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Laser is a device capable of emitting laser. The invention of laser science and technology in the 20th century, a major achievement. 1916 Einstein proposed the concept of stimulated emission is an important theoretical basis, the so-called stimulated emission is: material particles in high-energy state, when subjected to an energy equal to the energy state and sub-state energy of the difference between energy photons, the particles will be converted into secondary energy state, while the release of the second photon, and a photon is emitted together. This radiation received light output is amplified, and is coherent light, i.e. as a plurality of photon emission direction, frequency, phase, polarization identical. The rise of laser science and technology to make human understanding and use of light reached a new level. Conventional lasers working medium according to their classification, including: gas lasers, solid-state lasers, semiconductor lasers, liquid lasers, and free electron lasers. The semiconductor laser can not be compared with the characteristics of other lasers, such as: common with He-Ne laser excitation, high voltage excitation (about 1500V) and the semiconductor laser 2-3V low voltage excitation, compared to the semiconductor laser excitation means safer, and more efficient than conventional lasers excite the high number of times. In some measuring instrument, the selection of the semiconductor laser lighting, to meet good color, good coherence, high beam collimation requirements. In the long-distance communications, laser radar, digital signal storage and recovery, laser ranging, robots, holographic applications, medical diagnostics and so have a wide range of applications. However, in practical applications, the laser has a low noise requirements, high stability and other characteristics, because the drive current fluctuations, will not only cause the laser of the laser intensity noise, will result in the output wavelength of the spectral linewidth broadening. Addition to a stable current, but also the need for the laser diode temperature precise control. Laser light source in the process of stimulated emission laser, stimulated source for temperature sensitive, temperature changes will affect the emission spectra and output power. Generally 1 degree Celsius change in temperature, the wavelength change 0.2 ~ 0.3nm. This paper presents a relatively complete function semiconductor laser system, enabling the current source drive and protection, optical power feedback control, temperature control, and error alarm function, the whole system is controlled by the MCU. Current source drives can achieve APC (Automatic Power Control Steady) and ACC (automatic steady current control) mode, constant temperature control system through the precision adjustment through TEC (Thermo Electric Coolers) of the current size and orientation, and with thermistor feedback and PID algorithm to achieve the laser operating ambient temperature control.
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