Extra-cavity frequency-doubling pulse-width-adjustable ultraviolet laser device

Abstract

A half-wave plate and a focusing lens are sequentially arranged on an output light path of an infrared laser with adjustable pulse width, the focusing lens is connected with a frequency doubling crystal, the frequency doubling crystal is connected with a frequency tripling crystal, an output end face of the frequency tripling crystal is cut into a Brewster angle, and the output end face of the frequency tripling crystal is connected with an infrared laser. The output infrared laser is shielded by the infrared light blocking block after being transmitted in the space, the output green laser is shielded by the green light blocking block after being transmitted in the space, the frequency tripling crystal is connected with the imaging lens, the imaging lens is connected with the input surface of the wedge-shaped lens, and the input surface of the wedge-shaped lens is cut into a Brewster angle. Through fine adjustment of the distance between the imaging lens and the frequency tripling crystal and the distance between the wedge-shaped lens and the imaging lens, the ultraviolet laser output by the wedge-shaped lens becomes circular and is output. The Brewster angle output surface of the frequency tripling crystal reduces the ultraviolet damage probability and separates infrared light, green light and ultraviolet light. The position of the imaging lens is finely adjusted to compensate a light spot ellipse caused by a walk-off effect during frequency doubling.

Description

TECHNICAL FIELD

[0001] The utility model relates to a cavity outside frequency multiplication adjustable pulse width ultraviolet laser device. BACKGROUND

[0002] With the development of the laser industry, it is difficult to perfectly match the processing requirements in the use process of single-parameter lasers, so laser with adjustable pulse width is derived. Compared with picosecond lasers and femtosecond lasers, nanosecond lasers have lower cost, higher output pulse energy, and wider use range. In order to further improve the processing performance of the pulse width adjustable laser, the output wavelength of the pulse width adjustable laser needs to be extended from infrared to ultraviolet. Since the pulse width of the pulse width adjustable laser is generated by electrical switch modulation, there is no cavity structure, and cavity frequency multiplication is not possible, so the ultraviolet output of the pulse width adjustable laser needs to be performed in an extracavity frequency multiplication manner.

[0003] In the laser industry, when the nanosecond laser is frequency multiplied outside the cavity, the infrared laser needs to be focused to improve the frequency multiplication efficiency, and the focal point is near the second frequency multiplication crystal and the third frequency multiplication crystal. The infrared light is frequency multiplied by the second frequency multiplication crystal and the third frequency multiplication crystal in turn to form, the three frequency multiplication outputs are separated according to the different properties of ultraviolet, green and infrared, and the ultraviolet laser output with adjustable pulse width is obtained.

[0004] The existing technology focuses on how to improve the damage threshold and beam roundness of the output ultraviolet beam. Patent No. CN117117619A discloses a YAG side-pumped extracavity frequency multiplication ultraviolet laser, and the frequency multiplication method is the most common one. The disadvantage is that when the output surface of the third frequency multiplication crystal is only a coated surface, the damage of the output crystal end face is easy to occur when the output ultraviolet laser spot is small. Patent No. CN107315301A discloses a superfast laser three-frequency multiplication device and method, the output end face of the third frequency multiplication crystal is cut into Brewster angle, the polarization characteristics of the output light are used to realize ultraviolet separation output, and the damage probability of the output end face is reduced. The output ultraviolet beam is shaped into a circle by a wedge-shaped mirror, but the input beam is an approximate parallel beam, which cannot be compatible with the focused beam. Patent No. CN219321802U discloses an ultraviolet laser. In order to improve the damage threshold and beam roundness of the output ultraviolet beam, the output end face of the third frequency multiplication crystal is cut into Brewster angle, and a wedge-shaped mirror is added in front of the frequency multiplication crystal. The disadvantage is that the compatibility of the focused beam is poor, the focused beam becomes elliptical, and the spot and the frequency multiplication efficiency cannot be optimized at the same time. Patent No. CN116974120A discloses a superfast laser wedge angle beam expansion system, which shapes the output ultraviolet beam through the wedge angle beam expansion system. The disadvantage is that it cannot well compatible with the beam shaping of the output after the focused beam Brewster angle. UTILITY MODEL CONTENT

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an extracavity frequency-doubling adjustable pulse width ultraviolet laser device.

[0006] The objective of this utility model is achieved through the following technical solution:

[0007] An extracavity frequency-doubled tunable pulse width ultraviolet laser device is characterized by the following: a half-wave plate and a focusing lens are arranged sequentially in the output optical path of the pulse width-tunable infrared laser. The focusing lens is connected to a second-harmonic crystal, which is connected to a third-harmonic crystal. The output end face of the third-harmonic crystal is cut at Brewster's angle. The output infrared laser is blocked by an infrared light-blocking block after spatial transmission, and the output green laser is blocked by a green light-blocking block after spatial transmission. The third-harmonic crystal is connected to an imaging lens, which is connected to the input surface of a wedge mirror. The input surface of the wedge mirror is cut at Brewster's angle.

[0008] Furthermore, in the aforementioned extracavity frequency-doubled tunable pulse width ultraviolet laser device, the tunable pulse width infrared laser is an infrared laser with an output wavelength of 1030nm, 1064nm, and 1342nm, an output power of 1–500W, and a pulse width of 100fs–100ns.

[0009] Furthermore, in the aforementioned extracavity frequency-doubled adjustable pulse width ultraviolet laser device, the half-wave plate is an infrared half-wave plate with operating wavelengths in the 1030nm, 1064nm, and 1342nm bands.

[0010] Furthermore, in the aforementioned extracavity frequency-doubled adjustable pulse width ultraviolet laser device, the focusing lens operates in the 1030nm, 1064nm, and 1342nm wavelength bands.

[0011] Furthermore, in the aforementioned extracavity frequency-doubled tunable pulse width ultraviolet laser device, the second-harmonic crystal is LBO, BBO, or KTP.

[0012] Furthermore, in the aforementioned extracavity frequency-doubled tunable pulse width ultraviolet laser device, the third-harmonic crystal is LBO, BBO, or CLBO.

[0013] Furthermore, in the aforementioned extracavity frequency-doubled adjustable pulse width ultraviolet laser device, the imaging lens has an imaging ratio of less than or equal to 1.

[0014] Furthermore, in the aforementioned extracavity frequency-doubled adjustable pulse width ultraviolet laser device, the imaging lens has an imaging ratio of 1:1, 1:0.9, or 1:0.8.

[0015] Compared with the prior art, this utility model has significant advantages and beneficial effects, specifically reflected in the following aspects:

[0016] The utility model discloses utilize the mode of focusing frequency multiplication and the shaping output after imaging to realize the cavity outside frequency multiplication ultraviolet laser of high efficiency high beam quality, through the spacing of the imaging lens and the three times frequency crystal and the spacing of the wedge mirror and the imaging lens are adjusted slightly, make the ultraviolet laser of wedge mirror output become circular and output.Three times frequency crystal Brewster angle output surface reduces ultraviolet damage probability, carries out infrared light, green light and ultraviolet light separation.Imaging lens position fine adjustment compensates the spot ellipse caused by the walk-off effect when frequency multiplication, both guarantee the output efficiency, avoid the damage of device, can also keep the roundness of output spot, provide simple and effective implementation scheme for the cavity outside frequency multiplication ultraviolet laser of same type.

[0017] The other features and advantages of the utility model will be described in the subsequent specification, and, partially become obvious from the specification, or understand by implementing the utility model specific embodiment. The purpose and other advantages of the utility model can be realized and obtained through the structure that is pointed out in the written specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical scheme of the utility model embodiment, the following will be needed to use the drawings in the embodiment briefly introduced, should understand, the following drawings only shows some embodiments of the utility model, therefore should not be regarded as the limitation to the scope, for ordinary skilled person in the art comes, under the premise of not paying the creative labor, can also obtain other related drawings according to these drawings.

[0019] Figure 1 The utility model laser device light path structure schematic diagram. DETAILED DESCRIPTION

[0020] The technical scheme in the utility model embodiment will be described clearly and completely below in conjunction with the drawings in the utility model embodiment, obviously, the described embodiment only is a part of the embodiment of the utility model, not all the embodiment.Usually the components of the utility model embodiment described and shown in the drawing here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiment of the utility model provided in the drawing is not intended to limit the scope of the claimed utility model, but only represents selected embodiments of the utility model. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of the utility model protection.

[0021] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this utility model, directional and ordinal terms are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] like Figure 1 As shown, in an external cavity frequency-doubled adjustable pulse width ultraviolet laser device, a half-wave plate 2 and a focusing lens 3 are arranged sequentially on the output optical path of the adjustable pulse width infrared laser 1. The focusing lens 3 is connected to a second-harmonic crystal 4, which is connected to a third-harmonic crystal 5. The output end face of the third-harmonic crystal 5 is cut at Brewster's angle and is uncoated. The output infrared laser is blocked by an infrared light-blocking block 6 after spatial transmission, and the output green laser is blocked by a green light-blocking block 7 after spatial transmission. The third-harmonic crystal 5 is connected to an imaging lens 8, which is connected to the input surface of a wedge mirror 9. The input surface of the wedge mirror 9 is cut at Brewster's angle and is uncoated.

[0023] Among them, the pulse width adjustable infrared laser 1 is an infrared laser with an output wavelength of 1030nm, 1064nm, and 1342nm, an output power of 1 to 500W, and a pulse width of 100fs to 100ns.

[0024] Half-wave plate 2 is an infrared half-wave plate with operating wavelengths in the 1030nm, 1064nm, and 1342nm bands.

[0025] The working wavelengths of focusing lens 3 are 1030nm, 1064nm, and 1342nm.

[0026] Second harmonic crystal 4 consists of LBO, BBO, and KTP. Third harmonic crystal 5 consists of LBO, BBO, and CLBO.

[0027] The imaging ratio of the imaging lens 8 is less than or equal to 1, preferably 1:1, or 1:0.9 or 1:0.8.

[0028] The pulse width adjustable infrared laser 1 outputs pulse width adjustable infrared laser. After passing through the half-wave plate 2, the polarization of the infrared light is adjusted to be vertical polarization. The infrared light is focused by the focusing lens 3, and the focal point is located near the second harmonic crystal 4 and the third harmonic crystal 5. By adjusting the front and back positions of the focusing lens 3, the distance between the second harmonic crystal 4 and the third harmonic crystal 5, and the temperature of the second harmonic crystal 4 and the third harmonic crystal 5, the output ultraviolet light reaches the strongest. The infrared laser output by the third harmonic crystal 5 is blocked by the infrared light blocking block 6 after spatial transmission. The output green laser is blocked by the green light blocking block 7 after spatial transmission. The imaging lens 8 provided on the propagation path of the output ultraviolet laser has an imaging ratio of 1:1. The object plane of the imaging corresponds to the Brewster angle output surface of the third harmonic crystal 5. The image plane is located on the input surface of the wedge-shaped mirror 9. By slightly adjusting the distance between the imaging lens 8 and the third harmonic crystal 5 and the distance between the wedge-shaped mirror 9 and the imaging lens 8, the ultraviolet laser output by the wedge-shaped mirror 9 becomes circular and is output.

[0029] The pulse width adjustable infrared laser is focused to enhance the light intensity, realize third harmonic output, and reduce the probability of ultraviolet damage of the Brewster angle output surface of the third harmonic crystal 5. The infrared light, green light and ultraviolet light are also separated. The separated ultraviolet light is elliptical due to walk-off effect and wedge angle output. The wedge-shaped mirror 9 shapes the input elliptical spot of the wedge-shaped mirror to ensure that the elliptical ratio of the input elliptical spot of the wedge-shaped mirror is approximately equal to the elliptical ratio of the output spot of the third harmonic crystal. The imaging lens 8 between the third harmonic crystal 5 and the wedge-shaped mirror 9 performs imaging operation to facilitate shaping. The position of the imaging lens 8 is slightly adjusted to compensate for the spot elliptical caused by walk-off effect during frequency multiplication. While ensuring the output ultraviolet efficiency, the device is avoided from being damaged. The ultraviolet output is shaped into a better circular spot, and the optical path is simple and effective.

[0030] Embodiment

[0031] The adjustable pulse width infrared laser 1 outputs parameters of average power 108W, repetition frequency 200kHz, output light spot 2mm, output pulse width 2ns-7ns adjustable, and fixed pulse width 5ns. After the infrared light passes through the half wave plate 2, the polarization of the output infrared light is adjusted to be vertical polarization. The infrared light is focused after passing through the focusing lens 3. The focal length of the focusing lens is 250mm. The focal point after focusing is 170μm. The focal point is located in the middle of the second harmonic crystal 4 and the third harmonic crystal 5, close to the second harmonic crystal 4. The spacing between the focusing lens 3 and the second harmonic crystal 4 is 285mm. The spacing between the second harmonic crystal 4 and the third harmonic crystal 5 is 33mm. The temperature of the second harmonic crystal 4 is set to 50 DEG C. The temperature of the third harmonic crystal 5 is set to 45 DEG C. The highest average power of the output ultraviolet light is 44.6W. The infrared laser output by the third harmonic crystal 5 is blocked by the infrared light blocking block 6 after spatial transmission. The green light laser is blocked by the green light blocking block 7 after spatial transmission. The imaging lens 8 is arranged on the propagation path of the output ultraviolet laser. The focal length of the imaging lens 8 is 100mm. The spacing between the imaging lens 8 and the Brewster angle output surface of the third harmonic crystal 5 is 160mm. The material of the wedge-shaped mirror 9 is quartz. The cut angle is 56 DEG. The spacing between the wedge-shaped mirror 9 and the imaging lens 8 is 200mm. The ultraviolet laser becomes circular and is output.

[0032] The utility model discloses to the problem that the ultraviolet light beam of the focused light beam output of the adjustable pulse width laser cavity outside frequency multiplication is easy to cause the damage of the third harmonic crystal and the poor problem of the output light beam roundness, keeps the infrared part output of the adjustable pulse width laser unchanged, focuses the output light beam to the second harmonic crystal and the third harmonic crystal near through the lens, adopts the polished and plating antireflection film mode to handle the light transmission end face of the second harmonic crystal, adopts the polished and plating antireflection film mode to handle the incidence end face of the third harmonic crystal, and the output end face of the third harmonic crystal is cut to the Brewster angle and is not plated film. The infrared light beam and the green light of the third harmonic crystal output are blocked, and the ultraviolet output light beam is output after shaping through a lens and a wedge-shaped mirror in turn. The output end face of the third harmonic crystal is cut to the Brewster angle and is not plated film, reduces the ultraviolet damage probability of the output end face, separates the output infrared light, green light and ultraviolet light by using the different refractive index of different output wavelengths simultaneously. The ultraviolet light is output first through the lens to image the output end face, utilizes the principle of the wedge-shaped mirror shaping, combines the imaging light spot to make the output light beam be fine tuned to be circular, guarantees the consistency of the output.

[0033] In summary, the utility model discloses to realize the cavity outside frequency multiplication ultraviolet laser of high efficiency and high beam quality by the mode of focusing frequency multiplication and shaping output after imaging, guarantees the output efficiency, avoids the damage of the device, and can also keep the roundness of the output light spot, provides simple and effective implementation scheme for the cavity outside frequency multiplication ultraviolet laser of the same type.

[0034] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and thus once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0035] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and thus once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0036] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one from another entity or action without necessarily requiring or implying that the entities or actions are in any way actually related or ordered other than as expressly defined in the patent. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without limitation, an element preceded by "comprises... a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Claims

1. An extracorporeal frequency-doubled tunable pulse-width ultraviolet laser device, characterized by: The output light path of the pulse width adjustable infrared laser (1) is sequentially arranged with a half wave plate (2) and a focusing lens (3), the focusing lens (3) is connected with a second harmonic generation crystal (4), the second harmonic generation crystal (4) is connected with a third harmonic generation crystal (5), the output end surface of the third harmonic generation crystal (5) is cut at Brewster angle, the output infrared laser is shielded by an infrared light blocking block (6) after spatial transmission, the output green laser is shielded by a green light blocking block (7) after spatial transmission, the third harmonic generation crystal (5) is connected with an imaging lens (8), the imaging lens (8) is connected with the input surface of a wedge mirror (9), and the input surface of the wedge mirror (9) is cut at Brewster angle.

2. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device according to claim 1, characterized in that: The pulse width adjustable infrared laser (1) is an infrared laser with output wavelength of 1030nm, 1064nm and 1342nm wave band, output power of 1-500W and pulse width of 100fs-100ns.

3. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device of claim 1, wherein: The half wave plate (2) is an infrared half wave plate with working wavelength of 1030nm, 1064nm and 1342nm wave band.

4. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device according to claim 1, characterized in that: The working wavelength of the focusing lens (3) is 1030nm, 1064nm and 1342nm wave band.

5. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device according to claim 1, wherein: The second harmonic generation crystal (4) is LBO, BBO or KTP.

6. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device according to claim 1, characterized in that: The third harmonic generation crystal (5) is LBO, BBO or CLBO.

7. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device according to claim 1, wherein: The imaging ratio of the imaging lens (8) is less than or equal to 1.

8. The extra-cavity frequency-doubled adjustable pulse width ultraviolet laser device according to claim 7, characterized in that: The imaging ratio of the imaging lens (8) is 1:1, 1:0.9 or 1:0.8.

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