CN103091783B - Tunable array waveguide grating based on liquid crystal waveguides - Google Patents

Abstract

The invention relates to a tunable array waveguide grating based on liquid crystal waveguides, and belongs to integrated waveguide optical devices. The problems that an existing tunable array waveguide grating is complex in preparation technology, relatively high in cost and relatively poor in consistency of performance are solved. The tunable array waveguide grating based on the liquid crystal waveguides comprises an input coupled area, an array waveguide area, an output coupled area and an output waveguide area, wherein the input coupled area, the array waveguide area, the output coupled area and the output waveguide area are arrayed in sequence on a light path, the input coupled area is formed by a first right trapezoid prism-shaped electrode, a second right trapezoid prism-shaped electrode, a concave-lens-shaped electrode and a first convex-lens-shaped electrode, the array waveguide area is formed by N parallel vertical-bar-shaped electrodes, the output coupled area is formed by second convex-lens-shaped electrodes, and the output waveguide area is formed by M parallel vertical-bar-shaped electrodes. The electrodes in various shapes are all plated on the upper surface of a liquid crystal layer of a liquid crystal waveguide. The tunable array waveguide grating based on the liquid crystal waveguides is simple in structure, easy to manufacture and low in cost, the electrooptic effect of the liquid crystal layer is used to achieve tunable performance, and the tunable array waveguide grating based on the liquid crystal waveguides is beneficial for demultiplexing wave band frequency tuning.

Description

A Tunable Arrayed Waveguide Grating Based on Liquid Crystal Waveguide

technical field

The invention belongs to an integrated waveguide optical device, in particular to a tunable arrayed waveguide grating based on a liquid crystal waveguide.

Background technique

As one of the most important optical devices in the optical fiber communication network, the arrayed waveguide grating (AWG) has gradually entered the commercial stage from the laboratory stage since it was proposed by Smit in 1988. As shown in Figure 1, an AWG with a traditional structure generally consists of five parts: input waveguide 1, input free transmission area 2, array waveguide 3, output free transmission area 4, and output waveguide 5. Since there is a certain optical path difference nΔL between adjacent waveguides in the arrayed waveguide, the light of each wavelength will produce different phase differences, thereby realizing the function of grating dispersion. The function of AWG is to separate the light of each wavelength in the composite light composed of different wavelengths, and it is a device that realizes wave division and multiplexing.

As an important DWDM (Dense Wavelength Division Multiplexing) device, how to increase the tunable performance of the existing AWG is an important research topic. In conventional AWGs, the materials used have low electro-optic coefficients, making electro-optic tuning almost impossible. The existing integrated tunable AWG technical solution uses electro-optical phase shifters in the arrayed waveguide 3 to realize its continuous tuning function. In terms of design structure, the input and output slab waveguides are still slab waveguides with a Rowland circle structure, forming Each waveguide of the arrayed waveguide is still a curved rectangular waveguide. With the existing integrated waveguide technology, the preparation process is complicated, the cost is high, and the performance consistency is poor; see Heck, M.J.R., La Porta, A., Leijtens, X.J.M et al., Monolithic AWG-based Discretely Tunable Laser Diode With Nanosecond Switching Speed, IEEE Photonics Technology Letters, 2009, 21(13): 905-907.

The high electro-optic coefficient of liquid crystals (the typical value of the refractive index change at 5V voltage is 0.2) provides the possibility to realize tunable integrated optoelectronic devices, and some related researches have been reported, such as tunable switches and tunable SOI microring resonators. Due to the development of integrated optical waveguide technology, the good electro-optic effect of liquid crystal waveguide provides a new development path and direction for the development of new optoelectronic devices.

Contents of the invention

The invention provides a liquid crystal waveguide-based tunable arrayed waveguide grating, which solves the problems of complex preparation process, high cost and poor performance consistency of the existing tunable arrayed waveguide grating.

A tunable arrayed waveguide grating based on a liquid crystal waveguide provided by the present invention includes an input coupling region, an arrayed waveguide region, an output coupling region and an output waveguide region arranged sequentially on the optical path, and is characterized in that:

The input coupling area is composed of the first rectangular trapezoidal prism-shaped electrode, the second rectangular trapezoidal prism-shaped electrode, the concave lens-shaped electrode and the first convex lens-shaped electrode arranged in sequence on the optical path, forming a beam collimation beam expansion system; wherein, the first The right-angled trapezoidal prism-shaped electrode and the second right-angled trapezoidal prism-shaped electrode have the same shape, and the two are inverted and spliced into a rectangle;

The arrayed waveguide area is composed of N parallel straight strip-shaped electrodes, forming a parallel straight arrayed waveguide area, N≥3;

The output coupling area is composed of a second convex lens-shaped electrode, forming a beam convergence interference area;

The output waveguide area is composed of M parallel straight strip-shaped electrodes to form an output waveguide, M is the number of output channels, M≥1;

The above-mentioned electrodes of various shapes are all plated on the upper surface of the liquid crystal layer of the liquid crystal waveguide; the side section of the liquid crystal waveguide is a liquid crystal layer, a waveguide layer, a lower cladding layer, and a substrate in sequence from top to bottom.

The incident light enters from the end face of the liquid crystal waveguide.

The tunable arrayed waveguide grating is further characterized by:

The gap between each part of the input coupling area, the arrayed waveguide area, the output coupling area and the output waveguide area is 10 μm to 1000 μm;

The length of the upper side of the first rectangular trapezoidal prism-shaped electrode and the second rectangular trapezoidal prism-shaped electrode is 10 μm to 100 μm, the ratio of the upper and lower sides is 1:2 to 1:4, and the height is 50 μm to 2000 μm;

The electrode in the shape of a concave lens has an upper and lower side length of 20 μm to 400 μm, a height of 50 μm to 2000 μm, and a focal length of 10 μm to 1000 μm;

The first convex lens-shaped electrode has a height of 50 μm to 2000 μm and a focal length of 10 μm to 1000 μm;

The gap between the first rectangular trapezoidal prism-shaped electrode, the second rectangular trapezoidal prism-shaped electrode, the concave lens-shaped electrode and the first convex lens-shaped electrode is 5 μm to 20 μm;

In the arrayed waveguide region, the shape and size of each straight electrode are the same, with a width of 2 μm to 5 μm, a length of 500 μm to 3000 μm, and an interval of 10 μm to 20 μm;

The second convex lens-shaped electrode has a height of 50 μm to 2000 μm and a focal length of 10 μm to 1000 μm;

In the output waveguide area, the shape and size of each straight electrode are the same, with a width of 2 μm-5 μm, a length of 100 μm-1000 μm, and an interval of 10 μm-50 μm.

In the tunable arrayed waveguide grating, the material of the waveguide layer of the liquid crystal waveguide is silicon (Si) or silicon nitride (Si ₃ N ₄ ), with a thickness of 0.3 μm to 2.0 μm;

Each electrode material of the input coupling area, the array waveguide area, the output coupling area and the output waveguide area is indium tin oxide (ITO).

The present invention is based on a flat liquid crystal waveguide. When transmitting light, an appropriate voltage is set on each electrode constituting the input coupling region, so that the liquid crystal waveguide below each electrode constitutes an equivalent first right-angled trapezoidal prism, a second right-angled trapezoidal prism, a concave lens and The first convex lens optical element; the light passes through the input coupling area to form collimated and expanded beam parallel light, which is uniformly coupled into the arrayed waveguide area, and then transmitted to the output coupling area by the arrayed waveguide area, where the second convex lens shape electrode constituting the output coupling area Set the appropriate voltage so that the liquid crystal waveguide under the electrode constitutes an equivalent second convex lens optical element, and the light realizes multi-beam convergence and interference in the output coupling area, and the light of different wavelengths will converge on the waveguides at different positions in the output waveguide area output to realize the function of wave division multiplexing.

The tunable performance principle of the present invention is: the voltage of the straight strip-shaped electrodes parallel to the arrayed waveguide region for: in To be applied to each straight strip-shaped electrode, so that the liquid crystal waveguide under the straight strip-shaped electrode constitutes the voltage of an equivalent strip waveguide; In order to be added to each straight-shaped electrode, the voltage that causes each equivalent strip-shaped waveguide to generate an optical path difference; set the voltage on each straight-shaped electrode The optical path difference of the equivalent strip waveguide in the arrayed waveguide area can be controlled, and the effect of continuously tunable output light wavelength can be achieved.

The invention is simple in structure, easy to manufacture, and low in cost. The arrayed waveguide area is composed of parallel straight strip-shaped electrodes. Compared with the curved arrayed waveguide of the same structure as the traditional AWG, the performance consistency is good; the electro-optical effect of the liquid crystal layer is used to realize tunable performance, which facilitates its demultiplexed band frequency tuning.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a traditional arrayed waveguide grating;

Fig. 2 is a structural representation of the present invention;

FIG. 3 is a schematic diagram of a side sectional structure of a liquid crystal waveguide;

Fig. 4 is a schematic diagram of the electrode shape of the input coupling region;

Fig. 5 is a schematic diagram of the shape of electrodes in the arrayed waveguide region.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Fig. 2, the present invention includes an input coupling region 7, an array waveguide region 8, an output coupling region 9 and an output waveguide region 10 arranged sequentially on the optical path; the above-mentioned parts are all plated on the upper surface of the liquid crystal layer of the liquid crystal waveguide 6; Incident light enters from the end face of the liquid crystal waveguide 6 .

As shown in FIG. 3 , the liquid crystal waveguide 6 includes a liquid crystal layer 6-1, a waveguide layer 6-2, a lower cladding layer 6-3, and a substrate 6-4 from top to bottom.

As shown in Figure 4, the input coupling region 7 consists of a first rectangular trapezoidal prism-shaped electrode 7-1, a second rectangular trapezoidal prism-shaped electrode 7-2, a concave lens-shaped electrode 7-3 and a first convex lens arranged in sequence on the optical path A shape electrode 7-4 is formed to form a beam collimation and beam expansion system; wherein, the first rectangular trapezoidal prism-shaped electrode 7-1 and the second rectangular trapezoidal prism-shaped electrode 7-2 have the same shape, and the two are inverted and spliced into a rectangle;

As shown in FIG. 5 , the arrayed waveguide region 8 is composed of N parallel straight strip-shaped electrodes, forming a parallel straight arrayed waveguide region;

The output coupling area 9 is composed of a second convex lens-shaped electrode, forming a convergent interference area for light beams;

The output waveguide area 10 is composed of M parallel straight strip-shaped electrodes to form an output waveguide, where M is the number of output channels.

Embodiment 1 of the present invention:

The gap between the input coupling region 7, the arrayed waveguide region 8, the output coupling region 9 and the output waveguide region 10 is 300 μm;

The first right-angled trapezoidal prism-shaped electrode 7-1 and the second right-angled trapezoidal prism-shaped electrode 7-2 have an upper side length of 100 μm, a ratio of upper and lower side lengths of 1:4, and a height of 2000 μm,

The concave lens-shaped electrode 7-3 has an upper and lower side length of 400 μm, a height of 2000 μm, and a focal length of 500 μm.

The first convex lens-shaped electrode 7-4 has a height of 2000 μm and a focal length of 500 μm,

The gap between the first rectangular trapezoidal prism-shaped electrode 7-1, the second rectangular trapezoidal prism-shaped electrode 7-2, the concave lens-shaped electrode 7-3 and the first convex lens-shaped electrode 7-4 is 20 μm;

The arrayed waveguide region 8 is composed of 80 parallel straight strip-shaped electrodes, each of which has the same shape and size, a width of 5 μm, a length of 3000 μm, and an interval of 20 μm;

The second convex lens-shaped electrode has a height of 2000 μm and a focal length of 500 μm,

The output waveguide region 10 is composed of 8 parallel straight strip-shaped electrodes, each of which has the same shape and size, with a width of 5 μm, a length of 1000 μm, and an interval of 50 μm.

For the tunable arrayed waveguide grating, the material of the waveguide layer 6-2 of the liquid crystal waveguide 6 is silicon nitride (Si ₃ N ₄ ), with a thickness of 0.3 μm;

The electrode materials of the input coupling region 7 , the arrayed waveguide region 8 , the output coupling region 9 and the output waveguide region 10 are indium tin oxide (ITO).

Embodiment 2 of the present invention:

The gap between each part of the input coupling region 7, the arrayed waveguide region 8, the output coupling region 9 and the output waveguide region 10 is 50 μm;

The first rectangular trapezoidal prism-shaped electrode 7-1 and the second rectangular trapezoidal prism-shaped electrode 7-2 have an upper side length of 10 μm, a ratio of upper and lower side lengths of 1:2, and a height of 50 μm,

The concave lens-shaped electrode 7-3 has an upper and lower side length of 20 μm, a height of 50 μm, and a focal length of 100 μm.

The first convex lens-shaped electrode 7-4 has a height of 50 μm and a focal length of 100 μm,

The gap between the first rectangular trapezoidal prism shaped electrode 7-1, the second rectangular trapezoidal prism shaped electrode 7-2, the concave lens shaped electrode 7-3 and the first convex lens shaped electrode 7-4 is 5 μm;

The arrayed waveguide region 8 is composed of 10 parallel straight-strip electrodes, each of which has the same shape and size, with a width of 2 μm, a length of 1000 μm, and an interval of 5 μm;

The second convex lens-shaped electrode has a height of 50 μm and a focal length of 100 μm,

The output waveguide region 10 is composed of two parallel straight electrodes, each of which has the same shape and size, with a width of 2 μm, a length of 100 μm, and an interval of 10 μm.

For the tunable arrayed waveguide grating, the material of the waveguide layer 6-2 of the liquid crystal waveguide 6 is silicon (Si), and the thickness is 0.6 μm;

The electrode materials of the input coupling region 7 , the arrayed waveguide region 8 , the output coupling region 9 and the output waveguide region 10 are indium tin oxide (ITO).

Embodiment 3 of the present invention:

The gap between the input coupling region 7, the arrayed waveguide region 8, the output coupling region 9 and the output waveguide region 10 is 100 μm;

The first right-angled trapezoidal prism-shaped electrode 7-1 and the second right-angled trapezoidal prism-shaped electrode 7-2 have an upper side length of 50 μm, a ratio of upper and lower side lengths of 1:3, and a height of 1000 μm,

The electrode 7-3 in the shape of a concave lens has an upper and lower side length of 150 μm, a height of 1000 μm, and a focal length of 100.

The first convex lens-shaped electrode 7-4 has a height of 1000 μm and a focal length of 100 μm,

The gap between the first rectangular trapezoidal prism-shaped electrode 7-1, the second rectangular trapezoidal prism-shaped electrode 7-2, the concave lens-shaped electrode 7-3 and the first convex lens-shaped electrode 7-4 is 10 μm;

The arrayed waveguide region 8 is composed of 50 parallel straight strip-shaped electrodes, each of which has the same shape and size, a width of 4 μm, a length of 2000 μm, and an interval of 15 μm;

The second convex lens-shaped electrode has a height of 1000 μm and a focal length of 100 m,

The output waveguide region 10 is composed of 4 parallel straight strip-shaped electrodes, each of which has the same shape and size, with a width of 4 μm, a length of 500 μm, and an interval of 25 μm.

For the tunable arrayed waveguide grating, the material of the waveguide layer 6-2 of the liquid crystal waveguide 6 is silicon nitride (Si ₃ N ₄ ), with a thickness of 2.0 μm;

The electrode materials of the input coupling region 7 , the arrayed waveguide region 8 , the output coupling region 9 and the output waveguide region 10 are indium tin oxide (ITO).

Claims (3)

1. A tunable arrayed waveguide grating based on a liquid crystal waveguide, including an input coupling region (7), an arrayed waveguide region (8), an output coupling region (9) and an output waveguide region (10) arranged in sequence on the optical path. Features: The input coupling area (7) consists of the first rectangular trapezoidal prism-shaped electrode (7-1), the second rectangular trapezoidal prism-shaped electrode (7-2), the concave lens-shaped electrode (7-3) and the second rectangular trapezoidal prism-shaped electrode (7-3) arranged in sequence on the optical path. A convex lens-shaped electrode (7-4) forms a beam collimation and beam expansion system; wherein, the first right-angled trapezoidal prism-shaped electrode (7-1) and the second right-angled trapezoidal prism-shaped electrode (7-2) have the same shape, The two are inverted and spliced into a rectangle; The arrayed waveguide area (8) is composed of N parallel straight electrodes, forming a parallel straight arrayed waveguide area, N≥3; The output coupling area (9) is composed of a second convex lens-shaped electrode, forming a beam convergence interference area; The output waveguide area (10) is composed of M parallel straight strip-shaped electrodes to form an output waveguide, M is the number of output channels, M≥1; The side section of the liquid crystal waveguide (6) is sequentially from top to bottom the liquid crystal layer (6-1), the waveguide layer (6-2), the lower cladding layer (6-3), and the substrate (6-4); Electrodes of various shapes are plated on the upper surface of the liquid crystal layer of the liquid crystal waveguide (6). 2. The tunable arrayed waveguide grating as claimed in claim 1, characterized in that: The gap between each part of the input coupling area (7), the arrayed waveguide area (8), the output coupling area (9) and the output waveguide area (10) is 10 μm to 1000 μm; The first rectangular trapezoidal prism-shaped electrode (7-1) and the second rectangular trapezoidal prism-shaped electrode (7-2) have an upper side length of 10 μm to 100 μm, a ratio of upper and lower side lengths of 1:2 to 1:4, and a height of 50μm～2000μm; The concave lens-shaped electrode (7-3) has an upper and lower side length of 20 μm to 400 μm, a height of 50 μm to 2000 μm, and a focal length of 10 μm to 1000 μm; The first convex lens-shaped electrode (7-4) has a height of 50 μm to 2000 μm and a focal length of 10 μm to 1000 μm; The gap between the first rectangular trapezoidal prism-shaped electrode (7-1), the second rectangular trapezoidal prism-shaped electrode (7-2), the concave lens-shaped electrode (7-3) and the first convex lens-shaped electrode (7-4) 5 μm ~ 20 μm; In the arrayed waveguide region (8), the shape and size of each straight-shaped electrode are the same, with a width of 2 μm to 5 μm, a length of 500 μm to 3000 μm, and an interval of 10 μm to 20 μm; The second convex lens-shaped electrode has a height of 50 μm to 2000 μm and a focal length of 10 μm to 1000 μm; In the output waveguide area (10), the shape and size of each straight-shaped electrode are the same, with a width of 2 μm to 5 μm, a length of 100 μm to 1000 μm, and an interval of 10 μm to 50 μm. 3. The tunable arrayed waveguide grating as claimed in claim 1 or 2, characterized in that: The material of the waveguide layer (6-2) of the liquid crystal waveguide (6) is silicon or silicon nitride, with a thickness of 0.3 μm to 2.0 μm; The electrode materials of the input coupling area (7), the array waveguide area (8), the output coupling area (9) and the output waveguide area (10) are indium tin oxide.