Packaging structure of mode-locked fiber laser

Abstract

The utility model relates to the field of laser packaging, in particular to a packaging structure of a mode-locked fiber laser, which comprises a first shell and a second shell which are of a rectangular frame structure, the first shell comprises a first shell, the upper surface of the first shell is provided with a first fixing groove, the first shell is provided with a first small hole and a second small hole, and the second shell is provided with a second fixing groove. The central axes of the first small hole, the second small hole and the first fixing groove are collinear; the second shell comprises a second shell body and a third fixing groove, the two ends of the third fixing groove are communicated with the second fixing groove and the fourth fixing groove respectively, a fifth fixing groove is communicated with the side edge of the third fixing groove, a third small hole and a fourth small hole are formed in the wall of the second shell body, and the fifth fixing groove and the third small hole are located on the same straight line. The third small hole is close to the fifth fixing groove, and the fourth small hole is formed in the shell wall close to the third fixing groove. According to the utility model, the fixing grooves are adopted to restrain the optical element in a multi-point manner, vibration displacement is reduced, stress is dispersed, deformation is prevented, and mode locking stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser package, in particular to a package structure of mode-locked fiber laser. BACKGROUND

[0002] Femtosecond laser is a kind of laser capable of generating ultra-short pulse (duration in femtosecond, i.e. 10 -15 Femtosecond laser is a kind of laser capable of generating ultra-short pulse (duration in femtosecond, i.e. 10

[0003] Passive mode-locking technology does not need external modulator, but uses nonlinear element or saturable absorber in laser cavity to realize mode-locking. When laser intensity reaches a certain degree, saturable absorber will selectively absorb light of certain frequency, thereby forming mode-locked pulse. Passive mode-locking, as an important way to generate ultra-short pulse, is concerned. Linear nonlinear deflection evolution mode-locked fiber laser has simple structure, and the resonant cavity is linear cavity, two spatial cavities are separated, and maintenance only needs to adjust the cavity that occurs problem, the other end is not affected, which is convenient to use and has the widest application range.

[0004] Traditional laser generally adopts standard optical support or screw fixing mode for packaging and fixing, and the position of optical element is easy to move. However, the mode-locked state of femtosecond laser is very sensitive to the position of optical element, and slight deviation will cause the light beam to deviate from the optimal path, resulting in mode-locking failure or efficiency reduction. Since femtosecond laser generates ultra-short pulse, its mode-locked state is extremely sensitive to the position of optical device, so the package must have extremely high mechanical stability to prevent slight displacement from causing optical path misalignment. That is, compared with ordinary continuous laser or pulsed laser, the fiber coupling and mode-locking mechanism of femtosecond laser require the package to provide more accurate optical element position to ensure long-term operation stability.

[0005] Therefore, the existing packaging method has poor stability, which easily causes the movement of optical element, makes it difficult for femtosecond laser to be coupled, and reduces the mode-locking efficiency. CONTENT OF THE INVENTION

[0006] The present application relates to the field of laser package, in particular to a package structure of mode-locked fiber laser.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] The application provides a packaging structure of a mode-locked fiber laser, which comprises a first shell and a second shell in a rectangular frame structure, the first shell comprises a first casing, the upper surface of the first casing is provided with a first fixing groove, the first casing is provided with a first small hole and a second small hole, the central axes of the first small hole, the second small hole and the first fixing groove are collinear; the second shell comprises a second casing and a third fixing groove, the third fixing groove is arranged in the second shell, the two ends of the third fixing groove are in communication with the second fixing groove and a fourth fixing groove respectively, a fifth fixing groove is in communication with the side edge of the third fixing groove, a third small hole and a fourth small hole are arranged on the wall of the second casing, the third fixing groove, the fifth fixing groove and the third small hole are on the same straight line, and the third small hole is close to the fifth fixing groove, and the fourth small hole is arranged on the shell wall adjacent to the third fixing groove.

[0009] In the mode-locked laser, the phase modulator (Faraday rotator + 1 / 8 wave plate), half-wave plate, polarization beam splitter prism, grating pair and collimator are important components, which determine the efficiency and quality of the laser mode-locked. In application, the first fixing groove is used to limit the phase modulator, the second fixing groove and the fifth fixing groove are used to limit the half-wave plate, the third fixing groove is used to limit the polarization beam splitter prism, and the fourth fixing groove is used to limit the grating pair; the first small hole and the fourth small hole are used to fix the collimator to ensure the collimation of the light path, and the two collimators are connected to the two ends of the gain fiber. In this way, the positions of the core components are limited, and the influence of the movement of the positions on the mode-locked process is prevented, and the mode-locked efficiency of the femtosecond laser is improved.

[0010] Further, the fourth fixing groove is in the shape of a parallelogram, and the groove width of the fourth fixing groove is the distance of the pre-placed grating pair.

[0011] Further, the directions of the second fixing groove and the fifth fixing groove are perpendicular to the direction of the light path; the widths of the second fixing groove and the fifth fixing groove are 1.01-1.05 times the diameter of the pre-placed half-wave plate.

[0012] Further, the fourth small hole is in communication with the second fixing groove, and the third small hole is in communication with the fifth fixing groove.

[0013] Further, the width of the first fixing groove is 1.01-1.05 times the diameter of the pre-placed Faraday rotator.

[0014] Further, the four corners of the first fixing groove are respectively provided with a machining groove, and the direction of the machining groove is the same as the depth direction of the first fixing groove.

[0015] Further, the first fixing groove is provided with a light-reflecting groove on the two side edges close to the first small hole and the second small hole, and the light-reflecting groove is arranged in the middle of the edge.

[0016] Further, the lower surface of the first and second shells are provided with outwardly extending feet; the thickness of the feet is 1.0 mm.

[0017] Further, the feet are rectangular in shape and are provided with through holes for fixing the first and second shells on a plane.

[0018] Further, a sixth fixing groove is arranged between the fourth through hole and the second fixing groove.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (1) By arranging a plurality of fixing grooves in the first and second shells, the optical element can be precisely positioned and constrained at multiple points, avoiding position deviation caused by vibration or thermal expansion; and the deviation caused by displacement is avoided. Compared with the traditional screw or pressing piece fixing method, the present application eliminates the displacement problem caused by installation error, so that the optical element can maintain a highly consistent coupling state and improve the mode-locked efficiency of femtosecond laser.

[0021] (2) The plurality of fixing grooves in the second shell are interconnected, dispersing mechanical stress and avoiding deformation caused by local stress, thereby ensuring the long-term stability of the optical element. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a top view of a first shell of a packaging structure of a mode-locked fiber laser according to the present application;

[0023] Figure 2 FIG. 2 is a perspective view of the first shell of the packaging structure of the mode-locked fiber laser according to the present application;

[0024] Figure 3 FIG. 3 is a top view of a second shell of the packaging structure of the mode-locked fiber laser according to the present application;

[0025] Figure 4 FIG. 4 is a perspective view of the second shell of the packaging structure of the mode-locked fiber laser according to the present application;

[0026] Figure 5 FIG. 5 is a schematic view of a packaged laser of the packaging structure of the mode-locked fiber laser according to the present application.

[0027] Icon: 1 - first housing; 11 - first fixed groove; 12 - first small hole; 13 - processing groove; 14 - light slot; 2 - second housing; 21 - second fixed groove; 22 - third fixed groove; 23 - fourth fixed groove; 24 - fifth fixed groove; 25 - sixth fixed groove; 26 - third small hole; 27 - fourth small hole; 28 - fifth small hole; 3 - leg. DETAILED DESCRIPTION

[0028] In order to make the implementation process of the utility model more clearly, the following will be combined with the drawings for detailed description.

[0029] The utility model provides a kind of packaging structure of mode-locked fiber laser, and packaging structure includes the first shell and second shell of rectangular frame structure.The material of first shell and second shell can be one of aluminum alloy, stainless steel, titanium alloy;Aluminum alloy has the advantages of light weight, good thermal conductivity, easy processing, can effectively dissipate heat, reduce the influence of temperature on optical element, while reducing overall weight;Titanium alloy has high strength, low thermal expansion coefficient, good shock resistance, suitable for extreme environment or high-precision laser system, ensure optical path stability.The first shell includes first housing 1, the top view schematic diagram of first housing 1 is as shown in Figure 1 The three-dimensional schematic diagram is as shown in Figure 2 The lower surface of first housing 1 is provided with outwardly extending leg 3, and leg 3 has four settings at two ends of side edge;The shape of leg 3 is rectangle, and through hole is provided on leg 3, and screw can be fixed first housing 1 on optical platform by passing through through hole, to reduce the movement of first shell 1.The thickness of leg 3 is 1.0 mm;If leg 3 is too thick, local thermal expansion and contraction will be caused by external stress or temperature change, so that slight deformation of the whole shell occurs, and then the relative position of optical element is affected, optical path is offset, and coupling efficiency is reduced;Leg 3 is 1.0 mm thin, and certain local buffering is generated when stressed, mechanical stress is absorbed, and stress is prevented from being transmitted to first housing 1, so that the overall deformation of shell is reduced, the accurate alignment of optical element is ensured, the mode-locked stability of femtosecond laser is improved, and long-term operation reliability is improved.Leg 3 is also provided in second housing 2, and the function is the same as here.Leg 3 can be used to fix first housing 1 and second housing 2 on optical platform.

[0030] The upper surface of the first shell 1 is provided with a first fixing groove 11, and the first shell 1 is provided with a first small hole 12 and a second small hole (not shown in the figure, which is opposite to the first small hole 12). The first small hole 12 and the second small hole are in communication with the first fixing groove 11, and can form an optical path. The central axes of the first small hole 12, the second small hole and the first fixing groove 11 are collinear; the laser can propagate along a straight line, and the central axis of the first fixing groove 11 refers to the central axis of the pre-placed Faraday rotator, that is, the straight line where the optical axis is located. The width of the first fixing groove 11 is 1.01-1.05 times the diameter of the pre-placed Faraday rotator. The depth of the first fixing groove 11 is slightly larger than the radius of the pre-placed Faraday rotator. The length of the first fixing groove 11 is slightly larger than the sum of the lengths of the pre-placed Faraday rotator and the 1 / 8 wave plate. This makes the Faraday rotator able to rotate around the optical axis, and the Faraday rotator needs to be rotated during the film locking process; and it will not produce radial or axial movement, avoiding the influence of movement on the coupling efficiency of the optical path.

[0031] Four corners of the first fixed groove 11 are respectively provided with a machining groove 13, the direction of the machining groove 13 is the same as the depth direction of the first fixed groove 11; it is convenient for machining by using a drill bit. In order to facilitate the observation of the light condition, the first fixed groove 11 is provided with a light checking groove 14 on the two sides close to the first small hole 12 and the second small hole, the light checking groove 14 is arranged in the middle of the side; the light checking groove 14 can observe the light path, improve the accuracy and efficiency of the light checking. The side wall of the first small hole 12 is provided with a thread, which is a threaded hole, which is used to fix the sleeve of the pre-placed integrated fiber wavelength division multiplexing collimator when in use, first tighten and fix the sleeve to the first small hole 12, and then fix it with high-temperature curing glue in the gap, and then the integrated fiber wavelength division multiplexing collimator is fixed with the sleeve through soldering. One end of the integrated fiber wavelength division multiplexing collimator outside the first shell is used to connect one end of the gain optical fiber and the pump laser diode; the collimated light output from the inside end enters the Faraday rotator connection. The outside of the second small hole is fixedly pasted with the first plane mirror, so that the laser is reflected at the first plane mirror to form oscillation; the other end of the oscillation cavity is a second plane mirror, and the second plane mirror is arranged on the second shell. In order to further improve the stability, the lower surface of the first shell 1 is provided with a rectangular groove recessed upward, the depth of the groove is 1.0mm, so as to reduce the influence of the deformation of the four supporting legs 3 on the first shell 1 and improve the stability of the laser. Specifically, when the supporting leg 3 is subjected to external force or temperature change, it will deform slightly. If it is directly connected to the first shell 1, the deformation will be transmitted to the whole shell, causing the position of the optical element to deviate, thereby affecting the light path coupling and the mode locking efficiency; by arranging a 1.0mm deep rectangular groove at the bottom of the shell, the rigidity connection degree of the supporting leg 3 and the first shell 1 can be reduced, so that the supporting leg 3 can partially release stress when deformed under stress, without being directly transmitted to the optical system; effectively reducing the interference of the external environment on the light path of the laser, improving the alignment accuracy of the optical element and the long-term stability of the system. The lower surface of the second shell 2 is also provided with a rectangular groove for improving stability.

[0032] The second shell includes a second shell 2, a second fixed groove 21, a third fixed groove 22, a fourth fixed groove 23, a fifth fixed groove 24, a third small hole 26, and a fourth small hole 27; the top view of the second shell is shown in Figure 3 The three-dimensional schematic view is shown in Figure 4The second fixing groove 21, the third fixing groove 22, the fourth fixing groove 23 and the fifth fixing groove 24 are arranged on the upper surface of the second shell 2 and form a communication space. The third small hole 26 and the fourth small hole 27 are arranged on the side wall of the second shell 2. The third fixing groove 22 is in a rectangular shape and is used for placing a polarization beam splitter. The width of the third fixing groove 22 is the same as the width of the polarization beam splitter. A scale line is arranged between the second fixing groove 21 and the third fixing groove 22 and is used for marking the polarization beam splitter. The scale line is processed according to the size of the polarization beam splitter and is used for marking the position of the polarization beam splitter. The two ends of the third fixing groove 22 (the transmission direction of the polarization prism) are respectively communicated with the second fixing groove 21 and the fourth fixing groove 23. The direction of the second fixing groove 21 is perpendicular to the light path and is used for placing a half-wave plate. The width of the second fixing groove 21 is 1.01-1.05 times the diameter of the half-wave plate, and the length of the second fixing groove 21 is 1.01-1.05 times the thickness of the half-wave plate, so as to ensure that the half-wave plate will not move during rotation. The fourth fixing groove 23 is in a parallelogram shape. The angle between the length direction of the fourth fixing groove 23 and the straight line on which the communication channel between the third fixing groove 22 and the fourth fixing groove 23 is located is 61°. In this way, the angle between the plane on which the grating is located and the light path is 61°, and the light splitting efficiency is relatively high. The width of the fourth fixing groove 23 is the distance between the grating pair. The two walls of the fourth fixing groove 23 are respectively pasted with gratings, and the two gratings form a grating pair. The gratings are arranged at the aperture through which the fourth fixing groove 23 is communicated with the third fixing groove 22, so that the light is transmitted through the gratings. The side wall of the second shell is provided with a sixth small hole (not shown in the figure). The grating away from the third fixing groove 22 in the grating pair is opposite to the sixth small hole and is coaxial and at the same height. The sixth small hole is communicated with the grating. The second plane mirror is pasted outside the sixth small hole, so that the laser is reflected and then enters the grating pair again, thereby forming oscillation, and the laser forms oscillation between the first plane mirror and the second plane mirror.

[0033] The fifth fixed groove 24 is communicated with the side of the third fixed groove 22 (the reflection direction of the polarization prism), the direction of the fifth fixed groove 24 is perpendicular to the light path direction, the width of the fifth fixed groove 24 is 1.01-1.05 times of the diameter of the pre-placed half-wave plate, the length is 1.01-1.05 times of the thickness of the half-wave plate, and the half-wave plate can freely rotate therein. The third small hole 26 and the fourth small hole 27 are arranged on the wall of the second shell 2. The third fixed groove 22, the fifth fixed groove 24 and the third small hole 26 are on the same straight line, and the third small hole 26 is close to the fifth fixed groove 24, and the third small hole 26 is communicated with the fifth fixed groove 24; the laser reflected by the polarization beam splitting prism can be output through the third small hole 26, that is, the light output hole of the laser. The fourth small hole 27 is arranged on the shell wall adjacent to the third fixed groove 22, and is communicated with the second fixed groove 21; the side wall of the fourth small hole 27 is provided with a thread, which is a threaded hole, which is used for fixing the sleeve of the collimator in use. First, the sleeve is tightly fixed to the fourth small hole 27, and then the sleeve is fixed by high-temperature curing glue, and then the collimator and the sleeve are fixed by soldering. The collimator is connected with the gain optical fiber at one end outside the second shell, and outputs the collimated light to irradiate on the half-wave plate. The third small hole 26 can also be a threaded hole, and the output light is converted into spatial light by the collimator.

[0034] In order to facilitate the coupling of the light adjusting light path, a coaxial sixth fixed groove 25 is further arranged between the fourth small hole 27 and the second fixed groove 21; a fifth small hole 28 is further arranged on the shell wall of the second shell, the fifth small hole 28 and the third small hole 26 are arranged on the same side wall, and the fifth small hole 28 is opposite to the sixth fixed groove 25. The sixth fixed groove 25 is used for placing a mirror with a 45° inclination angle in the light path, which adjusts the coupling efficiency of the spatial cavity without opening the optical fiber and without external light source. When the light is detected, the reflected light is emitted through the fifth small hole 28, the power of the reflected light is detected, and the angle of the collimating head is adjusted until the coupling efficiency is the highest. The seventh small hole is further arranged on the transmission direction of the sixth fixed groove 25, and the seventh small hole and the sixth small hole are arranged on the same side wall of the second shell 2. The seventh small hole is coaxially arranged with the second fixed groove 21 and the third fixed groove 22, and the laser passing through the mirror in the sixth fixed groove 25 can pass through the seventh small hole and be detected, so as to facilitate the adjustment of the light path. When the laser works, the mirror does not need to be placed in the sixth fixed groove 25.

[0035] Figure 5The figure is a schematic diagram of a packaged fiber laser. The two ends of the gain fiber (YDF) are connected to the first spatial light path section (corresponding to the first housing) and the second spatial light path section (corresponding to the second housing) respectively. The gain fiber is a ytterbium-doped gain fiber. From the end close to the gain fiber to the end far from the gain fiber, the first spatial light path section includes in sequence: an integrated fiber wavelength division multiplexing collimator (WDM-Collimator), a Faraday rotator (FR), a 1 / 8 wave plate (EWP), and a first plane mirror (M1). The laser emitted by the gain fiber is collimated by the integrated fiber wavelength division multiplexing collimator, enters the Faraday rotator and the 1 / 8 wave plate, the Faraday rotator and the 1 / 8 wave plate play the role of phase shifter, the laser transmitted through the 1 / 8 wave plate is reflected by the first plane mirror and then enters the 1 / 8 wave plate again, and then passes through the Faraday rotator and the integrated fiber wavelength division multiplexing collimator in sequence, and then enters the gain fiber. During packaging, the integrated fiber wavelength division multiplexing collimator and the Faraday rotator are fixed together and arranged in the first fixed groove 11, the first plane mirror is fixedly arranged outside the second small hole, the integrated fiber wavelength division multiplexing collimator is arranged in the first small hole 12 through a sleeve, and the outer side of the integrated fiber wavelength division multiplexing collimator is connected to the gain fiber and a pump laser diode (LD).

[0036] From the end close to the gain fiber to the end far from the gain fiber, the second spatial light path section includes in sequence: a collimator (Col), a half wave plate (HWP), a polarization beam splitter prism (PBS), a grating pair (Grating Pair), and a second plane mirror (M2). The laser emitted by the gain fiber is collimated by the collimator and then irradiates on the half wave plate, and then enters the polarization beam splitter prism after being transmitted through the half wave plate, the transmitted light of the polarization beam splitter prism passes through the grating pair, is reflected by the second plane mirror, and then enters the grating pair, the polarization beam splitter prism, the half wave plate, the collimator, and then enters the gain fiber. The pump source is a pump laser diode. The laser repeatedly oscillates between the first plane mirror and the second plane mirror, realizes gain in the gain fiber, and the film-locked laser is reflected from the polarization beam splitter prism and then output after passing through the half wave plate (arranged in the fifth fixed groove 24), that is, output from the third small hole 26. During packaging, the collimator is arranged in the fourth small hole 27, the half wave plate is arranged in the second fixed groove 21, the polarization beam splitter prism is arranged in the third fixed groove 22, the grating pair is arranged on the two side walls of the fourth fixed groove 23, and the second plane mirror is fixedly arranged outside the sixth small hole.

[0037] The two light path sections of the linear cavity are separated, and only the highest coupling efficiency of each is required. The loss of adjusting the light emitted by the integrated fiber wavelength division multiplexing collimator to be reflected back to the integrated fiber wavelength division multiplexing collimator by the first plane mirror is minimum; the loss of adjusting the light emitted by the collimator to be reflected back to the collimator by the second plane mirror is minimum, and the light circulates in the resonant cavity formed by the first plane mirror and the second plane mirror. Subsequent maintenance only needs to adjust the cavity that has problems, and the other end is not affected, and it is easy to adjust and maintain.

[0038] The first shell and the second shell of the application are independent of each other, and are connected together by a gain optical fiber in use. The shell has low requirements on the processing technology, can be processed at one time, and is easy to manufacture. The sixth fixing groove 25 can adjust the in-cavity coupling without breaking the optical fiber and without using an external light source. The overall size of the packaging structure is small, and is 63.6mmx59.1mmx23mm and 46mmx56.9mmx13.5mm respectively, so that the miniaturization of the femtosecond laser is realized.

[0039] The above is only a preferred embodiment of the application and is not used to limit the application. For those skilled in the art, the application can be variously changed and modified. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A package structure of a mode-locked fiber laser, the package structure comprising a first housing and a second housing in a rectangular frame structure, characterized in that, The first shell comprises a first shell body, an upper surface of the first shell body is provided with a first fixing groove, the first shell body is provided with a first small hole and a second small hole, the center axes of the first small hole, the second small hole and the first fixing groove are collinear; the second shell comprises a second shell body and a third fixing groove, the third fixing groove is arranged in the second shell body, two ends of the third fixing groove are in communication with a second fixing groove and a fourth fixing groove respectively, a fifth fixing groove is in communication with a side of the third fixing groove, a third small hole and a fourth small hole are arranged on a wall of the second shell body, the third fixing groove, the fifth fixing groove and the third small hole are on the same straight line, and the third small hole is close to the fifth fixing groove, and the fourth small hole is arranged on a shell wall adjacent to the third fixing groove.

2. The packaging structure of the mode-locked fiber laser according to claim 1, wherein, The fourth fixing groove is in the shape of a parallelogram, and a groove width of the fourth fixing groove is a distance of a preset grating pair.

3. The packaging structure of the mode-locked fiber laser according to claim 2, characterized in that, The second fixing groove and the fifth fixing groove are perpendicular to a light path direction, and widths of the second fixing groove and the fifth fixing groove are 1.01-1.05 times of a diameter of a preset half-wave plate.

4. The packaging structure of the mode-locked fiber laser according to claim 3, characterized in that, The fourth small hole is in communication with the second fixing groove, and the third small hole is in communication with the fifth fixing groove.

5. The packaging structure of the mode-locked fiber laser according to claim 4, characterized in that, A width of the first fixing groove is 1.01-1.05 times of a diameter of a preset Faraday rotator.

6. The packaging structure of the mode-locked fiber laser according to claim 5, wherein, Four corners of the first fixing groove are respectively provided with a machining groove, and a direction of the machining groove is the same as a depth direction of the first fixing groove.

7. The packaging structure of the mode-locked fiber laser according to claim 6, characterized in that, The first fixing groove is provided with a light guiding groove on two side edges close to the first small hole and the second small hole, and the light guiding groove is arranged in the middle of the edge.

8. The packaging structure of the mode-locked fiber laser according to claim 7, characterized in that, Lower surfaces of the first shell and the second shell are both provided with a support extending outward, and a thickness of the support is 1.0 mm.

9. The packaging structure of the mode-locked fiber laser according to claim 8, characterized in that, The support is in the shape of a rectangle, and a through hole is arranged on the support to fix the first shell and the second shell on a plane.

10. The packaging structure of the mode-locked fiber laser according to claim 9, wherein, The fourth small hole and the second fixing groove are further provided with a sixth fixing groove.

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