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Investigation Of Eye-safe Laser And Supercontinuum Generation

Posted on:2016-05-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:H N ZhangFull Text:PDF
GTID:1108330461484413Subject:Optical Engineering
Abstract/Summary:Request the full-text of this thesis
Lasers operating in the wavelength region of 1.4-2.1 μm have a high water absorption coefficient, it has high eye damage threshold power, therefore, it has an eye-safe characteristic. Eye-safe lasers have many important applications in the fields of laser radar, laser ranging, laser medicine, optical communications and pumping source.The most simple method for obtaining eye-safe laser is directly pump different ion-doped laser media, such as 1.5-1.6μm eye-safe laser can be obtained by pumping Er-doped gain media, also,1.9-2.1 μm eye-safe lasers can be got by pumping Ho or Tm-doped laser gain media. Additionally, by pumping Nd-doped laser gain media, we can get 1.4 μm eye-safe lasers, μm, Ho or Er doped laser gain media have commonly used for obtaining eye-safe lasers. However, due to the small stimulated emission cross section and the lower ion efficiency, there are rarely researches on using Nd-doped laser gain medium for obtaining 1.4 μm eye-safe laser reporting. Since the output wavelengths of solid-state lasers relied on the energy level transitions in the ions, the wavelength maybe restricted. Therefore, in order to meet the desire for the new laser frequency. Nonlinear frequency conversion technology has become an effective means for obtaining new laser frequency.Stimulated Raman scattering (Stimulated Raman Scattering, SRS) is an important way to develop new laser frequency components based on the existing frequency, new laser frequency depends on the frequency of the pump light and Raman frequency shift of the Raman medium, so reasonable combination of the wavelength of pump light and the Raman medium frequency shift laser wavelengths form ultraviolet to near-infrared can be obtained. Meanwhile, Solid-state Raman laser have the advantages of small size, high efficiency, good stability and so on.Sometimes, in order to meet the requirements of particular laser wavelength in many scientific fields, single non-linear effect is difficult to meet the requirements, then combining a variety of non-linear effects for generating new frequency component becomes important. Supercontinuum generation is obtained under the affections of a variety of non-linear effects such as self-phase modulation (Self phase modulation, SPM), cross-phase modulation (Cross phase modulation, XPM), four-wave mixing (Four wave mixing, FWM) and stimulated Raman scattering (Stimulated Raman Scattering, SRS). It has a wide spectral coverage, high output power, spatial coherence and other characteristics. So far, supercontinuum generation is the most efficient way for obtaining new frequencies.In this dissertation, we mainly investigated three aspects. First, we experimentally studied the performance of 1.4 μm eye-safe laser by employing different Nd-doped laser gain media. Secondly, based on BaWO4, SrWO4, and YVO4 Raman media, we have studied the characteristics of the 1.6 μm eye-safe Raman laser. Thirdly, we studied the characteristics of the supercontinuum in photonic crystal fibers. The concrete research contents of this thesis are as follows.1. By employing Nd:YAG ceramic as laser gain media, we have demonstrated an eye-safe laser operation at the wavelength of 1442.8 nm, when the pump power was 20.3 W, the output power of as high as 3.96 W was obtained, corresponding to an optical-to-optical efficiency of 19.1%.2. We have demonstrated a LD-end pumped Nd:GGG eye-safe laser operation at the wavelength of 1423.4 nm, the output power was 3.63 W and the optical-to-optical efficiency and the slop efficiency are 19.6% and 26%,respectively.3. by employing Nd:KLu(WO4)2 crystal as laser gain medium, a 1425 nm laser operation was obtained, when the pumped power was 9.6 W, the output power was as high as 1.57 W, corresponding to an optical-to-optical efficiency of 16.4%.4. We have studied the performance of the passively Q-switched Nd-doped 1.4 μm eye-safe laser by employing V3+:YAG, Co:LMA and graphene as saturable absorber. The highest output power of 1.53 W was obtained by employing V3+:YAG as saturable absorber, in addition, the biggest pulse energy of 53 μJ was obtained when the Co:LMA used as saturable absorber. When the graphene used as saturable absorber, the pulse width was 610 run.5. An intracavity ceramic Nd:YAG/BaWO4 Raman laser operating at 1666 nm have been demonstrated. When the pump power was 20.3 W and the pulse repetition frequency is 5 kHz, the output power was as high as 1.21 W, corresponding to an optical-to-optical efficiency of 6%, the output power and the optical efficiency are all the highest of a 1.6 μm Raman laser.6. An intracavity ceramic Nd:YAG/YVO4 Raman laser operating at 1657 nm have been demonstrated. When the pump power was 19.6 W and the pulse repetition frequency is 20 kHz, the output power was as high as 651 mW, the corresponding an optical-to-optical efficiency is 3.3%.7. An intracavity ceramic Nd:YAG/SrWO4 Raman laser operating at 1664 nm have been demonstrated. When the pump power was 27.7 W and the pulse repetition frequency is 25 kHz, the output power was as high as 1.16 W, the corresponding an optical-to-optical efficiency is 4.2%. The biggest pulse energy and the highest pulse peak power was 46.6 μJ and 9.3 kW, additionally,9.3 kW is the highest peak power of a 1.6 μm Raman laser.8. By employing SrWO4 as a Raman active medium, an efficient eye-safe dual-wavelength Raman laser-operating at 1501 and 1526 nm has been demonstrated. A maximum total output power as high as 3.36 W is obtained under a pump power of 33.3 Wand a pulse repetition frequency (PRF) of 30 kHz, corresponding to an optical-to-optical conversion efficiency of 10%. To our knowledge,3.36 W is the highest output power of a 1.5 μm eye-safe Raman laser.9. We have studied the laser performance of the supercontinuum generation obtained by pumping photonic crystal fiber with single zero-dispersion wavelength with a picosecond fiber laser. When the pump power was 10 W, the maximum output power was 2.8 W, the spectrum ranged from 750 nm to 2000 nm.10. We have studied the laser performance of the supercontinuum generation obtained by pumping photonic crystal fiber with two zero-dispersion wavelengths with a picosecond fiber laser. When the pump power was 10 W, the maximum output power was 1.09 W, the spectrum ranged from 750 nm to 1650 nm.11. By cascading a dual zero-dispersion-wavelength photonic crystal fiber with a single zero-dispersion-wavelength photonic crystal fiber, ultra-flat supercontinuum generation spectrum at 3 dB level from 1070 up to 1630 nm (560 nm) and 6 dB bandwidth of 690 nm (960-1650) without the redundant pump wavelength are obtained, to our knowledge, the 3 dB bandwidth of 560 nm is the most flat supercontinuum generation obtained in photonic crystal fibers. The main innovations of this thesis are summarized as follows:1. For the first time, an Nd:YAG ceramic laser oprating at 1442.8 nm was demonstrated, the maximum output power was 3.96 W, and the optical-to-optical efficiency was 19.1%.2. For the first time, an Nd:GGG laser oprating at 1423.4 nm was demonstrated, the maximum output power was 3.63 W, and the optical-to-optical efficiency was 19.6%.19.6% is the highest optical-to-optical efficiency of a 1.4 μm eye-safe laser.3. For the first time, an Nd:KLu(WO4)2 laser oprating at 1425 nm was demonstrated, the maximum output power was 1.59 W, and the optical-to-optical efficiency was 16.4%.4. For the first time, graphene was used as SA for a 1.4 μm eye-safe laser, the pulse width was 610 ns.5. The intracavity pumped BaWO4 Raman laser operating at 1666 nm was realized for the first time.When the pump power was 20.3 W and the pulse repetition frequency is 5 kHz, the output power was as high as 1.21 W, corresponding to an optical-to-optical efficiency of 6%, the output power and the optical efficiency are all the highest of a 1.6 μm Raman laser.6. The intracavity pumped YVO4 Raman laser operating at 1657 nm was realized for the first time. When the pump power was 19.6 W and the pulse repetition frequency is 20 kHz, the output power was as high as 651 mW, the corresponding an optical-to-optical efficiency is 3.3%.7. The intracavity pumped SrWO4 Raman laser operating at 1664 nm was realized for the first time. The biggest pulse energy and the highest pulse peak power was 46.6 μJ and 9.3 kW, additionally,9.3 kW is the highest peak power of a 1.6 μm Raman laser.8. in a cascading photonic crystal fiber, when the pump power was 10 W, ultra-flat supercontinuum generation spectrum at 3 dB level from 1070 up to 1630 nm (560 nm) and 6 dB bandwidth of 690 nm (960-1650) without the redundant pump wavelength are obtained, to our knowledge, the 3 dB bandwidth of 560 nm is the most flat supercontinuum generation obtained in photonic crystal fibers.
Keywords/Search Tags:Eye-safe, Solid-state Raman laser, Solid-state laser, BaWO4 crystal, SrWO4 crystal, YVO4 crystal, Nd:YAG ceramic, Nd:GGG crystal, Nd:KLu(WO4)2 crystal, Supercontinuum generation, Photonic crystal fiber, cascaded fibers
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