JP4899705B2 - Optical amplification module - Google Patents

Description

The present invention relates to an optical amplification module.

Processing technology using laser light has attracted attention, and in each field including the medical field, demand for an optical amplification module capable of generating high-power laser light is increasing. As an optical amplification module, for example, a double clad type optical fiber in which a rare earth element excited by excitation light is added to a core region is used as an amplification optical fiber (see Non-Patent Document 1). ). The optical amplification module described in Non-Patent Document 1 is used as a fiber laser light source, and supplies pumping light to an amplification optical fiber by using an optical module having an LD with a fiber and an optical coupling means. Yes.
Koji Sugioka, Akira Yabe, "Laser Micro / Nano Processing", 1st edition, Japan, CM Publishing, November 2004, pp67-68

  By the way, normally, the amplification optical fiber included in the optical amplification module is supplied with amplified light and excitation light using an optical module as shown in FIG.

  The optical module 110 of the optical amplification module 100 shown in FIG. 7 includes an excitation light source 40 that outputs excitation light, and an optical coupling unit 120 that combines the excitation light and the light to be amplified and inputs them to the amplification optical fiber. It has. The optical coupling means 120 includes an optical fiber 51 as an input port for amplified light, an optical fiber 121 as an input port for pumping light, an optical coupling unit 53 as a multiplexing medium for amplified light and pumping light, and an output. The optical fiber 54 is a port, and the amplified light source 10 is connected to the optical fiber 51, and the amplification optical fiber 20 is connected to the optical fiber 54. With the above configuration, the light to be amplified and the pump light output from the light source to be amplified 10 and the pump light source 40 are input to the amplification optical fiber 20 via the optical coupling means 120. Then, the light to be amplified is amplified in the amplification optical fiber 20 and outputted as high-power light. In order to output light with higher output from the amplification optical fiber 20, it is conceivable to use a so-called multimode fiber that propagates pumping light in multimode as the optical fiber 121.

  However, when the amplification optical fiber 20 is connected to another optical fiber or the like, a connection loss occurs at the connection portion, and the amplified light as the loss is, for example, in the direction opposite to the propagation direction of the excitation light in the amplification optical fiber 20. May propagate to In this case, if the optical fiber 121 is a multimode fiber, the multimode fiber has a large core diameter and NA, so that light other than the pumping light is easily confined in the fiber, and thus propagates in the opposite direction to the pumping light. A case where high-power amplified light propagates to the excitation light source 40 may occur. In this case, the pumping light source 40 is broken or the operation becomes unstable, so that the pumping light cannot be stably supplied to the amplification optical fiber, and as a result, there is a possibility that high output light cannot be generated.

Therefore, an object of the present invention is to provide an optical amplification module that can stably supply pumping light to an amplification optical fiber.

An optical amplification module according to the present invention includes an excitation light source, an optical coupling means, a guide optical fiber, and an amplification optical fiber , and supplies the excitation light and the amplified light to the amplification optical fiber to amplify the amplified light. a of the optical amplifier module, the optical coupling means connects the pumping light source and guide optical fiber optically, and outputs the excitation light from the excitation light source to guide optical fiber, the guide optical fibers, the amplification The optical fiber for guide is provided on the outer periphery of the first core region and the first core region, and has a refractive index lower than the refractive index of the first core region. A first cladding region, and a second cladding region provided on the outer periphery of the first cladding region and having a refractive index lower than the refractive index of the first cladding region. Propagate light to be amplified At the same time, the excitation light from the optical coupling means is propagated in multimode in the first core region and the first cladding region, and the first cladding region is larger than the wavelength of the excitation light than the wavelength of the excitation light. An element having a transmission loss is added.

  In this configuration, when the amplification optical fiber is optically connected to the guide optical fiber, the excitation light output from the excitation light source is input to the guide optical fiber through the optical coupling means, and the guide optical fiber After propagating through the first core region and the first cladding region, the light is input to the amplification optical fiber. In this way, when pump light is input into the amplification optical fiber, if the amplified light is supplied into the amplification optical fiber, the amplified light is optically amplified in the amplification optical fiber. High output light can be generated.

  By the way, for example, when a connection loss occurs due to a mode field diameter (MFD) mismatch or the like in the connection portion when the amplification optical fiber is connected to another optical fiber, the amplified light as the connection loss is excited. It may propagate toward the excitation light source in the direction opposite to the light propagation direction.

In the optical amplification module having the above configuration, the guide optical fiber is disposed between the optical coupling means and the amplification optical fiber by optically connecting the guide optical fiber and the amplification optical fiber. . In the first clad region of the guide optical fiber, an element having a transmission loss larger than the wavelength of the light to be amplified is added to the wavelength of the light to be amplified. The amplified light propagating in the direction opposite to the light propagation direction does not reach the pumping light source while maintaining a high output that affects the pumping light source. As a result, the pumping light source is not broken or the operation becomes unstable, so that the pumping light can be stably supplied to the amplification optical fiber.

In the optical amplification module according to the present invention, the element can be a rare earth element.

In the optical amplification module according to the present invention, the amplification optical fiber is provided on the outer periphery of the second core region and the second core region, and has a refractive index lower than the refractive index of the second core region. A third cladding region, and a fourth cladding region that is provided on the outer periphery of the third cladding region and has a refractive index lower than that of the third cladding region. In the second core region, It is preferable to propagate the light to be amplified and propagate the pumping light from the guide optical fiber in the second core region and the third cladding region.

  The amplification optical fiber having this configuration is a so-called double clad type optical fiber in which third and fourth clad regions are provided on the outer periphery of the second core region. In the amplification optical fiber, since the pumping light is propagated in the second core region and the third cladding region, more pumping light can be propagated, so that the amplified light can be amplified more efficiently. it can.

Further, in the optical amplifier module according to the present invention, the amplified light outputted from the guide optical fiber is inputted to the amplifying optical fiber, at a wavelength of the light to be amplified, the mode field diameter of the amplifying optical fiber, for guiding It is preferable that it is larger than or equal to the mode field diameter of the optical fiber.

  When the amplified light output from the guide optical fiber is input to the amplification optical fiber, the MFD for the wavelength of the amplified light in the guide optical fiber and the amplification optical fiber satisfies the relationship as described above. Since the connection loss with respect to the light to be amplified is reduced, the light to be amplified is further prevented from entering the excitation light source. As a result, excitation light can be supplied to the amplification optical fiber more stably.

In the optical amplification module according to the present invention, the light to be amplified output from the optical fiber for amplification is input to the optical fiber for guide, and the mode field diameter of the optical fiber for amplification is the guide wavelength at the wavelength of the light to be amplified. The mode field diameter of the optical fiber is preferably equal to or smaller than that.

  When the amplified light output from the amplification optical fiber is input to the guide optical fiber, the MFD with respect to the wavelength of the amplified light in the guide optical fiber and the amplification optical fiber satisfies the above relationship. Since the connection loss for the amplified light is reduced, the amplified light is further suppressed from entering the excitation light source. As a result, excitation light can be supplied to the amplification optical fiber more stably.

Further, in the optical amplifier module according to the present invention, the amplified light outputted from the amplification optical fiber is inputted to guide optical fiber, optical coupling means different from other optical coupling means and the guide optical fiber different from other for The guide optical fiber and the other guide optical fiber are separately disposed on both sides of the amplification optical fiber and optically connected to the amplification optical fiber. The coupling means receives the amplified light and other excitation light different from the excitation light, and the other optical coupling means passes the inputted amplified light and the other excitation light to another guide optical fiber. The other guiding optical fiber outputs the inputted amplified light and other pumping light to the guiding optical fiber of the amplifying optical fiber, and the other guiding optical fiber has a first 'core region. And provided on the outer periphery of the first 'core region A first ′ cladding region having a refractive index lower than that of the 1 ′ core region, and a refractive index lower than the refractive index of the first ′ cladding region provided on the outer periphery of the first ′ cladding region; A second ′ cladding region for propagating light to be amplified in the first ′ core region and other excitation from other optical coupling means in the first ′ core region and the first ′ cladding region. The light is propagated in multimode, and an element having a transmission loss larger than the wavelength of the other pumping light with respect to the wavelength of the amplified light is added to the first 'cladding region. The mode field diameter of the guiding optical fiber is preferably equal to or larger than the mode field diameter of the other guiding optical fibers.

  In this configuration, the guide optical fiber and the other guide optical fibers are optically connected to both sides of the amplification optical fiber. The pumping light is supplied to the amplification optical fiber through the optical coupling means and the guide optical fiber. Further, other pumping light input to the other guide optical fiber through the other optical coupling means propagates through the first ′ core region and the first ′ clad region of the other guide optical fiber. Further input to the amplification optical fiber. In this manner, since the pumping light and other pumping light are input from the guide optical fiber and the other guide optical fiber to the amplification optical fiber, the light to be amplified passes through the other guide optical fiber to the amplification optical fiber. When input, the amplified light can be efficiently amplified in the amplification optical fiber, and the amplified light can be output to the guide optical fiber. Further, in the first cladding region of the guide optical fiber and the first ′ cladding region of the other guide optical fiber, an element having a transmission loss larger than the wavelength of the pumping light with respect to the wavelength of the amplified light. Since it is added, the amplified light does not reach the excitation light source while maintaining a high output that affects the excitation light source. As a result, the pumping light source is not broken or the operation becomes unstable, so that the pumping light can be stably supplied to the amplification optical fiber.

  Furthermore, since the MFD with respect to the wavelength of the light to be amplified in the guide optical fiber and other guide optical fibers satisfies the above relationship, the light to be amplified is further prevented from entering the excitation light source. The pumping light can be supplied to the amplification optical fiber more stably.

According to the optical amplification module of the present invention, the excitation light can be stably supplied to the amplification optical fiber. Therefore, it is possible to stably output high-power light from the amplification optical fiber.

  Hereinafter, an embodiment of an optical module according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

(First embodiment)
FIG. 1 is a configuration diagram schematically showing the configuration of the optical amplification module of the first embodiment. The optical amplification module 1 is used as a fiber laser light source in an optical processing system, and an embodiment of an optical module according to the present invention is applied.

Optical amplifier module 1 includes a target amplification source 10 which outputs a processing laser beam of a wavelength lambda _A as the light to be amplified, the amplification optical fiber 20 by using the excitation light and outputs a processing laser beam by optical amplification And an optical module 31 for supplying processing laser light and excitation light to the amplification optical fiber 20. The amplified light source 10 is, for example, a laser diode (LD).

  FIG. 2A is a cross-sectional view substantially orthogonal to the longitudinal direction of the amplification optical fiber. FIG. 2B is a diagram showing the refractive index distribution of the amplification optical fiber.

The amplification optical fiber 20 is composed mainly of SiO ₂ , and includes a core region (second core region) 20A, and a cladding region (third cladding region) 20B provided on the outer periphery of the core region 20A. , A double clad optical fiber having a clad region (fourth clad region) 20C provided on the outer periphery of the clad region 20B. The diameter of the core region 20A is exemplified as 10 μm, the diameter of the cladding region 20B outside the core region 20A is exemplified as 100 μm, and the diameter of the cladding region 20C outside the cladding region 20B is exemplified as 125 μm.

  A rare earth element such as Yb or Er (hereinafter referred to as “light amplification element”) E1 is added to the core region 20A of the amplification optical fiber 20 to amplify the processing laser light by supplying excitation light. Has been. FIG. 2A schematically shows the light amplification element E1. Although the rare earth element for amplifying the processing laser beam may be added to the cladding region 20B, in that case, it has a larger transmission loss with respect to the wavelength of the pumping light than the wavelength of the processing laser beam. Those are preferred.

  As shown in FIG. 2B, the refractive index of the cladding region 20B is lower than the refractive index of the core region 20A, and the refractive index of the cladding region 20C provided on the outer periphery of the cladding region 20B is the refractive index of the cladding region 20B. It is lower. The refractive index profile as shown in FIG. 2B may be formed using a refractive index adjusting agent such as Ge.

  The amplification optical fiber 20 propagates the processing laser light in a single mode in the core region 20A and propagates the excitation light in a multimode in the core region 20A and the cladding region 20B. The core region 20A only needs to be able to propagate the processing laser beam, and the processing laser beam may be propagated in multimode.

As shown in FIG. 1, the optical module 31 has a plurality (e.g., six in Figure 1) for outputting a laser beam having a wavelength lambda _P as excitation light for amplifying the pump light source 40, the processing laser beam and the excitation light An optical coupling means 50 for inputting to the optical fiber 20, and a guide optical fiber 60 connecting the optical coupling means 50 and the amplification optical fiber 20 are provided. The excitation light source 40 and the guide optical fiber 60 are provided. Are optically connected by the optical coupling means 50. The excitation light source 40 is, for example, an LD.

  The optical coupling means 50 includes an optical fiber 51 that propagates the processing laser light and a plurality of optical fibers 52 that propagate the excitation light in a multimode. The amplified light source 10 is connected to the optical fiber 51, and the optical fiber 51 functions as an input port for processing laser light output from the amplified light source 10. The pumping light source 40 is connected to the optical fiber 52, and the optical fiber 52 functions as an input port for pumping light output from the pumping light source 40.

  The optical coupling means 50 includes an optical coupling portion 53 for combining the processing laser light and the excitation light that have propagated through the optical fibers 51 and 52, and the processing laser light and the excitation light that have passed through the optical coupling portion 53. Is further input to the guide optical fiber 60.

  The optical fiber 54 is optically connected to the guide optical fiber 60, propagates the processing laser light, and inputs it to a core region (first core region) 60 </ b> A of the guide optical fiber 60, which will be described later. The light is propagated in multimode and input to the core region 60A and the cladding region (first cladding region) 60B. The optical fiber 54 only needs to be able to propagate the processing laser light and multi-mode propagate the excitation light and input it to the guide optical fiber 60 as described above. For example, a core region for propagating the processing laser light; It is only necessary to have a first cladding region that propagates excitation light in multimode. When optical fibers are optically connected as in the case of optically connecting the optical fiber 54 and the guide optical fiber 60, fusion connection may be used, connector connection, etc. May be used.

  As a more specific configuration of the optical coupling means 50, as shown in FIG. 3, an optical fiber 51 and an optical fiber 52 are integrated by being taper-extended (for example, Japanese Patent No. 34149). reference). In the optical coupling means 50 shown in FIG. 3, the tapered portion where the optical fiber 51 and the optical fiber 52 are coupled is an optical coupling portion 53, and the optical fiber 54 is optically connected to the optical coupling portion 53. ing. When the optical coupling portion 53 is further extended from the taper portion to a constant outer diameter and the amplification optical fiber 20 has a portion capable of inputting processing laser light and excitation light as described above, the optical fiber 54 is It does not have to be provided.

  The optical module 31 shown in FIG. 1 has a plurality of excitation light sources 40. However, the number of excitation light sources 40 may be adjusted according to the power of the excitation light supplied to the amplification optical fiber 20, and the excitation light sources 40 As long as is high output, one may be used. Further, the number of pumping light sources 40 and the number of optical fibers 52 are made to correspond to each other. For example, when the number of optical fibers 52 is larger than the number of pumping light sources 40, the ends of the unused optical fibers 52 The unit may be terminated so that light is not reflected.

As shown in FIG. 4, the guide optical fiber 60 is composed mainly of SiO ₂ , and includes a core region (first core region) 60A and a cladding region (first core region) provided on the outer periphery of the core region 60A. 1 clad region) 60B and a clad region (second clad region) 60C provided on the outer periphery of the clad region 60B. FIG. 4 is a cross-sectional view substantially perpendicular to the longitudinal direction of the guide optical fiber.

The cladding region 60B, rare earth elements having a greater transmission loss to the wavelength lambda _A of the processing laser light from the wavelength lambda _P of the pumping light (hereinafter referred to as "light absorbing element") E2 is added. FIG. 4 schematically shows the light-absorbing element E2. Note that the optical amplification element E <b> 1 may be added to the core region 60 </ b> A as in the case of the amplification optical fiber 20.

  The magnitude relationship of the refractive indexes of the core region 60A, the cladding region 60B, and the cladding region 60C included in the guide optical fiber 60 is the same as that of the amplification optical fiber 20, and the guide optical fiber 60 also includes the core region 60A. While processing laser light is propagated, excitation light is propagated in multimode in the core region 60A and the cladding region 60B.

Next, the operation of the optical amplification module 1 will be described. Here, as an example, the wavelength λ _A of the processing laser light is about 1060 nm, and the wavelength λ _{P of the} excitation light is about 974 nm. The optical amplification element E1 added to the amplification optical fiber 20 is, for example, Yb, which is a rare earth element. FIG. 5 is a diagram showing the absorption / radiation characteristics of Yb. As shown in FIG. 5, it can be seen that Yb absorbs a lot of light in the wavelength band of about 915 nm (915 nm ± 30 nm) and light in the 974 nm band (974 nm ± 10 nm). Bands are often used. Here, as an example, the wavelength of the 974 nm band having a large absorption coefficient is used as the excitation LD. However, even if the wavelength of the 915 nm band is used as the excitation LD, there is no difference in the wavelength band to be amplified. There is no change in the operation and effect of the module 31. It can also be seen from FIG. 5 that when Yb is excited in either of the two wavelength bands, it has an amplification band of 1020 to 1080 nm, and here, particularly, light of 1060 nm was used. From FIG. 5, it is clear that there is a difference between the excitation light wavelength and the amplification wavelength band, and considering the action and effect of the optical module 31 in which a medium having a different absorption coefficient depending on the excitation light wavelength and the amplified light wavelength is considered. As long as the wavelength of the laser beam is arranged between 1020 and 1080 nm, the action and effect of the optical module 31 are the same.

  The light absorbing element E2 added to the cladding region (first cladding region) 60B of the guide optical fiber 60 is, for example, Tm, which is a rare earth element. FIG. 6 is a diagram showing the absorption characteristics of Tm (“Tetsuro Komukai et. Al.“ Upconversion Pumped Thulium-Doped Fluride Fiber Amplifier and Laser Operating at 1.47 μm, ”IEEE JOURNAL OF QUANTUM ELECTRONICS, NOVENBER 1995, VOL.31, NO. 11, pp1880-1889 "). As shown in FIG. 6, at Tm, the absorption coefficient for light having a wavelength of about 974 nm is small, and the absorption coefficient for light in the vicinity of a wavelength of 1060 nm is large. That is, Tm as the light absorbing element E2 has a property of mainly absorbing the processing laser light from the excitation light, and as a result, the processing laser light receives a larger transmission loss due to Tm. .

  In the optical amplification module 1 having the above conditions, when each pumping light source 40 outputs pumping light having a wavelength of about 974 nm, the pumping light propagates in the multimode through the optical fiber 52 connected to each pumping light source 40, and then the optical coupling unit. 53 and the optical fiber 54 to be input to the guide optical fiber 60 and propagate in the guide optical fiber 60 toward the amplification optical fiber 20.

  Tm is added as a light absorbing element E2 to the cladding region (first cladding region) 60B of the guide optical fiber 60. As shown in FIG. 6, Tm almost radiates light having a wavelength of about 974 nm. Since it does not absorb, the excitation light is reliably incident on the amplification optical fiber 20. Then, the excitation light incident on the amplification optical fiber 20 propagates toward the end 20b while exciting Yb, which is the optical amplification element E1 added in the core region 20A.

  When the amplified light source 10 outputs a processing laser beam having a wavelength of 1060 nm, the processing laser beam propagates through the optical fiber 51 and is input to the guide optical fiber 60 through the optical coupling portion 53 and the optical fiber 54. Is done. The processing laser light input to the guide optical fiber 60 propagates through the core region 60A of the guide optical fiber 60 and is input into the amplification optical fiber 20, and then the core region 20A of the amplification optical fiber 20. Propagates toward the end 20b.

  At this time, if Yb, which is the optical amplification element E1 added in the core region 20A as described above, is excited by the excitation light, stimulated emission is generated by the processing laser light. Amplified. Therefore, the optically amplified high-power processing laser beam is output from the end portion 20 b of the amplification optical fiber 20.

  In the optical amplification module 1, it is important that the optical module 31 has the guide optical fiber 60, and the guide optical fiber 60 is provided between the optical coupling means 50 and the amplification optical fiber 20. is there. Here, the operation and effect of the optical module 31 having the guide optical fiber 60 will be described in comparison with the optical amplification module 100 to which the comparative optical module 110 shown in FIG. 7 is applied.

  The optical module 110 included in the comparative optical amplification module 100 shown in FIG. 7 includes an excitation light source 40 and an optical coupling unit 120. The optical coupling unit 120 is an input port for processing laser light and excitation light. Optical fibers 51 and 121, an optical coupling portion 53 as a combining medium for processing laser light and excitation light, and an optical fiber 54 as an output port in the optical coupling means 120. In the following description, the configuration of the optical fiber 121 is the same as the configuration of the optical fiber 52 and is a so-called multimode fiber that propagates pumping light in multimode.

  The optical amplification module 100 is configured by optically connecting the amplified light source 10 to an optical fiber 51 included in the optical module 110 and optically connecting the amplification optical fiber 20 to an optical fiber 54. In FIG. 7, only one excitation light source 40 is shown for simplicity of explanation.

  In the optical amplification module 100, the processing laser light from the light source to be amplified 10 and the excitation light from the excitation light source 40 are supplied to the amplification optical fiber 20 via the optical coupling means 120, and the processing laser light is supplied to the amplification optical fiber. After being optically amplified at 20, the laser beam is output as a high-power processing laser beam from the end 20b.

  By the way, when the end portion 20b of the amplification optical fiber 20 is connected to another optical fiber, a connection loss due to, for example, MFD mismatch or axial misalignment occurs in the connection portion, and high-power processing for the loss is generated. Laser light may enter the clad region 20B (see FIG. 2) of the amplification optical fiber 20 as return light. Further, when the optical amplification module 100 is applied to an optical processing system or the like as described above, a high-intensity processing laser beam output from the end portion 20b is used as another optical element (lens, mirror) or the like of the optical processing system. May be incident on the cladding region 20B as return light. In such a case, there may be processing laser light that propagates in the excitation light propagation region toward the excitation light source 40.

  In the optical amplifying module 100, the optical fiber 54 of the optical module 110 and the amplifying optical fiber 20 are optically connected. The processing laser light is input into the optical fiber 54 while maintaining its output, and then propagates in the optical module 110 in the direction opposite to the propagation direction of the excitation light.

  In order to prevent high-power processing laser light from being input to the excitation light source 40, an optical fiber 121 serving as an excitation light input port may be provided with an isolator, a fiber grating, or the like. Since it is a mode fiber, an isolator or the like effective for adjusting the propagation direction of light propagating in a single mode may not cut high-power processing laser light propagating toward the excitation light source 40. As a result, the high-power processing laser beam reaches the pumping light source 40, and the pumping light source 40 may be broken or the operation may become unstable, so that the high-power processing laser beam may not be stably output. is there.

  In contrast, in the optical amplification module 1, the optical module 31 has the guide optical fiber 60, and the amplification optical fiber 20 is optically connected to the guide optical fiber 60. Accordingly, the guide optical fiber 60 in which the light absorption element E2 is added to the cladding region (first cladding region) 60B is disposed between the optical coupling means 50 and the amplification optical fiber 20. Therefore, as described above, even if the processing laser light propagates from the amplification optical fiber 20 toward the optical coupling means 50 side, the processing laser light passes through the guide optical fiber 60. A large transmission loss is caused by being absorbed by the light absorbing element E2. For this reason, the pumping light source 40 is not broken or unstable by the processing laser light as the return light, so that the pumping light can be stably supplied to the amplification optical fiber 20. In the amplification module 1, the processing laser beam can be stably output from the end 20b.

  Further, since the pumping light output from each pumping light source 40 is propagated in the multimode using the optical fiber 52, the optical fiber for amplification is used rather than using the optical fiber that propagates the pumping light in the single mode. 20 can supply a large amount of excitation light. Therefore, since the processing laser beam can be efficiently amplified, it is possible to output a higher-power processing laser beam. Therefore, the optical amplification module 1 can stably output high-power processing laser light from the end 20b.

  As described above, the light absorbing element E2 is for preventing the processing laser light as the return light from reaching the excitation light source 40 and breaking the excitation light source 40. Therefore, as the light absorbing element E2 added to the guide optical fiber 60, the transmission of the processing laser beam can be suppressed so that the excitation light source 40 is not damaged or the operation thereof is unstable. Any material that can propagate the excitation light may be used.

By the way, when the processing laser light is input to the amplification optical fiber 20 through the guide optical fiber 60 as in the optical amplification module 1, the processing laser light enters the excitation light source 40 as return light. From the viewpoint of further suppressing this, the MFD of the amplification optical fiber 20 is preferably equal to or greater than the MFD of the guide optical fiber 60 at the wavelength λ _A of the processing laser light.

With such a configuration, since the connection loss at the connection portion between the guide optical fiber 60 and the amplification optical fiber 20 is reduced, the processing laser light is suppressed from returning to the optical coupling means 50 side. As a result, the processing laser beam is less likely to be incident on the excitation light source 40, so that the processing laser beam can be generated more stably and with high output. Similarly, from the viewpoint of reducing the connection loss at the connection portion between the optical fiber 54 and the guide optical fiber 60, the mode field diameter (MFD) of the guide optical fiber 60 at the wavelength λ _A of the processing laser light. Is more preferably equal to or larger than the MFD of the optical fiber 54.

  The magnitude relationship between the MFDs of the amplification optical fiber 20 and the guide optical fiber 60 described above is particularly effective when the optical amplification element E1 is added to the core region 60A of the guide optical fiber 60.

When the optical amplification element E1 is added to the core region 60A, the guide optical fiber 60 also functions as an amplification optical fiber. Therefore, the optically amplified laser beam for processing reaches the connection portion between the amplification optical fiber 20 and the guide optical fiber 60. Therefore, as described above, when the MFD of the amplification optical fiber 20 is equal to or higher than the MFD of the guide optical fiber 60 with respect to the wavelength λ _A , the high-power processing laser light is supplied to the excitation light source 40. As a result, the laser beam for processing with high output can be stably output from the end portion 20b.

(Second Embodiment)
FIG. 8 is a configuration diagram schematically showing the configuration of the optical amplification module of the second embodiment. The optical amplification module 2 is a so-called backward pumping type optical amplification module.

  In the optical amplification module 2, the amplified light source 10 is connected to the end 20a of the amplification optical fiber 20, and the processing laser light output from the amplified light source 10 passes through the amplification optical fiber 20 from the end 20a. Propagate toward the end 20b. An optical module 32 is optically connected to the end 20 b of the amplification optical fiber 20.

  As in the optical module 31 of the first embodiment, the optical module 32 is configured such that the excitation light source 40 is optically connected to the optical fiber 52 of the optical coupling means 50, and the guide optical fiber 60 is connected to the optical fiber 54. Are optically connected. In this embodiment, the guide optical fiber 60 is optically connected to the end 20 b of the amplification optical fiber 20. In this configuration, the optical fiber 54 functions as an input port for the processing laser light and also functions as an output port for the excitation light. The optical fiber 51 functions as an output port.

  The operation of the optical amplification module 2 will be described. Excitation light output from the excitation light source 40 is input into the guide optical fiber 60 through the optical coupling means 50, propagates through the guide optical fiber 60, and then input into the amplification optical fiber 20. Then, the excitation light input to the amplification optical fiber 20 excites the optical amplification element E1 while propagating toward the end 20a. Further, the processing laser light output from the amplified light source 10 is input to the amplification optical fiber 20 from the end portion 20 a and propagates in the amplification optical fiber 20 toward the optical coupling means 50.

  When the processing laser light is input from the light source to be amplified 10 to the amplification optical fiber 20 with the optical amplification element E1 being excited, stimulated emission occurs and the processing laser light is optically amplified. The optically amplified laser beam for processing is input to the optical fiber 51 through the optical fiber 54 and the optical coupling unit 53 and then output from the end of the optical fiber 51. As a result, a high-power processing laser beam is output from the optical fiber 51.

  Also in the optical amplification module 2, the optical module 32 has the guide optical fiber 60 in which the light absorption element E <b> 2 is added to the cladding region (first cladding region) 60 </ b> B, and is amplified through the guide optical fiber 60. The pumping light is supplied to the optical fiber 20 for use.

  For this reason, even if the processing laser light enters the cladding region 60B of the guide optical fiber 60 due to MFD mismatch or axial misalignment at the connection portion between the amplification optical fiber 20 and the guide optical fiber 60, the light absorbing element E2 As a result, the laser beam for processing receives a large transmission loss. As a result, the processing laser light as a loss caused by connection loss or the like is suppressed from reaching the excitation light source 40. Therefore, since the excitation light source 40 is not broken or unstable by the high-power processing laser light, the high-power processing laser light can be output stably.

When the processing laser light is input from the amplification optical fiber 20 to the guide optical fiber 60 as in the optical amplification module 2, as in the case of the optical amplification module 1, From the viewpoint of suppressing the incidence of the laser beam, it is preferable that the MFD of the amplification optical fiber 20 is equal to or smaller than the MFD of the guide optical fiber 60 at the wavelength λ _A of the processing laser beam.

Thereby, the connection loss with respect to the processing laser light is reduced at the connection portion between the guide optical fiber 60 and the amplification optical fiber 20. Therefore, the processing laser light is further suppressed from entering the excitation light source 40 as the return light, and as a result, the processing laser light with higher output can be generated more stably. Further, the return light of the processing laser beam from further suppressing, at the wavelength lambda _A, MFD of the optical fiber 54 is further preferably larger greater than or equal to the MFD of the guide optical fiber 60.

  Although the optical module 32 has a plurality of excitation light sources 40, it may be one as in the case of the first embodiment.

(Third embodiment)
FIG. 9 is a configuration diagram schematically showing the configuration of the optical amplification module of the third embodiment. The optical amplification module 3 is a so-called bidirectional excitation type optical amplification module. Another embodiment of the optical module according to the present invention is applied to the optical amplification module 3.

  The optical amplification module 3 includes an amplified light source 10, an amplification optical fiber 20, and an optical module 33. In the following description, the direction from the end 20a to the end 20b of the amplification optical fiber 20 is referred to as the forward direction, and the direction from the end 20b to the end 20a is referred to as the reverse direction.

  The optical module 33 is disposed on the end 20 a side of the amplification optical fiber 20, and a forward light supply unit 33 A that supplies excitation light to the amplification optical fiber 20 in the forward direction, and an end of the amplification optical fiber 20. And a reverse-direction light supply unit 33B that supplies excitation light to the amplification optical fiber 20 in the reverse direction.

  The configuration of the reverse direction light supply unit 33B is the same as the configuration of the optical module 32 of the second embodiment. That is, the reverse light supply unit 33B includes the excitation light source 40, the optical coupling unit 50, and the guide optical fiber 60, and the excitation light source 40 and the guide optical fiber 60 are optically connected to the optical coupling unit 50. Has been configured. The reverse direction light supply unit 33B is optically connected to the amplification optical fiber 20 by optically connecting the guide optical fiber 60 to the end 20b of the amplification optical fiber 20.

  The forward light supply unit 33A is different from the excitation light source 40, the optical coupling unit 50, and the guide optical fiber 60 included in the backward light supply unit 33B. An optical fiber 90 is provided.

  The configuration of the guide optical fiber 90 is the same as the configuration of the guide optical fiber 60 having the cross-sectional configuration shown in FIG. That is, the guide optical fiber 90 includes a core region (first ′ core region) 60A and a cladding region (first ′ cladding region) 60B provided on the outer periphery of the core region 60A and having a refractive index smaller than that of the core region 60A. And a clad region (second 'clad region) 60C provided on the outer periphery of the clad region 60B and having a refractive index smaller than that of the clad region 60B. Similarly to the guide optical fiber 60, the light absorbing element E2 is added to the cladding region 60B of the guide optical fiber 90. In the guide optical fiber 90, the processing laser light is propagated in the core region 60A, and the excitation light is propagated in multimode in the core region 60A and the cladding region 60B.

The configurations of the excitation light source 70 and the optical coupling unit 80 are the same as the configurations of the excitation light source 40, the optical coupling unit 50, and the guide optical fiber 60. The optical fibers 81 and 82, the optical coupling unit 83, and the optical fiber 84 included in the optical coupling unit 80 correspond to the optical fibers 51 and 52, the optical coupling unit 53, and the optical fiber 54 included in the optical coupling unit 50. The configurations of the optical fibers 81, 82, 84 and the optical coupling portion 83 are the same as the configurations of the optical fibers 51, 52, 54 and the optical coupling portion 53. The wavelength of the excitation light (other excitation light) outputted from the pumping light source 70, if excited possible range light amplifying element E1, different from the wavelength lambda _P of the pumping light outputted from the pumping light source 40 It may be.

  As shown in FIG. 9, the amplified light source 10 is optically connected to the optical fiber 81, and the optical fiber 81 functions as an input port for the processing laser light output from the amplified light source 10. . The optical fiber 82 is optically connected to the pumping light source 70 and functions as an input port for pumping light output from the pumping light source 70. The optical fiber 84 is optically connected to the guide optical fiber 60 and serves as an output port for outputting the processing laser light and the excitation light input through the optical fibers 81 and 82 to the guide optical fiber 60. It is functioning.

  Specifically, the optical fiber 84 propagates the processing laser light and inputs it to the core region 60A of the guide optical fiber 60, and propagates the excitation light in multimode and inputs it to the core region 60A and the cladding region 60B.

In the optical amplifier module 3, at the wavelength lambda _A of the processing laser beam, the MFD guide optical fiber 90 is equal to or greater than the larger the MFD of the optical fiber 84, the MFD amplification optical fiber 20 guide light It is the same as or larger than the MFD of the fiber 90. Further, at the wavelength λ _A of the processing laser light, the MFD of the guide optical fiber 60 is equal to or larger than the MFD of the amplification optical fiber 20, and the MFD of the optical fiber 54 is the same as the MFD of the guide optical fiber 60. Or larger.

  The operation of the optical amplification module 3 will be described. In the optical amplification module 3, the pumping light from the pumping light source 40 included in the backward light supply unit 33 </ b> B is input to the amplification optical fiber 20 from the end 20 b through the optical coupling unit 50 and the optical fiber 54, and the amplification optical fiber 20. The light amplifying element E1 is excited by propagating in the reverse direction. Further, other pumping light from the pumping light source 70 included in the forward light supply unit 33A is input to the amplification optical fiber 20 from the end 20a through the optical coupling means 80 and the guide optical fiber 90, and the amplification optical fiber 20 is supplied. The light amplifying element E1 is excited by propagating in the forward direction.

  When the optical amplification element E1 is excited in this way, the processing laser light output from the light source 10 to be amplified passes through the optical fiber 81, the optical coupling unit 83, and the optical fiber 84 of the forward light supply unit 33A. When the signal is input to the amplification optical fiber 20, the light is amplified. Then, the optically amplified laser beam for processing is input to the guide optical fiber 60 of the reverse direction light supply unit 33B optically connected to the end 20b, as in the second embodiment. . Then, the processing laser light input into the guide optical fiber 60 passes through the optical coupling portion 53, is input to the optical fiber 51 that functions as an output port in the present embodiment, and propagates through the optical fiber 51. Output from the end.

  Also in this case, the respective excitation lights output from the respective excitation light sources 40 and 70 are input to the amplification optical fiber 20 through the guide optical fibers 60 and 90 to which the light absorbing element E2 is added. Therefore, even when the high-power processing laser light propagates in the opposite direction to the pumping light propagating in the forward direction and the reverse direction, in the case of the optical amplification modules 1 and 2 of the first and second embodiments, Similarly to the above, a high-power processing laser beam does not enter the excitation light sources 40 and 70. Further, the MFDs of the optical fiber 84, the guide optical fiber 90, the amplification optical fiber 20, the guide optical fiber 60, and the optical fiber 54 are the same or the processing laser light is incident at the wavelength of the processing laser light. Since the MFD on the side is larger, the connection loss at the connection portion between adjacent optical fibers (for example, the connection portion between the guide optical fiber 90 and the amplification optical fiber 20) is reduced. As a result, the pumping light can be stably supplied to the amplification optical fiber 20, so that it is possible to stably generate a high-power processing laser beam.

  In this embodiment, the optical module 33 has a plurality of excitation light sources 40 and 70. However, the number of excitation light sources 40 included in the forward light supply unit 33A and the excitation light source 40 included in the backward light supply unit 33B. May be one as in the case of the optical modules 31 and 32 of the first and second embodiments.

In the optical amplification module 3, the magnitude relationship between the MFDs of the guide optical fiber 90 and the optical fiber 84 and the magnitude relationship between the MFDs of the optical fiber 54 and the guide optical fiber 60 at the wavelength λ _A of the processing laser light. Although even the same or processing laser light is set to large MFD of the side incident, the MFD guide optical fiber 60 to at least the wavelength lambda _a is equal to or a MFD of guide optical fiber 90 with respect to the wavelength lambda _a Bigger than that. In the present embodiment, the forward light supply unit 33A includes the excitation light source 70, but the optical module 3 only needs to include at least the excitation light source 40.

  Although the embodiments of the optical module of the present invention have been described above, the optical module according to the present invention and the optical amplification module to which the optical module is applied are limited to those described using the first to third embodiments. Not.

In the optical amplification modules 1 to 3, the light source 10 to be amplified is provided, but the light source 10 to be amplified is not necessarily provided. For example, in the optical amplification module 1 of FIG. 1, a resonator structure is formed by the end of the optical fiber 51 on the side to which the light source 10 to be amplified is connected and the end 20b on the output side of the amplification optical fiber 20. It is also possible. In this case, by laser oscillation in the optical amplifier module 1 can output a high intensity light wavelength lambda _A from the optical amplifier module 1.

  Moreover, although an example of the optical coupling means 50 is shown in FIG. 3, the optical coupling means 50 is not limited to that shown in FIG. The optical coupling means 50 can input pumping light to the amplification optical fiber 20 through the guide optical fiber 60 and also input the light to be amplified to the amplification optical fiber 20 through the guide optical fiber 60 (or in the amplification optical fiber 20). Any optical coupler that can output (amplified light to be amplified) may be used. Further, although the optical coupling unit 50 includes the optical fiber 54, the optical coupling unit 53 and the guide optical fiber 60 may be directly connected without providing the optical fiber 54.

  Further, in the above description, the optical amplification modules 1 to 3 are fiber laser light sources used in the optical processing system, and the laser light for laser processing is output from the light source 10 to be amplified. Instead, it is also possible to output signal light for optical communication in an optical communication system or the like.

It is a block diagram which shows schematically the structure of embodiment of the optical amplification module to which one Embodiment of the optical module which concerns on this invention is applied. (A) is sectional drawing orthogonal to the longitudinal direction of the optical fiber for amplification shown in FIG. (B) is a figure which shows the refractive index distribution in the radial direction of the optical fiber for amplification. It is sectional drawing orthogonal to the longitudinal direction of the optical fiber for guides shown in FIG. It is a perspective view of the optical coupling means shown in FIG. It is a figure which shows the absorption and discharge | release characteristic of Yb. It is a figure which shows the absorption characteristic of Tm. It is a block diagram which shows schematically the structure of the optical amplification module for a comparison. It is a block diagram which shows schematically the structure of other embodiment of an optical amplification module. It is a block diagram which shows schematically the structure of further another embodiment of an optical amplification module.

Explanation of symbols

  1, 2, 3... Optical amplification module, 20... Amplifying optical fiber, 20A... Core region (second core region), 20B... Cladding region (third cladding region), 20C. Region), 31, 32, 33 ... optical module, 40 ... excitation light source, 50 ... optical coupling means, 60 ... optical fiber for guide, 60A ... core region (first core region, first 'core region), 60B ... cladding region (first cladding region, first 'cladding region), 60C ... cladding region (second cladding region, second' cladding region), 70 ... excitation light source (other excitation light source), 80 ... Optical coupling means (other optical coupling means), 90 ... guide optical fiber (other guide optical fiber), E2 ... light absorbing element (element having a transmission loss larger than the excitation light with respect to the amplified light) .

Claims (6)

An optical amplification module comprising an excitation light source, an optical coupling means, a guide optical fiber, and an amplification optical fiber , supplying excitation light and amplified light to the amplification optical fiber, and amplifying the amplified light,
The optical coupling means optically connects the excitation light source and the guide optical fiber, and outputs excitation light from the excitation light source to the guide optical fiber.
The guide optical fiber is optically connected to the amplification optical fiber,
The guide optical fiber is:
A first core region; a first cladding region provided on an outer periphery of the first core region and having a refractive index lower than a refractive index of the first core region; and an outer periphery of the first cladding region And a second cladding region having a refractive index lower than that of the first cladding region,
Propagating the light to be amplified in the first core region, and multi-mode propagation of the excitation light from the optical coupling means in the first core region and the first cladding region,
An optical amplification module, wherein an element having a transmission loss larger than the wavelength of the light to be amplified is added to the first cladding region. The optical amplification module according to claim 1, wherein the element is a rare earth element. The amplification optical fiber includes a second core region, a third cladding region provided on an outer periphery of the second core region and having a refractive index lower than a refractive index of the second core region, A fourth cladding region provided on an outer periphery of the third cladding region and having a refractive index lower than that of the third cladding region, and propagates the amplified light in the second core region 3. The optical amplification module according to claim 1, wherein pump light from the guide optical fiber is propagated in the second core region and the third cladding region. 4. The amplified light outputted from said guide optical fiber is input to the amplifying optical fiber,
The mode field diameter of the amplification optical fiber is equal to or larger than the mode field diameter of the guide optical fiber at the wavelength of the light to be amplified. An optical amplification module according to 1. The amplified light outputted from the amplification optical fiber is input to the guide optical fiber,
4. The optical amplification module according to claim 3, wherein a mode field diameter of the amplification optical fiber is equal to or smaller than a mode field diameter of the guide optical fiber at a wavelength of the light to be amplified . The amplified light outputted from the amplification optical fiber is input to the guide optical fiber,
Another optical coupling means different from the optical coupling means, and another guide optical fiber different from the guide optical fiber,
The guide optical fiber and the other guide optical fiber are separately disposed on both sides of the amplification optical fiber, and are optically connected to the amplification optical fiber,
The other light coupling means receives the amplified light and other excitation light different from the excitation light, and the other optical coupling means receives the inputted amplified light and the other excitation light. Outputting light to the other guide optical fiber,
The other guide optical fiber inputs the input light to be amplified and the other pump light to the guide optical fiber of the amplification optical fiber,
The other guide optical fiber is:
A first ′ core region, a first ′ clad region provided on an outer periphery of the first ′ core region and having a refractive index lower than that of the first ′ core region, and the first ′ And a second ′ cladding region having a refractive index lower than the refractive index of the first ′ cladding region.
The amplified light is propagated in the first 'core region, and other excitation light from the other optical coupling means is propagated in multimode in the first' core region and the first 'cladding region. ,
In the first 'clad region, an element having a transmission loss greater than the wavelength of the amplified light is added than the wavelength of the other excitation light,
4. The optical amplification module according to claim 3, wherein a mode field diameter of the guide optical fiber is equal to or larger than a mode field diameter of the other guide optical fiber at the wavelength of the light to be amplified. .

Images