A short cavity structure for realizing double-locked high-repetition-rate femtosecond laser

Abstract

The present invention discloses a short cavity structure for achieving dual locking of high-repetition-rate femtosecond lasers. The short cavity structure comprises a metal bottom box, a metal top box, a temperature detection element, a piezoelectric actuator, a semiconductor refrigeration plate, and a gain fiber. The metal bottom box and the metal top box are provided with grooves for fixing the gain fiber. The piezoelectric actuator is fixed in the cutout of the metal bottom box and achieves rapid locking of the laser resonant cavity output pulse repetition rate by stretching the gain fiber. The gain fiber is fixed to the upper surface of the piezoelectric actuator. The temperature sensing area of ​​the temperature sensing element is placed in the side opening of the metal bottom box. The cooling surface of the semiconductor refrigeration plate is bonded to the bottom surface of the metal bottom box to suppress the influence of ambient temperature changes on the laser resonant cavity output pulse repetition rate, thereby achieving slow locking of the laser resonant cavity repetition rate. The present invention overcomes the sensitivity of the short cavity laser output pulse repetition frequency to the environment and achieves long-term and precise locking of the short cavity laser output pulse repetition frequency.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber laser technology, in particular to a short cavity structure for realizing double-locked high-repetition-rate femtosecond laser. Background Art

[0002] Pulsed lasers, as a vital resource, have significant applications in biomedicine, optical communication networks, industrial processing, basic research, and military defense. The repetition rate of laser pulses, a key performance metric, significantly impacts their application value. In optical communication networks, pulsed lasers, serving as information carriers, contribute significantly to the establishment of high-speed optical communication networks by increasing their pulse repetition rate. In laser material processing, thermal diffusion during processing not only causes energy loss but also affects processing precision. Shortening the temporal interval between laser pulses, allowing the ablation process to enter the "ablation cooling" regime, is a key solution to this problem. Given the impact of pulse repetition rate, achieving high-repetition-rate pulse output has become a crucial area of ​​laser research. Among implementation options such as vertical-cavity surface-emitting lasers, rational harmonic mode locking, active mode locking, and extracavity frequency doubling, short-cavity fiber laser technology holds the most promise due to its compact structure, excellent beam quality, low cost, and robustness. Increasing the repetition rate of the fundamental frequency of the resonant cavity output pulses presents the challenge of increasing the sensitivity of the output pulse performance to environmental factors. Specifically for short-cavity fiber lasers, the same environmental changes, including cavity temperature and mechanical vibration, will cause a greater change in the repetition rate of the short-cavity output pulse compared to laser cavities with repetition rates of tens or hundreds of MHz (R. Paschotta, Noise of mode-locked lasers (Part 1): numerical model, Appl.Phys. B 79, 153-164(2004). R. Paschotta, Timing jitter and phase noise ofmode-locked fiber lasers, Opt. Express 18(5), 5041-5054(2010).). Due to the limitation of the cavity length (cavity length less than 10 cm) of short-cavity pulse lasers with repetition rates in the GHz range, it is not possible to use the common technology of adding an electro-optical modulator to the cavity to stabilize the repetition rate of lasers with repetition rates of tens or hundreds of MHz. Therefore, how to suppress the sensitivity of the pulse repetition rate to the environment in short-cavity fiber laser technology and achieve highly stable pulse laser output is an urgent problem to be solved. Summary of the Invention

[0003] The present invention aims to address the high sensitivity of high-repetition-rate short laser cavities to environmental disturbances, enabling them to output pulse trains with stable repetition rates. The proposed chimeric structure effectively isolates the fiber laser resonator from the environment; furthermore, the fast and slow dual-locking design of the structure further enhances the stability of the laser cavity's output pulse repetition rate.

[0004] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0005] A short cavity structure for realizing double-locked high-repetition-rate femtosecond laser, comprising a metal bottom box, a metal top box, a temperature detection element, a piezoelectric actuator, a semiconductor refrigeration sheet, and a gain fiber;

[0006] Among them, the metal bottom box and the metal top box are provided with grooves for fixing the gain fiber in the high-repetition-rate laser resonant cavity. The metal bottom box and the metal top box are connected by screws to form a metal box, and the gain fiber is clamped between the two; the piezoelectric actuator is fixed in the incision of the metal bottom box, and the laser resonant cavity output pulse repetition rate is quickly locked by stretching the gain fiber; the gain fiber is fixed to the upper surface of the piezoelectric actuator; the temperature sensing area of ​​the temperature sensing element is placed in the side opening of the metal bottom box for monitoring the temperature of the metal box; the cooling surface of the semiconductor refrigeration plate is in contact with the bottom surface of the metal bottom box for stabilizing the temperature inside the metal box, so as to suppress the influence of ambient temperature changes on the laser resonant cavity output pulse repetition rate and achieve slow locking of the laser resonant cavity repetition rate.

[0007] Furthermore, the materials used for the metal bottom box and the metal top box include aluminum, aluminum alloy, brass or copper, which helps to enhance heat conduction between the fiber laser resonant cavity and the metal box, thereby suppressing the influence of temperature jitter on the output pulse repetition rate of the laser resonant cavity by controlling the temperature of the metal box.

[0008] Furthermore, in order to ensure the compactness of the overall structure of the metal box, the metal bottom box is provided with standard threaded holes of size M1 or M2, and the number of threaded holes is 6, of which the opening positions of the four threaded holes are symmetrically distributed at the four corners of the bottom box to increase the stability of the metal box structure. Two more threaded holes are opened along the central axis 3-6 cm inward of the structural member at the two threaded openings on the side where the temperature detection element is provided; the metal top box has corresponding screw holes at the corresponding positions, and the metal bottom box and the metal top box are connected by screws to form a metal box, thereby fixing the gain fiber in the high repetition rate laser resonant cavity. The laser resonant cavity will be in a relatively closed space, which helps to reduce the impact of the environment.

[0009] Furthermore, the grooves provided on the metal bottom box and the metal top box are used to fix the gain fiber in the high-repetition-rate laser resonant cavity; the grooves can tightly accommodate the metal tail handle of a common ferrule, and placing the gain fiber in the laser resonant cavity tightly in the grooves helps to reduce the impact of environmental jitter on the fiber.

[0010] Furthermore, the piezoelectric actuator is fixed in the cutout of the metal bottom box by means of a room-temperature curing epoxy resin adhesive; the piezoelectric actuator is perpendicular to the central axis of the two end faces and parallel to the central axis of the metal bottom box perpendicular to the two end faces; one end of the piezoelectric actuator is fixed to one end of the cutout by means of a room-temperature curing epoxy resin adhesive, ensuring that the two end faces are parallel to each other during the fixing process; the other end is a free end;

[0011] The piezoelectric actuator must have sufficient stroke and dynamic response range to quickly respond to instantaneous changes in the pulse repetition rate of the laser resonant cavity output; the piezoelectric actuator is a linear small multilayer piezoelectric ceramic actuator with a maximum stroke of 1~10 μm, a resonant frequency greater than 10 kHz, and a length less than 5 cm.

[0012] Furthermore, the gain fiber with the coating stripped in the high repetition frequency resonant cavity is adhered to the surface of the piezoelectric actuator along the direction perpendicular to the center line of the two ends of the piezoelectric ceramic by using a room temperature curing epoxy resin adhesive. The gain fiber and the piezoelectric actuator are point-bonded, and the bonding points are located at the axial ends of the piezoelectric actuator.

[0013] Furthermore, the temperature detection element is a thermistor with a linear temperature coefficient, the operating temperature range of the temperature detection element is -5°C to 40°C, the resistance accuracy is better than 5%, and the lateral size of the sensing area is less than 2mm.

[0014] Furthermore, the temperature sensing area of ​​the temperature sensing element is placed in the side opening of the metal base box, and the opening is filled with thermal grease between the temperature sensing element to provide feedback on the temperature inside the metal box. The filled thermal grease can more accurately reflect the temperature of the metal box; the center of the side opening is located at the center of the metal base box in the vertical direction, and the horizontal distance from the end surface of one side where the temperature sensing element is provided is 8-10 mm, the diameter of the side opening is 1-3 mm, and the depth of the side opening is 2-5 mm.

[0015] Furthermore, the cooling surface of the semiconductor refrigeration plate is fitted with the bottom groove of the metal bottom box along the central axis, and the cooling surface of the semiconductor refrigeration plate can completely cover the bottom groove of the metal bottom box, and thermal conductive silicone grease is used to fill the space between the two. The semiconductor refrigeration plate uses the Peltier effect of the semiconductor to achieve temperature regulation, and promotes heat exchange between the semiconductor refrigeration plate and the metal bottom box through the thermal conductive silicone grease, thereby achieving effective control of the temperature of the metal box; the temperature range of the semiconductor refrigeration plate is 0~40℃.

[0016] The advantages of the present invention are:

[0017] In short-cavity femtosecond lasers, the dual locking technology based on temperature control technology and rapid stretching of the gain fiber in the piezoelectric ceramic resonant cavity overcomes the sensitivity of the short-cavity laser output pulse repetition frequency to the environment and achieves long-term precise locking of the short-cavity laser output pulse repetition frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a three-dimensional structural diagram of a short cavity structure for realizing double-locked high-repetition-rate femtosecond laser in an embodiment of the present invention;

[0019] Figure 2 This is a top view of the three-dimensional structure of the short cavity structure for realizing double-locked high-repetition-rate femtosecond laser in an embodiment of the present invention, after removing the metal top box;

[0020] Figure 3 This is a bottom view of the three-dimensional structure of the short cavity structure for realizing double-locked high-repetition-rate femtosecond laser in an embodiment of the present invention, after removing the metal top box;

[0021] Figure 4 This is a three-dimensional structural diagram of the metal top box in the short cavity structure of the double-locked high repetition rate femtosecond laser in the embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific implementation of the present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0023] Example:

[0024] A short cavity structure for realizing double-locked high repetition rate femtosecond laser, such as Figure 1 As shown, it includes a metal bottom box 1, a metal top box 2, a temperature detection element 3, a piezoelectric actuator 4, a semiconductor refrigeration sheet 5 and a gain optical fiber 6;

[0025] Among them, the metal bottom box 1 and the metal top box 2 are provided with grooves for fixing the gain optical fiber in the high repetition rate laser resonant cavity. The metal bottom box 1 and the metal top box 2 are connected by screws to form a metal box, and the gain optical fiber is clamped between the two; the piezoelectric actuator 4 is fixed in the incision of the metal bottom box, and the laser resonant cavity output pulse repetition rate is quickly locked by stretching the gain optical fiber; the gain optical fiber 6 is fixed on the upper surface of the piezoelectric actuator 4; the temperature sensing area of ​​the temperature sensing element 3 is placed in the side opening of the metal bottom box 1 for monitoring the temperature of the metal box; the cooling surface of the semiconductor refrigeration plate 5 is in contact with the bottom surface of the metal bottom box 1 for stabilizing the temperature inside the metal box, so as to suppress the influence of ambient temperature changes on the laser resonant cavity output pulse repetition rate and achieve slow locking of the laser resonant cavity repetition rate.

[0026] The materials used for the metal bottom box 1 and the metal top box 2 include aluminum, aluminum alloy, brass or copper, which helps to enhance the heat conduction between the fiber laser resonant cavity and the metal box, thereby suppressing the influence of temperature jitter on the output pulse repetition rate of the laser resonant cavity by controlling the temperature of the metal box.

[0027] like Figure 1 As shown, in order to ensure the compactness of the overall structure of the metal box, the metal bottom box 1 is provided with standard threaded holes of size M1 or M2, and the number of threaded holes is 6. The opening positions of the four threaded holes are symmetrically distributed at the four corners of the bottom box to increase the stability of the metal box structure. Two more threaded holes are opened along the central axis 3-6 cm inward of the structural member at the two threaded openings on the side where the temperature detection element 3 is provided; the metal top box 2 has corresponding screw holes at the corresponding positions, and the metal bottom box 1 and the metal top box 2 are connected by screws to form a metal box, thereby fixing the gain fiber in the high repetition rate laser resonant cavity. The laser resonant cavity will be in a relatively closed space, which helps to reduce the impact of the environment.

[0028] like Figure 2 、 Figure 4 As shown, the grooves provided on the metal bottom box 1 and the metal top box 2 are used to fix the gain fiber in the high repetition rate laser resonant cavity; the grooves can tightly accommodate the metal tail handle of a common ferrule, and placing the gain fiber in the laser resonant cavity tightly in the grooves helps to reduce the impact of environmental jitter on the fiber.

[0029] like Figure 2 As shown, the piezoelectric actuator 4 is fixed in the cutout of the metal bottom box 1 by means of a room-temperature curing epoxy resin adhesive. The piezoelectric actuator 4 is perpendicular to the central axis of the two end faces and parallel to the central axis of the metal bottom box 1 perpendicular to the two end faces. One end of the piezoelectric actuator 4 is fixed to one end of the cutout by means of a room-temperature curing epoxy resin adhesive, ensuring that the two end faces are parallel to each other. The other end is a free end.

[0030] The piezoelectric actuator 4 must have sufficient stroke and dynamic response range to quickly respond to instantaneous changes in the laser cavity output pulse repetition rate; the piezoelectric actuator 4 is a linear small multilayer piezoelectric ceramic actuator with a maximum stroke of 1~10 μm, a resonance frequency greater than 10 kHz, and a length less than 5 cm.

[0031] like Figure 2 As shown, the gain fiber 6 with the coating stripped in the high repetition frequency resonant cavity is adhered to the surface of the piezoelectric actuator 4 along the direction perpendicular to the center line of the two ends of the piezoelectric ceramic 4 by room temperature curing epoxy resin adhesive. The gain fiber and the piezoelectric actuator 4 are point-bonded, and the bonding points are located at the two axial ends of the piezoelectric actuator 4.

[0032] The temperature detection element 3 is a thermistor with a linear temperature coefficient. The operating temperature range of the temperature detection element 3 is -5°C to 40°C, the resistance accuracy is better than 5%, and the lateral size of the sensing area is less than 2mm.

[0033] like Figure 2 As shown, the temperature sensing area of ​​the temperature sensing element 3 is placed in the side opening of the metal base box 1. The opening is filled with thermal grease between the temperature sensing element to provide feedback on the temperature inside the metal box. The filled thermal grease can more accurately reflect the temperature of the metal box. The center of the side opening is located at the center of the metal base box 1 in the vertical direction, and the horizontal distance from the end surface of one side where the temperature sensing element 3 is provided is 8-10 mm. The diameter of the side opening is 1-3 mm, and the depth of the side opening is 2-5 mm.

[0034] like Figure 3 As shown, the cooling surface of the semiconductor refrigeration sheet 5 is fitted with the bottom groove of the metal bottom box 1 along the central axis, and the cooling surface of the semiconductor refrigeration sheet 5 can completely cover the bottom groove of the metal bottom box 1, and thermal conductive silicone grease is used to fill the space between the two. The semiconductor refrigeration sheet 5 uses the Peltier effect of the semiconductor to achieve temperature regulation, and the thermal conductive silicone grease promotes heat exchange between the semiconductor refrigeration sheet 5 and the metal bottom box 1, thereby achieving effective control of the temperature of the metal box; the temperature range of the semiconductor refrigeration sheet 5 is 0~40 ℃.

[0035] The frequency stability in a short period of time after the double locking method of the present invention was tested. In this embodiment, the maximum frequency deviation within 1 minute did not exceed 30 mHz (the basic repetition frequency of the pulse was 1.27 GHz).

[0036] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A short cavity structure for realizing double-locked high repetition rate femtosecond laser, characterized in that: It comprises a metal bottom box (1), a metal top box (2), a temperature detection element (3), a piezoelectric actuator (4), a semiconductor cooling sheet (5) and a gain optical fiber (6); The metal bottom box (1) and the metal top box (2) are provided with grooves for fixing the gain optical fiber (6) in the high repetition rate laser resonant cavity. The metal bottom box (1) and the metal top box (2) are connected by screws to form a closed metal box, and the gain optical fiber (6) is clamped between the two. The piezoelectric actuator (4) is fixed in the cutout of the metal bottom box (1) by a room temperature curing epoxy resin adhesive. The piezoelectric actuator (4) is a linear small multilayer piezoelectric ceramic actuator with a maximum stroke of 1 to 10 μm, a resonance frequency greater than 10 kHz, and a length less than 5 cm. The gain optical fiber (6) is point-bonded to the upper surface of the piezoelectric actuator (4) by a room temperature curing epoxy resin adhesive in a direction perpendicular to the center line of the two ends of the piezoelectric actuator (4). The bonding point is located at the axis of the piezoelectric actuator (4). Towards both ends; the temperature detection element (3) is a thermistor with a linear temperature coefficient, with an operating temperature range of -5°C to 40°C, a resistance accuracy of better than 5%, and a lateral dimension of the sensing area of ​​less than 2mm. The temperature sensing area is placed in the side opening of the metal bottom box (1), and thermal grease is filled between the opening and the temperature detection element; the cooling surface of the semiconductor refrigeration sheet (5) is fitted with the groove of the bottom surface of the metal bottom box (1) along the central axis and completely covers the groove, and thermal grease is filled between the two; the piezoelectric actuator (4) is perpendicular to the central axis of the two end faces and parallel to the central axis of the metal bottom box (1) perpendicular to the two end faces. One end of the piezoelectric actuator (4) is fixed to one end of the cutout by a room temperature curing epoxy resin adhesive, and the two end faces are ensured to be parallel to each other when fixed; the other end is a free end; The metal bottom box (1) is provided with a total of 6 standard threaded holes of size M1 or M2, 4 of which are symmetrically distributed at the four corners of the bottom box, and 2 additional threaded holes are provided 3-6 cm inward along the central axis of the two threaded holes on the side where the temperature detection element (3) is provided; screw holes are provided at corresponding positions of the metal top box (2), and the metal box is formed by screw connection; the center of the side opening is located at the center of the metal bottom box (1) in the vertical direction, and the horizontal distance from the end face of the side where the temperature detection element (3) is provided is 8-10 mm; the diameter of the side opening is 1-3 mm, and the depth of the side opening is 2-5 mm.

2. The short cavity structure for realizing double-locked high repetition rate femtosecond laser according to claim 1, characterized in that: The materials used for the metal bottom box (1) and the metal top box (2) include aluminum, aluminum alloy, brass or copper.

3. The short cavity structure for realizing double-locked high repetition rate femtosecond laser according to claim 1, characterized in that: The grooves provided on the metal bottom box (1) and the metal top box (2) are used to fix the gain optical fiber in the high repetition rate laser resonant cavity; the grooves can tightly accommodate the metal tail handle of a common ferrule.

4. The short cavity structure for realizing double-locked high repetition rate femtosecond laser according to claim 1, characterized in that: The gain optical fiber (6) with the coating stripped in the high repetition frequency resonant cavity is adhered to the surface of the piezoelectric actuator (4) along the direction perpendicular to the center line of the two ends of the piezoelectric actuator (4) by means of a room temperature curing epoxy resin adhesive. The gain optical fiber and the piezoelectric actuator (4) are point-bonded, and the bonding points are located at the two axial ends of the piezoelectric actuator (4).

5. The short cavity structure for realizing double-locked high repetition rate femtosecond laser according to claim 1, characterized in that: The cooling surface of the semiconductor cooling sheet (5) is fitted with the groove on the bottom surface of the metal bottom box (1) along the central axis. The semiconductor cooling sheet (5) uses the Peltier effect of the semiconductor to achieve temperature regulation. The heat exchange between the semiconductor cooling sheet (5) and the metal bottom box (1) is promoted by thermal grease, thereby achieving effective control of the temperature of the metal box. The temperature range of the semiconductor cooling sheet (5) is 0~40℃.

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