KR100644600B1 - Optical head for recording and reproducing using near field - Google Patents

Abstract

Disclosed is an optical head for near field recording and reproducing in a structure in which an optical element is disposed on a slider which performs recording and reproducing of information while floating on a recording medium by air dynamic pressure.

The disclosed optical field recording and reproducing head includes a lower slider having a light transmission hole through which incident light is transmitted; An upper slider coupled to and installed on the lower slider and having a mounting groove in which an optical element is mounted on a surface facing the lower slider, inclined at a predetermined inclination at an end of the mounting groove to reflect incident light; ; A light source installed in the mounting groove for irradiating light toward the recording medium; A converging lens mounted in the light transmitting hole to focus and transmit the light passing through the light transmitting hole; And a main photodetector installed at one surface of the lower slider facing the recording medium to receive the light reflected from the recording medium.

Description

Optical head for recording and reproducing using near field}

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the main portion of a conventional near field scanning optical microscopy (NSOM) optical head for near field recording and reproducing;

Fig. 2 is a schematic cross-sectional view showing the main portion of a conventional optical head for near field recording and reproduction of a solid-impregnated lens (SIL) system;

3 is an exploded perspective view showing an optical head for near field recording and reproducing according to an embodiment of the present invention;

4 is a cross-sectional view of FIG.

5 is a schematic view showing a main photodetector according to an embodiment of the present invention.

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

31 Lower slider 32 Transmitter

33.Block 35 ... opening

41 Top slider 42 Mounting groove

50 ... optical module 51 ... light source

55 ... sub-photodetector 61 ... optical fiber                 

64.Reflective surface 65.Procedure lens

70 ... main photodetector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a near-field recording and reproducing optical head capable of recording and reproducing information by using near-field light locally located near the surface of the recording medium. The optical head for near-field recording and reproducing has a structure in which an optical element is disposed on a slider for performing information recording and reproducing.

1 is a schematic cross-sectional view showing the main portion of a conventional near field recording and reproducing optical head of a near field scanning optical microscopy (NSOM) method.

Referring to FIG. 1, a conventional NSOM optical head for near field recording and reproducing generates and records a near field light on a recording medium 1 from a light source (not shown) and light irradiated from the light source. Probe 10 for transmitting the light reflected from the photodetector (not shown).

The probe 10 transmits incident light and has an optical fiber 11 positioned at one end with a small distance from the recording medium 1, and a metal film 15 formed to surround the optical fiber 11. It includes. The optical fiber 11 is composed of a core 12 and a clad 14 surrounding the core 12. Here, the cladding 14 becomes thinner gradually toward the end of the side facing the recording medium 1 at a predetermined length at one end thereof. And the end of the clad 14 is removed, the end of the core, that is, the probe tip 13 is formed to protrude a predetermined length. The probe tip 13 is a portion where the metal film 15 is not formed, and its cross-sectional size forms an opening approximately 1/10 of the wavelength of light emitted from the light source. The NSOM optical head configured as described above has a probe tip 13 because the probe tip 13 and the surface of the recording medium 1 should be kept close to each other by several nm when recording / reproducing information with respect to the recording medium 1. ) And the distance is controlled by feeding back a voltage to the piezoelectric element so that the amplitude of the vibration remains constant at all times.

The NSOM optical head has an advantage of obtaining a high density of about 100 gigabits per square inch as the surface recording density. On the other hand, the operating range of the optical head by the piezoelectric element is extremely narrow, such as up to several tens of micrometers, and the operating speed is very slow, up to several tens of micrometers / sec. In addition, since the manufacturing process of the optical head probe is complicated and lacks reproducibility, mass production is impossible, and there is a problem in that mechanical durability is low because it is easy to collide with the recording medium.

FIG. 2 is a schematic cross-sectional view showing the main portion of an optical head for near field recording and reproducing of a solid immersion lens (SIL) method.

Referring to Fig. 2, the conventional SIL-type near field recording and reproducing optical head includes a light source (not shown), an objective lens 21 for condensing light emitted from the light source, and a light focused at the objective lens 21. And a hemispherical SIL 23 to form a near field on the recording medium 1, and a slider 25 to which the objective lens 21 and the SIL 23 are mounted. The optical head having such a structure has the size of the size of the light spot before entering the SIL 23 on one surface of the SIL 23 facing the recording medium 1 when the refractive index of the SIL 23 is n. Can be reduced to 1 / n.

However, the light spots focused through the SIL 23 include far field components as well as near fields, which limits the size of the light spots. And, the larger the effective numerical aperture of the lens is, the more sensitive it becomes to the aberration of the optical system.

In the SIL method illustrated in FIG. 2, the SIL 23 is mounted on the floating slider 25 to increase the data transmission speed and improve the durability of the optical head, compared to the NSOM method.

On the other hand, except for the optical head portion, a device used for a conventional optical pickup device such as a lens optical system (not shown) is used as it is, and since each optical element is separated, a mechanism for focusing the optical axis and the device is needed. There is a problem that becomes complicated. In addition, there is a problem in that the apparatus is enlarged because a space for configuring the entire optical system is required. In addition, it is necessary to increase the light efficiency because the intensity of the optical signal is weak during near field recording. The disadvantage is that.

Therefore, with the configuration of the optical head as shown in Figs. 1 and 2 described above, practical use of near-field optical recording / reproducing is difficult. On the other hand, in order to realize near field optical recording / reproducing, the optical head for near field recording and reproducing is required to solve the following points. That is, high near-field light generation efficiency during recording, high sensitivity of light received by the photodetector during reproduction, high-speed signal detection, fine tracking of the recording strings can be precisely tracked, and digital cameras, camcorders, PDAs It is required to be miniaturized and to be able to mass-produce such that it can be mounted on a portable information device.

Accordingly, an object of the present invention is to provide an optical head apparatus for near field recording and reproducing, which has been devised in view of the above-mentioned problems and requirements, and has an improved optical efficiency and transmission speed, a compact, light weight, and precise tracking structure. have.

In order to achieve the above object, the optical head device for recording near-field recording material according to the present invention is driven by air pressure on the recording medium, and has a lower slider having a light transmission hole through which incident light is transmitted; An upper portion having a reflective surface coupled to and installed on the lower slider and having a mounting groove in which an optical element is mounted on a surface facing the lower slider, is formed to be inclined at a predetermined inclination at an end of the mounting groove to reflect incident light. With a slider; A light source installed in the mounting groove and irradiating light toward the recording medium; A converging lens mounted in the light transmitting hole to focus and transmit the light passing through the light transmitting hole; And a main photodetector installed at one surface of the lower slider facing the recording medium to receive the light reflected from the recording medium.

Hereinafter, an optical head for near field recording and reproducing according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 and 4, the optical head for near field recording and reproducing according to the embodiment of the present invention is driven while being floated by air dynamic pressure on the recording medium 1, and has a lower slider having an optical hole 32. (31), upper slider (41) having mounting grooves (42, 46) and reflecting surfaces (64), optical module (50) installed in said mounting groove (46), and in said light transmitting hole (32). And a main photodetector 70 formed on a surface facing the recording medium 1 of the lower slider 31.

An air bearing surface (ABS), that is, an unevenness is formed on the bottom surface 31a of the lower slider 31 so that an interval between the recording medium 1 and the recording medium 1 is substantially reduced due to the air flow caused by the rotation of the recording medium 1. Floating to maintain dozens of nm to 100 nm. The upper slider 41 is supported by the suspension 80. The suspension 41 is connected to a driving device (not shown) which allows the upper and lower sliders 41 and 31 to be driven on the recording medium 1. The recording medium 1 is composed of a recording layer 3 on which an information mark is recorded and a lubrication layer 5 provided on the recording layer 3 so that the lower slider 31 can be smoothly floated by pneumatic pressure. .

Each of the upper and lower sliders 41 and 31 is made of single crystal silicon, and the mounting grooves 42 and 46, the reflective surface 64, and the light transmitting hole 32 are each formed by anisotropic etching. desirable. Here, the anisotropic etching is performed by, for example, an aqueous solution of Tetra methyl Ammonium Hydroxide (TMAH), and the reflecting surface () is formed to be inclined along the crystal direction of the single crystal silicon, and the mounting groove 44 This long V-shape is formed. At this time, the angle θ of both the slope and the wall surface of the V-shaped groove is fixed by a predetermined angle, for example, about 55 degrees by the crystal direction of the single crystal silicon. In this case, it is preferable that a reflective film, for example, an aluminum reflective film having a relatively higher reflectance than the upper slider 41 is deposited on the reflective surface 64 so as to increase the reflectance.

Meanwhile, the mounting groove 46 on which the optical module 50 is to be mounted is formed as a rectangular groove and is formed through anisotropic reactive ion etching (RIE) etching.

The optical module 50 includes a light source 51 for irradiating light directed toward the recording medium 1. The light source 51 is composed of a corner-emitting semiconductor laser or the like, and the light irradiated from the light source 51 travels along the mounting groove 42 in a direction parallel to the recording surface of the recording medium 1. Then, the reflective surface 64 passes through the converging lens 65 and is reflected on the recording medium 1 in a state reflected perpendicularly to the recording medium 1. In addition, the optical module 50 may further include a sub-photo detector 55 to receive the incident light. The sub-photodetector 55 is disposed on the rear surface of the light source 51 and passes through the light transmission hole 32 of the light reflected from the recording medium 1, and is focused by the converging lens 65. Then, the light reflected from the reflective surface 64 is received. Therefore, by detecting the reproduction signal as the sum signal of the signal detected by the sub photodetector 55 and the signal detected by the main photodetector 70, the light sensitivity of the detection signal can be increased. The sub-photodetector 55 receives and monitors the light emitted to the rear edge of the light source 51 in addition to the detection of the reproduction signal, thereby stably controlling the light output of the light source 51. In order to electrically wire the optical module 50, a via hole may be formed in the upper slider 41, and the via hole may be filled with a conductor.

Although the light output from the light source 51 may proceed through the free space, it is preferable to proceed through the optical fiber 61 more preferably to reduce the light loss. The optical fiber 61 is installed in the mounting groove 42 formed on the optical path between the light source 51 and the reflective surface 64, and the clad 63 surrounding the core 62 and the core 62. ), And both end surfaces thereof are cut at right angles.

Here, the central axis of the core 62 of the optical fiber 61 and the center of the light emitted from the light source 51 coincide between the optical fiber 61 and the light source 51 and the optical coupling efficiency is improved. To this end, a spherical lens may be further provided, or the end portion of the core 62 may be processed into a lens. Since the optical coupling structure itself is widely known, its detailed description will be omitted.

In addition to the optical fiber 61, it is also possible to employ the above-described free space or thin film slab waveguide as a means for guiding light. In forming the thin film slab waveguide, the core must have a higher refractive index than the cladding. For example, the cladding may be SiO ₂ and the core may be SiNx, and the thin film slab waveguide may be formed by a silicon process.

The lower slider 31 and the upper slider 41 are bonded to an ultraviolet curable resin. Here, when the guide groove is provided in the upper and lower sliders 41 and 31 through etching, there is an advantage that the assembly is easy.

The light transmission hole 32 provided in the lower slider 31 is formed to have a smaller cross-sectional area from the upper slider 41 toward the recording medium 1, and has an inverted pyramid having an opening 65 at its apex. It is a hole of shape. The light transmitting hole 32 is formed by a photolithography patterning process and a wet anisotropic etching process, and the length of the opening 65 is approximately 100 nm or less. The ABS unevenness 31a formed on the bottom surface of the lower slider 31 is formed through photolithography and anisotropic RIE etching. The ABS unevenness 31a is formed by the flow of air in accordance with the rotation of the recording medium 1 and the substrate 10s to several hundreds of nm. Keep your distance constant and injure yourself.

The converging lens 65 is mounted in the light transmitting hole 32, and focuses and transmits incident light, and is preferably a spherical lens as shown. In the case of the spherical lens as described above, the light reflected from the four inclined side surfaces of the light transmitting hole 32 is focused to focus through the opening 35 to increase the efficiency of the near field light generated in the opening. have.

An upper surface of the lower slider 31, that is, a surface facing the upper slider 41, is a barrier film formed to prevent direct light and external light incident from the light source 51 toward the main photodetector 70. It is preferable that 33 is further provided.                     

4 and 5, the main photodetector 70 is divided into at least two around the light transmission groove, and is capable of independently photoelectric conversion of each of the light received by the divided photodetectors. have. This is to make it possible to detect the track error signal by differentially detecting the signals detected by each of the divided photodetectors. On the other hand, when detecting the reproduction signal, it is possible to detect by summing the signals detected by each of the divided photodetectors.

The main photodetector 70 is formed by the junction of the p-type semiconductor layer 71 and the n-type semiconductor layer 75, and the signals detected through the metal wirings 73 and 77 are output. Since the surface facing the recording medium 1 of the lower slider 31 on which the main photodetector 70 is installed must be flat, the metal wiring is etched and thin film deposited so as not to protrude. Here, the inlet depths of the p-type and n-type semiconductor layers 71 and 75 are set in consideration of the optical wavelength to be used and the kind of the lower slider 31, and are set to approximately several micrometers. Highly doped semiconductor layers 76 are surrounded around the p-type and n-type semiconductor layers 71 and 75. By forming the semiconductor layer 76, an ohmic contact with the wiring portion is formed, and the scattered light is reflected to be reincident to the p-type and n-type semiconductor layers 71 and 75 so as to have a signal strength. Can increase.

The operation of the near-field recording / reproducing optical head configured as described above is as follows.

First, at the time of near field light reproduction, light irradiated from the light source 51 is focused around the opening 35 by the converging lens 65 to form near field light. This near-field light is modulated by mutual scattering with the recording mark. The modulated light is detected through the main photodetector 70 and the sub photodetector 55. That is, since the distance between the opening 35 and the recording medium 1 is extremely small, several tens of nm, the light emitted at a low angle of about 70 degrees or less from the recording surface is almost all of the main light located around the opening 35. The remaining light received by the photodetector 70 and radiated at an angle of 70 degrees or more is focused by the spherical lens and reflected by the reflecting surface 64 to enter the sub photodetector 55. By summing the signals detected by the main photodetector 70 and the sub photodetector 55, the reproduction signal can be detected.

On the other hand, the main photodetector 70 is divided into at least two, so that the track error of the optical head with respect to the recording mark on the recording medium 1 according to the sign of the result value obtained by differentially receiving the light received by each of the divided photodetectors. Detect the degree. By actuating the optical head according to the detected track error signal, fine tracking can be precisely controlled during ultra high density recording.

As described above, the near-field recording / reproducing optical head according to the present invention can use a floating slider to obtain a higher data transfer rate than the near-field optical recording method of the conventional optical fiber probe scan type.

In addition, since the optical module, the optical fiber, the converging lens, and the main and sub photodetectors are installed in the upper and lower sliders, the optical axis can be easily adjusted, and the optical head can be reduced in size and weight. In addition, the photodetector includes a main photodetector around the opening and a sub photodetector for detecting light passing through the opening, thereby maximizing the intensity of the detected signal after being modulated and increasing the signal-to-noise ratio. . In addition, accurate and efficient tracking is possible by the two-segment photodetector disposed around the opening.

Claims (9)

A lower slider which travels while being floated on the recording medium by air dynamic pressure, and has a light penetrating hole through which incident light is transmitted; An upper portion having a reflective surface coupled to and installed on the lower slider and having a mounting groove in which an optical element is mounted on a surface facing the lower slider, is formed to be inclined at a predetermined inclination at an end of the mounting groove to reflect incident light. With a slider; A light source installed in the mounting groove and irradiating light toward the recording medium; A converging lens mounted in the light transmitting hole to focus and transmit the light passing through the light transmitting hole; And a main photodetector provided on one surface of the lower slider facing the recording medium to receive the light reflected from the recording medium. The method of claim 1, wherein the upper and lower sliders are made of a single crystal silicon material, And said mounting groove, said reflecting surface and said light transmitting hole are each formed by anisotropic etching. The optical head for near field recording and reproducing according to claim 1 or 2, further comprising an optical fiber for guiding light on an optical path between the light source and the reflective surface of the upper slide. The light source of claim 1, wherein the light source passes through the light transmission hole among the light reflected from the recording medium, receives light incident through the converging lens and the reflecting surface, and a part of the light irradiated from the light source. An optical head for near field recording and reproducing, further comprising a sub-photodetector configured to receive light. The optical head for near field recording and reproducing according to claim 1, wherein a reflective film having a relatively higher reflectance than that of the upper slider is formed on the reflective surface. The method of claim 1, wherein the light transmitting hole, An optical head for near field recording and reproducing, characterized in that the cross-sectional area becomes smaller from the upper slider toward the recording medium, and the length in one direction of the cross section facing the recording medium is about 100 nm or less. The optical head for near field recording and reproduction according to claim 1 or 6, wherein the converging lens provided in the light transmitting hole is a spherical lens. The near field recording and reproducing apparatus of claim 1, further comprising a blocking film on a side of the lower slider facing the upper slider to prevent the incident light and external light from being directed toward the main photodetector. Optical head. The method of claim 1, wherein the main photodetector, It is divided into at least two around the light transmission groove, it is possible to independently photoelectric conversion of each of the light received by each divided photodetector, it is possible to differentially detect the signal detected by each photodetector to detect the track error signal An optical head for near field recording and reproducing, characterized by the above-mentioned.

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