Fast, accurate responsivity calculations for detectors, fiber links, and lab setups today. Choose units, include efficiency, view steps, then download CSV or PDF instantly.
These sample values are typical for quick checks; use calibrated instruments for final work.
| # | Wavelength (nm) | Optical Power (mW) | Photocurrent (µA) | Gain M | Measured R (A/W) |
|---|---|---|---|---|---|
| 1 | 850 | 0.50 | 120 | 1.0 | 0.240 |
| 2 | 940 | 0.30 | 75 | 1.0 | 0.250 |
| 3 | 1310 | 0.80 | 520 | 5.0 | 0.130 |
R = I / (P · M)
R = η · q · λ / (h · c)
1.602176634×10⁻¹⁹ C.6.62607015×10⁻³⁴ J·s.299792458 m/s.Photodiode responsivity (A/W) links optical power to electrical current, making it the primary figure for receiver sensitivity and calibration. In laboratory radiometry, responsivity converts a power meter reading into an electrical signal budget. In telecom, it predicts photocurrent for a given launch power and loss.
Silicon photodiodes commonly peak between 0.45 and 0.65 A/W near 850–950 nm, while performance drops toward the UV and beyond 1100 nm. InGaAs devices cover 900–1700 nm, often reaching about 0.8–1.0 A/W around 1550 nm under linear operation.
The theoretical expression R = ηqλ/(hc) shows that responsivity scales linearly with wavelength when η is constant. For η = 0.80 at 1550 nm, the predicted responsivity is about 1.00 A/W. At 850 nm with η = 0.75, the prediction is about 0.51 A/W.
Measured responsivity uses R = I/(P·M). Use photocurrent (light-on minus light-off) rather than total current, and ensure the optical spot stays within the active area. If coupling changes between measurements, treat the power at the diode plane as the reference value. For best practice, record temperature, bias voltage, connector type, and averaging time to support repeatable comparisons later.
APDs introduce multiplication M, which raises current but also adds excess noise. The calculator allows M so you can report “effective responsivity” while keeping the intrinsic diode responsivity separate. Document the bias and temperature because M can shift significantly with operating conditions.
Practical uncertainty is dominated by power meter calibration, alignment repeatability, and current measurement noise. A common approach is root‑sum‑square propagation of relative errors in I, P, and M. Even a 2% power uncertainty and 2% current uncertainty combine to roughly 2.8% in responsivity.
When wavelength is known, η inferred from measured responsivity helps validate datasheets and spot saturation. Values above 100% often indicate gain not accounted for, a power reference error, or nonlinearity. Values far below expectation can indicate reflection loss, poor coupling, or contamination.
Use responsivity with load impedance to estimate signal voltage, and combine it with noise sources to estimate SNR. For example, 0.8 A/W at 1550 nm yields 0.8 mA per milliwatt. With a 50 Ω load, that is about 40 mV per milliwatt before amplification.
Responsivity is the photocurrent produced per unit incident optical power. It is reported in amperes per watt and depends on wavelength, quantum efficiency, and device structure.
Measure light-on current and subtract light-off current to remove dark current. Keep alignment fixed, avoid saturation, and ensure the optical spot stays within the active area.
Photon energy changes with wavelength, and absorption varies with material bandgap. Even with constant efficiency, the theoretical relation shows responsivity increases linearly with wavelength.
M models multiplication inside avalanche or gain-enhanced photodiodes. Use M=1 for standard PIN devices. If you know the multiplication factor at your bias and temperature, enter it to compute effective responsivity.
If you enter uncertainties for current, power, and gain, the calculator combines their relative contributions using root-sum-square propagation. This provides an approximate ± responsivity suitable for reporting and comparisons.
Yes. With a known wavelength, EQE can be inferred from measured responsivity using η = R·h·c/(q·λ). Values above 100% often indicate unaccounted gain or a power reference error.
Use consistent units and convert to amperes and watts internally. Ensure the optical power corresponds to the power at the photodiode plane, not at the laser output.
Use consistent units to avoid responsivity calculation errors always.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.