T-SWEEPER

Fast optoelectronic FMCW terahertz system
Rapidly swept lasers offer an alternative to established distributed feedback diodes for applications in which measurement speed is more relevant than frequency resolution. One implementation combines a fast, widely tunable laser and a static source into a “frequency-modulated continuous-wave” (FMCW) terahertz system. Equipped with state-of-the-art photomixers, the system acquires spectra with more than 2 THz bandwidth in less than 15 ms. Akin to pulsed systems, trace averaging reduces the noise floor and consequently, broadens the useable frequency range: With 2 minutes of averaging, the bandwidth increases to more than 3.5 THz. Users can conveniently set the number of averages in the control software, and therefore optimize system performance with respect to either measurement speed, or dynamic range and bandwidth.
An important difference to pulsed systems: The fast FMCW unit utilizes an InGaAs-based p-i-n photodiode as terahertz emitter, and consequently, the spectrum peaks at approximately 0.1 THz – significantly lower than the 1.0 THz peak of pulsed spectra. Owing to the lower peak frequency, the signals generated by the fast FMCW unit have a higher penetration depth in many polymers, a property that makes the system particularly attractive for thickness measurements on thick samples.

Your Benefits

Faster processes, higher throughput
Go fast, with up to 70 traces per second while still covering a 2 THz bandwidth. Ideal for fast inline inspection, with the flexibility to trade speed for bandwidth and dynamic range via simple averaging in software. The measurement rate up to 500 Hz also enables real-time or near-real-time measurements. 
Non-destructive thickness measurements that were previously difficult or impossible
Because the FMCW spectrum peaks around 0.1 THz, the system achieves deeper penetration in strongly scattering materials, e.g. certain polymers or ceramics. 
Scalable and robust industrial system
The no-moving-parts design ensures robustness and long-term stability, while the FMCW concept allows true multi-channel scalability, demonstrated by the world’s first 8-channel optoelectronic FMCW THz system (T-SWEEPER x8). Ideal for large-area inspection, parallel measurements, and advanced concepts like synthetic aperture radar. 
Virtually unlimited fiber length
Because the lasers operate in continuous-wave (CW) mode rather than pulsed mode, the system allows for virtually unlimited fiber umbilical lengths between the main unit and the THz measurement heads. Ideal for large industrial setups, confined environments, or applications requiring long-distance remote sensing.

Applications

Plastic inspection
TOPTICA TeraFlash smart - Ultrafast time-domain terahertz platform 0.1 to 4 THz (in < 1 s)
Paint and coating layers
Synthetic aperture radar

Options

GaAs and InGaAs photomixers
Both top quality material systems offer an excellent bandwidth and dynamic range. The modules come equipped with a Silicon lens and SM/PM fiber pigtail.
Scale to 8 channels
Each of the eight channels can measure and process up to 500 thickness values per second. Available as a prototype by Fraunhofer HHI and Fraunhofer ITWM in collaboration with TOPTICA. Possible applications include multi-channel layer thickness measurements, e.g. on large structures, but also more advanced experimental concepts like synthetic aperture radar.
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