A semiconductor laser is a kind of laser that matures earlier and progresses faster. It uses the mirror surface formed by the cleavage plane of the semiconductor crystal as a resonant cavity to amplify the light oscillation, feedback, and light generated by the light, and output the laser with a wide wavelength range. The utility model has the advantages of simple production, low cost, small volume, light weight and long service life. Therefore, the variety has developed rapidly and has a wide application range, and has more than 300 kinds.
Compared with traditional lasers, design and construction mode tunable lasers are one of the most important research tasks, and an effective way to expand the range of laser applications. At present, the R&D personnel regulate the laser mode structure through semiconductor energy band engineering, the self-absorption effect of the material itself, and the Burstein-Moss (BM) effect under the participation of plasmons. However, these methods of modulation are not reversible, and the implementation of dynamic, sustainable laser mode structures still lacks effective research protocols.
Recently, Wang Zhonglin, Pan Caofeng and Lu Junfeng of the Institute of Nano-Energy and Systems, Chinese Academy of Sciences, organically combined the piezoelectric properties of the ZnO optical microcavity and its laser mode, and the ionic polarization inside the ZnO cavity crystal generated by external mechanical strain. Change the refractive index to achieve dynamic control of the coherent laser.
ZnO has a large bandgap and exciton binding energy, high transparency, and excellent room temperature luminescence. At room temperature, excitons can be stably present in ZnO, which is an ideal material for achieving ultraviolet spontaneous and stimulated radiation at room temperature or higher, and is highly prominent in obtaining low-value, high-quality UV lasers. The intrinsic physical advantage. In addition, the non-centrosymmetric wurtzite structure ZnO micro/nano material also has special piezoelectric properties. When the material is subjected to external stress, the ionic polarization inside the crystal causes the dielectric constant of the medium to change, which is effective for the refractive index of the material. Regulation.
It is understood that the researchers systematically analyzed the influence of strain on the refractive index of ZnO, established the correspondence between strain and mode movement, and obtained super-precision stress sensing, which is spontaneous compared with the energy band caused by the piezoresistive effect. The spectral resolution of the radiation spectrum is increased by an order of magnitude.
The research results provide an effective method for dynamically regulating coherent light sources, and provide a new idea for developing a color-resolved stress sensing component.
By-pass assembly has two positions; by-pass and close. It is in by-pass position during trip operation, and circulates mud fluid in the drill string into the annular space by-passing the idle motor, so that no mud may spray out onto the platform during the trip operation. When mud flow rate and pressure reach the setting value, the valve stem moves down and closes the valve. Meanwhile, mud stream flows through the motor, and converts the pressure energy into mechanical energy. As mud flow rate is too low, or mud pump stops, and as the pressure produced is not enough to overcome the spring force and the static friction force, the spring presses the stem upward, and by-pass is in open position. In general, the cross-over subs are used in deep well, large angle well, horizontal well or when hollow rotor is selected.
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