Calculator Inputs
Use any supported mode. The page stays single-column, while the form fields adapt to large, smaller, and mobile screens.
Example Data Table
| Case | Wavelength (nm) | QE (%) | Responsivity (A/W) | Optical Power (µW) | Photocurrent (µA) |
|---|---|---|---|---|---|
| Blue detector test | 450 | 70 | 0.254 | 100 | 25.4 |
| Visible red setup | 650 | 80 | 0.419 | 180 | 75.4 |
| Near-IR receiver | 850 | 78 | 0.534 | 250 | 133.5 |
| Longer-wave device | 980 | 82 | 0.648 | 320 | 207.4 |
Formula Used
R = η × q × λ / (h × c)
R ≈ η × λ(nm) / 1240
Iph = R × Popt
Popt = Iph / R
η = (1240 × R / λ(nm))
in = √(2 × q × Itotal)
irms = in × √B
NEP = in / R
D* = √A / NEP
Here, η is the quantum efficiency in decimal form, R is responsivity in A/W, λ is wavelength, I is current, P is optical power, B is bandwidth, and A is active area in cm².
How to Use This Calculator
- Select the mode matching the values you already know.
- Enter wavelength if you want wavelength-dependent QE or responsivity calculations.
- Fill in power, current, responsivity, or QE as required by your selected mode.
- Add dark current, bandwidth, and active area for advanced noise estimates.
- Press Calculate Responsivity to show results above the form.
- Review the metrics, use the Plotly graph, and export CSV or PDF when needed.
FAQs
1) What does photodiode responsivity mean?
Responsivity shows how much photocurrent a detector produces for each watt of incident optical power. It is usually expressed in amperes per watt and changes with wavelength and device efficiency.
2) Why does wavelength affect responsivity?
Each photon carries energy that depends on wavelength. Longer wavelengths have lower photon energy, so a detector with the same quantum efficiency can produce different responsivity values across the spectrum.
3) How is quantum efficiency related to responsivity?
Quantum efficiency tells you what fraction of incoming photons generate charge carriers. Responsivity converts that photon conversion behavior into an electrical current-per-watt value, so the two metrics are directly linked.
4) What is dark current and why include it?
Dark current is the small current flowing without illumination. Including it helps estimate total current, shot noise, NEP, and detectivity more realistically for low-light optical receiver designs.
5) Can responsivity be greater than 1 A/W?
Yes, but usually only in devices with internal gain, such as avalanche photodiodes or photoconductive gain structures. Standard photodiodes without gain often stay below 1 A/W over common wavelengths.
6) Which units should I enter for power and current?
Use whatever unit matches your measurement setup. This calculator converts watts, milliwatts, microwatts, and nanowatts for power, plus amperes down to picoamperes for current.
7) What does NEP tell me?
Noise equivalent power estimates the optical power needed for a signal to match the noise floor in a 1 Hz bandwidth. Lower NEP generally means a more sensitive detector.
8) Why might the calculated QE look unrealistic?
A QE above 100% often means unit conversion errors, incorrect wavelength entry, or internal multiplication gain. Check current units, power units, wavelength, and detector operating mode carefully.