JP2003209268A - Optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module in which an assembling man hour is reduced when a photodetector for monitoring an optical output is mounted and a cost is decreased. <P>SOLUTION: The optical module comprises a light emitting element, the photodetector for monitoring the optical output of the emitting element, and a mounting board. A photodetecting sensitivity layer formed in a planar state of the photodetector for monitoring the optical output has a structure having a sensitivity at a base side. The emitting element and the photodetector are horizontally mounted on the board. The optical module further comprises an optical element such as a diffraction grating, a prism having an uneven pattern or the like formed on an incident light side base end face of the photodetector. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device using a light emitting element such as a semiconductor laser diode (hereinafter referred to as LD) used for optical communication and a light receiving element for monitoring its optical output, and a method of manufacturing the same. In particular, the present invention relates to a method of mounting a light receiving element for capturing light emitted from the back side of the semiconductor LD.

[0002]

2. Description of the Related Art In order to popularize a public communication network using optical fibers, it is important to manufacture high-performance semiconductor laser devices at low cost.

The output of the semiconductor LD decreases with the deterioration over time and the temperature rise during operation. Therefore, in the semiconductor LD for optical communication, the light emitted from the back side of the semiconductor LD (hereinafter referred to as monitor light) is received by the light output monitoring light receiving element (hereinafter referred to as monitor light receiving element). Light is received and the semiconductor LD is controlled based on the current generated here, and the output of the semiconductor LD is kept constant.

FIG. 8 is a perspective view (1) of one example of a semiconductor laser device 50 according to the prior art, and a partially cutaway side view (2). In FIG. 8, 2 is a substrate, 4 is a semiconductor LD
Element, 6 is an active layer of a semiconductor LD element, 8 is a base material of a monitor light receiving element, 10 is a light receiving sensitivity layer of a monitor light receiving element, 1
Reference numeral 2 is a monitor light receiving element, 14 is monitor light, 16 is laser output light, 102 is a semiconductor LD subcarrier, and 104 is a submount of the monitor light receiving element.

In the semiconductor laser device 50 shown in FIG.
In order to efficiently receive the monitor light 14 emitted from the rear of the semiconductor LD element 4, the monitor light receiving element 12 is arranged perpendicular to the monitor light 14.

FIG. 9 is a partially cutaway side view of another example of the conventional semiconductor laser device. The same symbols as in FIG.
Indicates the same or equivalent. Further, 106 is a spacer and 108 is a reflective film.

In the semiconductor laser device 50 of FIG. 9,
The monitor light 14 is reflected by the reflective film 108 on the substrate 2 and guided to the sensitivity surface of the light receiving sensitivity layer 10. Examples of these conventional techniques (FIGS. 8 and 9) are disclosed in Japanese Patent Laid-Open No. 2000-323745.

In the semiconductor laser device 50 according to FIG. 8, it is certainly possible to incorporate a large amount of light into the light receiving sensitivity layer 10 of the monitor light receiving element 12. However, on the other hand, setting the monitor light-receiving element 12 to be perpendicular to the monitor light 14 has a problem that it takes time and man-hours. There is also a problem that it is difficult to carry out the wiring work between the monitor light receiving element 12 and the monitor light receiving element submount 104.

Further, in the semiconductor laser device 50 according to FIG. 9, since the semiconductor LD element 4 and the monitor light receiving element 12 are arranged horizontally (that is, parallel to the substrate 2), the structure shown in FIG.
The problem in the semiconductor laser device 50 according to (1) is solved. However, since the structure is complicated, the mounting cost cannot be significantly reduced.

[0010]

SUMMARY OF THE INVENTION The present invention reduces the cost in the process of mounting the monitor light-receiving element 12, and further provides a semiconductor laser device having a monitor light-receiving element for accurately capturing the monitor light into the light-sensitive layer. To provide
To aim.

[0011]

The present invention has been made to achieve the above object. An optical module according to claim 1 of the present invention comprises a light emitting element and a light receiving element for monitoring the optical output thereof, and a light receiving sensitivity layer formed in a plane shape of the monitor light receiving element has sensitivity on the substrate side. It is an optical module in which the light emitting element and the monitor light receiving element are horizontally mounted on a mounting substrate. In the optical module, an optical element such as a prism having a diffraction grating or a concavo-convex pattern is formed on the end surface of the monitor light incident side of the monitor light receiving element.

An optical module according to a second aspect of the present invention comprises a light emitting element and a light receiving element for monitoring the optical output thereof,
This is an optical module in which a light receiving sensitivity layer formed in a planar shape of a monitor light receiving element has a structure having sensitivity on the base material side, and the light emitting element and the monitor light receiving element are horizontally mounted on a mounting substrate. In the optical module, a rough surface is formed on the end surface of the monitor light incident side of the monitor light receiving element.

An optical module according to a third aspect of the present invention comprises a light emitting element and a light receiving element for monitoring the optical output thereof,
This is an optical module in which a light receiving sensitivity layer formed in a planar shape of a monitor light receiving element has a structure having sensitivity on the base material side, and the light emitting element and the monitor light receiving element are horizontally mounted on a mounting substrate. In the optical module, a refractive index distribution layer is formed in the base material portion of the monitor light receiving element.

An optical module according to a fourth aspect of the present invention comprises a light emitting element and a light receiving element for monitoring its optical output,
This is an optical module in which a light receiving sensitivity layer formed in a planar shape of a monitor light receiving element has a structure having sensitivity on the base material side, and the light emitting element and the monitor light receiving element are horizontally mounted on a mounting substrate. In the optical module, the surface of the mounting board on which the monitor light receiving element is mounted has a gradient with respect to the surface on which the light emitting element is mounted.

An optical module according to a fifth aspect of the present invention comprises a light emitting element and a light receiving element for monitoring its optical output,
This is an optical module in which a light receiving sensitivity layer formed in a planar shape of a monitor light receiving element has a structure having sensitivity on the base material side, and the light emitting element and the monitor light receiving element are horizontally mounted on a mounting substrate. The optical module has an antireflection film (AR coat) on the end face of the monitor light incident side of the monitor light receiving element,
A highly reflective film (HR coat) is applied to the opposite end face of the substrate.

[0016]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1. FIG. 1 is a partially cutaway side view of a semiconductor laser device 50 according to the first embodiment of the present invention. In FIG. 1, 2 is a substrate, 4 is a semiconductor LD element, and 6
Is an active layer of a semiconductor LD element, 8 is a substrate of a monitor light receiving element, 10 is a light receiving sensitivity layer of a monitor light receiving element, 12 is a monitor light receiving element, 14 is monitor light, and 16 is laser output light.

In the semiconductor laser device 50 of FIG. 1, the semiconductor LD element 4 and the monitor light-receiving element 12 are horizontally mounted on the mounting substrate 2. Further, in the light receiving sensitivity layer 10 formed in a flat shape in the monitor light receiving element 12, the base material 8 side is set to be the sensitivity surface. Here, on the end face of the substrate of the monitor light-receiving element 12, the diffraction grating 24, or
An optical element such as a prism having an uneven portion is formed.

Therefore, in the monitor light receiving element 12, the monitor light 14 is refracted at the end face of the base material 8 on the incident side of the monitor light 14 and guided to the light receiving sensitivity layer 10. Here, the monitor light receiving element 12 is mounted on the semiconductor LD element 4 at a position in the light receiving sensitivity layer 10 where a sufficient amount of light can be obtained to control the output of the semiconductor LD.

The semiconductor laser device 50 according to the first embodiment.
The manufacturing process will be outlined.

(1) First, an uneven pattern or a diffraction grating 24 is formed on the end face of the substrate of the monitor light receiving element 12. (2) Next, the semiconductor LD element 4 is mounted on the substrate 2. (3) Then, the monitor light-receiving element 12 is formed in the previous step (1).
The base material end surface side on which the concave-convex pattern, the diffraction grating 24, etc. are engraved is mounted so as to face the back light (monitor light) 14 of the semiconductor LD element 4. (4) With the above, the semiconductor laser device 50 according to the first embodiment is created.

In this embodiment, the semiconductor LD is formed on the substrate 2.
After the element 4 is mounted, the monitor light receiving element 12 is placed on the same plane with the mounting position of the semiconductor LD element 4 as a reference. Therefore, the semiconductor LD element 4 and the monitor light receiving element 1
It is possible to reduce the deviation that tends to occur at the time of alignment with the position 2, so that it is possible to prevent a decrease in optical output due to the positional deviation.

Embodiment 2. FIG. 2 is a partially cutaway side view of a semiconductor laser device 50 according to the second embodiment of the present invention. The second embodiment has substantially the same configuration as that of the semiconductor laser device 50 according to the first embodiment. Therefore, the same parts are designated by the same reference numerals and the description thereof is omitted, and different parts and parts are mainly described. Proceed.

Also in the semiconductor laser device 50 of FIG. 2, the semiconductor LD element 4 and the monitor light receiving element 12 are horizontally mounted on the mounting substrate 2, and the light receiving sensitivity is formed in a planar shape in the monitor light receiving element 12. In the layer 10, the base material 8 side is set to be the sensitivity surface. Further, in the second embodiment, the rough surface 26 is formed on the end surface of the base material of the monitor light-receiving element 12.

Therefore, in the monitor light receiving element 12 of the second embodiment, the monitor light 14 is scattered at the monitor light incident side end surface of the base material 8 which is the rough surface 26 and is guided to the light receiving sensitivity layer 10. Here, the monitor light receiving element 12 is mounted on the semiconductor LD element 4 at a position in the light receiving sensitivity layer 10 where a sufficient amount of light can be obtained to control the output of the semiconductor LD.

A semiconductor laser device 50 according to the second embodiment.
The manufacturing process will be outlined.

(1) First, the rough surface 26 is formed on the end surface of the substrate of the monitor light-receiving element 12. (2) Next, the semiconductor LD element 4 is mounted on the substrate 2. (3) Then, the monitor light-receiving element 12 is formed in the previous step (1).
The substrate end surface side on which the rough surface 26 is engraved is mounted so as to face the back light (monitor light) 14 of the semiconductor LD element 4. (4) Through the above steps, the semiconductor laser device 50 according to the second embodiment is created.

Also in this embodiment, the semiconductor LD is formed on the substrate 2.
After the element 4 is mounted, the monitor light receiving element 12 is placed on the same plane with the mounting position of the semiconductor LD element 4 as a reference. Therefore, the semiconductor LD element 4 and the monitor light receiving element 1
It is possible to reduce the deviation that tends to occur at the time of alignment with the position 2, so that it is possible to prevent a decrease in optical output due to the positional deviation.

Embodiment 3. FIG. 3 is a partially cutaway side view of a semiconductor laser device 50 according to the third embodiment of the present invention. The third embodiment also has substantially the same configuration as the semiconductor laser device 50 according to the first embodiment. Therefore, the same portions are denoted by the same reference numerals and the description thereof is omitted, and different portions and portions are mainly described. Proceed.

Also in the semiconductor laser device 50 of FIG. 3,
The semiconductor LD element 4 and the monitor light-receiving element 12 are horizontally mounted on the mounting substrate 2, and in the light-receiving sensitivity layer 10 formed in a flat shape in the monitor light-receiving element 12, the base material 8 side is the sensitivity surface. Is set. Further, in the third embodiment, a dopant for changing the refractive index is selectively expanded on the base material 8 of the monitor light receiving element 12 to form the refractive index distribution layer 28.

Therefore, in the monitor light receiving element 12 of the third embodiment, the monitor light 14 is refracted in the refractive index distribution layer 28 of the base material 8 of the monitor light receiving element 12, and the light receiving sensitivity layer 1 is obtained.
Lead to zero. Here, the monitor light receiving element 12 is mounted on the semiconductor LD element 4 at a position in the light receiving sensitivity layer 10 where a sufficient amount of light can be obtained to control the output of the semiconductor LD.

A semiconductor laser device 50 according to the third embodiment.
The manufacturing process will be outlined.

(1) First, on the end face of the substrate of the monitor light-receiving element 12, a dopant with a change in refractive index is selectively expanded. (2) Next, the semiconductor LD element 4 is mounted on the substrate 2. (3) Then, the monitor light-receiving element 12 is formed in the previous step (1).
The base material end face side in which the dopant of the refractive index change is engraved is mounted so as to face the back light (monitor light) 14 of the semiconductor LD element 4. (4) With the above, the semiconductor laser device 50 according to the third embodiment is produced.

Also in this embodiment, the semiconductor LD is formed on the substrate 2.
After the element 4 is mounted, the monitor light receiving element 12 is placed on the same plane with the mounting position of the semiconductor LD element 4 as a reference. Therefore, the semiconductor LD element 4 and the monitor light receiving element 1
It is possible to reduce the deviation that tends to occur at the time of alignment with the position 2, so that it is possible to prevent a decrease in optical output due to the positional deviation.

Fourth Embodiment 4 (1) and 4 (2) are partially cutaway side views of the semiconductor laser device 50 according to the fourth embodiment of the present invention. The fourth embodiment also has substantially the same configuration as the semiconductor laser device 50 according to the first embodiment, and therefore, the same portions are denoted by the same reference numerals and the description thereof is omitted.
The explanation will focus on different parts and places.

The semiconductor laser device 50 shown in FIGS. 4A and 4B.
However, the semiconductor LD element 4 and the monitor light receiving element 12 are mounted on the mounting substrate 2. However, the substrate 2 has a V-shaped groove (see FIG. 4 (1)) or a chamfered portion (see FIG. 4 (2)) on the surface.
And the like, and the monitor light receiving element 12 is mounted on these inclined surfaces.

On the other hand, the light receiving sensitivity layer 10 formed in a planar shape in the monitor light receiving element 12 is set so that the base material 8 side becomes the sensitivity surface also in the fourth embodiment.

Therefore, in the monitor light receiving element 12 of the fourth embodiment, the monitor light 14 is refracted at the incident side end surface of the base material 8 and guided to the light receiving sensitivity layer 10. Here, the monitor light-receiving element 12 includes the semiconductor L in the light-receiving sensitivity layer 10.
The semiconductor LD device 4 is mounted at a position where a sufficient amount of light can be obtained to control the output of D.

A semiconductor laser device 50 according to the fourth embodiment.
The manufacturing process will be outlined.

(1) First, a V-shaped groove (see FIG. 4) is formed on the substrate 2.
(1)) or a chamfer (see FIG. 4B) is formed. (2) Next, the semiconductor LD element 4 is mounted on the substrate 2. (3) Then, the monitor light-receiving element 12 is formed in the previous step (1).
It is mounted on the inclined surface of the V-shaped groove / chamfered part formed in (4). (4) With the above, the semiconductor laser device 50 according to the fourth embodiment is produced.

Also in this embodiment, the semiconductor LD is formed on the substrate 2.
After the element 4 is mounted, the monitor light receiving element 12 is placed on the same plane with the mounting position of the semiconductor LD element 4 as a reference. Therefore, the semiconductor LD element 4 and the monitor light receiving element 1
It is possible to reduce the deviation that tends to occur at the time of alignment with the position 2, so that it is possible to prevent a decrease in optical output due to the positional deviation.

Further, according to the semiconductor laser device 50 of the present embodiment, the reflected return light 30 from the end face of the substrate of the monitor light-receiving element 12 and the submount 20 has the direction of the incident light (monitor light 14). Because it is different, the reflected return light 3 again
0 can be suppressed from entering the semiconductor LD element 4, and a stable laser light output can be obtained.

Fifth Embodiment FIG. 5 is a partially cutaway side view of a semiconductor laser device 50 according to the fifth embodiment of the present invention. The fifth embodiment also has substantially the same configuration as that of the semiconductor laser device 50 according to the first embodiment. Therefore, the same parts are designated by the same reference numerals and the description thereof is omitted, and different parts and parts are mainly described. Proceed.

Also in the semiconductor laser device 50 of FIG. 5, the semiconductor LD element 4 and the monitor light receiving element 12 are mounted on the mounting substrate 2. However, the substrate 2 has two pairs of Au bumps 32 having different sizes on the surface thereof, and the monitor light-receiving element 12 is mounted on the Au bumps 32 with an inclination with respect to the substrate 2.

On the other hand, the light receiving sensitivity layer 10 formed in a planar shape in the monitor light receiving element 12 is set so that the base material 8 side becomes the sensitivity surface also in the fifth embodiment.

Therefore, also in the monitor light-receiving element 12 of the fifth embodiment, similarly to the fourth embodiment, the monitor light 14 is refracted at the end face of the monitor light-incident side of the monitor light-receiving element 12, and the light-receiving sensitivity layer is formed. Guided to 10. Here, the monitor light-receiving element 12 has a position in the light-receiving sensitivity layer 10 where a sufficient amount of light can be obtained to control the output of the semiconductor LD.
It is mounted on the semiconductor LD element 4.

A semiconductor laser device 50 according to the fifth embodiment.
The manufacturing process will be outlined.

(1) First, the semiconductor LD element 4 is formed on the substrate 2.
Implement. (2) Next, two pairs of Au bumps 32 having different sizes are formed on the substrate 2 at the mounting positions of the monitor light receiving elements 12. (3) Subsequently, the monitor light-receiving element 12 is formed in the previous step (2).
It is mounted on the Au bump 32 formed in. Semiconductor LD
Since the pair of Au bumps 32 closer to the element 4 is smaller and the pair farther away is large, the monitor light-receiving element 12 is formed.
Are mounted to be inclined with respect to the substrate 2. (4) With the above, the semiconductor laser device 50 according to the fifth embodiment is produced.

In the above manufacturing process, the position of the monitor light receiving element 12 with respect to the semiconductor LD element 4 can be controlled by controlling the size of the paired Au bumps 32.

Also in this embodiment, the semiconductor LD is formed on the substrate 2.
After the element 4 is mounted, the monitor light receiving element 12 is placed on the same plane with the mounting position of the semiconductor LD element 4 as a reference. Therefore, the semiconductor LD element 4 and the monitor light receiving element 1
It is possible to reduce the deviation that tends to occur at the time of alignment with the position 2, so that it is possible to prevent a decrease in optical output due to the positional deviation.

Also in the semiconductor laser device 50 according to the present embodiment, the reflected return light 30 from the end face of the substrate of the light receiving element 12 for monitoring and the submount 20 is different in direction from the incident light (monitor light 14). Therefore, the reflected return light 30 can be prevented from entering the semiconductor LD element 4 again, and a stable laser light output can be obtained.

Sixth Embodiment FIG. 6 is a partially cutaway side view of a semiconductor laser device 50 according to the sixth embodiment of the present invention. The sixth embodiment also has substantially the same configuration as the semiconductor laser device 50 according to the first embodiment. Therefore, the same portions are denoted by the same reference numerals and the description thereof is omitted, and different portions and portions will be mainly described. Proceed.

Also in the semiconductor laser device 50 of FIG. 6, as in the first embodiment, the semiconductor LD element 4 and the monitor light receiving element 12 are horizontally mounted on the mounting substrate 2, and within the monitor light receiving element 12. In the light receiving sensitivity layer 10 formed in a flat shape, the base material 8 side is set to be the sensitivity surface. Further, in the sixth embodiment, with respect to the monitor light-receiving element 12, A is formed on the end surface of the incident side substrate of the back light (monitor light) 14.
An R coat (antireflection film) 34 is applied, and an HR coat (high reflection film) 36 is applied to the end face of the base material on the opposite side.

Therefore, in the monitor light receiving element 12 of the sixth embodiment, the monitor light 1 incident on the monitor light receiving element 12 is detected.
4 is confined in the light receiving element 12 for monitoring, and is efficiently taken into the light receiving sensitivity layer 10. Here, the monitor light-receiving element 12 has the semiconductor LD at a position in the light-sensitivity layer 10 where a sufficient amount of light can be obtained to control the output of the semiconductor LD.
It is mounted on the element 4.

A semiconductor laser device 50 according to the sixth embodiment.
The manufacturing process will be outlined.

(1) First, AR coats 34 and H are respectively provided on the end faces of two base materials of the monitor light receiving element 12 which face each other.
The R coat 36 is formed. (2) Next, the semiconductor LD element 4 is mounted on the substrate 2. (3) Then, the monitor light-receiving element 12 is formed in the previous step (1).
On the end face side of the base material on which the AR coat 34 is applied, the semiconductor LD
It is mounted so as to face the back light (monitor light) 14 of the element 4. (4) With the above, the semiconductor laser device 50 according to the sixth embodiment is produced.

Also in this embodiment, the semiconductor LD is formed on the substrate 2.
After the element 4 is mounted, the monitor light receiving element 12 is placed on the same plane with the mounting position of the semiconductor LD element 4 as a reference. Therefore, the semiconductor LD element 4 and the monitor light receiving element 1
It is possible to reduce the deviation that tends to occur at the time of alignment with the position 2, so that it is possible to prevent a decrease in optical output due to the positional deviation.

In addition to the sixth embodiment, in the present invention (for example, the first to fifth embodiments), the electrode section is installed on the surface of the monitor light receiving element 12, and the wire bonder wiring is performed. Wiring is relatively easy because it can be performed. FIG. 7 is a perspective view of the semiconductor laser device 50 according to the present invention, which is provided with the wire bonder wiring.

[0059]

As described above, according to the present invention, the number of assembling steps can be reduced when mounting the light receiving element for the optical output monitor.
It is possible to significantly reduce the cost associated with mounting. In particular, according to the optical module of claim 4 of the present invention, the reflected return light from the end face of the base material of the light receiving element for monitoring is the semiconductor L.
It is also possible to suppress entry into D and obtain a stable laser light output.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway side view of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 3 is a partially cutaway side view of a semiconductor laser device according to a third embodiment of the present invention.

FIG. 4 is a partially cutaway side view of a semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 5 is a partially cutaway side view of a semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 6 is a partially cutaway side view of a semiconductor laser device according to a sixth embodiment of the present invention.

FIG. 7 is a perspective view of a semiconductor laser device according to the present invention in which wire bonder wiring is provided.

FIG. 8 is (1) a perspective view and (2) a partially cutaway side view of an example of a semiconductor laser device according to a conventional technique.

FIG. 9 is a partially cutaway side view of another example of the semiconductor laser device according to the related art.

[Explanation of symbols]

2 substrate, 4 semiconductor laser diode element, 6
Semiconductor laser diode element active layer, 8 monitor light receiving element base material, 10 monitor light receiving element light receiving sensitivity layer,
12 light receiving element for monitor, 14 monitor light, 16
Laser output light, 24 diffraction grating, 26 rough surface, 28
Refractive index distribution layer, 30 reflected return light, 32 Au bumps, 34 antireflection film (AR coat), 36 high reflection film (HR coat), 50 semiconductor laser device,
102 semiconductor LD subcarrier, 104 light receiving element submount for monitor, 106 spacer, 10
8 Reflective film.

Continued front page    (72) Inventor Kiyohide Sakai             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Hiroshi Izawa             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Akira Takemoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Tatsuo Hatta             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 5F073 AB25 BA02 EA15 FA04 GA12                 5F088 BA16 BA18 BB01 DA17 DA20                       JA05 JA10 JA11 JA20                 5F089 AA01 AB03 AC02 AC11 AC13                       CA15 GA01 GA10

Claims (5)

[Claims] 1. An optical module comprising a light emitting element and a light receiving element for monitoring an optical output thereof, wherein a light receiving sensitivity layer formed in a plane shape of the light receiving element for an optical output monitoring has a structure having a sensitivity on a substrate side, A prism having a diffraction grating or a concavo-convex pattern on an end face of a monitor light incident side substrate of the light output monitoring light receiving element, the element and the light output monitoring light receiving element being horizontally mounted on a mounting substrate. An optical module in which optical elements such as are formed. 2. An optical module comprising a light emitting element and a light receiving element for monitoring an optical output thereof, wherein a light receiving sensitivity layer formed in a plane shape of the light receiving element for an optical output monitoring has a structure having sensitivity on the substrate side, An element and the light output monitor light-receiving element are horizontally mounted on a mounting substrate, wherein the light-output monitor light-receiving element has a rough surface at the end face of the incident side of the monitor light. module. 3. An optical module comprising a light emitting element and a light receiving element for monitoring the light output thereof, wherein a light receiving sensitivity layer formed in a plane shape of the light receiving element for the light output monitoring has a structure having sensitivity on the substrate side, An element and the light output monitoring light receiving element are horizontally mounted on a mounting substrate, and a dopant for changing the refractive index is injected into the base material of the light output monitoring light receiving element, and the refractive index distribution is applied to the base material. An optical module in which layers are formed. 4. An optical module comprising a light emitting element and a light receiving element for monitoring an optical output thereof, wherein a light receiving sensitivity layer formed in a plane shape of the light receiving element for an optical output monitoring has a structure having sensitivity on the base material side, Element and the light output monitor light receiving element are mounted horizontally on a mounting board, and the surface of the mounting board on which the light output monitoring light receiving element is mounted has a slope with respect to the surface on which the light emitting element is mounted. An optical module characterized by this. 5. An optical module comprising a light emitting element and a light receiving element for monitoring an optical output thereof, wherein a light receiving sensitivity layer formed in a planar shape of the light receiving element for an optical output monitoring has a structure having a sensitivity on a substrate side, An optical element and the above-mentioned light output monitoring light receiving element are horizontally mounted on a mounting board, and an antireflection film (AR coat) is provided on an end surface of a light incident side of a monitor light of the light output monitoring light receiving element, and an opposite side thereof. An optical module in which a high reflection film (HR coat) is applied to the end surface of the substrate.