CN103869424B - Optically coupled device - Google Patents

Abstract

The invention provides an optical coupling device, which includes a substrate, a slab optical waveguide formed on the substrate, a dielectric grating formed on the slab optical waveguide, a dielectric grating arranged on the dielectric grating parallel to the dielectric grating The modulating electrode and two ground electrodes are arranged on the substrate parallel to the dielectric grating and are respectively located on two sides of the dielectric grating. The flat optical waveguide is used for docking with a laser light source to receive the laser beam emitted by the laser light source. The dielectric grating is arranged parallel to the incident direction of the laser beam, and forms a diffraction-type optical waveguide lens with the flat optical waveguide to converge the laser beam. A modulation electric field is loaded between the modulation electrode and the two ground electrodes to change the refractive index of the flat optical waveguide through the electro-optic effect, thereby changing the focal length of the diffractive optical waveguide lens. In this way, the laser beam can be efficiently converged into an optical element.

Description

Optical coupling device

technical field

The invention relates to an integrated optical device, in particular to an optical coupling device.

Background technique

In integrated optics, the coupling of the light source and optical components needs to be considered: although integrated optics generally uses lasers with better directionality as the light source, the beam emitted by the laser still has a certain divergence angle. If the light source and optical components are directly connected Butt, the divergent light in the beam will not be able to enter the optical element, and the light utilization rate is low. Therefore, how to couple the light source to the optical element so that the divergent light beam converges into the optical element to improve light utilization is an important issue.

Contents of the invention

In view of this, it is necessary to provide an optical coupling device that can improve light utilization.

An optical coupling device comprising a substrate, a flat optical waveguide formed on the substrate, a dielectric grating formed on the flat optical waveguide, a modulation electrode arranged on the dielectric grating parallel to the dielectric grating and Two ground electrodes are arranged on the substrate parallel to the dielectric grating and respectively located on two sides of the dielectric grating. The flat optical waveguide is used for docking with a laser light source to receive the laser beam emitted by the laser light source. The dielectric grating is arranged parallel to the incident direction of the laser beam, and forms a diffractive waveguide lens (diffractive waveguide lens) with the flat optical waveguide to converge the laser beam. A modulation electric field is loaded between the modulation electrode and the two ground electrodes to change the refractive index of the flat optical waveguide through the electro-optic effect, thereby changing the focal length of the diffractive optical waveguide lens.

According to the theory of integrated optics, the dielectric grating and the slab optical waveguide constitute a strip/grating loaded waveguide, and the equivalent refractive index of the portion of the slab optical waveguide loaded with the dielectric grating becomes larger. In this way, by setting the structure of the dielectric grating reasonably, for example, setting it as a chirped grating (chirped grating), a diffractive optical waveguide lens of chirped grating type can be formed. A modulation electric field is applied between the modulation electrode and the two ground electrodes to change the refractive index of the flat optical waveguide through the electro-optic effect, thereby changing the focal length of the diffractive optical waveguide lens and effectively converging the laser beam into the optical element.

Description of drawings

FIG. 1 is a schematic perspective view of an optical coupling device according to a preferred embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the optical coupling device of FIG. 1 along the line II-II.

FIG. 3 is a schematic plan view of a dielectric grating of the photocoupling device in FIG. 1 .

Description of main component symbols

Optocoupler 10

base 110

first top surface 111

first side 112

Planar optical waveguide 120

second top surface 121

second side 122

Dielectric Grating 130

third top surface 131

Media section 132

Modulating electrodes 141

Ground electrode 142

buffer layer 150

Laser light source 20

laser beam 21

Optics 30

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

detailed description

Please refer to FIG. 1 and FIG. 2, the optical coupling device 10 according to the preferred embodiment of the present invention includes a substrate 110, a slab optical waveguide 120 formed on the substrate 110, and a medium formed on the slab optical waveguide 120. The grating 130 , a modulating electrode 141 disposed on the dielectric grating 130 parallel to the dielectric grating 130 , and two ground electrodes 142 disposed on the substrate 110 parallel to the dielectric grating 130 and located on two sides of the dielectric grating 130 respectively. The flat optical waveguide 120 is used to connect with a laser light source 20 to receive the laser beam 21 emitted by the laser light source 20 . The dielectric grating 130 is arranged parallel to the incident direction of the laser beam 21 , and forms a diffractive optical waveguide lens with the slab optical waveguide 120 to converge the laser beam 21 . Between the modulation electrode 141 and the two ground electrodes 142 is used to load a modulation electric field By changing the refractive index of the flat optical waveguide 120 through the electro-optic effect, the focal length of the diffractive optical waveguide lens can be changed.

According to the theory of integrated optics, the dielectric grating 130 and the slab optical waveguide 120 constitute a loaded optical waveguide, and the equivalent refractive index of the portion of the slab optical waveguide 120 loaded with the dielectric grating 130 becomes larger. In this way, by setting the structure of the dielectric grating 130 reasonably, for example, setting it as a chirped grating, a diffractive optical waveguide lens of chirped grating type can be formed. And the modulation electric field is applied between the modulation electrode 141 and the two ground electrodes 142 Therefore, the refractive index of the planar optical waveguide 120 is changed by the electro-optical effect, thereby changing the focal length of the diffractive optical waveguide lens, and effectively converging the laser beam 21 into the optical element 30 (such as a strip optical waveguide). In addition, taking the height direction of the flat optical waveguide 120 as the x-axis, the width direction as the y-axis, and the depth direction (that is, the direction parallel to the dielectric grating 130) as the z-axis to establish a coordinate system, then the modulation electrode 141 and the two The ground electrode l42 is set in such a way that the modulated electric field The part passing through the laser beam 21 is substantially parallel to the x-axis direction, and according to the wave equation analysis of the slab optical waveguide, it can be seen that the transverse electric wave of the laser beam has only the electric field component Ey along the y-axis direction, and the transverse magnetic wave has only the electric field component Ey along the y-axis direction, while the transverse magnetic wave has only The electric field component Ex along the x-axis direction and the electric field component Ez along the z-axis direction, therefore, the modulation electric field It can effectively act on the transverse magnetic wave and modulate the transverse magnetic wave.

The base 110 is substantially rectangular and includes a first top surface 111 and a first side surface 112 connected to the first top surface 111 . Since lithium niobate (LiNbO ₃ ) crystal (LN) has a relatively high reaction speed, and considering that lithium niobate diffusion metal titanium (single substance) can form a loaded optical waveguide with graded refractive index, the material of the substrate 110 is Lithium niobate crystals.

The flat optical waveguide 120 is also rectangular, located on the first top surface 111, and includes a second top surface 121 opposite to the first top surface 111 and a second top surface 121 connected to the second top surface 121 and connected to the first top surface 111 One side 112 is coplanar with the second side 122 . The slab optical waveguide 120 is formed by diffusing metallic titanium (single substance) into lithium niobate. In this way, after the dielectric grating 130 is loaded, the refractive index of the slab optical waveguide 120 changes gradually, which is a favorable condition for producing a chirped grating type diffractive optical waveguide lens.

The dielectric grating 130 is located on the second top surface 121 and includes a third top surface 131 opposite to the second top surface 121 . The dielectric grating 130 is also made of lithium niobate diffused into metal titanium. The dielectric grating 130 may be a chirped grating. Specifically, the dielectric grating 130 includes a plurality of rectangular dielectric portions 132 arranged in parallel, the plurality of dielectric portions 132 are arranged perpendicular to the first side 112 and the second side 122 , and have substantially the same height. The number of the plurality of dielectric parts 132 is an odd number, and they are symmetrically distributed about a symmetry axis O, and along the symmetry axis O to a direction away from the symmetry axis O, the width of the dielectric parts 132 becomes smaller and smaller, while two adjacent The gap between each of the dielectric parts 132 is getting smaller and smaller.

Please refer to FIG. 3 , in this embodiment, the width direction of the dielectric grating 130 is the x-axis, the intersection point of the symmetry axis O and the x-axis is the origin, and the direction along the symmetry axis O to the direction away from the symmetry axis O is x In the positive direction of the axis, taking the phase difference between the laser beam 21 at x and the origin as the y-axis, according to the planar optical waveguide wave theory, it can be obtained: where x>0. The nth boundary x _n of the medium portion 132 satisfies the following conditions: Wherein, n is a positive integer, y _n =nπ (to constitute the diffractive optical waveguide lens), and a and k are constants related to the focal length of the diffractive optical waveguide lens. In this way, it can be deduced that: In the case of x<0, that is, the boundary of the medium portion 132 on the left side of the symmetry axis O can be obtained through symmetry.

The modulated electric field Crossing the slab optical waveguide 120, so that the equivalent refractive index of the slab optical waveguide 120 can be further changed, and the refractive power (that is, the focal length) of the diffractive optical waveguide lens of the chirped grating type can be changed equivalently, so that it can be coupled with each The laser light source 10 and the optical element 30 are arranged at various distances. The lengths of the modulation electrode 141 and the two ground electrodes 142 are greater than or equal to the length of the dielectric grating 130. In this embodiment, the lengths of the modulation electrode 141 and the two ground electrodes 142 are equal to the length of the dielectric grating 130 and high. In addition, the width of the modulation electrode 141 is slightly smaller than or equal to the width of the dielectric grating 130 . The height of the two ground electrodes 142 is smaller than the height of the flat optical waveguide 120 , so that the electric field part passing through the laser beam 21 can be more parallel to the x-axis direction.

Preferably, in order to prevent light waves from being absorbed by the modulation electrode 141 and the two ground electrodes 142, a buffer layer may be formed on the dielectric grating 130 and the substrate 110 and between the modulation electrode 141 and the two ground electrodes 142. Layer 150. The buffer layer 150 is made of silicon dioxide.

When making the optical coupling device 10, a lithium niobate blank (not shown) including the third top surface 131 is firstly provided, and the third top surface 131 is plated with metal titanium (single substance) and then diffused into the metal titanium at high temperature. The lithium niobate blank is used to form the lithium niobate part diffused with metal titanium for making the planar optical waveguide 120 and the dielectric grating 130, and the part of lithium niobate not diffused with metal titanium is the substrate 110, and then The third top surface 131 is etched to the flat optical waveguide 120 (ie the second top surface 121) to form the dielectric grating 130 and the parts on both sides of the dielectric grating 130 are etched to the substrate 110 (the first top surface 111 ) to form the planar optical waveguide 120. Then, the buffer layer 150 , the modulation electrode 141 and the two ground electrodes 142 are plated on the dielectric grating 130 and the substrate 110 at positions corresponding to the modulation electrode 141 and the two ground electrodes 142 .

In a word, those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention, as long as within the spirit of the present invention, the above examples Appropriate changes and changes all fall within the scope of protection of the present invention.

Claims (12)

1. a kind of optically coupled device, it include a substrate, planar light waveguide being formed in the substrate, one be formed at Dielectric grating on the planar light waveguide, one the medium light is arranged on the dielectric grating and covered parallel to the dielectric grating The modulator electrode of grid and two ground for being arranged in the substrate parallel to the dielectric grating and being located at the dielectric grating both sides respectively Electrode；The planar light waveguide is used to dock to receive the laser beam that the LASER Light Source sends with a LASER Light Source；The medium light Grid are set along the incident direction parallel to the laser beam, and constitute a diffraction type optical waveguide lens with meeting with the planar light waveguide Gather the laser beam；It is used for load-modulate electric field between the modulator electrode and two ground electrodes and is put down with changing this by electrooptic effect The refractive index of plate fiber waveguide is so as to change the focal length of the diffraction type optical waveguide lens.

2. optically coupled device as claimed in claim 1, it is characterised in that the substrate is made of lithium columbate crystal.

3. optically coupled device as claimed in claim 1, it is characterised in that the planar light waveguide diffuses into metal in lithium niobate Titanium simple substance and formed.

4. optically coupled device as claimed in claim 1, it is characterised in that the dielectric grating diffuses into Titanium in lithium niobate Simple substance and formed.

5. optically coupled device as claimed in claim 1, it is characterised in that the substrate is rectangular, and including first top surface And a first side being connected with first top surface；The planar light waveguide is rectangular, on first top surface, and including one Individual second top surface opposite with first top surface and one are connected and second side coplanar with the first side with second top surface Face；The dielectric grating is arranged on second top surface, and including threeth top surface opposite with second top surface；The optocoupler Attach together and put by including that the 3rd top surface of the 3rd top surface lithium niobate blank plates Titanium simple substance and then high temperature will at one Titanium diffuses into the lithium niobate blank and be diffused with Titanium for make the planar light waveguide and the dielectric grating being formed Lithium niobate part, then the lithium niobate part as substrate without being diffused with Titanium be etched on the 3rd top surface Second top surface with formed the dielectric grating and the part of the dielectric grating both sides be etched to first top surface of the substrate with Form the planar light waveguide.

6. optically coupled device as claimed in claim 5, it is characterised in that the dielectric grating is a chirp grating.

7. optically coupled device as claimed in claim 6, it is characterised in that the dielectric grating includes multiple rectangles, parallel setting The media fraction put, the plurality of media fraction is set perpendicular to the first side and the second side, and highly essentially identical；Should The number of multiple media fractions is odd number, and symmetrical on a symmetry axis, and along the symmetry axis to away from the symmetry axis Direction, the width of the media fraction is less and less, and the gap of the two neighboring media fraction is also less and less.

8. optically coupled device as claimed in claim 7, it is characterised in that the width with the dielectric grating as x-axis, this pair Axle is called origin with the joining of x-axis, along the symmetry axis to the direction away from the symmetry axis for x-axis is positive, the media fraction N-th border x_nMeet following condition：Wherein, x_n＞ 0, n are positive integer, a and k be constant and with this The focal length of diffraction type optical waveguide lens is related.

9. optically coupled device as claimed in claim 1, it is characterised in that the modulator electrode is big with the length of two ground electrodes In or equal to the dielectric grating length.

10. optically coupled device as claimed in claim 1, it is characterised in that two height of ground electrode are less than the flat board light The height of waveguide.

11. optically coupled devices as claimed in claim 1, it is characterised in that the optically coupled device is also arranged at this including one Cushion between dielectric grating and the substrate and the modulator electrode and two ground electrodes, for preventing light wave by modulation electricity Two ground electrodes in pole and this are absorbed.

12. optically coupled devices as claimed in claim 11, it is characterised in that the cushion is made of silica.