An optical path system for a silicon photonic chip

Abstract

The application relates to an optical path system for a silicon optical chip, comprising: a laser, which provides two paths of incident light to the silicon optical chip; and a lens, which is arranged between the silicon optical chip and the laser, and the two paths of incident light emitted by the laser are condensed by the same lens and then respectively enter two coupling-in light ports of the silicon optical chip. The optical path system of the application adopts two paths of incident light sharing one lens, the two paths of incident light are symmetrically arranged on the two sides of the axis of the center position of the lens and the center positions of the two coupling-in light ports, and after being refracted by the lens, the two paths of incident light can respectively enter two different coupling-in light ports of the silicon optical chip. Compared with the prior art which needs to arrange two lenses to respectively introduce two laser beams, the optical path system of the application reduces the space occupied by the optical path system and reduces the number of components, and after being refracted by the lens, the incident light is obliquely incident into the coupling-in light port, thereby improving the return loss performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication technology, in particular to an optical path system for a silicon optical chip. BACKGROUND

[0002] The silicon optical chip is a photonic integrated circuit manufactured by special process of silicon optical material and device, mainly composed of modulator, detector, passive waveguide device, etc., which integrates various optical devices on the same silicon substrate. The silicon optical chip has the characteristics of high integration, low cost, higher transmission bandwidth, etc. Because the silicon optical chip uses silicon as the substrate of integrated chip, it can integrate more optical devices; in the optical module, the cost of traditional optical chip is very high, and the low cost of silicon optical chip becomes a great advantage; the silicon waveguide has high refractive index contrast between core and cladding, which has strong binding effect on light, so the silicon-based optical waveguide device has small size and high integration, and the manufacturing process of silicon-based optoelectronic device is compatible with CMOS, which is easy to realize low-cost mass production. At present, silicon-based optoelectronic chip has important application in coherent optical communication, optical sensing, laser radar, microwave photonics, etc. For example, silicon-based optical transceiver chip has achieved mass production development in optical communication and optical interconnection field.

[0003] The existing silicon optical chip generally includes two coupling-in light optical ports, which need to be provided with two external lasers to provide incident light. However, the distance between the two coupling-in light optical ports arranged on the silicon optical chip is usually small, such as 250um, and the distance between adjacent optical paths of the optical path system of the traditional free space coupling scheme is usually 1000um, which causes interference problems of components. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the problem that the optical path system of the traditional free space coupling scheme in the prior art cannot meet the incident requirements of the two coupling-in light optical ports with small distance on the silicon optical chip, and to provide an optical path system which adopts two incident light paths to share one lens, reduces the space occupied by the optical path system, reduces the number of components, simplifies the process steps, and improves the return loss performance.

[0005] To solve the above technical problems, the present application provides an optical path system for a silicon optical chip, which provides incident light to two coupling-in light optical ports of the silicon optical chip, comprising:

[0006] A laser provides two incident light paths to the silicon optical chip;

[0007] A lens is arranged between the silicon optical chip and the laser, and the two incident light paths emitted by the laser are condensed by the same lens and then enter the two coupling-in light optical ports of the silicon optical chip, respectively.

[0008] In one embodiment of the present application, the two incident lights are symmetrically arranged on both sides of the axis with the lens center position and the center positions of the two light-in-coupling ports as the axis, and the two incident lights are incident into the two light-in-coupling ports of the silicon optical chip at the same oblique angle after being crossed at the lens.

[0009] In one embodiment of the present application, the oblique angle is 2.5°-3.5°.

[0010] In one embodiment of the present application, the laser is a double waveguide DFB laser, which comprises a first waveguide and a second waveguide arranged independently and capable of providing two laser beams.

[0011] In one embodiment of the present application, the laser is arranged on the axis, and the first waveguide and the second waveguide are arranged on both sides of the axis, respectively.

[0012] In one embodiment of the present application, the lens is arranged on the side close to the laser, and the distance between the lens and the laser is adjusted according to the refractive index of the lens and the interval between the two light-in-coupling ports.

[0013] In one embodiment of the present application, a light-transmitting component capable of changing the optical path is further arranged between the lens and the silicon optical chip.

[0014] In one embodiment of the present application, an isolator is further arranged between the lens and the silicon optical chip.

[0015] To solve the above technical problems, the present application further provides an optical module comprising the optical path system and a silicon optical chip, wherein the silicon optical chip comprises two light-in-coupling ports.

[0016] The above technical solution of the present application has the following advantages compared with the prior art:

[0017] The optical path system for the silicon optical chip provided by the present application adopts an optical path system in which two incident lights share one lens, the two incident lights are symmetrically arranged on both sides of the axis with the lens center position and the center positions of the two light-in-coupling ports as the axis, and the two incident lights can be incident into the two different light-in-coupling ports of the silicon optical chip after being refracted by the lens. Compared with the prior art in which two lenses are arranged to introduce two laser beams, respectively, the optical path system of the present application reduces the space occupied by the optical path system and the number of components, and the incident light is obliquely incident into the light-in-coupling port after being refracted by the lens, thereby improving the return loss performance. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings, in which

[0019] Figure 1 is the overall structure schematic diagram of the optical path system for the silicon optical chip of the present application;

[0020] Figure 2 is the principle schematic diagram of the optical path system of the present application;

[0021] Figure 3 is the structure schematic diagram of an embodiment of the optical path system of the present application.

[0022] Description of the drawings: 1, silicon optical chip; 11, coupling-in light port; 2, laser; 21, first waveguide; 22, second waveguide; 3, lens; 4, isolator. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting the present application.

[0024] Referring to Figure 1 The silicon optical chip 1 in the embodiment includes two coupling-in light ports 11, and in the embodiment, the spacing between the two coupling-in light ports 11 is 250 um due to the small volume of the silicon optical chip 1. Generally, the optical path system for providing coupling light path for the silicon optical chip 1 includes a light-emitting assembly and a lens, and in the embodiment, two sets of optical path systems are needed for the two coupling-in light ports 11, each of which provides incident light for the coupling-in light port 11. However, the minimum spacing between the two sets of existing optical path systems is 1000 um due to the size limitation of the light-emitting assembly and the lens, which cannot meet the requirement of the spacing of 250 um between the coupling-in light ports 11 in the embodiment, and thus the element interference problem occurs and cannot be solved.

[0025] In order to provide coupling light path for the silicon optical chip 1 with small spacing between the coupling-in light ports 11, the embodiment changes the existing optical path system from two independent optical path systems to one optical path system, and the specific scheme is as follows:

[0026] The optical path system in the embodiment includes:

[0027] The laser 2, i.e. the light-emitting assembly, can provide two paths of incident light to the silicon optical chip 1.

[0028] The lens 3 is arranged between the silicon optical chip 1 and the laser 2, and the two paths of incident light emitted by the laser 2 are focused by the same lens 3 and then enter the two coupling-in light ports 11 of the silicon optical chip 1.

[0029] In the embodiment, two incident lights are introduced into the same lens 3, and after 3 refraction convergences of the same lens, are refracted into two coupling-in light ports 11 respectively. Thus, the coupling processing of two incident lights can be realized through only one set of optical path system, the space occupied by the optical path system can be reduced, and the number of components can be reduced, which is theoretically feasible.

[0030] Specifically, in order to ensure that the two incident lights do not interfere with each other and can be respectively incident into the two coupling-in light ports 11 after passing through the lens 3, referring to FIG. 2, the specific operation scheme of the present embodiment is as follows: first, the two incident lights are symmetrically arranged on both sides of the axis with the center position of the lens 3 and the center position of the two coupling-in light ports 11 as the axis, and after the two incident lights intersect with the lens 3 as the center, they are focused and emitted from the lens 3 after twice refraction in the lens 3, and the two incident lights are focused from the lens 3 at the same oblique angle as the laser 2 incident on the lens 3 and are incident into the two coupling-in light ports 11 of the silicon optical chip 1. Figure 2

[0031] There are two technical problems that need to be further verified and discussed by using the above technical scheme:

[0032] 1. Whether the two incident lights incident into the same lens 3 will affect each other in the same lens, increase the coupling loss, and thus reduce the coupling efficiency;

[0033] 2. Whether the oblique incidence in the present embodiment has an impact on the coupling effect, compared with the vertical incidence provided by the traditional optical path system after the incident light is coupled through the lens 3;

[0034] In order to verify the feasibility of the scheme, ZEMAX simulation experiment is conducted on the optical path system. The result of the ZEMAX simulation experiment shows that, compared with the traditional optical path system, the optical path system of the present embodiment does have coupling loss, but the increased coupling loss is about 2dB, which is within an acceptable range, and has only a small impact on the overall coupling efficiency. Moreover, it is found through the ZEMAX simulation experiment that, compared with the existing vertical incidence, the return loss of the present embodiment is increased. The reason is that the optical path of the present embodiment is not vertical incidence, and the reflected light will not return along the original path, which increases the return loss and thus indirectly improves the return loss performance. Therefore, the technical scheme of the present embodiment can not only meet the incident requirement of small spacing between the coupling-in light ports 11 of the silicon optical chip 1, reduce the space occupied by the optical path system and the number of components, but also has an additional technical effect of improving the return loss performance at the cost of a small coupling efficiency.

[0035] ​Specifically, the effect of improving the back loss performance by changing the incident angle of incidence is beneficial, and further comparison is carried out to verify the effect. In the comparative experiment, the same type of laser 2 and lens 3 are used, and the relative positions of the laser 2 and the lens 3 are kept the same, only the off-axis distance of the laser 2 is changed, so that the incident light is tilted by 0-5° after passing through the lens, and the angle is changed by 0.5° each time, so that ten experiments are carried out. The experiment shows that when the incident angle is 2.5-3.5°, the coupling efficiency can be ensured, and the back loss can be increased, and the back loss performance is improved. When the incident angle is less than 2.5°, although the coupling efficiency can be ensured, the incident angle is small, the effect of increasing the back loss is not obvious, and the back loss performance cannot be improved. When the incident angle exceeds 3.5°, the coupling efficiency is significantly reduced due to the large incident angle, so the incident angle needs to be limited, and the incident angle is controlled to be 2.5°-3.5°, so that the coupling efficiency can be ensured, and the back loss index can be optimized.

[0036] Specifically, in the embodiment, the laser 2 needs to provide two laser beams. If two independent lasers 2 are used, the distance between the two lasers 2 is relatively large, and even if the same lens 3 is used, it is difficult to meet the distance requirement of the small silicon optical chip 1. Therefore, in the embodiment, the light source is also improved. In order to compress the distance between the two incident lights from the light emitting component, the laser 2 in the embodiment uses a double waveguide DFB laser. The DFB (Distributed Feedback Laser) is a side-emitting semiconductor laser with a built-in Bragg grating. The double waveguide DFB laser includes a first waveguide 21 and a second waveguide 22 arranged independently, which can provide two laser beams. The laser 2 is arranged on the axis, and the first waveguide 21 and the second waveguide 22 are respectively located on both sides of the axis.

[0037] Specifically, in the embodiment, the distance between the first waveguide 21 and the second waveguide 22 of the double waveguide DFB laser is less than the distance of 250um between the two light-in coupling light ports 11 of the silicon optical chip 1. Therefore, the lens 3 is arranged on the side close to the laser 2. The distance between the lens 3 and the laser 2 is adjusted according to the refractive index of the lens 3 and the distance between the two light-in coupling light ports 11, so that the two incident lights refracted by the lens 3 can be injected into the two light-in coupling light ports 11. In the embodiment, lenses 3 with different refractive indexes can be used, and the distance between the lens 3 and the laser 2 needs to be adjusted to ensure that the two incident lights refracted by the lens 3 can be accurately injected into the two light-in coupling light ports 11.

[0038] In other embodiments, the interval between the two coupling-in light ports 11 in different models of the silicon optical chip 1 is also different, the interval in the present embodiment is 250 um, and in other embodiments, the interval can be 300 um, 350 um. The optical path system in the present embodiment can also provide a coupling optical path, and only the positions of the lens 3 and the laser 2 need to be changed according to the interval of the coupling-in light ports 11.

[0039] Referring to Figure 3 In the present embodiment, an isolator 4 is further arranged between the lens 3 and the silicon optical chip 1, so as to further increase the return loss. The isolator 4 allows the incident light to propagate in only one fixed direction, and can effectively prevent the reflection light.

[0040] Specifically, in other embodiments, in order to further change the direction of the light coupled through the lens 3 according to the position of the coupling-in light port 11 on the silicon optical chip 1, a light-transmitting component capable of changing the optical path, such as a prism, glass or the like, is further arranged between the lens 3 and the silicon optical chip 1.

[0041] The present application further discloses an optical module, comprising the optical path system and a silicon optical chip 1, wherein the silicon optical chip 1 comprises two coupling-in light ports 11, and the optical path system provides incident light for the silicon optical chip 1.

[0042] Obviously, the above embodiments are only examples for clearly illustrating the present application, and are not intended to limit the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. An optical path system for a silicon photonics chip, providing incident light to two coupled optical input ports of the silicon photonics chip, characterized in that, include: The laser provides two incident beams to the silicon photonic chip; A lens is positioned between the silicon photonics chip and the laser. Two incident beams emitted by the laser are focused by the same lens and then directed into two optical input ports of the silicon photonics chip. The two incident beams are symmetrically offset on both sides of the axis with the center of the lens and the center of the two coupled light ports as the axis. After the two incident beams intersect with the lens as the center, they enter the two coupled light ports of the silicon photonics chip at the same tilt angle. The tilt angle is 2.5° to 3.5°; The laser is a dual-waveguide DFB laser, which includes an independently set first waveguide and a second waveguide, and is capable of providing two laser beams. The laser is set on an axis, with the first waveguide and the second waveguide located on opposite sides of the axis.

2. The optical path system for silicon photonics chips according to claim 1, characterized in that: The lens is positioned on the side close to the laser, and the distance between the lens and the laser is adjusted according to the refractive index of the lens and the spacing between the two optical input ports.

3. The optical path system for silicon photonics chips according to claim 1, characterized in that: A light-transmitting element capable of changing the light path is also disposed between the lens and the silicon photonic chip.

4. The optical path system for silicon photonics chips according to claim 1, characterized in that: An isolator is also provided between the lens and the silicon photonic chip.

5. An optical module, characterized in that: The optical path system comprising any one of claims 1 to 4 further comprises a silicon photonics chip, wherein the silicon photonics chip comprises two optical input ports.

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