| Laser display is the fourth generation display technology following black and white display,color display,and digital display.Red,green and blue lasers are used as light sources in a laser display.It has competitive advantages in color,service life,brightness,ultra-high-definition display,ultra-large-screen display,energy conservation and environmental protection.It has wide applications and great market potential.At present,the research level of laser display in China is close to that of foreign countries,and it has been at the forefront of industrialization of laser display.The market of laser display in China has already begun to take shape.It is expected to realize a curve overtaking in the display field and become one of the core competitiveness of China in the field of display.However,there are still some problems in the process of development.At present,there are two main bottlenecks,which can't be independently obtained by China.First,the chip of laser display is currently mainly monopolized by Texas Instruments in the United States and Sony in Japan.Second,semiconductor laser sources in laser display are mainly dependent on Mitsubishi and Nichia in Japan.We mainly focus on the second problem.Combined with our laboratory conditions,we take the new light source of laser display as the main research content of the dissertation,and explore the feasibility of using fiber lasers as the light source of laser display.We hope to realize the vision of self-sufficiency of light source for laser display as soon as possible.The main research contents and results of the dissertation are as follows:1.In order to meet the needs of laser synthesis and speckle reduction of laser display,we focus on the research of noise-like square pulse in fiber laser.In a compact linear cavity,nonlinear polarization rotation(NPR)mode locking is realized by using a polarization beam splitter(PBS).A noise-like square pulse with adjustable pulse width is obtained.When we increase the pump power up to 338.5 mW,the pulse width can be increased from 2.92 ns to 12.06 ns,and the amplitude of the noise-like square pulse can keep constant.Through measurement,the maximum average output power of the proposed laser is 75.4 mW,and the maximum pulse energy is 20.87 nJ.The slope efficiency is 23.69%.In addition,the characteristics of noise-like square pulse under different dispersion conditions are further studied.Utilizing chirped fiber Bragg grating(CFBG)for dispersion management,two kinds of noise like square pulses with different shapes are obtained in normal dispersion region and anomalous dispersion region,respectively.The pulse width can be expanded from 1 ns to 5.5 ns.In the normal dispersion region,the top of the noise-like square pulse is flatter,and the maximum pulse energy is higher,up to 40.17 nJ.In the anomalous dispersion region,the slope efficiency of the laser is higher,about 20.5%.Because PBS is also used as the output coupler,the laser is linearly polarized,and the degree of polarization(DOP)is more than 98%.In addition,an amplitude-adjustable noise-like square pulse is also obtained by adjusting the polarization controller(PC)during the experiment.2.In order to further take the advantages of large color gamut of laser display,a multi-primary laser display needs to be established,which requires the development of new laser sources of laser display with different wavelengths.Due to the Raman scattering effect in fiber lasers,the selection of wavelength of the laser source can be expanded.Based on the research of mode-locked fiber laser,a low-threshold cascaded Raman fiber laser in the 1.0 ?m band has been achieved.Under the low-threshold pumping condition of 260.5 mW,a third-order Stokes has been obtained.The wavelength range of cascaded Raman mode-locked fiber laser is up to 220 nm and the pulses are noise-like Raman pulses.The maximum output average power is 119.3 mW(maximum pump power:316 mW),the maximum pulse energy is 63.97 nJ,and the slope efficiency is high to 41.7%.In order to obtain lasers with different wavelengths,we have compared the filtering effects of the two different filters,and their center wavelengths are 1030 nm and 1080 nm,respectively.3.We can reduce speckle in the laser display by destroying the coherence of the laser source,and the coherence can be destroyed by adopting multi-wavelength laser sources.The semiconductor saturable absorption mirror(SESAM)is employed to realize the mode-locking operations,and the cascaded polarization maintaining fiber Bragg gratings(PM-FBGs)are used as wavelength-switchable elements.Four switchable single-wavelength and two switchable dual-wavelength mode-locked pulses are achieved at 1061 nm and 1064 nm.In addition,through temperature control,we obtain tunable single-wavelength and dual-wavelength mode-locked pulses.4.In order to apply the fiber laser mentioned before to the laser display light source,it is necessary to obtain a visible light source through amplification and nonlinear frequency conversion.So,based on the Master Oscillator Power-Amplifier(MOPA)structure,we establish a 1.0 ?m fiber optic amplifier.Eventually,we obtain green laser by second harmonic generation.Highlights of the dissertation are as follows:1.It is the first time to achieve NPR mode locking by using PBS in a linear cavity laser,and to obtain a noise-like square pulse with adjustable pulse width and height.Through dispersion management,we also obtain noise-like square pulses in the same laser cavity in the normal dispersion and anomalous dispersion regions.If the noise-like square pulse is applied to the laser display,it can not only facilitate laser synthesis but also reduce speckle noise.2.Under the low-threshold pumping condition,due to the Raman scattering effect,the multi-orders Stokes wave in the 1.0 ?m band is obtained in the mode-locked fiber laser,and its wavelength range is up to 220nm.Through suitable filtering,laser sources with different wavelengths are obtained.After nonlinear frequency conversion,it can meet the needs of three-primary and multi-primary laser display,and it can maximize the advantages of large color gamut of laser display.3.Two cascaded PM-FBGs are used as wavelength-switchable elements.Four switchable single-wavelength and two switchable dual-wavelength mode-locked pulses are achieved at 1061 nm and 1064 nm.Besides,through temperature control,the tunable single-wavelength and dual-wavelength mode-locked operations are achieved in the proposed laser.If the multi-wavelength lasers are applied to the laser display,it can reduce the speckle contrast by reducing the coherence of the laser source. |
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