JP2008077003A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module which prevents loss of signal light. <P>SOLUTION: The optical module 1A is equipped with: a bar laser 2 for emitting signal light Cs; a visible light laser 3 for emitting visible guide light Cg; a first optical element group 5 which guides the signal light Cs emitted from the bar laser 2 to an optical fiber 4, condenses the signal light Cs through a focus lens 50 to couple the signal light to the optical fiber 4; and a second optical element group 6 which reflects the guide light Cg emitted from the visible laser 3 by a reflecting mirror 61A, guides the guide light Cg to the optical fiber 4 through a separate optical path parallel to the optical path of the signal light Cs to couple the guide light Cg to the optical fiber 4 through the focus lens 50. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical module that couples signal light and guide light by visible light to an optical fiber. Specifically, the loss of the signal light is prevented by guiding the signal light and the guide light through separate optical paths and coupling them to the optical fiber.

  As an optical module that couples laser light emitted from a semiconductor laser to an optical fiber, a fiber-coupled module equipped with a high-power semiconductor laser having a high output of several tens of watts (W) or more has recently been solid-state pumped, plastic It is used as a light source for welding and soldering.

  The fiber couple module has advantages in that the beam profile of the laser beam emitted from the optical fiber is isotropic and that the laser beam can be irradiated to a desired location by the optical fiber, as compared with the semiconductor laser alone. Due to these advantages, the fiber couple module can be applied to applications that cannot be applied by a single semiconductor laser, thereby expanding the application field of high-power semiconductor lasers.

  Now, the high-power semiconductor laser mounted on such a fiber coupled module has a wavelength region in the near infrared region and cannot be recognized by human eyes. Therefore, it is impossible to confirm the spot position where the laser beam is irradiated by human eyes.

  On the other hand, among applications to which the fiber couple module is applied, there is often a demand for visually recognizing that an object is irradiated with laser light. In order to solve such a problem, a module for coupling visible laser light such as red to the same optical fiber as the near-infrared signal light has been developed.

  As a method for coupling light of different wavelengths to the same optical fiber, a technique has been proposed in which wavelength selection means is provided in the optical path, and light of different wavelengths is combined and coupled to the optical fiber (for example, Patent Documents). 1).

  As a method of coupling the signal light and the guide light to the same optical fiber, a technique of combining them using a dichroic mirror having a wavelength dispersion in reflectance is common.

  FIG. 8 is a block diagram showing an example of a conventional optical module using a dichroic mirror. In the conventional optical module 100, a dichroic mirror 101 is disposed in the optical path of the signal light Cs. The near-infrared signal light Cs and the guide light Cg that is visible light are perpendicular to each other's light. Is incident on. In this case, the dichroic mirror 101 has a high transmittance with respect to the signal light Cs, almost all light passes through the dichroic mirror 101, and has a high reflectance with respect to the guide light Cg, so that almost all light is dichroic. Reflected by the mirror 101.

  The dichroic mirror 101 is arranged so that the optical axes of the combined light coincide with each other, and the guide light Cs and the signal light Cg combined by the dichroic mirror 101 are collected by the focus lens 102 and coupled to the optical fiber 103. To do.

  In the element structure of the dichroic mirror 101, a dielectric multilayer film is used as a reflection film. If the number of dielectric multilayer films is increased, the transmittance can be made close to 1 for light of a predetermined wavelength. If the transmittance of the dichroic mirror 101 is 1 with respect to the signal light Cs, the signal light Cs is not lost by the dichroic mirror 101.

  However, it is impossible to make the transmittance of the dichroic mirror 101 completely 1, and absorption and reflection components of several percent occur. Therefore, the multiplexing using the dichroic mirror causes a loss in the signal light Cs. The amount of loss of signal light is several watts for signal light of several hundred watts when the semiconductor laser has a high output.

  Further, the loss of the signal light Cs is absorbed by the dichroic mirror 101, or reflected and scattered, confined in the module, and finally absorbed by the casing and internal elements. Thereby, the energy generated by the loss of signal light becomes a heat source.

Japanese Patent Laying-Open No. 2005-140960 (FIG. 2)

  In a conventional optical module in which a wavelength selection optical element such as a dichroic mirror is arranged in the optical path of the signal light to combine the signal light and the guide light, loss occurs in the signal light, and the intensity of the signal light is reduced.

  Further, the loss of the signal light is absorbed by the wavelength selection optical element or is repeatedly scattered in the module. When a semiconductor laser of several hundred W class is used, even if the loss is several percent, it becomes energy of several W, and the energy of the loss becomes a wavelength selection optical element or a heat generation source inside the module, so that the reliability of the module is lowered.

  Furthermore, a wavelength selection optical element such as a dichroic mirror that multiplexes light having different wavelengths is an element that has wavelength dispersion in reflectance (transmittance) by a dielectric multilayer film, and is a relatively expensive optical element. For this reason, product cost rises.

  The present invention has been made to solve such a problem, and an object thereof is to provide an optical module that prevents loss of signal light.

  In order to solve the above-described problems, an optical module of the present invention is emitted from a first light emitting unit that emits signal light, a second light emitting unit that emits visible light guide light, and a first light emitting unit. The guide light emitted from the first light guiding means for guiding the signal light to the optical fiber and coupling the signal light to the optical fiber and the second light emitting means are guided to the optical fiber by a separate optical path from the signal light. And second light guiding means for coupling the guide light to the optical fiber.

  In the optical module of the present invention, the signal light emitted from the first light emitting means is guided to the optical fiber by the first light guiding means and coupled to the optical fiber. The guide light emitted from the second light emitting means is guided to the optical fiber by an optical path different from the signal light by the second light guiding means, and is coupled to the same optical fiber to which the signal light is coupled.

  The signal light and the guide light coupled to the optical fiber are propagated through the optical fiber, emitted from the optical fiber, and irradiate the object. The signal light and the guide light emitted from the optical fiber irradiate the same position.

  Since the guide light is visible light, the irradiation position of the signal light can be visually recognized at the irradiation position of the guide light even if the signal light is invisible light.

  According to the optical module of the present invention, since the guide light is guided to the optical fiber by an optical path different from the signal light, an optical element for multiplexing the guide light is not necessary in the optical path of the signal light, and the signal light is lost. Can be prevented. Therefore, the intensity of the signal light is not reduced by introducing the guide light.

  In addition, since loss of signal light can be prevented, energy associated with the loss of light is not generated inside the module, and high reliability can be obtained.

  Furthermore, since the optical path of the guide light can be formed using a reflection mirror or the like, an increase in cost can be suppressed.

  Hereinafter, embodiments of the optical module of the present invention will be described with reference to the drawings.

<Configuration example of optical module of this embodiment>
FIG. 1 is a configuration diagram illustrating an example of an optical module according to the present embodiment. FIG. 1A is a plan view of the optical module 1A according to the present embodiment, and FIG. 1B is a side view of the optical module 1A. FIG.

  The optical module 1A of the present embodiment includes a bar laser 2 that emits signal light Cs, a visible laser 3 that emits guide light Cg, and a first light that couples the signal light Cs emitted from the bar laser 2 to the optical fiber 4. An optical element group 5 and a second optical element group 6 for coupling the guide light Cg emitted from the visible laser 3 to the optical fiber 4 through an optical path different from the signal light Cs are provided.

  In a coupling method referred to as a separate optical path method in which the signal light Cs and the guide light Cg are coupled to the same optical fiber 4 by separate optical paths, the first optical element group 5 required for coupling the signal light Cs to the optical fiber 4 is used. On the other hand, since an optical element that adds a new function such as a dichroic mirror is not used, no loss occurs in the signal light Cs by introducing the guide light Cg. Therefore, a decrease in reliability due to loss is also prevented.

  As another optical path method, the following two methods can be considered. 2 and 3 are explanatory diagrams showing the concept of another optical path method in which signal light and guide light are different optical paths. The separate optical path method shown in FIG. 2 spatially separates the optical paths of the signal light Cs and the guide light Cg in parallel as shown in FIG. Then, the signal light Cs and the guide light Cg, which are spatially separated and separated from each other, are incident on the focus lens 50 and coupled to the optical fiber 4.

  As described above, another optical path method in which the signal light Cs and the guide light Cg are spatially separated to form separate optical paths is referred to as a spatial separate optical path method. FIG. 2B shows a beam image of two lights at the fiber entrance end in the spatial separate optical path method. The optical fiber 4 includes a core 40, a clad 41 that covers the core 40, and a covering material 42 that covers the clad 41. In the spatial separate optical path method, the beam spot of the signal light Cs at the incident end 43 of the optical fiber 4. The coupling center position of Bs and the coupling center position of the beam spot Bg of the guide light Cg are the same, which is an optical multiplexing system called angle multiplexing.

  In the separate optical path method shown in FIG. 3, as shown in FIG. 3A, the radiation directions of the signal light Cs and the guide light Cg are slightly shifted so as to be angularly separate optical paths. Then, the signal light Cs and the guide light Cg having different optical paths are incident on the focus lens 50 and coupled to the optical fiber 4.

  As described above, the separate optical path method in which the signal light Cs and the guide light Cg are angularly separated to form separate optical paths is referred to as an angular separate optical path method. FIG. 3B shows a beam image of two lights at the fiber entrance end in the angularly different optical path method. In the angular separate optical path method, the coupling center position of the beam spot Bs of the signal light Cs at the incident end 40 of the optical fiber 4 is shifted from the coupling center position of the beam spot Bg of the guide light Cg, and an optical multiplexing method called position multiplexing is used. Become.

  Next, the details of the optical module to which the spatial separate optical path method is applied will be described with reference to FIG. The bar laser 2 is an example of first light emitting means, and is a light emitting device in which, for example, about 20 emitters (not shown) are arranged in the slow (horizontal) direction of a laser diode (LD), and is mounted on a heat sink or the like to constitute a bar LD package. . In the configuration in which about 20 emitters are arranged, the entire width of the bar laser 2 is about 10 mm.

  The laser light emitted from the bar laser 2 generally has a wavelength of near 800 to 1000 nm in the near infrared, and in particular, the 900 nm band is almost completely invisible. For this reason, when the laser light emitted from the bar laser 2 is used as signal light, the necessity for visible guide light is high.

  The visible laser 3 is an example of a second light emitting means, and a lateral single mode LD of several tens of mW class is useful, and the wavelength may be any visible.

  The optical fiber 4 is configured such that the refractive index of the core 40 is slightly larger than the refractive index of the cladding 41, and light coupled to the core 40 is confined in the core 40 and propagated. Further, the refractive index of the clad 41 is configured to be slightly larger than the refractive index of the covering material 42, and the light coupled to the clad 41 is confined in the clad 41 and propagated. As the optical fiber 4, one having a core diameter of 100 to 600 μm and an NA (numerical aperture) of about 0.2 is usually used.

  The first optical element group 5 is an example of a first light guide unit, and includes a focus lens 50, a FAC (fast axis collimating) lens 51, a beam shaper 52A, and a collimator lens 53.

  The FAC lens 51 is an element that narrows the radiation angle in the fast (vertical) direction of the signal light Cs radiated from the bar laser 2 to make it parallel light. The FAC lens 51 is usually a rod lens having a focal length of about 1 mm, and is mounted on the bar LD package of the bar laser 2 by bonding or the like.

  The beam shaper 52A is called an optical path changing device or the like, and is an element that makes the beam quality of the signal light Cs emitted from the bar laser 2 in the fast direction and the slow direction isotropic. From the bar laser 2, for example, signal light is emitted in an extremely flat emission pattern in which the slow direction is 100 μm to 300 μm and the fast direction is 1 μm or less. The beam shaper 52A is an element that divides such flat signal light in the slow direction and stacks it in the fast direction, thereby condensing it in a narrow area. For example, the beam shaper 52A uses light reflection twice or by refraction. A device that swaps the fast direction and the slow direction is commercially available. The material of the beam shaper 51 is glass or metal.

  The collimating lens 53 is an element that collimates the slow direction of the signal light Cs isotropicized by the beam shaper 52A. For example, a cylindrical lens is used.

  The focus lens 50 is an example of a condensing unit, and is an element that condenses the signal light Cs collimated by the collimating lens 53 onto the optical fiber 4, and a glass material lens having a focal length of about several tens mm is useful.

  The second optical element group 6 is an example of a second light guide means, and includes a collimator lens 60 and a reflection mirror 61A. The collimating lens 60 is an element that narrows the radiation angle in the fast direction of the guide light Cg emitted from the visible laser 3 to make it parallel light, and a lens having a focal length of about several millimeters is used.

  The reflection mirror 61A is an example of a reflection unit, and is an element that makes the optical path of the guide light Cg collimated by the collimator lens 60 parallel to the optical path of the signal light Cs and enters the focus lens 53, and serves as a laser mirror. Common materials such as aluminum (Al) and gold (Au) are used.

  The reflection mirror 61A is installed outside the optical path of the signal light Cs at 45 degrees in this example with respect to the optical path of the signal light Cs, and reflects the guide light Cg emitted in the direction perpendicular to the signal light Cs to reflect the optical path. Is converted by 90 degrees to make the optical path of the guide light Cg parallel to the optical path of the signal light Cs.

  The guide light Cg having the optical path parallel to the signal light Cs is incident on the focus lens 50 and is condensed on the optical fiber 4 through an optical path different from the signal light Cs. The reflecting means may be a refractive element such as a prism.

  In the optical module 1A, a bar laser 2, a visible laser 3, a first optical element group 5, a second optical element group 6, and the like are mounted in a package (not shown), and an optical fiber 4 is connected to form a module.

<Modification of Optical Module of this Embodiment>
4A and 4B are configuration diagrams showing a modification of the optical module of the present embodiment. FIG. 4A is a plan view of the optical module 1B of the modification, and FIG. 4B is a side view of the optical module 1B. It is. Note that parts having the same configuration as those of the optical module 1A shown in FIG.

  The optical module 1B according to the modification includes a beam shaper 52B that converts the optical path by 90 degrees using reflection, and isotropically qualifies the beam quality of the signal light Cs emitted from the bar laser 2 in the fast direction and the slow direction. Further, a reflection mirror 61B is provided that makes the reflection angle of the guide light Cg emitted from the visible laser 3 an acute angle and makes the signal light Cs and the guide light Cg parallel.

  As described above, the reflection mirror may have any position and angle as long as the optical paths of the signal light Cs and the guide light Cg are parallel after reflection. In addition, the angular separate optical path method can also be realized with an equivalent optical element arrangement.

<Operation example of optical module of this embodiment>
Next, an operation example of the optical module according to the present embodiment will be described. When the signal light Cs emitted from the bar laser 2 passes through the FAC lens 51, the radiation angle in the fast direction is narrowed to be collimated.

  When the signal light Cs collimated by the FAC lens 51 passes through the beam shaper 52A, the beam quality in the fast direction and the slow direction is made isotropic. When the signal light Cs isotropicized by the beam shaper 52A passes through the collimator lens 53, the radiation angle in the slow direction is narrowed to be collimated. The signal light Cs that has been collimated by the collimator lens 53 passes through the focus lens 50 and is condensed on the incident end of the optical fiber 4.

  Then, the signal light Cs collected at the incident end of the optical fiber 4 enters the core 40 of the optical fiber 4, propagates through the core 40, exits from an output end (not shown) of the optical fiber 4, and Irradiate.

  On the other hand, when the guide light Cg radiated from the visible laser 3 passes through the collimating lens 60, the radiation angles in the fast direction and the slow direction are narrowed to be collimated.

  The guide light Cg that has been collimated by the collimator lens 60 is reflected by the reflection mirror 61A, so that the optical path is made parallel to the signal light Cs in a different optical path from the signal light Cs. The guide light Cg whose optical path is parallel to the signal light Cs by the reflection mirror 61A is incident on the focus lens 53 and passes through the focus lens 53, and is condensed on the incident end of the optical fiber 4 along an optical path different from the signal light Cs. Is done.

  The guide light Cg collected at the incident end of the optical fiber 4 is incident on the clad 41 of the optical fiber 4 in this example, propagated through the clad 41, and emitted from an unillustrated exit end of the optical fiber 4. And irradiate the object.

  The signal light Cs emitted from the emission end (not shown) of the optical fiber 4 has a wavelength in the near infrared and is almost invisible. On the other hand, the guide light Cg emitted from the emission end (not shown) of the optical fiber 4 is visible because it has a wavelength in the visible region. Therefore, the irradiation position of the signal light Cs can be visually confirmed.

<Examples of effects of propagating guide light in clad mode>
In the optical module 1A of the present embodiment, when the signal light Cs and the guide light Cg are coupled to the optical fiber 4 by another optical path method using different optical paths, the guide light Cg is preferably propagated in a clad mode. Next, the reason why the guide light Cg is propagated in the clad mode will be described.

FIG. 5 is an operation explanatory view showing the principle of coupling light to the core of the optical fiber. Normally, the coupling of light to the optical fiber 4 is performed by confining the size (spot diameter) of the beam C at the incident end 43 of the optical fiber 4 as shown in FIG. The angle at which the incident angle θ of the beam C to the optical fiber 4 is smaller than the diameter of the core 40 and falls within the allowable incidence angle θ _NA corresponding to the NA of the optical fiber 4 as shown in FIG. Connect with.

  In the signal light Cs, in order to couple as much light as possible to the optical fiber 4, the area of the core 40 at the incident end 43 of the optical fiber 4 and the almost whole area of the NA are used for coupling to increase the luminance. It is desirable.

  Therefore, when the guide light Cg is coupled to the optical fiber 4 by another optical path method, it is desirable that the space and the angle to the core 40 are left for the signal light Cs and coupled to the cladding mode.

  FIG. 6 is an explanatory diagram showing the relationship between the focal length of the focus lens, the beam position, and the incident angle to the optical fiber. A specific method for coupling the guide light Cg to the cladding mode by another optical path method will be described next.

  In the spatial separate optical path method in which the optical path of the signal light Cs and the optical path of the guide light Cg are made parallel to enter the focus lens 50 and focused on the optical fiber 4, the guide light Cg is incident at an incident angle of NA or more. Coupled to fiber 4. The numerical calculation for that will be described. The incident angle θ to the optical fiber 4 is such that the beam position of the signal light Cs incident on the focus lens 50 from the optical axis center of the optical fiber 4 is Ys, the beam position of the guide light Cg is Yg, and the focal length of the focus lens 50 is If it is set to f, it will represent like the following (1) Formula.

  tan θ = Y / f (1)

In the optical fiber 4, the NA of the core mode is determined by the refractive index difference between the materials constituting the core 40 and the clad 41. In general, the material constituting the core 40 and the clad 41 is glass, the refractive index is about 1.5 to 1.6, the refractive index difference Δn is about 0.01, and the NA is 0.2. When NA (= sin θ _NA ) is 0.2, tan θ _NA is 0.204, so that the signal light Cs propagates in the core mode using the beam position Ys of the signal light Cs (2 ) Is satisfied.

  0.204 ≧ Ys / f (2)

  On the other hand, the NA of the cladding mode is determined by the refractive index of the material of the cladding 41 and the covering material 42 on the outside thereof. The material of the covering material 42 that covers the clad 41 is generally silicon resin, polyamide resin, or the like, and its refractive index is about 1.4 to 1.5, and NA is about 0.3. Therefore, in order to propagate the guide light Cg in the clad mode, the following equation (3) may be satisfied using the beam position Yg of the guide light Cg.

  0.3 ≧ Yg / f ≧ 0.204 (3)

  By selecting the focal length f of the focus lens 50 and the beam position Y incident on the focus lens 50 according to the above calculation method, the coupling of the guide light Cg to the cladding mode can be realized.

  Also in the angular separate optical path method, the coupling of the guide light to the clad mode can be realized by selecting the focal length of the focus lens and the shift amount of the incident angle to the focus lens.

  FIG. 7 is an explanatory diagram showing a beam profile at the exit end of the optical fiber, FIG. 7A shows the light intensity in the core mode at the exit end 44 of the optical fiber 4, and FIG. The light intensity in the clad mode is shown.

  As shown in FIG. 7A, in the core mode, the beam is emitted with the diameter W1 of the core 40, and as shown in FIG. 7B, the beam is emitted with the diameter W2 of the clad 41. Therefore, the beam diameter is different between the core mode and the clad mode. On the other hand, the beam center position Os in the clad mode and the beam center position Og in the clad mode are the same if the center positions of the core 40 and the clad 41 are the same.

  When the light emitted from the optical fiber 4 is condensed on the object, the guide light Cg performs a visual recognition function if it has the same center position as the signal light Cs. As a result, even if the guide light Cg is in the clad mode, the center position of the guide light Cg is the same as the center position of the signal light Cs, so that the function as the guide light is sufficiently achieved.

  The present invention can be used as a heat source of a film forming apparatus such as a crystal growth apparatus. Moreover, it is applicable also to a medical use. In the case of medical use, a visible red laser may be used as signal light. However, when the tissue of the human body that is the target is red, it is difficult to visually recognize the signal light. For this reason, the signal light is not limited to invisible infrared light, and visible light having a color different from that of the object may be used as the guide light, even if it is visible light or ultraviolet light. For example, in medical applications, a green laser may be used as guide light.

It is a block diagram which shows an example of the optical module of this Embodiment. It is explanatory drawing which shows the concept of the different optical path method which made signal light and guide light into another optical path. It is explanatory drawing which shows the concept of the different optical path method which made signal light and guide light into another optical path. It is a block diagram which shows the modification of the optical module of this Embodiment. It is operation | movement explanatory drawing which shows the coupling principle of the light to the core of an optical fiber. It is explanatory drawing which shows the relationship between the focal distance of a focus lens, a beam position, and the incident angle to an optical fiber. It is explanatory drawing which shows the beam profile in the output end of an optical fiber. It is a block diagram which shows an example of the conventional optical module using a dichroic mirror.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A, 1B ... Optical module, 2 ... Bar laser, 3 ... Visible laser, 4 ... Optical fiber, 5 ... 1st optical element group, 6 ... 2nd optical element group 40 ... core, 41 ... cladding, 42 ... covering material, 50 ... focus lens, 61A, 61B ... reflection mirror

Claims (5)

First light emitting means for emitting signal light;
A second light emitting means for emitting visible light guide light;
First light guiding means for guiding the signal light emitted from the first light emitting means to an optical fiber, and coupling the signal light to the optical fiber;
A second light guiding unit configured to guide the guide light emitted from the second light emitting unit to the optical fiber through a separate optical path from the signal light, and to couple the guide light to the optical fiber. An optical module characterized by that. The second light guide means emits the light path of the guide light emitted from the second light emitting means and is guided from the first light emitting means to the optical fiber by the first light guide means. In parallel with the optical path of the signal light, the guide light is guided to the optical fiber through a separate optical path from the signal light, and the guide light is incident on a condensing means for condensing the signal light on the optical fiber. The optical module according to claim 1, wherein the optical module collects light on the optical fiber. The second light guide means emits the light path of the guide light emitted from the second light emitting means and is guided from the first light emitting means to the optical fiber by the first light guide means. A condensing unit that makes a predetermined angle with respect to the optical path of the signal light, guides the guide light to the optical fiber through an optical path different from the signal light, and condenses the signal light on the optical fiber. The optical module according to claim 1, wherein the guide light is incident and condensed on the optical fiber. The first light guide unit couples the signal light to the optical fiber in a core mode, and the second light guide unit couples the guide light to the optical fiber in a clad mode. The optical module according to claim 1. The second light guide means reflects the guide light emitted from the second light emitting means outside the optical path of the signal light, and the optical path of the guide light is separated from the optical path of the signal light by the optical path. The optical module according to claim 1, further comprising reflecting means for guiding light to the optical fiber.

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