JP3153892B2 - Optical module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module for optical transmission used for optical communication and the like.

[0002]

2. Description of the Related Art FIG. 3 shows the internal configuration of a conventional optical module of this type. A pair of electrodes 12 and 13 are formed on a silicon substrate 11, and a laser diode (hereinafter, referred to as LD) 14 is mounted on one of the electrodes 12. The LD 14 is face-down (the light-emitting portion is down, that is, the electrode 12 side), and its signal electrode is mounted by soldering to the electrode 12, while the GND electrode located on the upper surface is electrically connected to the electrode 13 by wire bonding. You. In the figure, reference numeral 15 denotes a wire (lead wire).

Light emitted from the front surface of the LD 14 enters an optical fiber 16. At this time, the LD 14 and the optical fiber 16
In order to obtain sufficient light coupling efficiency, extremely high-precision alignment (optical axis alignment) on the order of μm is required. Therefore, a V-groove 17 extending from the edge to the front surface of the LD 14 is formed on the plate surface of the silicon substrate 11 with high precision by anisotropic etching, and one end of the optical fiber 16 is accommodated in the V-groove 17. By holding the position
The configuration realizes accurate alignment between D14 and the optical fiber 16.

On the other hand, a photodetector (hereinafter, referred to as PD) 18 for receiving light emitted from the rear surface is provided on the rear surface side of the LD 14, and the backward emitted light is monitored by the PD 18. The monitor output of PD 18 is APC (Au
LD14 by a circuit (not shown)
, So that the light amount (power) of the LD 14 is controlled to be constant. In addition, PD18
Are mounted on a submount 19, and the submount 19 is mounted on a base substrate 21 together with the silicon substrate 11.

FIG. 4 shows an external shape of an optical module 23 in which the above-described configuration is housed in a package 22. The optical fiber 16 is led out of the package 22, and the package 22 has a plurality of terminal pins 24 for electrical connection.

[0006]

By the way, as shown by the arrow in FIG. 5, the light emitted from the LD 14 spreads, for example, as much as 40 ° in full-angle and diffuses greatly. On the other hand, the distance between the LD 14 and the light receiving surface of the PD 18 is, for example, the silicon substrate 11
It is necessary to secure about 1 mm from the problem of mounting the LD 14 by forming the electrode 12 and avoiding the edge portion where chipping easily occurs, and the mounting problem of the PD 18 such as preventing the PD 18 from colliding with the silicon substrate 11. There is.

Further, in order to perform good feedback control by the APC circuit so that the light amount of the LD 14 becomes constant, it is necessary to use a monitor PD 18 having a band equivalent to the transfer speed of the LD 14, In this case, for example, a PD capable of handling high-speed data exceeding 1 Gbps
In 18, the diameter of the light receiving section 18 a is extremely small, about φ50 μm.

Therefore, these LD emission angles of 40 °, LD ·
Due to the dimensional relationship such as the distance between PDs of 1 mm and the PD light receiving diameter of φ50 μm, the PD 18 cannot effectively receive the light emitted from the LD 14, and the amount of received light is greatly reduced, thereby causing unstable operation or malfunction of the APC circuit. Had become. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical module capable of securing a light receiving amount of a PD and stably operating an APC circuit in view of the above-described problems.

[0009]

According to the first aspect of the present invention, a structure is adopted in which forward emitted light from a laser diode is made incident on an optical fiber, and backward emitted light from the laser diode is received and monitored by a photodetector. In an optical module, a laser diode is mounted on a silicon substrate, and is anisotropically etched before and after the laser diode on the plate surface of the silicon substrate, extending in the front-rear direction and reaching the edge of the silicon substrate.
A first V-groove and a second V-groove formed on one line are formed, one end of the optical fiber is positioned and held in the first V-groove, and a photodetector is arranged on an edge of the second V-groove. .

Further , the width of the second V-groove is made substantially equal to the diameter of the light receiving portion of the photodetector.

[0011]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows the internal configuration of an embodiment of the present invention. Parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted. In this example, V-grooves 31 are also provided behind the LD 14, that is, before and after the LD 14 on the plate surface of the silicon substrate 11, V-grooves 17 and 31 extending in the front-rear direction and reaching the edges of the silicon substrate 11, respectively. It is assumed to have been formed. P
D18 is mounted on the submount 19,
a is disposed so as to be located close to the edge of the V-groove 31.

According to this configuration, of the backward emission light emitted from the rear surface side of the LD 14 mounted face-down, the light incident on the V-groove 31 is, as shown by an arrow in FIG. Reflected by the wall surface, ie, in the lateral direction (V-groove 3
1 is prevented, the amount of light received by the PD 18 is greatly increased as compared with the case where the V-groove 31 is not provided. Therefore, the PD 18 can secure a required amount of received light.

The case where the width of the V-groove 31 is set to a value substantially equal to the diameter of the light receiving portion 18a of the PD 18 is particularly effective for increasing the amount of light. V-groove 1 into silicon substrate 11
The electrodes 7 and 31 are formed by wet etching such as KOH, and the electrodes 12 and 13 are formed on the silicon substrate 11 by sputtering Ti / Pt / Au or Cr / Au. The LD 14 is mounted, for example, by soldering Au / Sn or the like on the electrode 12 by vapor deposition, and the optical fiber 16 is fixed to the V-groove 17 using an adhesive such as a UV adhesive or solder. V-grooves 17, 31,
Patterning of the electrodes 12, 13 and the solder or the like on the electrodes 12 can all be performed by photolithography, so that mutual positioning can be performed with high accuracy.

The optical module shown in FIG. 1 is housed in a package 22. That is, the optical module has the same appearance as that shown in FIG. In the above example, PD1
8 is mounted on the submount 19,
Is fixed to the base substrate 21, but it is also possible to mount the PD 18 directly on the silicon substrate 11, for example.

[0015]

As described above, according to the present invention, the light guide V-groove 31 provided in the silicon substrate 11 allows the
Lateral diffusion of the backward emission light of D14 is suppressed, and the light is effectively P
Since the light is guided to D18, the PD 18 can obtain a sufficient amount of light. Therefore, the APC circuit using the PD 18 can be operated well.

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining an embodiment of the present invention.

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a perspective view showing the internal configuration of a conventionally proposed optical module.

FIG. 4 is a perspective view showing an external shape of the optical module.

FIG. 5 is a plan view of FIG. 3;

Claims (1)

(57) [Claims] 1. An optical module having a structure in which forward emitted light from a laser diode is made incident on an optical fiber, and backward emitted light from the laser diode is received and monitored by a photodetector, wherein the laser diode is mounted on a silicon substrate. The laser diode on the surface of the silicon substrate before and after the laser diode, extending in the front-rear direction and reaching the edge of the silicon substrate , respectively, by anisotropic etching.
A first V-groove and a second V-groove formed on the same line , one end of the optical fiber is positioned and held in the first V-groove, and the edge of the second V-groove is An optical module comprising a photodetector.