Choosing The Right Photodetector Selector
Match Your Application To The Detector It Deserves
Selection guide
Photodetector Selector
Answer four questions to find the right detector for your application, then explore key parameters and trade-offs every engineer should know.
Step 1 of 4
What is your target wavelength range?
Key parameters explained
These are the datasheet values that most directly affect whether a detector will work in your system.
| Parameter | What it means | Matters most for |
|---|---|---|
| Responsivity (A/W) | Photocurrent generated per watt of incident light. Higher means more signal output per unit of light input. | All applications |
| Dark current (nA) | Current that flows with no light present. Sets the noise floor — lower is better for weak-signal detection. | Low-light, spectroscopy |
| Rise time / bandwidth | How quickly the detector responds to a changing signal. Smaller active area = lower capacitance = faster response. | Telecom, LiDAR, pulsed |
| Active area (mm²) | Size of the light-sensitive region. Larger catches more light but increases capacitance and slows the response. | Free-space, large beams |
| Shunt resistance (MΩ) | Resistance across the detector at zero bias. High shunt resistance reduces noise in DC or low-frequency systems. | Power meters, DC sensing |
| Gain (APDs only) | Internal multiplication from the avalanche effect. Amplifies weak signals before they reach external electronics. | LiDAR, photon-starved |
| Spectral range | The wavelength band over which the detector responds. Must overlap your light source and any optical filters used. | All applications |
| Linearity | How faithfully output current tracks input power across a dynamic range. Critical wherever data accuracy matters. | Spectroscopy, measurement |
Detector types at a glance
Standard InGaAs
900 – 1700 nm
The go-to for NIR sensing. Low dark current, excellent linearity. Available in small-area (fast) and large-area (sensitive) formats.
Extended InGaAs
1700 – 2600 nm
Extends sensitivity past standard InGaAs. Higher dark current — often thermoelectrically cooled. Best for gas sensing and SWIR spectroscopy.
High-speed InGaAs
GHz bandwidth
Small active area, low capacitance, fast rise times. Optimized for optical communications and high-frequency pulsed systems.
Avalanche (APD)
Internal gain
Built-in multiplication amplifies very weak signals. Best for LiDAR, OTDR, and photon-starved applications where SNR is critical.
Germanium
800 – 1800 nm
Cost-effective for strong-signal NIR. Higher dark current than InGaAs but useful for large-area power sensing where noise budget allows.
Quadrant / position
Beam tracking
Segmented active area allows beam centroid measurement by comparing signals across cells. Used in alignment and stabilization systems.
Common trade-offs
Every detector selection involves balancing competing properties. These are the tensions engineers encounter most often.
| If you want more of this... | ...you typically give up some of this |
|---|---|
| Active area (sensitivity) | Speed — higher capacitance means slower response bandwidth |
| Wavelength range (extended InGaAs) | Dark current — more noise, often requires thermoelectric cooling |
| Internal gain (APD) | Noise figure and bias voltage complexity |
| Speed (high-speed InGaAs) | Tolerance for misaligned or large-diameter beams |
| Lower cost (Germanium) | Noise floor and dark current performance vs. InGaAs |