JP2007158012A - Excitation light guide member, optical fiber structure and optical device - Google Patents

Excitation light guide member, optical fiber structure and optical device Download PDF

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Publication number
JP2007158012A
JP2007158012A JP2005350983A JP2005350983A JP2007158012A JP 2007158012 A JP2007158012 A JP 2007158012A JP 2005350983 A JP2005350983 A JP 2005350983A JP 2005350983 A JP2005350983 A JP 2005350983A JP 2007158012 A JP2007158012 A JP 2007158012A
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optical fiber
excitation light
optical
introducing member
incident
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Katsuhisa Ito
Hidenori Kosugi
Hiroshi Sekiguchi
Hirobumi Suga
勝久 伊東
英徳 小杉
博文 菅
宏 関口
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Hamamatsu Photonics Kk
浜松ホトニクス株式会社
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Abstract

A pumping light introducing member capable of increasing the efficiency of pumping light introduction from a pumping light source into an optical fiber, and an optical fiber structure and an optical capable of improving optical amplification efficiency and laser oscillation efficiency in the optical fiber Providing equipment.
An optical device includes an optical fiber having a disk shape that is closely wound in a spiral shape, a reflecting member provided at one end of the optical fiber, and pumping light introduced into the optical fiber. An excitation light introducing member 13, an optical system 14 that makes the excitation light incident on the excitation light introducing member 13, and an excitation light source 15 that outputs the excitation light. The core of the optical fiber 11 contains a laser active material that can absorb excitation light of a predetermined wavelength and emit light of other wavelengths. The refractive index of the excitation light introducing member 13 is higher than the refractive index of the cladding of the optical fiber 11.
[Selection] Figure 1

Description

  The present invention relates to an optical fiber structure including an optical fiber having a core containing a laser active material, a pumping light introducing member for introducing pumping light into the optical fiber in the optical fiber structure, and an optical including the optical fiber structure. The present invention relates to an apparatus (for example, an optical amplifier or a laser oscillator).

  As an optical device including an optical fiber whose core contains a laser active substance, an optical amplifier and a laser oscillator can be cited. In an optical amplifier, pumping light is introduced into an optical fiber to excite a laser active substance, and when amplified light is input to the optical fiber, stimulated emission occurs in the optical fiber, and the amplified light is optically amplified. And output from the optical fiber. In a laser oscillator, an optical fiber is disposed in a resonator, and pumping light is introduced into the optical fiber to excite a laser active material, which causes stimulated emission in the optical fiber and laser oscillation in the resonator. Laser light is output.

  Since such an optical device uses an optical fiber as an optical amplification medium, the number of transverse modes of light amplified or oscillated in the optical fiber is small, and the output light quality is excellent. Therefore, an optical device using an optical fiber as an optical amplification medium can be suitably used for industrial purposes (particularly for machining).

  In such an optical device, a method for introducing pumping light into an optical fiber includes an end surface introducing method for introducing pumping light from the end surface of the optical fiber into the core of the optical fiber, and winding the optical fiber. The method is roughly divided into a side surface introduction method for introducing pumping light into the optical fiber cladding from the side surface of the optical fiber structure. Compared with the former end face introduction method, the latter side introduction method has higher efficiency when introducing the pumping light output from the pumping light source into the optical fiber structure, and the pumping light inlet area to the fiber is widened. Therefore, it is possible to use not only a laser diode (LD) alone but also an LD array or LD stack as a pumping light source, so that high power pumping light can be introduced into the optical fiber structure, and therefore optical amplification efficiency Also, the laser oscillation efficiency is excellent, and in this respect, it can be suitably used for industrial use (for example, see Patent Document 1 and Non-Patent Document 1).

  In the side surface introducing method, a pumping light introducing member is used to introduce pumping light into the optical fiber cladding from the side surface of the optical fiber structure. The excitation light introducing member described in Non-Patent Document 1 has a substantially flat plate shape. The excitation light is incident on the incident surface, the incident excitation light is guided inside, and the guided excitation is performed. The light is totally reflected on the inclined surface, and the totally reflected excitation light is emitted from the emission surface and is incident on the optical fiber.

In the side surface introduction method, it is possible to use not only a laser diode (LD) alone but also an LD array or an LD stack as an excitation light source. Compared with the end face introduction method, particularly in the side face introduction method, an LD array or an LD stack can be suitably used as the excitation light source in relation to the use of the excitation light introduction member as described above.
Japanese Patent Laid-Open No. 10-190097 2001 New Energy and Industrial Technology Development Organization Consignment Photon Measurement and Processing Technology (Petroleum Production System Advanced Measurement and Processing Technology Research and Development) Results Report, "Chapter VII Highly Concentrated Complete Solidification Laser Technology: Fiber Laser Research and Development" , Manufacturing Science and Technology Center, March 2002

  In the optical fiber structure and the optical device based on such a side surface introduction method, further improvement in optical amplification efficiency and laser oscillation efficiency in the optical fiber is desired. In order to improve the optical amplification efficiency and the laser oscillation efficiency, it is necessary that the input excitation light is efficiently converted into the laser output power. For this purpose, it is conceivable to increase the content of the laser active substance in the optical fiber and increase the efficiency with which the pumping light output from the pumping light source is introduced into the optical fiber. However, there is a limit to the increase in the content of the laser active substance due to concentration quenching problems and manufacturing problems.

  The present invention has been made in order to solve the above-described problems. A pumping light introducing member capable of increasing the efficiency of pumping light introduction from the pumping light source to the optical fiber, and the optical amplification efficiency in the optical fiber, An object of the present invention is to provide an optical fiber structure and an optical device capable of improving the laser oscillation efficiency.

  The pumping light introducing member according to the present invention is a pumping light introducing member that introduces pumping light into the optical fiber from the side surface of the optical fiber including the core containing the laser active substance in the cladding, and the pumping light is incident thereon. An incident surface, an inclined surface that totally reflects the excitation light incident on the incident surface and guided inside, and an emission surface that emits the excitation light totally reflected by the inclined surface and enters the optical fiber; And the refractive index of the introduction plate is higher than the refractive index of the clad of the optical fiber.

  The excitation light introducing member according to the present invention further includes a plurality of linear bodies each having an incident end where the excitation light is incident and an exit end where the excitation light incident on the incident end and guided through the interior is emitted. It is preferable that the emission ends of the plurality of linear bodies are optically connected to the incident surface of the introduction plate.

  An optical fiber structure according to the present invention includes an optical fiber including a core containing a laser active substance in a cladding, and pumping light according to the present invention that introduces pumping light into the optical fiber from a side surface of the optical fiber. And an introduction member.

  An optical device according to the present invention includes the above-described optical fiber structure according to the present invention, and a pumping light source that outputs pumping light to be introduced into an optical fiber included in the optical fiber structure. To do.

  In the pumping light introducing member according to the present invention, since the refractive index of the introducing plate for allowing the pumping light to enter the optical fiber is higher than the refractive index of the cladding of the optical fiber, the efficiency of introducing the pumping light into the optical fiber is increased. Can do. When the excitation light introducing member according to the present invention includes a plurality of linear bodies in addition to the introduction plate, the excitation light source is optically connected to the incident ends of each of the plurality of linear bodies to introduce into the optical fiber. The power of the excitation light to be increased can be increased. Moreover, the optical fiber structure and the optical device according to the present invention can improve the optical amplification efficiency and the laser oscillation efficiency in the optical fiber.

  The excitation light introducing member according to the present invention can increase the efficiency of introducing excitation light from the excitation light source to the optical fiber. In addition, the optical fiber structure and the optical device using the excitation light introducing member can improve the optical amplification efficiency and the laser oscillation efficiency in the optical fiber.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  (First embodiment)

  First, an embodiment of an excitation light introducing member according to the present invention will be described, and an optical fiber structure and an optical apparatus using the excitation light introducing member will be described. FIG. 1 is a plan view of an optical device 1 according to the first embodiment. The optical device 1 shown in this figure has an optical fiber 11 that is densely wound in a spiral shape and has a disk shape, a reflecting member 12 provided at one end of the optical fiber 11, and excitation light to the optical fiber 11. An excitation light introducing member 13 to be introduced, an optical system 14 for making the excitation light incident on the excitation light introducing member 13, and an excitation light source 15 for outputting the excitation light are provided. Among these, the optical fiber 11, the reflecting member 12, and the excitation light introducing member 13 constitute an optical fiber structure 10.

  The cross-sectional shape of the optical fiber 11 is substantially square, and the cross-sectional shape of the core in the cladding is circular. The core contains a laser active material that can absorb excitation light of a predetermined wavelength and emit light of other wavelengths. Specifically, the optical fiber 11 is mainly composed of quartz glass. Further, as the laser active substance contained in the core, any one or combination of trivalent ions of lanthanoid elements such as Yb, Er, Nd, Tm, Ho, Pr, and Ce, or some kind of Cr, Ti, and the like Of transition metal elements.

  Such an optical fiber 11 is manufactured as follows. A base material having a circular cross section is manufactured by a method similar to a method of manufacturing a normal optical fiber base material (for example, MCVD method), and the side surface of the base material having the circular cross section is ground and polished to obtain a base material having a rectangular cross section. To do. And the optical fiber 11 can be obtained by drawing this optical fiber preform. By appropriately setting various conditions during the drawing, the cross-sectional shape of the optical fiber 11 obtained by the drawing remains substantially rectangular.

  In the optical fiber structure 10, the optical fiber 11 is densely wound in a spiral shape to have a disk shape. At the time of this ticket circulation, at least a part of the optical fiber 11 is laminated in the radial direction to have a disk shape. The optical fiber 11 does not need to be laminated in the direction perpendicular to the disk surface. In this wound state, adjacent clads may be optically connected by fusion or optical resin, but more preferably polysilazane is used as an adhesive and optically connected.

  Both end faces of the optical fiber 11 may be polished flat (including oblique) or spherical. In this case, the optical fiber structure 10 is preferably used as an optical amplification medium in an optical amplifier. That is, the amplified light that has entered the core from one end face is optically amplified in the core, and the light amplified light is emitted from the other end face. At this time, it is also preferable that a reflection reducing film is provided on both end faces.

  Further, as shown in FIG. 1, a reflection member 12 that reflects light emitted from the laser active substance contained in the core of the optical fiber 11 may be provided on one end face. In this case, the other end face and the reflecting member 12 constitute an optical resonator, and the optical fiber structure 10 is suitably used as an optical amplification medium in a laser oscillator. At this time, it is also preferable that a reflection reducing film is provided on the other end surface (surface from which the laser beam is emitted). In addition, a configuration in which a fiber Bragg grating (FBG) having a reflectance of 10% or less is provided in the vicinity of an end face from which laser light is emitted, and the end face itself is polished obliquely is also preferable. As the reflection member 12, an external mirror, a dielectric multilayer film mirror attached to an end face, an optical fiber grating, or the like is preferably used.

  In addition, a disk-shaped metal plate (not shown) for cooling the optical fiber 11 is provided. The metal plate is in direct or indirect contact with the optical fiber 11 wound in a disk shape, and absorbs heat of the optical fiber 11 generated by absorption of excitation light. It is also preferable that a low-refractive index resin (for example, gel-like fluorosilicone) is provided between the metal plate and the optical fiber 11, so that excitation is performed at the interface between the resin and the clad. Since light is totally reflected, absorption of excitation light by the metal plate is prevented and heat transfer between the metal plate and the clad is improved, so that a cooling effect is increased.

  The pumping light source 15 outputs pumping light to be introduced into the optical fiber 11 included in the optical fiber structure 10, and is, for example, an LD. Preferably, a plurality of LD emitters are arranged one-dimensionally. An LD array or an LD stack in which a plurality of LD arrays are stacked. As the wavelength of the excitation light, a wavelength that can excite the laser active substance contained in the core of the optical fiber 11 is selected. The optical system 14 collimates and further converges the excitation light output from the excitation light source 15 and causes the converged excitation light to enter the one end surface 131 of the excitation light introducing member 13.

  The excitation light introducing member 13 introduces the excitation light output from the excitation light source 15 and input to the one end surface 131 through the optical system 14 into the optical fiber 11 in the stacked portion of the optical fiber 11. The pumping light introducing member 13 is made of a material having a small absorption at the pumping light wavelength, preferably synthetic quartz glass, or may be multicomponent glass, and more preferably, the clad of the optical fiber 11 is refracted. Has a refractive index higher than the refractive index. For example, the cladding 110 of the optical fiber 11 is made of pure quartz glass, whereas the excitation light introducing member 13 is made of quartz glass to which an impurity as a refractive index increasing material is added. Moreover, it is preferable that the excitation light introducing member 13 is provided so that the excitation light after introduction propagates in the extending direction of the core.

  FIG. 2 is a partial cross-sectional view of the optical fiber structure 10 according to the first embodiment. As shown in this figure, in an optical fiber structure 10, an optical fiber 11 including a core 111 is clad into a clad 110 and spirally wound into a disk shape, and the disk-shaped optical fiber. 11 are bonded by polysilazane 161, and gel-like fluorosilicones 162A and 162B, fluororesin sheets 163A and 163B, and heat conductive sheets 164A and 164B are formed above and below the optical fiber 11 having a disk shape. , And metal plates 165A and 165B are sequentially provided.

The polysilazane 161 is provided as an adhesive between the adjacent clads 110 when the optical fiber 11 is wound. This polysilazane is a transparent material whose molecular formula is represented by (SiH 2 NH) n and is hydrolyzed with moisture in the air and converted to SiO 2 . However, here, the polysilazane 161 provided as an adhesive between the clads 110 may or may not be converted. When polysilazane melted in a solvent such as xylene or mineral spirits is dropped onto the disk surface, it penetrates between the clads 110 by capillary action and the solvent evaporates, and the polysilazane acts as an adhesive between the clads 110.

Since polysilazane does not contain a carbon element, there is no absorption in the 900 nm wavelength range associated with C—H stretching vibration. On the other hand, the wavelength of the excitation light for exciting Yb 3+ added to the core 111 of the optical fiber 11 is 910 nm to 980 nm. Therefore, polysilazane does not absorb excitation light. In this respect, polysilazane is superior to conventional optical resins. Polysilazane has higher heat resistance than conventional optical resins. Furthermore, polysilazane can easily connect between the clads 110 as compared to the case of fusion splicing, and has a high yield.

  The gel-like fluorosilicone 162A is interposed between the optical fiber 11 in which the clads 110 are connected by the polysilazane 161 to form a disk and the metal plates 165A and 165B as cooling members for cooling the optical fiber 11. 162B, fluororesin sheets 163A and 163B, and heat conductive sheets 164A and 164B are provided in this order. The fluororesin sheets 163A and 163B and the heat conductive sheets 164A and 164B all have high thermal conductivity and excellent flexibility. The refractive indexes of the fluororesin sheets 163A and 163B are lower than the refractive index of the clad 110 of the optical fiber 11.

  Gel-like fluorosilicone is a very stable substance, and has excellent durability and transparency. Since the gel-like fluorosilicone does not contain a hydrogen element, the gel-like fluorosilicone does not absorb at a wavelength of about 900 nm accompanying the C—H stretching vibration, and therefore does not absorb excitation light. The gel-like fluorosilicone has a refractive index lower than that of quartz glass constituting the clad 110, and can totally reflect the excitation light at the interface with the clad 110. If the clad 110 is in direct contact with the metal plates 165A and 165B, the excitation light is absorbed by the metal plates 165A and 165B, resulting in a decrease in excitation efficiency. However, the clad 110 is gel-like fluorosilicone (or fluorine). Excitation efficiency is excellent by being in contact with the resin sheets 163A and 163B).

  Since the gel-like fluorosilicone has a high thermal conductivity, it is convenient for heat transfer cooling of the optical fiber 11 by the metal plates 165A and 165B. Further, the disk surface of the optical fiber 11 in which the clads 110 are connected by polysilazane 161 to form a disk has irregularities with the period of the diameter of the optical fiber 11, but even in that case, the optical fiber 11 The gel-like fluorosilicone is filled between the disk surface and the fluororesin sheets 163A and 163B, so that the effect of heat transfer cooling can be enhanced. Depending on the pressure between the metal plates 165A and 165B, there may be a portion where the clad 110 is in direct contact with the fluororesin sheets 163A and 163B, but even in that case, the above effect is slightly reduced.

  FIG. 3 is a plan view and a side view of the excitation light introducing member 13, the optical system 14, and the excitation light source 15. FIG. 3 (a) is a plan view, and FIG. 3 (b) is a side view. In this figure, the excitation light source 15 is an LD stack in which two LD arrays are stacked. The optical system 14 includes a first collimator 141, a second collimator 142, and a condenser lens 143. The first collimator 141 receives the excitation light output from each emitter of the LD stack as the excitation light source 15 and collimates the excitation light with respect to the fast axis. The second collimator 142 receives the excitation light output from the first collimator 141 and collimates the excitation light with respect to the slow axis. The condenser lens 143 receives the excitation light converted into parallel light by the first collimator 141 and the second collimator 142, converges the excitation light, and makes the converged excitation light incident on the excitation light introducing member 13. Incident on the surface 131.

  FIG. 4 is a side view for explaining introduction of excitation light into the optical fiber 11 by the excitation light introducing member 13. The excitation light introducing member 13 guides the excitation light input from the optical system 14 to the incident surface 131 at one end while totally reflecting the upper and lower surfaces, and the guided excitation light from the other end side to the optical fiber 11. Introduce in. The upper surface and the lower surface of the excitation light introducing member 13 are planes parallel to each other, and on the other end side (the side where the excitation light is introduced into the optical fiber 11) of the excitation light introducing member 13, an inclined surface inclined with respect to the lower surface 132 is provided. A lower surface (outgoing surface) 133 below the inclined surface 132 is optically connected to the side surface of the optical fiber 11. The inclined surface 132 forms an angle of several degrees to several tens of degrees with respect to the lower surface, has an optical polishing or a smooth surface corresponding thereto, and the excitation light that has guided the inside of the excitation light introducing member 13. Is totally reflected. Then, the emission surface 133 emits the excitation light totally reflected by the inclined surface 132 and causes the excitation light to enter the optical fiber 11.

Here, consider the excitation light traveling as shown by the dotted line in the figure. It is assumed that the excitation light travels at an angle θ 0 with respect to the emission surface 133 in the excitation light introducing member 13. An angle formed by the emission surface 133 and the inclined surface 132 is defined as θ 1 . It is assumed that excitation light travels at an angle θ 2 with respect to the optical axis in the optical fiber 11. The refractive index of the excitation light introducing member 13 is n f and the refractive index of the clad 110 of the optical fiber 11 is n clad . Further, the thickness of the excitation light introducing member 13 and D f, the diameter of the cladding 110 of the optical fiber 11 to D c. At this time, the following equation (1) is established between these parameters.

The excitation light reflected from the inclined surface 132 of the excitation light introducing member 13 and introduced into the optical fiber 11 from the emission surface 133 is reflected by the lower surface of the optical fiber 11 having a disk shape, and then the upper surface (excitation light introducing member). 13 is provided). The distance between the starting point of the inclined surface 132 of the excitation light introducing member 13 (the position closest to the incident surface 131) and the position where the excitation light reflected at the starting point first reaches the upper surface of the disk-shaped optical fiber 11. X ref is expressed by the following equation (2).

The distance L edge between the start point and the end point (position farthest from the incident surface 131) of the inclined surface 132 of the excitation light introducing member 13 is expressed by the following equation (3). Note that each of the distance X ref and the distance L edge is a distance in a direction along the optical axis of the optical fiber 11.

If the excitation light introduced into the optical fiber 11 from the excitation light introduction member 13 returns to the excitation light introduction member 13 again, the excitation light introduction efficiency is reduced. In order to prevent the excitation light from returning to the excitation light introducing member 13 as described above, it is necessary that the relationship expressed by the following expression (4) is established between the distance Xref and the distance Ledge .

  The optical device 1 configured as described above operates as follows. The excitation light output from the excitation light source 15 is collected by the optical system 14, is incident on the incident surface 131 of the excitation light introducing member 13, is guided inside the excitation light introducing member 13, and the excitation light introducing member 13 It is totally reflected by the inclined surface 132. The excitation light totally reflected by the inclined surface 132 is introduced into the optical fiber 11 through a portion where the emission surface 133 of the excitation light introducing member 13 and the side surface of the optical fiber 11 are optically connected. The excitation light introduced into the optical fiber 11 excites the laser active substance contained in the core 111 while being guided through the optical fiber 11 while being totally reflected at the outer interface of the clad 110.

  When the optical apparatus 1 does not include the reflecting member 12 and operates as an optical amplifier, when amplified light is input to one end of the core 111, the input amplified light is optically amplified while being guided through the core 111, and the light The amplified light is output from the other end. On the other hand, when the optical device 1 includes the reflecting member 12 and operates as a laser oscillator, stimulated emission is generated by the excited laser active material, and laser oscillation is performed in the resonator to output laser light.

In particular, the present embodiment is characterized in that the refractive index n f of the excitation light introducing member 13 is higher than the refractive index n clad of the clad 110 of the optical fiber 11. The angle θ 0 formed by the excitation light with respect to the emission surface 133 in the excitation light introducing member 13 is allowed as long as the above equation (4) is satisfied. That is, when the refractive index n f of the pumping light introducing member 13 is higher than the refractive index n clad of the clad 110 of the optical fiber 11, the allowable range of the angle θ 0 is widened.

  Therefore, the excitation light introducing member 13 can increase the efficiency of introducing excitation light from the excitation light source 15 to the optical fiber 11. Further, the optical fiber structure 10 and the optical device 1 using the excitation light introducing member 13 can improve the optical amplification efficiency and the laser oscillation efficiency in the optical fiber 11. Further, the positional adjustment among the excitation light introducing member 13, the optical system 14, and the excitation light source 15 is not required to be highly accurate, and these individual components are not required to be highly accurate. The fiber structure 10 or the optical device 1 can be manufactured inexpensively and easily.

In general, quartz glass has a lower melting point when impurities are added. That is, the melting point of the excitation light introducing member 13 having a high refractive index n f is lower than the melting point of the clad 110. Therefore, when the emission surface 133 of the excitation light introducing member 13 is fused and connected to the upper surface of the disk-shaped optical fiber 11, only the excitation light introducing member 13 can be softened and fused.

  Next, various modifications of the excitation light introducing member 13 will be described. FIG. 5 is a first side view showing a modification of the excitation light introducing member 13. As long as the excitation light reflected by the inclined surface 132 of the excitation light introducing member 13 passes, the emission surface 133 and the clad 110 of the optical fiber 11 need only be optically connected. At this time, as shown in FIG. 5A, the entire range where the lower surface of the excitation light introducing member 13 and the clad 110 overlap may be optically connected. However, as shown in FIG. 5B, the emission surface 133 and the clad 110 are optically connected within a range in which the excitation light reflected by the inclined surface 132 of the excitation light introducing member 13 passes. Thus, in a range where excitation light does not pass, it is preferable that a film 134 that blocks excitation light is provided between the emission surface 133 and the clad 110. By providing the excitation light blocking film 134 in this way, it is possible to suppress the excitation light introduced from one excitation light introduction member into the optical fiber 11 from being emitted through another excitation light introduction member. This makes it possible to improve excitation efficiency.

  FIG. 6 is a second side view showing a modification of the excitation light introducing member 13. As shown in FIG. 5A, the inclined surface 132 of the excitation light introducing member 13 may be a flat surface, and the tip may reach the lower surface. However, since it is actually difficult to manufacture a sharp pointed tip, the inclined surface 132 of the excitation light introducing member 13 is not sharply pointed as shown in FIG. The optical resin 135 used for connection to the optical fiber 11 may be present at the tip portion. Further, the inclined surface 132 of the excitation light introducing member 13 may be a convex surface as shown in FIG. 10C, or may be a concave surface as shown in FIG. In some cases, the lens action can be exerted on the reflected excitation light.

  FIG. 7 is a third side view showing a modification of the excitation light introducing member 13. As shown in FIG. 5A, the incident surface 131 of the excitation light introducing member 13 may be a flat surface and perpendicular to the lower surface. However, as shown in FIG. 5B, it is preferable that the incident surface 131 of the excitation light introducing member 13 is a flat surface and not perpendicular to the lower surface. In this case, the excitation light reflected by the incident surface 131 is suppressed from returning to the excitation light source 15, and a stable excitation light output can be obtained. Further, as shown in FIG. 5B, the incident surface 131 of the excitation light introducing member 13 is a convex surface, and it is also preferable that it has a lens action.

  FIG. 8 is a plan view showing a modification of the excitation light introducing member 13. The excitation light introducing member 13 may have a constant width as shown in FIG. 9A, or the width becomes narrower from the incident surface 131 toward the inclined surface 132 as shown in FIG. It may be. In the latter case, a large number of linear bodies can be optically connected to the incident surface 131 as shown in FIG. 9 later, and high-power excitation light can be introduced into the optical fiber 11 at a high density. it can.

  FIG. 9 is a plan view and a side view showing a modification of the excitation light introducing member 13. The excitation light introducing member that has been described so far consists of an approximately flat plate-like introduction plate 13A having an incident surface 131, an inclined surface 132, and an exit surface 133. However, the excitation light introducing member 13 shown in the figure further includes a plurality (five in the figure) of linear bodies 13B in addition to the approximately flat introducing plate 13A. In this case, the optical system 14 may be omitted.

  Each linear body 13B preferably has flexibility. Each linear body 13B has an incident end 136 that receives the excitation light output from the excitation light source, and an emission end 137 that emits the excitation light incident on the incident end 136 and guided inside. The exit end 137 of each linear body 13B is optically connected to the incident surface 131 of the introduction plate 13A. Each linear body 13B may have a uniform refractive index, or may be an optical fiber having a core in the cladding. In the latter case, each linear body 13B may be an individual optical fiber constituting the optical fiber array, or may be a pigtail optical fiber attached to the LD as the excitation light source 15. .

  Thus, when the excitation light introducing member 13 includes the introduction plate 13A and the plurality of linear bodies 13B, not only can the power of the excitation light introduced into the optical fiber 11 be increased, but also the following effects can be obtained. is there. That is, the connection between the plurality of linear bodies 13B arranged in an array and the introduction plate 13A can be easily made by fusion splicing that has a proven record in the optical communication field. Further, as shown in the side view of FIG. 10, the excitation light introducing member 13 is sandwiched between the metal plates 139A and 139B via the resins 138A and 138B, so that highly efficient cooling can be performed. It is easy to make it stronger. Further, since the fabrication is easy and precise position adjustment and tilt adjustment are possible, the deterioration of the beam quality of the excitation light merged by the introduction plate 13A from the plurality of linear bodies 13B is small.

  If each linear body 13B has flexibility, the arrangement of LDs as excitation light sources connected to the incident end 136 of the linear body 13B can be arbitrarily set, and a chip LD is used as the excitation light source. Therefore, it is possible to cool the LD by air cooling. About each linear body 13B, since a diameter can be made small, it is preferable also at the point of heat dissipation. Since the arrangement of the LDs can be made arbitrary, the LDs can be aggregated on the board, and the deteriorated LD can be easily replaced. Misalignment hardly occurs. Even if the disk-shaped optical fiber structure 10 is thinned, it is possible to increase the degree of integration of pumping light and increase the output, and to easily improve the beam quality.

  (Second Embodiment)

  Next, a second embodiment of the optical fiber structure and the optical device according to the present invention will be described. FIG. 11 is a perspective view of the optical device 2 according to the second embodiment. The optical device 2 shown in this figure is provided with a cylindrical cooling member 29, an optical fiber 21 that is densely spirally wound around the cooling member 29 to form a cylinder, and one end of the optical fiber 21. A reflection member 22, an excitation light introducing member 23 for introducing excitation light into the optical fiber 21, an optical system 24 for causing the excitation light to enter the excitation light introducing member 23, and an excitation light source 25 for outputting the excitation light. Among these, the cooling member 29, the optical fiber 21, the reflecting member 22, and the excitation light introducing member 23 constitute an optical fiber structure 20. The optical fiber 21 has the same configuration as the optical fiber 11 in the first embodiment and is manufactured in the same manner.

  In the optical fiber structure 20, the optical fiber 21 is densely wound in a spiral shape and has a cylindrical shape. At the time of this ticket turning, at least a part of the optical fiber 21 is laminated in the radial direction to have a cylinder shape. The optical fiber 21 does not need to be laminated in the radial direction of the cylinder shape. In this wound state, adjacent clads may be optically connected by fusion or optical resin, but more preferably polysilazane is used as an adhesive and optically connected.

  Both end surfaces of the optical fiber 21 may be polished flat. In this case, the optical fiber structure 20 is preferably used as an optical amplification medium in an optical amplifier. That is, the amplified light that has entered the core from one end face is optically amplified in the core, and the light amplified light is emitted from the other end face. At this time, it is also preferable that a reflection reducing film is provided on both end faces. In addition, a configuration in which a fiber Bragg grating (FBG) having a reflectance of 10% or less is provided in the vicinity of an end face from which laser light is emitted, and the end face itself is polished obliquely is also preferable.

  As shown in FIG. 11, a reflection member 22 that reflects light emitted from the laser active substance contained in the core of the optical fiber 21 may be provided on one end face. In this case, the other end face and the reflecting member 22 constitute an optical resonator, and the optical fiber structure 20 is suitably used as an optical amplification medium in a laser oscillator. At this time, it is also preferable that a reflection reducing film is provided on the other end surface (surface from which the laser beam is emitted). As the reflecting member 22, an external mirror, a dielectric multilayer film mirror attached to an end face, an optical fiber grating, or the like is preferably used.

  The cooling member 29 is made of metal and is used for cooling the optical fiber 21. It is preferable that a hole for flowing circulating cooling water is provided inside the cooling member 29. The cooling member 29 is in direct or indirect contact with the optical fiber 21 wound in a cylinder shape and absorbs heat of the optical fiber 21 generated by absorption of excitation light. Further, it is also preferable that a low refractive index resin (for example, fluorosilicone) is provided between the cooling member 29 and the optical fiber 21, and in this way, excitation light is generated at the interface between the resin and the clad. Is totally reflected, so that absorption of excitation light is prevented by the cooling member 29 and heat transfer between the cooling member 29 and the clad is improved, so that the cooling effect is increased.

  The excitation light introducing member 23, the optical system 24, and the excitation light source 25 in the second embodiment are the same as the excitation light introducing member 13, the optical system 14, and the excitation light source 15 in the first embodiment as shown in FIGS. It is the same thing. The pumping light introducing member 23 is made of a material having a small absorption at the pumping light wavelength, and is preferably synthetic quartz glass, or may be multicomponent glass, and more preferably, the clad of the optical fiber 21 is refracted. Has a refractive index higher than the refractive index. For example, the cladding of the optical fiber 21 is made of pure quartz glass, whereas the excitation light introducing member 23 is made of quartz glass to which an impurity as a refractive index increasing material is added. Moreover, it is preferable that the excitation light introducing member 23 is provided so that the excitation light after introduction propagates in the extending direction of the core. The excitation light introducing member 23 may have a configuration as shown in FIGS.

  FIG. 12 is a partial cross-sectional view of the optical fiber structure 20 according to the second embodiment. As shown in this figure, in the optical fiber structure 20, an optical fiber 21 including a core 211 is clad into a clad 210 and spirally wound into a cylinder shape, and the cylinder-shaped optical fiber is formed. The clad 210 of the 21 is bonded by the polysilazane 261, and the gel-like fluorosilicone 262, the fluororesin sheet 262, and the heat conductive sheet 264 are sequentially disposed between the cylindrical optical fiber 21 and the cooling member 29. Is provided.

  The polysilazane 261 is provided as an adhesive between the adjacent clads 210 when the optical fiber 21 is wound. Here, the polysilazane 261 provided as an adhesive between the clads 210 may be converted or may not be converted. Thus, between the optical fiber 21 in which the clads 210 are connected by the polysilazane 261 and formed into a cylinder shape, and the cooling member 29 that cools the optical fiber 21, the gel-like fluorosilicone 262, the fluororesin sheet 262, and A heat conductive sheet 264 is provided in order. The gel-like fluorosilicone 262, the fluororesin sheet 262, and the heat conductive sheet 264 all have high thermal conductivity. Further, both the fluororesin sheet 262 and the heat conductive sheet 264 are excellent in flexibility.

  The optical device 2 according to the present embodiment configured as described above operates in the same manner as the optical device 1 according to the first embodiment, and can achieve the same effects.

  (Third embodiment)

  Next, a third embodiment of the optical fiber structure and the optical device according to the present invention will be described. FIG. 13 is a perspective view of the optical device 3 according to the third embodiment. The optical device 3 shown in this figure includes a substantially disc-shaped cooling member 39, an optical fiber 31 wound around the cooling member 39, a reflecting member 32 provided at one end of the optical fiber 31, and the optical fiber 31. Are provided with an excitation light introducing member 33 that introduces excitation light, and an excitation light source (not shown) that outputs the excitation light. Among these, the cooling member 39, the optical fiber 31, the reflecting member 32, and the excitation light introducing member 33 constitute an optical fiber structure 30. The optical fiber 31 has the same configuration as the optical fiber 11 in the first embodiment and is manufactured in the same manner.

  In the optical fiber structure 30, the optical fiber 31 is wound around the side surface of the cooling member 38. The optical fibers 31 need not be laminated in the radial direction. In this optical fiber 31, the adjacent clads are optically connected in some areas 31A, but the individual clads are separated from each other in the other areas 31B. The adjacent clads in the region 31A may be optically connected by fusion or optical resin, but more preferably, polysilazane is used as an adhesive and optically connected. In the region 31B where the clads are separated from each other, a resin or the like is coated around the clad made of quartz glass. The refractive index of the resin around the clad is lower than the refractive index of the clad, and these preferably form a double clad structure.

  Both end faces of the optical fiber 31 may be polished flat. In this case, the optical fiber structure 30 is preferably used as an optical amplification medium in the optical amplifier. That is, the amplified light that has entered the core from one end face is optically amplified in the core, and the light amplified light is emitted from the other end face. At this time, it is also preferable that a reflection reducing film is provided on both end faces.

  As shown in FIG. 13, a reflection member 32 that reflects light emitted from the laser active substance contained in the core of the optical fiber 31 may be provided on one end face. In this case, the other end face and the reflecting member 32 constitute an optical resonator, and the optical fiber structure 30 is suitably used as an optical amplification medium in the laser oscillator. At this time, it is also preferable that a reflection reducing film is provided on the other end surface (surface from which the laser beam is emitted). In addition, a configuration in which a fiber Bragg grating (FBG) having a reflectance of 10% or less is provided in the vicinity of an end face from which laser light is emitted, and the end face itself is polished obliquely is also preferable. As the reflecting member 32, an external mirror, a dielectric multilayer film mirror attached to an end face, an optical fiber grating, or the like is preferably used.

  The cooling member 39 is made of a metal and is for cooling the optical fiber 31. The cooling member 39 is preferably provided with holes for circulating circulating cooling water, and a plurality of through holes 39A are provided for air cooling as shown in FIG. preferable. Each of the plurality of through-holes 39A has a rectangular shape that is long in one direction, each long side is parallel to each other, and the space between adjacent through-holes 39A is thin. The cooling member 39 is in direct or indirect contact with the optical fiber 31 and absorbs heat of the optical fiber 31 generated by absorption of excitation light. In addition, it is preferable that a low refractive index resin (for example, fluorosilicone) is provided between the cooling member 39 and the optical fiber 31. By doing so, excitation light is generated at the interface between the resin and the clad. Is totally reflected, so that absorption of excitation light is prevented by the cooling member 39 and heat transfer between the cooling member 39 and the cladding is improved, so that the cooling effect is increased.

  The excitation light introducing member 33, the optical system, and the excitation light source in the third embodiment are the same as the excitation light introducing member 13, the optical system 14, and the excitation light source 15 in the first embodiment as shown in FIGS. It may be a thing. The excitation light introducing member 33 is made of a material that absorbs less light at the excitation light wavelength, and is preferably synthetic quartz glass, or may be multicomponent glass, and more preferably, the clad of the optical fiber 31 is refracted. Has a refractive index higher than the refractive index. For example, the cladding of the optical fiber 31 is made of pure quartz glass, whereas the excitation light introducing member 33 is made of quartz glass to which an impurity as a refractive index increasing material is added. Moreover, it is preferable that the excitation light introducing member 33 is provided so that the excitation light after introduction propagates in the extending direction of the core. The excitation light introducing member 33 may be configured as shown in FIGS.

  In the present embodiment, the exit surface of the excitation light introducing member 33 (the surface from which the excitation light introduced into the optical fiber 31 is emitted) is optically connected between adjacent clads in the optical fiber 31 that is wound. Connected to the region 31A. Further, in particular, the excitation light introducing member 33 shown in FIG. 13 has a configuration including a substantially flat introducing plate 33A and a plurality of linear bodies 33B as shown in FIGS. . Further, the cross-sectional structure of the optical fiber structure 30 in the region 31A where the adjacent clads are optically connected is the same as that shown in FIG.

  The optical device 3 according to this embodiment configured as described above operates in the same manner as the optical device 1 according to the first embodiment, and can provide the same effects. In addition, the optical device 3 according to the present embodiment can exhibit the following operations and effects. In the region 31A of the optical fiber 31 into which the pumping light is introduced from the pumping light introducing member 33, the adjacent cladding is optically connected, so that the pumping light introduction efficiency is increased. On the other hand, in the other region 31B of the optical fiber 31, the individual clads are separated from each other, which is advantageous in terms of heat dissipation.

  In addition, the optical device 3 can be easily manufactured, and the diameter of the optical fiber can be reduced. Therefore, the optical fiber can be accommodated in a compact manner, and this is also advantageous for heat dissipation. Since this optical device 3 has a small pumping light propagation loss in the optical fiber 31, the pumping light absorption length can be increased and it is easy to make a single mode. In the optical device 3, the optical fiber 31 can be handled in various ways in the region 31 </ b> B that is a double clad, and therefore it is easy to suppress higher-order modes due to bending.

1 is a plan view of an optical device 1 according to a first embodiment. 1 is a partial cross-sectional view of an optical fiber structure 10 according to a first embodiment. 2 is a plan view and a side view of the excitation light introducing member 13, the optical system 14, and the excitation light source 15. FIG. It is a side view explaining excitation light introduction to the optical fiber 11 by the excitation light introducing member 13. 6 is a first side view showing a modification of the excitation light introducing member 13. FIG. FIG. 10 is a second side view showing a modification of the excitation light introducing member 13. FIG. 10 is a third side view showing a modification of the excitation light introducing member 13. 6 is a plan view showing a modification of the excitation light introducing member 13. FIG. It is the top view and side view which show the modification of the excitation light introduction member 13. 6 is a side view showing a modification of the excitation light introducing member 13. FIG. It is a perspective view of the optical apparatus 2 which concerns on 2nd Embodiment. It is a partial cross section figure of the optical fiber structure 20 which concerns on 2nd Embodiment. It is a perspective view of the optical apparatus 3 which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1-3 ... Optical apparatus, 10 ... Optical fiber structure, 11 ... Optical fiber, 12 ... Reflection member, 13 ... Excitation light introducing member, 14 ... Optical system, 15 ... Excitation light source, 20 ... Optical fiber structure, 21 ... Optical fiber, 22 ... Reflecting member, 23 ... Excitation light introducing member, 24 ... Optical system, 25 ... Excitation light source, 29 ... Cooling member, 30 ... Optical fiber structure, 31 ... Optical fiber, 32 ... Reflecting member, 33 ... Excitation Light introducing member, 39 ... cooling member.

Claims (4)

  1. A pumping light introducing member for introducing pumping light into the optical fiber from the side surface of the optical fiber including a core containing a laser active substance in the cladding,
    An incident surface on which the excitation light is incident, an inclined surface that totally reflects the excitation light that is incident on the incident surface and guided inside, and the excitation light that is totally reflected by the inclined surface is emitted into the optical fiber. An introduction plate having an exit surface for incidence;
    The refractive index of the introduction plate is higher than the refractive index of the cladding of the optical fiber,
    An excitation light introducing member.
  2. A plurality of linear bodies each having an incident end for incident excitation light and an output end for emitting excitation light incident on the incident end and guided inside;
    The exit ends of the plurality of linear bodies are optically connected to the entrance surface of the introduction plate,
    The excitation light introducing member according to claim 1.
  3.   An optical fiber including a core containing a laser active substance in a clad, and an excitation light introducing member according to claim 1 or 2 for introducing excitation light into the optical fiber from a side surface of the optical fiber. An optical fiber structure.
  4. An optical apparatus comprising: the optical fiber structure according to claim 3; and an excitation light source that outputs excitation light to be introduced into an optical fiber included in the optical fiber structure.

JP2005350983A 2005-12-05 2005-12-05 Excitation light guide member, optical fiber structure and optical device Pending JP2007158012A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Application Number Priority Date Filing Date Title
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