Features

• Wide spectral range up to  3.5 THz (116 cm^-1)

• Excellent spectral resolution better than 5 GHz (0.17 cm^-1)

• High power S/N ratio >10⁶:1 at 0.4 THz

• Real-time data acquisition  up to 10 spectra/s

• “No bearing” design of fast delay line – virtually unlimited lifetime

• Transmission and reflection modes

• High spatial resolution THz imaging

• Complete PC control

• User-friendly software for transmission or/and  absorption measurements, imaging

Applications

• THz transmission, reflection spectroscopy

• Optical pump – THz probe spectroscopy

• Chemical material characterization

• Medical and biological nondestructive research

• Semiconductor wafer inspection

• Polymeric compounding

• Explosives detection

• Your application is welcome…

Real-time Terahertz Spectrometer offered by EKSPLA is a powerful   tool for investigative applications of pulsed terahertz waves. With   simple and robust design, it is easy-to-use and adaptable to individual   requirements.The unique design of microstrip photoconductive antenna   fabricated on low-temperature grown GaAs  (LT-GaAs) substrate ensures   broad-band spectral coverage and high dynamic range.The system is   designed with two delay lines: fast and slow. Fast scan line allows real   time data acquisition with 10 spectra/sec. speed. Average of collected   spectra can increase signal to noise ratio to 10⁶:1 at 0.4.   Additional slow delay line extends scan window from  110 ps to 220 ps;   as a result system obtains excellent spectral resolution of &Delta;f < 5   GHz. The fast scan line is designed without bearings and uses a   magnetically coupled drive which makes it extremely reliable and   significantly extends the lifetime. Our T-SPEC series spectrometer is   the perfect choice for broadband THz imaging. It allows scan of up to   25&times;25 mm sample with spatial resolution of approx. 1 mm. Measurements   contain information about the target, revealing both structural and   spectroscopic information.

Basic operation principles of THz Time Domain Spectroscopy

The terahertz (THz) and sub-THz frequency region (100 GHz &ndash; 10   THz) of the electromagnetic spectrum bridges the gap between the   microwaves and infrared. THz waves penetrate dielectric materials like   paper or plastic, are reflected by materials with free electrons like   metals and are absorbed by molecules with certain vibration levels   within the terahertz band. Terahertz absorption or refection   spectroscopy, imaging of biological and other objects, THz tomography   and optical pump-THz probe spectroscopy are all hot topics in recent   scientific conferences with possible applications in semiconductor,   medical and security industries. The typical THz Time Domain   Spectroscopy (THz-TDS) setup is shown in Fig. 1.

Fig.1. Example of THz-TDS experimental setup

Sub-picosecond pulses of THz radiation are detected after   propagation through a sample and an identical length of a free space. A   comparison of the Fourier transforms of these pulse shapes gives the   absorption spectra of the sample under investigation.

Fig.2. typical performance of T-SPEC series real-time THz   spectrometer (measured in ambient atmosphere) - THz pulse waveform and   Fourier-transform spectra. (Click on the picture to enlarge)

Examples of THz spectra

Fig.3. Absorption coefficient measurements of RDX and * in ambient atmosphere. (Click on the image to enlarge).

THz Components

The key components for any THz system are THz radiation emitter and detector. EKSPLA THz emitter and detector features a microstrip photoconductive antenna fabricated on   low-temperature grown GaAs  (LT-GaAs) substrate. THz radiation is   collected and collimated by integrated hemispherical high-resistivity   silicon lens, mounted on X-Y stage. Performance of photoconductive   antenna, depends on carriers mobility and their trapping time in   semiconductor layers. LT-GaAs is one of the best materials for THz   applications because of its high carrier mobility, fast carrier capture   time, high breakdown voltage and high resistivity. LT-GaAs growth   technology allows controlling the photoexcited carrier lifetime within a   very wide region: from less than 100 fs to 100 ps. Photoconductor   antenna geometry, silicon lens parameters, as well as the properties of   LT-GaAs epitaxial layers were optimized for highest THz radiation output   efficiency while preserving optimal bandwidth.

As  a result, the   typical emitted THz radiation power exceeds several &micro;W when pumped by   mode-locked ultrafast laser with 30 mW output power and 100 fs pulse   duration. FWHM bandwidth of detection system exceeds 700 GHz, with   usable spectral range of 0.1&ndash;3.5 THz. Versions for different types of   pump lasers are available.

Fig. 4. THz radiation emitter and detector

Software

Stand-alone software   is supplied with the device. It has integrated tools for complete   system control, transmission/absorption spectra analysis, 2D imaging   data visualization and spectral analysis by X, Y position. It also   allows real-time signal and spectra monitoring (useful for system   adjustment) as well as averaging up to 512 spectra to increase dynamic   range. Raw data can be exported to file for further analysis.

Fig. 5. Software main window (image of blade (size 97 x 97 pixels) acquired in imaging mode at 1 THz  frequency

Build Your own THz spectrometer
As a totally flexible and cost effective solution, Ekspla offers the   Terahertz Spectroscopy Kit. Four standard confgurations are available,   optimized for transmission, reflection,imaging or pump-probe   measurement. All can be easily interchanged and modified. Any other   optional configuration can be ordered initially or as a future upgrade.

Basic THz Spectroscopy Kit includes:

• photoconductive antenna,

• THz emitter and detector,

• pump laser beam guiding optics,

• motorized slow delay line with controller,

• THz beam guiding mirrors,

• sample holder,

• lock-in amplifier,

• Labview based software for data acquisition.

Optionally:

• femtosecond laser,

• purging box, removes water absorption lines

• personal computer.

Requests for custom-made version are welcome.