JP3947460B2 - Optical module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical module incorporating an optical element and an optical transmission body. More specifically, the present invention relates to an optical module in which the positional relationship between the optical element and the optical transmission body is adjusted with high accuracy and the reliability is improved.
[0002]
[Prior art]
For example, an optical module in which a semiconductor laser chip and an optical fiber are incorporated as a pumping light source is used in an EDFA (optical fiber amplifier) used as a relay point in a trunk transmission line and playing a role of signals. This type of optical module has a structure as shown in FIG. That is, the substrate 1 is disposed on the Peltier element 12 in the housing 11, and the substrate 1 is provided with the semiconductor laser chip 21 via the submount 7, the optical fiber 31 via the optical transmitter fixing base 3 a, and the light reception. The light receiving element 6 is fixed to the substrate 1 through the element fixing base 6a. And the optical transmission body fixing base 3a and the optical fiber 31 are being fixed using the solder material 5 (refer patent document 1). On the other hand, in this type of optical module, in order to reduce the load on the semiconductor laser chip 21, the coupling efficiency between the semiconductor laser chip 21 and the optical fiber 31 is required to be 80% or more. The positional accuracy of the optical fiber 31 needs to be about ± 0.2 μm or less.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-333472 (FIG. 1)
[0004]
[Problems to be solved by the invention]
In the above-described optical module, since the optical fiber is fixed by soldering, there is an advantage that when the positional deviation occurs, it can be corrected by melting the solder material again. As described above, heat at the time of melting the solder material when the optical fiber is fixed is transferred to the semiconductor laser chip, which may deteriorate the characteristics of the semiconductor laser chip.
[0005]
In addition, as a method of precise alignment between an optical element such as a semiconductor laser chip and an optical transmission body such as an optical fiber, the present inventors measure an absolute value of a deviation amount at the time of fixing with a laser micrometer. Thus, a method for easily and accurately aligning an optical element and an optical transmission body has been invented and disclosed in Japanese Patent Application No. 2002-320722. If the substrate is not a transmissive substrate, it is emitted from a laser micrometer. The parallel light beam reflected by the substrate is not transmitted to the light receiving portion, the amount of deviation in the direction parallel to the substrate (X direction) cannot be measured, and perfect alignment cannot be performed.
[0006]
The present invention has been made in view of such circumstances, and the positional relationship between the optical element and the optical transmission body can be accurately adjusted without degrading the optical element, the coupling efficiency is high, and the optical element or the like can be used. An object is to provide an optical module with high reliability.
[0007]
[Means for Solving the Problems]
In the optical module according to the present invention, an optical element composed of a light emitting device or a light receiving device is fixed on a substrate, the optical element and the optical fiber are coupled to face each other in the axial direction of the optical fiber, and the optical fiber is An optical module fixed on a substrate, wherein the substrate is made of a material that is not transmissive to laser light of a laser micrometer that detects the position of the optical fiber, and the optical element fixing portion and the light The position of the optical fiber can be recognized by transmitting the laser light of the laser micrometer to the position where the optical fiber extends on or above the surface of the substrate between the fixed portion of the fiber. It consists of a substrate having a through hole.
[0009]
Further, the term “fixed on the substrate” means not only the case of directly fixing on the substrate but also the case of fixing on the substrate via a fixing base or a submount. Furthermore, the fixed portion refers to a fixed portion on the substrate side when directly fixed to the substrate, and when fixed to the substrate via a submount or a fixing base, the submount or the fixing base and the substrate. And a fixing portion on the substrate side of the fixing surface.
[0010]
As described above, by providing the through hole between the optical element fixing portion and the optical transmission member fixing portion of the substrate, the heat generated during soldering is hardly transmitted to the optical element side. Deterioration can also be prevented. That is, since heat generated during soldering has a through hole, it takes time for heat to reach the optical element without being transmitted to the optical element at the shortest distance, making it difficult for heat to be transmitted to the optical element. On the other hand, when heat is generated by the operation of an optical element like a semiconductor laser chip, it is transferred to the substrate directly below through the submount and absorbed by the substrate at a constant temperature by a Peltier element, etc., and the heat of the optical element is absorbed. There is no danger of raising it higher than necessary.
[0011]
Furthermore, even when the optical element and the optical transmission body are aligned using a light transmission type measuring instrument such as a laser micrometer, the light can be transmitted through the through-hole. The positional relationship in the X direction (see FIG. 1) as well as the positional relationship in the Y direction between the optical transmission body and the optical transmission body is accurately matched, and the positional accuracy improves. That is, the laser micrometer can be installed so as to face the through hole using a laser micrometer before the optical transmission body is fixed with the solder material, and the parallel light beam emitted from the laser micrometer emitting portion is passed through the through hole. The X-direction optimum position can be measured, and after fixing with a solder material, the X-direction position is again measured using the laser micrometer, and the X-direction is reached. It is possible to detect the amount of deviation and correct the position, thereby improving the positional accuracy and improving the coupling efficiency.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the optical module of the present invention will be described with reference to FIGS. In the optical module according to the present invention, as shown in FIG. 1 (a), which is an explanatory diagram of an optical module according to one embodiment, for example, an optical element 2 and an optical transmitter fixing base 3a are fixed on a substrate 1. The optical element 2 and the optical transmission body 3 are coupled, and the optical transmission body 3 is fixed to the optical transmission body fixing base 3a. The present invention is characterized in that the substrate 1 is composed of a substrate having a through hole 13 between the optical element fixing portion 16 and the optical transmission member fixing portion 17.
[0013]
The substrate 1 is made of an insulating substrate having a through hole 13 between the optical element fixing portion 16 and the optical transmission member fixing portion 17. In the example shown in FIG. 1, the optical element 2 is fixed via a submount 7 and the optical transmission body 3 is fixed via an optical transmission body fixing base 3a. Further, the substrate 1 is preferably made of a substrate having good thermal conductivity such as AlN or SiC from the viewpoint of heat dissipation, but is not limited to this, and Al ₂ O ₃ or quartz substrate having poor thermal conductivity. Or a glass ceramic substrate. The size of the substrate is, for example, about 6 mm in the X direction, about 1 mm in the Y direction, and about 8 mm in the Z direction, but is not limited to this size. Here, the Z direction refers to the optical axis direction connecting the optical element 2 and the optical transmission body 3, the Y direction refers to a direction perpendicular to the surface of the substrate 1 to which the optical element 2 is fixed, and the X direction refers to A direction perpendicular to the Y direction and the Z direction (refer to FIG. 1).
[0014]
The through hole 13 is formed between the optical element fixing portion 16 and the optical transmission member fixing portion 17 so as to penetrate the substrate 1. By being formed in this way, for example, when the optical transmission body 3 is fixed to the optical transmission body fixing base 3a by soldering, it takes time for heat to be transmitted to the optical element 2, and the temperature of the optical element 2 is increased. This can be prevented and the characteristics of the optical element are not deteriorated. Further, from this point of view, it is preferable that the size of the through-hole 13 is larger in that the heat at the time of soldering is more difficult to be transmitted to the optical element 2 side, but it is 0 in relation to the strength of the substrate 1. The width (W) is about 5 mm and the length (L) is about 50% or less of the width of the substrate 1. Further, as will be described later, the through-hole 13 preferably transmits the parallel light beam emitted from the laser micrometer emission unit 10a during the alignment in the X direction, and has a width (W) capable of transmitting the parallel light beam. ) And the length (L) is smaller than the width of the beam, the position of the optical transmission body 3 is determined with reference to the end of the through hole 13 of the substrate 1 at the time of alignment. It is desirable in that it can be measured relatively.
[0015]
It is desirable that the light transmission base fixing base 3a be made of glass ceramics, mullite (a mixture of Al ₂ O ₃ and MgO), quartz or the like with poor heat dissipation. That is, as will be described later, when the optical transmission body 3 such as the optical fiber 31 is used to fix the optical transmission body fixing base 3a with the solder material 5, the solder material 5 is melted and the optical transmission body 3 is fixed. Heating is performed using hot tweezers or the like, but heat is also transmitted to the optical element 2 through the optical transmission body fixing base 3 a and the substrate 1. For this reason, there is a possibility that the characteristics of the optical element 2 may be deteriorated, and in order to prevent this, the heat at the time of melting the solder material 5 is transferred to the optical element 2 side by using a material with poor heat dissipation for the optical transmission body fixing base 3a. It can be difficult to communicate.
[0016]
The optical element 2 is not only a light emitting device such as a semiconductor laser or a light emitting diode, a light receiving device such as a photodiode, but also a lens coupled with the light emitting device or the light receiving device or an optical transmission body such as a combination of these or an optical waveguide. For example, in the example shown in FIG. 1A, a semiconductor laser chip 21 is used as the optical element 2, and an EDFA excitation light source is a high output power of 980 nm band InGaAs. A semiconductor laser is used.
[0017]
The optical element 2 is generally die-bonded with a solder material (not shown) separately on the submount 7 having good thermal conductivity such as AlN, and the submount 7 in which the optical element 2 is die-bonded is the substrate 1. The optical element fixing part 16 in this case is fixed to the substrate 1 side between the submount 7 and the substrate 1 by using a solder material (not shown) such as an Au—Sn alloy. Part. It is also possible to first fix the submount 7 on the substrate 1 and then die-bond the optical element 2 thereon, and the optical element 2 can be directly mounted on the substrate 1 without using the submount 7. In this case, it is a fixing portion on the substrate 1 side between the optical element 2 and the substrate 1.
[0018]
Further, as another example of the optical element 2, for example, as shown in FIG. 2A, a combined body in which the semiconductor laser chip 21 and the lens 22 are integrally coupled may be used. The combined body includes a semiconductor laser chip 21 and a lens 22 formed on the submount 7. The lens 22 condenses the light emitted from the semiconductor laser chip 21 into a parallel beam, and the optical transmission body 3, for example, described later. This is for transmission to the optical component assembly 32. Specifically, as shown in FIG. 2A, a lens bracket 22a and the like are formed on the submount 7 by YAG welding or the like, and then the semiconductor laser chip 21 is fixed, and the lens is attached to the lens bracket 22a. It is formed by fixing 22 with an adhesive or the like. A lens may be provided directly on the submount 7. Further, the optical element 2 may be other than these, for example, a can packaged semiconductor laser, an optical waveguide, a combination of a plurality of lenses and a light emitting device such as the semiconductor laser chip 21, etc. It may be a light receiving device such as a photodiode.
[0019]
The submount 7 is preferable because it has good thermal conductivity because it easily dissipates heat generated from the optical element 2 to the substrate 1 side when the optical element 2 is driven, but is not limited to this. A submount in which an oxide film is formed may be used.
[0020]
A light receiving element 6 is provided on the surface of the submount 7 or on the substrate 1. The light receiving element 6 may be built in the submount 7 or may be individually provided at any location on the substrate 1 via the light receiving element fixing base 6a. That is, it should just be installed in the position which can receive a part of light emitted from the optical element 2. The light receiving element 6 receives light emitted from the optical element 2 to monitor the optical output of the optical element 2 and perform auto power control driving (hereinafter referred to as APC driving) so as to keep the optical output constant. A photodiode made of Si, InGaAs or the like is generally used.
[0021]
The optical transmission body 3 is an optical component assembly 32 including an optical transmission path such as an optical fiber 31 and an isolator or a condenser lens coupled to the optical transmission path. In the example shown in FIG. The optical fiber 31 is used, and is fixed on the optical transmission body fixing base 3a so that one end of the optical fiber 31 passes through the through hole 13 and is coupled to the optical element 2 by a coupling method described later. In this case, the light transmission member fixing portion 17 is a fixing portion on the substrate 1 side between the light transmission member fixing base 3 a and the substrate 1. Further, the optical transmission body 3 may be directly fixed to the substrate 1 without providing the optical transmission body fixing base 3a. In this case, the optical transmission body 3 and the substrate 1 are fixed on the substrate 1 side. Part. When the direct optical fiber 31 is used, it is desirable to use a wedge-shaped lensed fiber at the tip because the coupling efficiency can be further increased. That is, the wedge-shaped lensed fiber at the tip is a spherical lens in the Y direction. For example, when the semiconductor laser chip 21 is used as the optical element 2, the light emission angle in the Y direction is generally large. If fiber is used, the coupling efficiency does not drop.
[0022]
Further, when a plated optical fiber is used as the optical transmission body 3, it is desirable to heat the optical fiber 31 in advance in order to increase the positional accuracy. That is, for example, the Ni / Au plated optical fiber 31 is stressed by plating, and the present inventors have found that the position of the optical fiber 31 in the Y direction is deformed by about 10 μm when heat is applied. It was further found that the stress of plating is relaxed by heating the fiber 31, and hardly changes even when heated again. Therefore, when using the optical fiber 31 with the plating, for example, performing heat treatment at 150 to 400 ° C. for about 10 to 60 seconds, preferably about 300 ° C. for about 30 seconds, further reduces the amount of misalignment. It is desirable in that it can.
[0023]
Another example of the optical transmission body 3 may be an optical component assembly 32 connected to an optical fiber. For example, as shown in FIG. 2B, the optical component assembly 32 includes a collimator lens 32a, an isolator 32b, a condenser lens 32c, a sleeve 32d, a ferrule 32e, and the like combined in a cylinder 32f. The light emitted from the element 2 is collected and transmitted to the optical fiber 31 or the like coupled to one end of the optical component assembly 32. The optical component assembly 32 may have a configuration other than the configuration described above. That is, any structure may be used as long as it transmits light emitted from the semiconductor laser chip 21 and does not transmit or refract the light of the laser micrometer 10. For example, BK7 (boron silicate crown glass ) Or a single lens such as a rod lens made of quartz or the like, as long as it has a configuration that does not transmit or refract the light of the laser micrometer 10.
[0024]
The Peltier element 12 controls the temperature on the substrate 1 by absorbing heat generated when the optical element 2 is driven, and generally includes a plurality of p-type and n-type thermoelectric elements. Are arranged in series and sandwiched between both sides by a ceramic substrate, and controlled based on the temperature monitored by the thermistor 15 on the substrate 1. The thermistor 15 is a resistor sensitive to heat, and is a semiconductor thermosensitive element obtained by sintering a transition metal oxide mainly composed of Mo or Co. The temperature detected by the thermistor 15 is monitored and the Peltier is detected. By feeding back to the element 12, the temperature of the substrate 1 is controlled to be constant.
[0025]
Next, the alignment in the X direction when the substrate 1 having the through holes 13 is used and the method for manufacturing the optical module of the present invention will be described with reference to FIG.
[0026]
As shown in FIG. 1B, a substrate 1 on which a semiconductor laser chip 21 or the like is assembled is placed on a work table 14 having a constant temperature such as a Peltier element, and an optical transmission body 3 composed of an optical fiber 31 is formed. One end is fixed by a drive mechanism 8 such as an XYZ stage that can be finely adjusted to 0.1 μm or less in the XYZ direction so as to face the semiconductor laser chip 21 through a through hole in the side wall of the housing 11. The work table 14 is also provided with a through hole in a portion corresponding to the through hole 13 of the substrate 1. Then, the semiconductor laser chip 21 is driven, and the optical fiber 31 is moved by the drive mechanism 8 to adjust the position so that the coupling with the semiconductor laser chip 21 becomes the optimum position. In the position adjustment, the optical fiber 31 is disposed on the optical transmitter fixing base 3a, and the semiconductor laser chip 21 is APC driven. On the other hand, a light output measuring instrument (not shown) is installed on the other end side of the optical fiber 31 so that light is incident on the optical fiber 31 and the output transmitted from the optical fiber 31 is monitored so that the optimum position is obtained. This is done by adjusting the XY direction of the optical fiber 31 by the drive mechanism 8. Note that the Z direction is insensitive to misalignment and can be adjusted without using the drive mechanism 8, but may be adjusted using the drive mechanism 8.
[0027]
And the absolute position of a X direction is measured using the laser micrometer 10 (10a, 10b, 10c) in the state match | combined with the optimal position. The Y direction can be similarly measured using the laser micrometer 10 (10d, 10e, 10c). The laser micrometer 10 (10a to 10e) is a non-contact high-precision laser measuring sensor that enables high-precision dimension control, and reflects a laser beam emitted from a laser oscillator by a polygon mirror that rotates at high speed. The collimator lens to emit parallel light rays 10a and 10d, the collimating lens to collect the parallel light rays on the light receiving element 10b and 10e, and the light received by the light receiving portion to the dimensions and display the processing control portion 10c. The parallel light beams emitted from the emitting units 10a and 10d scan the measurement object at high speed, receive the light at the light receiving units 10b and 10e, and control the processing according to the brightness of light caused by being blocked by the measurement object It is displayed as a dimension in the part 10c, the resolution is about 0.02 μm, and the measurement accuracy is about 0.1 μm.
[0028]
By using this laser micrometer 10, it is possible to detect the absolute value of the deviation amount after fixing with the solder material 5, and accurately detect the relative position with respect to the optical element 2 again during correction. Can be combined. For example, as shown in FIG. 1 (b), in measurement in the X direction, the emitting part 10a and the light receiving part 10b of the laser micrometer 10 are installed in the Y direction so as to face the through hole 13, and the emitting part 10a. The parallel rays emitted from the laser beam pass through the through-hole 13, reach the light receiving unit 10b, and are converted into dimensions in the X direction by the processing control unit 10c. Similarly, with respect to the Y direction, the laser micrometer 10 (10d, 10e, 10c) is installed in the X direction and converted into a dimension in the Y direction. Further, for the measurement of the absolute position in the X direction, for example, FIG. 3A shows a cross-sectional view of the substrate (a cross-sectional view in the direction of AA in FIG. 1B, which mainly includes the laser micrometers 10a and 10b). As shown in the figure, a parallel light beam having a width wider than the width (L) of the through hole of the substrate is emitted from the emitting portion 10a, and in the light receiving portion 10b, it becomes a shadow of the substrate 1 and a shadow of the optical fiber 31. Since the location does not receive light, the relative position of the optical fiber 31 (distance B in FIG. 3A) can be measured with the end of the through hole 13 as a reference. Although it is possible to use the end of the beam width of the laser micrometer 10 as a reference, if the laser micrometer 10 moves even a little, the measurement value will be distorted. It is preferable to measure the reference position (B). As for the Y direction as well, as shown in the substrate cross-sectional view of FIG. 3B (the cross-sectional view of the AA direction of FIG. 1B and mainly the laser micrometers 10d and 10e), the substrate 1 The distance C can be measured with reference to the surface.
[0029]
Next, the optical fiber 31 whose position has been adjusted is fixed to the optical transmission body fixing base 3 a with the solder material 5. The fixing with the solder material 5 is performed by setting the solder material 5 around the optical fiber 31, melting the solder material 5 by performing a heat treatment at about 300 ° C. using a hot tweezers, and then cooling it. . In addition, although the Au-Sn alloy (Au80at% content) is used for the solder material 5 in the example shown by Fig.1 (a)-(b), it is not limited to these, Au-Sn alloy In addition, a material having a different Au content, a Sn—Pb alloy, In, or the like can be used. By using the solder material 5 in this manner, unlike the fixation by welding using the YAG laser, the fixation can be easily released and the fixation can be performed again. In other words, if the YAG laser is fixed, it is difficult to correct the misalignment, the accuracy is poor, and the readjustment is limited. But it can be corrected.
[0030]
Next, after being fixed by the solder material 5, the position in the X direction of the optical fiber 31 is measured by the laser micrometer 10 to detect the deviation Δd from the value stored as the optimum position. Then, the drive mechanism 8 shifts the optical fiber 31 from the optimum position and fixes it again by an amount of deviation Δd in the X direction detected by melting the fixing portion of the optical fiber 31. Even if the re-adhesion is performed, a deviation in the vicinity of Δd occurs from the set position. Therefore, the optical fiber 31 is fixed in the vicinity of the optimum position by setting it by deviating by Δd in advance. The position in the X direction of the optical fiber 31 after this re-adhesion is measured, and if the amount of deviation from the optimum position is large, the same adjustment is repeated again. This is because if the thermal history is not reproducible (the amount of deviation differs even when the same temperature is applied), the amount of deviation may occur even after adjustment. The alignment in the Y direction is similarly performed. Finally, the substrate 1 on which the optical fiber 31 and the semiconductor laser chip 21 are mounted is incorporated on the Peltier element 12 in the casing 11, and the casing 11 is closed and sealed in a nitrogen atmosphere.
[0031]
As described above, even if the alignment is performed in the past, in actuality, a position shift occurs when an optical transmission body such as an optical fiber to be performed after the alignment is fixed. When fixing an optical fiber or the like by welding, it is difficult to correct the plurality of times.On the other hand, in order to enable correction, even when fixing using a solder material, when the solder material melts, Since the position is displaced due to heat treatment or the like, and the displacement direction of the optical fiber or the like and the absolute amount thereof are not known, complete alignment cannot be performed. In order to adjust the position of the optical transmission body 3 such as the optical fiber 31 in the X direction, the laser micrometer is used to first determine the optimum position, and after fixing with the solder material, from the optimum position. Noz It is possible to detect the amount. That is, by using a substrate in which a through-hole is provided between the optical transmission body and the optical element, the light emitted from the laser micrometer emission unit 10a as shown in FIG. While recognizing the position of the laser beam, the laser beam passes through the through-hole 13 and reaches the laser micrometer light receiving unit 10b, so that the optimum position in the X direction and the amount of deviation can be accurately measured. The binding efficiency with the body can be increased.
[0032]
Furthermore, by providing this through-hole, heat during soldering is difficult to transfer to the optical element side, and heat generated from the optical element during operation is absorbed by a Peltier element or the like provided directly under the substrate, resulting in a rise in temperature. Can be prevented.
[0033]
In each of the above examples, the semiconductor laser chip 21 is used as the optical element 2 and the optical fiber 31 is used as the optical transmission body 3. However, the present invention is not limited to these examples. In the same manner, it is possible to prevent deterioration of the optical element due to heat and perform accurate alignment.
[0034]
【The invention's effect】
According to the present invention, since the substrate is made of a substrate having a through hole between the optical element fixing portion and the optical transmission member fixing portion, the optical element is not deteriorated due to heat generated during soldering. Also, since the positional accuracy of the optical element and the optical transmission body can be precisely matched with less man-hours not only in the Y direction but also in the X direction during assembly, the optical module has a very high characteristic and high reliability. It can be obtained inexpensively.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective explanatory view for explaining alignment of an optical module according to the present invention and alignment in an X direction and a Y direction.
FIG. 2 is an explanatory side view illustrating an optical element and an optical transmission body according to another embodiment of the present invention.
FIG. 3 is an explanatory cross-sectional view illustrating a method of aligning an optical transmission body using a substrate according to the present invention.
FIG. 4 is an explanatory perspective view of the inside of a housing of a conventional optical module.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Optical element 3 Optical transmission body 13 Through-hole 16 Optical element fixing | fixed part 17 Optical transmission body fixing | fixed part

Claims (1)

An optical element composed of a light emitting device or a light receiving device is fixed on a substrate, the optical element and an optical fiber are coupled to face each other in the axial direction of the optical fiber, and the optical fiber is fixed on the substrate. A module, wherein the substrate is made of a material that is not transmissive to laser light of a laser micrometer that detects the position of the optical fiber, and is between the fixing portion of the optical element and the fixing portion of the optical fiber. And a substrate having a through hole through which the laser light of the laser micrometer can be transmitted and the position of the optical fiber can be recognized at a position where the optical fiber extends on or above the surface of the substrate. Optical module.

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