.
· Non-Destructive Testing
Industries use terahertz radiation for quality control and inspection. It allows precision measurement of thickness, absorption coefficients, refractive indices, and structural integrity in multilayer structures without harming the materials. This makes it ideal for inspecting composite panels, semiconductor wafers, or delicate polymer sheets.
· Biomedical Imaging
Terahertz radiation is gaining prominence in medical diagnostics due to its ability to penetrate biological tissues without causing harm or ionization. Researchers are exploring its potential for tumour detection, skin analysis, and other diagnostic applications.
· Security and Surveillance
Its ability to penetrate non-metallic materials and reflect off metallic objects makes terahertz radiation suitable for stand-off security screening, such as detecting hidden weapons or explosives without physical contact.
· Art and Cultural Heritage
Museums and conservators use terahertz waves for the non-invasive inspection of artworks, manuscripts, and historical artifacts. The radiation can reveal hidden layers or defects without altering the object.
B. Why Terahertz? |
The unique properties of terahertz radiation—its energy range, wavelength, and coherence—make it invaluable for applications requiring precision, safety, and non-destructive methodologies. Terahertz photons possess low energies, ensuring no harm to biological tissues or fragile materials, while their wavelengths allow penetration into dielectrics and imaging of internal structures. The coherent nature of terahertz detection further enables high signal-to-noise ratios, even in ambient conditions.
Furthermore, terahertz systems provide simultaneous access to temporal and spectral data, yielding comprehensive insights into material properties. They excel in applications where conventional probes—such as X-rays or microwaves—either lack resolution or pose risks to the subject being analysed.
C. Time Domain Spectrometry
Spectrometric measurements using Terahertz
Empower your R&D and manufacturing with our Terahertz solutions—delivering contactless precision, speed, and unmatched versatility for a non-invasive approach to measurement
Terahertz time-domain spectroscopy (THz-TDS) is a coherent, ultrafast technique that uses single-cycle THz pulses to probe matter with a combination of temporal and spectral resolution unrivalled in the electromagnetic spectrum. Because each pulse is only a few hundred femtoseconds wide, the system captures sub-picosecond events—revealing carrier lifetimes in semiconductors, phonon-polariton dynamics in crystals, and the early stages of chemical reactions that are invisible to slower probes. Fourier transformation of the time-trace delivers a broadband spectrum that routinely spans 0.1 – 6 THz (and, with optimized emitters, well beyond), giving simultaneous access to low-energy molecular vibrations, rotational transitions, and intra-band electronic processes.
Unlike conventional frequency-domain systems, THz-TDS measures both the amplitude and the phase of the transmitted or reflected field. From a single scan one can retrieve the complex refractive index, absorption coefficient, dielectric function, and even thickness of multilayer structures. The coherent detection further suppresses thermal background, allowing high signal-to-noise ratios at room temperature and below.
The technique is inherently non-destructive: THz photons have energies in the millielectron-volt range, low enough to leave delicate biological tissues, polymers, artworks, or semiconductor wafers unharmed. At the same time, their millimetre-scale wavelengths penetrate most dielectrics while reflecting off metals and water, enabling tomographic imaging, hidden-defect inspection, and stand-off security screening. Adjustable optical delay lines let the same setup examine micron-thick films under a microscope objective or metre-scale composite panels on a factory floor, simply by changing the beam geometry.
TeraLumen Solutions has mastered the art of building and customizing THz controllers for your unique applications. No matter the purpose of your measurements—whether for R&D, material property estimation, non-destructive testing, or even biomedical imaging—TeraLumen can provide a solution that is both fast and precise.
D. Differentiating Through-Transmission and Reflection Modes in THz TDS Setup
Terahertz Time Domain Spectroscopy (THz-TDS) setups can operate in two fundamental modes: through-transmission and reflection. These modes serve distinct purposes and are optimized for different types of applications.
· Through-Transmission Mode
In through-transmission mode, terahertz pulses pass through the sample, allowing the system to measure the transmitted field. This mode is particularly effective for characterizing materials that allow terahertz waves to penetrate, such as polymers, biological tissues, and most dielectrics. By analyzing the transmitted amplitude and phase, this mode provides crucial insights into the sample’s refractive index, absorption coefficient, and dielectric function. It is particularly useful for identifying compositional variations, and studying low-energy molecular vibrations. Through-transmission setups excel in applications requiring high sensitivity to internal structure, such as semiconductor wafer analysis or thin-film characterization.
· Reflection Mode
Reflection mode, on the other hand, measures terahertz waves reflected off the sample’s surface. This mode is ideal for materials that are reflective or opaque to terahertz radiation, such as metals, water, and some composites. By examining the reflected field, this mode reveals surface properties, boundary conditions, and depth-resolved features when used in a tomographic configuration. Reflection setups are indispensable in applications where surface integrity and defect detection are critical, such as inspecting composite panels, artwork restoration, or security screening.
The key differences between the two modes are
- Signal Source: Through-transmission relies on detecting transmitted terahertz waves, while reflection mode focuses on reflected waves.
- Application Scope: Transmission mode is suited for transparent or semi-transparent samples, whereas reflection mode targets opaque or reflective materials.
- Measurement Focus: Transmission mode excels in bulk property characterization, while reflection mode specializes in surface and interface analysis.
The choice between these modes depends on the material properties, the desired measurement outcomes, and the complexities of the application. Both modes leverage the unique capabilities of THz-TDS to provide non-invasive, high-resolution insights into the physical and chemical properties of a wide range of samples.
E. Why TeraLumen? |
At TeraLumen Solutions, we don’t just build terahertz systems—we redefine precision, versatility, and performance for industries worldwide. What sets us apart is our unparalleled expertise in crafting state-of-the-art terahertz controllers tailored to meet the most intricate demands of your application. Whether it’s cutting-edge R&D, material property analysis, non-invasive testing, or biomedical imaging, our solutions deliver unmatched speed, accuracy, and reliability.
Our team comprises leading innovators in terahertz technology, combining deep scientific knowledge with years of hands-on experience in system design and deployment. We understand that no two projects are alike, and our commitment to customization ensures that each solution is perfectly aligned with your requirements. From portable setups to large-scale industrial systems, TeraLumen adapts to the specifics of your vision.
Why settle for the conventional when you can achieve results beyond ordinary? With terahertz systems capable of probing delicate objects without harm, revealing hidden defects, or capturing ultrafast phenomena, TeraLumen is uniquely positioned to empower your operations with the precision and insight they deserve. Partner with TeraLumen, and let’s unlock the true potential of terahertz technology—together.
D. Terahertz Applications
Terahertz time-domain spectroscopy (THz-TDS) offers an advanced approach to detecting defects in composite materials such as glass fiber-reinforced polymers (GFRP). Through its ability to penetrate non-conductive materials and provide high-resolution imaging, THz technology can accurately identify delamination, voids, and micro-cracks within the layered structure of these composites. Additionally, variations in material density or imperfections induced during manufacturing can be revealed through the precise analysis of refractive index changes and absorption coefficients. By leveraging the non-invasive nature of terahertz waves, defects can be detected without compromising the integrity of the material, making it an ideal solution for quality control in industries relying on composite technologies.
Paint Coating Thickness
Terahertz technology provides a precise and non-invasive method for determining paint coating thickness, enabling accurate measurements of layered structures in coatings. By utilizing terahertz waves, variations in refractive index and absorption coefficients can be analyzed to detect inconsistencies, ensuring uniform application and quality control. This technique is particularly valuable in automotive, aerospace, and construction industries, where maintaining coating integrity is critical for performance and aesthetics. Furthermore, THz methods can be applied in research environments to study coating properties or address challenges in manufacturing processes requiring consistent paint layers.
Rubber Thickness
Rubber, with its complex molecular structure and inherent flexibility, poses significant challenges for traditional non-destructive testing (NDT) methods. Terahertz technology, however, overcomes these hurdles by utilizing its ability to penetrate non-conductive materials and analyze their internal properties with remarkable precision. Through terahertz waves, variations in refractive indices and absorption coefficients can be meticulously examined, revealing inconsistencies such as thickness variations, voids, or density fluctuations within rubber components. This non-invasive approach ensures that the integrity and performance of the material remain uncompromised, making it an indispensable tool for industries where rubber plays a critical role, such as automotive, aerospace, and manufacturing.
Biomedical Applications
Terahertz technology offers a groundbreaking approach to cancer margin detection by exploiting its ability to differentiate between healthy and malignant tissue. Variations in tissue refractive indices and absorption properties, caused by cellular and structural differences, can be precisely analyzed using terahertz waves. This enables surgeons to identify cancer margins with unparalleled accuracy during procedures, ensuring complete removal of malignant tissue while preserving healthy structures. TeraLumen is actively engaged in an ongoing clinical trial to validate this revolutionary application, working closely with medical professionals to bring this life-saving technology closer to widespread adoption.