Investigation of the peak power enhancement available from a surface emitting GaAlAs near-infrared light emitting diode by cooling and pulsing

摘要

Light emitting diode (LED) light sources are required for many illumination and optical sensing applications, due to their compact dimensions, low cost and low power consumption. The optimization of optical power output in a specific wavelength band is often of critical importance. We are interested in using LEDs for optical sensing systems, particularly for gas sensing. We have conducted a very comprehensive engineering study to show that, by packaging a commercial surface emitting LED in a cooled heat-sunk package and optimizing the drive current for this lower temperature, the power from the LED may be substantially improved, particularly when pulsed at low duty cycle. We have found that, even with moderate cooling using a Peltier heat pump, the intensity in our required spectral band was improved by a factor of 5 compared to that attainable under normal drive conditions. We have also verified that almost all spectral changes in the LED were due to temperature changes in the emitting chip, rather than from other effects related to injection current, such as internal optical gain.