Block scheme of a typical terahertz time-domain measurement system for near-field transmission measurements.
Breaking the resolution limits of standard THz imaging systems and opening the door to direct THz-based microstructure analysis:
The patent-protected TeraSpike microprobe series offered by Protemics enables the surface-near detection of THz light with micron-resolution. This covers applications ranging from contactless sheet resistance measurement or time-domain reflectometry for fault isolation in chip-packages to THz near-field imaging at planar THz devices, metamaterials or waveguides. Thanks to the low optical power requirements of the TeraSpike microprobes (typ. <4 mW average power) they are compatible to most pulsed laser sources (pulse durations < 150 fs recommended).
Our current product portfolio includes:
We also offer design and fabrication services for custom products as well as measurement services and research studies. Please contact us for further information.
"Your laser-based THz system can do much more than just spectroscopy - discover the fascinating world of high-resolution THz applications!"
For further technical information please also refer to our product brochure.
Our scanning system solutions are the ideal modular platform for THz near-field imaging applications of any kind. All system components are optimized for the utilization of TeraSpike microprobes at maxmimum performance.
Standard scanning system configurations may be combined with a suitable laser systems on customer side or can be extended with a new laser source for optical excitation.
Scanning systems are designed for applications such as:
The TeraCube Scientific is a fully automated THz near-field scanning system to be operated in an optical laboratory surrounding. It can be driven by an existing fs-laser source with suitable specifications or extended with a new laser source. The system enables time-domain measurements of THz field distributions in a controlled distance of a sample surface. The system provides broadband THz pulse excitation and transmission through planar samples as well as spatially and temporally resolved detection of the transmitted pulses in the surface near-field using Protemics proprietary TeraSpike near-field microprobes.
|Spectral range||0.05 - 3 THz|
|Maximum sample size (x, y, z)||20 cm, 20 cm, 1 cm|
|Maximum scanning speed (x, y) without load||200 mm/s|
|Min. scanning time per pixel||10 ms|
|Maximum scanning range (x, y, z)||18 cm, 18 cm, 3 mm|
|Time-domain scanning range width||1000 ps|
|Time-domain step resolution (dt)||6.6 fs|
|Min. bi-directional repeatability (x, y, z)||+-0.1 µm, +-0.1 µm, +-0.15 µm|
|Min. step resolution (dx, dy, dz)||0.1 µm, 0.1 µm, 0.15 µm|
Vibration-damped optical table with 1.5 m x 1m x 1m of space for system placement
Laser laboratory specification of class 3R or higher
Center wavelength: 770 nm ... 820 nm
Repetition rate f: 10 MHz ... 1 GHz
Avg. optical power P: 60 mW ... 1.5 W
Pulse duration: < 150 fs
For further information or quote requests please contact us.
The microprobe series TeraSpike is the new generation of high-performance microprobes for the photo-conductive detection of electric fields in the THz frequency range. Surface-near electric THz fields can now be measured with unprecedented signal quality and low invasiveness. The microprobes seamlessly fit into systems with optical excitation wavelengths below 860 nm and are the most cost-efficient solution to turn an existing time-domain pump/probe-system into a powerful THz near-field system for high-resolution imaging.
In addition to custom-specific microprobes (please inquire) the following standard models are offered for pulsed excitation:
Electrical connection is done through a compact coaxial SMP plug. We recommend the use of a low-noise current amplifier with 107-108 V/A amplification (e.g. DLPCA200) and high-grade connection cables (e.g. our TS Cable) for optimum operation.
The microprobes from the X-series are sensitive to electric vector field-components oriented in transversal direction to the probe-tip axis as defined by the x-axis direction in the upper illustration. The model TD-800-X-HR offers highest spatial resolution. The model TD-800-X-HRS is characterized by highest sensitivity for f = 0.5 THz - 1.3 THz and 20 µm spatial resolution.
|Max. spatial resolution||3 µm||20 µm|
|Photo-switch gap size||1.5 µm||2 µm|
|Dark current @ 1 V Bias||< 0.5 nA||< 0.5 nA|
|Photocurrent @ 1 V Bias||> 1 µA||> 0.6 µA|
|Excitation wavelength||700 .. 860 nm|
|Average excitation power||0.1 .. 4 mW|
|Max. spatial resolution||8µm||8µm|
|Photo-switch gap size||2µm||5µm|
|Dark current @ 1 V Bias||< 0.4 nA||< 0.4 nA|
|Photocurrent @ 1 V Bias||>0.1 µA||> 0.5 μA|
|Excitation wavelength||700 .. 860 nm||700 .. 860 nm|
|Average excitation power||0.1 .. 4 mW||0.1 .. 4 mW|
Z-series microprobes are sensitive to THz field components oriented in longitudinal direction to the probe-tip axis as defined by the z-axis direction in the upper illustration. The N-option does not include a resonant antenna element and provides a somewhat higher bandwidth. The A-500G-option includes an antenna element for enhanced sensitivity around 0.5THz.
The new TeraSpike model TR.5 comes with a pair of closely spaced photoconductive THz antennas offering new means for high-performance near-field measurements in reflection-mode. While one antenna is used as a radiation pulse generator, the other antenna is used as the detector. The slim transceiver probe is taking advantage of Protemics´ proprietary “wave-trap” design for the suppression of probe-internal reflection signals as well as the XR-type flexible PET cantilever design for increased mechanical robustness. In contrast to standard reflection-mode approaches based on far-field emitter/detector components the new near-field transceiver probe provides access to sub-wavelength-resolution and shortest THz transmissions paths.
|Dark current @ 1 V Bias||< 1.5 nA|
|Photocurrent @ 1 V Bias||> 0.5 µA|
|Excitation wavelength||700 .. 860 nm|
|Average excitation power||0.1 .. 4 mW|
|Connection type||2x SMP|
The TeraSpike TD-1550-Y-BF is a microprobe emitter based on patent pending design (DE 10 2013 020 216.7) for the bias-free surface-near excitation of Terahertz pulses on planar waveguides, metallic surfaces or meta-materials. The optically generated THz field is polarized in y-direction.
Configuration: THz pulse generation on a thin-film microstrip line using the bias-free TeraSpike emitter microprobe. For on-chip contact-free THz field detection a second TeraSpike probe from the TD-800-X or Z series can be applied.
THz Emission scheme: THz pulse generation is based on optical excitation of the InGaAs micro-cantilever surface. Placing the excited tip close to a conductive structure or surface allows efficient capacitive coupling and pulse transmission.
|Excitation wavelength||700 .. 1600 nm|
|Average excitation power||0.1 .. 4 mW|
|Emission bandwidth (for 90 fs pulse excitation)||> 2.5 THz|
This kit is the ideal solution to start with. It includes the following components:
With this set the orientation of the mounted TeraSpike microprobe can be freely chosen as required by the application. The use of the dummy device TeraSpike Phantom - as included in the starter kit - is recommended during all mechanical set-up and construction works because the risk of an uncontrolled mechanical impact during such processes can be easily avoided. Each microprobe is delivered in a robust transport and storage box.
The standard design of the TeraSpike probe is optimized for highest spatial resolution, lowest field invasiveness and highest sensitivity. This is achieved through the free-standing semiconductor-based cantilever microstructure containing the active field sensor elements. The mechanical robustness of this standard design matches the requirements of long-term application in well controlled and automated systems such as the TeraCube Scientific allowing also pointed sample contact.
For application in rougher environments or where the sample distance is more difficult to control the new XR-design is an excellent choice with drastically further increased mechanical robustness combined with only low reduction of spatial resolution and sensitivity.
The XR-option is currently available for the following x- and z-field sensitive TeraSpike probes:
If you are interested in an XR-option for other TeraSpike models, please contact us.
TeraSpike near-field probes are used under different excitation conditions. Some configurations might generate THz modes which are able to propagate along the internal electrodes of the probe-tip. So far, these modes were observed in terms of reflection signals in the recorded time-domain transients.
Protemics has developed a new patent pending design* called “wavetrap” which is effectively slowing down and absorbing such probe-internal THz signal transmission.
The WT-option is currently available for the following x- and z-field sensitive TeraSpike probes:
If you are interested in an WT-option for other TeraSpike models, please contact us.
*German patent application DE 10 2014 015 516.1
The GigaSpike field probe series features low-invasive micro-antenna structures with integrated Zero-Bias Schottky-diodes for the active measurement of 3D field amplitude distributions. GigaSpike probes are offered for the frequency range from 25 GHz to 330 GHz. Thanks to their low-invasiveness they allow field measurements in close proximity to a device under test with only a minimal amount of back-scattering of the probed field and parasitic coupling effects. The GigaSpike probe is hence an ideal device for 3D vector field amplitude or power density measurements in the far- and near-field regions of millimeter-wave emitters, such as 5G Wigig antenna arrays. They can also be used to measure the radiation profile of photo-conductive Terahertz emitters.
|GS-28-XYZ||25 .. 32 GHz|
|GS-60-XYZ||56 .. 70 GHz|
|GS-285-X||250 .. 330 GHz|
Customized probes for other frequency ranges are available on request.
Probe response curve: DC output voltage versus high-frequency E-field amplitude strength.
Min .. Max
|Frequency range||56 .. 70 GHz|
|Power density range||0.005 .. 200 µW/mm2|
|DC output voltage range||0.1 mV .. 1100 mV|
|Responsivity||5500 .. 20000 Vmm2/W|
GigaSpike technical information download.
Interested in the GigaSpike high-frequency E-field probe? Please inquire here.
The new bias-free Terahertz emitter series TeraBlast from Protemics are optically pumped THz sources which can be used with a wide range of femtosecond laser sources (such as low power oscillators or amplified lasers with wavelengths in the range of 700..1600 nm). They are ideally suited and tested for near-field imaging applications including TeraSpike microprobe operation. The TeraBlast is however also a great emitter for far-field spectroscopy and other THz applications.
TeraBlast emitters are based on a patent pending technology (German patent application: DE102012010926 A1) utilizing bi-metallic grating structures for the optical bias-free generation of Terahertz radiation. The emitters offer a large active area and can be excited by pulsed Femtosecond lasers within a broad range of average power from 5 mW up to above 1 W without causing the typical signs of conversion efficiency saturation or device failures as known from small-scale photoconductive antennas. Furthermore, TeraBlast emitters are the ideal solution for applications where THz pulse generation needs to occur in close proximity to photoconductive detection (e.g. near-field detection or butt-coupled waveguide excitation). In such situations voltage-biased emitters are often unusable because of strong parasitic coupling effects from modulated photocurrents which are avoided for the bias-free TeraBlast emitters.
THz pulse emission is generated by optical excitation of the TeraBlast emitter through femtosecond near-infrared or infrared pulses. Pulse durations < 150 fs are recommended. The emitted Terahertz radiation is linearly polarized. The following plot is showing an exemplary measurment of the emitted THz field which is line scanned across the center of the TeraBlast emitter in time-domain using a TeraSpike microprobe (Model: TD-800-X-HRS). The bright fast oscillating THz frequency components are well confined to an aperture area of few millimeter size, whereas GHz radiation is emitted over a much wider range. The emission profile can be easily adapted by adjusting the focussing of the optical excitation beam.
Exitation scheme: The THz emission process is based on Schottky-field induced lateral photo-currents (jph) at the multiple asymmetric metal/semiconductor junctions.
Measurement example (TeraBlast TD-1550-L-165): Far-field transmission through N2-purged free-space measured with a femto-second laser from Laser Quantum („taccor") and electrooptic detection in a 400-µm-thick GaP crystal using ASOPS based time-domain spectroscopy.
|Excitation wavelength range||700 .. 1600 nm|
|Typ. average excitation power range||5 mW .. 1000 mW|
|Average THz emission power||> 2.5 µW (a)|
|Active area diameter||ca. 11 mm (b)|
|Adapter dimension (Outer diameter)||1/2 inch|
Anti-reflection coating (-AR)
For Terahertz emission spectra without Fabry-Perot signature THz pulse reflection at the emitter backside can be suppressed by this broadband anti-reflection coating. Please note, that the field amplitude of the emitted pulse is also reduced by approx. 30% through application of the AR-coating.
High-pass filter (-HPF)
In order to allow THz field measurements in close distance to the TeraBlast emitter without a dominating contribution of low-GHz-Range radiation the emitter can be equipped with an intergrated high-pass filter at the output facet.
(a) Measured with pyroelectric detector (Spectrum Detector Inc. SPI-D-62-THz) for 370 mW optical pump power
(b) Larger active areas possible. Please request!
The integration of TeraSpike microprobes into existing optoelectronic set-ups is simplified through the use of standardized optical mounting components and the following sub-systems featuring further basic funtions.
The core sub-system D-B1-TR is a mini-board module with pre-aligned opto-mechanical components for the system integration of the TeraSpike transceiver microprobe series (TR).
The core sub-system D-B1 is a mini-board module with pre-aligned opto-mechanical components for the system integration of TeraSpike microprobes
Sub-system D-B2 is a vertical breadboard platform holding the core module D-B1 as well as further beam guiding components. It is offering enough space for additional components such as a CCD camera for probe-tip monitoring or a distance sensor for the sampling of profiled or tilted sample surfaces.
Exemplary CCD camera image of a TeraSpike microprobe tip above sample microstructure.
The following accessory is offered.
The test target P-TTT-2-1200 has been specially developed for the characterization of Terahertz imaging systems. Featuring structures and areas from 2 µm up to 8 mm of lateral size it is suited for standard diffraction-limited systems as well as near-field imaging systems with sub-wavelength resolution.
The test target is based on high-resistivity silicon and contains conductor areas with three different transmission strengths beside uncoated substrate areas with maximum transmission. The featured structures include classic resolution test structures such as orthogonal pairs of three stripe structures, a Siemens star and concentric rings. These typical structures are accompanied by further structures specially useful for near-field imaging purposes such as metamaterial structures generating local field confinement. Additionally, areas helpful as references for sheet resistance imaging and wafer scanning applications are also listed.
High-resistivity FZ silicon, 2-side polished
> 10 kOhm cm
|Target overall size||2" x 2" (50 mm x 50 mm)|
Cr: 10 nm, 50 nm and 60 nm (in semi-transparent areas)
Au: 50 nm (opaque)
Orthogonal pairs of three stripe structures
2 – 1200 µm wide lines & spaces
45° rotated for 2 - 460 µm wide line & spaces
6 mm outer diameter, 18 elements
|Inverted Newton rings||
5.6 mm outer diameter
Ring widths from 10 – 500 µm in increasing steps
|Continuous Rsh Reference areas||
Four areas, each 6.7 mm x 8.3 mm
|Tilted metal grating areas||
Six areas, each 2 mm x 6.7 mm
Tilting angles: 0°, 18°, 36°, 54°, 72°, 90°
Bow-tie array metamaterial
300 µm length, 5µm gap
Asymmetric double slit array metamaterial
3 µm and 6 µm slit width and spaces
The TeraSpike Defender is an optional housing protecting the sensitive tip of the probe against accidential mechanical impact. The exposure of the tip can be manually adjusted from -1mm to +1mm. In the negative exposure range a direct contact of the probe-tip to a flat surface is prevented by the TeraSpike Defender housing. Optical excitation as well as visual monitoring of the tip region is not impaired by the protective structure thanks to vertically placed openings. The TeraSpike Defender can be applied to any existing or new TeraSpike probe.
The new SHG-Unit from Protemics is an easy to operate and very efficient solution to convert IR light from cost-efficient femtosecond fiber-lasers into NIR light for the high-efficiency excitation of our LT-GaAs-based TeraSpike microprobes and TeraBlast emitters.
|Type||SHG-Unit TD-1550-NLO (-FS/-FC)|
|Input wavelength range||1500 .. 1600 nm|
|Typ. average input power range||30 .. 200 mW|
|Typ. power conversion efficiency (a)||10 .. 50% (a)|
|Min. aperture diameter||ca. 10 mm|
|Dimension (l x d)||120 mm x 45 mm|
The TeraSpike Phantom is a dummy device for the replacement of a microprobe during construction work and system development. The use of the TeraSpike Phantom - as also included in the starter kit - is recommended to avoid the risk of an uncontrolled mechanical impact in critical working situations.
SMP to SMA connection cable plus SMA-to-BNC adapter (also included in the starter kit).