KR100544176B1 - Vertical cavity surface emitting laser and optical pickup apparatus employing thereof - Google Patents

Abstract

Disclosed is a surface light laser having a non-reflective portion which causes reflection of light re-incident to at least a portion of an upper surface thereof to be reflected back to the upper surface thereof, and an optical pickup apparatus employing the same.

By employing such a surface light laser in the optical pickup device, stable signal detection is possible. In particular, when a surface light laser having a non-reflective portion having a predetermined size is employed in the optical pickup apparatus for detecting the track error signal by the three-beam method, a stable track error signal can be obtained.

Description

Surface cavity laser and optical pickup apparatus employing the same

1 is a plan view schematically showing a general surface light laser,

2 is a perspective view schematically showing an embodiment of an optical pickup apparatus employing a surface light laser according to the present invention;

3 is a plan view schematically showing a surface light laser according to the present invention provided to be suitable for the optical pickup device of FIG.

4 is a cross-sectional view schematically showing a laminated structure of the surface light laser of FIG.

5 is a perspective view schematically showing another embodiment of an optical pickup apparatus employing a surface light laser according to the present invention;

6 and 7 schematically show a state in which light traveling from the surface light laser toward the recording medium and light traveling from the recording medium are diffracted and branched to the hologram element and the grating in FIG.

8 is a plan view schematically showing a surface light laser according to the present invention provided to be suitable for the optical pickup device of FIG.

<Description of the symbols for the main parts of the drawings>

10 ... surface light laser 11 ... substrate

12,15 ... lower and upper reflector layer 13 ... active layer

16,17 Lower and upper electrodes 18 ... Windows

19 ... Non-reflective 20,120 ... Grating

40 objective lens 50 recording medium

70 photodetector 130 hologram element

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light laser having an improved structure such that the reflectance of light reincident with a surface cavity laser (Vertical Cavity Surface Emitting Laser) is minimized and an optical pickup apparatus employing the same.

In general, the surface light laser emits light close to a circle in the stacking direction of the semiconductor material layer, so that the surface light laser is easy to arrange, and there is no need for a separate beam shaping. Since the surface of such a surface light laser is usually made of a metal electrode formed of gold or the like, or a surface of a semiconductor substrate such as AlGaAs or GaAs, it has a considerably high reflectance of, for example, 50% or more.

On the other hand, in a general optical pickup device that detects a tracking error signal by a three-beam method, it is emitted from a light source, diffracted by zeroth order diffraction light and ± 1st order diffracted light, that is, a main beam and two subbeams by grating, and forms an optical spot on a disc. Light is reflected off the disk and most of it is detected in the photodetector. However, the partial light amount is returned to the light source, and three reflected diffraction beams, that is, a main beam and two subbeams, of a predetermined light amount are incident on the light source. At this time, the distance between the three reflection diffraction beams incident on the light source from the disk side is within several tens of micrometers in the arrangement of the optical pickup apparatus.

As a light source of such an optical pickup device, there is a tendency to employ such a surface light laser that is easy to arrange and that does not require beam shaping. For example, a surface light laser having a surface area of 200 × 200 μm or more is generally employed.

Therefore, the three reflected diffraction beams incident on the surface light laser can be incident mostly into the surface area of the surface light laser 1 as shown in FIG. Here, reference numeral 7a denotes main beams 7b and 7c are subbeams located at both sides of the main beam 7a. At this time, the main beam 7a is incident on a region including the window 5 from which light is emitted from the surface light laser 1.

At this time, since the surface light laser 1 has a relatively large reflectance, the incident reflection diffraction beams 7a, 7b, and 7c are reflected from the surface and then irradiated onto the disk (not shown). This results in mutual interference with the light emitted from the surface light laser 1 and immediately irradiated onto the disk, thus adversely affecting the detection signal of the optical pickup device (not shown). In particular, the mutual interference between the subbeam emitted immediately from the surface light laser 1 and diffracted by grating (not shown) and irradiated to the disc and the subbeam rereflected from the surface of the surface light laser 1 and irradiated to the disc are tracked. It acts as noise to the error signal.

In addition, the surface light laser as described above is applied not only to the structure employing the grating but also to the optical pickup apparatus of various structures, and the light reflected from the disk is incident again to the surface light laser and reflected from the surface to the next disk. The light is irradiated again and immediately interferes with the light irradiated onto the disk, thereby adversely affecting information recording and / or reproducing signals and error signals.

In addition, even when the surface light laser 1 is employed as a light source of another optical device, the light reflected from at least one member constituting the optical device is incident again to the surface light laser, Again reflected and interfering with the light emitted directly from the surface light laser can lead to degradation of the performance of the overall optical device.

The present invention has been made in view of the above, and the surface light laser having improved structure so that the light re-incident with the surface light laser is hardly reflected from the surface, and the light that is capable of stable signal detection by employing the same The object is to provide a pickup device.

The present invention to achieve the above object, a substrate; A bottom reflector layer laminated on the substrate; An active layer formed on the lower reflector layer and generating light by recombination of electrons and holes; An upper reflector layer formed on the active layer; A lower electrode formed on the lower surface of the substrate; And an upper electrode formed on at least a portion of an upper surface of the upper reflector layer except for the window from which the laser light is emitted, wherein the surface light laser generates and emits laser light in a stacking direction of the semiconductor material layer. A non-reflective portion is provided in at least some regions except for the window of the upper surface such that a part of the light emitted from the upper surface is minimized when a part of the light emitted from the reflected light is reflected by a predetermined member and reincident into the surface light laser. Characterized in that.

Here, the non-reflective portion is preferably made of a non-reflective layer coated on at least a portion of the upper surface or a region for diffusely reflecting incident light formed on a portion of the upper surface.

In addition, the present invention to achieve the above object, the surface light laser for generating and emitting light in the stacking direction of the semiconductor material layer; Optical path converting means for converting a traveling path of the incident light; An objective lens for focusing incident light on a recording surface of a recording medium; And a photo detector, which is reflected from the recording medium and receives light incident through the objective lens and the optical path converting means, to detect an information signal and an error signal. , Board; A bottom reflector layer laminated on the substrate; An active layer formed on the lower reflector layer and generating light by recombination of electrons and holes; An upper reflector layer formed on the active layer; A lower electrode formed on the lower surface of the substrate; An upper electrode formed on at least part of an upper surface of the upper reflector layer except for the window from which the laser light is emitted; And a non-reflective portion provided in at least some regions except for the window on the upper surface such that a part of the light reflected from the recording medium is re-entered to the surface light laser side and the amount of light reflected from the upper surface is minimized.

According to a feature of the present invention, a grating is disposed on an optical path between the surface light laser and the optical path converting means and diffracts the light incident from the surface light laser to branch into zero-order diffraction light and ± first-order diffraction light; And a track error signal detected by a three-beam method, wherein the non-reflective portion is provided at an incident position of at least part of the diffracted light by the grating reflected from the recording medium and incident on the surface light laser. .

According to another feature of the present invention, the light incident from the surface light laser toward the light path conversion means is transmitted through most straight, and the light reflected from the recording medium is mostly diffracted by +1 or -1 order A hologram element directed toward a detector, disposed on an optical path between the surface light laser and the hologram element to diffract the light incident from the surface light laser to branch into zero-order diffraction light and ± first-order diffraction light And a grating; for detecting a track error signal by a three-beam method, wherein the non-reflective portion is diffracted by at least some of the light reflected from the recording medium and then diffracted by the hologram element to be incident on a surface light laser. It is provided at the incident position of light.

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

2 is a perspective view schematically showing an embodiment of the optical pickup device employing the surface light laser according to the present invention, Figure 3 is a surface light laser 10 according to the present invention provided to be suitable for the optical pickup device of FIG. Is a plan view schematically.

Referring to the drawings, the optical pickup device according to an embodiment of the present invention is a surface light laser 10 for generating and emitting light in the stacking direction of the semiconductor material layer, optical path conversion means for converting the traveling path of the incident light, An objective lens 50 for focusing incident light on a recording surface of the recording medium 50, a grating 20 for diffracting incident light disposed on an optical path between the surface light laser 10 and the optical path converting means and information And a photodetector 70 for detecting the signal and the error signal. Here, reference numeral 60 functions as a light receiving lens that focuses incident light on the photodetector 70 with a concave lens.

The optical path converting means includes a beam splitter 30 for transmitting and reflecting incident light at a predetermined ratio. The beam splitter 30, for example, reflects the light emitted from the surface light laser 10 toward the recording medium 50, and transmits the light reflected from the recording medium 50 to be incident to the photodetector. Face 70.

In the present embodiment, the light incident from the surface light laser 10 is diffracted on the optical path between the surface light laser 10 and the beam splitter 30 so as to branch into zero-order diffraction light and ± first-order diffraction light. The grating 20 is further provided. Here, the 0th order diffracted light is a main beam formed as a light spot on the main track of the recording medium 50, and the ± 1st order diffracted light is a subbeam formed at an angle before and after the main beam over the main track and an adjacent track.

In addition, the photodetector 70 preferably includes a main photodetector 71 for detecting a main beam reflected by the recording medium 50 and a sub photodetector 73 for detecting the two subbeams. .

The main photodetector 71 is composed of four division light receiving regions A, B, C, and D having a 2 × 2 matrix arrangement, and receives zero-order diffracted light and photoelectrically converts them independently. The information signal and the focus error signal are detected from the detection signals of the four-split light receiving regions A, B, C, and D. The sub photodetector 73 includes first and second light receiving regions E and F disposed at both sides of the main photodetector 71, respectively. The first light receiving area E receives the + 1st order diffracted light and the second light receiving area F receives the −1st order diffraction light, respectively, and the track error signal is the first and second light receiving areas E and F. Differential detection signal is detected.

In the optical pickup apparatus which detects the track error signal by the three-beam method as described above, the light emitted from the surface light laser 10 and split by the grating 20 into three diffracted light, that is, the main beam and the two sub-beams is beamed. Reflected by the splitter 30 and focused by the objective lens 50, it is formed as an optical spot on the recording surface of the recording medium 50 for recording and / or reproduction. The light is reflected on the recording surface and then incident to the beam splitter 30 via the objective lens 50, and most of the light passes through the beam splitter 30 and is detected by the photodetector 70. However, since the beam splitter 30 partially transmits the incident light and partially reflects the incident light, the partial amount of light of the three reflected diffraction light incident on the beam splitter 30 is reflected by the beam splitter 30 to reflect the surface light laser ( 10).

Therefore, the surface light laser 10 according to the present invention is to prevent the deterioration of the signal that may occur due to the light incident on the beam splitter 30 is reflected from the surface and then irradiated to the recording medium 50 again. As shown in FIG. 9, the non-reflective portion 11 is characterized in that the non-reflective portion 11 is located at the incidence position of at least some of the three diffracted light beams incident on the surface light laser 10 via the beam splitter 30. .

In the surface light laser 10, as shown in FIG. 4, the lower reflector layer 12, the active layer 13, and the upper reflector layer 15 are sequentially formed on the semiconductor substrate 11. The upper electrode 17 is formed on at least a portion of the upper surface of the substrate 11 except for the lower electrode 16 and the window 18 from which the laser light on the upper reflector layer 15 is emitted. . Here, reference numeral 14 is a guide layer for guiding the flow of current. The active layer 13 is a region where light is generated by recombination of electrons and holes generated in the lower and upper reflector layers 12 and 15 by currents applied through the upper and lower electrodes 17 and 16. The light generated in the active layer 13 is resonated between the lower and upper reflector layers 12 and 15 so that only light of a specific wavelength region corresponding to the resonance condition survives. The laser light is transmitted through the window 18 through most of the upper reflector layer 15 having a relatively smaller reflectance than the lower reflector layer 12.

The surface light laser 10 having the laminated structure as described above is a top emitting structure, in the case of the bottom emitting structure, the lower reflector layer has a relatively small reflectance compared to the upper reflector layer and the substrate is provided to emit laser light, Most of the laser light is emitted through the lower reflector layer.

Here, the top emitting or bottom emitting structure of the surface light laser 10, the function of each layer and the material configuration are as well known, and thus a detailed description thereof will be omitted.

Referring back to FIG. 3, in the present embodiment, the upper electrode 17 of the surface light laser 10 is provided over the entire upper surface except for the window 18 from which the laser light is emitted, and the non-reflective portion 19 Is preferably provided at the incidence position of the first-order reflection diffraction light among the reflection diffraction beams. In this case, as shown in FIG. 4, the non-reflective unit 19 may be formed by etching a portion of the upper electrode 17 corresponding to the incident position of the ± first order reflected diffracted light to diffusely reflect incident light.

For example, considering the optical system of the entire optical pickup apparatus, the distance between the main beam and the sub-beam diffracted by the grating 20 is about 10 to 25 μm on the recording medium 50, and the horizontal magnification of the optical system is about 5 If doubled, the position of the subbeam on the surface light laser 10 is approximately 50 to 123 탆 away from the window 18 from which the laser light is emitted. Therefore, in consideration of the diffusion caused by the aberration of the lens member or the like such as the objective lens 50 of the sub-beam, the non-reflective portion 19 may be formed by etching a region of sufficient size, for example, 10 µm or more in diameter.

In the present embodiment, it is preferable that the non-reflective portion 19 is provided at the incidence position of the ± 1st order reflected diffraction light. When the ± 1st order reflected diffraction light is reflected on the surface of the surface light laser 10, Since the reflected light is emitted directly from the surface light laser 10 and irradiated to the irradiation position of the ± first-order diffraction light diffracted by the grating 20, the reflected light interfering with the immediately-irradiated ± first-order diffraction light as described above causes noise to the track error signal. Because it can act as.

When the non-reflective portion 19 is provided as described above, since the reflectance at the non-reflective portion 19 becomes approximately 10% or less, then the light is reflected from the recording medium 50 in the optical pickup apparatus as shown in FIG. Reflected diffracted light incident on the surface light laser 10 side, in particular, the sub-beams are hardly re-reflected on the surface of the surface light laser 10 so that no noise is generated in the track error signal, thereby obtaining a stable track error signal.

5 is a perspective view schematically showing an optical pickup apparatus according to another embodiment of the present invention. Here, the same reference numerals as those in Fig. 2 denote the same members having substantially the same functions. This embodiment employs a hologram element 130 as a light path converting means instead of a beam splitter (30 in FIG. 2), so that the surface light laser 10, the grating 20, the hologram element 130 and the photodetector 70 ) Is an integrated optical module 100 structure. In this case, the hologram element 130 is directed toward the recording medium 50 by diffracting most of the light incident from the grating 120 toward a straight transmission, that is, zero-order diffracted light, and is reflected by the recording medium 50 to be incident. Most of the light to be diffracted by the + 1st order diffracted light is directed toward the photodetector 70.

However, as shown in FIG. 6, the hologram device 130 substantially not only outputs the 0th order and ± 1st order diffracted light incident by diffraction by the grating 120, but also the amount of light is small but ± 1. As shown in Fig. 7, the three zeroth order diffracted light reflected and incident on the recording medium 50 are diffracted not only in the + 1st order but also in the 0th order and -1th order, although the amount of light is small. 6 and 7 show the hologram element 130 and the grating 120 separately from each other for convenience.

In this case, as shown in FIG. 6, the + 1st order diffracted light and the −1st order diffracted light diffracted by the hologram element 130 facing the recording medium 50 do not enter the objective lens 50 and are lost. Only three zero-order diffracted light are focused by the objective lens 50 to form light spots on the recording medium 50. At this time, the light that has been diffracted by the zeroth order by the grating 120 among the three zeroth order diffracted light, that is, the main beam 131 is formed on the main track of the recording medium 50, and is ±± 1th order by the grating 120. The light that has been diffracted, i.e., the two subbeams 132 and 133, is obliquely formed in the front and rear directions of the main beam 131 over the main track and an adjacent track adjacent thereto. The main beam 131 and the sub beams 132 and 133 function substantially the same as those described with reference to FIG. 1.

Referring to FIG. 7, the three zeroth order diffracted light 131, 132, 133 are reflected from the recording medium 50 and then passed through the hologram element 130, respectively. It branches to the first order diffracted light. Therefore, the + 1st order diffracted light of the light reflected by the recording medium 50 and diffracted by the hologram element 130 is detected by the photodetector 70, and the 0th order diffracted light passes through the grating 120 to provide a surface light laser. Return to (10). The returned zeroth order diffracted light, i.e., the main beam and the two sub-beams, is reflected from the surface of the surface light laser 10 and irradiated onto the recording medium as in the case of FIG. 1, and immediately emitted from the surface light laser 10. And may cause mutual interference.

However, as in the embodiment of the present invention, as shown in Fig. 8, since the non-reflective portion 19 according to the present invention is provided on the upper surface of the surface light laser 10, for example, the incident position of the two sub-beams. Since the light is not irradiated to the recording medium 50, stable track error signal can be detected.

In the above description, the surface light laser 10 according to the present invention has been described with reference to an example provided to be suitable for the optical pickup device as shown in FIGS. 2 and 5, but is not limited thereto. It may have a non-reflective portion 19 modified to suit. Accordingly, the optical pickup apparatus having various structures employing the surface light laser 10 according to the present invention can detect not only a more stable signal, that is, an information signal and a focus error signal, but also a track error signal.

In addition, the surface light laser 10 according to the present invention has been described and illustrated that the non-reflective portion 19 is formed by etching a part of the upper electrode 17 to diffuse the incident light, by coating the anti-reflection layer in the position It is also possible.

As such, when the non-reflective portion 19 is formed of a coated anti-reflective layer, an area for further coating the non-reflective layer over a predetermined area of the area around the window 18 or wire-bonding the external terminal and the upper electrode 17. And a non-reflective layer can be formed over the entire upper surface of the surface light laser 10 except for the window 18. In this case, not only the sub-beams incident on the surface light laser 10 side but also the main beams are hardly reflected from the surface thereof, and noise is not generated even when the information signals on the main tracks are detected, thereby making it possible to detect the information signals more accurately.

In addition, although the upper electrode 17 has been described and illustrated as being formed over the entire upper surface of the surface light laser 10, the upper electrode 17 having a predetermined pattern may be formed only on a portion of the upper surface thereof. In this case, since the upper surface except for the upper electrode 17 is made of a semiconductor material such as AlGaAs or GaAs and has a reflectivity of about 50% or more like the metal electrode, the non-reflective portion 19 according to the present invention is the surface light laser 10 Of course, it is formed in the appropriate region of the upper surface.

Moreover, the case where the surface light laser 10 according to the present invention having the non-reflective portion 19 in at least a portion of the upper surface except for the window 18 is provided by way of example. In addition to the optical pickup device as described above, it may be employed as a light source in various optical devices, wherein the non-reflective portion 19 is reflected light from at least one member of the components constituting the optical device, the surface light laser 10 Of course, it can be applied in various forms so as not to cause a deterioration of the performance of the entire optical device due to re-reflection at the surface of the.

Accordingly, the embodiments described with reference to the drawings are merely exemplary, and the true technical protection scope of the present invention should be defined by the technical spirit of the claims.

The surface light laser according to the present invention as described above has a non-reflective portion that causes reflection of light incident to the surface light laser hardly occurs in at least a portion of the upper surface thereof.

Therefore, employing such a surface light laser can improve the overall performance degradation of the optical device, which can be caused by light that is reincident to the light source and reflected from its surface.

In addition, when the surface light laser according to the present invention is employed in the optical pickup device, stable signal detection is possible. In particular, when a surface light laser having a non-reflective portion having a predetermined size is employed in the optical pickup apparatus for detecting the track error signal by the three-beam method, a stable track error signal can be obtained.

Claims (8)

Board; A bottom reflector layer laminated on the substrate; An active layer formed on the lower reflector layer and generating light by recombination of electrons and holes; An upper reflector layer formed on the active layer; A lower electrode formed on the lower surface of the substrate; And an upper electrode formed on at least a portion of an upper surface of the upper reflector layer except for the window from which the laser light is emitted, wherein the surface light laser generates and emits laser light in a stacking direction of the semiconductor material layer. A portion of the light emitted from the surface light laser is reflected by at least a portion of the surface light laser when reflected by the predetermined member and reincident into the surface light laser. A surface light laser comprising a four-part. The method of claim 1, wherein the non-reflective unit, The surface light laser, characterized in that consisting of a non-reflective layer coated on at least a portion of the upper surface or a region that diffuses the incident light formed on a portion of the upper surface. A surface light laser for generating and emitting light in a stacking direction of the semiconductor material layer; Optical path converting means for converting a traveling path of the incident light; An objective lens for focusing incident light on a recording surface of a recording medium; And a photodetector that is reflected from the recording medium and receives light incident through the objective lens and the optical path converting means and detects an information signal and an error signal. The surface light laser, the substrate; A bottom reflector layer laminated on the substrate; An active layer formed on the lower reflector layer and generating light by recombination of electrons and holes; An upper reflector layer formed on the active layer; A lower electrode formed on the lower surface of the substrate; An upper electrode formed on at least part of an upper surface of the upper reflector layer except for the window from which the laser light is emitted; And a non-reflective portion provided in at least some regions except for the window on the upper surface such that a part of the light reflected from the recording medium is re-entered to the surface light laser side to minimize the amount of light reflected from the upper surface again. Pickup device. The grating of claim 3, further comprising: a grating disposed on an optical path between the surface light laser and the optical path converting means and diffracting the light incident from the surface light laser to branch into zero-order diffraction light and ± first-order diffraction light; Further, it is provided to detect the track error signal by the three-beam method, And the non-reflective portion is provided at an incident position of at least a portion of diffracted light by the grating reflected from the recording medium and incident on the surface light laser. The optical pickup apparatus of claim 4, wherein the non-reflective unit is provided at a predetermined width at an incident position of the ± first order diffracted light. 4. The light detector according to claim 3, wherein most of the light incident from the surface light laser toward the optical path converting means is transmitted straight, and the light reflected from the recording medium is mostly diffracted in the +1 or -1 order. Having a hologram element for directing, A grating disposed on an optical path between the surface light laser and the hologram element to diffract the light incident from the surface light laser to branch into zero-order diffraction light and ± first-order diffraction light. Provided to detect an error signal, And the non-reflective portion is provided at an incidence position of at least some of the diffracted light reflected from the recording medium and then zero-order diffracted by the hologram element to be incident on a surface light laser. 7. The incident position of the sub-reflective portion of claim 6, wherein the non-reflective portion is reflected from the recording medium and then diffracted by the hologram element to be incident toward the surface light laser, and the two sub-beams of the two sub-beams positioned on both sides thereof. Optical pickup device, characterized in that provided in. The optical pickup apparatus of any one of claims 3 to 7, wherein the anti-reflective unit comprises an anti-reflective layer coated on at least a portion of the upper surface or an area for diffusely reflecting incident light formed on a portion of the upper surface.

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