Quantum limits of position-sensitive photodiodes

Area of Science:

• Optics and Photonics
• Quantum Metrology
• Optical Sensing

Background:

• Split photodiodes and lateral effect photodiodes are common detectors for optical beam displacement measurement.
• These detectors are often considered interchangeable for small Gaussian beam displacements.
• Signal quality is crucial, particularly in low-noise environments dominated by fundamental shot noise.

Purpose of the Study:

• To theoretically and experimentally compare the signal-to-noise ratio (SNR) of lateral effect photodiodes and split photodiodes.
• To investigate detector performance in the shot-noise-limited regime for Gaussian beam displacement.
• To assess the practical viability of lateral effect photodiodes considering their thermal noise.

Main Methods:

• Theoretical analysis of photodiode responses to Gaussian beam displacement.
• Experimental measurements of beam displacement using both detector types.
• Analysis of signal-to-noise ratio under low technical noise conditions, focusing on shot noise.

Main Results:

• Lateral effect photodiodes demonstrate a superior signal-to-noise ratio compared to split photodiodes.
• This advantage is attributed to the optimal spatial response of the lateral effect photodiode.
• The quantum advantage persists even when considering the intrinsic thermal noise of the lateral effect photodiode.

Conclusions:

• Lateral effect photodiodes provide a quantum advantage in SNR for beam displacement sensing over split photodiodes.
• This improved performance is significant in shot-noise-limited scenarios.
• The practical application of lateral effect photodiodes is feasible for enhanced optical metrology.