JP2005345813A - High speed optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high speed optical scanner capable of performing high speed optical scanning capable of following light communication speed without incurring increase in a scale of the device and reduction of scanning accuracy. <P>SOLUTION: The high speed optical scanner is provided with a light controlling type optical deflector 3 scanning a serial light signal sequence 2 emitted from an optical fiber transmission line 1 in an axis X direction based on a controlling signal light beam 4, a light condensing optical system 6 condensing a scanning light beam 5 of the serial light signal sequence 2 and a light controlling type optical deflector 7 scanning the condensed serial light signal sequence 2 in an axis Y direction based on a controlling signal light beam 8 and each signal unit of the serial light signal sequence 2 is expanded on a two-dimensional plane 10 by a two-dimensional scanning light beam 9. A nonlinear optical material member whose transmittance or refractive index is changed according to intensity of irradiation with light is built in the light controlling type optical deflectors 3 and 7, interference fringes having spatial frequencies according to the controlling signal light beams 4 and 8 are formed in the nonlinear optical material member and the serial light signal sequence 2 is diffracted by the formed interference fringes to perform scanning. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-speed optical scanning device that scans a light beam carrying a high-speed and large-capacity serial signal of, for example, 1 Tbits / s or more at an ultra-high speed, and is used, for example, in an information output device such as an image display display or a printer. The present invention relates to a high-speed optical scanning device.

With the progress of optical communication technology, the amount of information transmitted per unit time has increased dramatically, and in response to such circumstances, devices that output information to information output terminal devices such as displays, recording, printing devices, etc. Also, there is a demand for higher speed and larger capacity.
Under such circumstances, a technology for rapidly converting a serial optical signal train transmitted at high speed into a two-dimensional parallel optical signal at a receiving terminal is a key technology for dramatically improving the amount of information from an output terminal. It is.

  As a conventional method for converting a serial optical signal train into a parallel optical signal, a scanning method using a mechanically driven scanning means such as a galvanometer mirror, a polygon mirror, or a hologram scanner has been known for a long time. The device becomes larger. In addition, since the scanning speed is slow (several ms to μs / deg) and a high speed operation is attempted, the accuracy is greatly lowered, so that it is not suitable for an application that requires high-speed conversion of an optical signal. .

  On the other hand, a scanning method using electrical deflection control means such as an electro-optic effect and an acousto-optic effect is also known. The scanning method using these electric deflection control means has a fast response speed, and can use a band of about 1 GHz using the electro-optic effect and about several tens of MHz using the acousto-optic effect. It is.

However, in the above-described scanning method using the electrical deflection control means, the scanning angle is generally small, and the number of decompositions per scanning line is about 10 ^3, which is one digit or more smaller than the mechanical drive scanning means. turn into.
Furthermore, the scanning method using the electrical deflection control means can significantly increase the response speed compared to the scanning method using the mechanical drive scanning means, but the serial optical signal train transmitted at high speed. It is difficult to realize high-speed scanning that can follow (several tens of G to several Tbits / s).

  The present invention has been made in view of the above circumstances, and provides a high-speed optical scanning device capable of high-speed optical scanning capable of following the communication speed of light without causing an increase in the size of the device and a decrease in scanning accuracy. It is intended to do.

The first high-speed optical scanning device of the present invention comprises a light control type optical deflector that scans an incident serial optical signal string in a predetermined direction based on the input control signal light,
The light control type optical deflector incorporates a nonlinear optical material member whose transmittance or refractive index changes according to the irradiation intensity of light, and the nonlinear optical material member has interference with a spatial frequency according to the control signal light. The scanning is performed by forming fringes and changing the spatial frequency of the interference fringes to change the diffraction direction of the incident serial optical signal sequence.

The second high-speed optical scanning device of the present invention includes a first light control type optical deflector that scans an incident serial optical signal string in a first direction based on the input control signal light, and
A condensing optical system for condensing the serial optical signal string scanned in the first direction;
Based on the input control signal light, which is arranged at a condensing position by the condensing optical system, the condensing serial optical signal string is scanned in a second direction different from the first direction. 2 light control type optical deflectors,
Each of the first light control type optical deflector and the second light control type optical deflector incorporates a nonlinear optical material member whose transmittance or refractive index changes according to the irradiation intensity of light. An interference fringe having a spatial frequency corresponding to the control signal light is formed on the member, and by changing the spatial frequency of the interference fringe, the diffraction direction of the incident serial optical signal train is changed, and the scanning is performed. It is characterized by doing.

Furthermore, in any one of the high-speed optical scanning devices described above, the scanning drive timing of the first optical control type optical deflector and the second optical control type optical deflector is a predetermined timing of the serial optical signal sequence. Configured to synchronize with
It is preferable that a two-dimensional parallel optical signal is output from the second light control type optical deflector.

Further, the control signal light is pulsed light,
A widening optical system for widening the pulsed light in a direction substantially orthogonal to the traveling direction of the pulsed light;
A delay time addition optical system that performs different time delay processing for each spatial position of the pulse light widened by the widening optical system;
It is preferable to include a condensing optical system for condensing the pulsed light subjected to the time delay processing by the delay time adding optical system onto the nonlinear optical material member.

In the time delay processing by the delay time adding optical system, the widened pulsed light is separated from the central axis in a predetermined plane including the central axis of the light beam substantially symmetrically with respect to the central axis. In accordance with the time delay amount gradually, increasing or decreasing,
When the pulsed light focused on the nonlinear optical material member reaches the surface of the nonlinear optical material member, the crossing angle of the wave fronts of the light beams that are substantially symmetrical is gradually increased with time. Changed to increase or decrease,
The nonlinear optical material member is preferably configured such that interference fringes having a spatial frequency corresponding to the size of the intersection angle are formed.

  Further, the delay time adding optical system can be configured to perform time delay processing by a deflection optical element.

  The deflecting optical element may be composed of a plurality of optical elements having lens characteristics, and the delay time may be changed according to the incident position of light on the optical element.

  Further, the deflecting optical element may include a prism optical element, and the delay time may be changed according to the optical path length in the prism optical element of the light incident on the prism optical element.

  According to the high-speed optical scanning device of the present invention, a serial optical signal transmitted at high speed can be diffracted and scanned using an interference fringe that can be modulated according to the speed of light, and converted into a parallel optical signal at ultra high speed. Therefore, high-speed optical scanning capable of following the communication speed of light is possible without causing an increase in size and scanning accuracy of the apparatus.

  This makes it possible to perform advanced information processing in real time, such as ultra-high-definition and high-density images, which was impossible with conventional scanning methods using electrical deflection control means. Transmission processing technology can be greatly changed.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a configuration of a high-speed optical scanning device according to an embodiment of the present invention.
As shown in FIG. 1, the high-speed optical scanning device of the present embodiment uses a serial optical signal sequence 2 emitted from an optical fiber transmission line 1 in a first direction (FIG. 1) based on input control signal light 4. The first light control type optical deflector 3 that scans in the X-axis direction), a condensing optical system 6 that condenses the scanning light 5 of the serial optical signal string 2, and a condensing position by the condensing optical system 6. A second optical system that scans the condensed serial optical signal sequence 2 in a second direction different from the first direction (the Y-axis direction in FIG. 1) based on the input control signal light 8. The optical control type optical deflector 7 and the scanning light 9 which is output from the second optical control type optical deflector 7 and scanned two-dimensionally, each signal unit of the serial optical signal sequence 2 is 2 Developed on the dimension plane 10.

  In the present embodiment, the first direction and the second direction are the X-axis direction and the Y-axis direction that are orthogonal to each other. Instead, any two different directions in the XY plane are used. Can be selected.

Hereinafter, the operation of the high-speed optical scanning device according to the embodiment will be described.
As described above, the serial optical signal train 2 emitted from the optical fiber transmission line 1 is incident on the first light control type optical deflector 3. The serial optical signal train 2 is an ultrafast optical pulse signal train of about several tens GHz to several THz.
The operation of the first optical control type optical deflector 3 is controlled by the control signal light 4, and the incident serial optical signal string 2 is reciprocally scanned in the first direction (X-axis direction in FIG. 1) to obtain the scanning light 5. Is output.
Since the optical scanning by the first light control type optical deflector 3 is performed by all-optical light control without an electrical control mechanism, ultra-high speed scanning is possible.

Next, the scanning light 5 in the first direction output from the first light control type optical deflector 3 is incident on the second light control type optical deflector 7 via the condensing optical system 6. Is done.
The second light control type optical deflector 7 is controlled in operation by the control signal light 8, and reciprocally scans the focused scanning light 5 in the second direction (Y-axis direction in FIG. 1) in a two-dimensional manner. The scanning light 9 to be scanned is output.
Similarly to the first light control type light deflector 3, the second light control type light deflector 7 is also controlled by all-optical light control without an electrical control mechanism, so that ultra-high speed scanning is performed. Is possible.

  The scanning drive timings of the first light control type optical deflector 3 and the second light control type optical deflector 7 are configured to be synchronized with a predetermined signal timing of the serial optical signal string 2. Yes.

  Specifically, the first light control type optical deflector 3 and the second light control type optical deflector 7 are driven and controlled by the configuration shown in FIG. Since the first light control type optical deflector 3 and the second light control type optical deflector 7 have substantially the same configuration, the first light control type optical deflector 3 is a representative example here. Will be described.

As described above, the light control type optical deflector 3 is driven and controlled by the control signal light 4. In the present embodiment, a short pulse light is used as the control signal light 4. That is, for example, laser light having a pulse width on the order of picoseconds to femtoseconds output from a semiconductor laser or a solid-state laser is used. In particular, a laser light source such as a Ti ³⁺ : Al ₂ O ₃ laser, a Cr ⁴⁺ : YAG laser, a Cr ⁴⁺ : LiSAF laser, or an Nd ³⁺ : YVO ₄ laser capable of a high repetition rate of GHz or higher is preferably used.

The short pulse light as the control signal light 4 input into the light control type optical deflector 3 is widened in the direction orthogonal to the optical axis in the widening optical system 11 and converted into slit-like light 12.
The widening optical system 11 may be a general beam expander configured by a combination of a concave lens and a convex lens or two convex lenses. In particular, the control signal light 4 is a high-strength ultrashort light having a frequency of 100 femtoseconds or less. In the case of pulsed light, a concave mirror may be used instead of the convex lens.

  The slit-shaped light 12 output from the widening optical system 11 is input to the delay time adding optical system 13, and different delay times are added depending on the spatial position. The addition of the delay time is, for example, as shown in FIG. 2, in a predetermined plane including the central axis of the luminous flux, the broadened short pulse light (12) is substantially symmetrical with respect to the central axis. And it deform | transforms so that a time delay may increase gradually as it leaves | separates from a central axis. Various other modes can be selected as the mode of adding the delay time. For example, in the control signal light 4, the delay time in the vicinity of the central axis is the largest, and the time delay gradually increases as the distance from the central axis increases. You may make it decrease.

The light 14 with the added delay time output from the delay time adding optical system 13 is condensed by the condensing optical system 15 and input to the nonlinear optical material member 17 in a state where the light wavefront 16 is converged. The
On the nonlinear optical material member 17, light that has been deformed by adding different delay times depending on the spatial position is collected and input, so that time elapses according to the deformed shape of the light. At the same time, interference fringes whose spatial frequency changes are formed.

  Hereinafter, the formation process of the interference fringes in which the spatial frequency changes will be described with reference to FIG.

The light wavefront 16 of the light from the condensing optical system 15 has a time delay in the peripheral portion rather than the central portion.
Therefore, as shown in FIG. 3A, when the front end portion 18 and the front end portion 19 of the light wavefront 16 are incident on the nonlinear optical material member 17 and lightwave interference occurs, the cross incident angle 20 formed between the lightwavefronts is small. The spatial frequency of the interference fringes formed on the nonlinear optical material member 17 is low.

  Next, as shown in FIG. 3B, the intermediate portion 21 and the intermediate portion 22 of the light wavefront 16 that are located between the center portion and the peripheral portion and have a time delay larger than those of the tip portion 18 and the tip portion 19 When light wave interference occurs when entering the nonlinear optical material member 17, the cross incident angle 23 formed by the light wave fronts of each other is larger than the cross incident angle 20, and the interference fringe space formed on the nonlinear optical material member 17. The frequency is higher than that shown in FIG.

  Further, as shown in FIG. 3C, the time delay is larger than that of the intermediate portion 21 and the intermediate portion 22, and the end portion 24 and the end portion 25 located in the peripheral portion of the optical wavefront 16 are formed in the nonlinear optical material member 17. When incident and light wave interference occurs, the cross incident angle 26 formed by the light wave fronts of each other is further larger than the cross incident angle 23, and the spatial frequency of the interference fringes formed on the nonlinear optical material member 17 is the above figure. It becomes higher than the case shown in 3 (b).

As described above, in this embodiment, the light wavefront whose cross incident angle gradually increases with the passage of time is incident on the nonlinear optical material member 17 so that interference fringes whose spatial frequency gradually increases with the passage of time are formed. It is configured.
The interference fringes formed in this way function as a diffraction grating, and the grating pitch changes so as to become gradually smaller, so the diffraction angle also changes gradually.

  Accordingly, in this state, when the serial optical signal string 2 is incident on the interference fringe forming portion of the nonlinear optical material member 17, the serial optical signal string 2 is diffracted in a direction corresponding to the spatial frequency of the interference fringes. The deflection direction of the light can be continuously changed, so that the optical scanning can be performed.

  The nonlinear optical material member 17 preferably has a high-speed response characteristic. For example, a semiconductor material having a GaAs thin film structure, or organic materials such as phthalocyanine, merocyanine, polycyan, polydiacetylene, polyarylene vinylene, diethylaminonitro. Stilbene or squarylium dyes can be used.

  In addition, as the above-described delay time adding optical system 13, various types can be adopted. Hereinafter, a specific mode of the delay time adding optical system 13 will be described with reference to FIGS. 4 and 5. In addition, regarding the light control type optical deflectors 3a and 3b shown in each drawing, the same reference numerals are given to the same elements as those of the light control type optical deflector 3 in FIG. 2, and the detailed description thereof is omitted.

FIG. 4 shows the delay time adding optical system 13a according to the first embodiment.
In this delay time adding optical system 13a, the spatially widened short pulse light (12) is transmitted through the two diffraction lenses 27a and 27b, so that the optical path at the center of the light beam and the optical path at the periphery of the light beam An optical path length difference is generated between the two. That is, the first diffractive lens 27a has a function as a convex lens, while the second diffractive lens 27b also has a function as a convex lens, and the light sequentially transmitted through the two diffractive lenses 27a and 27b is shown in the drawing. In this way, the light is output as the light 14a to which the delay time is added.

  Hereinafter, the relationship between the lens characteristics of the diffractive lenses 27a and 27b and the time delay amount resulting therefrom will be described. In both cases, when two diffractive lenses having a focal length f are arranged at an interval 2f, the delay amount (optical path length difference) Δl of the light that has passed through the peripheral portion relative to the light that has passed through the central portion is expressed by the following formula ( 1). Here, D is the diameter of the diffractive lens.

For example, a case is assumed where short pulse light having a pulse width of 100 fs is expanded into a parallel light beam having a width of 50 mm. At this time, if the diameter D of the diffractive lens is set to 50 mm and the focal length f is set to 50 mm, the optical path length difference Δl of each light passing through the central portion and the peripheral portion is 11.8 mm from the above equation (1).
The amount of time delay is about 39 ps because it is a value obtained by dividing Δl by the speed of light. That is, one reciprocation scanning time is about 39 ps.
Thus, by using a diffractive optical element, a relatively large time delay can be generated with a simple configuration.

  Next, the deflection angle of the serial optical signal string 2 due to the interference fringes formed on the nonlinear optical material member 17 will be described. Here, a case where a diffraction order of + 1st order is used will be described.

As described above, this deflection angle is determined by the spatial frequency of the diffraction grating due to the interference fringes, and this spatial frequency depends on the numerical aperture NA of the condenser lens 15.
That is, the spatial frequency p (lp / mm) of the interference fringes formed on the nonlinear optical material member 17 is expressed by the following equation (2). Here, λ is the wavelength of light.

For example, it is assumed that the light 14a is collected by the condenser lens 15 having a diameter D of 50 mm and a focal length f of 50 mm. At this time, when the wavelength λ of the control signal light 4 is set to 780 nm, the spatial frequency of the interference fringes formed on the nonlinear optical material member 17 is O to 1146 (lp / mm) from the above equation (2). .
Therefore, when the wavelength of the serial optical signal string 2 is set to 1.5 μm, the diffraction angle changes in the range of 0 to 12.9 degrees. That is, the deflection angle is in the range of 0 to 12.9 degrees.

  Here, a transmissive diffractive optical element is described, but a reflective diffractive optical element can be used instead. In particular, when the control signal light 4 is a high-intensity ultrashort pulse light of 100 femtoseconds or less, it is preferable to use a reflective structure with little dispersion and absorption.

  In order to increase the amount of time delay in the delay time adding optical system 13a, a plurality of sets of the diffraction lenses 27a and 27b as described above are arranged in series, or the NA of the diffraction lenses 27a and 27b is increased. Is effective.

  The delay time adding optical system having lens characteristics is not limited to a diffractive lens, and a commonly used glass lens or the like may be used.

Next, the delay time addition optical system 13b according to the second aspect will be described with reference to FIG.
In this delay time adding optical system 13b, the spatially widened short pulse light (12) is divided into two on the optical axis by the two total reflection mirrors 31a and 31b, and the divided short pulse light. (12) is incident on the corresponding triangular glass prisms 28a and 28b via the total reflection mirrors 31c and 31d, respectively, and is transmitted through the glass prisms 28a and 28b, so that An optical path length difference is generated between the optical path around the light beam and the optical path. In other words, the light at the central portion of the light beam and the light at the peripheral portion of the light beam are incident on the optical system 15 due to a difference in optical path length in both the interval until the light enters the glass prisms 28a and 28b and the glass prisms 28a and 28b. The light is output as light 14b having a time delay between the central portion and the peripheral portion of the luminous flux.

  Thus, by using a glass prism, the light efficiency can be improved compared to the case of using a diffractive optical element, the optical element can be easily manufactured, and the manufacturing cost can be reduced. Has the advantage of being able to

Note that the high-speed optical scanning device of the present invention is not limited to the above-described embodiment, and various other modifications can be made.
For example, in the above-described embodiment, the serial optical signal train is scanned two-dimensionally using two light control type optical deflectors, but only one light control type optical deflector is used. It is also possible to configure to serially scan the serial optical signal train. In such a configuration, only the main scanning may be performed by the apparatus of the present invention in combination with another optical scanning method for performing sub-scanning.

Schematic which shows the structure of the high-speed optical scanning device concerning embodiment of this invention. 1 is a block diagram showing a schematic configuration of the light control type optical deflector shown in FIG. The figure for demonstrating a mode that the interference fringe from which a spatial frequency changes gradually is formed on a nonlinear optical material member ((a)-(c)). Schematic showing a specific mode (first mode: when a diffractive lens is used) of the delay time adding optical system shown in FIG. Schematic showing a specific mode (second mode: when a prism is used) of the delay time adding optical system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber transmission line 2 Serial optical signal sequence 3 1st light control type optical deflector 3a, 3b Light control type optical deflector 4, 8 Control signal light 5, 9 Scanning light 6, 15 Condensing optical system 7 2nd Light control type optical deflector 10 Two-dimensional plane 11 Widening optical system 12 Slit-like light 13, 13 a, 13 b Delay time addition optical systems 14, 14 a, 14 b Light 16 with added delay time Light wavefront 17 Nonlinear optical material member 27a, 27b Diffraction lenses 28a, 28b Glass prisms 31a, 31b, 31c, 31d Total reflection mirrors

Claims (8)

Based on the input control signal light, it comprises a light control type optical deflector that scans the incident serial optical signal train in a predetermined direction,
The light control type optical deflector incorporates a nonlinear optical material member whose transmittance or refractive index changes according to the irradiation intensity of light, and the nonlinear optical material member has interference with a spatial frequency according to the control signal light. A high-speed optical scanning device characterized in that fringes are formed and the spatial frequency of the interference fringes is changed to change the diffraction direction of the incident serial optical signal sequence to perform the scanning. A first light control type optical deflector that scans an incident serial optical signal string in a first direction based on the input control signal light; and
A condensing optical system for condensing the serial optical signal string scanned in the first direction;
Based on the input control signal light, which is arranged at a condensing position by the condensing optical system, the condensing serial optical signal string is scanned in a second direction different from the first direction. 2 light control type optical deflectors,
Each of the first light control type optical deflector and the second light control type optical deflector incorporates a nonlinear optical material member whose transmittance or refractive index changes according to the irradiation intensity of light. An interference fringe having a spatial frequency corresponding to the control signal light is formed on the member, and by changing the spatial frequency of the interference fringe, the diffraction direction of the incident serial optical signal train is changed, and the scanning is performed. A high-speed optical scanning device. The scanning drive timing of the first light control type optical deflector and the second light control type optical deflector is configured to synchronize with a predetermined timing of the serial optical signal sequence,
3. The high-speed optical scanning device according to claim 2, wherein a two-dimensional parallel optical signal is output from the second optical control type optical deflector. The control signal light is pulsed light;
A widening optical system for widening the pulsed light in a direction substantially orthogonal to the traveling direction of the pulsed light;
A delay time addition optical system that performs different time delay processing for each spatial position of the pulse light widened by the widening optical system;
4. A condensing optical system for condensing the pulse light subjected to time delay processing by the delay time adding optical system on the nonlinear optical material member. The high-speed optical scanning device according to item 1. In the time delay processing by the delay time adding optical system, the widened pulsed light is substantially symmetrical with respect to the central axis in a predetermined plane including the central axis of the light beam, and as the distance from the central axis increases. It is a process that transforms so that the amount of time delay gradually increases or decreases,
When the pulsed light focused on the nonlinear optical material member reaches the surface of the nonlinear optical material member, the crossing angle of the wave fronts of the light beams that are substantially symmetrical is gradually increased with time. Changed to increase or decrease,
5. The high-speed optical scanning device according to claim 4, wherein the nonlinear optical material member is configured such that interference fringes having a spatial frequency corresponding to the size of the intersection angle are formed.   6. The high-speed optical scanning device according to claim 4, wherein the delay time adding optical system performs time delay processing by a deflecting optical element.   7. The deflecting optical element includes a plurality of optical elements having lens characteristics, and is configured to change a delay time according to a light incident position on the optical element. High-speed optical scanning device.   The deflection optical element includes a prism optical element, and is configured to change a delay time in accordance with an optical path length in the prism optical element of light incident on the prism optical element. Item 7. The high-speed optical scanning device according to Item 6.

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