Laser has been widely used since its invention, among which semiconductor laser is the most rapid development. Semiconductor lasers have the advantages of wide wavelength range, small size, light weight, good reliability, long service life, low power consumption, low cost, easy to mass production, etc. Because of the advantages mentioned above, it has been widely used. At present, more than 300 applications have been developed, including but not limited to laser ranging, laser radar, optical communication, laser simulation weapons, laser warning, laser guidance tracking, ignition and detonation, automatic control, detection instruments, all kinds of information scanning, etc.

In addition to the advantages mentioned above, the semiconductor laser has a disadvantage which is more prominent and relatively large impact on some application environment, that is, the performance of the laser is easily affected by the environmental temperature. In general, the influence of temperature on laser parameters is mainly shown as follows:

First, temperature can affect the output wavelength of the laser. When the current is constant, the wavelength of the laser increases about 0.1nm for every 1℃ increase in temperature.

Second, temperature can affect the output power of the laser. Temperature changes will result in a nonlinear relationship between power and current.

Third, temperature can affect the threshold current and the characteristic curve of the laser.

Fourth, temperature can affect the life of the laser. The sharp change of temperature will affect the output power and life of laser.

In order to control the working temperature of the laser and improve the performance of the laser while reducing the influence of temperature on the laser, we can try to design a temperature control design with NTC thermistor chip as the temperature measuring element and TEC as the temperature controlling element.

NTC thermistor chip is a sensitive electronic component which resistance value decreases with the increase of temperature. The temperature near the thermistor chip can be determined in real time by the change of its resistance value. TEC is a semiconductor refrigeration device based on the Peltier effect, which can form the conversion of hot and cold ends according to the current direction. According to the characteristics of these two components, TEC cooling or heating can be driven by the change of resistance value of NTC thermistor chip, so as to accurately control the temperature of the laser.

NTC thermistor chip adopts Wheatstone bridge. Through this circuit, the small change of resistance value of the thermistor chip can be converted into the output of the change of voltage difference. The voltage in different directions can be formed by comparing the preset voltage, and then the voltage difference can be amplified by the differential amplifier to drive TEC to work. This allows TEC to control heating/cooling based on real-time temperature changes of the NTC thermistor chip.

NTC thermistor chip for laser developed and produced by EXSENSE Electronics Technology Co., Ltd. are suitable for reflow welding, tin welding, gold and tin eutectic welding, gold/silver/copper bonding and other welding processes. NTC thermistor chip can also be printed with gold or silver electrodes, depending on customer requirements and application conditions.