Selecting the right photodetector starts with one question: what wavelength do you need to detect? Opto Diode’s detector portfolio spans from soft x-ray to mid-wave infrared, and the spectral band you’re working in narrows the field faster than any other parameter. This guide walks you through choosing by spectral band first, then refining by speed, active area, and cooling so you land on the right family and series for your design.
Start with the spectral band
Every detector technology has a wavelength range where it performs well and ranges where it simply won’t respond. Pin down your operating wavelength (or band) before anything else. Opto Diode’s portfolio covers high-energy photons and electrons in the x-ray and EUV region, the UV and visible bands, and out into the short- and mid-wave infrared.
Once you know your band, the table below points you to the matching family. Then use the speed, area, and cooling sections to choose a specific series.
By wavelength band → Opto Diode family
| Wavelength / spectral band | Recommended family | Material / technology | Notes |
|---|---|---|---|
| 0.0124–190 nm (soft x-ray, EUV; 100 eV–50 keV) | AXUV | Silicon, windowless | 100% internal quantum efficiency; high-energy photon, electron, and x-ray detection |
| 1–190 nm (EUV-optimized) | SXUV | Silicon | EUV-optimized photodiodes; high-speed and low-noise variants |
| 190–400 nm (UV) | UVG | Silicon, UV enhanced | Reliable UV detectors across a range of active areas |
| 400–740 nm (visible) | Blue & Red Enhanced | Silicon | Enhanced responsivity; blue-enhanced and red-enhanced options |
| 1–3 µm (near/short-wave IR) | PbS | Lead salt (PbS) | Near-IR lead-salt detection |
| 1–5.5 µm (mid-wave IR) | PbSe | Lead salt (PbSe) | High-sensitivity MWIR; uncooled and TE-cooled options |
| 400–1100 nm | Silicon APD | Silicon avalanche | High-gain, low-noise; for low-light and fast signals |
| 900–1700 nm | InGaAs APD | InGaAs avalanche | High-gain detection in the telecom/SWIR band |
You can browse the full lineup on the Detection category page.
Choose by detector family
Choose AXUV if…
You’re detecting high-energy photons, electrons, or x-rays anywhere from 0.0124 nm to 190 nm (roughly 100 eV to 50 keV). The AXUV family uses a windowless silicon design for enhanced response below 200 nm and offers 100% internal quantum efficiency with high stability. It’s the right call for electron detection, synchrotron radiation monitoring, electron reticle inspection, and radiation detection. AXUV ships in many form factors, including high-speed circular photodiodes, large-area square and rectangular detectors, center-hole versions, quad detectors, and multi-element arrays.
Choose SXUV if…
You’re working in the EUV band (1–190 nm) and want photodiodes optimized for that region. The SXUV series, part of our silicon detectors line, includes high-speed variants for fast EUV signals and low-noise variants for weak-signal measurement, plus large-area and integrated-filter options. SXUV also offers quadrant (4-quadrant) detectors in this band.
Choose UVG if…
Your signal sits in the ultraviolet, 190–400 nm. The UVG UV-enhanced silicon detectors are built for reliable UV measurement and come in a wide spread of active areas, from small to large square formats, so you can match the detector to your beam or field of view.
Choose Blue or Red Enhanced if…
You’re in the visible band, 400–740 nm, and want enhanced responsivity. The Blue & Red Enhanced silicon photodiodes feature low dark current and low capacitance and are offered in hermetic TO-18, TO-5, and TO-8 packages across a range of active areas. Blue-enhanced parts favor the shorter-wavelength end; red-enhanced parts favor the longer end. Typical uses include photometry and colorimetry, pulse oximetry, and bar code readers, and a bi-cell option is available for dual-element sensing.
Choose PbS or PbSe if…
You’re detecting in the infrared. The lead-salt PbS and PbSe detectors deliver high-sensitivity performance with high detectivity (D*) and low noise. Reach for PbS for near-IR work in the 1–3 µm range. Reach for PbSe when you need the mid-wave IR band out to 5.5 µm for gas analysis and spectroscopy, flame monitoring, and aerospace or defense sensing.
Choose an APD if…
You need high gain and low-light sensitivity with fast response, not just a standard photodiode. The avalanche photodiodes provide high-gain, low-noise detection in hermetically sealed packages. Pick a silicon APD for 400–1100 nm and an InGaAs APD for 900–1700 nm. These are the go-to detectors for LiDAR and laser rangefinding, autonomous-vehicle and safety sensing, optical communication, and scientific instrumentation.
Then refine by speed, active area, and cooling
Speed
If you’re recovering fast pulses or high-bandwidth signals, look for the high-speed members of a family. Both the AXUV and SXUV lines list dedicated high-speed circular photodiodes. APDs are inherently suited to fast, low-light signals such as LiDAR returns. For weak but slower signals, the low-noise SXUV variants and high-detectivity lead-salt detectors are a better fit.
Active area
Active area is a trade-off: a larger area is easier to align and captures more of a diverging or wide beam, while a smaller area generally favors speed and low capacitance. Opto Diode offers a broad span of active areas, from sub-square-millimeter APDs up to large-area AXUV detectors in square and rectangular formats. Match the active area to your spot size, alignment tolerance, and field of view, and don’t oversize it if speed matters.
Cooling
Cooling matters most in the infrared, where it lowers noise and improves detectivity. The PbSe line is offered in uncooled, one-stage thermoelectrically cooled, and two-stage TE-cooled configurations. Choose uncooled for the simplest, lowest-cost integration; step up to one- or two-stage TE cooling when your application demands lower noise and higher sensitivity. Our silicon, UV/EUV, visible, and APD detectors are typically selected on spectral response, speed, and area rather than cooling.
Talk to an applications engineer
Still deciding between families, packages, or active areas? Opto Diode’s team can help you match a detector to your exact wavelength, signal level, and environment. Contact us to discuss your application.
FAQ
Which parameter should I choose a photodetector by first?
Start with wavelength. Your operating spectral band determines which detector technology can respond at all, so it narrows the field faster than speed, active area, or cooling. Once the band points you to a family, refine within that family.
What’s the difference between a standard photodiode and an APD?
An avalanche photodiode (APD) provides internal gain, giving it high sensitivity and fast response for low-light and high-speed signals such as LiDAR returns, where a standard photodiode would not deliver enough signal. Opto Diode offers silicon APDs (400–1100 nm) and InGaAs APDs (900–1700 nm).
Which detector covers the infrared, and do I need cooling?
Lead-salt PbS (1–3 µm) and PbSe (1–5.5 µm) detectors cover the IR bands. Cooling is optional and improves noise and detectivity; PbSe is available uncooled as well as one-stage and two-stage thermoelectrically cooled.
How do I detect EUV, soft x-rays, or electrons?
Use the AXUV family for high-energy photons, electrons, and x-rays (0.0124–190 nm), and the SXUV series for EUV-optimized measurement (1–190 nm). AXUV’s windowless silicon design delivers 100% internal quantum efficiency for these demanding applications.