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Features & Applications

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

Description

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).

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.

Specifications

	Emitters		Detectors
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

Subject to laser pulse duration, repetition rate and beam size at the surface of wafer
Recommended value, if used with EKSPLA THz emitter/detector mount of THz spectroscopy kit

Drawings & Performance

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

Fig. 2. THz emitter and detector crossection

Fig. 3a. THz emitter/detector housing (model with collimated THz output)

Fig. 3b. THz emitter/detector housing (model with diverging THz output)

Fig. 4. 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.

Fig. 5. 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.

Ordering information

Description	Model	Notes
THz emitter for 800 nm wavelength	EMT-8	Includes Si lens and coaxial cable with BNC connector
THz detector for 800 nm wavelength	DET-8	Includes Si lens and coaxial cable with BNC connector
THz emitter for 1060 nm wavelength	EMT-10	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 Emitters & Detectors