Opto Diode, an ITW company, builds two silicon photodiode families for the soft x-ray and extreme-ultraviolet (EUV) range, and both detect down into the same difficult part of the spectrum where conventional windowed detectors fall short. The difference is in how each is optimized: AXUV is engineered for absolute, calibration-grade response across an exceptionally broad band, while SXUV is hardened to survive the high-intensity EUV environments that would degrade an ordinary diode. Choosing the wrong family means either leaving sensitivity on the table or watching responsivity drift mid-program — so the selection deserves a deliberate look.
AXUV vs SXUV at a Glance
| Parameter | AXUV | SXUV |
|---|---|---|
| Wavelength / spectral range | 0.0124 nm to 190 nm; detects energy from 100 eV to 50 keV | 1 nm to 190 nm (individual models labeled 1 nm–190 nm) |
| Quantum efficiency | 100% internal quantum efficiency (UV to visible spectrum) | Broad spectral responsivity (specific QE values not published on the page) |
| Window / construction | Windowless for enhanced response below 200 nm | Detector construction details not published on the page |
| Radiation hardness | Not specified as a primary attribute | High radiation hardness; low-noise performance |
| Representative active areas | 3, 10, 20, 23, 36.5, 63, 100, 331, 576.5 mm² | 1.25, 5, 20, 100, 331 mm² |
| Primary applications | Electron detection, synchrotron radiation monitoring, electron reticle inspection | EUV lithography, x-ray spectroscopy, synchrotron radiation monitoring |
All specifications above are drawn directly from the Opto Diode AXUV and SXUV product-category pages. For the physics behind the AXUV figures — why quantum efficiency exceeds unity in the XUV, the 0.27 A/W ideal responsivity limit, and where effective silicon thickness limits the response — see AXUV photodiode operating principles.
When Should You Choose AXUV?
- You need 100% internal quantum efficiency for absolute, calibration-grade radiometry rather than relative measurements.
- Your work spans an extremely broad band — 0.0124 nm to 190 nm, covering energies from 100 eV up to 50 keV — and you want a single detector technology across photons, electrons, and x-rays.
- A windowless front end is acceptable (and desirable), since it delivers enhanced response below 200 nm without window-absorption losses.
- Your application is electron detection, synchrotron radiation monitoring, or electron reticle inspection.
- You need a wide menu of active areas, from a compact 3 mm² up to a large 576.5 mm², to match beam size or solid-angle requirements.
When Should You Choose SXUV?
- Your detector will see high-intensity EUV flux, where high radiation hardness is essential to maintain stable responsivity over the life of the program.
- You are working in EUV lithography — the headline application for this family — and need a diode that holds up under repeated, intense EUV exposure.
- You want low-noise performance combined with broad spectral responsivity across roughly 1 nm to 190 nm.
- Your application is x-ray spectroscopy or synchrotron radiation monitoring in an environment that would degrade a non-hardened diode.
Representative Models
AXUV detectors (browse the full AXUV line):
- AXUV20HS1 (20 mm²) and AXUV20A (23 mm²)
- AXUV63HS1, AXUV63HS1-CH (63 mm² class)
- AXUV100G, AXUV100TF030, AXUV100TF400 (100 mm² class)
- AXUV300C (331 mm²) and AXUV576C (576.5 mm²) for large-area needs
- AXUV16ELG, AXUV20ELG, and AXUVPS7 for specialized configurations
SXUV detectors (browse the full SXUV line):
- SXUVPS4, SXUVPS4C (1.25 mm² class)
- SXUV5 (5 mm²)
- SXUV20HS1, SXUV20C (20 mm² class)
- SXUV100, SXUV100TF135 (100 mm² class)
- SXUV300C (331 mm²) for large-area EUV monitoring
Model availability, active-area options, and thin-film coatings vary; confirm the exact configuration against the current product pages before specifying.
The Bottom Line
If your priority is absolute quantum efficiency over the widest possible band — for synchrotron, electron, and x-ray work — AXUV is the natural starting point. If your priority is surviving high-intensity EUV with stable responsivity — the defining requirement of EUV lithography — SXUV is built for that duty. Both families are designed and built by Opto Diode — a US-based ITW company in Camarillo, California — with the engineering support to match a detector to your application.
Not sure which family — or which active area and coating — fits your beamline or tool? Contact Opto Diode for a quote and application support and our team will help you match the detector to your spectral range, geometry, and radiation environment.
Frequently Asked Questions
Which family has higher quantum efficiency?
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The AXUV family is specified with 100% internal quantum efficiency from the UV into the visible spectrum, making it the choice when absolute, calibration-grade response matters. The SXUV pages describe broad spectral responsivity but do not publish specific quantum-efficiency figures.
Which photodiode is right for EUV lithography?
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SXUV. EUV lithography is the lead application for the SXUV family, which pairs high radiation hardness with low-noise performance to keep responsivity stable under intense EUV exposure.
Which family is more radiation-hard?
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SXUV is the radiation-hardened family, explicitly characterized by high radiation hardness for demanding EUV and x-ray environments. AXUV is optimized instead for windowless broadband response and 100% internal quantum efficiency.
Can Opto Diode customize these detectors?
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Both families ship in a range of active areas — from 1.25 mm² up to 576.5 mm² across the two lines — along with various model configurations and thin-film options. For specific active-area, coating, or packaging requirements, reach out for a quote to discuss your application.
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Reviewed and updated July 2026.