KR0138341B1 - An optical output controller of a surface optical laser and a recording/reproducing optical pick up - Google Patents

Abstract

Disclosed are an optical output control device of a surface light laser and an optical pickup for recording / reproducing using the same.

The light output control device of the surface light laser is a half mirror installed in front of the surface light laser and reflecting a part of the light emitted therefrom, and a monitor installed at the rear of the surface light laser to receive light reflected by the half mirror. It has a photodetector.

The optical pickup for recording / reproducing using the light output control device of the surface light laser includes a surface light laser having a light generating surface and emitting light in a direction perpendicular to the light generating surface, and the light of the surface light laser. Optical output control means for controlling the output, an objective lens for focusing incident light to form a light spot on the optical recording medium, optical path converting means for changing a traveling path of the reflected light from the optical recording medium, and receiving the reflected light And a first photodetector for detecting an error signal and an information signal, wherein the light output control means is installed in front of the surface light laser and reflects a part of light emitted from the surface light laser, and the surface And a second photodetector for a monitor installed at the rear of the optical laser and receiving the light reflected by the half mirror.

Description

Optical power control device of surface light laser and optical pickup for recording / reproducing

1 is a schematic view showing an example of a light output control apparatus of a conventional surface light laser.

2 is a graph showing a comparison between the amount of vertical light and the amount of lateral light output from a conventional surface light laser light source.

3 is a schematic view showing another example of the light output control apparatus of the conventional surface light laser.

4 is a perspective view showing the light output control device of the surface light laser according to the present invention.

5 is a schematic diagram showing an optical pickup for recording / reproducing using the light output control apparatus of the surface light laser according to the present invention.

Explanation of symbols on the main parts of the drawings

60,100. Surface-emitting lasers 70,90. Photodetector for Monitor

72 ... light-receiving pattern

110 Hologram element 120 Objective lens

130 ... optical disk

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical output control device of a surface light laser and an optical pickup for recording / reproducing using the same. An optical output control device of a surface light laser improved to adjust and an optical pickup for recording / reproducing using the same.

In general, the light output control device of the surface light laser refers to a photodetector for a monitor employed as a means for controlling the amount of light emitted from the light source of the surface light laser.

The light source emits light in a direction perpendicular to the semiconductor material stacked on the substrate, unlike an edge emitting laser that emits light toward the side of the stacked semiconductor material. Since the light emitted from this light source is close to circular light, has a high light density, and operates in a single mode, it is widely used in optical application devices such as optical output devices and computer fields of optical pickup.

However, since the surface light laser emits light in a direction perpendicular to the upper surface and the lower surface is coupled to the semiconductor substrate, it is difficult to install the photodetector for the monitor.

In order to overcome this problem, US Patent No. 5,285,466 discloses a 'Feedback mechanism for VCSEL'.

This mechanism is described with reference to FIGS. 1 to 3.

This mechanism includes a light source 12 of a surface light laser to which a forward bias voltage is applied to emit light, and an annular ring around the light source 12 to absorb self-luminous light emitted from the side of the light source 12. The monitor photodetector 14 is provided. The light source 12 and the photodetector 14 are formed on a single semiconductor substrate 10. The photodetector 14 is mainly a surface light laser, and receives light by applying a reverse bias voltage or not applying a voltage to electrode layers formed on upper and lower surfaces.

The photodetector 14 receives the side light emitted from the light source 12, converts it into an electrical signal, and feeds it back to the electrode of the light source 12 to control the amount of light.

However, the light amount of the side light emitted to the side of the light source 12 is not only directly proportional to the light amount of the vertical light emitted vertically, but is significantly smaller than the light amount of the vertical light. In addition, since the emitted side light is transmitted by the photodetector 14 without being absorbed, it is difficult to obtain the amount of light required to detect a signal for controlling the amount of vertically emitted light.

As shown in FIG. 2, the vertical light is emitted from the light source 12 by the milling ampere current applied in the forward direction. Analyzing the vertical light detected through the photodetector, it can be seen that the vertical light has a lasing threshold 20 and a lasing end value 22 which are greatly increased or decreased in the amount of light. When the lasing current between the lasing threshold 20 and the end 22 is applied, an output current 24 of a few microamperes of a slope shape is detected, and for other applied currents. The current is close to zero.

The amount of current 34 of the side light emitted laterally from the light source 12 and detected by the photodetector 14 is generally smaller than the amount of vertical light emitted in the vertical direction and detected. In addition, the lasing threshold 30 and lasing end 32 are not apparent, but gradually increase and decrease according to the intensity of the applied current. Therefore, the amount of side light emitted laterally by the surface light laser light source 12 and detected by the photodetector is significantly smaller than the amount of light detected by the monitor photodetector when the edge emitting laser is used as the light source. This may reduce the precision of the light output control.

3 is a schematic view showing another example of the light output control apparatus of the conventional surface light laser. In order to overcome the problems mentioned in FIGS. 1 and 2, at least two surface light lasers 50 are provided side by side on a single substrate 40 made of, for example, N-type GaAs, and have the same forward bias voltage ( 52). In this case, both surface light lasers 50a and 50b generate and emit light in the vertical direction and the lateral direction. Since the forward bias voltage is equally applied, the emitted light is proportional to each other.

Here, one side surface laser 50a is used as a light source. The other surface light laser 50b coupled to the current sensor 56 and the like applied to the reverse bias voltage 54 is used as a photodetector. Therefore, the light emitted from the surface of the other surface light laser 50b is detected and the amount of emitted light from the surface light laser 50a used as the light source is adjusted. In this case, it is easy to control the amount of emitted light, but by employing two or more surface light lasers 50, the overall volume of the device becomes large, causing a price increase.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems, and has a first object to provide a light output control apparatus of a miniaturized surface light laser while efficiently adjusting the amount of light emitted from the surface light laser.

There is also a second object of providing an optical pickup using the light output control apparatus of the surface light laser of the present invention.

In order to achieve the first object, the light output control apparatus of the surface light laser of the present invention,

In the light output control apparatus for a surface light laser having a light generating surface and having a surface light laser for emitting light in a direction perpendicular to the light generating surface, and a light output control means for controlling the light output of the surface light laser. ,

The light output control means includes a half mirror installed in front of the surface light laser to reflect a part of the light emitted from the surface light laser, and a rear mirror installed behind the surface light laser to receive light reflected from the half mirror. And a monitor photodetector configured to control the light output of the surface light laser from the amount of light received by the monitor photodetector.

In order to achieve the second object, the recording / reproducing optical pickup employing the light output control apparatus of the surface light laser according to the present invention,

A surface light laser having a light generating surface and emitting light in a direction perpendicular to the light generating surface, light output control means for controlling the light output of the surface light laser, and condensing the incident light to provide a light spot on the optical recording medium. A surface light laser, comprising: an objective lens to be formed; an optical path converting means for changing a traveling path of reflected light from the optical recording medium; and a first optical detector for receiving the reflected light to detect an error signal and an information signal In the optical pickup for recording / playback employing the optical output control device of

The light output control means may include a half mirror installed at the front surface of the surface light laser to reflect a part of the light emitted from the surface light laser, and a rear mirror installed at the rear of the surface light laser to receive light reflected by the half mirror. And a second photodetector for the monitor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 4, the light output control apparatus of the surface light laser according to the present invention includes a light source 60 having a laminated structure for emitting light 62 in the vertical direction, and a vertical direction of the light source 60. It consists of a light output control means to be described later for adjusting the amount of light emitted.

The light source 60 is made of a surface light laser. This surface light laser is formed by stacking at least one N layer and at least one P layer. This surface light laser generates and emits light by a quantum-well active region formed between an N-type distributed Bragg reflector (hereinafter referred to as DBR) layer and a P-type DBR layer. This surface light laser is driven by applying a forward bias voltage. The vertical light 62 is emitted not only in the vertical direction but also in the horizontal direction by the voltage applied in this way.

The light output control means includes a half mirror 80 provided on the output optical axis of the light source 60 to partially reflect the vertical light 62 emitted from the light source 60 at a predetermined ratio, and the monitor light. It comprises a detector 70.

The monitor photodetector 70 may be configured using a silicon semiconductor that is relatively inexpensive without using an expensive compound semiconductor. The photodetector 70 has a plate shape and the light source 60 is coupled to an upper surface thereof. In addition, on the photodetector 70, a photodetecting surface 72 is disposed around the light source 60 to emit the reflected light 82 reflected from the half mirror 80 in a vertical direction from the light source 60. Is formed.

The half mirror 80 is made of a material capable of transmitting and reflecting incident light. It is mainly made of a material such as glass or transparent plastic, and most of the light is transmitted but part of it is reflected. In the case of conventional glass, reflection of 5% to 10% of incident light occurs. The half mirror coating method is used as a means for increasing the reflectance, and the amount of light reflected from the half mirror 80 and incident on the photodetector 70 can be adjusted by such means.

The vertically emitted light 62 emitted from the light source 60 is mostly transmitted by the half mirror 80 positioned on the optical axis of the light source 60 and partially reflects the light. The transmitted light is used for the original purpose of the device, and the reflected light 82 is used for adjusting the amount of emitted light of the light source 60. The reflected light 82 reaches the photodetecting surface 72 at a reflection angle approximately twice that of the divergence angle of the light emitted from the light source 60. The amount of light 82 reaching the photodetecting surface 72 is proportional to the amount of light emitted from the light source 60. When the photodetecting surface 72 is installed to protrude a predetermined height, the side light 64 emitted from the side of the light source 60 can also be received.

As described above, since a current proportional to the amount of light emitted from the light source can be obtained in the photodetector according to the present invention, the amount of output light of the light source can be precisely adjusted according to the current signal.

In addition, since only one surface light laser is used, the size of the device can be miniaturized and manufacturing cost can be reduced by employing a low-cost silicon semiconductor.

Referring to Fig. 5, the structure and function of the optical pickup employing the light output control device of the surface light laser as described above will be described.

The optical pickup is an object for connecting the surface light laser 100 that emits the vertical light 102 and the light 102 emitted from the surface light register 100 onto the disk 130 which is an optical recording / reproducing medium. First light detector 94 for receiving the lens 120, the light 104 reflected from the disk 130 to detect a focusing error signal and a tracking error signal, and the amount of emitted light of the singer surface light laser 100 It is provided with a light output control means described below for receiving a portion of the emitted light to adjust the.

On the optical path between the surface light laser 100 and the optical disk 130, optical path conversion means for diffracting the light reflected from the recording surface of the optical disk 130 at a predetermined angle is provided. It is preferable to provide the hologram element 110 as this optical path converting means. The hologram device 110 has a characteristic of transmitting the light 102 emitted from the surface light laser 100 in a straight line and diffracting the light reflected from the optical disc 130.

The light output control means includes a second photodetector 90 for monitoring and a half mirror described later, and the second photodetector 90 functions to detect light for adjusting the output light amount of the surface light laser 100. The surface light laser 100 is supported. In addition, the first photodetector 94 is also provided on the upper surface of the second photodetector 90 so as to receive light 104 that is diffracted by the hologram element 110 and is incident.

The hologram element 110 transmits most of the light emitted from the surface light laser 100, but partially reflects the light. By using this property, it is preferable that the hologram element 110 perform the function of the half mirror described with reference to FIG. In this case, the reflectance may be increased by coating a reflective material on the lower surface of the hologram 110.

As mentioned above, the half mirror may be provided integrally with the hologram element 110 and may be provided as a separate member between the surface light laser 100 and the hologram element 110.

The monitor photodetector 90 receives the light 106 reflected from the hologram element 110 used as the half mirror on the photodetecting surface 92 formed on the upper surface thereof. The monitor photodetector 90 does not need to be a compound semiconductor having the same structure as the surface light laser 100, but may be a silicon semiconductor as employed in a conventional edge emitting laser.

In addition, the first photodetector 94 may be integrated with the second photodetector 90. In this case, the second photodetector for monitor 90 has a plurality of dividers. The light received at each partition plate is converted into a current signal, and a tracking and focusing error signal can be obtained using the sum and difference of the converted signals.

Therefore, the optical pickup of compact structure can be realized.

Claims (4)

In the light output control apparatus for a surface light laser having a light generating surface and having a surface light laser for emitting light in a direction perpendicular to the light generating surface, and a light output control means for controlling the light output of the surface light laser. , The light output control means may be provided in front of the surface light laser to reflect a part of the light emitted from the surface light laser to the periphery of the surface light laser, and the half mirror is integrally installed at the rear of the surface light laser. And a monitor photodetector for receiving the light reflected by the light detector, to control the light output of the surface light laser from the amount of light received by the monitor photodetector. The method of claim 2, A surface light laser having a light generating surface and emitting light in a direction perpendicular to the light generating surface, light output control means for controlling the light output of the surface light laser, and condensing the incident light to provide a light spot on the optical recording medium. A surface light laser, comprising: an objective lens to be formed; an optical path converting means for changing a traveling path of reflected light from the optical recording medium; and a first optical detector for receiving the reflected light to detect an error signal and an information signal In the optical pickup for recording / playback employing the optical output control device of The light output control means may be provided in front of the surface light laser to reflect a part of the light emitted from the surface light laser to the main surface of the surface light laser, and is integrally provided at the rear of the surface light laser. A recording / reproducing optical pickup employing an optical output control device for a surface light laser, characterized by comprising a second photodetector for a monitor that receives light reflected by the mirror. And the optical path converting means is a hologram element disposed between the surface light laser and the objective lens to diffract the reflected light from the optical recording medium toward the first photodetector. Optical pickup for recording / playback. The method of claim 2, The optical path converting means is a hologram element disposed between the surface light laser and the objective lens to diffract the reflected light from the optical recording medium toward the first photodetector, And said half mirror is coated on one surface of said hologram element.