KR20160025149A

KR20160025149A - Laser diode module

Info

Publication number: KR20160025149A
Application number: KR1020140111747A
Authority: KR
Inventors: 강승구; 윤재춘; 김대경; 김상철; 이현주
Original assignee: (주)코셋
Priority date: 2014-08-26
Filing date: 2014-08-26
Publication date: 2016-03-08

Abstract

The present invention relates to a laser diode module, comprising: a laser diode disposed in one area of a mount; a trench formed by cutting the mount in another area of the mount; a monitoring photodiode disposed inside the trench; And a mirror having a reflection surface for reflecting the light traveling to the rear side to the monitoring photodiode and transmitting the reflected light.

Description

Laser diode module {LASER DIODE MODULE}

The present invention relates to a laser diode module, and more particularly, to a laser diode module that proposes a new module structure in which a monitoring photodiode is disposed without using a laser heat sink.

Generally, a laser (Light Amplification by Stimulated Emission of Radiation (LASER)) is a light emitted from a medium by an external stimulus and amplified by a resonator.

Such a laser is composed of an amplification medium, a resonator, and a pumping source, and is classified into a gas laser, a solid laser, a semiconductor laser, and an optical fiber laser depending on the kind of the medium.

In particular, lasers are used in various industrial fields because they are easy to use, clean, and provide rapid processing results, and new industrial lasers are being developed steadily due to the increased demand for high power lasers.

Fiber-optic lasers have unprecedented optical-to-optical conversion efficiency among solid-state lasers, have good beam quality, and can form a resonator in the optical fiber itself. Therefore, And thus it has been attracting attention as an industrial light source.

The development of optical fiber lasers in the present market is being developed as a high power continuous operation laser, a pulse operation laser, and a light source for high speed communication. For many years, many companies have been making KW class lasers for industrial use.

In the manufacture of laser diode modules for high-speed optical communication, optical signals emitted to the front side of the laser diode are optically coupled to the optical fiber through the lens as much as possible, Or as a signal for high-speed optical communication.

On the other hand, the signal emitted from the back side of the laser diode is detected by using a monitoring photodiode (monitoring photodiode), and then it is monitored whether the laser diode, which is a core device, is normally operating, And a feedback function that keeps the characteristic of the variable laser diode constant.

Therefore, the monitoring photodiode is a key element in the laser diode module, which is as important as the laser diode.

Hereinafter, conventional techniques for installing a monitoring photodiode in a laser diode module will be described.

Figure 1 is a schematic perspective view of a laser diode module of U.S. Patent No. 6,837,627, one of the prior art.

Referring to FIG. 1, a surface light receiving monitoring photodiode 42 is attached to a monitoring photodiode block 36 and used. In this case, a die bonding process for accurately attaching the monitoring photodiode block 36 to the substrate 32, is added.

In this case, the light receiving height of the monitoring photodiode 42 attached to the monitoring photodiode block 36 should be matched with the light emitting height of the laser diode 34, so that the laser diode 34 is attached to the additional laser diode heat sink . Therefore, there is a problem that additional parts and additional processes are required.

If the laser heat sink 31 is used, the length of a bonding wire (not shown) for connection between the laser diode 34 and the high-speed transmission line becomes long, which is disadvantageous for high-speed operation.

In addition, the monitoring photodiode block 36 is mainly made of ceramics, and there is a problem that a high-quality manufacturing technique for forming a bonding pad and a pattern is required, which is expensive.

FIG. 2 is a schematic perspective view of a laser diode module of US Pat. No. 5,005,178, another of the prior art.

Referring to Fig. 2, the monitoring photodiode PD is in the form of a request to the side surface of the ceramic submount 2 disposed on the rear surface of the laser diode LD. This approach corresponds to the most common way to arrange a monitoring photodiode.

However, this method requires a separate process from a separate component called the ceramic submount 2, which is costly and requires expensive fabrication techniques for forming bonding pads and patterns, which is expensive.

Also, according to this method, the length of the bonding wire (not shown) for connecting the laser diode 34 and the high-speed transmission line becomes long due to the structure using the laser heat sink, which is disadvantageous for high-speed operation.

U.S. Patent No. 6,837,627 U.S. Patent No. 5,005,178

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new module structure for disposing a monitoring photodiode without using a laser heat sink.

Another object of the present invention is to provide a laser diode module capable of reducing the number of components, simplifying the process, and reducing the cost.

It is still another object of the present invention to provide a laser diode module capable of increasing the optical coupling efficiency by using a low-cost and large area light receiving monitoring photodiode.

According to an aspect of the present invention, there is provided a laser diode module comprising: a laser diode disposed in a region of a mount; a trench formed by cutting the mount into another region of the mount; And a mirror having a reflection surface for reflecting and transmitting the light traveling to the rear surface of the laser diode to the monitoring photodiode.

Preferably, the depth of the trench is greater than the height of the monitoring photodiode so that when the monitoring photodiode is disposed within the trench and light traveling to the backside of the laser diode is transmitted through the mirror, the influence of external light is reduced .

On the other hand, the reflection surface of the mirror may completely cover the light receiving portion of the monitoring photodiode with respect to the plan view. In this case, the light receiving efficiency can be improved.

Preferably, the laser diode and the monitoring photodiode are die-bonded to the mounting surface and to the interior of the trench of the mount, respectively.

Also, the electrodes disposed on the surface of the mount, the laser diode, the electrodes disposed on the surface of the mount, and the monitoring photodiode are respectively wire-bonded. With such a configuration, the positions where the wire bonding is performed are made to have similar heights, and the distance for wire bonding can be reduced, so that the defective rate can be reduced and it is advantageous for high-speed operation.

According to the present invention, by using a low-cost surface light monitoring photodiode, it is possible to simplify die bonding and wire bonding processes without using an expensive monitoring photodiode block and an expensive laser diode heat sink, There is an effect that can be achieved.

Further, according to the present invention, since the laser heat sink is not used, the bonding wire can be shortened, and the laser diode can be positioned near the transmission line, so that the performance improvement advantageous to high-speed operation can be obtained.

FIGS. 1 and 2 are perspective views illustrating a conventional laser diode module.
3 is a perspective view of a laser diode module according to an embodiment of the present invention.
FIG. 4A is a plan view of a laser diode module according to an embodiment of the present invention, and FIG. 4B is a sectional view of a laser diode module according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will be more apparent from the following detailed description taken in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification. "And / or" include each and every combination of one or more of the mentioned items.

3 is a perspective view illustrating a laser diode module according to an embodiment of the present invention. FIG. 4A is a plan view of a laser diode module according to an embodiment of the present invention, and FIG. 4B is a sectional view of a laser diode module according to an embodiment of the present invention.

The laser diode module of the present embodiment includes a laser diode 1 and a monitoring photodiode 3 disposed inside a trench 11 of a mount (for example, Silicone Optical Bench) 2 and a rear surface of the laser diode 1 And a mirror 4 for reflecting and transmitting the proceeding light to the monitoring photodiode 3.

The laser diode 1 is bonded directly onto the mount 2 and does not require a heat sink. This is one of the main characteristic features of the present invention and will be described later in detail.

The monitoring photodiode 3 may be horizontally attached to the interior of the trench of the mount 2.

The trench 11 is dug deeper than the thickness of the monitoring photodiode 3 and the monitoring photodiode 3 is die bonded to the plane in order to sense light emitted from the rear surface of the laser diode 1. [ Thereafter, the mirror 4 capable of turning the backward proceeding light of the laser diode 1 into the monitoring photodiode 3 is positioned.

The lower view of Figure 3 shows the monitoring photodiode 3. Referring to this figure, the monitoring photodiode 3 can lower the overall laser diode module price by employing a relatively low-cost surface-receiving monitoring photodiode.

According to this structure, there is no LD heat sink for mounting the laser diode 1 in the prior art. Generally, since the electrode for driving the laser diode 1 is present on a lower substrate (mount surface) than the LD heat sink, the bonding wire naturally lengthens in the presence of the LD heat sink. Nevertheless, in many cases, a heat sink for a laser diode was installed in order to match the height with the monitoring photodiode (3). However, when the bonding wire becomes long, it becomes disadvantageous for high-speed operation. Therefore, in the present invention, it is devised to eliminate the separate LD heat sink without disposing the laser diode 1 on the LD heat sink. In the embodiment of the present invention, a material serving as a heat sink for the mount 2 is employed and a separate LD heat sink is not used.

In the structure in which the LD heat sink is eliminated, since the laser diode can be positioned near the transmission line, the distance of the bonding wire is shortened, so that the performance improvement advantageous to high-speed operation can be obtained.

On the other hand, the monitoring photodiodes 3 are also disposed inside the trenches 11 so that the bonding pads 9 of the monitoring photodiodes 3 are not significantly different from each other, though the height of the mounts 2 is slightly lower μm). Therefore, when the bonding wire is applied to the bonding pad 9, the distance of the wire is shortened, which is convenient.

On the other hand, the mirror 4 is required to align vertically and effectively to transmit the light to the monitoring photodiode 3 inside the trench 11. In the embodiment of the present invention, the mirror 4 can be positioned after the monitoring photodiode 3 is disposed in the trench 11. The mirror can use a 45-degree mirror, but a mirror can be made so that the reflection surface has various angles so that the light transmitted to the monitoring photodiode 3 can be maximized, and one mirror can be a polygonal or multi- As shown in Fig.

The trench 11 according to the present embodiment is configured to be made at the same time when the collimating lens 6 is placed in a V-groove, so that no separate process is required. Thus, the process for fabricating the trench 11 substantially eliminates the need for additional cost and process, and thus is very suitable for the purpose of simplifying the process of the present invention. In addition, since the process of manufacturing the trench 11 uses semiconductor wet etching, the accuracy can be adjusted in units of um and the bottom can be controlled flat.

1, the monitoring photodiode block 36 is manufactured by using a ceramic. In this case, it is difficult to provide a step difference. In the case of using a silicon substrate or the like, the trench and the lens 6 are raised in a single step It is possible to make V-grooves and accurate position, so it is advantageous for LD bonding, m-PD bonding and lens attaching process requiring sub-micron precision. .

Referring to FIG. 4A, the mirror 4 preferably has a structure in which the reflecting surface completely covers the light receiving portion 8, which is the light detecting region of the monitoring photodiode 3, with reference to the plan view. In this case, when the electrode pad 9 is formed separately from the light receiving unit 8, the monitoring photodiode 3 can be formed by wire bonding lines between the electrode pad 9 and the other electrodes GND and mPD- May not be reduced.

1 and 2, the laser diode structure of the present invention does not include a heat sink for LD and a block for a monitoring photodiode, simplifying parts and making it possible to manufacture at low cost.

On the other hand, it is possible to use die bonding, which is a relatively simple process when attaching the monitoring photodiode 3 inside the trench 11 and attaching the laser diode to the mount 2.

4A, the GND terminal is a terminal for wiring with the ground electrode of the laser diode 1 and the monitoring photodiode 3, and the LD- terminal and the LD + terminal are terminals for wiring the signal line to the laser diode 1 And mPD- is a terminal for wiring with the anode electrode of the monitoring photodiode 3.

Hereinafter, a method of manufacturing a laser diode module according to an embodiment of the present invention will be described.

First, a trench 11 is formed in a mount 2, and a laser diode 1, a monitoring photodiode 3, and the like are bonded by die bonding to a mount 2 on which a trench 11 is formed.

Next, a lens 6 for making the front propagating light 7 of the laser diode 1 into parallel light is attached, and the back light 5 of the laser diode 1 is reflected by the light receiving portion of the monitoring photodiode 3 8 on the monitoring photodiode 3 by attaching the mirror 4 having the reflection surface to the monitoring photodiode 3 to complete the COS (Chip on Submount).

Next, the TEC 13 is attached to the inside of the metal package 14, the COS (Chip on Submount) assembled from the front is attached to the TEC 13, and then the isolator 12 is attached.

Then, the front light 7 emitted from the laser diode is guided to the optical fiber as much as possible by aligning the receptacle 16 in which the fiber stub 18 with the optical fiber inserted therein is aligned by applying current to the laser diode 1 And laser welding is performed via a welding ring 17 to fix the receptacle 16. Finally, the lid is covered to complete the laser diode module.

Although the preferred embodiments of the laser diode module according to the present invention have been described above, the present invention is not limited thereto, and various modifications and changes may be made within the scope of the claims, And this also belongs to the present invention.

1: Laser diode 2: Mounted
3: Monitoring photodiode 4: Mirror
5: Rear progressive light 6: Lens
7: front progress light 8: light reception area
9: bonding pad 10: focusing lens
11: monitoring photodiode trench 12: isolator
13: TEC 14: Package
15: Lead pin 16: Receptacle
17: Welding Ring 18: Fiber stub

Claims

In a laser diode module,
A laser diode disposed in one region of the mount;
A trench formed by cutting the mount in another area of the mount;
A monitoring photodiode disposed within the trench; And
And a mirror having a reflecting surface for reflecting light propagating to a rear surface of the laser diode to a monitoring photodiode and transmitting the reflected laser light.

The method according to claim 1,
Wherein the depth of the trench is greater than the height of the monitoring photodiode.

The method according to claim 1,
Wherein the reflection surface of the mirror completely covers the light receiving portion of the monitoring photodiode with respect to the plan view.

The method according to claim 1,
Wherein the laser diode and the monitoring photodiode are die-bonded to the mount surface and the trench of the mount, respectively.

The method according to claim 1,
Wherein the electrodes disposed on the surface of the mount, the laser diode, the electrodes disposed on the surface of the mount, and the monitoring photodiode are wire-bonded, respectively.