JPH05341155A - Photocoupler and manufacture thereof - Google Patents

Abstract

PURPOSE:To achieve efficient coupling using a simple method by coupling light emitted from a light emission diode to an optical fiber or other phototransmission mediums via a lens made by a diffraction grating. CONSTITUTION:A phototransmission medium such as optical fiber and other transparent thin films is coupled to an LED (light emission diode) 1 via a lens made by a diffraction grating comprising a hologram lens or the like. The diffraction grating is combined to LED 1 so that light is directed in a certain direction by the diffraction grating. Since the emission wavelength band of LED 1 is more or less broad, flux of light of a uniform distribution can be formed in the certain direction even with the directivity of the light. In a module which preferably has a fiber which is coupled to the light emitted from LED 1, a photosensitive material 3 is directly applied to the luminous part of LED 1 to form the hologram lens.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical coupler and a manufacturing method thereof, and more particularly to an optical coupler used for optical communication and a manufacturing method thereof. For example, it is applied to an optical pickup.

[0002]

2. Description of the Related Art The following are known documents which describe the prior art relating to the present invention. "High-precision optical coupling technology for single-mode optical fiber array and optical element array" (Takeshi Kato 3 persons, IEICE Technical Report No.197, EMC91-31) describes the following: There is. The single mode optical fiber array is made of Si V
Arrange by the groove guide, arrange the fibers on it, and
Place the press plate made of i and fix it with solder. Then, a tip lens is processed at the tip of each fiber by etching and discharging. In the alignment of the single mode optical fiber array and the optical element array, the micro positioner is aligned with respect to the rotation axis in addition to the orthogonal axis.

In addition, "Thin LED / PD for optical parallel transmission
The array module ”(Hiromoto Motohiro, 7 members, IEICE Technical Report No.197, EMC91-32) describes the following. LED for parallel transmission of 12-channel, 150-Mb / s / ch thin optical module with a thickness of 7 mm, which realizes module thinning and high speed by arranging optical element and electric element on each side and upper surface of submount. (Light Emitting Diode) / P
It has realized a D (Photo Diode) array module. In addition, the optical fibers are easily arranged by using a structure in which the optical fibers are inserted into the glass tubes arranged in an array of 250 μm pitch, and the thickness is 2 m.
It has become possible to store the m in the ferrule. The fiber has a core diameter of 62.5 μm and an outer diameter of 125 μm.

As a general technique, a single mode fiber requires high accuracy, but a multimode fiber has a large core diameter and is easy to couple. As a general method of coupling, there are a method of coupling a light emitting element and a fiber through a lens, and a method of assembling and coupling with a V groove with the tip of the fiber as a front sphere.

Conventionally, when connecting a fiber to an optical waveguide, for example, a method of adjusting through a ruby fiber and fixing with a photocurable resin was considered to be the best. However, the biggest problem is that it is difficult to perform position matching when coupling an LD (laser diode) with a fiber or a waveguide. Therefore, a special adjustment jig was needed. Also, the loss of light quantity is large. In addition, as another specific technique, in order to perform accurate coupling as in the above-mentioned publicly known document, a device for improving precision and selecting a material has been devised. Thus, single mode fiber is extremely strict in accuracy. However, a multimode fiber with a thick core diameter is easier to couple with an LD. Among the methods, the light loss is small when the light emitting element and the fiber are coupled via the lens. However, it requires precise adjustment of each fiber. At the same time, considerable light loss occurs. Also, if the tip of the fiber is a spherical tip, the assembly is simple, but the coupling loss is further increased. This is because the divergence angle is extremely large and the directivity is small.

Therefore, as shown in FIG. 5, even if the fiber is moved sufficiently close to the light emitting position for bad coupling, most of the light is transmitted through the wall of the fiber,
Does not propagate in fiber. That is, although some light 24 from the LED 23 is reflected and propagates at the boundary surface between the core 21 and the clad 22, most of the light 24 is in the clad 22.
Through. Further, as shown in FIG. 6, even if an attempt is made to separate the light emitting layer from the light emitting layer and perform coupling through the lens, a large amount of light does not enter the lens and is lost. When the multimode fiber is arranged sufficiently close to the light emitting layer, and if the light emitting element has sufficient directivity, the coupling efficiency is sufficiently increased even if it is not as accurate as the single mode fiber.

[0007]

[Purpose] The present invention has been made in view of the above-mentioned circumstances, and although it can be used in LDs and LD arrays, the main targets are LEDs and LED arrays that are relatively easy to make and have a very large divergence angle. It is an object of the present invention to provide an optical coupler and a method for producing the same, which are capable of efficiently coupling these light emitting devices with a simpler method than before and without any special adjusting jig.

[0008]

In order to achieve the above object, the present invention provides (1)
Coupling the light emitting diode to an optical transmission medium such as an optical fiber or other transparent thin film through a lens made of a diffraction grating such as a hologram lens, and further,
(2) In a module having a fiber or a fiber array for coupling light emitted from a light emitting diode (LED) or a light emitting diode (LED) array, directly to the light emitting portion of the light emitting diode (LED) or the light emitting diode (LED) array. A photosensitive material is applied to form a hologram lens, and (3) the light emitting element is a laser diode (LD) or a laser diode (LD) array, and a multilayer film is provided between the light emitting element and the hologram. Alternatively, another transparent solid is provided via an air layer to create a hologram on it, or (4) the hologram is a volume hologram and is exposed to light of the same wavelength as the used wavelength or a different wavelength. The material is stable and the hologram is stable by UV irradiation and heating. After using a photosensitive material to create a light emitting element with a vacuum device, etc., apply a photopolymer as the photosensitive material, align the optical axis of the object light and the thin reference light for hologram lens exposure at the light emitting position, and adjust the volume. Type hologram lens is exposed and ultraviolet rays are heated to stabilize the material, or (5) the hologram is a volume hologram and is exposed to light having the same wavelength as the used wavelength or a different wavelength. Use a photosensitive material whose hologram is stable by UV irradiation and heating.After creating a light emitting element with a vacuum device, etc., apply a photopolymer resin and accurately position the pre-made stamper at the light emitting position. After aligning, press the stamper and expose it from the side with ultraviolet rays to solidify and peel it off, or create a hologram lens, or ( ) A hologram is a volume hologram, and a light-sensitive material that is sensitive to light of the same wavelength as the wavelength used or a different wavelength, and the hologram is stable by irradiation with ultraviolet light and heating, and creates a light-emitting element with a vacuum device. After applying the volume hologram material and accurately aligning the inline hologram lens, irradiate ultraviolet rays or laser light through the inline hologram to duplicate the hologram lens to create the hologram lens. It is characterized by. Hereinafter, description will be given based on examples of the present invention.

1 (a) to 1 (e) are configuration diagrams for explaining an embodiment of a method for manufacturing an optical coupler according to the present invention. FIG. 1 (a) is a completed LED, and FIG. 1 (b) is a hologram material. Coating, drawing (c) shows exposure, drawing (d) shows ultraviolet exposure and drawing (e) shows heating. In the figure, 1 is LE
D, 2 are LED substrates, and 3 is a volume photopolymer.

Single-mode fibers are extremely strict in accuracy. Therefore, a multimode fiber with a large core diameter has a large core diameter and is easier to couple, but any of the conventional methods has a large coupling loss. This is particularly remarkable in LEDs, but it is because the divergence angle of the light emitting element is extremely large and the directivity is small. If the multimode fiber is arranged sufficiently close to the light emitting layer and the light emitting element has sufficient directivity, the coupling efficiency will be sufficiently increased even if the accuracy is not as high as that of the single mode fiber.

The present invention is for coupling to an LED via a diffraction grating. This diffraction grating has a lens function, and a hologram lens or the like is suitable. But LE
Since the emission wavelength of D is wide, it is unlikely to combine it with a diffraction grating. However, the purpose of combining the diffraction grating with the LED here is that the diffraction grating has a directivity in a certain direction and the emission wavelength band of the LED is broad to a certain degree, so that it has directivity. This is because a light beam having a uniform distribution can be formed in a certain direction.

Another main feature of the present invention is a module having a fiber or a fiber array for coupling light emission from an LED or an LED array, wherein a light-sensitive portion is directly coated with a photosensitive material, and a hologram lens is applied thereto. Is formed, thereby giving a directivity to the light of the LED. Here, the hologram lens is equivalent when the end surface of the light emitting element is a spherical lens. However, the latter requires more advanced technology and time than the former. Regarding that, recently, a hologram material that can be easily processed has been announced. It is a volume hologram, which is a material that is exposed to light of the same wavelength as the used wavelength or a different wavelength, and the hologram is stable by irradiation with ultraviolet light and heating. Since this material does not use a solvent, the element itself is not corroded or soiled. Moreover, since the heating is also performed at about 100 ° C., the element is not destroyed. Therefore, after producing a high-performance light emitting element by a normal process in vacuum, a hologram material can be directly applied to the element and a hologram can be directly formed on the element by exposure.

On the other hand, since the conventional materials use the solvent as described above, they corrode or stain the light emitting element itself. Therefore, the hologram is usually prepared separately from the light emitting element, and then assembled and adjusted to the light emitting element. This method requires sophisticated adjustment technology. That is, position adjustment in the X, Y and Z directions and tilt adjustment in the X, Y and Z directions. This is the same method as coupling using other lenses. Conventionally, it has been a big problem that the optical coupler takes a lot of time and effort for this highly accurate adjustment.

However, if the hologram material is directly applied to the light emitting element after the above light emitting element is prepared and the hologram lens is directly exposed, the adjustment becomes very simple. That is, each hologram lens can be exposed while being accurately aligned while passing through the optical microscope at the light emitting position. This optical adjustment is a one-time operation and is much easier and faster than the mechanical adjustment described above. In addition, since the coupling partner is a multimode fiber, the core diameter is large, so that the light emitting source can have directivity and the coupling efficiency is significantly increased. This is shown in FIG. In the figure, 4 is the light of the LED, 5 is the core, 6
Is the clad. The directivity of the light emitting source 1 enables efficient light propagation in the core of the fiber.

As a method of directly forming the hologram lens on the surface of the LED, there are a method of using a volume bologram material and a method of using a photopolymer (2P-photo polymer-resin) used in an optical disk or the like as described below. is there. When a volume hologram material is used, a material that is exposed to light having the same wavelength as the used wavelength or a different wavelength, and the hologram is stable by irradiation with ultraviolet light and heating is used. After concealing the light emitting element with a vacuum device etc., apply the photopolymer to it, align the optical axes of the object light and the thin reference light for exposure of the hologram lens at the light emitting position, and use the volume hologram lens. It may be prepared by exposing, exposing to ultraviolet rays, and heating to stabilize the material (see FIG. 1). The lens formed at this time is usually an off-axis type lens, but an in-line type hologram lens can be accurately formed on the light emitting layer by synthesizing light by a half mirror and exposing as shown in FIG. In FIG. 3, reference numeral 7 is reference light, 8 is object light, 9 is a lens, and 10 is a prism (half mirror).

The method using the 2P resin is to press the metal master of the surface relief type hologram. After creating a light-emitting element with a vacuum device, etc., apply 2P resin to it, and after accurately aligning the pre-created stamper at the light-emitting position with the microscope and manipulator, press the stamper to press the light-emitting element side or ring. Ultraviolet rays are radiated from the sides to solidify and peel off the stamper. Further, when the volume hologram is produced, if an inline hologram lens is used as shown in FIG. 4, it can be produced more easily by a contact exposure method. In the figure, 11 is a reproduction light, and 12 is an in-line hologram lens. After a light emitting element is created by a vacuum device or the like, a volume hologram material is applied to the light emitting element, and the inline hologram lens 12 is accurately aligned, and then ultraviolet light or laser light is passed through the inline hologram 12. Irradiate. Then, the diffracted light becomes the object light and the transmitted light becomes the reference light, so that the hologram lens can be easily duplicated.

These can be applied not only to LEDs but also to LDs and LD arrays. However, if the hologram material is applied as it is, the reflectance of the end face is lowered and the light emission power is greatly lowered. Therefore, a multilayer film is formed on the end face of the LD so as not to lower the reflectance of the end face, or an air layer is provided and another solid substance is then adhered, and the hologram material is applied thereon. Or DFB (Distributed
Feed Back; DBR (Distributed)
Bragg Reflector: Apply the hologram material on the end face of the laser and expose the hologram. By doing this, without sacrificing the light emission power of the LD,
Can be coupled. Also, if the hologram material is applied to the light emitting surface to some extent directly, it will affect the light emission power. Therefore, if the same treatment is carried out so that the end face of the LED maintains the same reflectance as when it is cleaved, There is little change in emission power.

[0018]

[Effect] As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1; By intentionally combining an LED and a hologram lens or the like, it is possible to give directivity to a certain direction of a light beam. Moreover, the distribution of the light intensity in a certain direction becomes uniform in the light emission direction. Therefore, although the coupling efficiency is not so high as around 10%, the mounting tolerance such as the position and direction of the fiber becomes very loose. In the conventional method, since the mounting tolerance is small, the coupling efficiency may vary. However, the diffractive grating element such as the hologram lens is dared to be L.
An optical coupler with stable performance can be formed by combining with ED. (2) The effect corresponding to claim 2; since the hologram lens is easy to make, the end surface of the optical element may be a spherical lens,
It is easier to create than inserting a lens.
In addition, the production is easy because the exposure position is simply overlapped with the emission position while looking at it with the optical machine. Further, since a hologram at an accurate position can be set and the other party is a multimode fiber having a large core diameter, a large amount of light can be transmitted without loss and the optical coupling efficiency is high. (3) Effect corresponding to claim 3; Since the coupling can be performed without reducing the end face reflectance of the LD, the coupling can be efficiently performed even in the LD or the LD array. (4) Effect corresponding to claim 4; In addition to the same effect as claim 2, this material does not corrode or contaminate the light emitting element itself, since a hologram can be created only by a dry process. Also, the hologram function does not deteriorate even if touched to some extent. (5) Effects corresponding to Claims 5 and 6; In addition to the same effects as Claim 2, it can be created only by adjusting the position of the stamper or the position of the master hologram. 4 is necessary for adjusting the reference light and the object light). Also, there is no need to heat.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining one embodiment of a method for manufacturing an optical coupler according to the present invention.

FIG. 2 is a diagram showing an embodiment of an optical coupler according to the present invention.

FIG. 3 is a diagram showing another embodiment of the optical coupler according to the present invention.

FIG. 4 is a view showing still another embodiment of the optical coupler according to the present invention.

FIG. 5 is a diagram showing a conventional optical coupler.

FIG. 6 is a diagram showing another conventional optical coupler.

[Explanation of symbols]

1 ... LED, 2 ... LED substrate, 3 ... Volume photopolymer.

Claims (6)

[Claims] 1. An optical coupler, characterized in that light emitted from a light emitting diode is coupled with an optical fiber or another optical transmission medium through a lens made of a diffraction grating. 2. In a module having a fiber or a fiber array for coupling light emitted from a light emitting diode or a light emitting diode array, a photosensitive material is directly applied to a light emitting portion of the light emitting diode or the light emitting diode array to form a hologram lens. An optical coupler characterized by being performed. 3. The light emitting element is a laser diode or a laser diode array, and another transparent solid is provided between the light emitting element and the hologram via a multilayer film or an air layer to form a hologram thereon. The optical coupler according to claim 2. 4. The hologram is a volume hologram,
Use a photosensitive material that is exposed to light of the same wavelength as the used wavelength or a different wavelength, and that has a hologram that is stable when irradiated with ultraviolet light and heated. Stabilize the material by applying a polymer, aligning the optical axis of the object light and the thin reference light for exposure of the hologram lens at the light emitting position, exposing the volume hologram lens, and applying heat by applying ultraviolet light. A method for producing an optical coupler characterized by the above. 5. The hologram is a volume hologram,
Use a photosensitive material that is sensitive to light of the same or different wavelength as the wavelength used, and that has a hologram that is stable when exposed to UV light and heated. After creating a light-emitting element using a vacuum device, apply a photopolymer resin. Then, after accurately aligning the stamper previously created at the light emitting position, the stamper is pressed and exposed from the side with ultraviolet rays to be solidified and peeled off, thereby forming a hologram lens. Production method. 6. The hologram is a volume hologram,
After using a photosensitive material that is sensitive to light of the same or different wavelengths as the wavelength used and whose hologram is stable by UV irradiation and heating, create a light-emitting element with a vacuum device, etc., and then change the volume hologram material. After coating and accurately aligning the in-line type hologram lens, ultraviolet ray or laser light is irradiated through the in-line type hologram, and the hologram lens is duplicated to produce an optical coupler. Method.