Performance Evaluation of Green and Red Lasers in Long-Distance Optical Sensing Using Light Dependent Resistors

Abstract

This study compares the performance of green (532 nm) and red (650 nm) lasers in optical sensing applications using Light Dependent Resistors (LDRs), focusing on their effectiveness for long-range light intensity detection in environments like bathymetry and surrogate sediment monitoring. The experiment measures resistance changes in LDRs exposed to both wavelengths at incremental distances (1m, 2m, 3m, 4m, and 5m) under controlled laboratory conditions. The key objective is to assess the spectral sensitivity and photoconductivity efficiency of the LDRs with each laser wavelength, providing insights into the optimal laser choice for long-distance sensing systems. The results indicate that green lasers exhibit superior sensitivity compared to red lasers, as evidenced by consistently lower resistance values at all tested distances. This performance advantage is attributed to green light’s higher photon energy and reduced scattering and absorption losses in air and other media, which enhance electron excitation in the semiconductor material of the LDR. These findings align with previous studies suggesting that green light performs better in turbid media, such as sediment-laden water, where precise light transmission and detection are critical for accurate measurements. This comparison is crucial for the design of optical systems used in environmental monitoring and water resource management, where accurate, long-distance light intensity detection is essential. The research highlights the importance of selecting the appropriate laser wavelength to improve the efficiency and reliability of optical sensing technologies, particularly in challenging aquatic environments. The study’s findings provide a foundation for the optimization and calibration of laser-based systems in applications like surrogate sediment monitoring and bathymetric mapping, where maintaining signal strength over long distances is vital. Future work could explore the impact of environmental factors on photodetector efficiency to further advance optical sensing technologies.