KR20050005358A - Optical module with planar lightwave circuit structure - Google Patents

Abstract

PURPOSE: An optical module having a planar light waveguide structure is provided to easily align a semiconductor laser and an optical axis. CONSTITUTION: An optical module having a planar light waveguide structure includes a substrate(210), an optical source(220), and a waveguide element(230). The optical source is mounted on the substrate and outputs a light having a predetermined wavelength. The waveguide element is formed on the substrate such that an end thereof faces the optical source. The waveguide includes a core(231) transmitting the light from the optical source and a clad(232) enclosing the core. The waveguide element has a bilayer structure having a first layer enclosing the clad and the core to condensing the light incident on the clad to the core and a second layer enclosing the first layer and having a diffraction ratio lower than that of the first layer. A long period lattice for guiding the optical signal incident on the clad to an inner portion thereof is formed on the core.

Description

OPTICAL MODULE WITH PLANAR LIGHTWAVE CIRCUIT STRUCTURE}

The present invention relates to an optical module in the form of a planar waveguide, and more particularly, to a heterogeneous integrated optical module including an active element and cores.

In the conventional planar optical waveguide device, cores and clads are sequentially stacked on an upper surface of a substrate, and various types of waveguides are formed on the core, thereby passive devices such as an arrayed waveguide grating, an optical coupler, etc. Form. In addition, by integrating active devices such as a photodiode or a semiconductor laser that outputs an optical signal together with the above-described passive devices on the substrate upper surface of the planar optical waveguide device, optical Various types of optical modules capable of transmitting and receiving, amplifying, and the like may be configured.

However, the heterogeneous integrated optical module described above has a problem that loss of an optical signal is caused due to improper optical coupling between an active element and a passive element. That is, there is a problem in that the loss of the optical signal is increased when the optical coupling between the active element and the passive element is incorrect.

1 is a side cross-sectional view showing an optical module including a lens seated between a conventional light source and a planar optical waveguide element as light coupling means. Referring to FIG. 1, a conventional optical module includes a light source 120, a planar optical waveguide device 130, a lens 140, and a substrate 110 on which components of the optical module are mounted or supported. As the light source 120, a semiconductor laser or the like may be used.

The planar optical waveguide device 130 is formed of a clad 132 stacked on and under the core 131 on the top surface of the substrate 110, and forms a waveguide on the core 131. A function as a passive element such as dividing an optical signal input therein can be performed.

The substrate 110 is provided with a groove for mounting the lens 140, and the light source 120 is heterogeneously integrated so as to face one end of the planar optical waveguide device 130 formed on an upper surface thereof.

The above-described optical module includes the lens 140 between the light source 120 and the planar optical waveguide device 130 to inject light output from the light source 120 into the planar optical waveguide device with high coupling efficiency. By inserting in, high bonding efficiency is obtained.

As another means for improving the coupling efficiency between the waveguide and the active element of the planar optical waveguide device as described above, conventionally forms a lens having a predetermined curvature at one end of the planar optical waveguide device facing the active element, By forming a long-period grating on the waveguide, a configuration of an optical module for coupling the optical signal incident to the cladding into the inside of the waveguide has been proposed. In addition, the conventional optical module has a semiconductor laser having a limited spot size. By using the light source as a light source, an optical module structure has been proposed which limits the divergence angle of light output from the light source and thereby improves the light coupling efficiency.

However, there is a problem in that alignment and integration of the lens are not easy by inserting the coupling lens to improve the coupling efficiency between the conventional semiconductor laser and the waveguide, thereby increasing the process delay and the production cost. In addition, an optical module using a semiconductor laser having a spot size limited according to another conventional embodiment also has a problem in that it is difficult to manufacture a semiconductor laser having a limited spot size, and a unit cost is high, and a semiconductor laser having a limited spot size There is a problem that a high precision is required for the integration and alignment of the.

In order to solve the above problems, an object of the present invention is to provide a heterogeneous integrated planar waveguide type optical module that is easy to manufacture, can reduce the production cost and excellent coupling efficiency.

In order to achieve the above object, an optical module in the form of a planar waveguide according to the present invention,

A substrate;

A light source mounted on the substrate and outputting light having a predetermined wavelength;

An end of which is formed on an upper surface of the substrate so as to face the light source, the waveguide device comprising a core, which is a medium for transmitting light output from the light source, and a cladding surrounding the core;

The waveguide device has a first layer surrounding the core and having a lower index of refraction than the first layer surrounding the core to couple unbonded light incident to the clad with the core. It is formed to have a double structure including a second layer, and a long-period grating for injecting an uncoupled optical signal incident to the clad into the core is formed in the core.

1 is a side cross-sectional view showing an optical module in which a planar waveguide device and a light source are integrated according to the prior art;

2 is a side cross-sectional view showing an optical module in which a waveguide device and a light source are integrated, including a cladding layer composed of first and second layers according to a first embodiment of the present invention;

3 is a perspective view illustrating a waveguide device including a plurality of cores and an optical module in which a plurality of light sources are integrated, according to a second embodiment of the present invention;

4 is a cross-sectional view of the optical module shown in FIG. 3 along AA ′;

FIG. 5 is a cross-sectional view of the optical module shown in FIG. 3 taken along line BB '; FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

FIG. 2 is a cross-sectional view illustrating a side surface of an optical module in which a waveguide device and a light source including a cladding of first and second layers according to a first embodiment of the present invention are integrated. 2, the optical module according to the first embodiment of the present invention includes a substrate 210 on which a light source is mounted, a light source 220 for outputting light having a predetermined wavelength, and an upper surface of the substrate 210. And a waveguide device 230 in which a core 231, which is a medium for transmitting light output from the light source 220, and a clad 232 surrounding the core 231 are stacked.

The waveguide element 230 is formed on an upper surface of the substrate 210 so that one end thereof faces the light source 220, and the core 231 and the core, which is a medium for transmitting the light output from the light source 220, are provided. It consists of a clad 232 surrounding 231.

The waveguide device 230 includes a first layer in which the clad 232 surrounds the core 231 to couple uncoupled light incident to the clad 232 to the core 231, and the first layer. A long-period grating formed to have a double structure including a second layer surrounding a first layer and having a lower refractive index value than the first layer, and for injecting an uncoupled optical signal incident to the clad 232 therein. Is formed in the core 231.

The clad 232 is formed to have a dual structure of the first layer 232a and the second layer 232b having different refractive indices, so that an uncoupled optical signal incident into the first layer 232a is received. Do not leave the first layer 232a. In addition, the first layer 232a has a lower refractive index than the core 231, so that the uncoupled optical signal input therein can be easily coupled to the core 231.

The core 231 has a long-period grating 213a for coupling the uncoupled optical signal incident to the first layer 232a of the clad 232 into the core 231 to the light source 220. It is formed at an opposite end, and has a refractive index lower than that of the first layer 232a of the clad 232.

The relationship between the period of the long period grating 213a and the effective refractive index between the core 231 and the first layer 232a may be expressed by Equation 2 below.

? Denotes the wavelength of the optical signal, n _co denotes the effective refractive index of the core, n _cl denotes the effective refractive index of the first layer, and Λ denotes the long period lattice period, respectively.

The clad 232 is configured to have a refractive index difference between the first layer 232a and the second layer 232b to prevent the unbound optical signal incident therein from leaking out.

That is, the non-coupled optical signal described above is coupled into the core 231 by the long period grating 231a of the core 231. In addition, the clad 232 includes the first layer 232a and the second layer 232b having a dual structure formed to have different refractive indices, and thus unbonded light beams incident into the first layer 232a. By preventing the arc from being emitted to the outside through the second layer 232b, the coupling efficiency of the uncoupled optical signal coupled to the core is further improved. The refractive index of the core 231 has a larger value than the first layer 232a based on the refractive index of the first layer 232a, and the refractive index 232b of the second layer is the first layer 232a. It has a value smaller than the refractive index of).

3 is a perspective view illustrating a planar waveguide device including a plurality of cores and an optical module in which a plurality of light sources are integrated, and FIG. 4 is an A-A optical module illustrated in FIG. 2. 5 is a cross-sectional view illustrating the optical module shown in FIG. 2 along B-B '.

3 to 5, an optical module according to a second embodiment of the present invention may include a waveguide element 320, which is a transmission medium of an optical signal formed on an upper surface of a substrate 310, and an upper surface of the substrate 310. And a plurality of light sources 330 seated opposite one end of the core 321.

The waveguide device 320 has a structure in which the clad 322 is sequentially stacked below and on the cores 321 formed on the upper surface of the substrate 310. It serves as a signal transmission.

Each core 321 has a long period grating 321a having a predetermined period at one end thereof to couple therein an uncoupled optical signal incident on the first layer 322a of the clad 322 therein. .

The clad 322 includes a first layer 322a surrounding each of the cores 321 at one end of the clad 322 facing the light source 330, and a first layer 322a surrounding the first layer 322a. The second layer 322b having a lower refractive index value than the double layer structure is formed. The uncoupled optical signal incident on the first layer 322a is not coupled to the core 321 by preventing the uncoupled optical signal from leaving the inside thereof. Improve the coupling efficiency of the optical signal.

The light sources 330 are seated on the upper surface of the substrate 310 so as to face one end of each core 321, and may use a semiconductor laser or the like.

That is, the clad 322 is formed of a double structure of the first and second layers 322a and 322b having different refractive indices so that an uncoupled optical signal incident on the first layer 322a is transmitted to the clad 322. To prevent leakage to the outside. As a result, the uncoupled optical signal input into the first layer 322a is coupled into the core 321 through the long period grating 321a of the core 321 without losing its intensity.

In addition, the clad layer 322 may have the same effect as described above by etching a portion thereof and exposing the first layer 322a to the atmosphere.

The optical module having the planar waveguide structure according to the present invention includes a clad with a refractive index layer having different dual structures, and a core with a long period grating, so that the semiconductor laser and the core can be removed without using a lens or a spot-limited semiconductor laser. There is an advantage that it is possible to provide an optical module that is easy to align the optical axis. That is, the present invention does not use a semiconductor laser, such as a lens or spot size is limited, there is an advantage that the manufacturing process and optical axis alignment is easy and the production cost is reduced.

Moreover, by combining the uncoupled optical signal inside the core through the long period lattice of the core, the intensity loss of the optical signal is preserved, and further, the clad prevents the unbound optical signal incident on the first layer from leaking out of it. There is an advantage of improving the coupling efficiency of the uncoupled optical signal coupled to the core.

Claims (4)

In an optical module in the form of a planar waveguide, A substrate; A light source mounted on the substrate and outputting light having a predetermined wavelength; An end of which is formed on an upper surface of the substrate so as to face the light source, the waveguide device comprising a core, which is a medium for transmitting light output from the light source, and a cladding surrounding the core; The waveguide device has a first layer surrounding the clad with the clad, and a refractive index value surrounding the first layer and having a lower refractive index than the first layer to couple unbound light incident to the clad with the core. And having a double structure including a second layer, and forming a long-period grating in the core for injecting an uncoupled optical signal incident to the clad into the core. The method of claim 1, The period of the long period grating is a planar waveguide type optical module, characterized in that determined by the following equation (2). (λ: wavelength of an optical signal, n _co : effective refractive index of the core, n _cl : effective refractive index of the first layer, Λ: period of the long period grating) An optical module having a planar waveguide structure integrated on an upper surface of a substrate, A waveguide element comprising a plurality of cores, which are optical transmission mediums formed on an upper surface of the substrate, and a cladding layer surrounding each core; A plurality of light sources mounted on an upper surface of the substrate so as to face one end of each core and corresponding to the cores one to one; The waveguide device has a first layer surrounding the core and a lower refractive index value surrounding the first layer than the first layer to couple unbonded light incident to the clad with the core. Forming a double structure including a second layer, wherein the core forms a long-period grating for injecting an uncoupled optical signal incident to the clad into the clad end at one end thereof; module. The method of claim 3, wherein And the second layer of the clad is a flat waveguide type optical module.