KR20200052784A - Fiber femtosecond laser apparatus - Google Patents

Abstract

The present invention relates to an optical fiber femtosecond laser apparatus and, more specifically, to an optical fiber femtosecond laser apparatus in which an optical loss adjustment unit is disposed in an oscillator of the optical fiber femtosecond laser apparatus to adjust an optical loss in accordance with a wavelength, thereby easily adjusting an error in the central wavelength of a laser even if the error occurs due to characteristic deviation in each component forming the oscillator. According to the present invention, the optical fiber femtosecond laser apparatus comprises the oscillator to generate the laser. The oscillator comprises: a gain optical fiber amplifying the layer at an amplification ratio in accordance with the wavelength; a pumping light source performing pumping to operate the gain optical fiber; and the loss adjustment unit adjusting the optical loss in accordance with the wavelength. Accordingly, the optical loss in accordance with the wavelength in the oscillator is adjusted by the optical loss adjustment unit, thereby adjusting the central wavelength of the laser generated by mode-locking.

Description

Fiber optic femtosecond laser device {FIBER FEMTOSECOND LASER APPARATUS}

The present invention relates to an optical fiber femtosecond laser device, and more specifically, an optical loss adjusting unit is provided in a resonator of an optical fiber femtosecond laser device to control optical loss according to wavelength, thereby resulting in variation in characteristics in each component constituting the resonator. Therefore, even if an error occurs in the center wavelength of the laser, the present invention relates to an optical fiber femtosecond laser device that can be easily adjusted.

Fiber optic femtosecond laser devices are mostly composed of optical fibers, so they are simple to configure, easy to operate and insensitive to environmental changes, and can be operated for a long time. Using fiber optic components in the communication band, low price and utilization in the communication band, etc. It has several advantages that are good for industrial application.

More specifically, the optical fiber femtosecond laser can be divided into a normal dispersion region and an abnormal dispersion region according to the dispersion value of the optical fiber according to the band of the oscillation wavelength, and the length of the wavelength is smaller than 1300 nm. In the case, since the dispersion value D has a negative value corresponding to the normal dispersion region, the width on the time axis of the ultrashort pulse generated by the optical fiber femtosecond laser continues to widen as the optical fiber progresses. Accordingly, passive mode locking is used to induce oscillation of an optical fiber femtosecond laser while gaining while maintaining the microwave.

In the passive mode lock, an absorbent saturable (Saturable Absorber, SA), a semiconductor-based saturable absorber mirror (SEMIconductor Saturable Absorber Mirror, SESAM), a nonlinear polarization rotation (Nonlinear Polarization Rotation, NPR), etc. may be used, and generally a saturated absorber ( SA) or a fiber-based femtosecond laser of ring type (Fig. 1 (a)) or Fabry-Parot type (Fig. 1 (b)) mainly using a semiconductor-based saturated absorber mirror (SESAM) The resonator is constructed.

More specifically, the mode lock of the optical fiber femtosecond laser is generated by the number of razing modes created by the balance of gain and loss according to the optical characteristics of various components present in the resonator.

However, the center wavelength of the optical fiber femtosecond laser generated by the mode lock is difficult to accurately match the design value or calculation value due to the characteristic variation in each component, resulting in an error.

Furthermore, in the case of a hybrid type high-power femtosecond laser system using a fiber optic femtosecond laser resonator as a master oscillator and using a solid amplification stage, matching the center wavelength of the master oscillator and the solid amplification stage becomes very important to obtain high power.

For a more specific example, a Yb: YAG material having a high emission spectral characteristic at 1030nm as a solid gain medium has a high gain and is used as a high output gain medium, but the center wavelength is 1030nm and the band width should be 4nm or less, so the center of the master oscillator The difficulty is that efficient amplification can be achieved only when the wavelength is within 1030 nm +/- 2 nm.

On the other hand, various techniques are used to accurately adjust the center wavelength of the optical fiber femtosecond laser resonator, and a typical example is a method using a grating, but this is a wavelength in which the grating is easily manufactured, such as when the center wavelength is 1550 nm. Not only can it be applied in the band, but even if it is possible to fabricate a grid, there are still problems in terms of cost and stability.

Accordingly, there is an urgent need for the development of an optical fiber femtosecond laser device that can easily adjust the center wavelength of an optical fiber femtosecond laser generated by mode lock even if an error occurs due to a characteristic variation in each component.

Republic of Korea Patent Publication No. 10-2012-0058275 (published on June 7, 2012)

The present invention was devised to solve the problems of the prior art as described above, and even if an error occurs due to a characteristic deviation in each component of a central wavelength of an optical fiber femtosecond laser generated by mode locking, it can be easily adjusted. It is an object to provide an optical fiber femtosecond laser device.

Other detailed objects of the present invention will be clearly understood and understood by experts or researchers in this technical field through specific contents described below.

An optical fiber femtosecond laser device according to an aspect of the present invention for solving the above problems is provided in an optical fiber femtosecond laser device having a resonator to generate a laser, comprising: a gain fiber for amplifying a laser at an amplification ratio according to a wavelength; A pumping light source that pumps the gain optical fiber so that it can be driven; And a light loss adjusting unit that adjusts light loss according to a wavelength; and a resonator comprising a light-adjusting light loss according to a wavelength in the resonator by using the light loss adjusting unit, to mode-locking. It is characterized by adjusting the center wavelength of the laser generated by.

In this case, the optical loss adjusting unit may adjust the optical loss in the resonator by using the bending loss of the optical fiber included in the resonator.

Furthermore, the optical loss adjusting unit may control the optical loss in the resonator by adjusting the curvature or number of turns of the optical fiber included in the resonator.

More specifically, the optical loss adjusting unit may control the optical loss in the resonator by using an optical loss adjusting structure capable of adjusting the curvature or number of turns of the optical fiber.

Further, the resonator may be a ring type resonator including a saturable absorber.

Further, the resonator may be a Fabry-Parot type resonator including a semiconductor-based saturable absorber mirror.

In addition, the optical fiber femtosecond laser device further includes a solid-state amplification stage for amplifying the laser generated by the resonator, and the optical loss adjusting unit can adjust the center wavelength of the resonator to match the solid-state amplification stage and the center wavelength. .

Accordingly, in the optical fiber femtosecond laser device according to an embodiment of the present invention, an optical loss adjusting unit is provided in a resonator of an optical fiber femtosecond laser device to control optical loss according to wavelength, thereby characteristic in each component constituting the resonator. Even if an error occurs in the center wavelength of the laser due to the deviation, it can be easily adjusted.

The accompanying drawings, which are included as part of the detailed description to aid understanding of the present invention, provide embodiments of the present invention and describe the technical spirit of the present invention together with the detailed description.
1 illustrates an optical fiber femtosecond laser device according to the prior art.
2 is a configuration diagram of an optical fiber femtosecond laser device according to an embodiment of the present invention.
Figure 3 shows an implementation of an optical fiber femtosecond laser device according to an embodiment of the present invention.
4 illustrates the operation of an optical fiber femtosecond laser device according to an embodiment of the present invention.
5 shows an implementation of an optical loss adjusting unit in an optical fiber femtosecond laser device according to an embodiment of the present invention.
6 shows measurements showing a central wavelength shift by an optical fiber femtosecond laser device according to an embodiment of the present invention.

The present invention can be applied to various transformations and can have various embodiments. Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings.

The following examples are provided to aid in a comprehensive understanding of the methods, devices and / or systems described herein. However, this is only an example and the present invention is not limited thereto.

In describing the embodiments of the present invention, when it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or practice. Therefore, the definition should be made based on the contents throughout this specification. The terminology used in the detailed description is only for describing embodiments of the present invention and should not be limiting. Unless expressly used otherwise, a singular form includes a plural form. In this description, expressions such as “including” or “equipment” are intended to indicate certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and one or more other than described. It should not be interpreted to exclude the presence or possibility of other characteristics, numbers, steps, actions, elements, or parts or combinations thereof.

Further, terms such as first and second may be used to describe various components, but the components are not limited by the terms, and the terms are used to distinguish one component from other components. Used only.

Hereinafter, exemplary embodiments of the optical fiber femtosecond laser apparatus 10 according to an embodiment of the present invention will be described in turn with reference to the accompanying drawings.

First, FIG. 2 is a block diagram of an optical fiber femtosecond laser device 10 according to an embodiment of the present invention. As can be seen in Figure 2, the optical fiber femtosecond laser device 10 according to an embodiment of the present invention, a gain optical fiber (gain fiber) 110 for amplifying the laser at an amplification ratio according to the wavelength, the gain optical fiber 110 ) Is provided with a resonator 100 including a pumping light source 120 for pumping so that it can be driven, and the light loss adjusting unit 130 for controlling light loss according to wavelength. By adjusting the light loss according to the wavelength in the resonator 100 using the adjusting unit 130, the center wavelength of the laser generated by mode-locking is adjusted.

At this time, the optical loss adjusting unit 130 may adjust the optical loss in the resonator 100 by using the bending loss of the optical fiber included in the resonator 100.

Accordingly, in the optical fiber femtosecond laser device 10 according to an embodiment of the present invention, the resonator 100 using the optical loss adjusting unit 130 provided in the resonator 100 of the optical fiber femtosecond laser device 10 By adjusting the optical loss according to the wavelength at, even if an error occurs in the central wavelength of the laser due to the characteristic variation in each component constituting the resonator 100, it can be easily adjusted.

More specifically, FIG. 3 shows an implementation of an optical fiber femtosecond laser device 10 according to an embodiment of the present invention.

Hereinafter, an optical fiber femtosecond laser device 10 according to an embodiment of the present invention will be divided for each configuration and examined in more detail with reference to FIGS. 2 and 3.

First, the gain fiber 110 gains a laser at an amplification ratio according to a wavelength so that resonance can occur in the resonator 100.

In addition, a pumping light source 120 is provided in the resonator 100 to pump the gain optical fiber 110 to be driven.

At this time, the resonator 100 may be provided with a wavelength division multiplexing 140 connecting the pumping light source 120 to the resonator 100.

Further, the resonator 100 may be provided with an output coupler 150 for drawing the generated laser to the outside.

Furthermore, the resonator 100 may have necessary resonant structures and components according to the resonant type. More specifically, in the ring type, as shown in FIG. 3 (a), the ends of the optical fibers are matched to match the mode coherence, and the saturation of the femtosecond pulse generated in the mode lock can be maintained. A absorber (SA) 160 and an isolator 170 are provided.

In addition, in the Fabry-Parot type, as shown in FIG. 3 (b), semiconductor-based saturated absorber mirrors (SEMIconductor Saturable Absorber Mirrors, SESAM) 180 and mirrors 190 are respectively provided at both ends. To configure the resonance structure.

At this time, the position and combination of each component constituting the resonator 100 is not fixed, and may be configured by being modified in various forms depending on the application field.

Furthermore, an optical loss adjusting unit 130 is provided in the resonator 100 of the optical fiber femtosecond laser device 10 according to an embodiment of the present invention to control optical loss according to the wavelength.

Accordingly, in the resonator 100 of the optical fiber femtosecond laser apparatus 10 according to an embodiment of the present invention, the optical loss according to the wavelength in the resonator 100 is controlled using the optical loss adjusting unit 130. Thus, it is possible to effectively adjust the center wavelength of the laser generated by mode-locking.

More specifically, FIG. 4 is a diagram illustrating an operation of the optical fiber femtosecond laser device 10 according to an embodiment of the present invention.

That is, in the resonator 100 of the optical fiber femtosecond laser apparatus 10 according to an embodiment of the present invention, the gain due to the gain optical fiber 110 and other components and loss in optical fibers, etc., can be seen in FIG. 4. As described above, a gain curve 101 of the resonator 100 is formed.

At this time, it may be determined that the center wavelength of the laser generated by the difference between the possible gain-loss oscillation. Here, the loss means all kinds of losses present in the resonator 100, and when the steady state of gain and loss by the components constituting the resonator 100 is maintained, the center wavelength of the laser generated accordingly is determined. Lose.

In addition, since the resonator 100 achieves coherence in multiples of a specific wavelength, as can be seen in FIG. 4, eventually, the gain in the resonator 100 is coherent as a multiple of the specific wavelength and a wavelength region greater than a loss. The mode lock is possible in the number of modes in which the wavelength regions constituting the overlapping, and resonance is achieved, thereby generating the femtosecond laser.

Furthermore, in the optical fiber femtosecond laser apparatus 10 according to an embodiment of the present invention, the optical loss according to the wavelength in the resonator 100 is controlled by using the optical loss adjusting unit 130 to generate the laser. The center wavelength is adjusted.

That is, the optical loss adjusting unit 130 adjusts the optical loss according to the wavelength in the resonator 100, and as shown in FIG. 4, changes the gain curve 101 of the resonator 100 (FIG. (A) of 4, whereby it is possible to effectively adjust the center wavelength of the laser generated by the mode lock in the resonator 100.

As an embodiment of the present invention, the optical loss adjusting unit 130 may adjust the optical loss in the resonator 100 by using the bending loss of the optical fiber included in the resonator 100.

As a more specific embodiment, the optical loss adjusting unit 130 may adjust the optical loss in the resonator 100 by adjusting the curvature or the number of turns of the optical fiber included in the resonator 100.

Furthermore, in the optical fiber femtosecond laser apparatus 10 according to an embodiment of the present invention, the optical loss adjusting unit 130 uses the optical loss adjusting structure 131 to adjust the curvature or the number of turns of the optical fiber. Light loss in the resonator 100 can be adjusted.

On the other hand, Figure 5 shows an implementation of the optical loss control unit 130 in the optical fiber femtosecond laser device 10 according to an embodiment of the present invention.

First, as can be seen in FIG. 5 (a), the optical loss adjusting unit 130 wraps an optical fiber in a conical structure 131 with a curvature R, resulting in bending loss due to bending of the optical fiber. bending loss) to control the optical loss.

At this time, it is also possible to control the optical loss in the resonator 100 by adjusting the curvature R of the optical fiber or adjusting the number of turns.

In addition, as can be seen in FIG. 5 (b), the optical loss adjusting unit 130 winds an optical fiber with a curvature R on a structure 131 having a plurality of cylinders having different diameters, thereby bending the optical fiber due to bending. It is also possible to control the optical loss by using a loss (radiation loss or bending loss), it is also possible to adjust the optical loss in the resonator 100 by changing the curvature R of the optical fiber or by adjusting the number of turns.

In addition, as can be seen in FIG. 5 (c), the optical loss adjusting unit 130 may adjust the optical loss in the optical fiber by using structures 131 and 132 capable of bending the optical fiber with a predetermined curvature R. have.

Furthermore, in the present invention, the method of adjusting the optical loss in the resonator 100 by adjusting the curvature or the number of rotational turns of the optical fiber is not limited to those listed in FIG. 5, and the optical fiber in various structures in addition to the application fields It is possible to control the optical loss at.

In addition, Figure 6 shows a measurement showing the central wavelength shift by the optical loss control unit 130 in the optical fiber femtosecond laser device 10 according to an embodiment of the present invention.

More specifically, FIG. 6 shows measurement values when the center wavelength of the laser generated by reducing the curvature of the optical fiber by using the light loss adjusting unit 130 is adjusted from 1033 nm to 1030 nm ((B) of FIG. 6). have.

As can be seen in Figure 6, in the optical fiber femtosecond laser device 10 according to an embodiment of the present invention, the optical loss control unit 130 adjusts the optical loss in the resonator 100 using the bending loss of the optical fiber. By doing so, even if an error occurs in the center wavelength of the laser due to the characteristic variation in each component constituting the resonator 100, it can be easily adjusted.

Accordingly, in the optical fiber femtosecond laser device 10 according to an embodiment of the present invention, while the conventional optical fiber femtosecond laser device did not have a proper method to adjust the center wavelength, the resonator 100 includes the tune of the optical fiber. By controlling the light loss in the resonator 100, it is possible to adjust the center wavelength of the optical fiber femtosecond laser device 10 using the same.

More specifically, when a grating or grating mirror or a mirror is used in an existing optical fiber femtosecond laser device, a mirror loss is determined according to a design value to construct a resonator. As the balance with other components to be shifted, it was difficult to move to the central wavelength to be adjusted. In the optical fiber femtosecond laser device 10 according to an embodiment of the present invention, the curvature of the optical fiber was simply changed to change the wavelength. The optical loss can be adjusted, and thus, it is possible to adjust the center wavelength of the laser generated even after the resonator 100 is manufactured.

Accordingly, according to the present invention, even if the optical fiber femtosecond laser device 10 is prepared by preparing a component constituting the resonator 100 in accordance with the center wavelength of the laser targeted at the time of design, the mode lock in the resonator 100 When this occurs, each optical component (gain optical fiber 110, pumping light source 120, wavelength division multiplexer 140, output coupler 150, saturated absorber (SA) 160, semiconductor-based saturated absorber mirror (SESAM) (180), etc., even if the center wavelength of the generated laser deviates from the design value, it is possible to adjust the center wavelength of the laser simply by adjusting the curvature of the optical fiber.

In particular, in the optical fiber femtosecond laser device 10 according to an embodiment of the present invention, a hybrid type optical fiber femtosecond laser device 10 in which a solid amplification stage for amplifying the laser generated by the resonator 100 is combined is used. When implemented, accurate tuning of the center wavelength is possible, so that amplification stage design and fabrication can be made more effectively.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention, but to explain them, and are not limited to these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present invention.

10: fiber optic femtosecond laser device
100: resonator
110: gain optical fiber
120: pumping light source
130: light loss control unit
131, 132: light loss control structure
140: wavelength division multiplexer
150: output coupler
160: saturated absorber
170: isolator
180: semiconductor-based saturated absorber mirror
190: mirror

Claims (7)

In the optical fiber femtosecond laser device having a resonator to generate a laser,
A gain fiber for amplifying the laser at an amplification ratio according to the wavelength;
A pumping light source that pumps the gain optical fiber so that it can be driven; And
The optical loss control unit for adjusting the optical loss according to the wavelength; having a resonator comprising a,
Optical fiber femtosecond laser device, characterized in that by adjusting the optical loss according to the wavelength in the resonator by using the optical loss adjusting unit, the center wavelength of the laser generated by mode-locking (mode-locking). According to claim 1,
The light loss control unit,
Optical fiber femtosecond laser device, characterized in that to control the optical loss in the resonator by using the bending loss of the optical fiber included in the resonator. According to claim 2,
The light loss control unit,
Optical fiber femtosecond laser device, characterized in that to control the optical loss in the resonator by adjusting the curvature or the number of turns of the optical fiber included in the resonator. According to claim 3,
The light loss control unit,
Optical fiber femtosecond laser device, characterized in that for controlling the optical loss in the resonator by using an optical loss control structure that can adjust the curvature or the number of turns of the optical fiber. According to claim 1,
The resonator,
An optical fiber femtosecond laser device, characterized in that it is a ring type resonator including a saturable absorber. According to claim 1,
The resonator,
Fiber-based femtosecond laser device, characterized in that the Fabry-Parot type (Fabry-Parot type) resonator including a semiconductor-based saturable absorber mirror (semiconductor saturable absorber mirror). According to claim 1,
Further comprising a solid-state amplification stage for amplifying the laser generated by the resonator,
The optical loss adjusting unit is a fiber femtosecond laser device, characterized in that to adjust the center wavelength of the resonator to match the solid-state amplification stage and the center wavelength.

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