JPS6032382A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable to reliably obtain an APC signal even if the reflectivity of the lower end of a semiconductor laser element is set to 1 or near this value by applying part of a laser light emitted from the upper end of the element as a monitoring light to a photoelectric converter mounted on the ceiling of a conductive sealing vessel. CONSTITUTION:A photodiode 7 of a photoelectric converter is bonded to the ceiling surface of a metal vessel 11, and the top of an external lead is connected through a soft metal 13 such as an indium to the opposite surface side to the bonded surface. With this structure, a photodiode 7 receives part of a laser light emitted from the upper end of a semiconductor laser element 6 as a monitoring light, photoelectrically converts it and outputs as an APC signal. Accordingly, it is not necessary to emit the laser light from the lower end for monitoring. Since the vessel 11 is electrically connected to a metal stem substrate 4 by sealing, an electrically equivalent state to the conventional structure for bonding the photodiode 7 directly to the metal stem substrate 4 can be obtained.

Description

Detailed Description of the Invention: Industrial Application Field The present invention utilizes a portion of the laser light emitted from a semiconductor laser element as a monitor light, and controls the amount of power supplied in accordance with the strength of the laser light. This invention relates to a semiconductor laser device in which emitted light is stabilized by doing so.

Conventional configurations and their problems Semiconductor laser devices have been widely used in the field of optoelectronics in recent years as small, lightweight, highly efficient, and highly reliable laser light sources. , the magnitude of laser light noise has a large effect. As one of the measures to reduce the noise of the laser light and obtain a high S/N, automatic control of the power supplied to the semiconductor laser device (APC) is proposed.
There is a control method. by the way,
8 In order to use PC, it is necessary to detect the strength of the laser light emitted from the semiconductor laser device.A photoelectric conversion device is placed inside the semiconductor laser device, and the output of the photoelectric conversion device is used as an APC signal. Similar structures have already been proposed.

FIG. 1 is a partially cutaway perspective view of a conventional semiconductor laser device having such a structure. A semiconductor laser element 6 is attached to this heat dissipation block, and a photoelectric conversion element, for example, a photodiode 7 is attached to the metal stem base 4, and further,
An assembled structure obtained by connecting a pixel element and an external lead with a thin metal wire 8.9 is sealed with a metal container 11 having a through hole 10.

In a semiconductor laser device having such a structure, the reflectance of both the upper and lower end surfaces of the semiconductor laser element (resonator) is 32%, and the laser light emitted from the upper end surface passes through the through hole 1o and passes through the metal container 11. taken outside. On the other hand, the laser light emitted from the lower end face is received by the photodiode 7 as monitor light, photoelectrically converted, and taken out as an APC signal. However, the intensity of the laser light emitted from the lower end facet is much higher than the intensity required as monitor light. Therefore, a part of the monitor light is reflected on the surface of the photodiode 7, and this light appears outside through the transparent light 10, creating a ghost.

In order to eliminate this ghost, it is possible to increase the reflectance by covering the lower end face with a metal film or dielectric film and reduce the laser light emitted from the lower end face, but these coatings If the reflectance is increased too much due to adhesion, there will be a shortage of monitor light, causing the inconvenience of not being able to obtain an APC signal. Therefore, when applying a film, breakage conditions must be determined from two aspects: eliminating ghosts and securing monitor light, and the application process is by no means easy. For this reason, a structure has been proposed in which the photodiode 7 is bonded to the main surface of the metal stem base 4 at an angle, as shown in a cross-sectional structure in FIG. According to such a structure, the laser light emitted from the upper end face of the semiconductor laser elements is transmitted through the transparent plate 12 such as a transparent glass plate, and is reliably extracted from the through hole 10. However, the reflection angle of the laser beam emitted from the lower end face changes, and most of it is confined inside the metal container 11. Therefore, it will be ghosted or eliminated. However, in order to bond the semiconductor laser element 7 at an angle as shown in the figure, it is necessary to drill a recess in the metal stem base 4 with an inclined bottom surface and a specified inclination angle. Second, there arises the disadvantage that the processing cost of the metal stem base itself increases significantly.

OBJECTS OF THE INVENTION An object of the present invention is to reliably obtain an APC signal even if the reflectance of the lower end face of a semiconductor laser element conventionally used to obtain monitor light is 1 or close to it. An object of the present invention is to provide a semiconductor laser device having a structure.

Composition of the Invention The semiconductor laser device of the present invention has a semiconductor laser element mounted on a stem base body having a through hole in the top surface, and is sealed with a conductive sealing container, and the semiconductor laser device of the present invention is sealed with a conductive sealing container. Glue one side of the photoelectric conversion element to the inner top surface excluding the hole,
The other surface faces the laser light emitting surface of the semiconductor laser element, and the tip of the external lead penetrating the stem base is connected to the electrode of the other surface of the photoelectric conversion element directly or through a connecting means. It has a built-in structure.

According to this structure, the photoelectric conversion element attached to the top surface of the conductive sealed container receives a part of the laser light emitted from the upper end surface of the half-41 laser element as monitor light, and receives an APC signal. occurs.

Therefore, the reflectance of the lower end face may be set to 1, and the light emitted from this face may be made zero, and the reflection of the laser light from the photoelectric conversion element will not appear outside through the through hole.

Description of Actual Gun Examples Actual gun examples of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a sectional view showing an embodiment of the semiconductor laser device according to the present invention, and the attachment of the semiconductor laser element 6 to the stem base 4 is similar to that shown in FIG. 1 or 2. The structure is the same as the conventional structure. However, there is a structure in which the photodiode 7, which is a photoelectric conversion element, is adhered to the top surface of the metal container 11, and the top of the external lead 1 is connected to the surface opposite to this adhesive surface via a soft metal 13 such as indium. It is different from the conventional one in that it is In the semiconductor laser device of the present invention having such a structure, the photodiode 7 receives a part of the laser light emitted from the upper end surface of the semiconductor laser element 6 as monitor light, photoelectrically converts it and converts it into an APC signal. Therefore, it is not necessary to emit a monitoring laser beam from the lower end face. The twisted metal container 11 also serves as one electrode of the photodiode 7, but since this metal container 11 is electrically connected to the metal stem base 4 by sealing, the photodiode 7 is directly connected to the metal stem base 4. A state electrically equivalent to that of the conventional structure in contact can be obtained.

Incidentally, the connection between the photodiode 7 and the external lead 1 is not limited to the connection structure using the above-mentioned soft metal.

4a and 4b are views showing other connection structures, such as a structure in which a spring 14 is interposed as shown in FIG. 4a, or a structure for flattening as shown in FIG. It is also possible to use an external lead 1 having a tip 15 that has been subjected to pressure processing and bending, and adopt a structure in which it is directly connected.

By the way, the typical full width at half maximum of the emitted light of a semiconductor laser element is 6 to 16 degrees in the direction horizontal to the junction and 20 to 40 degrees in the direction perpendicular to the junction. In this case, it is necessary to consider the full width at half maximum of the emitted light, the sensitivity of the photodiode, and the optical output of the semiconductor laser element.

In the semiconductor laser device of the present invention described above, a part of the laser light emitted to the through hole side is converted into APC (g −'i
'C (47), the noise of the laser beam is reduced.

FIG. 6 shows a comparison of S/N f of laser light with respect to current value of a semiconductor laser device that is subjected to APC using laser light from the lower end facet of a semiconductor laser device that is not subjected to APC, and a semiconductor laser device of the present invention. It is a diagram showing the experimental results studied, and the horizontal axis is normalized by the threshold current.

'1. The vertical axis is the S/N in a song with a center frequency f = 1 Mh and a bandwidth Δf-300. In the same figure, the characteristic curve A indicates a semiconductor laser device with an APC
Characteristic curve B shows APC using laser light from the lower end face.
The characteristic curve C shows the entire S/N ratio of the semiconductor laser device of the present invention.

As is clear from the drawings, the semiconductor laser device of the present invention has significantly improved S/N ratio.

The present invention has been explained above by exemplifying a metal-sealed semiconductor laser device, but it may also be possible to construct a stem base and a sealing container made of an insulator such as ceramic, and to have a sealing structure in which main parts are metallized. , the present invention is applicable.

Effects of the Invention In the semiconductor laser device of the present invention, the laser light that irradiates the photoelectric conversion element for obtaining an APC signal is a part of the laser light emitted from the upper end facet of the semiconductor laser element. It is possible to increase the reflectance and substantially suppress the light emitted from this surface 9, thereby reducing the threshold current, improving the differential efficiency, and increasing the output. Furthermore, the unity of the longitudinal mode and transverse mode is improved, and noise is also reduced.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing the structure of a conventional semiconductor laser device, FIG. 2 is a sectional view of a conventional semiconductor laser device having a structure for reducing reflected light from a photoelectric conversion element, and FIG.
The figure is a cross-sectional view illustrating the structure of the semiconductor laser device of the present invention, FIGS. , is a diagram showing the results of an experiment conducted to compare and inspect the S/N of laser light with respect to the current value of a semiconductor laser device of the present invention and a conventional semiconductor laser device. 1 to 3... External lead, 4... Metal stem base, 5... Heat dissipation block, 6... Semiconductor laser element, 7... Photodiode, 8, 9...・・・
・Thin metal wire, 10...Through hole, 11...Metal container, 12...Transparent plate, 13...Soft metal,
14...Spring, 15...Tip of external lead. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure @2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) The semiconductor laser element that has been inserted into the stem base is sealed with a conductive sealing container that has a through hole on the top surface, and the inside of the sealing container excluding the through hole part. One surface of the photoelectric conversion element is adhered to the top surface, the other surface is opposed to the laser light emitting surface of the semiconductor laser element, and further,
A semiconductor laser device characterized in that a tip of an external lead penetrating the stem base is directly connected to an electrode on the other surface of the photoelectric conversion element via a concubine or connecting means. (2) The semiconductor laser device according to claim 1, wherein the connecting means is either a soft metal body or a spring.