Ultrashort pulse-width compression device based on spectral broadening, and femtosecond fiber laser system including same

Abstract

According to the present disclosure, a first mirror, a second mirror, a third mirror, and a fourth mirror are arranged to face each other with a nonlinear crystal interposed therebetween, and the first mirror, the second mirror, the third mirror, and the fourth mirror respectively include a plurality of first points, a plurality of second points, a plurality of third points, and a plurality of fourth points, so as to reflect multiple laser beams between the mirrors in a predetermined sequence, wherein the second mirror may include a second hole through which the laser beam that is finally reflected from the first mirror is transmitted to the outside.

Description

Ultrashort pulse width compression device based on spectrum broadening, femtosecond fiber laser system including the same

[0001] The present disclosure relates to a laser system. More specifically, the present disclosure relates to an ultrashort pulse width compression device for spectrum expansion and a femtosecond fiber laser system including the same.

[0002] Generally, femtosecond laser light has been used in industrial settings to reduce cutting defects in semiconductor wafers and secondary battery electrodes.

[0003] Here, the femtosecond laser light was modulated by a pulse control signal not only for repetition rate control but also by laser light formed from a pulse train of the femtosecond laser.

[0004] At this time, laser light could be generated by a femtosecond fiber laser system.

[0005] However, conventional femtosecond fiber laser systems had limitations in increasing beam intensity by adjusting the magnification ratio of the laser light spectrum and increasing the focusing intensity.

[0006] Therefore, recently, there is a demand for the development of improved technology capable of increasing beam intensity by adjusting the magnification ratio of the laser light spectrum and increasing the focusing intensity.

[0007] The purpose of the embodiment according to the present disclosure is to provide a method for increasing beam intensity by adjusting the magnification ratio of the spectrum of laser light and increasing the focusing intensity.

[0008] The problems that this disclosure aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0009] An ultrashort pulse width compression device according to spectrum expansion according to one aspect of the present disclosure for achieving the technical problem described above comprises: a first mirror including a first hole that transmits incident laser light; a second mirror that reflects laser light incident through the first hole; a third mirror that reflects laser light incident through the second mirror; and a fourth mirror that reflects laser light incident through the third mirror. The apparatus includes a nonlinear crystal that expands the spectrum of laser light traveling back and forth through the first mirror, the second mirror, the third mirror, and the fourth mirror, wherein the first mirror, the second mirror, the third mirror, and the fourth mirror are arranged facing each other with the nonlinear crystal in between, and the first mirror, the second mirror, the third mirror, and the fourth mirror each include a plurality of first points, a plurality of second points, a plurality of third points, and a plurality of fourth points for reflection of a plurality of laser light between them in a predetermined order, and the second mirror may include a second hole that transmits the laser light finally reflected through the first mirror to the outside.

[0010] Additionally, the plurality of first points are formed at three equal intervals to reflect a plurality of laser lights incident through the fourth mirror to the second mirror, the plurality of second points are formed at three equal intervals to reflect a plurality of laser lights incident through the first mirror to the third mirror, the plurality of third points are formed at three equal intervals to reflect a plurality of laser lights incident through the second mirror to the fourth mirror, and the plurality of fourth points are formed at three equal intervals to reflect a plurality of laser lights incident through the third mirror to the first mirror.

[0011] An ultrashort pulse width compression device for spectrum expansion according to another aspect of the present disclosure comprises: a first mirror having a first hole that transmits incident laser light; a second mirror that reflects laser light incident through the first hole; a third mirror that reflects laser light incident through the second mirror; and a fourth mirror that reflects laser light incident through the third mirror. The apparatus includes a nonlinear crystal that expands the spectrum of laser light traveling back and forth through the first mirror, the second mirror, the third mirror, and the fourth mirror, wherein the first mirror, the second mirror, the third mirror, and the fourth mirror are arranged facing each other with the nonlinear crystal in between, and the first mirror, the second mirror, the third mirror, and the fourth mirror each include a plurality of first points, a plurality of second points, a plurality of third points, and a plurality of fourth points for reflection of a plurality of laser light between them in a predetermined order, and the fourth mirror may include a second hole that transmits the laser light finally reflected through the third mirror to the outside.

[0012] Additionally, the plurality of first points are formed at equal intervals of two to reflect a plurality of laser lights incident through the fourth mirror to the second mirror, the plurality of second points are formed at equal intervals of three to reflect a plurality of laser lights incident through the first mirror to the third mirror, the plurality of third points are formed at equal intervals of three to reflect a plurality of laser lights incident through the second mirror to the fourth mirror, and the plurality of fourth points are formed at equal intervals of two to reflect a plurality of laser lights incident through the third mirror to the first mirror.

[0013] In addition, the laser light may be characterized by forming a round-trip path by alternating one by one in sequence through the plurality of first points, the plurality of second points, the plurality of third points, and the plurality of fourth points.

[0014] Additionally, it may further include a first lens that is aligned with the first mirror and the fourth mirror and focuses the laser light; and a second lens that is aligned with the second mirror and the third mirror and focuses the laser light.

[0015] In addition, the focusing intensity in the nonlinear crystal can be determined according to the focal length of the lens.

[0016] In addition, the above nonlinear crystal may be characterized by being provided in multiple numbers between the first lens and the second lens to adjust the magnification ratio of the spectrum.

[0017] In addition, the above nonlinear crystal may include any one of SF10, SF11, Fused silica, BK7, CaF2, Sapphire glass, and Birefringent crystal, which belong to the glass series.

[0018] In addition, a femtosecond fiber laser system including an ultrashort pulse width compression device according to spectrum expansion according to another aspect of the present disclosure may be provided.

[0019] According to the above-described means for solving the problem of the present disclosure, by adjusting the magnification ratio of the spectrum of laser light and increasing the focusing intensity, an effect is provided to increase the beam intensity.

[0020] FIG. 1 illustrates a femtosecond fiber laser system according to the present disclosure.

[0021] Figure 2 illustrates a detailed configuration of the femtosecond fiber laser system of Figure 1 as an example.

[0022] FIG. 3 shows the wavelength of the pulsed laser light of FIG. 2, the wavelength of the first continuous wave laser light, and the wavelength of the second continuous wave laser light.

[0023] Figure 4 illustrates the configuration of the ultrashort pulse width compression device of Figure 2 as an example.

[0024] Figure 5 illustrates the configuration of the ultrashort pulse width compression device of Figure 2 as another example.

[0025] Throughout this disclosure, the same reference numerals denote the same components. This disclosure does not describe all elements of the embodiments, and general content in the art to which this disclosure pertains or content that overlaps between embodiments is omitted. The terms 'part, module, component, block' as used in the specification may be implemented in software or hardware, and depending on the embodiments, a plurality of 'parts, modules, components, blocks' may be implemented as a single component, or a single 'part, module, component, block' may include a plurality of components.

[0026] Throughout the specification, when a part is described as being "connected" to another part, this includes not only cases where they are directly connected but also cases where they are indirectly connected, and indirect connections include connections made via a wireless communication network.

[0027] Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0028] Throughout the specification, when it is stated that a component is located "on" another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components.

[0029] Terms such as "first," "second," etc., are used to distinguish one component from another, and the components are not limited by the aforementioned terms.

[0030] Singular expressions include plural expressions unless there is an obvious exception in the context.

[0031] In each step, identification codes are used for convenience of explanation and do not describe the order of the steps; the steps may be performed differently from the specified order unless a specific order is clearly indicated in the context.

[0032] The operating principles and embodiments of the present disclosure will be described below with reference to the attached drawings.

[0033] FIG. 1 illustrates a femtosecond fiber laser system according to the present disclosure. FIG. 2 illustrates a detailed configuration of the femtosecond fiber laser system of FIG. 1 as an example.

[0034] FIG. 3 shows the wavelength of the pulsed laser light of FIG. 2, the wavelength of the first continuous wave laser light, and the wavelength of the second continuous wave laser light.

[0035] Referring to FIGS. 1 to 3, a femtosecond fiber laser system (100) according to the present disclosure may include a femtosecond light source (10), a preamplifier (20), a pulse picker (30), a first continuous wave light source (40), a main amplifier (50), an ultrashort pulse width compression device (60), a polarizing plate (65), a control module (70), and a second continuous wave light source (80).

[0036] The femtosecond light source (10) can generate femtosecond laser light (12). Here, the femtosecond laser light (12) can have a frequency of about 10 MHz to about 1000 MHz.

[0037] A preamplifier (20) can be connected to a femtosecond light source (10). Here, the preamplifier (20) can amplify femtosecond laser light (12).

[0038] The pulse speaker (30) can be connected to a preamplifier (20). Here, the pulse speaker (30) can generate pulsed laser light (32) by modulating femtosecond laser light (12). Here, pulsed laser light (32) refers to femtosecond laser light having any pulse train.

[0039] The first continuous wave light source (40) may be connected to a pulse speaker (30) and a main amplifier (50) by an optical fiber (11). Here, the first continuous wave light source (40) may provide a first continuous wave laser light (42) to the main amplifier (50). For example, the first continuous wave light source (40) may include a laser diode, but the present disclosure is not limited thereto.

[0040] Here, the first continuous wave light source (40) may include a first pump light source (41) and a first ring resonator (43). Here, the first pump light source (41) may generate a first pump light (45). For example, the first pump light source (41) may include a laser diode. Additionally, the first ring resonator (43) may be provided between the first pump light source (41) and a coupler (44). Here, the first ring resonator (43) may have a first radius (R1). Such a first ring resonator (43) may resonate the first pump light (45) to generate a first continuous wave laser light (42).

[0041] The second continuous wave light source (80) can be connected to the coupler (44). Here, the second continuous wave light source (80) can generate a second continuous wave laser light (82) that is longer than the wavelength of the first continuous wave laser light (42) of the first continuous wave light source (40). Here, the second continuous wave light source (80) may include a second pump source (81) and a second ring resonator (83). Here, the second pump light source (81) can generate a second pump light (85). For example, the second pump light source (81) may include a laser diode. Additionally, the second ring resonator (83) may be provided between the second pump light source (81) and the coupler (44). Here, the second ring resonator (83) may have a second radius (R2) that is larger than the first radius (R1). This second ring resonator (83) can resonate the second pump light source (85) to generate a second continuous wave laser light (82).

[0042] The first continuous wave laser light (42) and the second continuous wave laser light (82) can prevent damage to the main amplifier (50) during the idle period of the pulsed laser light (32). In this case, the first continuous wave laser light (42) and the second continuous wave laser light (82) can prevent damage to the main amplifier (50) because, at the moment when the pulsed laser light (32) is turned off, the first pump light source (40) and the second pump light source (80) are turned on, and the first continuous wave laser light (42) and the second continuous wave laser light (82) are oscillated and input to the main amplifier (50).

[0043] Additionally, the first continuous wave laser light (42) and the second continuous wave laser light (82) may have the same polarization. Here, the pulsed laser light (32) may have a polarization perpendicular to the first continuous wave laser light (42) and the second continuous wave laser light (82).

[0044] As illustrated in FIG. 3, the wavelength peak of the first continuous wave laser light (42) may overlap with one side of the wavelength band of the pulsed laser light (32), and the wavelength peak of the second continuous wave laser light (82) may overlap with the other side of the wavelength band of the pulsed laser light (32). For example, the wavelength peak of the first continuous wave laser light (42) may overlap with the short wavelength of the pulsed laser light (32), and the wavelength peak of the second continuous wave laser light (82) may overlap with the long wavelength of the pulsed laser light (32). Additionally, the wavelength peak of the first continuous wave laser light (42) may overlap with or touch either end of the wavelength band of the pulsed laser light (32).

[0045] A polarizing plate (65) is provided between the main amplifier (50) and the ultrashort pulse width compression device (60) and can eliminate the first continuous wave laser light (42) and the second continuous wave laser light (82). In one example, a first continuous wave light source (40) provided perpendicular to the polarization axis of the pulsed laser light (32) generates the first continuous wave laser light (42) polarized in one direction, and the polarizing plate (65) can eliminate the first continuous wave laser light (42). In another example, a second continuous wave light source (80) provided perpendicular to the polarization axis of the pulsed laser light (32) generates the second continuous wave laser light (82) polarized in one direction, and the polarizing plate (65) can eliminate the second continuous wave laser light (82).

[0046] Here, the polarizing plate (65) may have a polarizer perpendicular to the polarization direction of the first continuous wave laser light (42) and the second continuous wave laser light (82). For example, if the first continuous wave laser light (42) and the second continuous wave laser light (82) are polarized in a horizontal direction, the polarizing plate (65) may have a vertical polarizer. For another example, if the first continuous wave laser light (42) and the second continuous wave laser light (82) are polarized in a vertical direction, the polarizing plate (65) may have a horizontal polarizer. For yet another example, if the first continuous wave laser light (42) and the second continuous wave laser light (82) are right-circle polarized, the polarizing plate (65) may have a left-circle polarizer. For yet another example, if the first continuous wave laser light (42) and the second continuous wave laser light (82) are left-circle polarized, the polarizing plate (65) may have a right-circle polarizer.

[0047] The control module (70) may include a memory that stores data for an algorithm or a program that reproduces the algorithm for controlling the operation of components within the system, and at least one processor that performs the aforementioned operation using the data stored in the memory. Here, the memory and the processor may each be provided as separate chips. Additionally, the memory and the processor may be provided as a single chip.

[0048] The memory can store data supporting various functions of the system and programs for the operation of the control module, as well as input or output data. Additionally, the memory can store multiple application programs (or applications) running on the system, data for the operation of the system, and instructions. At least some of these application programs may be downloaded from an external server via wireless communication.

[0049] Here, the memory may include at least one storage medium among Flash Memory type, Hard Disk type, Solid State Disk (SSD) type, Silicon Disk Drive (SSD) type, Multimedia Card Micro type, card type memory (e.g., SD or XD memory, etc.), Random Access Memory (RAM), Static Random Access Memory (SRAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), Programmable Read Only Memory (PROM), magnetic memory, magnetic disk, and optical disk. Additionally, the memory may be a database that is separated from the system and connected via wired or wireless connection.

[0050] Memory can store data related to the femtosecond fiber laser. The processor can control operations related to the femtosecond fiber laser.

[0051] The control module (70) can control the pre-amplifier (20), the pulse speaker (30), and the main amplifier (50). Additionally, the control module (70) can control the pre-amplifier (20) and the pulse speaker (30) to control the generation of femtosecond laser light (12) and pulse laser light (32). Here, when femtosecond laser light (12) and pulse laser light (32) are not generated, the first continuous wave light source (40) can provide the first continuous wave laser light (42) to the main amplifier (50) to prevent burning and damage to the main amplifier (50).

[0052] The femtosecond fiber laser system (100) according to the present disclosure may further include a pulse width expander (15), an isolator (16), a picker control module (34), and a coupler (44).

[0053] A pulse width expander (15) may be provided between the femtosecond light source (10) and the preamplifier (20). Such a pulse width expander (15) can expand the pulse width of the femtosecond laser light (12).

[0054] For example, the pulse width expander (15) may include a circulator (13) and a chirped fiber Bragg grating (14). Here, the circulator (13) may be provided between the femtosecond light source (10) and the preamplifier (20). In this case, the circulator (13) may include at least one port. Additionally, the chirped fiber Bragg grating (14) may be connected to the port of the circulator (13). Such a chirped fiber Bragg grating (14) can expand the pulse width of the femtosecond laser light (12).

[0055] The isolator (16) may be connected by an optical fiber (11) between the preamplifier (20) and the pulse picker (30). Such an isolator (16) can protect the preamplifier (20) and the femtosecond light source (10) by blocking the return of the femtosecond laser light (12). Here, the optical fiber (11) located between the preamplifier (20) and the isolator (16) may include a gain medium optical fiber, such as a Yb-doped, Nd-doped, or Er-doped Polarization Maintaining Fiber. For example, the preamplifier (20) may include a laser diode.

[0056] A picker control module (34) can be connected to a pulse picker (30). Such a picker control module (34) can control the pulse repetition rate and the pulse train. Here, an optical fiber coupling device (18) may be provided in the optical fiber (11) adjacent to the picker control unit (34).

[0057] Here, the picker control module (34) provides a pulse control signal to the pulse picker (30), and the pulse picker (30) can generate a pulse laser light (32) by modulating the femtosecond laser light (12) based on the pulse control signal. Here, the pulse control signal and the pulse laser light (32) may have a modulated frequency between about 0 Hz and about 1 GHz.

[0058] A coupler (44) may be provided between a pulse speaker (30) and a main amplifier (50). Additionally, a coupler (44) may be provided between a first continuous wave light source (40) and a main amplifier (50). Here, the coupler (44) may connect the pulse speaker (30) and the first continuous wave light source (40) to the main amplifier (50). For example, the coupler (44) may include a Y-branch coupler.

[0059] Additionally, the coupler (44) can couple optical fibers (11) connected to the first continuous wave light source (40) and the pulse speaker (30). Here, the optical fibers (11) may include single-mode optical fibers. Additionally, the optical fibers (11) may include multi-mode optical fibers, and the present disclosure is not limited thereto.

[0060] A main amplifier (50) may be provided between a pulse speaker (30) and an ultrashort pulse width compression device (60). Here, the main amplifier (50) may be provided between a first continuous wave light source (40) and an ultrashort pulse width compression device (60). Here, the main amplifier (50) may amplify pulsed laser light (32). Additionally, the main amplifier (50) may amplify the first continuous wave laser light (42). Additionally, the main amplifier (50) may amplify the second continuous wave laser light (82). For example, the main amplifier (50) may include a plurality of laser diodes. Here, the main amplifier (50) may include a first main amplifier (52), a second main amplifier (54), and a third main amplifier (56).

[0061] The first main amplifier (52) may be connected to the coupler (44) and the second main amplifier (54) via an optical fiber (11). Here, the first main amplifier (52) may include a laser diode and a gain medium optical fiber. Here, the gain medium optical fiber of the first main amplifier (52) may include a Yb-doped, Nd-doped, or Er-doped Polarization-Maintaining Fiber. Additionally, the first filter (51) may be connected to the first main amplifier (52) and the second main amplifier (54) via an optical fiber (11). Here, the first filter (51) may remove noise from the pulsed laser light (32) amplified by the first main amplifier (52). Additionally, an isolator (16) may be provided between the first filter (51) and the gain medium optical fiber. Here, the isolator (16) can increase the amplification efficiency of the first main amplifier (52) by blocking reverse flow for the pulsed laser light (32) and the first continuous wave laser light (42).

[0062] The second main amplifier (54) may be connected by an optical fiber (11) between the first main amplifier (52) and the third main amplifier (56). Here, the second main amplifier (54) may include a laser diode and a gain medium optical fiber. Here, the gain medium optical fiber of the second main amplifier (54) may include a Yb-doped, Nd-doped, or Er-doped Polarization-Maintaining Fiber. Additionally, the second filter (53) may be connected by an optical fiber (11) between the second main amplifier (54) and the third main amplifiers (56). Here, the second filter (53) may remove noise from the pulsed laser light (32) amplified by the second main amplifier (54). Additionally, the first cladding mode stripper (55) may be provided between the gain medium optical fiber of the second main amplifier (54) and the second filter (53). Here, the first cladding mode stripper (55) can remove residual pumps within the cladding of the gain medium optical fiber. Additionally, an isolator (16) can be provided between the first cladding mode stripper (55) and the second filter (53). Such an isolator (16) can increase the amplification efficiency of the second main amplifier (54) by blocking reverse flow for the pulsed laser light (32) and the first continuous wave laser light (42).

[0063] The third main amplifier (56) may be connected to the second main amplifier (54) and the ultrashort pulse width compression device (60) via an optical fiber (11). Here, the third main amplifier (56) may include a laser diode and a gain medium optical fiber. At this time, the gain medium optical fiber provided between the third main amplifier (56) and the lens (58) may include a Yb-doped, Nd-doped, or Er-doped Polarization-Maintaining Fiber. Additionally, an end cap (59) may be provided at the end of the gain medium optical fiber. Such an end cap (59) can prevent the end of the optical fiber (11) from being damaged by the amplified pulsed laser light (32) and the first continuous wave laser light (42). Additionally, the lens (58) may be provided between the third main amplifier (56) and the ultrashort pulse width compression device (60). Such a lens (58) can collimate the pulsed laser light (32) and the first continuous wave laser light (42) to the pulse width compression device (60).

[0064] The ultrashort pulse width compression device (60) can be connected to the main amplifier (50). Here, the ultrashort pulse width compression device (60) can compress the pulse width of the pulse laser light (32) and block or remove the first continuous wave laser light (42) and the second continuous wave laser light (82).

[0065] Figure 4 illustrates the configuration of the ultrashort pulse width compression device of Figure 2 as an example.

[0066] Referring to FIG. 4, the ultrashort pulse width compression device (60) may include a first mirror (61), a second mirror (62), a third mirror (63), a fourth mirror (64), a nonlinear crystal (65), and a fifth mirror (66).

[0067] The first mirror (61) may include a first hole (h1) that transmits incident laser light. Here, a plurality of first points (P11 to P13) may be formed at three equal intervals to reflect a plurality of laser lights incident through the fourth mirror (64) to the second mirror (62). For example, the first mirror (61) may be a prism reflective mirror. Not limited thereto, the plurality of first points (P11 to P13) may be formed at four or more equal intervals.

[0068] The second mirror (62) can reflect laser light incident through the first hole (h1). Here, a plurality of second points (P21 to P23) may be formed at three equal intervals to reflect a plurality of laser lights incident through the first mirror (61) to the third mirror (63). Not limited thereto, the plurality of second points (P21 to P23) may be formed at four or more equal intervals. Here, the second mirror (62) may include a second hole (h2) that transmits the laser light finally reflected through the first mirror (61) to the outside. Here, the fifth mirror (66) may output the laser light finally transmitted to the outside. For example, the second mirror (62) may be a prism reflective mirror. Also, the fifth mirror (66) may be a planar reflective mirror.

[0069] The third mirror (63) can reflect laser light incident through the second mirror (62). Here, a plurality of third points (P31 to P33) may be formed at three equal intervals to reflect a plurality of laser lights incident through the second mirror (62) to the fourth mirror (64). For example, the third mirror (63) may be a prism reflector mirror. Not limited thereto, the plurality of third points (P13 to P33) may be formed at four or more equal intervals.

[0070] The fourth mirror (64) can reflect laser light incident through the third mirror (63). Here, a plurality of fourth points (P41 to P43) may be formed at three equal intervals to reflect a plurality of laser lights incident through the third mirror (63) to the first mirror (61). For example, the fourth mirror (64) may be a prism reflective mirror. Not limited thereto, the plurality of fourth points (P41 to P43) may be formed at four or more equal intervals.

[0071] Here, the laser light (69) can form a round-trip path by alternating one by one in a predetermined order through a plurality of first points (P11 to P13), a plurality of second points (P21 to P23), a plurality of third points (P31 to P33), and a plurality of fourth points (P41 to P43), each formed at three equal intervals. For example, the laser light (69) may be an ultrashort laser light.

[0072] The first lens (67) is positioned in alignment with the first mirror (61) and the fourth mirror (64) and can focus the laser light (69). Additionally, the second lens (68) is positioned in alignment with the second mirror (62) and the third mirror (63) and can focus the laser light (69).

[0073] The first mirror (61), the second mirror (62), the third mirror (63), and the fourth mirror (64) may be arranged facing each other with a nonlinear crystal (65) in between. Here, the nonlinear crystal (65) can magnify the spectrum of the laser light (69) traveling back and forth through the first mirror (61), the second mirror (62), the third mirror (63), and the fourth mirror (64). Additionally, the nonlinear crystal (65) can move horizontally between the first lens (67) and the second lens (68) to adjust the amount of spectrum magnification. Here, the nonlinear crystal (65) may include any one of SF10, SF11, Fused silica, BK7, CaF2, Sapphire glass, and Birefringent crystal, which correspond to the glass series. Here, when the nonlinear crystal (65) is made of N-SF11 material, the reference output must exceed approximately Pc = 0.7 MW @ 1030 nm to expand the spectrum of the laser light (69) (this is called Self-Phase Modulation, SPM phenomenon). Here, the threshold value of the nonlinear crystal (65) may vary depending on the refractive index of the nonlinear material.

[0074] The ultrashort pulse width compression device (60) according to the present disclosure can focus a laser light (69) incident through a first hole (h1) through a first lens (67) and a second lens (68), and reflect the focused laser light (69) in the direction of a third mirror (63) through P21 among a plurality of second points (P21 to P23) of a second mirror (62).

[0075] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the third mirror (63) in the direction of the fourth mirror (64) through P31 among a plurality of third points (P31 to P33) of the third mirror (63), and reflect laser light (69) intended to be incident on the fourth mirror (64) in the direction of the first mirror (61) through P41 among a plurality of fourth points (P41 to P43) of the fourth mirror (64).

[0076] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the first mirror (61) in the direction of the second mirror (62) through P11 among a plurality of first points (P11 to P13) of the first mirror (61), and reflect laser light (69) intended to be incident on the second mirror (62) in the direction of the third mirror (63) through P22 among a plurality of second points (P21 to P23) of the second mirror (62).

[0077] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the third mirror (63) in the direction of the fourth mirror (64) through P32 among a plurality of third points (P31 to P33) of the third mirror (63), and reflect laser light (69) intended to be incident on the fourth mirror (64) in the direction of the first mirror (61) through P42 among a plurality of fourth points (P41 to P43) of the fourth mirror (64).

[0078] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the first mirror (61) in the direction of the second mirror (62) through P12 among a plurality of first points (P11 to P13) of the first mirror (61), and reflect laser light (69) intended to be incident on the second mirror (62) in the direction of the third mirror (63) through P23 among a plurality of second points (P21 to P23) of the second mirror (62).

[0079] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the third mirror (63) in the direction of the fourth mirror (64) through P33 among a plurality of third points (P31 to P33) of the third mirror (63), and reflect laser light (69) intended to be incident on the fourth mirror (64) in the direction of the first mirror (61) through P43 among a plurality of fourth points (P41 to P43) of the fourth mirror (64).

[0080] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the first mirror (61) in the direction of the second mirror (62) through P13 among a plurality of first points (P11 to P13) of the first mirror (61).

[0081] Afterwards, the ultrashort pulse width compression device (60) according to the present disclosure transmits the final laser light (69) intended to be incident on the second mirror (62) through the second hole (h2) and reflects it in the direction of the fifth mirror (66), and can output the final laser light (69) intended to be incident on the fifth mirror (66) by reflecting it outward.

[0082] Here, a plurality of nonlinear crystals (65) may be provided between the first lens (67) and the second lens (68) to adjust the magnification ratio of the spectrum. For example, the nonlinear crystals (65) may include a first nonlinear crystal (65a), a second nonlinear crystal (65b), and a third nonlinear crystal (65c).

[0083] Additionally, the focusing strength in the nonlinear crystal (65) can be determined according to the focal lengths of the first lens (67) and the second lens (68). Here, the focusing strength can be increased as the number of round-trip paths formed by the laser light (69) alternately in a predetermined order through a plurality of first points (P11 to P13), a plurality of second points (P21 to P23), a plurality of third points (P31 to P33), and a plurality of fourth points (P41 to P43), each formed at three equal intervals. Accordingly, the present disclosure can increase the beam strength by increasing the focusing strength in the nonlinear crystal (65). That is, the beam strength (I1, I2, I3) of the laser using the focusing strength of the nonlinear crystal (65) of the present disclosure can be stronger than the beam strength (I1) of the laser before it is incident on the first hole (h1).

[0084] Figure 5 illustrates the configuration of the ultrashort pulse width compression device of Figure 2 as another example.

[0085] Referring to FIG. 4, the ultrashort pulse width compression device (60) may include a first mirror (61), a second mirror (62), a third mirror (63), a fourth mirror (64), a nonlinear crystal (65), and a fifth mirror (66).

[0086] The first mirror (61) may include a first hole (h1) that transmits incident laser light. Here, a plurality of first points (P11 and P12) may be formed at two equal intervals to reflect a plurality of laser lights incident through the fourth mirror (64) to the second mirror (62). For example, the first mirror (61) may be a prism reflective mirror. Not limited thereto, the plurality of first points (P11 and P12) may be formed at three or more equal intervals.

[0087] The second mirror (62) can reflect laser light incident through the first hole (h1). Here, a plurality of second points (P21 to P23) may be formed at three equal intervals to reflect a plurality of laser lights incident through the first mirror (61) to the third mirror (63). For example, the second mirror (62) may be a prism reflective mirror. Not limited thereto, the plurality of second points (P21 to P23) may be formed at four or more equal intervals.

[0088] The third mirror (63) can reflect laser light incident through the second mirror (62). Here, a plurality of third points (P31 to P33) may be formed at three equal intervals to reflect a plurality of laser lights incident through the second mirror (62) to the fourth mirror (64). For example, the third mirror (63) may be a prism reflector mirror. Not limited thereto, the plurality of third points (P31 to P33) may be formed at four or more equal intervals.

[0089] The fourth mirror (64) can reflect laser light incident through the third mirror (63). Here, a plurality of fourth points (P41 and P42) may be formed at two equal intervals to reflect a plurality of laser lights incident through the third mirror (63) to the first mirror (61). Not limited thereto, a plurality of fourth points (P41 and P42) may be formed at three or more equal intervals. Here, the fourth mirror (64) may include a second hole (h2) that transmits the laser light finally reflected through the third mirror (63) to the outside. Here, the fifth mirror (66) may output the laser light finally transmitted to the outside. For example, the fourth mirror (64) may be a prism reflective mirror. Also, the fifth mirror (66) may be a planar reflective mirror.

[0090] Here, the laser light (69) can form a round-trip path one by one in a predetermined order through a plurality of first points (P11 and P12) formed at two equal intervals, a plurality of second points (P21 to P23) formed at three equal intervals, a plurality of third points (P31 to P33) formed at three equal intervals, and a plurality of fourth points (P41 and P42) formed at two equal intervals. For example, the laser light (69) may be an ultrashort laser light.

[0091] The first lens (67) is positioned in alignment with the first mirror (61) and the fourth mirror (64) and can focus the laser light (69). Additionally, the second lens (68) is positioned in alignment with the second mirror (62) and the third mirror (63) and can focus the laser light (69).

[0092] The first mirror (61), the second mirror (62), the third mirror (63), and the fourth mirror (64) may be arranged facing each other with a nonlinear crystal (65) in between. Here, the nonlinear crystal (65) can magnify the spectrum of the laser light (69) traveling back and forth through the first mirror (61), the second mirror (62), the third mirror (63), and the fourth mirror (64). Additionally, the nonlinear crystal (65) can move horizontally between the first lens (67) and the second lens (68) to adjust the amount of spectrum magnification. Here, the nonlinear crystal (65) may include any one of SF10, SF11, Fused silica, BK7, CaF2, Sapphire glass, and Birefringent crystal, which correspond to the glass series. Here, when the nonlinear crystal (65) is made of N-SF11 material, the reference output must exceed approximately Pc = 0.7 MW @ 1030 nm to expand the spectrum of the laser light (69) (this is called Self-Phase Modulation, SPM phenomenon). Here, the threshold value of the nonlinear crystal (65) may vary depending on the refractive index of the nonlinear material.

[0093] The ultrashort pulse width compression device (60) according to the present disclosure can focus a laser light (69) incident through a first hole (h1) through a first lens (67) and a second lens (68), and reflect the focused laser light (69) in the direction of a third mirror (63) through P21 among a plurality of second points (P21 to P23) of a second mirror (62).

[0094] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the third mirror (63) in the direction of the fourth mirror (64) through P31 among a plurality of third points (P31 to P33) of the third mirror (63), and reflect laser light (69) intended to be incident on the fourth mirror (64) in the direction of the first mirror (61) through P41 among a plurality of fourth points (P41 and P42) of the fourth mirror (64).

[0095] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the first mirror (61) in the direction of the second mirror (62) through P11 among a plurality of first points (P11 and P12) of the first mirror (61), and reflect laser light (69) intended to be incident on the second mirror (62) in the direction of the third mirror (63) through P22 among a plurality of second points (P21 to P23) of the second mirror (62).

[0096] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the third mirror (63) in the direction of the fourth mirror (64) through P32 among a plurality of third points (P31 to P33) of the third mirror (63), and reflect laser light (69) intended to be incident on the fourth mirror (64) in the direction of the first mirror (61) through P42 among a plurality of fourth points (P41 and P42) of the fourth mirror (64).

[0097] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the first mirror (61) in the direction of the second mirror (62) through P12 among a plurality of first points (P11 and P12) of the first mirror (61), and reflect laser light (69) intended to be incident on the second mirror (62) in the direction of the third mirror (63) through P23 among a plurality of second points (P21 to P23) of the second mirror (62).

[0098] Afterward, the ultrashort pulse width compression device (60) according to the present disclosure can reflect laser light (69) intended to be incident on the third mirror (63) in the direction of the fourth mirror (64) through P33 among a plurality of third points (P31 to P33) of the third mirror (63).

[0099] Afterwards, the ultrashort pulse width compression device (60) according to the present disclosure transmits the final laser light (69) intended to be incident on the fourth mirror (64) through the second hole (h2) and reflects it in the direction of the fifth mirror (66), and can output the final laser light (69) intended to be incident on the fifth mirror (66) by reflecting it outward.

[0100] Here, a plurality of nonlinear crystals (65) may be provided between the first lens (67) and the second lens (68) to adjust the magnification ratio of the spectrum. For example, the nonlinear crystals (65) may include a first nonlinear crystal (65a), a second nonlinear crystal (65b), and a third nonlinear crystal (65c).

[0101] Additionally, the focusing strength in the nonlinear crystal (65) can be determined according to the focal lengths of the first lens (67) and the second lens (68). Here, the focusing strength can be increased as the number of round-trip paths formed by the laser light (69) alternately one by one in a predetermined order through a plurality of first points (P11 and P12) formed at two equal intervals, a plurality of second points (P21 to P23) formed at three equal intervals, a plurality of third points (P31 to P33) formed at three equal intervals, and a plurality of fourth points (P41 and P42) formed at two equal intervals increases. Accordingly, the present disclosure can increase the beam strength by increasing the focusing strength in the nonlinear crystal (65). That is, the beam intensity (I1, I2, I3) of the laser using the focusing intensity of the nonlinear crystal (65) of the present disclosure can be stronger than the beam intensity (I1) of the laser before it is incident on the first hole (h1).

[0102] Meanwhile, at least one of the first mirror (61), the second mirror (62), the third mirror (63), and the fourth mirror (64) is coated using a Negative Group Delay Dispersion method, so that the magnification ratio of the spectrum can be adjusted while compensating for the Positive GDD value generated in the nonlinear material. This Negative Group Delay Dispersion coating method can improve the effect of Self-Phase Modulation by increasing the focusing intensity.

[0103] As described above, the disclosed embodiments have been explained with reference to the attached drawings. Those skilled in the art will understand that the present disclosure may be practiced in forms different from the disclosed embodiments without changing the technical spirit or essential features of the present disclosure. The disclosed embodiments are illustrative and should not be interpreted restrictively.

Claims

1. A first mirror including a first hole that transmits incident laser light; A second mirror that reflects laser light incident through the first hole; A third mirror that reflects laser light incident through the second mirror; A fourth mirror that reflects laser light incident through the third mirror; and A nonlinear crystal that expands the spectrum of laser light traveling back and forth through the first mirror, the second mirror, the third mirror, and the fourth mirror, wherein The first mirror, the second mirror, the third mirror, and the fourth mirror are arranged facing each other with the non-linear crystal in between, and The first mirror, the second mirror, the third mirror, and the fourth mirror each include a plurality of first points, a plurality of second points, a plurality of third points, and a plurality of fourth points for reflection of a plurality of laser lights between them in a predetermined order. An ultrashort pulse width compression device for spectrum expansion, wherein the second mirror includes a second hole that transmits the laser light finally reflected through the first mirror to the outside.

2. In Paragraph 1, The above plurality of first points are, Three equally spaced mirrors are formed to reflect a plurality of laser lights incident through the fourth mirror to the second mirror, and The above plurality of second points are, Three mirrors are formed at equal intervals to reflect a plurality of laser lights incident through the first mirror to the third mirror, and The above plurality of third points are, Three mirrors are formed at equal intervals to reflect a plurality of laser lights incident through the second mirror to the fourth mirror, and The above plurality of fourth points are, An ultrashort pulse width compression device for spectrum expansion, characterized by being formed at three equal intervals to reflect a plurality of laser lights incident through the third mirror to the first mirror.

3. In Paragraph 2, The above laser light is, An ultrashort pulse width compression device for spectrum expansion, characterized by forming a round-trip path in sequence, one by one, through the plurality of first points, the plurality of second points, the plurality of third points, and the plurality of fourth points.

4. In Paragraph 1, A first lens provided in alignment with the first mirror and the fourth mirror and focusing the laser light; and An ultrashort pulse width compression device for spectrum expansion, further comprising a second lens that is positioned in alignment with the second mirror and the third mirror and focuses the laser light.

5. In Paragraph 4, An ultrashort pulse width compression device for spectrum expansion, characterized in that the focusing intensity in the nonlinear crystal is determined according to the focal distance between the first lens and the second lens.

6. In Paragraph 5, The above nonlinear crystal is, A spectral expansion ultrashort pulse width compression device characterized by having a plurality of lenses arranged between the first lens and the second lens to adjust the magnification ratio of the spectrum.

7. A first mirror including a first hole that transmits incident laser light; A second mirror that reflects laser light incident through the first hole; A third mirror that reflects laser light incident through the second mirror; A fourth mirror that reflects laser light incident through the third mirror; and A nonlinear crystal that expands the spectrum of laser light traveling back and forth through the first mirror, the second mirror, the third mirror, and the fourth mirror, wherein The first mirror, the second mirror, the third mirror, and the fourth mirror are arranged facing each other with the non-linear crystal in between, and The first mirror, the second mirror, the third mirror, and the fourth mirror each include a plurality of first points, a plurality of second points, a plurality of third points, and a plurality of fourth points for reflection of a plurality of laser lights between them in a predetermined order. The above-mentioned fourth mirror includes a second hole that transmits the laser light finally reflected through the third mirror to the outside, an ultrashort pulse width compression device according to spectrum expansion.

8. In Paragraph 7, The above plurality of first points are, Two mirrors are formed at equal intervals to reflect a plurality of laser lights incident through the fourth mirror to the second mirror, and The above plurality of second points are, Three mirrors are formed at equal intervals to reflect a plurality of laser lights incident through the first mirror to the third mirror, and The above plurality of third points are, Three mirrors are formed at equal intervals to reflect a plurality of laser lights incident through the second mirror to the fourth mirror, and The above plurality of fourth points are, An ultrashort pulse width compression device for spectrum expansion, characterized by having two equally spaced mirrors formed to reflect a plurality of laser lights incident through the third mirror to the first mirror.

9. In Paragraph 8, The above laser light is, An ultrashort pulse width compression device for spectrum expansion, characterized by forming a round-trip path in sequence, one by one, through the plurality of first points, the plurality of second points, the plurality of third points, and the plurality of fourth points.

10. In Paragraph 7, A first lens provided in alignment with the first mirror and the fourth mirror and focusing the laser light; and An ultrashort pulse width compression device for spectrum expansion, further comprising a second lens that is positioned in alignment with the second mirror and the third mirror and focuses the laser light.

11. In Paragraph 10, An ultrashort pulse width compression device for spectrum expansion, characterized in that the focusing intensity in the nonlinear crystal is determined according to the focal distance between the first lens and the second lens.

12. In Paragraph 11, The above nonlinear crystal is, A spectral expansion ultrashort pulse width compression device characterized by having a plurality of lenses arranged between the first lens and the second lens to adjust the magnification ratio of the spectrum.

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