Semiconductor lasers, also known as laser diode (LD), are one of the most recent developments in semiconductor physics in the 1980s. The advantages of semiconductor lasers are: small volume, lightweight, good reliability, long service life, and low power consumption. In addition, semiconductor laser adopted low voltage constant current power supply mode, hence provided low powder failure rate, safe operation, and low cost of maintenance. Currently, semiconductor laser is the most popular laser. It has gradually replaced other type of lasers in some important applications. Besides, there are many types of semiconductor lasers, including infrared and red lasers with long wavelength and green and blue lasers with shorter wavelength, which can be used to expand the measurement range of laser particle size meter and improve the measurement precision.
The laser performance of early semiconductor lasers was greatly affected by temperature, and the beam's divergence Angle was also large (below 20 degrees), so the performance in directionality, monochromaticity, and coherence was not ideal. With the rapid advancement of semiconductor laser technology, its performance has reached a very high level, with a significant improvement in the quality of laser beam as well. Therefore, semiconductor lasers are used as laser source in most brands of laser particle sizing instruments worldwide.
When using semiconductor lasers as laser source, constant current and constant temperature must be utilized in the control electric circuit to ensure stable output power.
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