CN105700203A - Planar waveguide type near-and-mid infrared light modulator based on graphene-chalcogenide glass - Google Patents

Abstract

The invention discloses a planar waveguide type near-and-mid infrared light modulator based on graphene-chalcogenide glass, and belongs to the technical field of electro-optical modulators. The optical modulator solves the problems in modulation and demodulation of integrated photonic devices based on optical signals of near-and-mid infrared light ranging from 1.55 microns to 3 microns. The modulator comprises a substrate layer, ridge-shaped light waveguide layers, a first strut and a second strut, wherein the ridge-shaped light waveguide layers, the first strut and the second strut are arranged on the substrate layer; a first graphene layer and a second graphene layer are arranged on the ridge-shaped light waveguide layers; the first graphene layer extends to the upper surface of the first strut, and the second graphene layer extends to the upper surface of the second strut; isolation medium layers are arranged between the ridge-shaped optical waveguide layer and the first graphene layer, between the ridge-shaped optical waveguide layer and the second graphene layer, between the first graphene layer and the second graphene layer, between the first graphene layer and the first strut, and between the second graphene layer and the second strut respectively; a first electrode is arranged on the first graphene layer on the first strut, and a second electrode is arranged on the second graphene layer on the second strut. The modulator is used for signal modulation and demodulation in the integrated photonic devices.

Description

Near-mid-infrared optical modulator based on graphene-chalcogenide glass planar waveguide

technical field

A near-mid-infrared optical modulator based on graphene-chalcogenide glass planar waveguide, used for integrated photonic devices to modulate and demodulate 1.55-3μm near-mid-infrared optical signals, belonging to electro-optic modulators, especially related to graphene-sulfur based The invention relates to the technical field of glass planar waveguide near-mid infrared light modulators.

Background technique

It is an inevitable trend of historical development that photons replace electrons as the carrier of information. The research of modern integrated optics mainly focuses on the near-infrared communication band. With practical application, the wavelength band of integrated optics research has gradually shifted from the first-generation 0.85μm to the second-generation 1.31μm and to the most mainstream 1.555μm wavelength. Various optical devices, including optical waveguides, optical couplers, optical switches, optical modulators, filters, analog-to-digital converters, and detectors, have been extensively studied and fabricated successfully. Integrated optics has become a research hotspot all over the world and is developing rapidly, which is of great significance to optical fiber communication, optical signal processing, and photoelectric hybrid integration with integrated circuits. So far, various materials and devices of integrated optics working in the near-infrared light band of 0.8-1.55 μm have led the industrialization of high-tech optical communication and become an important pillar of the current information industry.

The mid-infrared band (2‐20μm) is an important band in solar radiation, and it has very important applications in various scientific and technological fields, including sensing, environmental monitoring, biomedical applications, thermal imaging, military applications, etc. Although the mid-infrared light has great application potential in various fields, and the research in the near-infrared band has attracted enough attention, the progress of integrated photonics in the mid-infrared band has been very slow, and it has been facing great difficulties and difficulties for many years. The challenges are far less than the research and development of the near-infrared communication band. The first is the problem of the light source. In the early days, a continuous mid-infrared light source was usually very large in size and very expensive, and some of them required cryogenic cooling. The second is the problem of transmission, limited by the difficulty of the light source, the research on waveguides and optical fibers for transmitting mid-infrared signals is also full of difficulties.

In recent years, with the development of quantum cascade lasers, the problem of mid-infrared light sources has been solved to a certain extent. According to literature reports, many research groups have developed quantum cascade lasers based on different mid-infrared wavelengths. These lasers not only solve the previous problems of high cost and large volume, but also have a wide range of wavelengths, up to 9 μm (see Literature MuJ.Soref, et al.Silicon‐on‐nitridestructuresformid‐infraredgap‐plasmonwaveguiding[J].AppliedPhysicsLetters, 2014, 104(3)), and commercial production is already available. Similarly, mid-infrared optical fibers have also been developed. Taking IRphotonics in the United States as an example, their heavy metal fluoride optical fibers such as ZBLAN (ZrF4‐BaF2‐LaF3‐AlF3‐NaF) have very stable mid-infrared light bands. Excellent transmission characteristics, the transmission loss in the 300nm to 4500nm band can be less than 0.2dB/cm. In addition, IRphotonics can also provide mid-infrared single-mode fiber, mid-infrared multimode fiber, mid-infrared high-power fiber, mid-infrared doped fiber, etc. Therefore, the development of mid-infrared lasers and optical fibers has promoted the research of mid-infrared integrated optoelectronics, making it possible for the research in the mid-infrared band to develop as rapidly as the near-infrared band. But generally speaking, research on mid-infrared optical devices, including mid-infrared optical modulators, is still lagging behind, especially the modulation and demodulation of integrated photonic devices based on 1.55-3 μm near-mid-infrared optical signals.

Contents of the invention

The present invention provides a graphene-chalcogenide glass planar waveguide-based near-mid-infrared optical modulator to solve the problem of modulation and demodulation of integrated photonic devices based on near-mid-infrared optical signals of 1.55-3 μm.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A near-mid-infrared optical modulator based on graphene-chalcogenide glass planar waveguide, characterized in that it includes a base layer, a ridge-shaped optical waveguide layer arranged on the base layer, a first pillar and a second pillar, and the first pillar The first graphene layer and the second graphene layer are arranged on the ridge-shaped optical waveguide layer, and the first graphene layer extends to the upper surface of the first pillar , the second graphene layer extends to the upper surface of the second pillar, between the ridge-shaped optical waveguide layer and the first graphene layer and the second graphene layer, the first graphene layer and the second graphene layer, the first graphene layer layer and the first pillar, the second graphene layer and the second pillar are respectively provided with an isolation dielectric layer, the first graphene layer on the first pillar is provided with a first electrode, and the second graphene layer on the second pillar A second electrode is disposed on the layer.

Further, the ridge optical waveguide layer is divided into a first ridge optical waveguide layer and a second ridge optical waveguide layer arranged on the first ridge optical waveguide layer, the first graphene layer, the second graphene The layers are sequentially arranged between the first ridge optical waveguide layer and the second ridge optical waveguide layer from bottom to top; the first ridge optical waveguide layer and the first graphene layer, the first graphene layer and the first The isolation dielectric layer between the pillars is the first isolation dielectric layer; the isolation dielectric layer between the first graphene layer and the second graphene layer, the second graphene layer and the second pillar is the second isolation dielectric layer; The isolation dielectric layer between the second graphene layer and the second ridge optical waveguide layer is a third isolation dielectric layer.

Further, the first graphene layer and the second graphene layer are sequentially arranged on the upper surface of the ridge-shaped optical waveguide layer from bottom to top, and the ridge-shaped optical waveguide layer is connected with the first graphene layer and the first graphene layer. The isolation dielectric layer between the first pillar is the first isolation dielectric layer; the isolation dielectric layer between the first graphene layer and the second graphene layer, the second graphene layer and the second pillar is the second isolation medium layer.

Further, the material of the base layer is silicon dioxide.

Further, the material of the ridge-shaped optical waveguide layer is a chalcogenide glass material.

Further, the chalcogenide glass material is a compound glass formed of Group VI elements other than O as anions and other metal and non-metal elements, which may be Ge ₂₃ Sb ₇ S ₇₀ , As ₂ Se ₃ , As ₂ S ₃ one of the materials.

Further, the first pillar, the second pillar and the base layer form a groove structure, and the ridge-shaped optical waveguide layer is arranged in the groove structure.

Further, the thickness of the isolation dielectric layer is 5-60 nm.

Further, the isolation dielectric layer is one of insulating materials such as silicon oxide, silicon oxynitride, and boron nitride.

Further, the first electrode and the second electrode are composed of two layers of materials, the first layer is a material in contact with the first graphene layer and the second graphene layer, and the second layer is a material arranged on the first layer The material of the first layer is one of titanium, nickel, cobalt and palladium, and the material of the second layer is one of gold, silver, platinum and copper.

Compared with the prior art, the present invention has the advantages of:

1. The mid-infrared light modulator of the present invention places the graphene between the ridge-shaped optical waveguide layer and the pillars in the air, which can improve the mobility of graphene carriers, increase the operating speed of the device, and the modulation rate can be as high as 122GHz/bit;

2. The ridge-shaped optical waveguide layer material in the mid-infrared light modulator of the present invention is a chalcogenide glass material, which has a wide and flat transmittance to the mid-infrared spectrum, and can realize modulation of 1.55-3.0 μm mid-infrared light wave signals ;

3. The mid-infrared light modulator of the present invention has small size, high modulation rate and high extinction ratio, and its preparation process is compatible with traditional CMOS process, and it is easy to integrate.

Description of drawings

Fig. 1 is a schematic diagram of a cross-sectional structure of a near-mid-infrared light modulator embedding graphene in the middle of a ridge-shaped optical waveguide layer in an embodiment of the present invention;

Fig. 2 is a cross-sectional schematic diagram of placing graphene on the upper surface of a ridge-shaped optical waveguide layer in a near-mid-infrared light modulator in an embodiment of the present invention;

Fig. 3 shows that the light absorption coefficient of the TM mode in the ridge optical waveguide layer varies with the graphene chemical potential energy when the incident light wavelengths are 1.55 μm, 2 μm, 2.5 μm, and 3 μm in the near-middle infrared light modulator in the embodiment of the present invention. change curve;

Fig. 4 shows the TM modes in the ridge optical waveguide layer in the "ON" and "OFF" states when the incident light wavelengths of the near-mid-infrared light modulator in the embodiment of the present invention are 1.55 μm, 2 μm, 2.5 μm, and 3 μm respectively Plot of normalized power variation with transmission distance.

In the figure: 1. base layer, 2. ridge-shaped optical waveguide layer, 21. first ridge-shaped optical waveguide layer, 22. second ridge-shaped optical waveguide layer, 31. first pillar, 32. second pillar, 41, First graphene layer, 42, second graphene layer, 51, first isolation dielectric layer, 52, second isolation dielectric layer, 51, third isolation dielectric layer, 61, first electrode, 62, second electrode.

detailed description

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

A near-mid-infrared optical modulator based on graphene-chalcogenide glass planar waveguide, including a base layer, a ridge-shaped optical waveguide layer disposed on the base layer, a first pillar and a second pillar, and the first pillar and the second pillar They are respectively arranged on both sides of the ridge-shaped optical waveguide layer, and a first graphene layer and a second graphene layer are arranged on the ridge-shaped optical waveguide layer, the first graphene layer extends to the upper surface of the first pillar, and the second graphite The ene layer extends to the upper surface of the second pillar, between the ridge optical waveguide layer and the first graphene layer and the second graphene layer, the first graphene layer and the second graphene layer, the first graphene layer and the first graphene layer An isolation dielectric layer is respectively arranged between the pillar, the second graphene layer and the second pillar, the first electrode is arranged on the first graphene layer on the first pillar, and the second graphene layer on the second pillar is provided with second electrode.

Preferably, the material of the base layer is silicon dioxide.

Preferably, the material of the ridge optical waveguide layer is a chalcogenide glass material.

Preferably, the chalcogenide glass material is a compound glass formed of Group VI elements other than O as anions and other metal and non-metal elements, which may be Ge ₂₃ Sb ₇ S ₇₀ , As ₂ Se ₃ , As ₂ S One of ₃ materials.

Preferably, the first pillar, the second pillar and the base layer form a groove structure, and the ridge-shaped optical waveguide layer is arranged in the groove structure.

Preferably, the thickness of the isolation dielectric layer is 5-60 nm.

Preferably, the isolation dielectric layer is one of insulating materials such as silicon oxide, silicon oxynitride, and boron nitride.

Preferably, the first electrode and the second electrode are composed of two layers of materials, the first layer is a material in contact with the first graphene layer and the second graphene layer, and the second layer is a material arranged on the first layer Material, the material of the first layer is a kind of in titanium, nickel, cobalt, palladium with good adhesion with graphene material, the material of the second layer is a kind of in gold, silver, platinum, copper material, as Extract the electrodes.

Preferably, the first graphene layer and the second graphene layer are completely overlapped in the ridge optical waveguide layer.

The working principle of the optical modulator of the present invention is as follows: the ridge optical waveguide material of the optical modulator adopts chalcogenide glass material, which has lower waveguide loss for the near-mid infrared spectrum of 1.55-3 μm, and the graphene material is a material for wide spectrum (including 1.55 ~ 3μm near-mid-infrared spectrum) absorbing two-dimensional material, and its optical response characteristics can be adjusted by external bias voltage. Place two layers of graphene on the upper surface of the ridge-shaped optical waveguide layer or embedded in the middle of the optical waveguide layer and extend to both sides of the ridge-shaped optical waveguide layer to connect the first electrodes to the first pillar and the second pillar respectively and the second electrode, by applying a bias voltage to modulate the Fermi level of graphene to adjust its optical response characteristics, change the complex effective refractive index of the ridge optical waveguide, the real part of the complex effective refractive index corresponds to the change of the optical phase, and the complex The imaginary part of the effective refractive index corresponds to the absorption of light. For different incident wavelengths, the imaginary part of the complex effective refractive index of the ridge optical waveguide corresponding to different specific bias voltage points will be relatively large, that is, the optical loss of the ridge optical waveguide will be large, and the optical signal can hardly pass through. It can be used as the "OFF" state; at other bias voltage points, the optical loss of the ridge-shaped optical waveguide layer will be small, and the optical signal can pass through almost without loss, and it can be used as the "ON" state. 1.55 ~ 3μm near-mid-infrared spectral signal modulation function. Since the graphene material has ultra-fast carrier mobility, and the suspension of graphene between the ridge-shaped optical waveguide layer and the pillar can improve the graphene carrier mobility, the operating rate of the device can be further improved, The preparation process of the modulator of the present invention is compatible with the traditional SOICMOS process and has the advantage of easy integration.

Example 1

The three-dimensional structural diagram of the near-mid-infrared light modulator based on graphene-chalcogenide glass planar waveguide is shown in Figure 1; the near-mid-infrared light wavelength is 1.55-3 μm, including the base layer 1 and the ridge light set on the base layer 1 The waveguide layer 2, the first pillar 31 and the second pillar 32, the first pillar 31 and the second pillar 32 are arranged on the left and right sides of the ridge-shaped optical waveguide layer 2, and the ridge-shaped optical waveguide layer 2 is divided into first ridge-shaped The optical waveguide layer 21 and the second ridge optical waveguide layer 22 arranged on the first ridge optical waveguide layer 21, the first graphene layer 41 and the second graphene layer 42 are sequentially arranged on the first ridge optical waveguide layer 21 from bottom to top. Between the ridge-shaped optical waveguide layer 21 and the second ridge-shaped optical waveguide layer 22; the first graphene layer 41 extends to the upper surface of the first pillar 31, and the second graphene layer 42 extends to the upper surface of the second pillar 32, A first isolation dielectric layer 51 is arranged between the first ridge optical waveguide layer 21 and the first graphene layer 41, the first graphene layer 41 and the first pillar 31; the first graphene layer 41 and the first A second isolation medium layer 52 is arranged between the two graphene layers 42, the second graphene layer 42 and the second pillar 32; Three isolating dielectric layers 53 , the first electrode 61 is disposed on the first graphene layer 41 on the first pillar 31 , and the second electrode 62 is disposed on the second graphene layer 42 on the second pillar 32 . The material of the base layer 1 is SiO ₂ ; the width and height of the ridge optical waveguide layer 2 are 0.6 μm and 0.4 μm respectively, and the material As ₂ S ₃ is used; the first isolation dielectric layer 51, the second isolation dielectric layer 52 and The material of the third isolation dielectric layer 53 is boron nitride hBN; the thickness of the second isolation dielectric layer 52 is 15nm; material) composition.

Example 2

The three-dimensional structural diagram of the near-mid-infrared light modulator based on graphene-chalcogenide glass planar waveguide is shown in Figure 2; the near-mid-infrared light wavelength is 1.55-3 μm, including the base layer 1 and the ridge light set on the base layer 1 The waveguide layer 2, the first pillar 31 and the second pillar 32, the first pillar 31 and the second pillar 32 are arranged on the left and right sides of the ridge optical waveguide layer 2, the first graphene layer 41, the second graphene layer 42 are sequentially arranged on the upper surface of the ridge-shaped optical waveguide layer 2 from bottom to top; the first graphene layer 41 extends to the upper surface of the first pillar 31, and the second graphene layer 42 extends to the upper surface of the second pillar 32, A first isolation dielectric layer 51 is arranged between the ridge optical waveguide layer 2 and the first graphene layer 41, the first graphene layer 41 and the first pillar 31; the first graphene layer 41 and the second graphite A second insulating dielectric layer 52 is arranged between the ene layer 42, the second graphene layer 42 and the second pillar 32; a first electrode 61 is arranged on the first graphene layer 41 on the first pillar 31, and the second pillar 32 A second electrode 62 is disposed on the second graphene layer 42 on the top. The material of the base layer 1 is SiO ₂ ; the width and height of the ridge optical waveguide layer 2 are 0.6 μm and 0.4 μm respectively, and the material As ₂ S ₃ is used; the first isolation dielectric layer 51 and the second isolation dielectric layer 52 are The material is boron nitride hBN; the thickness of the second insulating dielectric layer 52 is 15nm; the material of the first electrode 61 and the second electrode 62 is composed of a layer of Au (gold material) plated on Pa (palladium material).

Fig. 3 shows the variation of the optical absorption coefficient of the TM mode in the ridge optical waveguide layer with the chemical potential energy of graphene when the incident light wavelengths are 1.55 μm, 2 μm, 2.5 μm, and 3 μm for the near-mid-infrared light modulator according to the embodiment of the present invention. Graph. It can be seen from the figure that the absorption peaks of different incident light wavelengths correspond to different bias voltage points, and the peak values of the light absorption coefficient (the imaginary part of the negative effective refractive index) corresponding to the incident wavelengths of 1.55 μm, 2 μm, 2.5 μm, and 3 μm are 0.06467 respectively . When the graphene chemical potential energy is 0.7eV, the optical modulator of the present invention has a very small absorption coefficient for incident light of 1.55-3 μm, on the order of ^10-5 , and the light attenuation is small when passing through the modulator, which can be regarded as the "ON" state.

Fig. 4 shows how the TM modes in the ridge optical waveguide layer are in the "ON" and "OFF" states respectively when the incident light wavelengths are 1.55 μm, 2 μm, 2.5 μm, and 3 μm in the near-mid-infrared light modulator according to the embodiment of the present invention. The graph of normalized power variation with transmission distance. It can be seen from the figure that in the "OFF" state, the incident light wavelengths of 1.55 μm and 2 μm attenuate to a very small value after passing through a transmission distance of 100 μm, and the incident light wavelengths of 2.5 μm and 3 μm require a longer transmission length to achieve To achieve a more ideal light attenuation. The calculation results show that when the incident light wavelengths are 1.55 μm, 2 μm, 2.5 μm, and 3 μm, the achievable extinction ratios of the graphene-chalcogenide glass optical modulator with a length of 400 μm are: >30dB, >30dB, 26dB, 11.3 dB.

The modulation rate of the optical modulator of the present invention is mainly limited by the RC constant, which can be expressed as f _3dB = 1/2πRC, because graphene itself has ultra-high carrier mobility, coupled with the ridge-shaped optical waveguide layer and pillars The graphene suspended between them can further improve the carrier mobility of graphene, so the RC constant of the light modulator of the present invention is a very small value, about 1.3×10 ^-12 , the calculation results show that the light modulation of the present invention The modulation rate of the device can be as high as 122GHz/bit.

Claims (10)

1. one kind based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterized in that: include basal layer, ridge optical waveguide layer on the base layer is set, first pillar and the second pillar, first pillar and the second pillar are separately positioned on the both sides of ridge optical waveguide layer, ridge optical waveguide layer is provided with the first graphene layer and the second graphene layer, first graphene layer extends to the upper surface of the first pillar, second graphene layer extends to the upper surface of the second pillar, at ridge optical waveguide layer and the first graphene layer and the second graphene layer, first graphene layer and the second graphene layer, first graphene layer and the first pillar, spacer medium layer it is respectively arranged with between second graphene layer and the second pillar, the first graphene layer on first pillar is provided with the first electrode, the second graphene layer on second pillar is provided with the second electrode。

2. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterized in that: described ridge optical waveguide layer is divided into the first ridge optical waveguide layer and the second ridge optical waveguide layer being arranged on the first ridge optical waveguide layer, and described first graphene layer, the second graphene layer are successively set between the first ridge optical waveguide layer and the second ridge optical waveguide layer from top to bottom；Spacer medium layer between described first ridge optical waveguide layer and the first graphene layer, the first graphene layer and the first pillar is the first spacer medium layer；Spacer medium layer between described first graphene layer and the second graphene layer, the second graphene layer and the second pillar is the second spacer medium layer；Spacer medium layer between described second graphene layer and the second ridge optical waveguide layer is the 3rd spacer medium layer。

3. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterized in that: described first graphene layer, the second graphene layer are successively set on the upper surface of ridge optical waveguide layer from top to bottom, the spacer medium layer between described ridge optical waveguide layer and the first graphene layer, the first graphene layer and the first pillar is the first spacer medium layer；Spacer medium layer between described first graphene layer and the second graphene layer, the second graphene layer and the second pillar is the second spacer medium layer。

4. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterised in that: the material of described basal layer is silicon dioxide。

5. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterised in that: the material of described ridge optical waveguide layer is chalcogenide glass material。

6. one according to claim 5 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterized in that: described chalcogenide glass material is the compound glass formed with other metals and nonmetalloid as anion by the group vi element except O, it is possible to be Ge₂₃Sb₇S₇₀、As₂Se₃、As₂S₃One of material。

7. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterised in that: described first pillar, the second pillar and basal layer form groove structure, and ridge optical waveguide layer is arranged in groove structure。

8. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterised in that: the thickness of described spacer medium layer is 5～60nm。

9. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterised in that: described spacer medium layer is one of insulant such as Si oxide, silicon nitrogen oxides, boron nitride。

10. one according to claim 1 is based on the nearly mid-infrared light manipulator of Graphene chalcogenide glass planar waveguide-type, it is characterized in that: described first electrode and the second electrode are made up of materials at two layers, ground floor is the material contacted with the first graphene layer and the second graphene layer, the second layer is arrange material on the first layer, the material of ground floor is the one in titanium, nickel, cobalt, palladium, and the material of the second layer is the one in gold, silver, platinum, copper product。