Free space Terahertz Detector
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 housingSpecifications
*Detector with integrated preamplifier could be provided.
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
** 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 holderOrdering 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