On-chip chalcogenide inverted ridge type optical waveguide and Bragg grating preparation method thereof

Abstract

The invention relates to the technical field of chalcogenide photonics, and discloses an on-chip chalcogenide inverted-ridge optical waveguide and a Bragg grating preparation method thereof.The on-chip chalcogenide inverted-ridge optical waveguide comprises a substrate layer and a waveguide layer arranged on the substrate layer, the waveguide layer comprises a transverse flat plate layer and a longitudinal ridge part, and the flat plate layer and the ridge part are integrally formed and are in a T shape; the ridge part of the waveguide layer is embedded into the substrate layer to form an inverted ridge type optical waveguide structure; wherein the waveguide layer is made of As2S3, and the substrate layer is made of SiO2; the Bragg grating on the waveguide layer is formed by using band gap light with the wavelength of 443 nm as an exposure source, irradiating from the surface of the flat plate layer of the waveguide layer and inscribing on the ridge part of the waveguide layer. The Bragg grating is prepared on the submicron on-chip chalcogenide ridge-type optical waveguide with the inverted structure, so that the submicron on-chip chalcogenide ridge-type optical waveguide has the characteristics of submicron size and better spectral performance, and can meet the requirements of an integrated photonic device on miniaturization, integration and high efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of chalcogenide photonics, and in particular to an on-chip chalcogenide inverted ridge optical waveguide and a method for preparing a Bragg grating thereof. Background Art

[0002] Chalcogenide photonics has become one of the most active frontiers in the research and development of photonic functional devices in the world. Its integrated photonic devices have attracted much attention in the field of integrated photonic device research in recent years. They have the advantages of multi-spectral band, low threshold and multi-functional integration in the application of optical information processing chips and systems, and can realize supercontinuum spectroscopy, Brillouin scattering, wavelength conversion and other functions. Chalcogenide glass is made of chalcogenide elements S, Se, Te, combined with other elements such as As, Sb, Ge, Ga, etc. It has excellent optical properties such as high linear refractive index and extremely high nonlinear refractive index, ultrafast nonlinear response, and a wide infrared transmission window. It is a new type of matrix material for integrated photonic devices in the near and mid-infrared band. Chalcogenide optical waveguides are the key foundation of chalcogenide integrated photonic device chips. They are constructed as linear devices and can be used for optical transmission and infrared sensing in the near and mid-infrared band; and they are constructed as nonlinear devices with a 10% higher performance than quartz glass. 2 ~10 3 times the optical nonlinear coefficient, and because chalcogenide glass has a high elasto-optic coefficient (10 times that of silicon material), extremely excellent acoustic mode confinement ability, extremely low two-photon absorption coefficient in the optical communication band, and no free carrier effect, it exhibits low nonlinear loss and other advantages. It is widely used in achieving high-gain stimulated Brillouin scattering.

[0003] The Bragg grating based on chalcogenide optical waveguide has a wide range of application prospects in the fields of mid-infrared optical sensing, optical filters, lasers, coherent optical communication systems, precision spectroscopy and microwave photonics. At the same time, because the size of the chalcogenide waveguide grating is submicron, it can be integrated on the chip, which is suitable for the needs of on-chip integration and miniaturization of devices. At present, there is little research on the preparation of Bragg grating chips based on chalcogenide optical waveguides, mainly because the preparation process of chalcogenide optical waveguides with traditional structures is cumbersome and the transmission loss is high, about 0.5 to 5 dB / cm, resulting in poor grating quality and poor spectral performance. Summary of the invention

[0004] The purpose of the present invention is to provide an on-chip chalcogenide inverted ridge optical waveguide and a method for preparing a Bragg grating thereof, and to prepare a Bragg grating on an inverted submicron on-chip chalcogenide ridge optical waveguide, which has the characteristics of submicron size and better spectral performance, and can meet the requirements of integrated photonic devices for miniaturization, integration, and high efficiency.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] An on-chip chalcogenide inverted ridge optical waveguide comprises a substrate layer and a waveguide layer arranged on the substrate layer, wherein the waveguide layer comprises a transverse planar layer and a longitudinal ridge portion, wherein the planar layer and the ridge portion are integrally formed and are T-shaped; the ridge portion of the waveguide layer is embedded in the substrate layer to form an inverted ridge optical waveguide structure;

[0007] Wherein, the waveguide layer is made of As2S3, and the substrate layer is made of SiO2;

[0008] The 443nm wavelength bandgap light is used as an exposure source to irradiate from the surface of the slab layer of the waveguide layer, thereby writing and forming a Bragg grating on the ridge of the waveguide layer.

[0009] Furthermore, the ridge portion of the waveguide layer has a ridge height H of 950 nm, a ridge width W of 1500 nm, and a ridge depth h of 800 nm.

[0010] The present invention also provides a method for preparing the Bragg grating of the on-chip chalcogenide inverted ridge optical waveguide as described above, comprising the following steps:

[0011] S1, preparing As2S3 chalcogenide glass film of set thickness by vacuum resistance heating evaporation method;

[0012] S2, using bandgap light with a wavelength of 443nm as the exposure source, studying the photosensitivity of As2S3 chalcogenide glass film under the action of bandgap light, and obtaining the law of refractive index changing with illumination time as the experimental data for photolithography grating writing;

[0013] S3, using a damascene-like inlay process, depositing an As2S3 chalcogenide glass film on the substrate layer according to the designed on-chip chalcogenide inverted ridge optical waveguide structure parameters to form a waveguide layer, thereby obtaining an on-chip chalcogenide inverted ridge optical waveguide;

[0014] S4, a grating writing system consisting of a Sagnac interferometer is built on an optical anti-vibration platform;

[0015] S5, in the grating writing system composed of Sagnac interferometer, based on the experimental data of grating writing in S2, 443nm wavelength bandgap light is used as the exposure source, and the surface of the planar layer of the waveguide layer obtained in S3 is irradiated to write a Bragg grating on the ridge of the waveguide layer.

[0016] Furthermore, in S1, the thickness is set to 1.8 μm.

[0017] Furthermore, in S4, the grating writing system composed of the Sagnac interferometer includes: a writing laser light source, a beam expansion collimation group, an attenuator, an aperture, an electronic shutter, a cylindrical lens, a ±1 diffraction level phase mask, two reflectors, a shading template, a waveguide chip holder, and a spectrum monitoring system, wherein the waveguide chip holder is used to clamp the on-chip chalcogenide inverted ridge optical waveguide;

[0018] The writing laser light source adopts He-Cd laser, and 443nm wavelength bandgap light is selected as the exposure source. The exposure source is expanded by a telescope system composed of a beam expansion lens group, an attenuator, an aperture, and an electronic shutter in sequence, and then passes through a cylindrical lens and enters a ±1 diffraction order phase mask plate to generate three diffraction orders of +1, 0, and -1, wherein the 0-order light beam is blocked, and the +1 and -1-order light beams are reflected twice by two reflectors tiltedly arranged above and below the on-chip chalcogenide inverted ridge optical waveguide, and finally focused on the surface of the flat layer of the on-chip chalcogenide inverted ridge optical waveguide to form a coherent focused light spot.

[0019] Furthermore, the focal length of the cylindrical lens is 60 cm.

[0020] Furthermore, the spectral monitoring system includes a single-mode optical fiber and an amplified spontaneous emission light source ASE and a spectrometer OSA connected to the single-mode optical fiber. The single-mode optical fiber is used to achieve end-face coupling with an on-chip chalcogenide inverted ridge optical waveguide. In the spectral monitoring system, a 1520-1700nm bandwidth amplified spontaneous emission light source ASE is selected and coupled into and out of the on-chip chalcogenide inverted ridge optical waveguide through the single-mode optical fiber, and the grating transmission spectrum is tested by the spectrometer OSA.

[0021] Further, the S5, in the grating writing system composed of a Sagnac interferometer, based on the experimental data of the grating written by photolithography in S2, uses 443nm wavelength bandgap light as an exposure source, irradiates the surface of the planar layer of the waveguide layer obtained in S3, and writes a Bragg grating on the ridge of the waveguide layer, specifically including:

[0022] S501, placing the on-chip chalcogenide inverted ridge optical waveguide on a waveguide chip holder, and achieving end-face coupling with a single-mode optical fiber placed on a precision displacement platform by a spectrum monitoring system;

[0023] S502, adjusting the optical path so that the light beam of the exposure source forms a coherent focused light spot with a height of 1 mm and a length of 8 mm on the surface of the flat layer of the waveguide layer;

[0024] S503, controlling the exposure source intensity through an attenuator, adjusting the angle between the two reflectors to change the interference angle to set the grating Bragg center wavelength;

[0025] S504, an electronic shutter controls the writing time to achieve refractive index modulation of the ridge, and forms a Bragg grating structure in the ridge of the on-chip chalcogenide inverted ridge optical waveguide; during the writing process, the spectrometer OSA monitors the grating transmission spectrum.

[0026] Further, the S503, controlling the intensity of the exposure source by an attenuator, adjusting the angle between the two reflectors to change the interference angle to set the grating Bragg center wavelength, specifically includes:

[0027] The intensities of the two beams emitted by the two reflectors are controlled by attenuators to be 4 mW each, and the angle between the two reflectors is adjusted to be approximately 88.5°.

[0028] Furthermore, in S504, the electronic shutter controls the writing time to be 65 seconds.

[0029] According to the specific embodiments provided by the present invention, the on-chip chalcogenide inverted ridge optical waveguide and the Bragg grating preparation method provided by the present invention disclose the following technical effects:

[0030] (1) A Bragg grating is prepared on an inverted on-chip As2S3 chalcogenide inverted ridge optical waveguide. The ridge of the waveguide layer is deposited in the substrate layer, and does not require demolding and packaging protective layers. It has low waveguide transmission loss (less than 0.2 dB / cm). In addition, when writing the grating, the exposure source is irradiated from the surface of the planar layer of the waveguide layer, which is different from the light source of the traditional ridge-type optical waveguide that irradiates from the ridge area surface.

[0031] (2) When preparing Bragg gratings on the As2S3 chalcogenide inverted ridge optical waveguide structure on a submicron-sized chip, the light penetration depth of the exposure source only needs to be 1.5 to 2 μm, so the 443nm wavelength bandgap light with high photosensitivity is selected as the exposure source. The writing time only takes tens of seconds. This is different from writing fiber gratings on chalcogenide glass fiber structures. The diameter of the commercial As2S3 optical fiber cladding is 140 to 170 μm, and the light penetration depth needs to be 70 to 85 μm. The exposure source generally needs to use a long wavelength light source far away from the bandgap light so that the light can reach the fiber core. This exposure source has weaker photosensitivity and the writing time is as long as tens of minutes or even hours.

[0032] (3) The 443nm wavelength bandgap light of chalcogenide glass was selected as the exposure source to prepare an on-chip As2S3 chalcogenide inverted ridge optical waveguide Bragg grating. The writing time was about 65s, and a high-quality grating spectrum was obtained. Its transmission peak reached about -28dB, the reflectivity was as high as 99.8%, and the grating bandwidth was about 0.95nm. The chalcogenide optical waveguide Bragg grating has good spectral performance and has broad application prospects in mid-infrared optical sensing, optical filters, lasers, coherent optical communication systems, precision spectroscopy and microwave photonics.

[0033] (4) The on-chip As2S3 sulfur-based inverted ridge optical waveguide Bragg grating prepared by the present invention has submicron dimensions (waveguide width W is about 950nm, ridge height H is about 1500nm, and ridge depth h is about 800nm), which meets the requirements of integrated photonic devices for miniaturization, integration, and high efficiency, and has the advantages of a chip-on-chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 A schematic diagram of the structure of an on-chip chalcogenide inverted ridge optical waveguide provided by the present invention;

[0036] Figure 2 The optical field and acoustic field distribution diagram of the on-chip chalcogenide inverted ridge optical waveguide provided by the present invention;

[0037] Figure 3 It is a curve diagram of the refractive index change of the As2S3 chalcogenide film of the present invention when irradiated with band gap light (443nm);

[0038] Figure 4 A schematic diagram of the structure of a grating writing system composed of a Sagnac interferometer of the present invention;

[0039] Figure 5 The transmission spectrum of the on-chip chalcogenide inverted ridge optical waveguide Bragg grating inscribed by the present invention;

[0040] Figure 6 Schematic diagram of the process of preparing on-chip As-S chalcogenide inverted ridge optical waveguide using a damascene-like damascene process;

[0041] Explanation of the reference numerals: 1. writing laser light source; 2. beam expansion and collimation group; 3. attenuator; 4. aperture layer; 5. electronic shutter; 6. cylindrical lens; 7. phase mask; 8. on-chip chalcogenide inverted ridge optical waveguide; 9. shading template; 10. single-mode optical fiber; 11. reflector. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The purpose of the present invention is to provide an on-chip chalcogenide inverted ridge optical waveguide and a method for preparing a Bragg grating thereof, and to prepare a waveguide Bragg grating on an on-chip submicron chalcogenide ridge optical waveguide with an inverted structure. The on-chip submicron chalcogenide ridge optical waveguide structure with an inverted structure is different from a traditional ridge optical waveguide structure. Its As2S3 chalcogenide ridge region (ridge) is buried in a SiO2 substrate, and is an inverted ridge optical waveguide structure. Moreover, since the ridge is inverted and buried in the substrate, no demoulding and packaging protective layer are required. Based on this structure, the present invention selects a 443nm wavelength bandgap light source of chalcogenide glass with high photosensitivity as an exposure source, and adopts a grating writing system composed of a Sagnac interferometer with a ±1 diffraction order phase mask with mechanical stability, to write a waveguide Bragg grating on the on-chip chalcogenide inverted ridge optical waveguide, and obtains a Bragg grating with good spectral quality, with a transmission peak reaching -28dB, a reflectivity as high as 99.8%, and a grating bandwidth of about 0.95nm.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figure 1 As shown, the on-chip chalcogenide inverted ridge optical waveguide provided by the present invention comprises a substrate layer and a waveguide layer arranged on the substrate layer, wherein the waveguide layer comprises a transverse planar layer and a longitudinal ridge portion, wherein the planar layer and the ridge portion are integrally formed and are T-shaped; the ridge portion of the waveguide layer is embedded in the substrate layer to form an inverted ridge optical waveguide structure;

[0046] The waveguide layer is made of As2S3, and the substrate layer is made of SiO2; the ridge of the As2S3 chalcogenide waveguide layer is inverted and buried in the SiO2 substrate;

[0047] The 443nm wavelength bandgap light is used as an exposure source to irradiate from the surface of the slab layer of the waveguide layer, thereby writing and forming a Bragg grating on the ridge of the waveguide layer.

[0048] For example, the ridge portion of the waveguide layer has a ridge height H of 950 nm, a ridge width W of 1500 nm, and a ridge depth h of 800 nm.

[0049] Figure 2 The distribution of light and sound fields carried by the on-chip chalcogenide inverted ridge optical waveguide shows that the waveguide light field is concentrated on the ridge, which meets the light field distribution required by the ridge-type optical waveguide. It also shows that there is a good overlap between the light and sound fields of the waveguide, which makes the interaction between light and sound very effective and is conducive to achieving a high-gain stimulated Brillouin effect.

[0050] On this waveguide structure, the grating is written using the photosensitivity law of chalcogenide glass. The on-chip chalcogenide inverted ridge optical waveguide structure of the present invention is different from the chalcogenide glass optical fiber structure. The chalcogenide glass optical fiber is a cylindrical structure, and its core and cladding components are similar, both of which are photosensitivity. The exposure source is selected to make the light penetration depth greater than the fiber cladding thickness. Generally, sub-bandgap light (such as 600-700nm wavelength) far away from the absorption edge of the chalcogenide glass material is used so that the light can reach the core. The diameter of the commercial As2S3 optical fiber cladding is 140-170μm, and the light penetration depth needs to reach 70-85μm. The ridge area depth of the sub-micron on-chip chalcogenide inverted ridge optical waveguide involved in the present invention is about 1.5-2μm, which is far lower than the range of 70-85μm. The bandgap light of the chalcogenide glass material can be selected as the exposure source, and the light can penetrate into the ridge area of ​​the waveguide without penetrating through. The present invention utilizes the photosensitivity law of chalcogenide glass to write gratings. Therefore, the present invention first experimentally studies the photosensitivity of an As2S3 chalcogenide glass film with a thickness of about 1.8 μm under the action of bandgap light, and selects a He-Cd laser as the irradiation light source, whose wavelength is 443 nm, which is in the bandgap light region of the As-S chalcogenide glass material. Figure 3 The refractive index change law of the As2S3 chalcogenide glass film with a thickness of about 1.8μm under the irradiation of the laser with a wavelength of 443nm shows high photosensitivity: at the beginning of irradiation, the refractive index changes significantly and shows good linearity with the illumination time. As the illumination time increases, the refractive index change reaches a saturation state. This shows that under the irradiation of the 443nm wavelength bandgap light, the high photosensitivity of the chalcogenide glass can be triggered and can penetrate the chalcogenide glass film with a thickness of several microns, which can ensure the formation of a grating structure in the chalcogenide ridge deposited in the substrate.

[0051] On the basis of the above, a mechanically stable Sagnac interferometer with ±1 diffraction order phase mask is used to write the As2S3 chalcogenide inverted ridge optical waveguide Bragg grating on the chip, such as Figure 4As shown, the system includes a writing laser light source 1 (using 443nm wavelength bandgap light of chalcogenide glass as the exposure source, for example, using He-Cd laser), a beam expansion collimator group 2, an attenuator 3, an aperture 4, an electronic shutter 5, a cylindrical lens 6, a phase mask plate 7 of ±1 diffraction order, a reflector 11, an on-chip chalcogenide inverted ridge optical waveguide 8 on a waveguide chip holder, a light shielding template 9, a spectrum monitoring system, etc. The advantage of the writing system is that the grating period can be changed by adjusting the angle between the two reflectors 11 to obtain the designed grating center wavelength, without having to replace the phase mask plate, and at the same time, the two beams of diffracted light with good intensity uniformity of the +1 and -1 levels of the phase mask plate are used to obtain a high contrast of interference fringes and a good quality of the written grating. In this system, in order to obtain a more uniform writing spot and have a larger space for placing the waveguide chip sample, a cylindrical lens with a focal length of 60cm is selected to form an interference spot with a height of about 1mm and a length of about 8mm on the waveguide flat plate layer. In the spectrum monitoring, a 1520-1700nm bandwidth amplified spontaneous emission light source ASE is selected, coupled into the on-chip chalcogenide waveguide chip through a high numerical aperture single-mode fiber, and the grating transmission spectrum is tested by a high-resolution spectrometer OSA. In addition to directly obtaining a uniform waveguide Bragg grating, this system can also be combined with a shading template to block part of the interference light on the grating structure to achieve phase shift and obtain a phase-shifted grating. In addition, because the inverted ridge region is buried in the substrate, the exposure source should be incident from the waveguide plate layer rather than from the ridge region surface, which is different from the traditional ridge-type optical waveguide grating. In this system, based on the experimental study of the photosensitivity law of thick As2S3 chalcogenide films under the action of bandgap light, a He-Cd laser with a wavelength of 443nm is selected as the writing laser light source, and appropriate exposure dose and other parameters are set.

[0052] Specifically, the present invention also provides a method for preparing the Bragg grating of the on-chip chalcogenide inverted ridge optical waveguide as described above, comprising the following steps:

[0053] S1, high-quality thick film As2S3 chalcogenide glass film was prepared by vacuum resistance heating evaporation method, and the surface root mean square roughness of the film was about 0.48nm and the film thickness was about 1.8μm;

[0054] S2, using bandgap light with a wavelength of 443nm as the exposure source, the photosensitivity of As2S3 chalcogenide glass film under the action of bandgap light was studied, and the law of change of refractive index with illumination time was obtained, such as Figure 3 As shown, it is the experimental data of photolithography writing grating;

[0055] S3, using a damascene-like inlay process, depositing an As2S3 chalcogenide glass film on the substrate layer according to the designed on-chip chalcogenide inverted ridge optical waveguide structure parameters to form a waveguide layer, and obtaining an on-chip chalcogenide inverted ridge optical waveguide; wherein, a damascene-like inlay process is used to prepare a high-quality thick-film on-chip As2S3 chalcogenide inverted ridge optical waveguide, achieving low-loss transmission (less than 0.2dB / cm), about 0.16dB / cm, and good optical transmission performance;

[0056] Among them, Figure 6 As shown in the figure, the specific steps of the Damascus-like inlay process are as follows: (1) Select a SiO2 material with high purity and good polishing quality as the substrate, and use the inductively coupled plasma (ICP) etching method to etch a micro-groove waveguide pattern with a smooth inner wall on the substrate, and the groove size meets the design requirements; (2) Use a degumming machine to remove the remaining photoresist on the substrate with the micro-groove waveguide pattern, and use a solvent to clean other residues or impurities, and then dry it in a vacuum hot oven to obtain an ultra-clean SiO2 substrate: (3) Use a vacuum resistance heating evaporation method to deposit a high-quality thick film of As2S3 sulfur-based film buried in the micro-groove of the SiO2 substrate to form an inverted ridge waveguide structure: (4) Since the deposition rate on the entire chip is the same, a concave shape will be formed at the groove on the waveguide surface, and a low-temperature hot pressing method is used to flatten the surface of the waveguide flat layer. At the same time, the low hot pressing temperature can avoid crystallization on the surface of the sulfur-based film, thereby greatly reducing the surface scattering loss.

[0057] This type of Damascus damascene process can be used to efficiently prepare on-chip As2S3 chalcogenide inverted ridge optical waveguides.

[0058] S4, a grating writing system composed of a Sagnac interferometer is built on an optical anti-vibration platform; the grating writing system composed of a Sagnac interferometer includes: a writing laser light source, a beam expansion and collimation group 2, an attenuator 3, an aperture 4, an electronic shutter 5, a cylindrical lens 6, a ±1 diffraction order phase mask 7, two reflectors 11, a light shielding template 9, an on-chip chalcogenide inverted ridge optical waveguide 8 on a waveguide chip holder, a spectrum monitoring system, etc.; the writing laser light source adopts a He-Cd laser 1, and a 443nm wavelength bandgap light is selected as an exposure source. The exposure source is expanded by a telescope system composed of a beam expansion lens group 2, an attenuator 3, an aperture 4, and an electronic shutter 5 in sequence, and then passes through a cylindrical lens 6 and enters a ±1 diffraction order phase mask 7 to generate +1, 0 , -1 third-order diffraction, wherein the 0th-order light beam is blocked, and the +1st and -1st-order light beams are reflected twice by two reflectors 11 tiltedly arranged above and below the on-chip chalcogenide inverted ridge optical waveguide, and finally focused on the flat layer surface of the on-chip chalcogenide inverted ridge optical waveguide to form a coherent focusing spot; the spectrum monitoring system comprises a single-mode optical fiber 10 and an amplified spontaneous emission light source ASE and a spectrometer OSA connected to the single-mode optical fiber 10, the single-mode optical fiber 10 is placed on a precision displacement platform, and is used to achieve end-face coupling with the waveguide on the waveguide chip holder, in the spectrum monitoring system, a 1520-1700nm bandwidth amplified spontaneous emission light source ASE is selected, coupled into and out of the on-chip chalcogenide inverted ridge optical waveguide through the single-mode optical fiber 10, and the spectrometer OSA tests the grating transmission spectrum;

[0059] S5, in a grating writing system composed of a Sagnac interferometer, based on the experimental data of the grating written by photolithography in S2, using 443nm wavelength bandgap light as an exposure source, irradiating the surface of the planar layer of the waveguide layer obtained in S3, and writing a Bragg grating on the ridge of the waveguide layer, specifically including:

[0060] S501, placing the on-chip chalcogenide inverted ridge optical waveguide on a waveguide chip holder, and achieving end-face coupling with a single-mode optical fiber placed on a precision displacement platform by a spectrum monitoring system;

[0061] S502, adjusting the optical path so that the light beam of the exposure source forms a coherent focused light spot with a height of 1 mm and a length of 8 mm on the surface of the flat layer of the waveguide layer;

[0062] S503, controlling the exposure source intensity through the attenuator 3, adjusting the angle between the two reflectors 11 to change the interference angle to set the grating Bragg center wavelength;

[0063] S504, the electronic shutter 4 controls the writing time to achieve refractive index modulation of the ridge, and forms a Bragg grating structure in the ridge of the on-chip chalcogenide inverted ridge optical waveguide; during the writing process, the spectrometer OSA monitors the grating transmission spectrum.

[0064] The step S503, controlling the intensity of the exposure source by means of the attenuator 3, adjusting the angle between the two reflectors 11 to change the interference angle to set the grating Bragg center wavelength, specifically includes:

[0065] The intensities of the two beams emitted by the two reflectors are controlled by attenuator 3 to be 4 mW each, and the angle between the two reflectors is adjusted to be approximately 88.5°.

[0066] In S504, the electronic shutter 4 controls the writing time to be 65 seconds.

[0067] Figure 5 The transmission spectrum of the on-chip chalcogenide inverted ridge optical waveguide Bragg grating obtained by the grating writing system composed of Sagnac interferometer in the present invention, the writing time is about 65s, the grating center wavelength is at 1555nm, the transmission peak reaches about -28dB, the reflectivity is as high as 99.8%, and the grating bandwidth is about 0.95nm. This shows that under the irradiation of 443nm wavelength bandgap light, an on-chip chalcogenide inverted ridge optical waveguide Bragg grating with good spectral quality and high reflectivity is obtained.

[0068] The on-chip As2S3 inverted-ridge optical waveguide Bragg grating provided by the present invention has a submicron size, meets the requirements of integrated photonic devices for miniaturization, integration, and high efficiency, and has the advantage of a chip-on-chip.

[0069] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An on-chip chalcogenide inverted ridge optical waveguide, comprising a substrate layer and a waveguide layer disposed on the substrate layer, characterized in that: The waveguide layer includes a transverse flat plate layer and a longitudinal ridge portion, wherein the flat plate layer and the ridge portion are integrally formed and are T-shaped; the ridge portion of the waveguide layer is embedded in the substrate layer to form an inverted ridge optical waveguide structure; Wherein, the waveguide layer is made of As2S3, and the substrate layer is made of SiO2; The Bragg grating on the waveguide layer is formed by using 443nm wavelength bandgap light as an exposure source, irradiating from the surface of the planar layer of the waveguide layer, and writing on the ridge of the waveguide layer.

2. The on-chip chalcogenide inverted ridge optical waveguide according to claim 1, characterized in that: The ridge portion of the waveguide layer had a ridge height H of 950 nm, a ridge width W of 1500 nm, and a ridge depth h of 800 nm.

3. A method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1, preparing As2S3 chalcogenide glass film of set thickness by vacuum resistance heating evaporation method; S2, using bandgap light with a wavelength of 443nm as the exposure source, studying the photosensitivity of As2S3 chalcogenide glass film under the action of bandgap light, and obtaining the law of refractive index changing with illumination time as the experimental data for photolithography grating writing; S3, using a damascene-like inlay process, depositing an As2S3 chalcogenide glass film on the substrate layer according to the designed on-chip chalcogenide inverted ridge optical waveguide structure parameters to form a waveguide layer, thereby obtaining an on-chip chalcogenide inverted ridge optical waveguide; S4, a grating writing system consisting of a Sagnac interferometer is built on an optical anti-vibration platform; S5, in the grating writing system composed of Sagnac interferometer, based on the experimental data of grating writing in S2, 443nm wavelength bandgap light is used as the exposure source, and the surface of the planar layer of the waveguide layer obtained in S3 is irradiated to write a Bragg grating on the ridge of the waveguide layer.

4. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 3, characterized in that: In the above S1, the thickness is set to 1.8 μm.

5. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 3, characterized in that: In S4, the grating writing system composed of the Sagnac interferometer includes: a writing laser light source, a beam expansion collimation group, an attenuator, an aperture, an electronic shutter, a cylindrical lens, a ±1 diffraction level phase mask, two reflectors, a shading template, a waveguide chip holder, and a spectrum monitoring system, wherein the waveguide chip holder is used to clamp the on-chip chalcogenide inverted ridge optical waveguide; The writing laser light source adopts He-Cd laser, and 443nm wavelength bandgap light is selected as the exposure source. The exposure source is expanded by a telescope system composed of a beam expansion lens group, an attenuator, an aperture, and an electronic shutter in sequence, and then passes through a cylindrical lens and enters a ±1 diffraction order phase mask plate to generate three diffraction orders of +1, 0, and -1, wherein the 0-order light beam is blocked, and the +1 and -1-order light beams are reflected twice by two reflectors tiltedly arranged above and below the on-chip chalcogenide inverted ridge optical waveguide, and finally focused on the surface of the flat layer of the on-chip chalcogenide inverted ridge optical waveguide to form a coherent focused light spot.

6. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 5, characterized in that: The focal length of the cylindrical lens is 60 cm.

7. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 5, characterized in that: The spectrum monitoring system includes a single-mode optical fiber and an amplified spontaneous emission light source ASE and a spectrometer OSA connected to the single-mode optical fiber. The single-mode optical fiber is used to achieve end-face coupling with an on-chip chalcogenide inverted ridge optical waveguide. In the spectrum monitoring system, a 1520-1700nm bandwidth amplified spontaneous emission light source ASE is selected and coupled into and out of the on-chip chalcogenide inverted ridge optical waveguide through the single-mode optical fiber, and the grating transmission spectrum is tested by the spectrometer OSA.

8. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 7, characterized in that: S5, in a grating writing system composed of a Sagnac interferometer, based on the experimental data of the grating written by photolithography in S2, uses 443nm wavelength bandgap light as an exposure source, irradiates the surface of the planar layer of the waveguide layer obtained in S3, and writes a Bragg grating on the ridge of the waveguide layer, specifically comprising: S501, placing the on-chip chalcogenide inverted ridge optical waveguide on a waveguide chip holder, and achieving end-face coupling with a single-mode optical fiber placed on a precision displacement platform by a spectrum monitoring system; S502, adjusting the optical path so that the light beam of the exposure source forms a coherent focused light spot with a height of 1 mm and a length of 8 mm on the surface of the flat layer of the waveguide layer; S503, controlling the exposure source intensity through an attenuator, adjusting the angle between the two reflectors to change the interference angle to set the grating Bragg center wavelength; S504, an electronic shutter controls the writing time to achieve refractive index modulation of the ridge, and forms a Bragg grating structure in the ridge of the on-chip chalcogenide inverted ridge optical waveguide; during the writing process, the spectrometer OSA monitors the grating transmission spectrum.

9. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 8, characterized in that: The S503, controlling the intensity of the exposure source by means of an attenuator, adjusting the angle between the two reflectors to change the interference angle to set the grating Bragg center wavelength, specifically includes: The intensities of the two beams emitted by the two reflectors are controlled by attenuators to be 4 mW each, and the angle between the two reflectors is adjusted to be approximately 88.5°.

10. The method for preparing a Bragg grating of an on-chip chalcogenide inverted ridge optical waveguide according to claim 8, characterized in that: In S504, the electronic shutter controls the writing time to be 65 seconds.

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