Use THz TDS to detect materials

Introduction and Application

Terahertz Time Domain Spectroscopy (THz TDS) is a technique used to characterize materials and analyze their characteristics in the terahertz frequency range. This frequency range is particularly noteworthy because many materials related to industry are semi transparent and/or have distinct spectral features, allowing for their identification. The working principle of terahertz time-domain spectroscopy technology is to emit short pulses of terahertz radiation and measure the time required for the pulses to pass through the sample and return. By analyzing the characteristics of the returned pulse, valuable information about the composition, structure, and dynamic changes of the sample can be obtained.

In the automotive industry, terahertz time-domain spectroscopy technology is used for non-contact measurement of automotive paint thickness. These measurements are crucial for ensuring quality control and detecting potential issues such as coating unevenness, non-uniformity, and delamination. Similarly, terahertz time-domain spectroscopy technology can be used to inspect functional coatings on aircraft, such as anti-corrosion coatings or thermal barrier coatings. But it is also useful in other fields: it can be used to study the optical and electronic properties of various materials, including semiconductors, polymers, ceramics, and composite materials. It helps to determine the refractive index, conductivity, and other important parameters of these materials.

main challenges

One of the key challenges in achieving high-performance terahertz time-domain spectroscopy (THz TDS) systems is optical delay scanning. Traditionally, people have used mechanical delay tables, but they often require a trade-off between scanning speed and scanning range. Making these mechanical platforms move quickly over long distances is a major challenge.

Terahertz time-domain spectroscopy applications often involve the detection of thick optical systems, where there is significant optical delay between reflected light. In other cases, sufficient spectral resolution is required to distinguish the desired spectral features. Fast optical delay scanning plays a crucial role in meeting both of these requirements.

With the help of fast optical delay scanning, terahertz time-domain spectroscopy systems can be applied to fast point scanning applications and factories that require the detection of large surface areas in a short period of time. In these scenarios, mechanical optical delay scanning is often difficult to achieve high-throughput performance.

Our Advantages

The single cavity dual comb laser provides a remarkable solution for achieving fast and accurate optical delay scanning, eliminating the limitations of mechanical delay stages. By using K2 laser, the performance and versatility of THz TDS system can be significantly improved.

Diagram of optical delay scanning parameters in THz TDS system driven by a single cavity dual comb laser. The optical delay scan with a length of 1/frep is repeated every 1/Δ frep, given by the detuning Δ frep of two comb like repetition frequencies frep.

The common noise suppression in single cavity dual comb lasers ensures a precision of over 10 femtoseconds on the time axis. This precise control of pulse delay enables accurate measurement of high-resolution spectra and material properties. The gigahertz repetition rate of K2 laser can achieve nanosecond level optical delay scanning. This is highly compatible with applications that require long latency scanning. But it avoids wasting measurement time in areas without signals, as is typical of low repetition rate dual laser systems.

In addition, the short pulse (<100fs) characteristics of single cavity dual comb lasers contribute to the wide spectral coverage of THz TDS. The frequency comb generated by K2 laser can be converted into broadband THz pulses with the help of high-efficiency photoconductive antenna (PCA), providing detailed spectral information within a wide bandwidth. The comprehensive characterization ability at THz frequency can identify specific molecular and structural features of materials.

Advantages of K2 Photonics for Testing Materials

• Fast scanning speed

The K2-1000 laser can be used to scan a significant optical delay range of 1 ns at speeds exceeding 10 kHz.

• High precision

The single cavity structure and common noise suppression ensure femtosecond level accuracy on the time axis throughout the entire optical delay scanning process.

• Small size

No mechanical delay lines are required, greatly simplifying the implementation of high-performance THz TDS settings.

• High sensitivity

Single cavity dual comb lasers can provide optical delay scanning over a long delay range, making them ideal for high-resolution measurement or inspection of thick and complex samples.