Ultraviolet laser

Abstract

The invention provides an ultraviolet laser. The ultraviolet laser comprises a seed source, a first pumping source, a first beam combiner, a first gain optical fiber, a frequency doubling device, a sum frequency device, a first dichroic mirror and a space coupling device. The seed source generates signal light with the wavelength ranging from 1000 nm to 1100 nm, the first pumping source generates pump light with the wavelength ranging from 900 nm to 1000 nm, and the pump light is used for providing sufficient pump for the first-stage amplification light path. Signal light and pump light are combined at the first beam combiner, and amplification of optical signals is achieved through the gain effect of the first gain optical fiber. The first dichroic mirror is used for carrying out color separation on the mixed light beam which is output after frequency summing of the frequency summing device, and separating ultraviolet light from green light and infrared light. Stray green light and infrared light after frequency doubling and frequency summing are collected through a space coupling device and then coupled and input into an optical fiber to bleach a laser system, so that the photon darkening effect is eliminated, the power of a laser is improved, and the long-term reliability and stability of the laser are improved.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and more particularly to an ultraviolet laser capable of suppressing photon darkening. Background Art

[0002] High-power ultraviolet lasers have shown incomparable advantages in many industrial processing solutions, especially in fine processing, relying on the small thermal impact of cold processing and the smaller focused spot, which is favored by industrial processing. However, solid lasers are limited by the thermal effect of materials, and the output ultraviolet power is low due to the limitation of light-to-light conversion rate, and it is usually difficult to exceed 100W, which seriously affects the processing efficiency and increases the processing cost for industrial processing after the light beam is frequency-doubled (for example, after the infrared laser wavelength of 1064nm passes through the frequency-doubling crystal, the wavelength is reduced by half to become a 532nm green laser. At this time, the infrared laser is called the fundamental frequency light, and the green laser is the frequency-doubled light) and then summed (the infrared laser wavelength of 1064nm and the green laser wavelength of 532nm are mixed and passed through the summed frequency crystal to generate 335nm, 236nm, and 199nm ultraviolet light).

[0003] Optical-solid hybrid (fiber + solid) technology, due to the use of fiber power amplification technology, can increase the power of ultraviolet lasers to hundreds of watts or even close to kilowatts, and has a high repetition rate, which is very suitable for industrial high-speed processing needs. However, in high-power ultraviolet lasers, it is necessary to output a narrow linewidth polarization-maintaining light source from the optical fiber, which requires very high and difficult control of the control process of the optical fiber material. The photon darkening effect of ultraviolet lasers using optical fiber technology will also reduce the transverse mode instability (TMI) threshold, causing abnormal phenomena such as light flash / spot deformation / power attenuation / mode instability in the laser, and limiting the further increase of the power of the ultraviolet laser, which seriously affects the effect of industrial use.

[0004] In the existing technology, in high-power infrared lasers using optical fiber technology, the photobleaching effect has been achieved by adding an additional visible light pump source to suppress or eliminate the effect of the photon darkening effect on the power increase of the laser. In theory, high-power ultraviolet lasers using a light-solid hybrid (optical fiber + solid) structure can also photobleach the photon darkening effect by adding an additional visible light pump source. However, the additional visible light pump source will undoubtedly increase production costs and is not conducive to the development direction of lightweight overall product structure.

[0005] Based on this, it is necessary to invent a low-cost ultraviolet laser that can effectively suppress the photon darkening effect. Summary of the invention

[0006] The purpose of the present application is to provide an ultraviolet laser, which at least solves the problem of large space occupation and high production cost caused by the need to add additional devices for the ultraviolet laser that suppresses photon darkening in the background technology. Therefore, the present invention can reduce production costs and will also be conducive to the development of lightweight overall product structure. The ultraviolet laser provided by the present application can meet the market's requirements for lightweight products and reduce production costs.

[0007] To achieve the above objectives, this application provides the following technical solutions:

[0008] The present application provides an ultraviolet laser, comprising: a seed source, a first pump source, a first beam combiner, a first gain fiber, a frequency doubling device, a sum frequency device, a first dichroic mirror and a spatial coupling device.

[0009] The seed source generates a signal light with a wavelength of 1000-1100nm, and the first pump source generates a pump light with a wavelength of 900-1000nm, which is used to provide sufficient pumping for the first-stage amplification optical path. The signal light and the pump light are combined at the first beam combiner, and the gain effect of the first gain fiber is used to achieve optical signal amplification.

[0010] The frequency doubling device is mainly used to double the frequency of the infrared light beam after the gain power of the first gain optical fiber is amplified. At this time, part of the infrared light is not completely converted into green light.

[0011] The green light and infrared mixed light input through the frequency doubling device are frequency-added in the sum frequency device to generate a mixed light beam of green light, infrared light and ultraviolet light.

[0012] The first dichroic mirror performs color separation on the mixed light beam output after the sum frequency device performs frequency summing, and separates the ultraviolet light from the green light and the infrared light. The ultraviolet light is used as the processing laser for light output, and then the green light and the infrared light separated by the first dichroic mirror are coupled as the bleaching light beam through the spatial coupling device, and the spatial light beam is coupled into the optical fiber for transmission, so as to be combined by the first beam combiner and enter the first gain optical fiber for light bleaching.

[0013] The first dichroic mirror 7 separates ultraviolet light from green light and infrared light by coating with a high-transmittance film and a high-reflection film.

[0014] The high-power ultraviolet laser provided by the present invention adopts a light-solid hybrid (optical fiber + solid) structure, collects the stray green light and infrared light after frequency doubling and summing through a spatial coupling device, and then couples them into the optical fiber to bleach the laser system, eliminate the photon darkening effect, and improve the power of the laser, as well as the long-term reliability and stability.

[0015] Compared with the prior art, the present invention can photobleach the photon darkening effect without the need for an additional visible light pump source, and the stray green light must be collected and processed even if it is not used for photon bleaching to prevent damage to the internal components of the laser. Therefore, the present invention can reduce production costs and will also be conducive to the development of lightweight overall product structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A first structural schematic diagram of the ultraviolet laser provided in this application;

[0018] Figure 2 A second structural schematic diagram of the ultraviolet laser provided in this application;

[0019] Figure 3 A third structural schematic diagram of the ultraviolet laser provided in this application;

[0020] Figure 4 This is a fourth structural schematic diagram of the ultraviolet laser provided in this application.

[0021] Figure 5 A fifth structural schematic diagram of the ultraviolet laser provided in this application;

[0022] Figure 6 This is a sixth structural schematic diagram of the ultraviolet laser provided in this application.

[0023] Figure numerals: 1. seed source, 2. first pump source, 3. first beam combiner, 4. first gain fiber, 5. frequency doubling device, 6. sum frequency device, 7. first color splitter, 8. spatial coupling device, 9. first power detection device, 10. spectrometer, 11. first isolation device, 12. second pump source, 13. second beam combiner, 14. second gain fiber, 15. second isolation device, 16. light stripping device, 17. light output device, 18. light collector. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, and are not limitations on the scope of the rights of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0025] See also Figure 1 , Figure 1 This is a first structural schematic diagram of the ultraviolet laser provided in the present application, which includes: a seed source 1, a first pump source 2, a first combiner 3, a first gain fiber 4, a frequency doubling device 5, a sum frequency device 6, a first dichroic mirror 7 and a spatial coupling device 8.

[0026] The seed source 1 generates a signal light with a wavelength of 1000-1100nm, and the first pump source 2 generates a pump light with a wavelength of 900-1000nm, which is used to provide sufficient pumping for the first-stage amplification optical path, so as to achieve a population inversion in the gain medium and thus stimulate the emission of laser light. The signal light and the pump light are combined at the first beam combiner 3, and the gain effect of the first gain fiber 4 is used to amplify the optical signal.

[0027] The frequency doubling device 5 is mainly used to double the frequency of the infrared light beam after the gain power is amplified by the first gain fiber 4, that is, to output a green light doubled frequency beam of 500-550nm after doubling the fundamental frequency beam of 1000-1100nm. At this time, some infrared light will not be completely converted into green light.

[0028] The green light and infrared mixed light inputted through the frequency doubling device 5 are frequency-added in the frequency addition device 6, thereby generating a mixed light beam of green light, infrared light and ultraviolet light.

[0029] The first dichroic mirror 7 performs color separation on the mixed light beam output after the sum frequency device 6 performs frequency separation, and separates the ultraviolet light from the green light and the infrared light. The ultraviolet light is used as the processing laser for light output, and then the green light after the first dichroic mirror 7 is coupled as the bleaching light beam through the spatial coupling device 8, and the spatial light beam is coupled into the optical fiber for transmission, so as to be combined by the first beam combiner 3 and enter the first gain optical fiber 4 for photobleaching. Usually, green light is used as the main light source for photobleaching. In some embodiments, infrared light can also be used as a supplementary light source to enhance the photobleaching effect of green light, and usually has the effect of slightly enhancing the photobleaching effect of green light.

[0030] In the embodiment of the present application, the first dichroic mirror 7 is coated with a 190-360nm high-transmittance film, a 500-550nm, or 1000-1100nm high-reflection film.

[0031] In other embodiments, the first dichroic mirror 7 may also be coated with a 500-550nm, 1000-1100nm high-transmittance film, or a 190-360nm high-reflection film, as long as it can separate the ultraviolet light from the green light and the infrared light.

[0032] In a preferred solution, in order to reduce losses, the internal optical elements of the frequency doubling device 5 are coated with anti-reflection films of 500-550nm and 1000-1100nm, and the internal elements of the sum frequency device 6 are coated with anti-reflection films of 190-360nm, 500-550nm and 1000-1100nm.

[0033] In a specific embodiment, infrared light beams of 1064 nm and 1030 nm may be used as fundamental frequency light, and after frequency doubling, frequency-doubled green light beams of 532 nm and 515 nm may be output respectively.

[0034] The high-power ultraviolet laser provided by the present invention adopts a light-solid hybrid (optical fiber + solid) structure. The stray green light and infrared light after frequency doubling and summing are collected through a spatial coupling device 8 and then coupled into the optical fiber to bleach the laser system, eliminate the photon darkening effect, and improve the power of the laser, as well as the long-term reliability and stability.

[0035] Compared with the prior art, the present invention can photobleach the photon darkening effect without the need to add an additional visible light pump source. By using the spatial coupling device 8 instead of the visible light pump source, the production cost can be reduced, and it will also be conducive to the development of the lightweight overall structure of the product. At the same time, in the field of high-power fiber laser technology, the higher the output laser power, the more serious the photon darkening effect, and at this time, the power of the stray green light and infrared light obtained after the first dichroic mirror 7 is also greater, and the photobleaching ability after coupling through the spatial coupling device 8 is also stronger. Usually, the photon darkening effect and the laser power are close to a linear relationship, and the power of the stray green light and infrared light is also close to a linear relationship with the power of the ultraviolet laser to be output, that is, no additional visible light pump source is required, and the requirements can be met by photobleaching the stray green light. If the ultraviolet light to be obtained is a deep ultraviolet laser, the stray green light and infrared light can be coupled into the optical fiber system through the spatial coupling device 8 as bleaching light.

[0036] See also Figure 2 , Figure 2 The second structural diagram of the ultraviolet laser provided in this application. Figure 1 On the basis of, it also includes a first power detection device 9 and a spectroscope 10.

[0037] The first power detection device 9 is located behind the first gain fiber 4, and extracts a very small part of the power from the laser amplification system for monitoring the real-time power of the entire optical fiber system. The power value monitored by this component is amplified and converted according to a certain ratio, so that the output power at the first gain fiber 4 can be monitored in real time and feedback can be provided.

[0038] The beam splitter 10 is located between the first dichroic mirror 7 and the spatial coupling device 8. It is used to monitor the real-time power change of the optical fiber system according to the first power detection device 9. If the bleaching light is harmful to the devices inside the entire optical path system, it is necessary to adjust the beam splitter 10 to form a suitable splitting ratio, that is, a part of the light beam is processed as an idle green light through the beam splitter 10, and the remaining part of the light beam is reflected by the beam splitter 10 as a coupled green light, and then coupled into the optical fiber through the spatial coupling device 8, and then transmitted to the first beam combiner 3 for beam combination and enters the first gain fiber 4 to perform real-time bleaching of photon darkening.

[0039] In a specific solution, the shorter the wavelength of the output ultraviolet light, the greater the proportion of coupled green light separated by the spectroscope 10, and the smaller the proportion of idle green light. For example, the output ultraviolet light may be ultraviolet light in the wavelength band of 195-205nm, 220-230nm, or 350-360nm. Since the shorter the wavelength of the output ultraviolet light, the less total idle green light remains, the less idle green light needs to be processed at this time, and the higher the proportion of coupled green light coupled into the spatial coupling device 8 after passing through the spectroscope 10 needs to be. Therefore, in a specific embodiment, the proportion of coupled green light separated by the spectroscope 10 for ultraviolet light in the wavelength band of 195-205nm, 220-230nm, or 350-360nm is gradually reduced to prevent the bleaching light from damaging the components inside the optical path system when it enters the optical path system.

[0040] That is, when the output ultraviolet light can be 195-205nm ultraviolet light, the proportion of coupled green light separated by the beam splitter 10 is relatively large. When the output ultraviolet light can be 220-230nm ultraviolet light, the proportion of coupled green light separated by the beam splitter 10 will decrease, and the proportion of idle green light that needs to be processed will increase. When the output ultraviolet light can be 350-360nm ultraviolet light, the proportion of coupled green light separated by the beam splitter 10 will further decrease, and the proportion of idle green light that needs to be processed will further increase.

[0041] When outputting 195-205nm ultraviolet light, if the photobleaching effect of green light is insufficient, part or all of the miscellaneous infrared light can also be used as a supplementary light source to enhance the photobleaching effect of green light.

[0042] See also Figure 3 , Figure 3 The third structural diagram of the ultraviolet laser provided in this application. Figure 2Based on the UV laser shown, Figure 3 The ultraviolet laser shown also includes: a first isolation device 11, which is located between the first beam combiner 3 and the seed source 1, and is mainly used to protect the front-end seed source 1 from being affected by the light beam returned by the rear-end amplified optical path, reducing the risk of damage, and also to ensure that the seed source 1 can work stably and reliably.

[0043] See also Figure 4 , Figure 4 The fourth structural diagram of the ultraviolet laser provided in this application. Figure 3 On the basis of the ultraviolet laser shown, it also includes a second pump source 12, a second beam combining device 13, a second gain fiber 14, and a second isolation device 15. The second pump source 12, the second beam combining device 13, the second gain fiber 14 and the second isolation device 15 are located between the seed source 1 and the first isolation device 11.

[0044] Similarly, the second pump source 12 is used to provide sufficient pumping for the secondary amplification optical path, so as to achieve a particle number inversion in the gain medium and thus stimulate the emission of laser light. The second beam combiner 13 combines the signal light transmitted from the front section with the pump light output by the second pump source 12 and couples them in an optical fiber for transmission. The second gain optical fiber 14 stimulates the radiation of the pump light transmitted from the front section in this component, and performs a second gain amplification on the signal light. The second isolation device 15 is used to protect the device in front of it. When the optical path continues to transmit and amplify, the return light generated by the rear amplification will be blocked and consumed when passing through this component, preventing the return light from being transmitted back to the front stage optical path to cause device damage or laser instability.

[0045] like Figure 5 As shown, the high-power ultraviolet laser provided by the present invention is Figure 4 On the basis of the optical fiber 4 , it also includes a light stripping device 16 and a light output device 17 , and the light stripping device 16 and the light output device 17 are located between the first gain fiber 4 and the frequency doubling device 5 .

[0046] The light stripping device 16 can strip the pump light that is not absorbed and converted after amplification in the optical fiber system, thereby improving the monochromaticity and stability of the output light.

[0047] Specifically, the light stripping device 16 is mainly used to strip the pump light of 900-1000 nm.

[0048] The optical output device 17 is mainly used to output the signal light amplified by the optical fiber amplification system. The optical output device 17 can be a QCS or a CPS. In order to reduce the loss during output, the output end of the device can also be plated with a 1000-1100nm anti-reflection film.

[0049] In other embodiments, in order to obtain a higher power ultraviolet laser, a third pump source, a third beam combining device, a third gain fiber and a third isolation device may be included to perform three-stage amplification of the ultraviolet laser, or even more pump sources, beam combining devices, gain fibers and isolation devices may be added to perform more stages of amplification. A forward pump source amplification may be used, or a reverse pump source may be used for amplification. These are all conventional power amplification structures and will not be described in detail.

[0050] It should be noted that the first pump source and the second pump source shown in the above figure are only one, but the actual first pump source, the second pump source, and the third pump source can be one or more, which are set according to the actual power requirements of the laser.

[0051] like Figure 6 As shown, the high-power ultraviolet laser provided by the present invention is Figure 5 On the basis of the laser system, it also includes a light collector 18, which is mainly used to collect and consume the remaining infrared light and green light after being split by the spectroscope 10, so as to improve the thermal stability of the laser system and prevent damage to other devices in the system.

[0052] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device that includes a series of elements are inherent to the elements. In the absence of more restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements. In addition, the above-mentioned technical solutions provided in the embodiments of the present application are consistent with the corresponding technical solutions in the prior art in the principle of implementation, and the part is not described in detail, so as not to be too much.

[0053] Specific examples are used herein to illustrate the principles and implementation methods of the present application, and the description of the above embodiments is only used to help understand the method and its core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and the various embodiments in the present application can be combined, and these improvements, modifications and combinations also fall within the scope of protection of the claims of the present application.

Claims

1. An ultraviolet laser, characterized in that , comprising: a seed source (1), a first pump source (2), a first beam combiner (3), a first gain fiber (4), a frequency doubling device (5), a sum frequency device (6), a first dichroic mirror (7) and a spatial coupling device (8); The seed source (1) generates signal light with a wavelength of 1000 to (11)00 nm, the first pump source (2) generates pump light with a wavelength of 900 to 1000 nm, the signal light and the pump light are combined at the first combiner (3), and the optical signal is amplified through the gain effect of the first gain optical fiber (4); The frequency doubling device (5) is mainly used to double the frequency of the infrared light beam after the gain power is amplified by the first gain optical fiber (4); the green light and infrared mixed light input through the frequency doubling device (5) are summed in the summing device (6), thereby generating a mixed light beam of green light, infrared light and ultraviolet light; The first dichroic mirror (7) separates the ultraviolet light, green light and infrared light output after being summed by the sum-frequency device (6), and the spatial coupling device (8) couples the green light split by the first dichroic mirror (7) as a bleaching light beam, which is then combined by the first beam combiner (3) and enters the first gain optical fiber (4).

2. The ultraviolet laser according to claim 1, characterized in that , further comprising a first power detection device (9) and a spectroscope (10); The first power detection device (9) is located behind the first gain optical fiber (4), and monitors the output power of the first gain optical fiber (4) in real time and provides feedback; The beam splitter (10) is located between the first dichroic mirror (7) and the spatial coupling device (8); The light splitting ratio of the light splitter (10) is adjusted according to the real-time power change of the optical fiber system monitored by the first power detection device (9).

3. The ultraviolet laser according to claim 2, characterized in that The ultraviolet light may be ultraviolet light in the wavelength band of 195-205nm, 220-230nm or 350-360nm. The shorter the wavelength of the output ultraviolet light, the greater the proportion of coupled green light separated by the spectroscope (10), and the less the proportion of idle green light processed.

4. The ultraviolet laser according to claim 2, characterized in that , further comprising a first isolation device (11), wherein the first isolation device (11) is located between the first beam combiner (3) and the seed source (1).

5. The ultraviolet laser according to claim 4, characterized in that , further comprising a second pump source (12), a second beam combining device (13), a second gain fiber (14) and a second isolation device (15); The second pump source (12), the second beam combining device (13), the second gain optical fiber (14), and the second isolation device (15) are located between the seed source (1) and the first isolation device (11).

6. The ultraviolet laser according to claim 5, characterized in that , and also includes a light stripping device (16) and a light output device (17), wherein the light stripping device (16) and the light output device (17) are located between the first gain optical fiber (4) and the frequency doubling device (5).

7. The ultraviolet laser according to claim 6, characterized in that The light stripping device (16) is used to strip the pump light of 900-1000nm.

8. The ultraviolet laser according to claim 7, characterized in that , the light output device (17) is a QCS or a CPS.

9. The ultraviolet laser according to claim 8, characterized in that , and also includes a light collector (18), which is used to collect and consume the infrared light and green light remaining after being split by the spectroscope (10).

10. The ultraviolet laser according to claim 1, characterized in that The internal optical elements of the frequency doubling device (5) are coated with anti-reflection films of 500-550nm and 1000-1100nm, and the internal elements of the sum frequency device (6) are coated with anti-reflection films of 190-360nm, 500-550nm and 1000-1100nm.

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