Source: ResearchGate

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The Concept of Responsivity in Photodetectors

The responsivity of a photodetector is a crucial parameter that defines its sensitivity to incident light. It is the ratio of the generated photocurrent to the incident optical power, measured in the linear response range.

Calculating Responsivity

The responsivity (R) can be calculated using the formula: R = η * (e / hν), where η is the quantum efficiency, e is the elementary charge, and hν is the photon energy. The unit of responsivity is typically amperes per watt (A/W).

Factors Affecting Responsivity

Responsivity is highest when the photon energy is slightly above the band gap energy of the photodetector material. For photodiodes, responsivity decreases sharply at photon energies corresponding to the band gap.

Types of Photodetectors

Photodiodes typically have responsivity values around 0.5 to 1 A/W, depending on the material and wavelength. Avalanche photodiodes and photomultipliers can have much higher responsivity due to internal current multiplication.

Operational Considerations

Operating a photodetector at wavelengths where responsivity is maximized ensures low detection noise, high signal-to-noise ratio, and optimal sensitivity. The detection bandwidth also affects the photodetector response.

Conclusion

Understanding the concept of responsivity is essential for optimizing the performance of photodetectors across various applications. By selecting the appropriate wavelength range and maximizing responsivity, one can enhance the sensitivity and reliability of photodetection systems.

Source: ResearchGate
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