JP2009175385A - Terrace type thin-plate substrate, making method of terrace type thin-plate substrate, pseudo phase matching second harmonic generating device, high-density recording medium, laser, optical modulator, and polarization inverting method of terrace type thin-plate substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a thin-plate substrate whose both surfaces are usable in a short time at low cost. <P>SOLUTION: The terrace type thin-plate substrate 1 which has a non-processed section 2 having a first main surface 11 and a second main surface 12 and a cut section 3 having the first main surface 11 and a cut surface 13 by cutting a surface 31 having a surface perpendicular to a self-polarization direction as the first main surface 11 by using a dicer, is manufactured. The substrate 13 is installed so as to have the first main surface 11 in parallel to a diameter direction of an extremely thin peripheral cutting edge 32 of the dicer, which is pressed against a side surface of the substrate 31 to cut off a portion of the substrate 31. As the cutting-off operation, an operation to cut off a surface-layer portion including the second main surface 12 first by pressing the extremely thin peripheral cutting edge 32 against a side surface end on the side of the second main surface 12 and then to cut off a surface-layer portion including a cut surface L<SB>1</SB>formed as a result by pressing the extremely thin peripheral cutting edge 32 against a side surface end on the side of the cut surface L<SB>1</SB>is repeatedly performed to shorten the distance between the first main surface 11 and cut surface 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a terrace-like thin plate substrate, a method for producing a terrace-like thin plate substrate, a quasi phase matching second harmonic generation device, a high-density recording medium, a laser, an optical modulator, and a method for inverting the polarization of the terrace-like thin plate substrate, The present invention relates to a method for manufacturing a terrace-shaped thin plate substrate using a dicing saw or a dicer, and a nonlinear optical device using the terrace-shaped thin plate substrate.

  Quasi-phase-matching (QPM) second harmonic generation (SHG) devices using ferroelectric nonlinear optical crystal materials are most suitable for improving the efficiency of wavelength conversion devices. Because it is necessary to realize a high-efficiency blue coherent light source in a wide range of fields such as memory, display, laser printer, optical measurement, etc., research is being conducted energetically at major internal and external research institutions (for example, patents) Reference 1 and 2). In addition, according to the QPM-SHG device, it is possible to output not only blue but also many other colors (from ultraviolet light to infrared light to THz). Here, blue is taken as an example for explanation. Continue.

  As shown in FIG. 23, the QPM-SHG device forms an optical waveguide 112 by forming a periodic polarization inversion structure composed of a polarization inversion 111 having a period of coherent length (lc) formed in the nonlinear optical crystal 100. , The incident light (pump light) 113 is converted to create outgoing light 114 as a blue light source. In order to reduce the wavelength, size, and performance of QPM-SHG devices, it is important to make the domain-inverted structure finer. For this purpose, it is important to reduce the thickness of the ferroelectric nonlinear optical crystal substrate. It has become. In the high-density recording media and photonic crystals described in the third and fourth embodiments of the present invention, which will be described later, it is an important issue to reduce the domain size of domain inversion. Thinning a body nonlinear optical crystal substrate is an important issue.

  For example, the coherent length of a QPM-SHG device is 0.7 μm (1.4 μm cycle) for short (for ultraviolet light), 0.4 μmφ for photonic crystals, and ˜3 nmφ for high-density recording media, respectively. is needed.

So far, in ferroelectric optical crystals such as LiNbO ₃ (hereinafter abbreviated as “LN”) and LiTaO ₃ (hereinafter abbreviated as “LT”), the liquid phase epitaxy (LPE) method (Non-patent Document 1). And thin film growth methods such as a sol-gel method (see Non-Patent Document 2), and a thin plate processing method (see Non-Patent Document 3) in which crystals are polished in a state of being attached to a metal plate.
JP 2005-234147 A JP 2006-106804 A S. Kondo, S .; Miyazawa, S .; Fusimi and K.K. Sugii, Appl. Phys. Lett. , 26, 489 (1975). S. Hirano and K.M. Kato, Journal of Non-Crystalline Solids 100, 538 (1988) K. Terabbe, M .; Nakamura, S .; Takekawa and K.K. Kitamura, Appl. Phys. Lett. , 82, 433 (2003).

  However, in any of the above methods, it takes a lot of time, process and cost to produce a thin plate-like substrate.

  In addition, since a metal plate or the like is attached to the back surface of the manufactured thin plate substrate, it is impossible to observe whether or not the domain-inverted structure is uniformly formed over the front and back surfaces of the thin plate substrate. There was a restriction on the degree of freedom that only one side of the thin plate substrate used could be used.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to produce a terrace-like thin plate substrate that can be used on both sides of the produced substrate in a short time and at a low cost. It is to provide a terraced thin plate substrate, a fine domain-inverted structure using the terraced thin plate substrate, and a method of manufacturing the same.

  In order to achieve the above object, a first feature of the present invention is a ferroelectric optical crystal substrate having a first main surface as a plane perpendicular to the direction of spontaneous polarization, which is used to fabricate a device having a domain-inverted structure. The substrate includes a non-processed portion having a first main surface and a second main surface opposite to the first main surface, and a first optical surface disposed on the outer periphery of the ferroelectric optical crystal substrate. A cutting part having a main surface of 1 and a cutting surface facing the first main surface is provided. The distance between the first main surface and the cutting surface is shorter than the distance between the first main surface and the second main surface.

  Both sides of the first main surface and the cutting surface of the cutting portion can be observed with a microscope or the like, so that both surfaces of the substrate can be used and the degree of freedom is improved. Therefore, by using the terrace-shaped thin plate substrate, it is possible to easily form a fine polarization inversion structure in the cut portion using the first main surface and the cut surface perpendicular to the spontaneous polarization direction. Further, since the terrace-shaped thin plate substrate includes a non-processed portion continuous with the cutting processing portion, the substrate can be easily handled.

  It is desirable that the cutting surface bends toward the second main surface and intersects the second main surface at the boundary portion between the cutting portion and the non-working portion. A sufficient mechanical strength of the machined portion can be ensured by curving the cutting surface and intersecting the second main surface.

  The second feature of the present invention is that a surface perpendicular to the direction of spontaneous polarization is formed by using a device that scrapes a part of a workpiece with an ultra-thin outer peripheral blade attached to the tip of a spindle that rotates at high speed. A ferroelectric optical crystal substrate having a first main surface and a second main surface opposite to the first main surface by cutting the ferroelectric optical crystal substrate as a surface, and the ferroelectric optical crystal substrate Is a method for producing a terrace-shaped thin plate substrate having a cutting portion having a first main surface and a cutting surface facing the first main surface, the method comprising: A first step of installing a ferroelectric optical crystal substrate on the apparatus so that the first main surface is parallel to the radial direction of the blade, and the first main surface and the first main surface; Press the ultra-thin outer peripheral edge on the side of the ferroelectric optical crystal substrate that connects the opposing second main surface. And a second step of etching a portion of the ferroelectric optical crystal substrate against. In the second step, first, an ultra-thin outer peripheral blade is pressed against the side end portion on the second main surface side to scrape off the surface layer portion including the second main surface, and the cutting surface side formed thereby is cut. By repeatedly carrying out an operation of pressing the ultra-thin outer peripheral blade against the side surface end portion and scraping off the surface layer portion including the cutting surface, the cutting portion that reduces the distance between the first main surface and the cutting surface is thinned.

  In the second feature of the present invention, the work of removing the surface layer portion including the cutting surface may be performed in a plurality of times. Alternatively, an operation of scraping a part of the ferroelectric optical crystal substrate by pressing an ultra-thin outer peripheral blade near the middle between the first main surface and the second main surface is performed a plurality of times (for example, twice), and thereafter By cutting a portion of the ferroelectric optical crystal substrate by pressing the ultra-thin outer peripheral blade against the second main surface so that the second main surface is substantially perpendicular to the radial direction of the thin outer peripheral blade, A processed part may be formed.

  A third feature of the present invention is a quasi-phase matching second harmonic generation device using the above-described terrace-shaped thin plate substrate, wherein an optical waveguide formed in a cutting portion, and spontaneous polarization along the optical waveguide A quasi-phase comprising a polarization reversal layer in which the direction is reversed and a periodic polarization reversal structure in which a non-polarization reversal layer in which the spontaneous polarization direction of the terrace-shaped thin plate substrate is not reversed is formed alternately In the matched second harmonic generation device, the lengths of the domain-inverted layer and the non-domain-inverted layer along the optical waveguide are each coherent.

  In the third aspect of the present invention, the optical waveguide is preferably formed from the first main surface to the cutting surface. Both the + Z direction and −Z direction boundary surfaces of the optical waveguide are in contact with air, and the density of propagating light is high, so that the conversion efficiency of the quasi phase matching second harmonic generation device is high.

  A fourth feature of the present invention is a polarization reversal method for forming a minute polarization reversal region on a terrace-shaped thin plate substrate produced by the above-described method for producing a terrace-shaped thin plate substrate. A third step of forming a conductive film on the cutting surface, a fourth step of bringing the tip of the metal probe closer to the first main surface of the cutting portion, and a predetermined voltage between the conductive film and the metal probe. And a fifth step of reversing the direction of spontaneous polarization of the ferroelectric optical crystal in the region where the tip of the metal probe is brought close to.

  Since the thickness of the cutting portion having the first main surface and the cutting surface perpendicular to the spontaneous polarization direction is extremely thin, a minute polarization inversion structure can be easily formed by a minute applied voltage according to the scaling law. be able to.

  In the fifth step, it is desirable to scan the metal probe on the first main surface of the cutting portion with a predetermined voltage applied. By scanning the metal probe on the first main surface of the cutting portion, a domain-inverted structure according to the scanning pattern can be formed. Therefore, a fine periodic polarization inversion structure can be easily formed by scanning the metal probe in a line at a predetermined interval.

  According to the present invention, a method for producing a terrace-like thin plate substrate that can use both sides of the produced substrate in a short time and at low cost, a terrace-like thin plate substrate produced by this method, and this terrace-like thin plate substrate are used. A fine domain-inverted structure can be provided.

Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are denoted by the same reference numerals.
(First embodiment)
With reference to FIG. 1, the whole structure of the terrace-shaped thin board | substrate 1 concerning the 1st Embodiment of this invention is demonstrated. The terrace-shaped thin plate substrate 1 is a substrate made of a ferroelectric optical crystal having a surface perpendicular to the direction of spontaneous polarization as a front surface or a back surface, and for producing a device having a polarization inversion structure such as a QPM-SHG device. It is the board | substrate used. The terrace-shaped thin plate substrate 1 has a flat plate shape, and an ultra-thin terrace-shaped cutting process in which a device having a domain-inverted structure is formed on one side (here, one long side) of the outer periphery of the substrate 1. The part 3 is formed, and the other part is composed of a non-processed part 2 having a thickness (about 400 to 500 μm) of a normal ferroelectric optical crystal substrate. Further, a corner dropping portion 4 is formed at one corner of the non-working portion 2 where the cutting portion 3 is not formed in order to identify the crystal orientation of the ferroelectric optical crystal.

In the embodiment of the present invention, the “ferroelectric optical crystal” includes LiNbO ₃ (lithium niobate: hereinafter abbreviated as “LN”) crystal or LiTaO ₃ (lithium tantalate: Hereinafter, abbreviated as “LT”.) Crystals are included. The LN crystal and the LT crystal are uniaxial crystals belonging to the trigonal system and have a large nonlinear optical constant. Therefore, for example, for the production of a QPM-SHG device that generates a second harmonic using a phenomenon due to the nonlinear optical effect. It is used. In addition, the nonlinear optical effect includes many device groups such as SFG (optical sum frequency generation), DFS (optical difference frequency generation), and OPO (optical parametric oscillation). Further, LN crystal and LT crystals, the polarization direction is a 180 ° domain structure showing only two of + _{P S} and -P _S in C-axis (Z-axis in FIG. 1) direction, the direction of spontaneous polarization By inverting, it becomes possible to form a periodic polarization inversion structure. A QPM-SHG device having a periodically poled structure will be described in a second embodiment.

  FIG. 2 is an enlarged perspective view of a part of the cutting portion 3 surrounded by a dotted line 5 in FIG. In FIG. 2, in order to explain the shape (terrace shape) of the non-processed part 2, for convenience, a state in which a part of the cutting part 3 is cut along a plane perpendicular to the X direction is shown. The non-processed part 2 provided with the terrace shape shown in FIG. 1 is continuously formed over one side of the outer periphery of the terrace-like thin plate substrate 1 shown in FIG.

As shown in FIG. 2, terraced thin substrate 1 according to a first embodiment of the present invention is a ferroelectric optical crystal substrate for a plane perpendicular to the first major surface 11 in the direction of spontaneous polarization P _S The non-processed part 2 having the first main surface 11 and the second main surface 12 facing the first main surface 11, and the first main surface 11 and the first main surface 11 are opposed to each other. And a cutting portion 3 having a cutting surface 13. The distance between first main surface 11 and cutting surface 13 is shorter than the distance between first main surface 11 and second main surface 12. In other words, the thickness of the cutting part 3 is thinner than the thickness of the non-working part 2. The cutting surface 13 is formed substantially parallel to the first main surface 11, and the second main surface 12 is also formed substantially parallel to the first main surface 11. The second main surface 12 and the cut surface 13 expressed in the spontaneous polarization direction P _S (+ Z direction) are referred to as “+ C plane” and expressed in the direction opposite to the spontaneous polarization direction P _S (−Z direction). The first main surface 11 is referred to as “−C plane”.

  At the boundary portion between the non-machined portion 2 and the machined portion 3, the cutting surface 13 is curved toward the second main surface 12 and intersects the second main surface substantially perpendicularly. As described above, the second main surface 12 and the cutting surface 13 are connected via the step surface 14 at the boundary portion between the non-processing portion 2 and the cutting processing portion 3, and connected to the cutting surface 13 of the step surface 14. A curved portion 15 made of a columnar curved surface with the X direction as an axis is formed in the portion.

  Next, with reference to FIGS. 3 to 10, a method for manufacturing the terrace-shaped thin plate substrate 1 shown in FIGS. 1 and 2 will be described. FIG. 3 is a flowchart showing a procedure of a method for manufacturing the terrace-shaped thin plate substrate 1 shown in FIGS. 1 and 2. FIGS. 4A and 4B are diagrams for explaining step S01 (crystal cutting) in FIG. FIG. 5 is a diagram illustrating step S03 (with electrodes) in FIG. FIG. 6 is a diagram for explaining step S04 (surface protection) in FIG. FIG. 7 is a diagram for explaining step S05 (mount) in FIG. FIG. 8 is a diagram for explaining step S07 (chipping removal) in FIG. FIG. 9 is a diagram for explaining step S08 (terrace processing) in FIG. FIG. 10 is a diagram for explaining step S09 (dimension measurement) in FIG.

  (A) First, in step S01, as shown in FIG. 4A, an apparatus (for example, a dicing saw or a dicer) that cuts a workpiece with an ultra-thin outer peripheral blade attached to the tip of a spindle that rotates at high speed. 4 is cut along a plurality of cut lines 22 that are parallel to the Y direction and equally spaced and a plurality of cut lines 23 that are parallel and equally spaced in the X direction. A strip-shaped substrate 31 as shown in FIG. Then, one corner portion of the strip-shaped substrate 31 is scraped to form the corner dropping portion 4. Thereafter, the strip-shaped substrate 31 is removed from the base of the dicer, and water washing, ultrasonic washing, methanol washing, and acetone washing are performed and dried.

  (B) Proceeding to step S02, a solution obtained by diluting a neutral detergent about 50 times is soaked in a cotton swab in a clean room, and the front and back surfaces (first and second main surfaces) of the strip-shaped substrate 31 are 100 with the cotton swab. Rub about once. Then, it is washed with ethanol and acetone and dried.

  (C) Proceeding to step S03, as shown in FIG. 5, a strip with the + C surface (second main surface) 12 on which the gold thin film is to be formed on the pedestal 24 in the sputtering apparatus (vacuum chamber) facing upward. The substrate 31 is installed, and gold (Au) is deposited on the + C surface 12 of the strip substrate 31 by sputtering. As an example of sputtering conditions, when a gold target having a diameter of 50 mm is used, the degree of vacuum may be 0.1 Torr, the current value may be 3 mA, and the sputtering time may be 10 minutes.

  (D) Proceeding to step S04, a resist is applied to the −C surface (first main surface) 11 of the strip-shaped substrate 31. Specifically, first, the resist is returned to room temperature, and the resist is sucked by the syringe 25 of FIG. A filter 26 is attached to the tip of the syringe 25. The strip-shaped substrate 31 is adsorbed on the spinner 27 with the -C surface 11 facing up. A resist is dropped on the −C surface 11 of the strip substrate 31. The spinner 27 is rotated to form a resist layer having a uniform thickness on the -C surface 11. Then, the resist layer on the −C surface 11 is solidified by baking in an oven.

  (E) Proceeding to step S05, as shown in FIG. 7, the jigs 30a and 30b are arranged on the flat surface of the soda glass plate 29, and the strip-shaped substrate 31 is sandwiched between the jigs 30a and 30b. The base 29, the jigs 30a and 30b, and the strip-shaped substrate 31 are fixed with wax. The strip-shaped substrate 31 has its long side end surface facing upward, and the −C plane (first main surface) 11 of the strip-shaped substrate 31 is perpendicular to the flat surface of the soda glass plate 29. Fixed. The specific procedure is as follows. First, filter paper is laid on the hot plate 28, and a flat soda glass plate 29 is placed on the filter paper. The hot plate 28 is heated to about 80 to 100 ° C., and the shift wax is melted on the soda glass plate 29. The jigs 30a and 30b made of flat glass are placed on the soda glass plate 29, and the strip-shaped substrate 31 is sandwiched between the jigs 30a and 30b with the end surface on the long side of the strip-shaped substrate 31 facing up. The jigs 30a and 30b and the strip-shaped substrate 31 are lightly pressed from above, and then the temperature of the hot plate 28 is lowered to solidify the shift wax.

  (F) Proceeding to step S06, alignment adjustment of an apparatus (for example, a dicing saw or a dicer) that scrapes off a part of the workpiece with an ultra-thin outer peripheral blade attached to the tip of a spindle that rotates at high speed is performed. Specifically, the dressing of the ultra-thin outer peripheral blade (blade) is performed, and the height of the ultra-thin outer peripheral blade is measured. Then, an Si substrate or the like is placed on the Dicer suction table, and the hairline is aligned by actually cutting and matching the cutline with the hairline.

  (G) Thereafter, the soda glass plate 29, the jigs 30a and 30b and the strip-shaped substrate 31 shown in FIG. 7 are placed on the adsorption table of the dicer. The ultrathin outer peripheral blade of the dicer is disposed so that the radial direction of the ultrathin outer peripheral blade is perpendicular to the flat surface of the suction table. Therefore, by placing the soda glass plate 29, the jigs 30a, 30b and the strip-shaped substrate 31 shown in FIG. 7 on the suction table, as shown in FIG. Thus, the strip-shaped substrate 31 can be placed on the suction table of the dicer so that the -C surface (first main surface) 11 of the strip-shaped substrate 31 is parallel.

  (H) Proceeding to step S07, as shown in FIG. 8, the ultrathin outer peripheral edge 32 is pressed against the side surface 34 of the strip-shaped substrate 31 that connects the -C surface 11 and the + C surface 12, and the strip-shaped substrate 31 The chipping 33 formed on the side surface 34 of the strip-shaped substrate 31 is removed by scraping off the surface layer portion including the side surface 34. Specifically, the side surface of the strip-shaped substrate 31 is cut to a depth of about 30 μm from the + C surface 12 side, and the ultrathin outer peripheral blade 32 is moved to the −C surface 11 side by the thickness or less (for example, about 90 μm). The side surface of the strip-shaped substrate 31 is cut again to a depth of about 30 μm. By repeating this, the entire surface layer portion of the side surface 34 on which the chipping 33 is formed is scraped off.

  (I) Proceeding to step S08, as shown in FIG. 9, the ultrathin outer peripheral edge 32 is pressed against the side surface of the strip-shaped substrate 31, and a part of the strip-shaped substrate 31 is scraped off, thereby removing -C of the strip-shaped substrate 31. Only the surface layer portion of the surface 11 is left, and the ultrathin cutting portion 3 is formed on the non-working portion 2 by removing the side surface portion of the other strip-shaped substrate 31. This operation is called “terrace processing”.

In this terrace processing, first, an ultrathin outer peripheral blade 32 is pressed against the end of the side surface 34 on the + C surface 12 side, and the surface layer portion including the + C surface 12 is scraped off. By performing this “cutting operation”, a cutting surface L ₁ parallel to the radial direction of the ultrathin outer peripheral edge 32 is formed as shown in FIG. Then, the ultra-thin outer peripheral blade 32 is moved to the −C surface 11 side by the distance d ₁ or less, for example, a distance d _1, and the ultra-thin outer peripheral blade 32 is pressed against the end of the side surface 34 on the cutting surface L ₁ side. _The surface layer part including ₁ is scraped off. Then, move the ultrathin peripheral cutting edge 32 at a distance d ₂ by -C face 11 side, the surface layer portion including the cutting surface L ₂ by pressing the ultra-thin outer peripheral edge 32 on the sides 34 end of the cutting surface L ₂ side Scrape off. By repeatedly performing the same operation (cutting operation), the distance between the first main surface 11 and the cutting surface 13 is shortened, and the cutting portion 3 is thinned.

For example, in the case of the strip-shaped substrate 31 having a thickness of 500 μm, if the distances d _{1 to} d ₅ are 90 μm, the cutting operation is performed 5 to 6 times. Further, each cutting operation may be performed as “multi-stage cutting” divided into about three times (w _{1 to} w ₃ ). If the depth of cut once (w ₁ to w ₃ ) is about 35 μm, the cut portion 3 having a width W of about 100 μm can be produced. By repeating this operation, it is possible to manufacture up to about 700 μm.

  (N) Proceeding to step S09, as shown in FIG. 10, the width W and the thickness d of the terrace (cutting portion 3) are measured using a laser microscope. If the measured terrace is insufficiently thin (NO in step S10), the process returns to step S08 and the terrace processing is performed again. If the measured terrace thickness is sufficiently thin (YES in step S10), the process proceeds to step S11, and the soda glass plate 29, jigs 30a, 30b and the strip-shaped substrate 31 are removed from the dicer suction stage, and the soda glass plate 29 is removed. The jigs 30a and 30b and the strip-shaped substrate 31 are again heated on the hot plate (about 80 to 100 ° C.), and the strip-shaped substrate 31 is removed. Through the above procedure, the terrace-shaped thin plate substrate 1 shown in FIG. 1 can be produced from the strip-shaped substrate 31 shown in FIG.

  The curved portion 15 shown in FIG. 2 is formed by the cross-sectional shape of the ultrathin outer peripheral blade 32. Therefore, the shape of the curved portion 15 can be freely changed depending on how to dress the ultra-thin outer peripheral blade (blade) in step S06.

As described above, the terrace-shaped thin plate substrate according to the first embodiment is a strong substrate having a first principal surface that is a plane perpendicular to the direction of spontaneous polarization used for manufacturing a device having a domain-inverted structure. A non-processed portion 2 having a first main surface 11 and a second main surface 12 opposite to the first main surface 11, which is a dielectric optical crystal substrate, and disposed on the outer periphery of the ferroelectric optical crystal substrate The cutting part 3 having the first main surface 11 and the cutting surface 13 is provided. The distance between first main surface 11 and cutting surface 13 is shorter than the distance between first main surface 11 and second main surface 12. Therefore, both the first main surface 11 and the cutting surface 13 of the cutting part 3 can be observed with a microscope or the like, so that the degree of freedom is improved. Thus, by using the terraced thin substrate 1 according to the first embodiment, the spontaneous polarization directions P _S finely cutting unit 3 using the first major surface 11 and the cutting plane 13 perpendicular to the polarization reversal The structure can be easily formed. Further, since the terrace-shaped thin plate substrate 1 includes the non-processed portion 2 continuously to the cutting processing portion 3, the substrate 1 can be easily handled.

  Further, the cutting surface 13 is curved toward the second main surface 12 and intersects the second main surface 12 at the boundary portion between the cutting portion 3 and the non-processing portion 2. A sufficient mechanical strength of the cutting portion 3 can be ensured by curving the cutting surface 13 and intersecting the second main surface 12.

  Further, in the method for manufacturing the terrace-shaped thin plate substrate according to the first embodiment of the present invention, the ultrathin outer peripheral blade 32 is pressed against the end of the side surface 34 on the second main surface 12 side, and the second main surface 12 is pressed. The surface layer portion including the cutting surface L is scraped off, and the operation of scraping the surface layer portion including the cutting surface L by pressing the ultrathin outer peripheral edge 32 against the end of the side surface 34 on the side of the cutting surface L formed thereby is repeatedly performed. The distance between the main surface 11 and the cutting surface 13 is shortened to reduce the thickness of the cutting portion 3. Thereby, the terrace-shaped thin plate | board board | substrate which can utilize both surfaces of the produced cutting process part 3 can be produced at low cost in a short time.

Further, by performing the cutting operation for cutting off the surface layer portion including the cutting surface L as a “multi-stage cutting” divided into multiple times (w _{1 to} w ₃ ), it is further possible that the cutting part 3 is damaged during the production. Therefore, the terrace-shaped thin plate substrate can be manufactured in a shorter time and at a lower cost.
(Comparative example)
As a technique related to “terrace processing” in the first embodiment (FIG. 3), there is a ridge processing technique. ECR-RIE is conventionally known as a ridge processing technique (Everybody: IEICE Transactions Vol. J77-CI, No. 5, 194 (1994)). However, ECR-RIE has a disadvantage that the ridge angle becomes shallow because the etching rate for the LN crystal and the LT crystal is slow. Since the ridge processing can be performed using a dicing saw or dicer, here, “terrace processing” using a dicing saw or dicer is compared with “ridge processing”.

  11A is a cross-sectional view showing a ridge processing method using a dicer, and FIG. 11B shows a state of a thin plate (ridge) portion of a substrate manufactured by the ridge processing method of FIG. 11A. It is a perspective view. FIG.11 (c) is sectional drawing which shows the terrace process in the 1st Embodiment of this invention.

  As shown in FIG. 11A, the −C surface of the LN crystal substrate 37 is fixed by vacuum suction onto a stage 36 made of stainless steel. One groove 40a that is a ridge side surface is cut perpendicularly to the + C plane 12 of the LN crystal substrate 37, and then the next groove 40b is cut by moving the blade at a constant interval corresponding to the ridge width. A ridge 38 shown in FIG. 11B is formed between the groove 40a and the groove 40b. The ridge width can be adjusted by adjusting the moving width of the blade. The amount of movement of the blade depends on the device, and there is a device that can feed 0.1 μm, but 1 μm feed is the minimum dimension in this experimental device. For example, the ridge width can be in units of 1 μm. The depth of the groove is obtained by subtracting the uncut amount from the thickness of the substrate 37, and can be controlled between 0 and 100 μm. Note that the + C plane 12 and the −C plane of the LN crystal substrate 37 may be exchanged.

As described above, in the ridge processing method, a convex portion (ridge) is formed by forming a groove perpendicular to the + C plane 12 or the −C plane of the LN crystal substrate 37, whereas FIG. As shown in (c), in the terrace processing method according to the first embodiment of the present invention, the + C plane 12 and the −C plane 11 of the LN crystal substrate 37 are arranged in parallel to the radial direction of the blade. The difference is that the cutting operation is performed by pressing the blade against the side surface of the substrate connecting the + C surface 12 and the −C surface 11.
(Second Embodiment)
In the second embodiment, a minute polarization inversion structure formed on the terrace-shaped thin plate substrate 1 manufactured by the method for manufacturing the terrace-shaped thin plate substrate shown in the first embodiment and a method for manufacturing the same will be described.

FIG. 12 is a perspective view showing a QPM-SHG device formed in the cutting portion 3 of the terrace-shaped thin plate substrate 1 according to the second embodiment of the present invention. QPM-SHG device has a period in the direction of spontaneous polarization P _S periodically poled obtained by inverting the coherent length (lc) along the propagation axis (X-axis). The cutting unit 3, the optical waveguide 39 is formed along the propagation axis (X-axis) along the optical waveguide 39, and the polarization inversion layer 45a~45g spontaneous polarization direction P _S is reversed, the spontaneous polarization direction P _S is the non-domain inverted layer 41a~41g that remains of the spontaneous polarization direction of the terraced thin substrate 1 without being inverted (+ Z direction in FIG. 12) are formed alternately. The polarization inversion layers 45a to 45g and the non-polarization inversion layers 41a to 41g are alternately formed in a stripe shape, and the length along the optical waveguide 39 is a coherent length (lc). Since the optical waveguide 39 is formed from the −C surface 11 to the cutting surface 13, both the + Z direction and −Z direction boundary surfaces of the optical waveguide 39 are in contact with air. Thereby, since the optical waveguide 39 has a symmetric configuration in the + Z direction and the −Z direction, it is possible to suppress the phenomenon that light escapes (does not pass) from the inside of the optical waveguide 39, which is cut off. Conventionally, since the optical waveguide 39 is formed only in the surface layer portion including the −C plane 11, the + Z direction boundary surface of the optical waveguide 39 is in contact with the ferroelectric optical crystal, and the −Z direction of the optical waveguide 39 is in the −Z direction. Since the boundary surface was in contact with air and was not symmetrical, a cut-off occurred.

  By providing such a periodically poled structure, the propagation constant difference between the fundamental wave (angular frequency: ω) and the SH wave (angular frequency: 2ω) can be quasi-phase matched. When near-infrared light (fundamental wave) is incident on the optical waveguide 39 as the incident light 46, a second harmonic (SH wave) having a half-wavelength (2ω) of the fundamental wave is obtained as the outgoing light 47 due to a phenomenon due to the nonlinear optical effect. It is done.

  Next, a method for manufacturing the QPM-SHG device shown in FIG. 12 will be described with reference to FIGS. FIG. 13 is a flowchart showing a procedure of a manufacturing method of the QPM-SHG device shown in FIG. FIG. 14 is a diagram for explaining step S21 (mount) in FIG. FIG. 15A is a diagram illustrating step S22 (drawing) in FIG. 13, and FIG. 15B is a diagram illustrating an example of a drawing pattern in step S22 (drawing).

  (A) First, a gold (Au) thin film is formed from the cutting surface 13 of the terrace-shaped thin plate substrate 1 to the second main surface 12. Then, in step S21, as shown in FIG. 14, the terrace-shaped thin plate substrate 1 is placed on the atomic force microscope (AFM) stage 48 so that the -C plane (first main surface) 11 faces up. Fix it. Specifically, the terrace-shaped thin plate substrate 1 is fixed with dotite by positioning so as to be within the movable range of the AFM. At this time, since the dotite cannot be completely removed, care is taken so that the dotite does not adhere to the terrace portion (cutting portion 3). Then, it is sufficiently dried.

(B) Proceeding to step S22, a drawing pattern as shown in FIG. 15B is drawn on the first main surface 11 of the cutting portion 3 by using an AFM metal probe. Specifically, as shown in FIG. 15 (a), the tip of the metal probe is brought close to the first main surface 11 of the cutting portion 3, and a predetermined amount is provided between the conductive film 42 (gold thin film) and the metal probe. voltage is applied to the, in a microscopic region closer to the tip of the metal probe, to reverse the direction of spontaneous polarization P _S of the ferroelectric optical crystal. The domain-inverted region is uniformly formed from the −C surface 11 to the cutting surface 13 in a minute region where the tip of the metal probe is brought closer.

In order to manufacture the periodically poled structure shown in FIG. 12, a drawing pattern as shown in FIG. 15B may be drawn. A predetermined voltage is applied when the thick line 43 in FIG. 15B is drawn, and a predetermined voltage is not applied when the thin line 44 is drawn. When the cut portion 3 is made of an LN crystal having a thickness of 6 μm, the applied voltage is −70 to −30V. In contrast, the applied voltage (inversion threshold voltage) necessary to reverse the direction of spontaneous polarization _{P S} in the bulk substrate made of LN crystal thickness 400 [mu] m (non-processing unit 2) is about 2400~8000V is there. In this manner, the applied voltage can be reduced according to the scaling law by thinning the substrate. The inversion threshold voltage varies depending on the crystal composition, and is 8000 V / 400 μm for CLN and 2400 V / 400 μm for SLN.

  In the experimental example conducted by the present inventor, an applied voltage of −40 V, a scanning speed of 10 μm / s, and a drawing pattern interval (interval between bold lines 43) of 1.5 μm are applied to the cutting portion 3 made of S-LN crystal having a thickness of 6 μm. In the case of drawing with, the line-shaped polarization inversion of 0.75 μm width (the inversion width and the non-inversion width are the same) has been succeeded. When the polarization inversion patterns on the first main surface (-C surface) 11 and the cutting surface (+ C surface) 13 at this time are compared, they match with high accuracy and are uniform patterns from the -C surface to the + C surface. It was also found that the polarization inversion is possible. When the ratio of the polarization inversion width to the non-inversion width is 1: 1 and the polarization inversion width and the non-inversion width are equal to the coherent length lc, the conversion efficiency is the highest.

Here, the “coherent length (lc)” will be described. As shown in FIG. 12, when a fundamental wave is incident on the optical waveguide 39 as the incident light 46, a second harmonic (SH wave) having a half wavelength (2ω) of the fundamental wave is obtained as the emitted light 47. The coherent length (lc) is obtained from equation (1). Here, k ^{ω is the} wave number of the fundamental wave, k ^{2ω is the} wave number of the SH wave, λ ₀ ^{ω is} the wavelength of the fundamental wave in vacuum, and n _e ^ω and n _e ^2ω are the refractions of the extraordinary rays of the fundamental wave and the SH wave, respectively. Rate.

図２１は、ＬＮ結晶における屈折率の波長分散曲線を示す。（１）式及び図２１からコヒーレント長を求めることが出来る。ＬＮ結晶及びＬＴ結晶におけるＳＨ波とコヒーレント長ｌｃとの関係を図２２（ａ）および図２２（ｂ）に示す。ＳＨ波の波長が短くなるにしたがって、コヒーレント長ｌｃも短くなり、短波長のＳＨ波を出力するには微小周期の分極反転構造が必要となることが分る。

FIG. 21 shows a wavelength dispersion curve of the refractive index in the LN crystal. The coherent length can be obtained from the equation (1) and FIG. 22A and 22B show the relationship between the SH wave and the coherent length lc in the LN crystal and the LT crystal. As the wavelength of the SH wave is shortened, the coherent length lc is also shortened, and it is understood that a domain-inverted structure with a minute period is required to output a short-wavelength SH wave.

  As described above, since the plate thickness of the cutting portion 3 having the first main surface 11 and the cutting surface 13 perpendicular to the spontaneous polarization Ps direction is formed extremely thin, the terrace-like thin plate of FIGS. By producing a quasi phase matching second harmonic generation device using the substrate 1, a fine periodic polarization inversion structure can be obtained. Therefore, a QPM-SHG device that outputs a short-wave SH wave having a short coherent length lc is obtained. By drawing a line-shaped periodic polarization reversal pattern using AFM, a fine periodic polarization reversal structure can be obtained by a simple and low-cost method. Accordingly, the QPM-SHG device that is a highly efficient blue coherent light source can be reduced in size and performance.

  In addition, the optical waveguide 39 can be formed from the −C plane (first main surface) 11 to the cutting plane 13 by forming the cutting portion 3 to be thin. As a result, both the + Z-direction and −Z-direction boundary surfaces of the optical waveguide 39 are in contact with air, so that the phenomenon of cut-off in which light escapes from the optical waveguide 39 is suppressed, and the light propagating through the optical waveguide 39 is suppressed. Propagation efficiency can be improved. Furthermore, since the refractive index difference between the substrate and air is large, the matching between the fundamental wave and the SH wave guided modes is improved, so that the SHG conversion efficiency is improved. By cutting the side surfaces in the + Y direction and the −Y direction of the optical waveguide 39, the boundary surfaces in the vertical and horizontal directions of the optical waveguide 39 can be all in contact with air, and the light propagation efficiency is further improved. The conversion efficiency of the SHG device is improved.

  Since the thickness of the cutting portion 3 having the first main surface 11 and the cutting surface 13 perpendicular to the spontaneous polarization direction is formed extremely thin, a minute polarization reversal structure can be easily formed by a minute applied voltage according to the scaling law. Can be formed.

By scanning the metal probe on the first main surface 11 of the cutting unit 3 with a predetermined voltage applied, a domain-inverted structure according to the scanning pattern can be formed. Therefore, as shown in FIG. 15B, a fine periodic domain-inverted structure can be easily formed by scanning the metal probe in a line at a predetermined interval.
(Third embodiment)
FIG. 16 shows a high density formed by writing minute polarization inversion dots at a high density on the cutting portion 3 of the terrace-shaped thin plate substrate 1 as an example of the domain inversion structure according to the third embodiment of the present invention. It is a perspective view which shows a recording medium.

  In the high-density recording medium according to the third embodiment, dot-shaped minute domain-inverted regions (dot memory) 51 are formed at a high density in the cutting portion 3 of the terrace-shaped thin plate substrate 1 shown in FIGS. The memory device that has been written. The dot memory 51 is a polarization inversion region (domain) in which the spontaneous polarization direction Ps of the terrace-shaped thin plate substrate 1 is inverted, and a plurality of dot memories 51 are formed in a matrix at regular intervals. One-bit information is stored depending on whether the spontaneous polarization direction Ps is upward or downward.

  As a method for reversing the polarization of the minute dot memory 51 (memory writing method), a focused electron beam 52 or laser light is irradiated onto the cutting unit 3 or, as described above, locally using an AFM or the like. There is a method of applying a voltage to the above. As a memory reading method, there are a method using SNDM and a piezoelectric detection method. Here, the “piezoelectric detection method” is a method of reading stored information by applying a voltage between electrodes formed on the front and back surfaces of the terrace-shaped thin plate substrate 1 and observing domain inversion. When an AC voltage is applied between the electrodes formed on the front and back surfaces of the terrace-shaped thin plate substrate 1, the substrate 1 contracts in the direction of the electric field by a + signal and extends by a-signal. Therefore, if the domain is reversed, the substrate 1 expands and contracts. Since the domain inversion unit is different, the stored information can be detected by the AFM. According to this method, it is possible to detect a dot size of about 50 nmφ.

When the thickness of the cutting portion 3 is 1 μm, the diameter of one dot memory 51 can be formed to about 3 nmφ. Accordingly, for example, when the dot memory 51 is formed at a pitch of 10 nm, 10 ⁶ × 10 ⁶ dot memories 51 can be formed in a 1 cm square region, so that a high-density recording medium of 1 Tbit / cm ² can be obtained. Can be produced.

Ferroelectric optical crystals such as LN crystal and LT crystal are not easily affected by an external magnetic field or electric field, and have a high environmental resistance such as a stable polarization structure even at a high temperature of about 600 ° C. Therefore, information can be stored stably over a long period of time.
(Fourth embodiment)
FIG. 17 was produced by forming minute dot-shaped etching holes 53 in the cutting portion 3 of the terrace-shaped thin plate substrate 1 as an example of the domain-inverted structure according to the fourth embodiment of the present invention. It is a perspective view which shows a photonic crystal.

  The photonic crystal according to the fourth embodiment is formed by arranging minute dot-shaped etching holes 53 in the cutting portion 3 of the terrace-shaped thin plate substrate 1 so as to form a hexagonal shape. The diameter of the etching hole 53 varies depending on the wavelength of light to propagate, but is about 400 nmφ for infrared light with λ = 1.5 μm, for example. As shown in FIG. 17, the optical waveguide surrounded by the etching hole 53 is formed along the X direction, and the etching hole 53 is not formed in the optical waveguide.

  The light incident on the slab optical waveguide travels in the + X direction in the cutting portion 3. The etching hole 53 functions as a Bragg reflector for incident light. Therefore, the incident light is reflected by the etching hole 53 in the optical waveguide, the light interaction is strong, and the wavelength of the light in the crystal is short (up to about 1/100). The incident light becomes a slow wave in the crystal, and the length (˜10 mm) of the optical waveguide formed in the cutting portion 3 becomes long (about 100 times) when viewed from the incident light. Thereby, the material constant of the optical waveguide can be effectively increased.

  In the slab optical waveguide, there is light confinement in the vertical direction (Z direction), but there is no light confinement in the horizontal direction (Y direction), so optical waveguide is not performed, but Bragg reflection occurs due to etching holes. As a result, light is confined in the lateral direction (Y direction). The wavelength of light propagating through the slab optical waveguide is shortened to about 1/10 to 1/100 of the wavelength of light propagating through the three-dimensional optical waveguide formed in the same manner in the cutting portion 3.

As a photonic crystal formation method, the first main surface 11 or the cut surface 13 is etched using a nitric acid having a high etching rate with respect to the -C plane by reversing the polarization of the LN crystal in a region where the etching hole 53 is to be formed. As a result, the etching hole 53 can be formed in the domain-inverted region. As described above, the polarization inversion method includes a method of irradiating the cutting part 3 with a converged electron beam or laser light, or a method of locally applying a voltage using AFM or the like.
(Fifth embodiment)
FIG. 18 is produced by forming minute dot-like etching holes 53b in the cutting portion 3 of the terrace-like thin plate substrate 1 as an example of the domain-inverted structure according to the fifth embodiment of the present invention. It is a perspective view which shows a Fabry-Perot resonator. FIG. 18 partially shows the cutting portion 3 of the terrace-shaped thin plate substrate 1, but the actual device has a non-processing portion 2 and a cutting portion 3 as shown in FIGS. 16 and 17. Is produced in a state of being integrated.

The Fabry-Perot resonator according to the fifth embodiment surrounds the area to be the optical waveguide 39c in the cutting portion 3 with a plurality of etching holes 53b in the same manner as the photonic crystal of FIG. Since the etching hole 53b functions as a light reflecting mirror, the incident light 56 input to one end of the optical waveguide 39c is reflected by the etching hole 53b and propagates through the optical waveguide 39c surrounded by the etching hole 53b. If a dopant such as Nd is diffused in this portion, an optical amplification effect occurs. In the middle of the optical waveguide 39c, two reflection mirrors 55 made of etching holes are formed facing each other. Light is confined between the two reflecting mirrors 55 facing each other to cause laser oscillation. The laser light is output as outgoing light 57. As described above, a high-reflectance mirror that is usually formed by cleavage, polishing, etching, or the like is formed as the reflection mirror 55 using the etching hole 53c.
(Sixth embodiment)
FIG. 19 is a cross-sectional view showing an SHG optical modulator according to the sixth embodiment. In the optical modulator, a part of the optical fiber 63 in which light propagates in the core 61 covered with the clad 62 is cut off, and a QPM-SHG device 64 is inserted on the light propagation axis. Furthermore, although illustration is omitted, electrodes are formed on the front and back surfaces of the QPM-SHG device 64, and an electric field can be applied to the optical waveguide of the QPM-SHG device 64 in the same direction as the polarization direction. Since the refractive index of the ferroelectric optical crystal changes according to the applied voltage, the effective period of the domain-inverted structure changes, and the quasi phase matching wavelength can be adjusted. Therefore, by applying a voltage, the phase matching condition collapses and the light conversion efficiency changes. Thereby, the output of the SH wave can be controlled while keeping the input of the fundamental wave constant.
(Seventh embodiment)
FIG. 20 is a perspective view showing an optical modulator according to the seventh embodiment. FIG. 20A is an implementation diagram of a Mach-Zehnder (MZ) type optical modulator. Two Y-branch waveguides are formed on the terrace substrate 3 so as to oppose each other, and a photonic crystal composed of an etching hole is formed on a straight line connecting the two arms of the Y-branch. Has no holes. A polarization inversion region (domain inversion region) is formed in one region of the arm. Although omitted in FIG. 20A, electrodes are formed on the upper surface 11 and the lower surface 13 of the terrace substrate 3. When a voltage is applied to the upper and lower electrodes, in the arm part, when one refractive index increases or decreases, the other decreases, so the speed of propagating light is different, and when combined at the Y branch at the exit, the emitted light turns on and off. To perform optical modulation. At this time, the light propagation speed of the arm portion is a slow wave of 1/10 to 1/100 due to the action of the photonic crystal, so the same characteristics can be obtained with a conventional length of 1/10 to 1/100. It is done. Therefore, this optical modulator can be the fiber embedded type described in the sixth embodiment.

  FIG. 20B is a perspective view of an optical modulator having the same configuration as that of FIG. 20A, but there is no polarization inversion region on one side of the arm part, and the electrode is only on the upper part 11 side. Different. The operating voltage (voltage required for on-off) is slightly higher than that of the embodiment of FIG. 20A, but the fiber length can be embedded because the element length is 1/10 to 1/100 as compared with the prior art. .

  FIG. 20C shows a Fabry-Perot (FP) resonator type optical modulator. Although omitted in FIG. 20 (c), electrodes are attached to the surfaces of the upper part 11 and the lower part 13 of the terrace substrate 3. When a voltage is applied, the refractive index of the FP resonator portion changes and the resonance wavelength changes. Therefore, when input light having a constant wavelength is input, an optical signal modulated from the output end appears. This element length can be made extremely short, and a fiber-embedded compact and high-performance optical modulator can be realized.

  As described above, the present invention has been described with reference to six embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art.

  For example, in FIG. 2, the terrace-shaped thin plate substrate 1 in which the first main surface is the −C plane and the second main surface and the cutting surface 13 is the + C plane has been described. A terrace-shaped thin plate substrate having the main surface as the + C plane and the second main surface and the cutting surface 13 as the −C plane may be manufactured.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

It is a perspective view which shows the whole structure of the terrace-shaped thin plate board | substrate concerning the 1st Embodiment of this invention. It is the perspective view which expanded a part of cutting part 3 enclosed with the dotted line 5 of FIG. It is a flowchart which shows the procedure of the preparation methods of the terrace-shaped thin board | substrate 1 shown in FIG.1 and FIG.2. FIGS. 4A and 4B are diagrams for explaining step S01 (crystal cutting) in FIG. It is a figure explaining step S03 (with an electrode) of FIG. It is a figure explaining step S04 (surface protection) of FIG. It is a figure explaining step S05 (mounting) of FIG. It is a figure explaining step S07 (chipping removal) of FIG. It is a figure explaining step S08 (terrace processing) of FIG. It is a figure explaining step S09 (dimension measurement) of FIG. 11A is a cross-sectional view showing a ridge processing method using a dicer, and FIG. 11B shows a state of a thin plate (ridge) portion of a substrate manufactured by the ridge processing method of FIG. 11A. It is a perspective view. FIG.11 (c) is sectional drawing which shows the terrace process in the 1st Embodiment of this invention. It is a perspective view which shows the structure of the QPM-SHG device formed in the cutting part 3 of the terrace-shaped thin board | substrate 1 concerning the 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the manufacturing method of the QPM-SHG device shown in FIG. It is a figure explaining step S21 (mount) of FIG. FIG. 15A is a diagram illustrating step S22 (drawing) in FIG. 13, and FIG. 15B is a diagram illustrating an example of a drawing pattern in step S22 (drawing). As an example of the domain-inverted structure according to the third embodiment of the present invention, a high-density recording medium formed by writing minute domain-inverted dots at high density on the cutting portion 3 of the terrace-shaped thin plate substrate 1 is shown. It is a perspective view. As an example of the domain-inverted structure according to the fourth embodiment of the present invention, a photonic crystal produced by forming minute dot-shaped etching holes 53 in the cutting portion 3 of the terrace-like thin plate substrate 1 is shown. It is a perspective view shown. As an example of the domain-inverted structure according to the fifth embodiment of the present invention, a Fabry-Perot resonator manufactured by forming minute dot-shaped etching holes 53 in the cutting portion 3 of the terrace-shaped thin plate substrate 1. FIG. It is sectional drawing which shows the SHG optical modulator by which the QPM-SHG device was inserted in the optical fiber concerning 6th Embodiment. 20A is a perspective view showing an MZ optical modulator (upper and lower electrode configuration), FIG. 20B is a perspective view showing an MZ optical modulator (upper electrode configuration), and FIG. It is a perspective view which shows an FP resonator type | mold optical modulator. The wavelength dispersion curve of the refractive index in a LN crystal is shown. FIG. 22A and FIG. 22B are graphs showing the relationship between the SH wave and the coherent length lc in the LN crystal and the LT crystal. It is a perspective view which shows the structure of the QPM-SHG device concerning a prior art.

Explanation of symbols

lc ... Coherent length 1 ... Terrace-shaped thin plate substrate 2 ... Non-processed part 3 ... Cutting process part 4 ... Corner drop part 5 ... Dotted line 11 ... 1st main surface (-C surface)
12 ... 2nd main surface (+ C surface)
13, 13b ... Cutting surface 14 ... Step surface 15 ... Curved portion 21 ... Wafer 22, 23 ... Cut line 24 ... Base 25 ... Syringe 26 ... Filter 27 ... Spinner 28 ... Hot plate 29 ... Soda glass plate (base)
30a, 30b ... jig 31 ... strip substrate 32 ... ultra-thin outer peripheral edge 33 ... chipping 34 ... side 36 ... stage 37 ... LN crystal substrate 38 ... ridge 39, 39c, 39d ... optical waveguide 40a, 40b ... groove 41a-41g ... non-polarization inversion layer 42 ... conductive film 43 ... thick line 44 ... thin wire 45a to 45g ... polarization inversion layer 46, 56 ... incident light 47, 57 ... outgoing light 48 ... stage 51 ... dot memory (polarization inversion region)
52 ... Electron beam 53, 53b, 53c ... Etching hole 55 ... Reflection mirror 61 ... Core 62 ... Cladding 63 ... Optical fiber 64 ... SHG device

Claims (13)

A ferroelectric optical crystal substrate having a first main surface that is a plane perpendicular to the direction of spontaneous polarization, used to produce a device having a domain-inverted structure,
A non-processed portion having the first main surface and a second main surface opposite to the first main surface;
A cutting portion disposed on the outer periphery of the ferroelectric optical crystal substrate, the cutting portion having the first main surface and a cutting surface facing the first main surface;
A terrace-shaped thin plate substrate, wherein a distance between the first main surface and the cutting surface is shorter than a distance between the first main surface and the second main surface.   2. The terrace according to claim 1, wherein the cutting surface is curved toward the second main surface and intersects the second main surface at a boundary portion between the cutting portion and the non-processing portion. Thin plate substrate. A ferroelectric optical crystal substrate whose first main surface is a plane perpendicular to the direction of spontaneous polarization using a device that scrapes off a part of the workpiece with an ultra-thin outer peripheral blade attached to the tip of a spindle that rotates at high speed. Is disposed on the outer periphery of the ferroelectric optical crystal substrate, and a non-processed portion having the first main surface and a second main surface opposite to the first main surface, A method of producing a terrace-shaped thin plate substrate comprising a cutting portion having the first main surface and a cutting surface facing the first main surface,
A first step of installing the ferroelectric optical crystal substrate on the apparatus so that the first main surface is parallel to the radial direction of the ultra-thin outer peripheral blade;
The ferroelectric optical crystal is formed by pressing the ultra-thin outer peripheral blade against a side surface of the ferroelectric optical crystal substrate that connects the first main surface and the second main surface facing the first main surface. A second step of scraping a part of the substrate,
In the second step, first, the surface portion including the second main surface is scraped off by pressing the ultra-thin outer peripheral blade against the side end portion on the second main surface side. Cutting that shortens the distance between the first main surface and the cutting surface by repeatedly performing an operation of pressing the ultra-thin outer peripheral blade against the side surface end on the cutting surface side and scraping off the surface layer portion including the cutting surface. A method for producing a terrace-like thin plate substrate, comprising thinning a processed portion.   4. The method for producing a terrace-shaped thin plate substrate according to claim 3, wherein the operation of scraping the surface layer portion including the cutting surface is performed in a plurality of times. A quasi-phase matched second harmonic generation device using the terrace-shaped thin plate substrate according to claim 1 or 2,
An optical waveguide formed in the cutting portion;
Along the optical waveguide, a polarization inversion layer in which the spontaneous polarization direction is inverted and a non-polarization inversion layer in which the spontaneous polarization direction is not inverted and remains in the spontaneous polarization direction of the terrace-shaped thin plate substrate are alternately formed. Periodic polarization reversal structure
The length along the optical waveguide of the polarization inversion layer and the non-polarization inversion layer is a coherent length, respectively.   6. The quasi phase matching second harmonic generation device according to claim 5, wherein the optical waveguide is formed from the first main surface to the cutting surface. A high-density recording medium using the terrace-shaped thin plate substrate according to claim 1 or 2,
In the cutting portion, dot-like domain-inverted regions in which the spontaneous polarization direction is inverted are formed in a matrix at regular intervals, and 1-bit information depending on whether the spontaneous polarization direction in each of the matrix regions is upward or downward. A high-density recording medium characterized by storing A laser using the terrace-shaped thin plate substrate according to claim 1,
A plurality of dot-shaped etching holes formed in the cutting portion;
An optical waveguide surrounded by the plurality of dot-shaped etching holes;
Two reflecting mirrors made of dot-like etching holes formed opposite to each other in the middle of the optical waveguide;
Means for amplifying and oscillating light confined between the two opposing reflecting mirrors. An optical modulator using the terrace-shaped thin plate substrate according to claim 1 or 2,
Two Y-polarized waveguides formed to face the cut portion;
An optical waveguide formed in a linear region connecting the arms of the two Y-branch waveguides and surrounded by a plurality of dot-like etching holes;
The polarization inversion layer formed in one of the linear regions of the arm and having the spontaneous polarization direction inverted along the linear region and the spontaneous polarization direction of the terrace-shaped thin plate substrate remains unchanged. A periodically poled structure in which a certain non-polarized layer is alternately formed;
An optical modulator comprising: a pair of electrodes formed on at least the first main surface and the cutting surface of the linear region of the cutting portion. An optical modulator using the terrace-shaped thin plate substrate according to claim 1 or 2,
Two Y-polarized waveguides formed to face the cut portion;
An optical waveguide formed in a linear region connecting the arms of the two Y-branch waveguides and surrounded by a plurality of dot-like etching holes;
An optical modulator comprising: an electrode formed on at least the first main surface of the linear region of the cutting portion. An optical modulator using the terrace-shaped thin plate substrate according to claim 1 or 2,
A plurality of dot-shaped etching holes formed in the cutting portion;
An optical waveguide surrounded by the plurality of dot-shaped etching holes;
Two reflecting mirrors formed of dot-like etching holes formed opposite to each other in the middle of the optical waveguide;
An optical modulator comprising: a pair of electrodes formed on at least the first main surface and a cutting surface of a region sandwiched between the two reflecting mirrors of the optical waveguide. A polarization inversion method for forming a minute polarization inversion region on a terrace-shaped thin plate substrate produced by the method for producing a terrace-shaped thin plate substrate according to claim 3 or 4,
A third step of forming a conductive film on the cutting surface of the terrace-shaped thin plate substrate;
A fourth step of bringing the tip of the metal probe closer to the first main surface of the cutting portion;
A fifth step of applying a predetermined voltage between the conductive film and the metal probe to reverse the direction of spontaneous polarization of the ferroelectric optical crystal in a region where the tip of the metal probe is brought close to A method for reversing the polarization of a terrace-shaped thin plate substrate.   13. The terrace-shaped thin plate substrate according to claim 12, wherein in the fifth step, the metal probe is scanned on the first main surface of the cutting portion while a predetermined voltage is applied. Polarization reversal method.

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