The Study Of All-solid-state Passively Q-switched Laser Based On Novel Saturable Absorbers

The Diode-pumped all-solid-state laser (DASSL) is a kind of laser device that all of the components are made by solid materials, such as the solid gain medium and the semiconductor pump source. DASSL have been widely used in the fields of industry and military, owning to their considerable advantages like high output conversion efficiency, good reliability and low-cost. Recently, the short pulse laser technology has attracted a lot of attention. All solid Q-switched laser realized by saturable absorbers was widely used in the laser communication, fine machining, and researching of micro world. On the other hand, the laser output performance of the passively Q-switched laser is greatly influenced by the saturable absorbers. For novel saturable absorbers, they usually have merits such as short response time, wide absorption wavelength, low optical loss and strong nonlinear effect. The performance of these kinds of novel saturable absorbers has attracted widespread attentions. A large number of research have been made to optimize the output characteristics of all-solid Q-switched lasers.In this paper, we used single-walled carbon nanotubes (SWCNT) solution and Bi-doped GaAs as saturable absorbers, realized the stable output Q-switched laser in 1μm and 2μm wavelengths, respectively. GaAs semiconductor material has already been used as saturable absorber in passively Q-switched lasers. However, the research about Q-switched laser with GaAs saturable absorber in 2μm wavelength has not been reported yet. We demonstrated the diode pumped passively Q-switched Tm:LuAG laser with Bi-doped or undoped GaAs wafer as saturable absorber. The Bi-doped GaAs wafer was obtained by ion implantation method. On the other hand, SWCNT saturable absorber has the advantages of wide absorption spectrum, good thermal conductivity, high damage threshold and rapid recovery time. We successfully fabricated the reticular ordered SWCNT solution by the liquid phase configuration method. We used the SWCNT solution as the saturable absorber, realized the stable running of all-solid Q-switched laser. At the same time, we detected and analyzed the laser output characteristics. The main study contents of this dissertation are shown as below:(a) We introduced the applications of GaAs in passively Q-switched laser at 2 μm wavelength. During the fabrication of Bi-doped GaAs wafer, the ion implantation method and rapid thermal annealing treatment was introduced and used in our experiment. After that, we presented the performance of 2μm Tm:LuAG laser with Bi-doped GaAs or undoped GaAs as saturable absorber. We measured and compared the laser output characteristics experimentally. The results confirmed that GaAs have good saturable absorption ability and can behave as saturable absorber in 2μm wavelength. At the same condition, the output parameters generated by Bi-doped GaAs are much better when compared with the referenced GaAs sample.(b) Firstly, the fabrication methods of the reticular ordered SWCNT was introduced. We used a kind of nonionic surfactant to help the aligning process during the dispersion of the carbon nanotube powder. When dissolved in aqueous solution, the self-assembly characteristic of the surfactant will benefit to the fabrication of reticular ordered SWCNT solution. After that, we achieved the diode-pumped passively Q-switched Nd:YVO4 laser with reticular ordered SWCNT solution and untreated referenced SWCNT solution as saturable absorbers. Experimentally measured and compared the laser output characteristics of the two different samples. The results indicated that several good effects on the absorption characteristics can be brought by the reticular configuration of the SWCNT solution.