TeraSpike - LT-GaAs photoconductive field detector
With the new device series TeraSpike we proudly introduce the next generation of microprobes for the photoconductive detection of electric fields in the THz frequency range. Based on our customers’ feedback and growing application-driven demands a thorough re-design of our previous near-field probe-tip has been developed. The result is a versatile detector for radiated and surface-near electric fields in the THz-range with unprecedented performance, robustness and applicability. It seamlessly fits into THz time-domain systems with optical excitation wavelengths below 860 nm and is the most cost-efficient solution to turn your system into a powerful high-resolution near-field THz system.
Your laser-based THz system can do much more than just spectroscopy – discover the fascinating world of high-resolution THz applications!
Key features
- Smallest active THz probe-tip on the market with only 1 µm cantilever thickness based on a patented design (DE 10 2009 000 823.3)
- Spatial resolution up to 3 µm
- Frequency range 0-4 THz
- Adaptable to all laser-based THz-Systems with λ < 860 nm
- Mounting compatible with standard opto-mechanical components
- Typical optical excitation power with common fs-lasers 1-5 mW (1-5 µJ/cm²)
Applications
- Terahertz research: Metamaterials, plasmonics, graphene, waveguides, …
- High-resolution Terahertz near-field imaging
- Contact-free sheet resistance imaging of semiconductors
- MMIC device characterization
- Non-destructive chip inspection
- Time-domain reflectometry (TDR)
Measured near-field distribution of a gated graphene layer on SiO2-Si revealing conductivity inhomogeneity.
Measured near-field image of a pulse-excited THz metamaterial surface.
Measured sheet conductivity image of a laser-doped multicrystalline silicon wafer.
Measurement services
AMO is also offering this innovative technology for measurement services on customer samples. Our advanced optoelectronic system with scanning speeds as high as 33 mm/s is able to provide crucial high-resolution conductivity information which is quasi inaccessible to existing measurement technology under cost and expenditure of time considerations.
For detailed information please refer to our service brochure or contact us directly.
Exemplary measurement set-up
The THz-Tip is mainly dedicated to be used in femtosecond pump probe experiments. The figure illustrates a typical set-up where the THz radiation transmitted through the sample is measured by the THz-Tip which is gated by the femtosecond probe beam.
Other configurations to measure in reflection or synchronized to HF devices in near-field are possible as well.
Best results, for fast transient recording, are obtained using a fast sampling technique like AMO´s AixScantechnology utilising shakers, ASOPS or ECOPS as a faster alternative to lock-in amplifiers with superior noise reduction also for low frequency noise.
Technical Data
AMO currently offers four different versions of near-field probes: The three probes from the X-series are sensitive to transversal THz field components. The new Z-series is sensitive to longitudinal THz field components. Within the X-series the HR-type is designed to provide highest spatial resolution while the HS-type is optimized for high sensitivity. The HRS-type offers highest field sensitivity from 0.5 THz to 1.3 THz at considerably higher spatial resolution (20 µm) than the HS (100 µm). All microprobes are designed for pulsed excitation and are equipped with an overvoltage protection. Each probe is individually tested and comes with manual & certificate enclosed.
For further information please take a look at our brochure (PDF file, 2 MB).
| TeraSpike TD-800- | X-HR | X-HRS | X-HS | Z-A-500G |
| Max. spatial resolution | 3 µm | 20 µm | 100 µm | 8 µm |
| Photoconductive gap size at tip | 1.5 µm | 2 µm | 3 µm | 5 µm |
| Dark current @ 1V Bias | < 0.5 nA | < 0.5 nA | < 0.4 nA | < 0.4 nA |
| Photocurrent | > 1 µA | > 0.6 µA | > 0.6 µA | > 0.5 µA |
| Excitation wavelength | 700 nm ... 860 nm | |||
| Excitation power | 1 mW ... 4 mW | |||
| Connection type | SMP | |||
excitation power 4 mW at a laser repetition rate of 80 MHz and approx. 100 fs pulse duration.
Integration in existing measurement systems
The integration of the TeraSpike microprobe into an existing (far-field) set-up is very simple thanks to a versatile mounting compatible to standardized opto-mechanical components. As required by the application the orientation of the TeraSpike can be freely chosen. For fast and easy implementation mounting post, post-holder and connection cable are included with the TeraSpike Starter Kit. The cheap dummy probe-tip TeraSpike Phantom - also included in the starter kit - is recommended to be applied during the mechanical set-up and construction work. Hence the risk of accidential mechanical impact during that process can be easily avoided. The probe is delivered in a robust transport and storage box.
With our opto-mechanical sub-system modules the integration of TeraSpike microprobes is further simplified. The core module D-B1 covers the functions of beam-to-tip alignment, focusing and probe-tip height variation. Module D-B2 is a vertical breadboard base 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.
The electrical connection is done through a small coaxial SMP plug. For the operation 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).
Further information can be found in the TeraSpike brochure. Please do not hesitate to contact us if you have any questions or need technical advice. In addition to our standard components we are also offering the fabrication of customized microprobe designs for your individual needs.
Order Information
| TeraSpike TD-800- | THz photoconductive probe-tip with SMP plug |
| Options: TD-800- | X-HR, X-HS, X-HRS or Z-A-500G |
| TeraSpike Phantom | Dummy probe-tip device |
| TS Cable | SMP to SMA/BNC probe connection cable |
| TeraSpike Starter Kit | Contains one TeraSpike TD-800-(X-HR, X-HS, X-HRS or Z-A-500G), TeraSpike Phantom, TS Cable, mounting post and post holder |
| DLPCA-200 | Variable gain current amplifier |
| Sub-System D-B1 | Axial positioning, focusing, alignment unit |
| Sub-System D-B2 | Vertical board base unit including D-B1 |
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