Free space Terahertz Detector

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Features

  • Based on LT-GaAs or GaBiAs photoconductive material
  • Optimized for wavelengths around 800 nm or 1060 nm
  • Wide spectral range and low noise
  • Sub-picosecond temporal resolution
  • Technical passport and test report included

Applications

  • Time-resolved broadband THz spectroscopy
  • Optical pump - THz probe spectroscopy
  • THz imaging

Principle of Operation

THz detector consists of a microstrip photoconductive antenna (PCA) fabricated on GaAs substrate. Depending on pump laser wavelength either low temperature grown GaAs (LT-GaAs) or GaBiAs is used as photoconductor. On its surface a coplanar Hertzian type dipole antenna structure is formed using AuGeNi metallization.

THz detector is illuminated by laser beam from panel side. Laser beams must be focused between two electrodes (Fig. 1). The gap between metallic contacts is similar to laser spot diameter. THz radiation is collected by integrated lens, manufactured from high-resistivity silicon (HRFZ-Si), mounted on X-Y stage (Fig. 2). Adjustment screws are used for Si lens positioning onto PCA center. SMA sockets on back side of the housing are used for connecting lock-in amplifier input (or TRS-16 THz registration system) to THz detector. Any of three M6 holes can be used for THz detector mounting on optical table (Fig. 3).

Fig 1. Microstrip antenna drawing

  

Fig 2. THz detector crossection


Fig 3. THz emitter/detector housing

Specifications


Detector Model DET-8 DET-10
Photoconductive antenna
Photoconductive material LT-GaAs GaBiAs
Dimensions of the wafer 5 x 1.5 mm
Thickness 600 µm
Antenna type dipole
Bias voltage ±12 V*
Central THz frequency ~0.5 THz
Detected THz bandwidth** up to 5 THz
Signal-to-noise ratio >60 dB @ 0.5 THz
Integrated focusing lens
Material HRFZ-silicon
Geometrical form hyper-hemi-sphere
X-Y adjustable stage range ±3 mm
Pump beam parameters
Excitation wavelength 800±40 nm 1060±40 nm
Average power <50 mW <20 mW
Pulse duration <150 fs
Pulse repetition rate 20-100 MHz
Beam profile near to Gaussian
Beam diameter ~2 mm

*Detector with integrated preamplifier could be provided.
** With 100 fs laser pulse duration

Fig 4. Typical spectra when used THz emitter and detector made from LT-GaAs

  

Fig 5. Typical spectra when used THz emitter and detector made from GaBiAs


Fig 6. THz detector mounted on standard optics holder


Fig 7. THz detector with integrated preamplifier mounted on standard optics holder

Ordering Information


Description Model Notes
THz detector for 800 nm wavelength DET-8 Includes Si lens and coaxial cable with BNC connector
THz detector for 1060 nm wavelength DET-10 Includes Si lens and coaxial cable with BNC connector
THz emitter/detector mounting stage MNT Includes pump beam focusing lens on XYZ stage
TMS-100M bias power supply TMS-100 30 - 70 V DC or square-wave output