Investigation On Laser Source Of Micro-projector

Laser show is a new type of display technology,compared with other display technology,It has high color saturation, any screen display, such as the superiority of unparalleled。The research of the all-solid-state red, green and blue laser light source is the key to achieve laser display technology. In this paper ,We study the semiconductor-pumped all-solid-state red, green and blue lasers comprehensivly. At the same time, according to the color theory, RGB color lasers will be synthesized to white laser . This paper contains the following two aspects:Ⅰ,The Investigation on Semiconductor-pumped all-solid-state red, green and blue lasers(1) All-solid-state micro -red laserThe light source is semiconductor laser diode whose output power is100mW of the Beijing HI-Tech company , Single-mode, In the room temperature ,the diode emissions Center wavelength of 650nm red light, I th? 80mA,I op?1 70mA,After the red light traverses the optical coupling system, the output laser is parallel light. The experimental schematic diagram is displayed in Figure 1.We research the micro-red lasers experimentally, when we change the input current ,We measured the output power of 650nm red light ,as well as the effects of laser power 650nm when we change the LD temperature, The experimental results are displayed in Figure 2,3. By the curve of Figure 2, we can see the red light output power increases as the input current increase, although it is not completely linear change, However, the output power is stable.when the room temperature is20°C, the output power is120mW stablely. When the input current is 170mA, we changes temperature of LD by temperature controller,we can see the curve of Figure 3, the Red light output power is insensitive of the temperature. However, between 19°C 21°C , the output power is maximum.,and the output power is stable about 125mW. Good quality laser beam, micro-structure, smaller than 3 cubic centimeters.(2) All-solid-state micro -green laserThe light source is semiconductor laser diode whose output power is 500mW of the Beijing HI-Tech company.In the room temperature ,the diode emissions Center wavelength of 808nm light, the output light traverses the self-focusing lens,laser crystal ( Nd :YVO₄ )and frequency-doubling crystal(KTP), we coate at the crystal face directly composing the laser cavity. The output light is 532nm. The frequency characteristics of KTP crystal is in Figure 4,5.By the theoretical simulation of the frequency curve of KTP crystal,in the experiment,we have taken the phase-matching angle of KTP crystal areθ= 90°,φ= 23.5°, the experimental schematic diagram is displayed in Figure 6.We research the micro-green lasers experimentally, at room temperature t = 20°C,We measured the relationship between the green output power and the input current, the models of the Laser Energy Meter is LPE-1B. The experimental results are Shown in figure 7.By the curve of Figure 2, we can see the green light output power increases as the input current increase, although it is not completely linear change, However, the output power is stable, in the Experiment ,we control the input current at 450mA,the temputer of Nd :YVO₄ and KTP is 20oC, We measured the variety of 532nm laser power,when we change the temperature of LD. The experimental results are Shown in figure 8. when the LD temperature is maintained at 20°C, the input current is 450mA, we changes the temperature of Nd :YVO₄ and KTP by temperature controller, we Measured the effects of 532nm laser power when the temperature change , as shown in Figure 9. From the Figure 8 ,we can see the laser output power is in the larger changes,When we Change the temperature of LD, especially at higher temperature, the power dropped a lot, so temperature control is carried out on the LD is very necessary. From the Figure 9, we can see the temperature of Nd :YVO₄ and KTP have a great impact on the green output power, there are two obvious maximum in the power curve, They are possible because of the corresponding temperature of the role of KTP crystal wasλ/ 4, which made the two lines through its polarization-based optical frequency to maintain the original direction of polarization, when the light once traverse the Nd :YVO₄ crystal ,the Nd :YVO₄ crystal achieves largest crystal gain, and thus greater output power.In the experiments ,we chose the phase-matching temperature is 19 o C ,λ=808nm,at this temperature, we see the Nd :YVO₄ and KTP as a whole, When the input current is 450mA, we control the temperature of Nd :YVO₄ and KTP with one temperature controller,we measure the polarization degree is 2:1, From our laser structure, frequency-doubling principle, etc., we analyse the result of the lower polarization degree is the effect of the Nd :YVO₄ crystal.We developed a high-performance and low-cost micro-green laser,when The Light source power is 500mW, when the input current is up to 500mA, the green Laser output power is 80mW and the laser output power is stability.(3) All-solid-state micro -blue laserThe light source is semiconductor laser diode whose output power is 2W of the Beijing HI-Tech company, In the room temperature ,the diode emissions Center wavelength of 808nm light, the output light traverses the self-focusing lens,laser crystal ( Nd :YAG )and frequency-doubling crystal( BIBO ), the output light is 473nm, The frequency characteristics of BIBO crystal is in Figure 10,11.By the theoretical simulation of the frequency curve of BIBO crystal,in the experiment,we have taken the phase-matching Cutting angle of BIBO crystal areθ= 161.7°,φ= 90°,the experimental schematic diagram is displayed in Figure 12. We research the micro-blue lasers experimentally, at room temperature t = 20°C,We measured the relationship between the blue output power and the input current, the models of the Laser Energy Meter is LPE-1B. The experimental results are Shown in figure 13.By the curve of Figure 13, we can see when the pump power is 2W,the maximum blue output power is 75mW, the Conversion efficiency is 3.75%. We developed a high-performance and low-cost micro-blue laser,when The Light source power is 2W, the blue Laser output power is75mW and the laser output power is stability.Ⅱ,micro -red, green and blue lasers compose white laser systemWe have obtained micro -red, green and blue lasers, analysis the theory of Color matching, We have calculated that whenλ=650nm,532nm,473nm, those power ratio is 3.008:0.8524:1,we can obtain white laser. In the experiment we made the power ratio is 3:1:1,the 650nm Red laser power is 120mW, the532nm Green laser power is 40 mW, the 473nm Blue laser power is 40 mW, we obtain the white-light laser source for the micro-projector, as shown in Figure 14. We research the micro-white lasers experimentally, at room temperature t = 20°C ,we can see the maximum white output power is 195mW, and the output power is stable.