JPS60411A - Laser module device - Google Patents

Abstract

PURPOSE:To attenuate a reflected light from an optical fiber incident end and a condensing lens incident end by placing an optical attenuator between a semiconductor laser and a condensing lens, and inclining diagonally the semiconductor laser against an optical axis in the direction parallel to its hetero junction surface. CONSTITUTION:An incident end face (e) of an optical fiber 4 is polished diagonally. A cylindrical condensing lens 5 is formed so that is refractive index becomes smaller gradually extending from the center axis to the outside circumference. An optical attenuator 6 whose attenuation ratio is about 1/10 is placed in the vicinity of the incident end of the lens 5. As for a semiconductor laser 7, a hetero junction surface 9 of a chip 9 is on a plane containing the lens 5, and its optical axis is inclined and placed diagonally about 10 deg. against the optical axis of the lens 5. In this way, an emitted light of the laser 7 is condenced to the incident surface of the fiber 4 by the lens 5, and made incident efficiently to the fiber 4. On the other hand, a light reflected by the end face (e) and an incident and emitting end face C of the lens 5 is attenuated by the attenuator 6. Also, a light reflected by the end face C and the surface of the attenuator 6 does not return to the laser 7. Therefore, deterioration of a characteristic of the laser 7 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laser module device used for optical communications and the like.

Structure of a conventional example and its problems FIG. 1 shows a conventional laser module device. The configuration of this conventional example will be explained below with reference to FIG. 1.

In FIG. 1, reference numeral 1 denotes a cylindrical optical core, and the input end surface of this optical fiber 10 is polished obliquely. 2 is a cylindrical condensing lens located on the same optical axis as the above-mentioned optical fiber.
A hemisphere with a radius approximately equal to the radius of the cylindrical portion is integrally formed. 3 is a semiconductor laser located on the same optical axis as the optical fiber 1 and the condenser lens 2. In addition, the above-mentioned condensing lens 2
is a cylindrical condensing lens whose refractive index decreases from the central axis toward the outer periphery.

Next, the operation of the above conventional example will be explained. In FIG. 1, the emitted light of the semiconductor laser 3 is condensed by the condensing lens 2 and is efficiently incident on the optical core ino (l). C
) to prevent the light from returning to the semiconductor layer 3, the incident end (C) is semicircular. Furthermore, the input end face (d) of the optical fiber 1 is aligned with the optical axis a around 1O0 so that the reflected light at the input end (d) of the optical fiber 1 is re-focused by the ballistic optical lens 2 and does not return to the semiconductor laser 3. It is slanted.

However, in the above conventional example, even if the input end surface of the optical fiber 1 is made oblique and the input end of the condenser lens 2 is made semicircular, the light is practically condensed. The reflected light from the output end (b) of the lens and the reflected light from a part of the semicircle return onto the chip of the semiconductor laser 3, which has the disadvantage that it is not possible to completely eliminate the characteristic deterioration of the semiconductor laser 3 due to the reflected light. In addition, the spherical condensing lens in which the tip of the condensing lens 2 has a semicircular shape has drawbacks such as being difficult to process.

Purpose of the Invention The present invention aims to eliminate the drawbacks of the above-mentioned conventional example, and aims to prevent reflected light from the input end face of an optical fiber and the input/output end face of a condensing lens from returning onto a semiconductor laser chip. It is.

Structure of the Invention In order to achieve the above-mentioned objects, the present invention includes (1) an optical attenuator is placed between the semiconductor laser and the condensing lens, and the semiconductor laser is tilted obliquely to the optical axis in a direction parallel to its heterojunction surface; This provides the effect of preventing reflected light from the input end of the optical fiber and the output end of the condenser lens from returning onto the semiconductor laser chip.

DESCRIPTION OF THE EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, 4 is an optical fiber whose input end face (e) is obliquely polished. Reference numeral 5 denotes a cylindrical condensing lens, and the condensing lens 5 is a lens whose refractive index decreases from the central axis toward the outer periphery. Reference numeral 6 denotes an optical attenuator with an attenuation ratio of around 1710, which is placed close to the entrance edge of the condenser lens 5; 7, the heterojunction surface is on a plane that includes the condenser lens 5; the optical axis is the condenser lens 50; 100 to the optical axis
This is a semiconductor laser placed obliquely in front and back.

FIG. 3 is a diagram illustrating the reflection path of laser light when the optical axis (a) of the condensing lens 5 and the optical axis f of the semiconductor laser 7 of the above embodiment are tilted by an angle θ. 4 is a view of FIG. 3 viewed from the right side. The outermost lights (d) and (el) emitted in a direction parallel to the heterojunction surface 9 of the chip 8 of the semiconductor laser 7 are incident on the condenser lens 1 at angles α and β, respectively, and are reflected, resulting in reflected light ( bL (C) Here, if the maximum emission angle of the laser beam is φ, it is clear that the reflected light (b) does not return to the chip of the semiconductor laser 7 within the range where the relationship φ<el holds. .Therefore, semiconductor laser 7
The output angle in the direction parallel to the mouth interface is at most 10
By making the inclination θ of the optical axis f much larger than the maximum output angle, it is possible to prevent the reflected light from the end faces of the condenser lens 5 and the optical attenuator 6 from returning to the semiconductor laser 7. In FIG. 4, reference numeral 10 indicates a near field pattern on the incident end surface of the condenser lens 5. In FIG.

Next, the operation of the above embodiment will be explained.

The emitted light from the semiconductor laser 7 is sent to the optical fiber 4 through the condensing lens 5.
The light is focused on the zero incidence plane and efficiently enters the optical fiber 4. On the other hand, the condensed light is reflected from the input end face (e) of the inner fiber 4 and the input/output end face (C) of the condensing fiber 4, but is attenuated by the optical attenuator 6 and transmitted to the semiconductor laser 7. won't return. Furthermore, the light emitted from the semiconductor laser 7 is transmitted through a condensing lens 50.
Although it is reflected by the incident end face (C) and the optical attenuator 6, it does not return to the semiconductor laser 7 because the optical axes of the condenser lens 5 and the semiconductor laser 7 are tilted.

In this way, according to the above embodiment, since the optical attenuator 6 is disposed in front of the incident end face of the condenser lens 5, the optical fiber 4
It is possible to attenuate the reflected light returning onto the chip of the semiconductor laser 7 from the incident end face of the condenser lens 5 and the input/output end face of the condensing lens 5, thereby preventing deterioration of the characteristics of the semiconductor laser 7. However, according to this embodiment, far-end reflected light from optical components such as optical connectors and light receiving elements can be prevented to some extent. Further, according to the present embodiment, there is no need to process one end of the condenser lens 5 into a hemispherical shape as in the conventional example, so that the process becomes easy.

Effects of the Invention The present invention has the above configuration, and according to the present invention, a coupling system of a semiconductor laser and an optical fiber (including an optical fiber) is provided.
The reflected light can be returned to the semiconductor laser, and deterioration of the characteristics of the semiconductor laser can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a conventional laser module device, FIG. 2 is a schematic explanatory diagram of a laser module device according to an embodiment of the present invention, FIG. 3 is an explanatory diagram of a reflection path of a laser beam of the same device, FIG. 4 is a right side view of FIG. 3. 4... Optical fiber, 5... Condensing lens, 6... Optical attenuator, 7... Semiconductor laser, 8... Chip, 9... Heterojunction surface. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A cylindrical condensing lens whose refractive index decreases as it goes from the central axis to the outer periphery, and a Peter junction surface on a plane that includes the optical axis of this condensing lens, and the optical axis is aligned with the optical axis of the condensing lens. a semiconductor laser that intersects at a predetermined angle with respect to the optical fiber; an optical fiber having an inclined incident surface, the incident end surface of which is disposed at the condensing point of the condensing lens; A laser module device comprising an optical attenuator interposed between the laser module and the optical attenuator.