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TOPAG Lasertechnik GmbH
Nieder-Ramstädter Str. 247
64285 Darmstadt
Telefon: +49 6151 4259 78
Telefax: +49 6151 4259 88 
E- mail: info [at] topag.de 

THz emitters and detectors

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THz emitters and detectors

thz-emitters-and-detectors

These components consist of a microstrip photoconductive antenna on LT-GaAs or GaBiAs substrate. Antenna structures are optimized for best combination of output efficiency and bandwidth. Different models for pumping at 800nm as well as at 1060nm are available. Configuration includes Si focusing lens with x-y-micrometer adjustments and SMA connector for bias voltage and lock-in amplifier input.

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Bezeichnungen der Tabs

  • Description
  • Specifikations
  • Pictures
Tab 1

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

THz emitter and 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. Photoconductive antenna geometry, as well as the properties of photoconductor epitaxial layers are optimized for highest THz radiation output efficiency, while preserving optimal bandwidth. As a result, typical emitted THz radiation power exceeds 10 μW, when pumped by laser with 30 mW output power and 150 fs pulse duration. FWHM bandwidth of detection system exceeds 700 GHz with usable spectral range of 0.1–4 THz. THz emitter or detector is illuminated by laser beam from panel side. Laser beams must be focused between two electrodes (Fig. 1).

Bild 1
Emitter and Detector-fiber 4 

Fig. 1: Microstip antena drawings: (a) emitter, (b) detector.

The gap between metallic contacts is similar to laser spot diameter in detector case and larger – in emitter case. THz radiation is collected by integrated lens, manufactured from high-density silicon, mounted on X-Y stage. EKSPLA offers two standard types of these lenses: for collimated or diverging THz beam output. In second case PCA is placed in aplanatic point of silicon lens, which reduces THz beam aberrations. Adjustment screws are used for Si lens positioning onto PCA center. SMA sockets on back side of the housing are used for connecting DC or AC bias to THz emitter and lock-in amplifier input to THz detector. Any of three M6 holes can be used for THz emitter mounting on optical table.

Tab 2
 EmittersDetectors
Model EMT-08 EMT-10 DET-08 DET-10
Photoconductive antenna
Photoconductive material LT-GaAs GaBiAs LT-GaAs GaBiAs
Dimensions of the wafer 5 x 1.5 mm
Thickness 600 µm
Antenna type strip line dipole
Bias voltage 50 V max, 40 V typical -
Central THz frequency ~ 0.5 THz -
Detected THz bandwidth - > 4 THz
Integrated focusing lens
Material HRFZ-silicon
Geometrical form hyper-hemi-sphere
THz beam output collimated or diverging -
X-Y adjustable stage range ± 3 mm
Pump beam parameters
Excitation wavelength 800±40 nm 1060±40 nm 800±40 nm 1060±40 nm
Average power 1) < 50mW < 30mW < 50mW < 30mW
Pulse duration < 150 fs
Pulse repetition rate 20-100 MHz
Beam profile near to Gaussian
Beam diameter 2) ~ 2 mm

¹⁾ Subject to laser pulse duration, repetition rate and beam size at the surface of wafer

²⁾ Recommended value, if used with EKSPLA THz emitter/detector mount of THz spectroscopy kit

Tab 3

Tab 3 Inhalt

Tab 4

Tab 4 Inhalt

Tab 5
Bild 1
 thz-emitters-and-detectors4
Beschreibung 2
THz emitter and detector 
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Emitter and Detector-fiber 4 
Beschreibung 2
THz Microstip antena drawings: (a) emitter, (b) detector 
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thz-emitters-and-detectors 3 
Beschreibung 3
THz emitter and detector crossection 
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thz-emitters-and-detectors 4 
Beschreibung 4
THz emitter/detector housing (model with collimated THz output) 
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thz-emitters-and-detectors 5 
Beschreibung 5
THz emitter/detector housing (model with diverging THz output) 
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T-SPEC 3 
Beschreibung 6
The measured THz signal. Average optical power incident to the emitter was 20 mW and to the detector – 26 mW. Laser: Yb:KGW, wavelength – 1030 nm, duration – 70 fs, pulse repetition rate – 75 MHz. 
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T-SPEC 4 
Beschreibung 7
The measured THz spectrum. Average optical power incident to the emitter was 20 mW and to the detector – 26 mW. Laser: Yb:KGW, wavelength – 1030 nm, duration – 70 fs, pulse repetition rate – 75 MHz. 
Bild 8
 
Beschreibung 8
 
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Beschreibung 9
 
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Beschreibung 10
 
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