The GATE Grind

GATE 2023 IN – Question 38

Communication and Optical Instrumentation · Optical sources and detectors · 2 marks · Multiple choice

A p-i-n photodiode receives a light pulse containing $8\times10^{12}$ photons at wavelength $\lambda_0=1.55$ μm. An average of $4\times10^{12}$ electrons is collected at its terminals. Its quantum efficiency at this wavelength is ______ %.

  1. 50
  2. 54.2
  3. 62.5
  4. 80

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Correct answer: (A) 50

Explanation

Quantum efficiency is electron count divided by photon count: $\eta=(4\times10^{12})/(8\times10^{12})=0.5$.

Thus the answer is **50%, A**.