Accessories for THz near-field setups

Light, targets
& cabling.

Components that complete a TeraSpike setup: SHG-Units that let LT-GaAs probes run on 1550 nm fiber lasers, a test target for characterizing THz imaging systems, and RF cables configured from probe to amplifier.

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1550 → 775 nm
SHG-Unit, frequency doubling
10 – 50 %
Typ. conversion efficiency
2 µm – 8 mm
Test target structure sizes
SMP → SMA / BNC
TS Cable, 50 Ω RG178
01 · IR-to-NIR light conversion

SHG-Units.

LT-GaAs photoswitches, as used in TeraSpike microprobes and TeraBlast emitters, are excited around 800 nm. The SHG-Unit frequency-doubles femtosecond pulses from a fiber laser at 1500–1600 nm into the 750–800 nm range, so cost-efficient telecom-wavelength lasers can drive these devices. The design is passive and robust, and the unit is ready after a short warm-up of 10–15 minutes.

SHG-Unit, FS version: black cylindrical module with silver adjustment ring on a post holder with clamping fork.
TD-1550-SHG-FS. Free-space output; free-space or fiber-coupled input, aperture ca. 6 mm.
SHG-Unit, Mini-FC version: slim black tube labelled TD-1550-NLO-MINI-FC with a green fiber connector, mounted on a post.
TD-1550-SHG-MINI-FC. Fiber-coupled input, free-space output, 77 × 21 mm.
Schematic of both versions. FS version: IR input through an aperture, a lens, a crystal behind the adjustment ring and a lens to a removable color filter, NIR output as a free-space beam. Mini-FC version: fiber-coupled IR input, crystal, lens, free-space NIR output.
Optical layout. Left: FS version with aperture, adjustment ring and removable color filter. Right: Mini-FC version with fiber connector (FC). In: IR, 1500–1600 nm; out: NIR, 750–800 nm.

Key benefits

  • Recommended for TeraSpike microprobe operation with IR femtosecond lasers
  • High power conversion efficiency
  • Passive and robust design
  • Short warm-up time, 10–15 min
  • Free-space (-FS) or fiber-coupled (-MINI-FC) input
  • Easy to use and to integrate into an existing setup

Technical data

TD-1550-SHG-FS-MINI-FC
Input wavelength1500 … 1600 nm
Output wavelength750 … 800 nm
Typ. average input power10 … 200 mW
Typ. power conversion efficiencya10 … 50 %
Input beamfree-space or fiber-coupledfiber-coupled
Output beamfree-space
Min. aperture diameterca. 6 mm—
Dimensions (l × d)120 × 45 mm77 × 21 mm

a For an input pulse length of 90 fs and a pulse repetition rate of 80 MHz.

02 · Imaging system characterization

Terahertz test target.

The P-TTT-2-1200 was developed to characterize THz imaging systems. With structures from 2 µm to 8 mm lateral size it serves standard diffraction-limited systems as well as near-field systems with sub-wavelength resolution. On high-resistivity silicon it combines uncoated areas of maximum transmission with conductor areas of three different transmission levels.

Layout of the 50 by 50 mm test target P-TTT-2-1200: orthogonal triple stripe groups from 2 to 1200 µm, a 45-degree diagonal row of stripe groups, a Siemens star, inverted Newton rings, a column of continuous sheet-resistance reference areas with tilted metal gratings beside it, a gold metamaterial area with double-slit arrays and a dipole antenna array area.
Target layout, 50 × 50 mm. Grey levels: chromium coatings of 10, 50 and 60 nm (semi-transparent); yellow: 50 nm gold (opaque).

What it is for

  • Evaluating THz far-field and near-field imaging systems with semi-transparent thin-film conductor structures
  • Resolution tests from sub-wavelength to diffraction-limited: 2 µm to 1.2 mm
  • Metamaterial structures with local field enhancement, useful for near-field system evaluation
  • Contrast evaluation and referencing of sheet resistance imaging systems

Classic resolution structures — triple stripes, Siemens star, concentric rings — are complemented by structures for near-field work, such as metamaterial arrays with local field confinement, and by reference areas for sheet resistance imaging and wafer scanning.

Technical data

P-TTT-2-1200Value
SubstrateHigh-resistivity FZ silicon, 2-side polished, > 10 kΩ·cm
Size · thickness2″ × 2″ (50 × 50 mm) · 525 µm
CoatingsCr: 10 nm, 50 nm and 60 nm (semi-transparent); Au: 50 nm (opaque)
Orthogonal triple stripes2 – 1200 µm lines & spaces; 45° rotated: 2 – 460 µm
Siemens star6 mm outer diameter, 18 elements
Inverted Newton rings5.6 mm outer diameter, ring widths 10 – 500 µm
Continuous Rsh reference areas4 areas, 6.7 × 8.3 mm each
Tilted metal grating areas6 areas, 2 × 6.7 mm each; 0° – 90° in 18° steps
Bow-tie (dipole) array metamaterial300 µm length, 5 µm gap
Double-slit array metamaterial3 µm and 6 µm slit width and spacing
03 · RF connection

TS Cable.

A highly flexible 50 Ω cable from the SMP connector of a TeraSpike microprobe to your amplifier or lock-in input: SMP female on the probe side, SMA male on the instrument side. Two versions are available, with a straight or a right-angle SMP connector. An SMA-to-BNC adapter is always included. The TS Cable is also part of the TeraSpike starter kit.

Blue RG178 cable with a gold SMP connector on one end and an SMA plug on the other, next to an SMA-to-BNC adapter.
TS Cable with SMP and SMA connectors and the included SMA-to-BNC adapter.

Two versions

Right-angle SMP 80 cm Order code TS Cable L080-R1-CSMA-M2-S2
Straight SMP 40 cm Order code TS Cable L040-S1-CSMA-M2-S2

Both versions: SMP female to SMA male, supplied with an SMA-to-BNC adapter.

Product details

  • Gold-plated brass contacts, MIL-STD-348A
  • Highly flexible, min. bend radius 10 mm
  • Operating temperature −55 … 150 °C
  • Heat-shrink connector claddings
  • Included: SMA-to-BNC adapter

Technical data

TS CableValue
RF cable typeRG178
Impedance50 Ω
Nominal capacitance96.46 pF/m
Connector 1 (probe side)SMP female, straight or right-angle
Connector 2 (instrument side)SMA male
Length80 cm with right-angle SMP · 40 cm with straight SMP
IncludedSMA-to-BNC adapter
Ready to specify

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