Parameters
Presets
Optical / Electrical Parameters
Quantum efficiency η0.90
Wavelength λ1550 nm
Active area A0.50 mm²
Bandwidth B1.0 GHz
Dark current I_d1.0 nA
Load resistance R_L50 Ω
Temperature T300 K
Incident power P1.0 μW
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Responsivity [A/W]
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Photocurrent [μA]
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NEP [pW/√Hz]
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D* [10¹⁰ cm√Hz/W]
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SNR [dB]
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Min. Det. Signal [pW]
Noise Component Comparison
Optical Power vs SNR
Key Formulas
Responsivity:
$$R = \frac{\eta e}{h\nu} = \frac{\eta e \lambda}{hc} \quad \text{[A/W]}$$Shot noise:
$$i^2_{shot} = 2e(I_{photo} + I_d)\cdot B$$Johnson (thermal) noise:
$$i^2_{thermal} = \frac{4k_B T B}{R_L}$$SNR:
$$\mathrm{SNR} = \frac{(R\cdot P)^2}{i^2_{shot}+i^2_{thermal}}$$Specific detectivity:
$$D^* = \frac{\sqrt{A \cdot B}}{\mathrm{NEP}} \quad \text{[cm}\cdot\sqrt{\text{Hz}}\text{/W]}$$
Engineering Note: First identify whether shot noise or Johnson noise dominates. High-impedance (transimpedance amplifier) design reduces thermal noise. Cooling suppresses dark-current shot noise, approaching the quantum-limited SNR. For LiDAR, APD excess noise factor F must also be included.