CN101752773A - Laser head - Google Patents

Abstract

The invention relates to a laser head, comprising: a pump source, used to emit continuous laser light; a light splitting device, used to divide the continuous laser light generated by the pump source into two beams of pulsed pump laser light; and two laser resonant cavities , are respectively used to receive the two beams of pulsed pump lasers and alternately output pulsed lasers. The laser head of the present invention can fully dissipate heat, and can reduce the thermal gradient of the laser crystal and the thermal effect to the greatest extent compared with continuous lasers, thereby improving the electro-optic conversion efficiency and increasing the total output power of the laser; the two laser resonances in the present invention The laser output of the cavity is complementary in time, and compared with the pulse-modulated laser, the device of the present invention improves the time utilization rate of the pumping source; the device has low cost, simple operation, and is favorable for mass production.

Description

a laser head

technical field

The invention belongs to the field of lasers, in particular to a laser head for solid lasers.

Background technique

Solid-state lasers will produce thermal effects during work, including thermal lens effects, thermal-induced stress birefringence effects, and thermal depolarization effects. The generation of thermal effect will affect the output energy and working stability of the laser. Specifically, it includes the following points:

1. The temperature of the laser crystal will rise after absorbing heat in the process of optical pumping. The thermal stress of the corresponding laser crystal is proportional to the pump energy. When the pump energy increases and the maximum stress in the laser crystal exceeds the material damage limit, The laser crystal will break;

2. The thermal stress generated in the laser crystal will cause the change of the refractive index, so that the original isotropic medium becomes anisotropic, which is the thermal stress birefringence effect;

3. The end face of the laser crystal will be deformed during the optical pumping process, which is the thermal lens effect.

The thermal effect of solid-state lasers seriously hinders the further improvement of laser output efficiency and reduces the beam quality. In practice, necessary measures should be taken to suppress or reduce the thermal effect. There are usually several commonly used measures to compensate the thermal effect of optically pumped solid-state lasers, including cooling, light filtering, and optical compensation methods. The thermal effect of the continuous laser using the conventional cooling method has been reduced to a certain extent, but because the pump light is continuously pumped to the laser crystal, the heat cannot be released in time, the thermal effect is enhanced, and the heat accumulates in the laser crystal. A high thermal gradient will cause problems such as thermal effects or thermally induced stress birefringence effects, which will make the laser crystal absorb the pump light unevenly, resulting in low optical-to-optical conversion efficiency and low electro-optical conversion efficiency. For pulse-modulated lasers, although the heat accumulated by the pump light in the laser crystal can be released to a certain extent within the laser output interval, the time utilization rate of the pump source of the entire laser device is low, that is, When the pulse-modulated laser has no laser output, the electric energy of the pump source is lost, which reduces the electro-optical conversion efficiency of the system. To sum up, conventional solid-state lasers either have low electro-optic conversion efficiency due to the thermal effect of the crystal or low time utilization of the pump source. In short, it is difficult to achieve both simultaneously.

Contents of the invention

The invention provides a laser head capable of effectively reducing thermal effects and improving the time utilization rate of pumping sources at the same time. In addition, the present invention also provides a laser display light source made by using the above laser head.

In order to achieve the above object, the present invention provides a laser head, including: a pump source, used to emit continuous laser light; a light splitting device, used to divide the continuous laser light generated by the pump source into two beams of pulsed pump laser light ;as well as

The two laser resonators are respectively used to receive the two pulsed pump lasers and alternately output the pulsed lasers.

In the above technical solution, the pulsed pump laser is a periodic pulsed laser.

In the above technical solution, the pulsed pump laser is a pulsed laser in the form of a square wave.

In the above technical solution, the sum of the duty ratios of the two pulsed pump lasers is 100%, and the two pulsed pump lasers are alternately generated, and the duty ratio of any one of the lasers is between 25% and 75%. % range.

In the above technical solution, the light splitting device includes a polarization conversion element and a polarization splitting device.

In the above technical solution, the polarization conversion element is an electro-optic crystal or a Faraday rotator.

In the above technical solution, the frequency of the pulsed pump laser is 50Hz to 2KHz.

In the above technical solution, each of the two laser resonators includes a laser crystal, or the two laser resonators include a common laser crystal.

In the above technical solution, each of the two laser resonators further includes an output mirror, or the two laser resonators include a common output mirror.

In the above technical solution, each of the two laser resonators further includes a frequency doubling crystal, or the two laser resonators include a common frequency doubling crystal.

In the above technical solution, a coupling lens is respectively placed in front of the two laser resonators.

In the above technical solution, the laser head further includes a mirror for adjusting the direction of the optical path.

In the above technical solution, the laser head further includes a beam combining output device for combining the outputs of the two laser resonators.

In the above technical solution, the beam combining output device is a beam combining mirror, which is used to combine the outputs of the two laser resonators to obtain continuous laser output; the output frequencies of the two laser resonators are different.

The present invention also provides a laser display light source, including a light source group, a coupling lens group and an optical fiber bundle, characterized in that the light source group is composed of at least one laser head as described above;

The coupling lenses in the coupling lens group correspond to the output beams of the laser head one by one, and are used to respectively shape and couple the output beams of the laser head into corresponding optical fibers of the optical fiber bundle.

In the above technical solution, the number of coupling lenses in the coupling lens group is twice the number of the laser heads, and the number of fibers in the optical fiber bundle is equal to the number of coupling lenses in the coupling lens group.

In the above technical solution, the output ends of the optical fibers are fixed into a bundle by a fixing device.

Adopt above-mentioned technical scheme, have following beneficial effect:

Compared with the continuous laser, the two laser crystals of the present invention can dissipate heat better, and can better reduce the thermal gradient of the laser crystal and reduce the thermal effect. Furthermore, by adjusting the power supply to the preferred duty ratio range, the optical-to-optical conversion efficiency of a single laser can be significantly improved, thereby improving the electro-optical conversion efficiency of the overall device, and also improving the total laser output of the overall device. power. In addition, the laser outputs of the two laser resonators in the present invention are complementary in time, so that the whole device has laser output at any time. Therefore, compared with pulse-modulated lasers, the present invention improves the time utilization rate of the pump source. In addition, the device of the invention has low cost and simple operation, which is beneficial to large-scale production.

Description of drawings

Fig. 1 is a schematic structural view of a polarization splitting laser head according to Embodiment 1 of the present invention;

Fig. 2 is the first embodiment of the laser head of the present invention, when the s-polarized light component and p-polarized light component in the incident pump light are respectively 100%: 0, the voltage signal applied to the electro-optic crystal, the outgoing light passing through the electro-optic crystal The percentage of the s-polarized light component and p-polarized light component in the total power, and the relationship between the output power of the two laser crystals versus time;

Fig. 3 is the light-to-light conversion efficiency figure of s polarized light path in embodiment one;

Fig. 4 is a schematic structural view of a polarization splitting laser head according to Embodiment 2 of the present invention;

Fig. 5 is the second embodiment of the laser head of the present invention, when the s-polarized light component and p-polarized light component in the incident pump light are respectively 80%: 20%, the voltage signal applied to the electro-optic crystal, the output through the electro-optic crystal The percentage of the s-polarization component and p-polarization component in the incident light to the total power, and the schematic diagram of the output power of the two laser crystals changing with time;

FIG. 6 is a schematic structural diagram of a laser display light source according to Embodiment 3 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Embodiment one:

FIG. 1 shows a schematic structural diagram of a polarization splitting laser head in this embodiment. As can be seen from Fig. 1, the laser head includes a pumping source 112, a polarized light conversion element 101, a polarization splitting device 102, a first coupling lens 103 and a second coupling lens 113, a first laser crystal 105 and a second laser crystal 115, a mirror 108 , the first frequency doubling crystal 107 and the second frequency doubling crystal 117 , the first output mirror 106 and the second output mirror 116 . The optical path where the first laser crystal 105 is located is defined as a first optical path, and the optical path where the second laser crystal 115 is located is defined as a second optical path. The polarized light generated by the pumping source 112 is used as the pumping light of the first optical path and the second optical path. The polarization conversion element 101 is used to convert s-polarized light and p-polarized light. When certain conditions are met, the s-polarized light entering the polarization conversion element 101 becomes p-polarized light when it exits, and the p-polarized light entering the polarization conversion element 101 exits When it becomes s-polarized light; when the other condition is met, the polarization conversion element 101 does not work. The polarization splitting device 102 is used to spatially separate s-polarized light and p-polarized light to obtain two paths of pumping light, and the two paths of pumping light are respectively incident on the first light path and the second light path.

时(V_π为半波电压)，光束产生的位相差为

即偏振面发生90度的旋转。设置一周期方波电压信号的低电平为V₀(V₀＜V_M)，高电平为

将具有一定占空比的上述周期方波电压信号施加到电光晶体上，那么在低电平V₀的驱动下，泵浦源112发出的偏振光经过电光晶体后偏振面不发生旋转，在高电平V_M的驱动下，偏振光经过电光晶体后偏振面旋转90度，即进入电光晶体的s偏光出射时变成p偏光，进入电光晶体的p偏光出射时变成s偏光。偏振光经过电光晶体后入射到偏振分光装置102，偏振分光装置102将s偏光和p偏光分离，从偏振分光装置102分离的s偏光入射到第一耦合透镜103，从偏振分光装置102分离的p偏光经反射镜108反射后入射到第二耦合透镜113，s偏光和p偏光分别被第一耦合透镜103和第二耦合透镜113耦合到第一激光晶体105和第二激光晶体115，并依次分别通过对应的倍频晶体和输出镜。第一耦合透镜103和第二耦合透镜113的入射面和出射面均镀有808nm的增透膜。第一激光晶体105的入射面镀有泵浦光的增透膜和基频光的反射膜，第一激光晶体105的出射面镀有基频光的增透膜；第一倍频晶体107的入射面镀有基频光的增透膜和倍频光的反射膜，其出射面镀有基频光和倍频光的增透膜；第一输出镜106入射面镀有基频光的反射膜和倍频光的增透膜，出射面镀有倍频光的增透膜；第一激光晶体105的入射面和第一输出镜106的入射面构成激光谐振腔；同理，第二光路的第二激光晶体115、第二倍频晶体117和第二输出镜116分别与第一光路的第一激光晶体105、第一倍频晶体107和第一输出镜106的镀膜相同，反射镜108镀有泵浦光的反射膜。第一激光晶体105和第二激光晶体115分别受到s偏光和p偏光激励，输出基频光，基频光分别通过第一倍频晶体107和第二倍频晶体117获得倍频光输出。In this embodiment, the polarization conversion element 101 uses an electro-optic crystal. When the electro-optic crystal voltage is taken

When (V _π is the half-wave voltage), the phase difference generated by the beam is

That is, the plane of polarization is rotated by 90 degrees. Set the low level of a cycle square wave voltage signal to be V ₀ (V ₀ <V _M ), and the high level to be

Apply the above periodic square wave voltage signal with a certain duty cycle to the electro-optic crystal, then under the drive of low level V ₀ , the polarization plane of the polarized light emitted by the pump source 112 does not rotate after passing through the electro-optic crystal. Driven by the level V _M , the polarized light rotates 90 degrees after passing through the electro-optic crystal, that is, the s-polarized light entering the electro-optic crystal becomes p-polarized light when it exits, and the p-polarized light entering the electro-optic crystal becomes s-polarized light when it exits. The polarized light enters the polarization beam splitting device 102 after passing through the electro-optic crystal, and the polarization beam splitting device 102 separates the s-polarized light and the p-polarized light, and the s-polarized light separated from the polarization beam-splitting device 102 enters the first coupling lens 103, and the p-polarized light separated from the polarization beam-splitting device 102 The polarized light is reflected by the reflector 108 and enters the second coupling lens 113. The s-polarized light and p-polarized light are respectively coupled to the first laser crystal 105 and the second laser crystal 115 by the first coupling lens 103 and the second coupling lens 113, and respectively Through the corresponding frequency doubling crystal and output mirror. Both the incident surface and the outgoing surface of the first coupling lens 103 and the second coupling lens 113 are coated with an 808nm anti-reflection film. The incident surface of the first laser crystal 105 is coated with the anti-reflection film of the pump light and the reflection film of the fundamental frequency light, and the output surface of the first laser crystal 105 is coated with the anti-reflection film of the fundamental frequency light; The incident surface is coated with an anti-reflection film for fundamental frequency light and a reflective film for frequency doubled light, and its outgoing surface is coated with an antireflection film for fundamental frequency light and frequency doubled light; the incident surface of the first output mirror 106 is coated with a reflective film for fundamental frequency light. The anti-reflection film of the film and the frequency-doubled light, and the anti-reflection film of the frequency-doubled light is coated on the exit surface; the incident surface of the first laser crystal 105 and the incident surface of the first output mirror 106 constitute a laser resonator; similarly, the second optical path The coating of the second laser crystal 115, the second frequency doubling crystal 117 and the second output mirror 116 of the first optical path is the same as that of the first laser crystal 105, the first frequency doubling crystal 107 and the first output mirror 106 respectively, and the reflection mirror 108 Coated with reflective coating for pump light. The first laser crystal 105 and the second laser crystal 115 are excited by the s-polarized light and the p-polarized light respectively, and output the fundamental frequency light, and the fundamental frequency light passes through the first frequency doubling crystal 107 and the second frequency doubling crystal 117 respectively to obtain the frequency doubled light output.

The working process of the laser head in this example will be described in detail below, and the ratio of the s-polarized light component and the p-polarized light component in the pump light is 100%:0 as an example for illustration:

不难得出，在上述电压信号的驱动下，KTP电光晶体的出射光中的s偏光分量占总泵浦光功率百分比分布图如图2的b部分所示，p偏光分量的示意图如图2的c部分所示，其中施加在KTP电光晶体上的电压为V_M的时间段内，经过KTP电光晶体的线偏振光的偏振面旋转90度，所以此时间内入射到KTP电光晶体的s偏光的偏振面旋转90度，从KTP电光晶体出射的光转换为p偏光(只有p偏光分量)；施加在KTP电光晶体上的电压为V₀的时间段内，经过KTP电光晶体的线偏振光的偏振面不发生旋转，此时间段内入射到KTP电光晶体的s偏光不发生偏振面旋转，从KTP电光晶体出射的光不发生变化，仍为s偏光(只有s偏光分量)，这样KTP电光晶体的输出光的占空比与方波电压信号的占空比相对应，其中KTP电光晶体的输出光中的s偏光分量和p偏光分量的功率占总泵浦光功率的百分比在时间上相互交错分布，即s偏光分量的功率百分比为最大值(对应本实施例，为100％)时，p偏光分量的功率百分比为最小值(对应本实施例，为0)，反之，当s偏光分量的功率百分比为最小值时，p偏光分量的功率百分比为最大值。当泵浦光中的s偏光分量和p偏光分量的比例为100％和0时，则KTP电光晶体交替出射s偏光和p偏光。Polarization conversion element 101 uses potassium titanyl phosphate (KTP) electro-optic crystal, pump source 112 uses a GaAs semiconductor laser that generates laser light with a center wavelength of 808 nm, and polarization beam splitter 102 is a PBS prism (Polarization Beam Splitter, polarization beam splitter prism). The first laser crystal 105 and the second laser crystal 115 are both neodymium-doped yttrium vanadate (Nd:YVO ₄ ) crystals, the first frequency-doubling crystal 107 and the second frequency-doubling crystal 117 are both LBO crystals, and each crystal is coated with corresponding film layer. The GaAs semiconductor laser generates linearly polarized light, and the power percentages of the s-polarized and p-polarized components of the pump light incident on the KTP electro-optic crystal are 100% and 0, respectively, that is, the pump light only has s-polarized light. After polarization conversion by the KTP electro-optic crystal, the light is divided into s-polarized component and p-polarized component through the PBS prism. The fundamental frequency light of 1064nm is emitted, and the fundamental frequency light of the first optical path and the second optical path respectively pass through the first frequency doubling crystal 107 and the second frequency doubling crystal 117 to output 532nm frequency doubling light respectively. As shown in Figure 2, part a of Figure 2 shows the voltage signal applied to the KTP electro-optic crystal, this voltage signal is a periodic square wave signal with a preset duty cycle, the high level is V _M , and the low level is V ₀ , in each cycle of the periodic square wave voltage signal, the duration of the high level is T ₁ , and the duration of the low level is T ₂ , and the duty cycle in this embodiment is 25%, namely

It is not difficult to conclude that, driven by the above-mentioned voltage signal, the percentage distribution of the s-polarized light component in the outgoing light of the KTP electro-optic crystal to the total pump light power is shown in part b of Figure 2, and the schematic diagram of the p-polarized light component is shown in Figure 2 As shown in part c, during the time period when the voltage applied to the KTP electro-optic crystal is V _M , the polarization plane of the linearly polarized light passing through the KTP electro-optic crystal rotates 90 degrees, so the s-polarized light incident on the KTP electro-optic crystal during this time The polarization plane is rotated by 90 degrees, and the light emitted from the KTP electro-optic crystal is converted into p-polarized light (only the p-polarized light component); during the time period when the voltage applied to the KTP electro-optic crystal is V ₀ , the polarization of the linearly polarized light passing through the KTP electro-optic crystal The plane does not rotate, the polarization plane of the s-polarized light incident on the KTP electro-optic crystal does not rotate during this time period, and the light emitted from the KTP electro-optic crystal does not change, and is still s-polarized light (only the s-polarized light component), so the KTP electro-optic crystal The duty cycle of the output light corresponds to the duty cycle of the square wave voltage signal, where the power of the s-polarized light component and the p-polarized light component in the output light of the KTP electro-optic crystal account for the percentage of the total pump light power and are interleaved in time. , that is, when the power percentage of the s polarized light component is the maximum value (corresponding to this embodiment, it is 100%), the power percentage of the p polarized light component is the minimum value (corresponding to this embodiment, it is 0), otherwise, when the power of the s polarized light component When the percentage is the minimum value, the power percentage of the p-polarization component is the maximum value. When the ratio of the s-polarized light component and the p-polarized light component in the pump light is 100% and 0, the KTP electro-optic crystal emits s-polarized light and p-polarized light alternately.

In this embodiment, the PBS prism of the polarization splitting device 102 can spatially separate the s-polarized light component and the p-polarized light component in the light emitted from the KTP electro-optic crystal into two paths of light, so for this embodiment, the PBS prism separated The time distributions of s-polarized light and p-polarized light are also shown in part b of Figure 2 and part c of figure 2, that is, s-polarized light and p-polarized light are distributed alternately in time, and the duty cycle is the same as that applied to the KTP electro-optic crystal. corresponding to the electrical signal. For this embodiment, ideally, the temporal distribution of the s-polarized light incident on the first laser crystal 105 and the p-polarized light incident on the second laser crystal 115 is shown in part b of FIG. 2 and part c of FIG. 2 the same. The first optical path outputs 532nm laser light under the excitation of s-polarized light, and the second optical path outputs 532nm laser light under the excitation of p-polarized light. 2 part d and Fig. 2 part e. It can be seen that for the first optical path, the s-polarized light of the pump light is a periodic square wave pulse with a duty ratio of 75%, and the first optical path is excited by the s-polarized light to output a pulse laser with a duty ratio of 75%. In the interval between, the Nd:YVO ₄ crystal in the first optical path can effectively dissipate the heat generated by the laser output just now; also under the excitation of the p-polarized light interlaced with the s-polarized light of the above-mentioned pump light in time, the second The optical path outputs a pulsed laser with a duty ratio of 25%. In the same principle, the Nd:YVO ₄ crystal in the second optical path can also effectively dissipate the heat generated by the output laser during the pulse output interval, which reduces the laser crystal The thermal effect reduces the thermal gradient of the laser crystal, makes the laser crystal absorb the pump light uniformly, and improves the output optical power; The purpose of the time utilization of the pumping source of the whole device. In particular, in this embodiment, the same crystal is used for the laser crystal and the frequency doubling crystal in the first optical path and the second optical path. In other cases, of course, different laser crystals and/or different frequency doubling crystals can be selected. At this time, lasers with the same or different wavelengths can be output from the two optical paths, and if the two optical paths output lasers with different wavelengths, the two laser paths can also be combined to output one output.

In addition, the coating methods of the laser crystal, the frequency doubling crystal and the output mirror in this embodiment can be properly adjusted as required. In addition, the optical path in this embodiment includes a frequency doubling crystal to output frequency doubling light, and the frequency doubling crystal can also be removed to output fundamental frequency light. In this embodiment, the output mirror is used, and the output mirror can also be removed, and the resonant cavity can be realized by coating on the corresponding crystal. Certainly, the coating of each optical element in the optical path is different according to the specific optical path, which can be understood by those skilled in the art.

In addition, in the above description of this embodiment, the pump light generated by the pump source is s-polarized light, but it is easy to understand that the pump light generated by the pump source may also be p-polarized light. When the semiconductor laser does not emit linearly polarized light, Polarizing optical elements can be used to make the semiconductor laser emit linearly polarized light first. In addition to the semiconductor laser, the pump source can also use a solid-state laser formed by a gain medium with birefringence characteristics, such as a neodymium-doped yttrium lithium fluoride (Nd:YLF) solid-state laser and a neodymium-doped yttrium aluminate (Nd:YAP ) solid-state lasers, etc.

Fig. 3 shows the light-to-light conversion efficiency diagram obtained under different duty ratios of the first optical path (s-polarized light path) in Embodiment 1. The light-to-optical conversion efficiency of the first optical path is the output optical power of the first optical path and the first The ratio of the pump light power of the optical path. In the experiment, the total pump power (that is, the power sum of s-polarized light and p-polarized light) is taken as 4W, the electro-optic crystal is KTP electro-optic crystal, the laser crystal is Nd:YVO ₄ crystal, and the frequency doubling crystal is lithium triborate (LBO) crystal , the output mirror is a plano-concave mirror, and both optical paths output 532nm frequency doubled light. Figure 3 shows the change curve of the light-to-light conversion efficiency with the duty cycle gradually increasing from 20% to 100% in the frequency range from 50Hz to 2KHz. When the duty cycle is 100%, it is continuous light. It can be seen from Figure 3 that the light-to-light conversion efficiency of continuous light is less than 5%, and when the frequency is within 50Hz to 1KHz, the light-to-light conversion efficiency of square waves with a duty cycle exceeding 25% is greater than or equal to 5%, that is At this time, the light-to-light conversion efficiency of the first light path is higher than that of the continuous light. Since the laser outputs of the first light path and the second light path are complementary in time, it can be inferred that when the duty cycle is 25% When the frequency is within 75% and the frequency is within 50Hz to 1KHz, the optical-to-optical conversion efficiencies of the first optical path and the second optical path are greater than or equal to 5%. Then, after the output optical power of the two optical paths is combined at this time, the optical-to-optical conversion efficiency must be It is also higher than the light-to-light conversion efficiency of continuous light, and can obtain higher output light power. When the duty cycle is 50% to 75%, the light-to-light conversion efficiency is significantly improved, especially when the duty cycle is 60% to 70%, the light-to-light conversion efficiency reaches the peak range, generally up to 9%. At this time, On the premise that the total pump light power (that is, the power sum of s-polarized light and p-polarized light) is equal, even if only one path of s-polarized light is considered in the present invention, its output light power can reach 4W×60%×9%=0.324W, And the output light power of the continuous output light is 4W×5%=0.2W, so the light output power of one path of the first light path has exceeded the output power of the continuous light, so the output light of the first light path of the present invention and the second light path are combined After the end, you can get a greater output power.

The pump light may not be linearly polarized light, as long as the power percentage difference between the s-polarized light component and the p-polarized light component of the pump light is more than 40%, and the duty cycle satisfies a certain ratio, the system can also achieve high electro-optic conversion efficiency and long system time. The purpose of high utilization rate and reducing the thermal effect of the laser crystal will be described in detail below by taking Embodiment 2 as an example.

Embodiment two:

FIG. 4 shows a schematic structural diagram of the laser head of this embodiment. As can be seen from FIG. 4 , the laser head includes a pumping source 412, a polarization conversion element 401, a polarization splitting device 402, a first coupling lens 403 and a second coupling lens 413, a first laser crystal 405 and a second laser crystal 415, the first The output mirror 406 and the second output mirror 416 , the first reflection mirror 408 and the second reflection mirror 407 , and the beam combining mirror 404 . The optical path where the first laser crystal 405 is located is defined as the first optical path, and the optical path where the second laser crystal 415 is located is the second optical path. Reflective film that outputs light. The polarization conversion element 401 adopts KTP electro-optic crystal, the pump source 412 is a GaAs semiconductor laser emitting laser with a center wavelength of 808nm, and the polarization beam splitter 402 is a PBS prism (Polarization Beam Splitter, polarization beam splitter). Both the incident surface and the outgoing surface of the first coupling lens 403 and the second coupling lens 413 are coated with _808nm anti-reflection coating; 1341nm reflection film and 808nm anti-reflection film, its outgoing surface is coated with 1341nm anti-reflection film; the incidence surface of the first output mirror 406 is coated with 1341nm reflection film; the second laser crystal 415 is doped with neodymium yttrium aluminum garnet ( Nd:YAG) crystal, Nd:YAG crystal incident surface is coated with 1064nm reflection film and 808nm anti-reflection film, its exit surface is coated with 1064nm anti-reflection film; The incident surface of the second output mirror 416 is coated with 1064nm partial transmission Film coating; the first reflector 408 is coated with a reflective film of 808nm; the second reflective mirror 407 is coated with a reflective film of 1064nm. In particular, the laser head in this embodiment is also provided with a beam combiner 404, and the incident surface and the output surface of the beam combiner 404 are all coated with an anti-reflection film of 1341nm and a reflective film of 1064nm, so that by using the beam combiner 404, the The output laser beams of the first optical path and the second optical path are combined to convert the pulsed laser light into a continuous or quasi-continuous laser output.

The semiconductor laser emits partially polarized light as pump light, and the powers of the s-polarized component and p-polarized component of the pumped light incident on the KTP electro-optic crystal are 80% and 20%, respectively, as shown in Figure 5, and part a of Figure 5 shows A square wave signal with a duty cycle of 40%, when the high level VM of the square wave signal is applied to the KTP electro-optic crystal, the polarization plane of the polarized light incident on the KTP electro-optic crystal is rotated by 90 degrees, so the output from the KTP electro-optic crystal The percentages of the s-polarized component and the p-polarized component in the incident light are exchanged, that is, the s-polarized component becomes 20% and the p-polarized component becomes 80%; when the low level V0 of the square wave signal is applied to the KTP electro-optic crystal, after The polarization plane of the polarized light of the KTP electro-optic crystal does not rotate, and the polarization state of the light emitted from the KTP electro-optic crystal is the same as that of the incident light. It can be seen that, driven by the above-mentioned voltage signal, for this embodiment, the polarization state of the KTP electro-optic crystal The time distribution of the power percentage of the s-polarized component and the p-polarized component in the outgoing light to the total output light is shown in part b of FIG. 5 and part c of FIG. 5 , respectively. In general, the output light is the minimum value of p polarization when the s polarization component is the largest, and the maximum value of p polarization when the s polarization is the smallest, and the maximum and minimum values of s polarization and p polarization are applied to the KTP electro-optic crystal. corresponding to the duty cycle of the square wave voltage signal.

Similar to Embodiment 1, the PBS prism can separate the light emitted from the KTP electro-optic crystal into s-polarized light components and p-polarized light components. Therefore, the time distribution of s-polarized light and p-polarized light separated by the PBS prism is the same as that shown in part b of Figure 5 and part c of Figure 5, that is, the percentage of the power of p-polarized light and s-polarized light to the total optical power in time staggered distribution on each other, and the p-polarized duty cycle is the same as the electrical signal applied to the KTP electro-optic crystal, which is 40%; the s-polarized duty cycle is complementary to the electrical signal applied to the electro-optic crystal, which is 60%.

Equally, similar to Embodiment 1, the time distribution of the s-polarized light and p-polarized light on the Nd:GdVO ₄ crystal and the Nd:YAG crystal from the two-way partially polarized light emitted from the PBS prism is different from the s-polarized light separated by the PBS prism The time distribution of the p-polarized light is consistent with that shown in part b of Fig. 5 and part c of Fig. 5. In this way, under the excitation of the incident s-polarized light and p-polarized light, the first optical path and the second optical path respectively output laser light corresponding to the incident polarized light, and the output optical power of the first optical path and the second optical path are distributed in time, respectively, as shown in part d of Figure 5 and as shown in part e of Figure 5.

In particular, a beam combining mirror 404 can also be arranged behind the Nd:GdVO ₄ crystal and the Nd:YAG crystal in the optical path, for combining the laser beams output by the first and second optical paths, and utilizing the two laser paths simultaneously, ideally state to obtain continuous light output. At the same time, an optical element for adjusting the propagation direction of the light beam can also be arranged between the first optical path, the second optical path and the beam combining mirror 404 , and a second reflector 407 is arranged between the second optical path and the beam combining mirror 404 in this embodiment.

It can be seen that the difference from Example 1 is that in this example, the Nd:GdVO ₄ crystal and the Nd:YAG crystal are always excited by the pump light, and the excitation has a maximum excitation value and a non-zero minimum excitation value. Under the pumping of the minimum excitation value, both Nd:GdVO ₄ crystal and Nd:YAG crystal can release the heat generated by the output laser just under the excitation of the maximum excitation value to a certain extent, thus reducing the heat accumulation, thereby increasing the total output laser power, and because the power waveforms of the laser output by the Nd:GdVO ₄ crystal and the Nd:YAG crystal are complementary in time, so ideally, the entire system is outputting at all times Laser, thereby improving the time utilization of the pump source. Of course, those skilled in the art can understand that the beam combiner 404 and the second reflector 407 may not be used in this embodiment. At this time, the laser head obtains two optical outputs, and if the two laser crystals are the same, the output can also be Two laser beams with the same wavelength.

In particular, the waveforms shown in Figure 2 and Figure 5 are only schematic diagrams, and there may be certain errors in actual work.

Using the scheme of dividing the pump light into two beams of square waves for excitation can reduce the heat accumulation of the laser crystal, reduce the thermal gradient of the laser crystal, and effectively reduce the thermal effect of the laser crystal, thereby greatly improving the light-to-light conversion of the entire device efficiency. In particular, when the duty cycle of the modulation signal applied by the electro-optic crystal in the device is in the range of 25% to 75%, the light-to-light conversion efficiency of the two paths is significantly higher than that of continuous light, and this scheme can effectively The heat effect of the laser crystal is reduced, so the invention simultaneously realizes the purposes of improving the electro-optic conversion efficiency of the device and improving the time utilization rate of the pumping source.

Embodiment three:

The laser head of the invention can effectively eliminate laser speckles when applied in the technical field of laser display. This embodiment is a laser display light source using the laser head of Embodiment 1 or Embodiment 2. FIG. 6 is a schematic structural diagram of a laser display light source in this embodiment, and the laser display light source includes a light source group 601 , a coupling lens group 602 and an optical fiber bundle 603 . The light source group 601 is composed of 10 lasers, and the 10 lasers all adopt the laser head with the structure shown in Embodiment 1 of the present invention, the coupling lens group 602 includes 20 coupling lenses, and the fiber bundle 603 includes 20 optical fibers. The 10 lasers emit two laser beams, and the 20 outgoing laser beams are respectively coupled into 20 optical fibers through 20 coupling lenses, and the laser output ends of the 20 optical fibers are fixed as a group with a fixing device. In the above-mentioned light source device, because the laser beams emitted by each laser have no coherence, it can achieve a better speckle dissipation effect. In addition, the two laser beams emitted by the same laser generally have a certain optical path difference. When the optical path difference of the light guided by the two optical fibers is greater than the coherence length, the two laser beams will not interfere, and the speckle can be better eliminated. Moreover, it is known in the prior art that there is generally no coherence between multiple laser light sources, so using multiple laser light sources as a display light source can achieve speckle elimination to a certain extent, and the more the number of laser beams, the more obvious the effect of eliminating speckle . However, the light sources of existing display devices with this type of structure are all single-channel output lasers, and 20 laser beams need 20 lasers. However, the light source device of the present invention can realize outputting more light beams with fewer light sources. Purpose: Compared with the light source of the existing display device with this structure, the light source device saves half of the lasers, effectively reduces the volume of the light source, and achieves a better effect of dissipating speckle.

The laser crystals in the present invention can also be Nd:YLF, Yb:YAG or Nd:Cr:GSGG crystals, etc., the frequency doubling crystals can also be KTP, BBO, BIBO, KN or LN crystals, etc., and the laser crystals in different optical paths Different laser crystals and frequency doubling crystals can be used for frequency doubling crystals. In addition, the present invention can not only be used for fundamental frequency light and double frequency light, but also can generate triple frequency, quadruple frequency laser, etc., and can also be used for difference frequency optical path, sum frequency optical path and parametric oscillation optical path. Of course, the optical path And the coating will also change accordingly according to the specific situation. The electro-optic crystal in Embodiment 1 of the present invention may be KTP, LiNbO ₃ , RTP, KD*P or BBO, etc.; the polarization conversion element 101 may also be a Faraday rotator. In addition, in Embodiment 1 and Embodiment 2, when the distance between the first optical path and the second optical path is relatively short, a laser crystal can be used instead of the first laser crystal and the second laser crystal, and a frequency doubling crystal can be used instead For the first frequency doubling crystal and the second frequency doubling crystal, an output mirror is used to replace the first output mirror and the second output mirror, and the output mirror can be a plane mirror at this time. In Embodiment 3, a laser crystal, a frequency doubling crystal or an output mirror can be used in one laser head, or a laser crystal and a frequency doubling crystal can be shared by multiple laser heads. Or an output mirror, the number of crystals or output mirrors is mainly determined according to the specific conditions of the optical path. If the optical paths are too far apart, using a crystal or output mirror will cause waste of crystals or output mirrors and increase the cost. The pumping light of the present invention can also be modulated into non-periodic pulsed light, besides square wave, it can also be modulated into triangular wave, sine wave and other forms of pulsed laser light. All of the above can be understood by those skilled in the art.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the present invention. within the scope of the claims.

Claims (17)

1. laser head comprises:

Pumping source is used to produce continuous laser;

Light-dividing device is used for the continuous laser that described pumping source produces is divided into two beam pulse formula pumping lasers; And

Two laserresonators are respectively applied for the described two beam pulse formula pumping lasers of reception and alternately export pulse laser.

2. laser head according to claim 1 is characterized in that, described pulsed pumping laser is a recurrent pulses laser.

3. laser head according to claim 1 is characterized in that, described pulsed pumping laser is the pulse laser of square wave form.

4. according to claim 1,2 or 3 described laser heads, it is characterized in that, the duty ratio sum of described two beam pulse formula pumping lasers is that 100%, two beam pulse formula pumping laser alternately produces, and wherein arbitrarily the duty ratio of beam of laser all in 25% to 75% scope.

5. laser head according to claim 1 is characterized in that described light-dividing device comprises polarised light conversion element and light splitting device.

6. laser head according to claim 5 is characterized in that, described polarised light conversion element is electrooptic crystal or Faraday polarization apparatus.

7. laser head according to claim 2 is characterized in that, the frequency of described pulsed pumping laser is that 50Hz is to 2KHz.

8. laser head according to claim 1 is characterized in that, comprises separately all in two described laserresonators that a laser crystal or two described laserresonators comprise a shared laser crystal.

9. laser head according to claim 8 is characterized in that, comprises separately also in two described laserresonators that an outgoing mirror or two described laserresonators comprise a shared outgoing mirror.

10. laser head according to claim 8 is characterized in that, comprises separately also in two described laserresonators that a frequency-doubling crystal or two described laserresonators comprise a shared frequency-doubling crystal.

11. laser head according to claim 1 is characterized in that, all places a coupled lens before two described laserresonators separately.

12. laser head according to claim 1 is characterized in that, described laser head also comprises the speculum that is used to adjust optical path direction.

13. laser head according to claim 1 is characterized in that, described laser head also comprises and closes the bundle output device, is used for that bundle is closed in the output of described two laserresonators and handles.

14. laser head according to claim 13 is characterized in that, described to close the bundle output device be light combination mirror, is used for that bundle is closed in the output of two laserresonators and handle obtains continuous laser output; The output frequency difference of described two laserresonators.

15. a laser display light source comprises light source group, coupled lens group and fiber bundle, it is characterized in that, described light source group is made up of the described laser head of at least one claim 1; Coupled lens in the described coupled lens group is one by one corresponding to the output beam of described laser head, be used for the output beam of described laser head respectively shaping be coupled in the corresponding optical fiber of described fiber bundle.

16. laser display light source according to claim 15, it is characterized in that, the quantity of the coupled lens of described coupled lens group is the twice of the quantity of described laser head, and the number of fibers of described fiber bundle equates with the quantity of the coupled lens of described coupled lens group.

17. laser display light source according to claim 16 is characterized in that, the output of described optical fiber is fixed as a branch of with fixture.

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