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Application of high-precision voltage source in semiconductor laser test

发布:2021-01-14

Semiconductor lasers are the core components in the fields of optical fiber communication, laser display, gas detection, etc., and have received extensive attention from scientific and technological personnel around the world. In the production and research and development process of semiconductor lasers, the measurement of the optical and electrical characteristics of the laser is particularly important, and it is a key link to control the stability of the laser preparation process and the reliability of the laser performance.

Semiconductor lasers are semiconductor photoelectric conversion devices. As shown in Figure 1, a semiconductor laser is composed of multiple layers of materials. From bottom to top, it includes a back electrode, a substrate, a lower light confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an upper confinement layer, and an upper electrode. The different layers are composed of different epitaxial materials. Such a layered structure is to achieve (1) the injection of carriers (electrons, holes) to recombine light emission, (2) the lateral restriction of photons to form an optical waveguide. The layered structure completed by epitaxy undergoes an etching process to form a ridge waveguide, and a contact electrode is prepared on the ridge waveguide.

The purpose of such a ridge waveguide: (1) limit the lateral diffusion of current, (2) form a lateral waveguide for photons. The prepared wafer undergoes cleavage, coating, welding, and bonding of leads to obtain the laser to be measured, as shown in 2. When a current is injected into the laser electrode, a large number of electrons and holes on both sides of the PN junction of the laser flood into the active area, where the electron-hole pairs recombine in the active area, and a large number of photons are generated. The photons move along the axis under the action of the waveguide. Propagation, at the end of the laser, the reflected light forms the lasing condition, and the transmitted light is the laser output from the laser.

The operating characteristics of the laser are mainly reflected in (1) PN junction characteristics, series resistance, (2) laser lasing threshold, and laser slope efficiency. These characteristics determine the laser output power, power conversion efficiency, working life and other properties. PIV measurement methods are often used to obtain these important parameters during production and scientific research.

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Chart 1 Laser structure chart chart chart            Chart 2 Laser microscope photo

The ATS-2000V series is a high-precision, high-stability voltage output voltage source. The maximum output voltage is 200V, the minimum voltage resolution can reach 2μV, the output accuracy is high, and the noise is low. The operation panel LCD display is simple and easy to understand and easy to operate. The system has simple structure, high precision, good reliability, and fast speed, which improves the production efficiency while increasing the test accuracy and reliability, reducing the cost of a large number of tests. The integrated PIV system is mainly composed of ATS-2000V dual-channel precision source measurement unit SMU, integrating sphere, fixture and software. One channel of the ATS-2000V is used as the current source of the laser to simultaneously measure the voltage V of the laser. The laser light of the LD is coupled into the integrating sphere, and the integrating sphere detector is converted into a photocurrent into another channel of the ATS-2000V high-precision voltage source. The photocurrent measured by the ATS-2000V is multiplied by the power current of the integrating sphere detector. The coefficient is the output power of the laser. B2900A is connected with PIV measurement software via USB port to complete measurement control and data acquisition.

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The scalability of the integrated PIV system is also its outstanding advantage in the field of semiconductor laser research and development. The hardware part of the integrated PIV system, including the ATS-2000V precision measurement unit, the measurement platform, is connected to the computer by GPIB or USB ports. Therefore, the hardware part of the integrated PIV system can cooperate with the test software program written by the user through the National Instrument and other software platforms to complete the more complex measurement tasks required by the user.

During the production and research and development of semiconductor lasers, a large number of PIV tests must be performed on semiconductor laser chips. Compared with the traditional discrete and complex PIV test system, the PIV test system integrated with the ATS-2000V precision measurement unit has the advantages of simple system structure, convenient operation, high precision, strong reliability, and rapid measurement, which greatly reduces the PIV performance measurement of the laser chip. The operating cost, time cost, and the flexibility of PIV measurement are increased. The ATS-2000V high-precision voltage source will be widely used in the fields of semiconductor laser production and scientific research.

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