JP4678854B2 - Optical information recording / reproducing apparatus - Google Patents

Description

The present invention, by recording the interference fringes of light on the recording medium, about the optical information recording and reproducing equipment capable of recording information density and large capacity.

  Today, the world has entered the multimedia era, and the necessity of a recording device for recording on a recording medium and a recording / reproducing device for recording and reproducing on a recording medium is increasing in importance. It is rising. Also in the optical information recording medium, progresses such as CD (compact disc), DVD (digital versatile disc), and blue ray (blue ray) disc can be seen. Corresponding to the progress in optical information recording media, the recording density has been increased by shortening the wavelength of light used in optical information recording devices and optical information recording / reproducing devices using disks. In recent years, a new recording method called holographic memory has been proposed. The holographic memory records information by forming a hologram corresponding to information to be recorded in a recording medium. Due to the feature of using holograms, multiple recording is possible, and information can be reproduced independently from these holograms even if adjacent holograms have overlapping portions. Therefore, the holographic memory can achieve a high recording density that cannot be obtained by a conventional optical information recording medium.

  The holographic memory is explained in, for example, Non-Patent Document 1. FIG. 16 illustrates a conventional recording / reproducing apparatus using a holographic memory and an optical system of a coaxial type holographic memory system (optical information recording / reproducing apparatus) called a collinear method.

  This optical information recording / reproducing apparatus records and reproduces information on, for example, a disc-shaped hologram recording medium 216. Specifically, a volume hologram is formed in the recording medium 216 by simultaneously irradiating the recording medium 216 with signal light modulated by information and reference light not modulated by information to cause interference. Record. Further, by irradiating the recording medium 216 with weak reference light, a reproduction image of the volume hologram is acquired and information is reproduced. In addition, the volume hologram of the volume hologram of the recording medium is a method of actively using the thickness direction of the recording medium and writing interference fringes three-dimensionally. By increasing the thickness, the diffraction efficiency is increased. In this method, the recording capacity is increased by using multiple recording. The digital volume hologram is a hologram recording method in which image information to be recorded is limited to a binarized digital pattern while using a recording method similar to that of the volume hologram.

  The illustrated optical system includes a first light source 201 that generates laser light used for recording and reproducing information, and a spatial light modulator (hereinafter abbreviated as SLM) 204 for modulating signal light. And a two-dimensional light receiving element 219 for detecting reproduction light.

  First, a case where recording is performed on a disk-shaped recording medium 216 using the optical system will be described.

  A light beam emitted from the first light source 201 made of a green laser or the like is converted into a parallel light beam by the collimator 202 and illuminates the SLM 204 via the mirror 203. In FIG. 16, a DMD (Deformable Mirror Device) is used as the SLM 204. Such an SLM 204 has a large number of light modulation elements (pixels) arranged two-dimensionally, and can represent “0” and “1” for each pixel. In the SLM 204, the light reflected by the pixel representing the information “1” is reflected in the direction of the recording medium 216, and the light reflected by the pixel representing the information “0” is not reflected in the direction of the recording medium 216. In the SLM 204 used in the collinear holographic memory system, the central portion is a portion that modulates the information light 206, and the portion surrounding the ring is a portion that modulates the reference light 205.

  Both the information beam 206 and the reference beam 205 reflected by the pixel representing the information “1” in the SLM 204 pass through a polarization beam splitter (hereinafter abbreviated as PBS) 207 as P-polarized light. Then, the light is directed to the recording medium 216 via a first relay lens 208, a mirror 209, a second relay lens 210, and a dichroic beam splitter (hereinafter abbreviated as DBS) 211. After passing through the DBS 211, the reference light 205 and the information light 206 that have been transmitted through a quarter-wave plate (hereinafter abbreviated as QWP) 212 and converted into circularly polarized light (for example, clockwise circularly polarized light) are reflected by a mirror 213. The light is reflected and enters the objective lens 214 having a focal length F. The pattern displayed on the SLM 204 forms an intermediate image in front of the objective lens 214 by F by the first and second relay lenses 208 and 210. As a result, a 4F optical system is configured in which a pattern image (not shown) on the SLM 204, the objective lens 214, and the recording medium 216 are all separated by a distance of F.

  A disk-shaped recording medium 216 is rotatably held on a spindle motor 215. The reference light 205 and the information light 206 are collected on the recording medium 216 by the objective lens 214 and interfere to form interference fringes. On the polymer material in the recording medium 216, the interference fringe pattern at the time of recording is recorded as a refractive index distribution, and as a result, a digital volume hologram is formed. When the information light 206 is modulated by the SLM 204 according to information to be recorded, a digital volume hologram corresponding to the information is formed on the recording medium 216. In particular, if modulation is performed for each pixel according to information to be recorded in the information light region of the SLM 204, a digital volume hologram having an information amount corresponding to the number of pixels is formed on the recording medium 216. Become. Note that a reflective film is provided in the recording medium 216.

  In addition to the first light source 201 that records and reproduces the holographic optical information, the optical information recording / reproducing apparatus is provided with a second light source 220 including a red laser having no sensitivity to the recording medium 216. . Using the second light source 220, it is possible to detect the displacement of the recording medium 216 with high accuracy using the reflective film of the recording medium 216 as a reference plane. As a result, even if surface blurring or eccentricity occurs in the recording medium 216, it is possible to dynamically follow the recording spot using the optical servo technology, and to record the interference fringe pattern with high accuracy. it can. Hereinafter, such tracking will be briefly described.

  A linearly polarized light beam emitted from the second light source 220 made of a red laser or the like is transmitted through a beam splitter (hereinafter abbreviated as BS) 221, converted into a parallel light beam by a lens 222, and reflected by a mirror 223 and a DBS 211. , Directed to the recording medium 216. The light beam that has been transmitted through the QWP 212 and converted into circularly polarized light (for example, clockwise circularly polarized light) is reflected by the mirror 213 and enters the objective lens 214, and is collected as a minute light spot on the reflective film of the recording medium 216. To be lighted. The reflected light beam becomes reversely circularly polarized light (for example, counterclockwise circularly polarized light), re-enters the objective lens 214 to become a parallel light beam, is reflected by the mirror 213, passes through the QWP 212, and is polarized in the forward path. Is converted into a vertical linearly polarized light beam. The light beam reflected by the DBS 211 is reflected by the BS 221 through the mirror 223 and the lens 222 in the same way as the forward path, and is guided to the photodetector 224. The photodetector 224 has a plurality of light receiving surfaces and detects position information of the reflecting surface, and can focus and track the objective lens 214 based on the detection result. Such focusing and tracking is the same as that performed in a conventionally well-known optical information recording / reproducing apparatus using a CD or DVD.

  Next, a case where information recorded on the recording medium 216 is reproduced using the optical system will be described. The light beam emitted from the first light source 201 illuminates the SLM 204 as in recording. During reproduction, only the portion of the SLM 204 that modulates the reference light 205 displays “1” information, and all the portions that modulate the information light 206 display “0” information. Therefore, only the light reflected by the pixels of the reference light 205 is reflected in the direction of the recording medium 216, and the information light 206 is not reflected in the direction of the recording medium 216.

  As in the recording, the reference light 205 is circularly polarized (for example, clockwise circularly polarized light), collected on the recording medium 216, and information light is reproduced from the recorded interference fringes (digital volume hologram). The information light reflected by the reflective film in the recording medium 216 becomes reversely circularly polarized light (for example, counterclockwise circularly polarized light), reenters the objective lens 214 to become a parallel light beam, and is reflected by the mirror 213. The light passes through the QWP 212 and is converted into a linearly polarized light beam (S-polarized light) perpendicular to the forward polarized light. At this time, an intermediate image of the display pattern of the SLM 204 reproduced at a distance F from the objective lens 214 is formed.

  The light beam that has passed through the DBS 211 is directed to the PBS 207 via the second relay lens 210, the mirror 209, and the first relay lens 208. The light beam reflected by the PBS 207 is re-imaged as an intermediate image of the display pattern of the SLM 204 at a position conjugate with the SLM 204. An opening 217 is previously placed at this position, and unnecessary reference light around the information light is shielded. The intermediate image re-formed by the lens 218 forms a display pattern of the SLM 204 only on the information light portion on the light receiving element 219 such as a CMOS sensor. Thereby, since unnecessary reference light 205 does not enter the light receiving element 219, a reproduction signal having a good S / N (signal-to-noise ratio) can be obtained.

  Eventually, in this optical information recording / reproducing apparatus, information to be recorded is developed into two-dimensional digital pattern information, and information light is modulated by this two-dimensional digital pattern information. By this processing, information light in which the recorded information becomes the light intensity distribution image information in the two-dimensional space is generated. Then, the interference fringes are recorded on the recording medium by causing the information light and the reference light to interfere with each other. At the time of reproduction, two-dimensional digital pattern information is extracted from the light intensity distribution image information reproduced by irradiating the reference light and decoded. This digital processing makes it possible to suppress a reduction in the reproduction error rate due to the deterioration of the S / N ratio, and reproduces recorded information with high fidelity by encoding binary data and performing error correction. It becomes possible.

In the collinear holographic memory system described above, the information light and the reference light have a coaxial optical arrangement with no angle, so that recording / reproduction can be performed using one objective lens. Therefore, there is an advantage that the optical system is simplified as compared with the biaxial two-beam interference method in which the recording medium is irradiated with the information light and the reference light from different optical paths. Further, the structure of the recording medium having the reflective film has an advantage that the optical system can be arranged on one side of the disk-shaped recording medium.
Hideyoshi Horime et al., “Holographic Media Near Takeoff Realizing 200 GB in 2006”, Nikkei Electronics 891, pages 105-114, January 17, 2005

  However, in a conventional holographic memory system, a transmissive liquid crystal element is generally used as a spatial light modulation element (SLM) although it is slightly different from the DMD or the optical system described above. In the case of using a transmissive liquid crystal element, there is an advantage that the optical system becomes easy, but there are problems of miniaturization and high speed due to the liquid crystal element. On the other hand, when DMD is used, there is a concern that cost reduction is difficult due to the complexity of the manufacturing method of DMD, and there is a problem of miniaturization.

  In view of the above-described problems, the present invention is a reflection type for operating at high speed and miniaturizing in a spatial light modulation element used in a holographic memory system, and for reducing the cost with a simple structure. A spatial light modulator is proposed.

That is, an object of the present invention is to realize an optical information recording / reproducing apparatus including a spatial light modulator that operates at high speed and can be miniaturized, and further achieves cost reduction with a simple structure.

The optical information recording / reproducing apparatus of the present invention records information on a recording medium by forming interference fringes generated by interference between information light and reference light on the recording medium, and applies the reference light to the recording medium to apply the interference fringes. In an optical information recording apparatus that reads and reproduces information light, and has a plurality of modulation elements that change the intensity of reflected light according to a modulation signal, and modulates at least a part of a light beam emitted from the light source to obtain information light, A spatial light modulator for modulating at least a part of the recording light into a reference light, an optical system for causing the reference light and the information light to interfere at a predetermined depth of the recording medium, and a reference light from the light source of the recording medium. An optical system for reproducing information light from interference fringes at a predetermined depth and extracting the reproduced information light; a light receiving element; and an optical system for introducing the extracted information light to the light receiving element. The modulation element reflects the light from the light source And electrode morphism, and the semi-transmissive film exhibiting semi-transparent to light from the light source is arranged through the space to the light source side of the reflective electrodes, for maintaining the distance between the reflective electrode and the semi-permeable membrane And a columnar insulating film provided only at the position corresponding to the peripheral edge of the reflective electrode, and by controlling the distance between the reflective electrode and the semi-transmissive film, the reflectance of light from the light source changes, and the spatial light The modulation element and the light receiving element are integrally formed on the same substrate, and the spatial light modulation element is disposed on the surface of the substrate on which the light receiving element is formed .

  In the present invention, the distance between the reflective electrode and the semi-transmissive film is preferably controlled for each modulation element. Specifically, a means for applying a voltage between the reflective electrode and the semi-transmissive film is provided, and the reflective electrode and the semi-transmissive film are formed according to the applied voltage by electrostatic attraction between the reflective electrode and the semi-transmissive film. It is preferable to change the interval of. In this case, a semi-transmissive film can be provided as a common electrode provided in common for a plurality of modulation elements, and a control voltage can be applied to the reflection electrode for each modulation element. In the spatial light modulation element, for example, the modulation elements are arranged in a line shape or a matrix shape.

  In the present invention, the interference fringes formed on the recording medium are preferably digital volume holograms. Therefore, it is preferable that the modulation element modulates light from the light source into binary information.

In the present invention, the substrate is preferably a single crystal silicon substrate. By forming the reflective electrode on the single crystal silicon substrate, high-speed driving is possible, and an optical information recording apparatus with high recording density can be realized. The semipermeable membrane is made of a material containing Ti, for example. In order to increase the displacement with respect to the applied voltage in such a semi-transmissive film, the semi-transmissive film may have a structure in which each pixel is connected with a thin structure as compared with the pixel region. Furthermore, such a thin structure in the semipermeable membrane can be provided at a plurality of locations.

In the optical information recording / reproducing apparatus of the present invention, the reference light can be reflected from the spatial light modulation element by a dummy element that is in the same plane as the modulation element and has the same structure as the modulation element.

According to the present invention, the spatial light modulation element is configured by using the modulation element including the reflection electrode and the semi-transmissive film disposed in front of the reflection electrode through the space. The optical information recording / reproducing apparatus can be provided at a low cost.

According to the present invention, because it uses one having a simple structure as a spatial light modulator, it is possible to provide a high have the optical information recording and reproducing apparatus of reliability at low cost. Further, since the spatial light modulation element and the light receiving element can be formed on the same chip, it is not necessary to align the both, and it is possible to provide a low-cost and highly reliable optical information recording / reproducing apparatus. .

  Next, a preferred embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
In describing the optical information recording / reproducing apparatus according to the first embodiment of the present invention, first, a spatial light modulation element used in the optical information recording / reproducing apparatus will be described. In the present embodiment, the spatial light modulation element is configured using a reflection type interferometric modulation element. FIG. 1 is an equivalent circuit diagram for explaining the spatial light modulator in the present embodiment.

  This spatial light modulation element includes a plurality of unit modulation elements (pixels) arranged two-dimensionally so that light “0” and “1” can be modulated for each pixel. A plurality of vertical signal lines and a plurality of driving lines (scanning lines) form a matrix wiring, and the intersection positions of the vertical signal lines and the driving lines correspond to pixels, respectively. Each pixel includes a pixel switch including a switching transistor, an interference structure unit, and a storage capacitor. The gate of the pixel switch is connected to the corresponding drive line, and the drain is connected to the corresponding vertical signal line. The storage capacitor is provided between the source of the pixel switch and a constant potential point (for example, a ground potential point). Furthermore, the interference structure is also connected to the source of the pixel switch. In FIG. 1, two vertical signal lines 301 and 302 and two drive lines 315 and 316 are shown, and an area for four pixels is shown. These four-pixel pixel switches are denoted by reference numerals 303 to 306, the interference structure portions are denoted by reference numerals 307 to 310, and the storage capacitors are denoted by reference numerals 311 to 314. Each interference structure portion also includes a common counter electrode 322 common to each pixel.

  One ends of the vertical signal lines 301 and 302 are connected in common to the horizontal signal line 319 via sampling switches 320 and 321, respectively. The gates of the sampling switches 320 and 321 are connected to the horizontal shift register 317. One ends of the drive lines 315 and 316 are connected to the vertical shift register 318.

  In FIG. 1, the pixels are arranged in 2 rows and 2 columns. However, the spatial light modulator in this embodiment can be a multi-pixel matrix such as 1000 rows and 1000 columns, and in this case, the same applies. It has a configuration.

  Hereinafter, the circuit operation of the spatial light modulator using the reflection type interferometric modulator in the present embodiment will be described.

  First, an on signal is input from the vertical shift register 318 to the drive line 315 to turn on the pixel switches 303 and 304. In this state, the horizontal shift register 317 sequentially operates to transmit a signal from the horizontal signal line 319 to the vertical signal lines 301 and 302. That is, first, the sampling switch 320 is turned on, and the signal of the horizontal signal line 319 is written to the vertical signal line 301. Then, in the interference structure unit 307, charges are accumulated in the storage capacitor 311 through the pixel switch 303, and an electric field is generated between the common counter electrode 322. The interference structure 307 is changed by this electric field, and the reflectance with respect to incident light is modulated to a desired value. Next, after the sampling switch 320 is turned off, the sampling switch 321 is turned on, and the signal of the horizontal signal line 319 is written to the vertical signal line 302 and then written to the storage capacitor 312 through the pixel switch 304. In this sequence, signals are sequentially written to the pixels in the X direction (the horizontal direction in the figure). After writing all the rows, the drive line 315 is turned off, and an on signal is input to the drive line 316 this time, and the pixel switches 305 and 306 are turned on. Thereafter, writing is performed sequentially in the horizontal direction as described above. After signals are written in all the rows arranged in the Y direction (vertical direction in the figure), this operation is repeated from the first row to rewrite the signals of the respective pixels.

  FIG. 2 is a cross-sectional view of a pixel portion (interference structure portion) of a spatial light modulation element using the reflection type optical interference modulation element in the present embodiment.

  The reflective interferometric modulation element according to the present embodiment includes a reflective electrode 330 that reflects light for each pixel (interference structure), and a transflective member that is disposed in front of the reflective electrode 330 and has translucency with respect to light. A film 331 is provided. The semi-transmissive film 331 is provided over a plurality of pixels and functions as the common counter electrode 322 described above. In the semi-transmissive film 331, a portion of the incident light that has not been transmitted is reflected. In this configuration, by changing the spatial distance (air gap) between the reflective electrode 330 and the semi-transmissive film 331, interference between the reflected light reflected by the reflective electrode 330 and the reflected light reflected by the semi-transmissive film 331 is achieved. Thus, the intensity of the reflected light as a whole can be controlled. The semi-transmissive film 331 can be made of a thin film metal material having a thickness of about 5 nm to 15 nm, for example, Ti, but is not particularly limited to Ti. In order to maintain the distance between the reflective electrode 330 and the semi-transmissive film 331, a columnar insulating film 332 is provided between them. The insulating film 332 is preferably provided only at the position of the gap between the reflective electrodes 330 of adjacent pixels. For example, a silicon nitride film is used as the insulating film 332. A protective film 333 made of, for example, a silicon oxide film is provided on the entire surface of the semi-transmissive film 331 that is not opposed to the reflective electrode 330.

  The reflective electrode 330 is preferably made of a material having a high light reflectance, such as Al, AlSi, AlCu, Ti, Ta, W, Ag, Pt, Ru, Ni, Au, TiN, or a metal film thereof. These compound films or laminated films can be used. However, the material of the reflective electrode 33 is not limited to these. The insulating film 332 and the protective film 333 may be formed of different materials or the same material, and there is no electrical problem as long as the insulating material is used, and the material is not particularly limited. The reflective electrode 330 is provided for each pixel and is connected to the source of the pixel switch in the equivalent circuit shown in FIG.

  Next, the operation of the interference structure will be described with reference to FIG.

  First, a ground potential of 0 V, for example, is applied to the common electrode of the semipermeable membrane 331. With the active matrix operation described with reference to FIG. 1, a voltage corresponding to a signal is applied to the reflective electrode 330, and a potential difference is generated between the reflective electrode 330 and the semi-transmissive film 331. The air gap between the reflective electrode 330 and the semi-transmissive film 331 changes for each pixel due to the Coulomb force generated by the potential difference.

  FIG. 3 shows the reflectance values of light incident from the semi-transmissive film 331 side when the thickness of the semi-transmissive film 331 is 10 nm and the air gap is 180 nm and when the air gap is 30 nm. It is the graph which showed the wavelength of light on the axis | shaft on the horizontal axis. As can be seen from FIG. 3, when the air gap changes from 30 nm to 180 nm in accordance with the voltage of the signal applied to the reflective electrode 330, the reflectivity changes greatly accordingly. This is due to the interference action between the light reflected by the reflective electrode 330 and the light reflected by the semi-transmissive film 331. This interference action can be designed according to the wavelength of light, the material of the semi-transmissive film, and the air gap. It is. Therefore, it is important to take a necessary configuration as the interference structure in view of physical strength in the dry structure and characteristics such as a contrast ratio required in the reflected light.

  Such a spatial light modulator is formed on the surface of a silicon semiconductor substrate using a semiconductor device manufacturing technique. That is, after forming the above-described wirings, pixel switches, and storage capacitors on the semiconductor substrate, the reflective electrode 330 is provided so as to cover those wirings, pixel switches, and storage capacitors. In the example shown in FIG. 2, the reflective electrode 330 is provided on the surface of the silicon substrate via an interlayer insulating film. A base wiring layer 334 is provided below the reflective electrode 330 and is electrically connected to the reflective electrode 330 via a plug 336 penetrating the interlayer insulating film. Further, the interlayer insulating film is used to prevent light incident on the spatial light modulation element using the reflection type interferometric modulation element from reaching the region of the transistor, which is a pixel switch disposed below the interference structure. A light shielding film 335 is provided.

  FIGS. 4A and 4B are a plan view and a perspective view, respectively, of such a reflection type interferometric modulation element. Here, a region corresponding to two pixels is shown, and the pixel on the left side in the figure is the reflection type optical interference modulation element 40 in the black display state, and the pixel on the right side in the figure is the reflection type optical interference modulation element 41 in the white display state. It is. Here, it is shown that a semi-transmissive film 42 is provided on the entire surface so as to straddle these pixels. The example shown in FIG. 4 is an example in which a signal is written by digital display. In the reflection type interferometric modulation element 41, the air gap at the center is narrowed and the reflectance is increased and whitened. By forming such a pattern of “0” and “1”, it can be recorded information. The region between adjacent pixels (reflection type interferometric modulation elements) 40 and 41 can be black or white, depending on the structure. However, from the viewpoint of application to a holographic memory system, it can be said that there is no disturbance if the area between adjacent pixels is black. Making the region between the elements black can be realized by laminating a light absorption layer below the reflective electrode 330.

  When the signal voltage applied to the reflective electrode 331 is continuously modulated in an analog manner, the air gap between the reflective electrode 330 and the semi-transmissive film 331 also changes continuously, and the reflectivity also varies depending on the air gap. Since it changes continuously, it can also be analog recording information.

  FIG. 5 is a plan view of a semiconductor chip having a spatial light modulator using the reflection type interferometric modulator as described above. Here, since the spatial light modulator is used for the collinear holographic memory system, a reflection region (reference light region 45) for reference light is also provided. Since the reference light region 45 only needs to reflect light in a white state at all times, the semi-transmissive film 42 is not provided in this region. On the other hand, in the information light region 46, the semi-transmissive film 42 is disposed and a reflection type interferometric modulation element is provided. In the present embodiment, the reference light region 45 is arranged around the information light region 46. As a result, the configuration of the optical system itself is simplified, and both information light and reference light can be formed using a single spatial light modulator.

  Next, a method for manufacturing a spatial light modulator using the reflection type interferometric modulator described above will be briefly described.

The n-type single crystal silicon semiconductor substrate is partially thermally oxidized to form a LOCOS (Local Oxdation of silicon) oxide film. Next, boron (B) is ion-implanted with a dose of about 10 ¹¹ cm ^{−2 using the} LOCOS oxide film as a mask to form a p-type well which is a p-type impurity region. This substrate is thermally oxidized again to form a gate oxide film having a thickness of 60 nm.

Next, after forming a gate electrode made of n-type polysilicon doped with phosphorus (P) at about 10 ²⁰ cm ⁻³ , phosphorus is ion-implanted at a dose of about 10 ¹³ cm ⁻² to obtain an impurity concentration. An n-type lightly doped drain that is an n-type impurity region of about 10 ¹⁸ cm ⁻³ is formed. Subsequently, using the patterned photoresist as a mask, phosphorus is ion-implanted at a dose of about 10 ¹⁵ cm ⁻² to form source / drain regions having an impurity concentration of about 10 ²⁰ cm ^−3, thereby forming an nMOS transistor. Similarly, a pMOS transistor is formed. Thereafter, an interlayer insulating film (not shown) is formed on the entire surface of the substrate. The interlayer insulating film can be a PSG (Phospho-silicate Glass) film, NSG (Nondope Silicate Glass) / BPSG (Boro-Phospho-Silicate Glass) film, or a CVD (chemical vapor deposition) film using TEOS (tetraethoxysilane). Etc. can be used, and is not particularly limited.

  Next, a contact hole is patterned immediately above the source / drain region, an aluminum (Al) layer is deposited by sputtering or the like, and then patterned to form a base wiring layer 334. In order to improve ohmic contact characteristics between the underlying wiring layer 334 and the source / drain regions, it is desirable to form a barrier metal such as Ti / TiN between the underlying wiring layer 334 and the source / drain regions. Thereafter, an interlayer insulating film is formed, and further a light shielding film 335 is formed of a metal film. For the light shielding film 335, for example, a metal film such as Ti, TiN, Al, or Ag or a laminated film thereof can be used, and is not particularly limited. After the light shielding film 335 is patterned, an interlayer insulating film is further formed, and a contact hole is opened at a predetermined position on the base wiring layer 334. Next, after depositing tungsten in the contact hole, the plug 336 is formed by planarization by CMP (chemical mechanical polishing).

  Thereafter, a metal layer is deposited to a thickness of about 300 nm by sputtering, and patterned to form the reflective electrode 330. Next, a silicon nitride film is formed to a thickness of 300 nm by plasma CVD, and a columnar insulating film 332 is formed by etching after patterning. Then, after applying and planarizing a resist, the planar insulating layer 332 having a height of about 180 nm is planarized so as to remain uniformly. Next, a Ti layer is deposited to a thickness of 10 nm and a silicon oxide film is deposited to a thickness of 300 nm by a low temperature sputtering method. After patterning, the silicon nitride film and the Ti layer are etched by dry or wet etching, and then the resist is removed by wet etching to form a semi-transmissive film 331 and a protective film 333. Thereafter, the electrode is taken out by wire bonding.

  Through such a manufacturing process, a spatial light modulation element having a reflection type optical interference modulation element could be manufactured.

(Second Embodiment)
FIG. 6 is a plan view of a reflection type interferometric modulation element according to the second embodiment of the present invention. In the first embodiment, the semi-transmissive film is provided uniformly on the entire surface across the pixels. On the other hand, in the present embodiment, the joint in the semi-transmissive film 47 is narrowed at a position between the adjacent reflective interferometric modulation elements (pixels) 40 and 41 so that the semi-transmissive film 47 can be driven at a low voltage. Thus, a reflection type optical interference modulation element was formed. FIG. 7 is a graph showing voltage-reflectance characteristics with the signal voltage in the reflective interferometric modulation element as the horizontal axis and the reflectance as the vertical axis. In FIG. 7, the characteristics of the element having the semi-transmissive film 42 uniformly formed on the entire surface shown in the first embodiment are indicated by A, and the semi-transmissive film 47 formed by narrowing the joint between pixels in this embodiment. The characteristics of the element having λ are shown as B. From FIG. 7, it can be seen that the reflection type interferometric modulation element of the present embodiment can be driven at a lower voltage and the reflectance of the element is increased as compared with the uniform shape of the entire surface. This is because an area in which the air gap becomes narrower in one reflective light modulation element becomes large, and can be said to be an element having a large white state aperture ratio. In holographic recording, the higher the contrast between white and black of the information light, the higher the contrast of the holographic interference fringes. Therefore, by using the reflection type interferometric modulation element of this embodiment, reading with less errors during reproduction is possible. It becomes possible.

(Third embodiment)
FIG. 8 is a plan view of a reflective interferometric modulation element according to the third embodiment of the present invention. Here, as in the second embodiment, the joint of the semi-transmissive film is narrowed at a position between the adjacent reflective interferometric modulation elements (pixels) 40 and 41 so that the semi-transmissive film can be driven at a low voltage. However, the shape of the joint is different from that of the second embodiment. That is, in order to improve the reliability when holding the semi-transmissive film 42, the semi-transmissive film 42 is configured so as to be separated into three parallel seams in the region between adjacent pixels. Thus, by providing the seam at a plurality of locations, a stable planar structure in the semipermeable membrane 42 is realized.

  The preferred reflection type interferometric modulation element of the present invention has been described above. This interferometric modulation element modulates light intensity by utilizing light interference. Therefore, the flatness of the surface of the semi-transmissive film and the reflective electrode is an important factor. If the flatness of the surface is poor and the light reflection direction changes slightly, the interference fringes due to the hologram change accordingly from the desired one. Resulting in. In the optical information recording apparatus or the optical information recording / reproducing apparatus of the present invention, as the spatial light modulation element, one having the element structure shown in the first to third embodiments can be arbitrarily selected. It is not limited to. For example, it is possible to use a spatial light modulation element configured by combining the reflection type optical interference modulation elements of the first to third embodiments.

(Fourth embodiment)
Next, an optical information recording / reproducing apparatus based on the present invention using the above-described spatial light modulation element based on the present invention will be described. The optical information recording / reproducing apparatus according to the present embodiment is configured as a collinear holographic memory system, and includes a spatial light modulation element and a light receiving element such as a CMOS image sensor for detecting reproduction light in the same semiconductor. It is formed on a chip. 9 to 11 are diagrams for explaining an optical system of the optical information recording / reproducing apparatus according to the present embodiment. FIG. 9 shows an optical system from the light source to the spatial light modulation element at the time of recording, FIG. 10 shows an optical system from the spatial light modulation element to the hologram disk (recording medium) at the time of recording, and FIG. The optical system of time is shown.

  The optical information recording / reproducing apparatus of the present embodiment records information by writing volume holograms on, for example, a disk-shaped hologram recording medium 186, and reproduces information by acquiring reproduced images of volume holograms. Is. The illustrated optical system includes a first light source 101 that generates laser light used for recording and reproducing information, a spatial light modulation element (SLM) for modulating signal light, and a two-dimensional structure for detecting reproduced light. And a modulation / light-receiving element (SLM / CMOS) 108 provided integrally therewith. As the SLM portion in the modulation / light receiving element 108, the spatial light modulation element having the reflection type interferometric modulation element described in the first to third embodiments is preferably used. A light receiving cell (for example, a photodiode) corresponding to each pixel is arranged in the area of the adjacent reflection type interferometric modulation element (pixel), and thereby, the light modulation by the SLM and the light reception by the light receiving element are coaxial. Can be done with. As will be described later, since it is only necessary to detect an optical image pattern only in the information light region at the time of reproduction, the light receiving element may be disposed only in the information light region in the SLM. Alternatively, as will be described later, a spatial light modulation element made of a reflective interferometric modulation element and a light receiving element are integrated in the vertical direction on a silicon semiconductor substrate (in other words, both are laminated). May be.

  First, the case where recording is performed on the recording medium 118 will be described with reference to FIGS. In FIG. 9, the light beam emitted from the first light source 101 made of a green laser or the like is converted into a parallel light beam by the collimator 102 and enters the mask element 103. The mask element 103 has a function of masking a portion corresponding to the information light at the center of the light beam. You may insert the mask which shields the center part of a light beam into an optical path. At the time of recording information, the mask element 103 does not function and transmits all light beams. The light transmitted through the mask element 103 enters a polarization beam splitter (hereinafter abbreviated as PBS) 104.

  The light beam transmitted through the PBS 104 as P-polarized light is transmitted through a quarter-wave plate (hereinafter abbreviated as QWP) 105 and converted into circularly-polarized light (for example, clockwise circularly-polarized light), and the first relay lens 106 and The light is applied to the modulation / light receiving element 108 via the second relay lens 107. The light reflected by the pixel representing the information “1 (white)” by the SLM in the modulation / light receiving element 108 is reflected toward the recording medium 118 with a high reflectance, and the information “0 (black)” of the SLM is reflected. The light reflected by the pixel representing is slightly reflected in the direction of the recording medium 118 due to interference. Similar to the conventional example and as shown in FIG. 5, the collinear SLM is provided with a portion for modulating the information light 110 and a portion for modulating the reference light 109 surrounding the information light 110 in a ring shape.

  In the following, referring to FIG. 10, the light beam reflected by the SLM of the modulation / light receiving element 108 is reversely circularly polarized light (for example, counterclockwise circularly polarized light). The light flux that has passed through the second relay lens 107 and the first relay lens 106 passes through the QWP 105 and is converted to S-polarized light, and is reflected by the PBS 104 and directed toward the recording medium 118.

  In the SLM of the modulation / light receiving element 108, the information light 110 and the reference light 109 reflected by the pixel representing the information “1” are reflected by the PBS 104, and the third relay lens 111, the mirror 112, and the fourth relay. It is directed to the recording medium 118 via a lens 113 and a dichroic beam splitter (hereinafter abbreviated as DBS) 114, reflected by a mirror 115, and incident on an objective lens 116 having a focal length F. The pattern displayed on the SLM of the modulation / light receiving element 108 forms an intermediate image in front of the objective lens 116 by F by the third and fourth relay lenses 111 and 112. As a result, the 4F optical system in which the pattern image (not shown) on the SLM of the modulation / detection element 108, the objective lens 116, and the recording medium 118 are all separated by a distance of F is configured. Become.

  A disk-shaped recording medium 118 is rotatably held on a spindle motor 117. The reference light 109 and the information light 110 are collected on the recording medium 118 by the objective lens 116 and interfere to form interference fringes. On the polymer material in the recording medium 118, the interference fringe pattern at the time of recording is recorded as a refractive index distribution, and a digital volume hologram is formed. In particular, if the information light 110 is modulated according to information to be recorded, a digital volume hologram corresponding to the information is formed on the recording medium 118. Note that a reflective film is provided in the recording medium 118.

  Similar to the conventional one, the optical information recording / reproducing apparatus of the present embodiment includes a red laser having no photosensitivity to the recording medium 118 in addition to the first light source 101 for recording / reproducing the holographic optical information. A second light source 119 is provided. Using the second light source 119, it is possible to detect the displacement of the recording medium 118 with high accuracy using the reflective film of the recording medium 118 as a reference plane. As a result, even if surface blurring or eccentricity occurs in the recording medium 118, it is possible to dynamically follow the recording spot using the optical servo technology, and an interference fringe pattern (digital volume hologram) with high accuracy. Can be recorded. Briefly described below.

  A light beam emitted from the second light source 119 passes through a beam splitter (hereinafter abbreviated as BS) 120, is converted into a parallel light beam by a lens 121, is reflected by a mirror 122 and a DBS 114, and is directed to a recording medium 118. . Thereafter, the light is reflected by the mirror 115, enters the objective lens 116, and is condensed as a minute light spot on the reflection film of the recording medium 118. The reflected light beam re-enters the objective lens 116 to become a parallel light beam, is sequentially reflected by the mirror 115 and the DBS 114, passes through the mirror 122 and the lens 121 in the same way as the forward path, and a part of the light beam is transmitted by the beam splitter BS120. The light is reflected and guided to the photodetector 123. The photodetector 123 has a plurality of light receiving surfaces, and can detect the position information of the reflecting surface by a known method, and focus and track the objective lens 116 based on the detected position information.

  Next, the operation for reproducing information recorded as a digital volume hologram on the recording medium 118 will be described with reference to FIG. The light beam emitted from the first light source 101 is applied to the modulation / light receiving element 108 in the same manner as in recording. At this time, the intensity of light from the first light source 101 is set to be smaller than the intensity used at the time of recording so as not to destroy the information recorded on the recording medium 118. During reproduction, the mask element 103 masks a portion corresponding to the information light at the center of the light beam.

  The first relay lens 106 and the second relay lens 107 serve to form an image of the mask element 103 on the SLM of the modulation / light receiving element 108. Thereby, only the element of the reference light portion is illuminated, and the information light portion is properly shielded by the image of the mask element 103. In the SLM of the modulation / light receiving element 108, only the portion that modulates the reference light 109 displays “1 (white)” information, and all the portions that modulate the information light 110 display “0 (black)” information. indicate. Therefore, only the light reflected by the pixel of the portion that modulates the reference light 109 is reflected toward the recording medium 118. Since the luminous flux of the pixels that reflect the information light 110 is not reflected in the direction of the recording medium 118, it is not even illuminated, so that it is possible to reproduce information light with a much better S / N compared to the conventional example. .

  As in the recording, the reference light 109 is reflected by the PBS 104, collected on the recording medium 118, and information light is reproduced from the recorded interference fringes. Information light (that is, reproduction light) reflected by the reflective film in the recording medium 118 is incident again on the objective lens 116 to be converted into a parallel light beam and reflected by the mirror 115. At this time, an intermediate image of the display pattern of the SLM reproduced at a distance F from the objective lens 116 is formed.

  The light beam transmitted through the DBS 114 is directed to the PBS 104 via the fourth relay lens 113, the mirror 112, and the third relay lens 111, and is masked by the fourth relay lens 113 and the third relay lens 111. The image is re-imaged as an intermediate image of the SLM display pattern at a position conjugate with 103 (not shown). The re-imaged intermediate image is reflected by the PBS 104 and formed on the modulation / light receiving element 108 by the first relay lens 106 and the second relay lens 107. As described above, the light receiving element portion of the modulation / light receiving element 108 is disposed only between the pixels of the portion illuminated with the information light. In the present embodiment, a CMOS sensor having a photodiode and a MOS transistor that amplifies a light reception signal detected by the photodiode is used for each pixel as the light receiving element.

  By using the mask element 103 as described above, in this optical information recording / reproducing apparatus, unnecessary reference light does not enter the area between the pixels of the information light portion where the light receiving element is formed. A good reproduction signal can be obtained.

  Next, the recording / reproducing circuit operation in the optical information recording / reproducing apparatus of the present embodiment will be described. FIG. 12 is an equivalent circuit diagram for explaining a modulation / light-receiving element in which an SLM using a reflection type interferometric modulation element and a light-receiving element made of a CMOS sensor are integrated, used in this embodiment. In FIG. 12, reference numerals 1 to 10 are assigned to components related to the spatial light modulator, and reference numerals 21 to 33 are assigned to components related to the light receiving element configured as a CMOS image sensor.

  Are provided with a plurality of vertical signal lines 1, 1a,... Extending in the column direction (vertical direction in the figure) and a plurality of drive lines (scanning lines) 2, 2a,. Matrix wiring is configured, and intersections of vertical signal lines and drive lines correspond to pixels, respectively. Accordingly, the pixels are arranged in a matrix, and a vertical signal line is provided for each column of the pixel array, and a drive line is provided for each row. The vertical signal lines 1, 1a,... Are for spatial light modulation elements, and similarly, vertical signal lines 26, 26a,... For light receiving elements are provided for each column. Further, horizontal read lines 27, 27a,..., Horizontal reset lines 28, 28a,..., Horizontal selection lines 29, 29a,.

  Each pixel is provided with pixel switches 3, 3a,... Made of switching transistors, interference structures 4, 4a,... And holding capacitors 5, 5a,. In addition, each pixel includes a photodiode 21, 21, a,..., A transfer switch 22, 22a,..., A transistor, a reset switch 23, 23a,. 24a,... And selection switches 25, 25a,.

  In the spatial light modulation element portion of each pixel, the gates of the pixel switches 3, 3a,... Are connected to the corresponding drive lines 2, 2a,..., And the drains are connected to the corresponding vertical signal lines 1, 1a,. The holding capacitors 5, 5a,... Are provided between the source of the pixel switch and a constant potential point (for example, a ground potential point). Further, the interference structures 4, 4a,... Are also connected to the source of the pixel switch. Each interference structure portion also includes a common counter electrode 6 common to each pixel. One end of each of the vertical signal lines 1, 1a,... Is connected to the horizontal signal line 10 for the spatial light modulator through the sampling switches 9, 9a,..., And the gates of the sampling switches 9, 9a,. Connected to the horizontal shift register 8 of the light modulation element. Further, one ends of the drive lines 2, 2 a,... Are connected to the vertical shift register 7.

  In the light receiving element portion of each pixel, the anodes of the photodiodes 21, 21a,... Are grounded, and the cathodes are connected to one ends of the transfer switches 22, 22a,. The gates of the transfer switches 22, 22a,... Are connected to the corresponding horizontal readout lines, and the other ends are connected to one end of the reset switch. The reset switches 23, 23a,... Are for resetting the photodiode and the floating diffusion (FD) region electrically connected thereto to a predetermined potential, and a predetermined potential is applied to the other end. At the same time, the gate is connected to the horizontal reset line. Further, the other ends of the transfer switches 22, 22a,... Are also connected to the gates of amplification transistors 24, 24a,... For amplifying signal charges by the photodiodes 21, 21a,. A predetermined potential is applied to one end of each of the amplification transistors 24, 24a,..., And the other end is connected to a corresponding vertical signal line of the light receiving element via the selection switches 25, 25a,. The gate of the selection switch is connected to the corresponding horizontal selection line. One end of the vertical signal lines 26, 26a,... Of the light receiving element is connected to the horizontal signal line 33 of the light receiving element via the sampling switches 32, 32a,. The gates of the sampling switches 32, 32a,... Are connected to the horizontal shift register 31 of the light receiving element. .., Horizontal reset lines 28, 28a,..., And horizontal selection lines 29 and 29a for the light receiving elements are all connected to the vertical shift register 30 of the light receiving element.

  In FIG. 12, the pixels are arranged in 2 rows and 2 columns, but it goes without saying that the circuit of the modulation / light receiving element 108 in the optical information recording / reproducing apparatus of the present embodiment has, for example, a large number such as 1000 rows and 1000 columns. A pixel matrix configuration may also be used.

  The circuit operation of the modulation / light receiving element 108 of this embodiment will be described. First, the write mode will be described. The operation at the time of writing is the same as the active matrix operation in a general display device or the like.

  First, an ON signal is input from the vertical shift register 7 to the drive line 2, and the pixel switches 3 and 3a are turned on. In this state, the horizontal shift register 8 sequentially operates to transmit a signal from the horizontal signal line 10 to the vertical signal line 1. That is, first, the sampling switch 9 is turned on, the signal of the horizontal signal line 10 is written to the vertical signal line 1, and charges corresponding to the signal are accumulated in the storage capacitor 5 through the pixel switch 3. When the reflection type interferometric modulation element as shown in the first to third embodiments is used as the SLM, a potential difference between the reflection electrode (not shown) of the interference structure unit 4 and the common counter electrode 6 is applied. An electric field is generated during this time. By this electric field, the interference structure part 4 can be changed, and the reflectance with respect to incident light can be modulated to a desired value. Since the SLM in the holographic memory system only needs to have two gradations of white and black, the interference structure unit 4 is supplied with a voltage that provides the maximum reflectance or the minimum reflectance as the reflectance. Next, the sampling switch 9 is turned off and then the sampling switch 9a is turned on. This time, the signal of the horizontal signal line 10 is written to the vertical signal line 1a, and this signal is written to the holding capacitor 5a via the pixel switch 3a. In such a sequence, signals are sequentially written to the pixels in the horizontal direction (row direction).

  After all the lines have been written, the drive line 2 is turned off, and a signal is input to the drive line 2a to turn on the pixel switches 3b and 3c. Thereafter, as described above, signals are sequentially written to the pixels in the horizontal direction. After writing the voltages in all the rows, this operation is repeated again from the first row, and the voltages of the respective pixels are rewritten. After writing the signals to all the pixels in this way, if the light from the first light source 101 is incident on the modulation / light receiving element 108, the light is reflected as modulated light in each pixel, and the reflected light is Interference with the reference beam 109 is recorded on the recording medium 118.

  A pixel that modulates the reference light 109, that is, a pixel in the reference light region is set to have a constant reflectance. For example, a voltage that gives the maximum reflectivity is applied to the same structure as the pixel that receives the information light. Further, for example, a mirror structure may be simply used without forming an interference structure.

  Next, the reading mode will be described.

  Information recorded on the recording medium 118 is reproduced by the reference light 109, light intensity corresponding to “1” (white) or “0” (black) is incident on the light receiving pixel, and an amount of electric charge corresponding to the light intensity is applied to the photodiode. Are accumulated in 21, 21 a. An on signal is output from the vertical shift register 30 to the horizontal readout line 27 and the transfer switch 22 is turned on, whereby the charge stored in the photodiode changes the potential of the gate of the amplifying transistor 24. A voltage corresponding to the signal stored in the diode is output to the drain of the amplification transistor 24. When the selection switch 25 is turned on by the horizontal selection line 29 from the vertical shift register 30, the output of the amplification transistor 24 is transmitted to the vertical signal line 26. Information is sent from the vertical signal line 26 to the horizontal signal line 33 by sequentially operating the horizontal shift register 31 and turning on the sampling switch 32. After the sampling switch 32 is turned off, the sampling switch 32a in the next row is turned on, and a signal is sent in the same manner. After all the signals in one row are sent, the vertical shift register 30 moves to the next row, and the signals are sequentially read out in the same manner. After that, the signal recorded on the recording medium 118 may be reproduced based on the read signal.

  In addition, when the SLM using the reflection type optical interference light modulation element and the CMOS sensor as the light receiving element are stacked on the silicon substrate and integrated, or when the light receiving element is arranged at a position between the pixels, the light receiving element Is located below the above-described semi-permeable membrane of the interference structure. Therefore, immediately before the read mode is performed, the SLM transistors 3, 3a, 3b,... Of all the pixels that receive information are turned on once, and the interference structures 4, 4a, 4b,. It is necessary to keep in a state showing.

  In addition, although the case where the modulation / light-receiving element having the configuration in which the SLM and the light-receiving element are stacked in the vertical direction is used has been described, even when the SLM and the light-receiving element are arranged at different positions on the substrate surface in the same silicon substrate, The circuit configuration is the same as described above. In other words, in the present embodiment, a device in which the SLM and the CMOS sensor are arranged in the lateral direction on the surface of the silicon semiconductor substrate can be used as the modulation / light receiving element.

  Next, the structure of the modulation / light-receiving element in which the SLM using the reflection type optical interference light modulation element and the CMOS sensor as the light-receiving element in the present embodiment are vertically integrated, that is, is described. FIG. 13 shows a cross-sectional structure of the main part of such a modulation / light-receiving element. Here, a region for two pixels is shown. Although an example in which a CMOS sensor capable of high-speed reading is used as the light receiving element has been described, the type of the light receiving element is not particularly limited, and may be a CCD or other optical sensor.

  A photodiode 52 is formed on the surface of a single crystal silicon (Si) substrate 51, and a gate electrode 53 of a transfer switch of the CMOS sensor is provided. An interlayer insulating film 60 is provided so as to cover the entire surface, and a CMOS sensor wiring 54, an SLM wiring 55, and a light shielding film 56 are provided in the interlayer insulating film 60. A reflective electrode 57 is provided near the outermost surface of the interlayer insulating film 60. The wiring 54 is connected to the source / drain electrode of the transfer switch through a contact hole, and the wiring 55 is connected to the reflective electrode 57 through the contact hole. A columnar insulating film 61 is provided on the surface of the interlayer insulating film 60 and on the periphery of the reflective electrode 57, and the semi-transmissive film 58 is held by the insulating film 61. Is provided. A space (air gap) 62 is formed between the semi-transmissive film 58 and the reflective electrode 57. A protective film 59 is formed on the entire surface of the semipermeable membrane 58 that does not face the space 62. In this figure, a LOCOS oxide film for insulating between elements, other transistors and wirings of the CMOS sensor, and pixel switches and wirings of the SLM are omitted.

  In this modulation / light-receiving element, interference is caused between the reflective electrode 57 and the semi-transmissive film 58 with respect to incident light, and a distance (air gap) of a space (for example, air) 62 therebetween is changed. The reflectance and transmittance are changed. In this configuration, an SLM using a reflective optical interference light modulation element and a CMOS sensor as a light receiving element are vertically integrated. Therefore, since the transmission mode is also used when reading light incident on the CMOS sensor as the light receiving element, both mirrors (semi-transmissive film 68 and reflective electrode 57) need to be translucent. However, in the case of the horizontal arrangement, it is not necessary to use the transmission mode in the interference structure unit 4, and thus the reflective electrode 57 does not need to be translucent. When the reflective electrode 57 is not translucent, it is preferable to use a material having high reflectivity as the reflective electrode 57, for example, Al, AlSi, AlCu, Ti, Ta, W, Ag, Pt, Ru, Ni, Au. , TiN, or a metal film or a compound film of these metals can be used. However, the material of the reflective electrode is not limited to that shown here. The columnar insulating film 61 disposed between the reflective electrode 57 and the semi-transmissive film 58 is made of, for example, a silicon nitride film, and the protective film 59 of the semi-transmissive film 58 is made of, for example, a silicon oxide film. The pillar-shaped insulating film 61, the interlayer insulating film 60, and the protective film 59 can be used without any particular limitation as long as they are electrically insulating materials. You may comprise with the same material.

Next, the operation of the modulation / light receiving element as an interference structure will be described. First, for example, a ground potential of 0 V is applied to the semi-transmissive film 58 made of Ti. By the above-described active matrix operation, a voltage corresponding to the signal is applied to the reflective electrode 57, a potential difference is generated between the reflective electrode 57 and the semi-transmissive film 58, and the air gap is changed by the coulomb force generated thereby. . FIG. 14 shows the reflection when the air gap is 170 nm and 10 nm when the interference structure portion is composed of the semi-transmissive film 58 having a thickness of 5 nm and the reflective electrode 57 having a thickness of 15 nm. It is a graph showing the wavelength change of a rate. As the protective film 59, SiO ₂ having a thickness of 10 nm is used. As shown in FIG. 14, in light having a wavelength of 550 nm, the reflectance when the air gap is 170 nm is 52.5%, and the reflectance when the air gap is 10 nm is 1.2%. It can be seen that when the air gap is changed from 10 nm to 170 nm by the voltage of the signal applied to the reflective electrode 57, the reflectivity changes greatly accordingly. This interference action can be designed according to the wavelength, the semi-transmissive film material, and the air gap. Therefore, it is important to take the necessary structure as the interference structure in view of characteristics such as physical strength and contrast ratio. is there.

  In the readout mode, it is necessary to keep the light transmittance constant and the transmittance constant in at least the pixels on which information light is incident. Accordingly, FIG. 15 shows a change in wavelength in transmittance when the air gap is set to 10 nm in this modulation / light receiving element. In this case, the transmittance is relatively low at 23.0%, but it is important that the transmittance is constant, and the absolute value of the transmittance is not so important. By keeping the transmittance constant, it is possible to determine the intensity of the reproduction light with a CMOS sensor and identify whether it is a white pixel or a black pixel.

  In this embodiment, since the SLM and the CMOS sensor as the light receiving element are arranged on the same chip, a complicated mechanism for aligning the two and an expensive relay lens system can be eliminated, and the optical System cost reduction and downsizing can be achieved.

  According to the present embodiment, a spatial light modulation element as an element for writing information in an optical information recording apparatus or an optical information recording / reproducing apparatus that records information by recording interference fringes caused by interference between information light and reference light Is used. The spatial light modulator has a plurality of reflection type optical interference modulators that exist in a line or matrix form. Each interferometric modulation element includes a reflective electrode that reflects light from the light source, and a semi-transmissive electrode that is disposed on the reflective electrode with a space interposed therebetween. In each interferometric modulation element, the intensity of the reflected light can be modulated by controlling the potential of the reflective electrode and changing the distance between the reflective electrode and the semi-transmissive electrode. The spatial light modulator having the reflection type light modulator having such a configuration has a simple structure that can be finely formed. Therefore, according to this embodiment, the optical information recording apparatus or the optical information recording / reproducing apparatus can be configured at low cost.

  INDUSTRIAL APPLICABILITY The present invention is applicable to an optical information recording apparatus and an optical information recording / reproducing apparatus capable of recording high density and large capacity information by recording light interference fringes on a recording medium.

1 is an equivalent circuit diagram of a spatial light modulation element used in an optical information recording / reproducing apparatus according to a first embodiment of the present invention. It is sectional drawing which shows the structure of the pixel part (interference structure part) of a spatial light modulation element. It is a graph which shows the wavelength-reflectance characteristic of an interference structure part. (A), (b) is the top view and perspective view of a reflection type interferometric modulation element, respectively. It is a top view of the semiconductor chip which has a spatial light modulation element using a reflection type interferometric modulation element. It is a top view of the reflection type interferometric modulation element in the second embodiment. It is a graph which shows the wavelength-reflectance characteristic of the reflective interference element shown in FIG. It is a top view of the reflection type interferometric modulation element in the third embodiment. It is a figure explaining the optical system of the optical information recording / reproducing apparatus of the 4th Embodiment of this invention, Comprising: It is a figure which shows from a light source at the time of recording to a modulation / light receiving element. It is a figure explaining the optical system of the optical information recording / reproducing apparatus of 4th Embodiment, Comprising: It is a figure which shows from a modulation / light receiving element to a recording medium at the time of recording. It is a figure explaining the optical system of the optical information recording / reproducing apparatus of 4th Embodiment, Comprising: It is a figure which shows the time of reproduction | regeneration. It is an equivalent circuit diagram explaining a modulation / light receiving element. It is sectional drawing of the principal part of a modulation / light receiving element. It is a graph which shows the wavelength-reflectance characteristic of a modulation / light receiving element. It is a graph which shows the wavelength-transmittance characteristic of a modulation / light receiving element. It is a figure which shows the outline of the conventional optical information recording device apparatus using a holographic memory.

Explanation of symbols

1,26,301,302 Vertical signal line 2,315,316 Drive line (scanning line)
3, 303 to 306 Switching transistor 4, 307 to 310 Interference structure portion 5, 311 to 314 Retention capacitance 6,322 Common counter electrode 7, 30, 318 Vertical shift register 8, 31, 317 Horizontal shift register 9, 32, 320, 321 Sampling switch 10, 33, 319 Horizontal signal line 21, 52 Photodiode 22 Transfer switch 23 Reset switch 24 Amplifying transistor 25 Selection switch 27 Horizontal readout line 28 Horizontal reset line 29 Horizontal selection line 42, 47, 58, 331 Transflective film 45 Reference light region 46 Information light region 51 Silicon (Si) substrate 53 Gate electrode 54 and 55 Wiring 56 and 335 Light shielding film 57 and 330 Reflective electrode 59 and 333 Protective film 60 Interlayer insulating film 61 and 332 Insulating film 62 Space 101 and 201 First The light source (green laser)
102, 202 Collimator 103 Mask element 104, 207 Polarizing beam splitter (PBS)
105,212 1/4 wave plate (QWP)
106, 107, 111, 113, 208, 210 Relay lens 108 Modulation / light receiving element 109, 205 Reference light 110, 206 Information light 112, 115, 122, 203, 209, 213, 223 Mirror 114, 211 Dichroic beam splitter (DBS) )
116, 214 Objective lenses 117, 215 Spindle motor 118, 216 Recording medium 119, 220 Second light source (red laser)
120,221 Beam splitter (BS)
121, 218, 222 Lens 123, 224 Photodetector 334 Base wiring layer 336 Plug 204 Spatial light modulator (SLM)
217 Aperture 219 Light-receiving element

Claims (10)

Optical information recording / reproduction in which information is recorded on the recording medium by forming interference fringes generated by the interference between the information light and the reference light on the recording medium, and the interference fringes are read and reproduced by applying the reference light to the recording medium. In the device
A light source;
It has a plurality of modulation elements whose reflected light intensity changes according to the modulation signal, and modulates at least a part of a light beam emitted from the light source to form the information light, and the reference light without modulating at least a part thereof a spatial light modulator to a,
An optical system for causing the reference light and the information light to interfere at a predetermined depth of the recording medium;
An optical system that applies the reference light from the light source to a predetermined depth of the recording medium, reproduces the information light from the interference fringes, and extracts the reproduced information light;
A light receiving element;
An optical system for introducing the extracted information light into the light receiving element;
Have
The modulation element is a reflective electrode that reflects light from the light source, and the semi-transmissive film exhibiting semi-transparent to light from the disposed through a space from the reflection electrode on the light source side before Symbol source A columnar insulating film provided only at a position corresponding to a peripheral edge of the reflective electrode in order to maintain a distance between the reflective electrode and the semitransmissive film, and the reflective electrode and the semitransmissive film reflectance of light from the light source is changed by controlling the distance between,
The spatial light modulation element and the light receiving element are integrally formed on the same substrate, and the spatial light modulation element is disposed on a surface of the substrate on which the light receiving element is formed. Optical information recording / reproducing device. The optical information recording / reproducing apparatus according to claim 1, wherein an interval between the reflective electrode and the semi-transmissive film is controlled for each of the modulation elements. 3. A device for applying a voltage between the reflective electrode and the semi-transmissive film, wherein a distance between the reflective electrode and the semi-transmissive film changes according to the voltage. 2. An optical information recording / reproducing apparatus according to 1. The optical information according to claim 3, wherein the transflective film is a common electrode provided in common to a plurality of modulation elements, and the voltage is applied to the reflection electrode for each modulation element. Recording / playback device. 5. The optical information recording / reproducing apparatus according to claim 1, wherein the modulation element modulates light from the light source into binary information. 6. The substrate, the optical information recording and reproducing apparatus according to any one of claims 1 to 5, characterized in that a substrate of single crystal silicon. The optical information recording / reproducing apparatus according to claim 1, wherein the semi-transmissive film is made of a material containing Ti. 8. The optical information recording / reproducing apparatus according to claim 1, wherein the semi-transmissive film connects each pixel with a narrower structure than a pixel region. 9. 9. The optical information recording / reproducing apparatus according to claim 8, wherein the thin structure of the semi-transmissive film is provided at a plurality of locations. 10. The reference light according to claim 1, wherein the reference light is reflected from the spatial light modulation element by an element that is on the same plane as the modulation element and has the same structure as the modulation element. 11. Optical information recording / reproducing apparatus.