JPH08220497A - Optical switch and optical scanner using the same - Google Patents

Abstract

PURPOSE: To provide an optical scanner enabling low-voltage driving at high speed and having high reliability. CONSTITUTION: A switching element is constituted by arraying a polarizing surface rotary element D1 having a function rotating the polarizing surface of the light wave of a TE mode or a TM mode by an electrooptic effect obtained by forming a pair of electrodes 4 along the advancing direction of light on an optical waveguide 2 formed on a substrate 1 and having an electrooptic function and impressing voltage between the electrodes and a polarizer D2 provided with a clad layer absorbing the light wave of a mode obtained by a rotation out of the light wave of the TE mode or the TM mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch and an optical scanning device using the same, and more particularly to an optical scanning device used for laser printers, digital copying machines, laser displays and the like.

[0002]

2. Description of the Related Art Conventionally, a device for scanning light (optical deflector)
Known polygon mirrors, galvano mirrors, and the like. These are now widely spread and applied to laser printers and the like. In the mechanically controlled optical polarizer, the natural rotation speed of the vibrating element is about 2.5 kHz, and if the polygon mirror is an octahedron, the polarization speed is several tens kHz. However, stable operation is possible in a wide angle, high speed is achieved by using a divided laser beam, and 256 gradations are realized by electrical control.

Electro-optical control and acousto-optical control are conceivable as a method for further increasing the speed, but as shown in the current laser engineering (co-authored by Takashi Azagami et al., Ohmsha), particularly electro-optical control. The deflection speed of the optical deflector by the control and the acousto-optical control can both be operated at a high speed in principle as compared with the mechanical control.

Moreover, the acousto-optic optical polarizer has several 100M.
While the polarization rate of Hz can be obtained, the electro-optical optical polarizer is expected to have the highest polarization rate of several tens GHz. Therefore, the electro-optical light deflector is most promising when the deflection speed is increased.

On the other hand, when the light propagating in the single mode fiber is incident on the waveguide type device for optical signal processing, the incident light wave is generally elliptically polarized.
The active element in the waveguide type device is z perpendicular to the waveguide plane.
When the axis is taken, the electric field vector is TE in the xy plane.
It operates only for polarized light of either mode or TM mode in which the magnetic field vector is in the xy plane. Therefore, it becomes necessary to select either polarized light or separate the TE or TM propagation path. At this time,
A metal clad or a mode splitter is used as a waveguide polarizer (optical integrated circuit: Hiroshi Nishihara, Masamitsu Haruna, Toshiaki Suhara, Ohmsha)

[0006]

However, the electro-optical light deflector has a small deflection angle, and the number of resolution points (a value obtained by dividing the deflection angle by the beam spread) indicating the performance of the light deflector is several points. There is a problem of being small and small. Further, analog light deflection by electro-optical control requires a high voltage.

[0007] Among these problems, with respect to the driving voltage, a technique has been proposed in which the driving voltage is suppressed to a low level by forming a waveguide, and this can be solved. However, the problem that the deflection angle is small and the problem that the number of resolution points is small have not been found yet.

The present invention has been made in view of the above circumstances, and solves the problems of the deflection angle and the number of resolution points, enables high-speed low-voltage driving, and has high reliability. The purpose is to provide a device.

[0009]

The first feature of the present invention is to:
A light-transmissive substrate, an optical waveguide having an electro-optical function formed on the substrate, and a pair of electrodes formed on the optical waveguide along the traveling direction of light, and between the pair of electrodes. By applying a voltage to the
A polarization plane rotating element having a function of rotating a polarization plane of an E-mode or TM-mode light wave, and a cladding layer formed behind the polarization plane rotating element so as to cover the optical waveguide. An optical switch having a polarizer that absorbs one of the mode or TM mode light waves.

A second feature of the present invention is to provide an optical scanning device by arranging a plurality of the switches and providing a light source for supplying light to each optical waveguide of the switch. That is, a second aspect of the present invention is to provide a translucent substrate, a plurality of optical waveguides having an electro-optical function formed on the substrate, and a pair of optical waveguides formed on the optical waveguide along a light traveling direction. A plurality of polarization plane rotating elements each having an electrode and having a function of rotating a polarization plane of a TE-mode or TM-mode light wave by an electro-optical effect by applying a voltage between the pair of electrodes; A plurality of polarizers formed of a clad layer formed behind the rotating element so as to cover the optical waveguide, and absorb the light waves of the mode obtained by the rotation among the TE-mode or TM-mode light waves. Of the TE-mode or TM-mode light wave, which is obtained by the rotation or is not rotated. In the optical scanning apparatus characterized by comprising a polarizer which absorbs one of the modes of the light wave mode.

A third feature of the present invention is that a waveguide lens is provided between the polarization plane rotating element of the optical scanning device and the light source, and the light from the light source is spread and branched into each channel. This is because the input is made to the polarization plane rotating element.

A fourth feature of the present invention is that a beam expander and a waveguide lens are arranged on the optical waveguide after passing through the polarization plane rotating element and the polarizer, or the polarization plane rotating element and the polarizer are arranged. A waveguide lens is provided on the optical waveguide prior to incidence on the optical waveguide.

The fifth feature of the present invention is that all these elements are integrated.

[0014]

The function of rotating the plane of polarization is a phenomenon in which the plane of polarization rotates because the main axis rotates when a voltage is applied to the crystal. First, a TE mode light wave is introduced into an optical waveguide having a wide channel width. As shown in FIG. 1, TE-mode light incident parallel to the crystal's dielectric main axis is transmitted from the opposite surface unless a voltage is applied to the pair of electrodes 4 formed at both ends in the width direction of the channel 2. It is emitted in the mode. When a voltage is applied, the dielectric main axis of the electro-optic crystal tilts. For this reason, the plane of polarization rotates and, after passing a certain length, is converted to the TM mode. As a result, the waveguide light can generate two kinds of modes, the TE mode or the TM mode, in the portion where the voltage is not applied. When this waveguide light is passed through a waveguide type polarizer typified by a metal clad or an anisotropic crystal clad, the TM mode is absorbed, and T
It can pass E mode and acts as a switch.

According to the second aspect of the present invention, an optical scanning device can be obtained by arranging a plurality of these switches. As shown in FIG. 2, by arranging the above-mentioned switches on the optical waveguide 2 having a wide channel width, an optical scanning device can be manufactured. The incident light may be TE mode or TM mode. In this case, the relationship between the TE mode and the TM mode is reversed. When a large number of these optical switch elements are arranged in parallel, they have fine dots.
The print pattern of the line can be obtained. If the polarization plane rotating element portion is about 70 mm, low voltage driving of 3 V is possible. In addition to the digital pattern of 0 and 1, the rotation speed of the polarization plane in the polarization plane rotating element portion can be changed by changing the applied voltage. As a result, the direction cosine to the TE mode component of the plane of polarization changes depending on the applied voltage. Thereby, intensity modulation can be performed, and gradation can be controlled when used as a printer, for example.

Further, according to a third aspect of the present invention, a waveguide lens is provided between the polarization plane rotating element of the optical scanning device and the light source, and the light from the light source is spread and branched into each channel. By making it possible to input to the polarization plane rotation element,
The beam can be expanded and the scan width can be increased.

Further, according to the fourth aspect of the present invention, the beam can be expanded by further arranging the beam expander and the waveguide lens on the optical waveguide after passing through the polarization plane rotating element and the polarizer. The width can be increased.

According to the fifth aspect of the present invention, it is possible to obtain an extremely small and highly reliable optical scanning device by integrating all these elements including the light source.

A two-dimensional optical scanning device can be obtained by installing the micro movable mirror on the same substrate. Further, since the phase shift modulation and the intensity modulation can be performed, it is possible to create a three-dimensional suspension.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 3 is a diagram showing an optical scanning device according to an embodiment of the present invention, and FIG. 4 is a sectional view thereof.

This optical scanning device uses a LiNbO ₃ substrate 1 which is a translucent electro-optical crystal as a substrate, and spreads light from a semiconductor laser 100 as a light source with an EO waveguide 200 composed of an expander and a collimating lens. Further, it was formed by diffusing titanium on the surface of this LiNbO ₃ substrate 1 by a thermal diffusion method, depth 1.2 μm, width 5
Channel waveguide 2 (2
a, 2b, 2c, 2d), a buffer layer 3 formed on this surface by a thin film having a thickness of 100 nm and made of a glass material called Corning 7059 (hereinafter referred to as glass material), and the buffer layer 3. 3 a polarization rotator D1 consisting of four pairs of aluminum electrodes 4 arranged in an array on the surface, and an aluminum clad layer 5 disposed behind the polarization rotator to cover the channel waveguide.
And a polarizer D2 composed of Here, the light source is configured to directly enter the channel waveguides 2 with TE mode semiconductor laser array light.

In this device, as shown by the solid line in FIG.
When no voltage is applied to each aluminum electrode 4, L
The laser light incident on the iNbO ₃ substrate 1 proceeds along the waveguide 2 as it is.

On the other hand, when a voltage is applied to the aluminum electrode 4, the polarization plane of that portion rotates and passes through the electrode, and then is converted to the TM mode (dotted line). Then, when the buffer layer disappears and the region is covered with the aluminum clad layer 5, the TM mode is absorbed here, and a dot pattern corresponding to the number of channels on the line of the channel waveguide can be obtained. That is, when a voltage is applied, it is turned off, and printing is not performed in the arrayed state. The optical scanning device thus created can scan the laser beam in the scanning range R on the paper surface as shown in FIG. Further, when the photosensitive drum is scanned, it can be used as a laser printer.

Next, a second embodiment of the present invention will be described.

FIG. 6 is a diagram showing an optical scanning device according to an embodiment of the present invention, and FIG. 7 is a sectional view of FIG.

In the first embodiment, the polarization rotation element D1
The pair of electrodes are arranged on the waveguide, that is, in parallel with the substrate surface, and the voltage is applied in parallel with the substrate surface. In this example, the electrodes are arranged in the direction perpendicular to the substrate surface. It is characterized in that a voltage is applied perpendicularly to the substrate surface.

That is, the optical scanning device includes a semiconductor laser 100 as a light source, an EO waveguide 200 having a beam expander and a collimating lens configured to spread the light from the semiconductor laser 100, and E
A polarization rotator D1 that rotates the polarization plane of the TE mode or TM mode light wave by the electro-optical effect of the light transmitted through the O waveguide 200 by turning on and off the voltage to the electrode, and this polarization rotation. Behind the element, a polarizer D2 for absorbing the light wave of the mode obtained by the rotation
And a branched waveguide 300 including a beam expander and an fθ lens. The actual element structure is, as shown in the sectional view of FIG. 7, a stripe-shaped first electrode 14 formed on the surface of a translucent glass substrate 11 made of a glass material, and a film formed on this upper layer. Thickness 100
buffer layer 15 made of a glass material thin film having a thickness of nm, a waveguide 16 made of a C-axis oriented ZnO thin film formed on the upper layer, and a film thickness of 100 nm selectively formed at a predetermined position on the upper layer. A buffer layer 17 formed of a thin film of a glass material, a second electrode 18 formed on the buffer layer 17, and niobium oxide (Nb oxide) formed so as to be located on the waveguide behind the second electrode. ₂ O ₃ ) and an absorption thin film 19 made of a thin film. The thickness of the C-axis oriented ZnO thin film forming the waveguide 16 is adjusted for each region so as to form a beam expander, a collimator lens and an fθ lens.

Next, a method of manufacturing this optical scanning device will be described. First, a glass material is used as a substrate, a gold layer is formed on this surface by a sputtering method, and patterned by a photolithography method to have a thickness of 1.2 μm.
The first electrode 1 is formed into a stripe shape with a width of 10 μm.
4 is formed. This stripe corresponds to each waveguide.
Then, a thin film of a glass material is formed on this upper layer by a sputtering method to form a buffer layer 15, and a ZnO thin film is further formed by a sputtering method, and then C
The waveguide 16 made of a C-axis oriented ZnO thin film is formed by annealing using an O ₂ laser. Further, the film thickness of this ZnO thin film is adjusted in its corresponding region so as to form a beam expander, a collimator lens and an fθ lens. Furthermore, here, Zn with C-axis orientation
Although the O thin film and the buffer layer are formed on the entire surface, the stripe is defined by the first electrode 14 to define the waveguide.

After that, a thin film of a glass material is further formed on the upper layer by a sputtering method and is patterned by photolithography to selectively form the buffer layer 17 only in the region corresponding to the polarization rotation element D1.

Further, an aluminum layer is formed by vapor deposition and an electrode pattern is formed by photolithography to obtain the second electrode 18. Then, an absorption thin film 19 made of a niobium oxide (Nb ₂ O ₃ ) thin film is formed by a sputtering method, and the absorption thin film 19 is patterned by photolithography. Finally, the end face of the substrate is polished.

In this way, the optical scanning device shown in FIGS. 6 and 7 is formed. Next, the operating principle of this optical scanning device will be described. As shown in FIG. 7, the light emitted from the TE mode light source 100 is directly incident on the waveguide, the laser beam is expanded through the waveguide lens, and the laser beam is collimated when the laser beam is expanded according to the element size. It is collimated by a lens and introduced into a branched channel waveguide, that is, a stripe region portion by the first electrode pattern. Then, when a voltage is applied between the first electrode 14 and the second electrode 18 via the buffer layers 15 and 17, the polarization plane of that portion rotates and passes through the inter-electrode region, and then the TM mode (dotted line) Is converted to.
On the other hand, if no voltage is applied, TE mode (solid line)
Continue as it is.

When the buffer layer is removed and the region is covered with the absorption thin film 19 made of niobium oxide, the TM mode leaks from the waveguide due to crystal anisotropy. After this, in order to clarify the separation between the elements, the radiation angle is expanded through the beam expander, and f / θ is further increased.
Focus through the lens. In this way, as shown in FIG. 8, the laser beam can be scanned in the scanning range R via the mirror 400 on the paper surface. Further, when the photosensitive drum is scanned, it can be used as a laser printer.

Next, a third embodiment of the present invention will be described.

FIG. 9 is a diagram showing an optical scanning device according to an embodiment of the present invention, and FIG. 10 is a sectional view of FIG. In the second embodiment, the waveguide is composed of a C-axis oriented ZnO thin film, but instead of this, in this embodiment, a MNA (2-methyl-4nitroaniline) thin film 26 which is a crystalline thin film having an EO effect is used. Is used. This MNA thin film is an organic thin film formed by a melt method or a vapor phase method. In the second embodiment, the EO waveguide provided with the beam expander and the collimating lens is used. However, here, the EO waveguide 200 'for transmitting the laser light as it is is used, and the deflection rotation element D1 is used. The laser beam spreads to the position. In the second embodiment, TM
A beam expander and an f.theta. Lens are provided behind the polarizer D2 that absorbs modes, but a waveguide lens 500 is provided here. The other parts are formed similarly to the second embodiment.

The operating principle of this optical scanning device is the same as that of the above-mentioned embodiment, but the light emitted from the TE mode light source 100 is directly incident on the waveguide, and the branched channel waveguide, that is, the first waveguide. It is introduced in the stripe region portion by the electrode pattern. Then, when a voltage is applied between the first electrode 14 and the second electrode 18 via the buffer layers 15 and 17, the polarization plane of that portion rotates and passes through the inter-electrode region, and then the TM mode (dotted line) Is converted to.
On the other hand, if no voltage is applied, TE mode (solid line)
Continue as it is.

When the buffer layer disappears and the region is covered with the absorption thin film 19 made of niobium oxide, the TM mode leaks from the waveguide due to crystal anisotropy. In this way, only TE mode light is transmitted and emitted from the end face of the substrate.

Next, a fourth embodiment of the present invention will be described.

FIG. 11 is a sectional view showing an optical scanning device according to an embodiment of the present invention, and FIG. 12 is a perspective view. In this example, all elements including a light source are two-dimensionally integrated. In this example, a GaAs substrate 31 is used, and GaIn is formed on this surface.
The P-type semiconductor laser 600 and the first waveguide lens 70
0, a polarization rotation element D1, a polarizer D2 for removing the TM mode, a second waveguide lens 800, a grating 900 for output and a mirror M are arranged along the optical transmission path. It is characterized by
The P layer is used as an EO waveguide.

Here, the semiconductor laser is composed of AlInP as a clad layer laminated on the surface of the GaAs substrate 31 by the MOCVD method.
The layer 32, the GaInP layer 33 as the active layer, the AlInP layer 34 as the cladding layer, and the electrodes 35a and 35b formed on the front and back surfaces are configured to emit light toward the waveguide. There is. In a region other than the region of the semiconductor laser, a GaP layer 36 is formed on the AlInP layer 32 and light is transmitted through this layer. First waveguide lens 700
Is composed of a grating pattern formed to have a desired thickness and shape by interferometry using an argon laser.

Then, the polarization rotation element D1 uses the GaP layer 36 as a waveguide and forms a pair on the same plane via the buffer layer 27 made of a glass layer as in the first embodiment. The electrode 24 is formed of a gold layer.

The polarizer D2 is constructed by using the GaP layer 36 as a waveguide and directly covering the waveguide with the electrode 25 made of a gold layer.

As for the second waveguide lens and the output grating 900, the GaP layer 36 is made to have a desired thickness and shape by the interferometry using an argon laser as in the first waveguide lens. It is composed of a grating pattern formed on.

Further, the mirror M is composed of a thin film formed by the micromachining method, and is structured so that the output direction is movable by resonance.

Next, the operating principle of this optical scanning device will be described. As shown in FIG. 11, the TM mode light emitted from the semiconductor laser 600 spreads along the waveguide formed of the GaInP layer, and the laser beam is further spread through the waveguide lens, and when the spread becomes according to the element size, The laser beam is collimated by a collimating lens and introduced into a branched GaP channel waveguide.
Then, when a voltage is applied to the electrode 24, the plane of polarization is rotated by the EO effect to enter the TE mode. On the other hand, if no voltage is applied, the process proceeds in the TM mode (solid line).

When the buffer layer disappears and the region is covered with the absorption thin film composed of the gold electrode 25, the TM mode leaks from the waveguide due to the crystal anisotropy, so that no light is emitted. The TE-mode light generated by applying the voltage is then further expanded by the second waveguide lens and emitted from the substrate by grading, and the movable mirror M resonating causes the beam to move upward and downward as shown in FIG. Is vibrated, and two-dimensional optical scanning is achieved.

[0046]

As described above, according to the present invention, it is possible to provide an optical scanning device which can be driven at high speed and low voltage and which is effective for a laser printer, a digital copying machine, a laser display and the like. Become.

[Brief description of drawings]

FIG. 1 is a principle explanatory view showing an optical scanning device of the present invention.

FIG. 2 is an explanatory view of the principle of the optical scanning device of the present invention.

FIG. 3 is a diagram showing an optical scanning device according to a first embodiment of the present invention.

FIG. 4 is a sectional view of the optical scanning device.

FIG. 5 is a diagram showing a scanning example of the optical scanning device.

FIG. 6 is a diagram showing an optical scanning device according to a second embodiment of the present invention.

FIG. 7 is a sectional view of the optical scanning device.

FIG. 8 is a diagram showing a scanning example of the optical scanning device.

FIG. 9 is a diagram showing an optical scanning device according to a third embodiment of the present invention.

FIG. 10 is a sectional view of the optical scanning device.

FIG. 11 is a diagram showing an optical scanning device according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view of the optical scanning device.

FIG. 13 is a diagram showing a scanning example of the optical scanning device.

[Explanation of symbols]

100 Semiconductor Laser 200 EO Waveguide 300 Branch Waveguide 1 LiNbO ₃ Substrate 2 Channel Waveguide 3 Buffer Layer 4 Aluminum Electrode 5 Aluminum Clad Layer D1 Polarization Rotating Element D2 Polarizer 11 Glass Substrate 14 First Electrode 15 Buffer Layer 16 Conductor Waveguide 17 Buffer layer 18 Second electrode 19 Absorption thin film 24 Electrode 25 Electrode 26 MNA thin film 32 AlInP layer (cladding layer) 33 GaInP layer (active layer) 34 AlInP layer (cladding layer) 35a, 35b Electrodes 35a, 35b 36 GaP layer

Claims (5)

[Claims] 1. A translucent substrate, an optical waveguide having an electro-optical function formed on the substrate, and a pair of electrodes formed on the optical waveguide in a light traveling direction, By applying a voltage between the pair of electrodes, the TE mode or T
A polarization plane rotation element having a function of rotating the polarization plane of the M-mode light wave, and a cladding layer formed behind the polarization plane rotation element so as to cover the optical waveguide. An optical switch comprising: a polarizer that absorbs one of the mode light waves. 2. A transparent substrate, a plurality of optical waveguides having an electro-optical function formed on the substrate, and a pair of electrodes formed on each of the optical waveguides along the light traveling direction. A plurality of polarization plane rotating elements having a function of rotating the polarization plane of the TE mode or TM mode light wave by an electro-optical effect by applying a voltage between the pair of electrodes; A plurality of polarizers configured to cover one side of the TE mode or TM mode light waves, the polarizer being formed behind the optical waveguide and covering the optical waveguide. A polarizer for absorbing a light wave of a mode obtained by the rotation among the TE-mode or TM-mode light waves, which is composed of a clad layer covering the optical waveguide. Optical scanning device. 3. A waveguide lens is provided between the polarization plane rotating element and the light source so that the light from the light source is spread and branched into each channel to be input to each polarization plane rotating element. The optical scanning device according to claim 2, which is characterized in that. 4. The optical scanning device according to claim 2, further comprising a beam expander and a waveguide lens, which are disposed in front of the polarization plane rotating element and the polarizer and are disposed on the optical waveguide. apparatus. 5. The optical scanning according to claim 2, wherein the light source, the polarization plane rotating element, the polarizer and the waveguide lens are integrated on the surface of the substrate. apparatus.