CN114609804A - Chip integrated all-optical modulation method based on photo-generated free carriers - Google Patents

Abstract

The invention discloses a chip integrated all-optical modulation method based on photo-generated free carriers.A pumping light field enters an optical modulator through a directional coupler, the free carriers are generated through a two-photon absorption effect, the refractive index of a transmission waveguide is changed, and the phase of a signal light field is effectively modulated along with the change of the refractive index. The method is based on the relatively mature chip integrated optical path preparation process at the present stage, can be prepared by one-time exposure etching, simultaneously has the advantages of high modulation rate, low insertion loss, high mechanical stability, high preparation efficiency and the like, and is expected to be widely applied to a very large-scale chip integrated photoelectric system.

Description

Chip integrated all-optical modulation method based on photo-generated free carriers

Technical Field

The invention belongs to the interdisciplinary field of integrated optics, semiconductor physics and microwave photonics, in particular to a method for realizing high-speed modulation of a signal square phase by adjusting a refractive index of a chip integrated waveguide through generating free carriers by a pumping light field, and particularly relates to a chip integrated all-optical modulation method, system and storage medium based on photo-generated free carriers.

Background

Optoelectronic information systems are generally composed of a series of discrete optoelectronic devices capable of performing a variety of complex functions; common photoelectric information systems comprise an optical communication system, an optical switching system, an optical computer, an all-optical signal processing system, a microwave optical subsystem and the like, are mainly constructed through a free space optical path or an all-optical fiber optical path, have large volume, poor stability, difficult coordination control and slow upgrading and updating rate, and are difficult to be applied in large scale in the outdoor environment of a laboratory. On the other hand, due to the rapid development of the preparation process of the precise micro-nano device, a large number of chip integrated photoelectric devices including an optical modulator, an optical filter, an optical attenuator, a directional coupler, a polarization beam splitter, a wavelength division multiplexer and the like have performance indexes similar to those of discrete photoelectric devices, and a solid foundation is laid for the integration of a single chip photoelectric information system.

The optical modulator plays an important role in a series of applications such as an optical communication coding and decoding system, an optical interferometer, a phased array radar and the like, and particularly the chip integrated optical modulator mainly focuses on two performance indexes, namely modulation rate and a preparation process. The thermo-optic modulation method generally adopted at the present stage is limited by dissipation time, and the kHz magnitude is difficult to break through; the electro-optic modulation method based on the P-I-N structure requires special processes such as ion implantation, chemical vapor deposition and the like, and the higher modulation voltage can cause waveguide breakdown; the electro-optical modulation method based on the graphene two-dimensional layered material can shorten the service life of free carriers and improve the modulation rate, but the cladding structure introduces huge transmission loss.

Disclosure of Invention

Based on the problems of the prior art, the technical problem to be solved by the invention is how to prepare the optical modulator by the silicon-on-insulator standard process; leading an X-waveband pumping optical field carrying a modulation signal into an optical modulator through a directional coupler; the pumping light field generates free carriers under the action of two-photon absorption and changes the refractive index of the transmission waveguide; and the phase of the optical field of the Y-waveband signal is repeatedly etched along with the change of the refractive index to modulate the signal to realize all-optical modulation.

In order to achieve the above effect, the chip integrated all-optical modulation method based on photo-generated free carriers provided by the invention comprises the following steps:

step one, pump light field modulation coupling, wherein a modulation signal is loaded in an X wave band pump light field and is coupled into an optical modulator through a directional coupler;

step two, signal light field modulation, wherein the pumping light field generates free carriers under the action of two-photon absorption to cause the change of the refractive index of the transmission waveguide and realize effective modulation of the phase of the Y-waveband signal light field; the optical modulator uses the pump optical field as a driving source and is composed of all passive optical devices.

Preferably, the method specifically comprises:

s101, preparing an optical modulator through a silicon-on-insulator standard process, and simultaneously transmitting a silicon-based waveguide of an X-waveband pumping light field and a Y-waveband signal light field, and a directional coupler with the largest cross coupling coefficient of the X-waveband pumping light field and the smallest cross coupling coefficient of the Y-waveband signal light field;

s102, guiding the modulated X-waveband pump light field into an optical modulator through a directional coupler and combining and transmitting the modulated X-waveband pump light field and an unmodulated Y-waveband signal light field;

s103, generating free carriers in the pumping light field under the action of two-photon absorption, changing the refractive index of the transmission waveguide, and modulating the phase distribution of the signal light field.

Preferably, in S101, the cross-sectional structure of the waveguide is optimally designed, so that the transmission loss is low, the free carrier lifetime is short, the refractive index of the waveguide is sensitive to change, and the length of the waveguide is optimally designed to achieve both low transmission loss and large modulation depth.

Preferably, the pump optical field and the signal optical field in S102 have the same repetition frequency, similar propagation constants, and a near-zero timing mismatch.

Preferably, the S103 may further convert the phase modulation into an intensity modulation, a polarization modulation, or a mode modulation through a specific optical path.

Preferably, the modulated X-waveband pump optical field and the unmodulated Y-waveband signal optical field are respectively coupled into the silicon-based waveguide through the grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pump light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler.

Preferably, the pumping optical field generates free carriers under the two-photon absorption action of the silicon-based waveguide, changes the refractive index of the silicon-based waveguide and realizes phase modulation of a signal optical field; the residual pump optical field is led out through another directional coupler; and the signal optical field which is subjected to phase modulation and the signal optical field which is not subjected to phase modulation interfere to output an intensity modulation signal.

Preferably, the directional coupler is composed of two parallel waveguides, the length, width and spacing of the waveguides are designed, the pumping optical field of the X waveband can be evanescently coupled between the two waveguides, and the signal optical field of the Y waveband does not generate evanescently coupling.

A system for realizing the chip integrated all-optical modulation method based on the photo-generated free carriers comprises a grating coupler, a silicon-based waveguide, an optical beam splitter, a Mach-Zehnder interferometer and a directional coupler, and also comprises:

the pump optical field modulation coupling subsystem is used for loading a modulation signal in an X-waveband pump optical field and coupling the modulation signal into the optical modulator through the directional coupler;

the signal light field modulation subsystem is used for generating free carriers in a pumping light field under the action of two-photon absorption, causing the change of the refractive index of the transmission waveguide and realizing the effective modulation of the phase of a Y-waveband signal light field;

the optical modulator takes a pumping optical field as a driving source and is completely composed of passive optical devices (i.e. does not contain external electrodes);

the system comprises a silicon-based waveguide, a grating coupler, a Y-band signal optical field and an X-band pump optical field, wherein the X-band pump optical field and the Y-band signal optical field are modulated and are respectively coupled into the silicon-based waveguide through the grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pump light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler; the pumping light field generates free carriers under the action of two-photon absorption of the silicon-based waveguide, the refractive index of the silicon-based waveguide is changed, and phase modulation of a signal light field is realized; the residual pump optical field is led out through another directional coupler; interfering the signal light field subjected to phase modulation and the signal light field not subjected to phase modulation to output an intensity modulation signal;

the directional coupler is composed of two parallel waveguides, the length, width and distance of the waveguides are designed, the X-waveband pumping optical field can be subjected to evanescent coupling between the two waveguides, and the Y-waveband signal optical field is not subjected to evanescent coupling.

A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the above-mentioned method.

Compared with the prior art, the method provided by the invention has the advantages that the pumping light field enters the optical modulator through the directional coupler, free carriers are generated through the two-photon absorption effect, the refractive index of the transmission waveguide is changed, and the phase of the signal light field is effectively modulated along with the change of the refractive index. The method is based on the relatively mature chip integrated optical path preparation process at the present stage, can be prepared by one-time exposure etching, simultaneously has the advantages of high modulation rate, low insertion loss, high mechanical stability, high preparation efficiency and the like, and is expected to be widely applied to a very large-scale chip integrated photoelectric system.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 shows a schematic diagram of the chip integrated all-optical modulation principle based on photo-generated free carriers.

Detailed Description

Features and exemplary embodiments of various aspects of the present invention will be described in detail below, and in order to make objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The invention provides an embodiment of a chip integrated all-optical modulation method based on photo-generated free carriers, which comprises the following steps:

step one, pump light field modulation coupling, loading a modulation signal in an X-waveband pump light field, and coupling the modulation signal into an optical modulator through a directional coupler;

step two, signal light field modulation, wherein the pumping light field generates free carriers under the action of two-photon absorption to cause the change of the refractive index of the transmission waveguide and realize effective modulation of the phase of the Y-waveband signal light field; the optical modulator uses the pump optical field as a driving source and is composed of all passive optical devices.

In some embodiments, the method specifically comprises:

s101, preparing an optical modulator through a silicon-on-insulator standard process, and simultaneously transmitting a silicon-based waveguide of an X-waveband pumping light field and a Y-waveband signal light field, and a directional coupler with the largest cross coupling coefficient of the X-waveband pumping light field and the smallest cross coupling coefficient of the Y-waveband signal light field;

s102, guiding the modulated X-waveband pump light field into an optical modulator through a directional coupler and combining and transmitting the modulated X-waveband pump light field and an unmodulated Y-waveband signal light field;

s103, generating free carriers in the pumping light field under the action of two-photon absorption, changing the refractive index of the transmission waveguide, and modulating the phase distribution of the signal light field.

In some embodiments, the waveguide cross-sectional structure is optimally designed in S101, so that the transmission loss is low, the free carrier lifetime is short, the waveguide refractive index is sensitive to change, and the waveguide length is optimally designed to take account of the low transmission loss and the large modulation depth.

In some embodiments, the pump optical field and the signal optical field in S102 need to have the same repetition frequency, similar propagation constants, and near-zero timing mismatch.

In some embodiments, S103 may also convert the above phase modulation into intensity modulation, polarization modulation, or mode modulation through a specific optical path.

In some embodiments, the modulated X-band pump optical field and the unmodulated Y-band signal optical field are respectively coupled into the silicon-based waveguide through a grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pump light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler; the pumping light field generates free carriers under the action of two-photon absorption of the silicon-based waveguide, the refractive index of the silicon-based waveguide is changed, and phase modulation of a signal light field is realized; the residual pump optical field is led out through another directional coupler; and the signal optical field which is subjected to phase modulation and the signal optical field which is not subjected to phase modulation interfere to output an intensity modulation signal.

In some embodiments, the directional coupler is composed of two parallel waveguides, the length, width and spacing of the waveguides are designed such that the X-band pump optical field can be evanescently coupled between the two waveguides and the Y-band signal optical field is not evanescently coupled.

The invention provides a system embodiment for realizing the chip integrated all-optical modulation method based on the photo-generated free carriers, which comprises a grating coupler, a silicon-based waveguide, an optical beam splitter, a Mach-Zehnder interferometer and a directional coupler, and further comprises:

the pump optical field modulation coupling subsystem is used for loading a modulation signal in an X-waveband pump optical field and coupling the modulation signal into the optical modulator through the directional coupler;

the signal light field modulation subsystem is used for generating free carriers in a pumping light field under the action of two-photon absorption, causing the change of the refractive index of the transmission waveguide and realizing the effective modulation of the phase of a Y-waveband signal light field;

in some embodiments, the optical modulator uses the pump light field as a drive source and is composed entirely of passive optical devices (i.e., without external electrodes);

in some embodiments, a modulated X-band pump optical field and an unmodulated Y-band signal optical field of the system are respectively coupled into the silicon-based waveguide through the grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pump light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler; the pumping light field generates free carriers under the action of two-photon absorption of the silicon-based waveguide, the refractive index of the silicon-based waveguide is changed, and phase modulation of a signal light field is realized; the residual pumping optical field is led out through another directional coupler; interfering the signal light field subjected to phase modulation and the signal light field not subjected to phase modulation to output an intensity modulation signal;

in some embodiments, the directional coupler is composed of two parallel waveguides, the length, width and spacing of the waveguides are designed so that the pump light field in the X-band can be evanescently coupled between the two waveguides, and the signal light field in the Y-band is not evanescently coupled.

As shown in fig. 1, the present invention provides an all-optically driven chip integrated mach-zehnder interferometer based on a silicon-on-insulator fabrication process, which is used to describe the chip integrated all-optical modulation principle based on a photo-generated free carrier: the modulated X-waveband pumping optical field and the unmodulated Y-waveband signal optical field are respectively coupled into the silicon-based waveguide through the grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pumping light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler (the directional coupler is composed of two parallel waveguides, the length, the width and the distance of the waveguides are finely designed, the X-waveband pumping light field can be subjected to evanescent coupling between the two waveguides, and the Y-waveband signal light field is hardly subjected to evanescent coupling); the pumping light field generates free carriers under the action of two-photon absorption of the silicon-based waveguide, the refractive index of the silicon-based waveguide is changed, and phase modulation of a signal light field is realized; the residual pump optical field is led out through another directional coupler; and the signal optical field which is subjected to phase modulation and the signal optical field which is not subjected to phase modulation interfere to output an intensity modulation signal. It should be noted that fig. 1 only shows the basic principles of phase modulation and intensity modulation, and the all-optical modulation method of the present invention can also be used to implement polarization modulation, mode field modulation, etc.

The invention provides an embodiment of a chip integrated all-optical modulation method based on photo-generated free carriers.

In some embodiments, the chip integrated waveguide can be prepared by a standard chip integrated optical circuit process, has a certain degree of structural design freedom, can efficiently and losslessly transmit an optical field, and can generate refractive index change under the action of free carriers, and the material platform used by the chip integrated waveguide comprises but is not limited to silicon on insulator, hydrogen-loaded amorphous silicon, silicon nitride, silicon carbide, chalcogenide glass, III-V group AlGaAs, III-V group InP and the like, and can adopt a single material integration method or a multi-material mixed integration method;

in some embodiments, the pump optical field is located in the X-band, where high concentration of free carriers (high refractive index variation) needs to be generated in the chip integrated waveguide at low power, and can be generated by a pulsed laser in either external modulation (modulation after generation of laser pulses) or internal modulation (direct output of modulated pulses); the signal light field is positioned in a Y wave band and needs to be transmitted in the chip integrated waveguide with low loss, and the signal light field can be continuous light, pulse light or a single photon sequence; the pump and signal fields need to have the same repetition frequency, similar propagation constants, and near-zero timing mismatch.

In some embodiments, the directional coupler needs to include two input ends and one output end, the pump light field and the signal light field are input from the input ends, the pump light field is merged with the signal light field through evanescent wave coupling and transmitted and output from the output end, the cross-coupling coefficient of the pump light field is maximum, the cross-coupling coefficient of the signal light field is minimum, and the specific structural parameters of the directional coupler are not limited.

In some embodiments, a pumping light field and a signal light field in an optical modulator are synchronously transmitted in a transmission waveguide in the optical modulator, the relative phase of the signal light field is influenced by the change of the refractive index caused by free carriers generated by the pumping light field, the cross section structure of the waveguide needs to be optimally designed so that the transmission loss is lower, the service life of the free carriers is shorter, the change of the refractive index of the waveguide is sensitive, and the length of the waveguide needs to be optimally designed so as to take account of the low transmission loss and the large modulation depth; the phase modulation can also be converted into intensity modulation, polarization modulation, mode modulation, and the like through a specific optical path.

The invention provides an embodiment of a chip integrated all-optical modulation method based on photo-generated free carriers, in particular to an all-optical modulation method which irradiates a modulated pumping light field to the upper surface of a transmission waveguide along the direction vertical to a chip to trigger the change of the refractive index caused by the free carriers.

Compared with the prior art, the invention has the following advantages:

firstly, the all-optical modulation method does not use chip electrodes and external voltage, does not need special processes such as ion implantation (P-I-N structure), vapor deposition and the like, simultaneously avoids the problem of waveguide breakdown caused by overhigh modulation voltage, and has simple structure, reliable performance and easy realization;

secondly, the maximum modulation rate of the all-optical modulation method depends on the free carrier dissipation rate, the service life of the free carrier can be reduced and the rate bottleneck can be broken through the optimization of a waveguide structure, and the modulation rate is far higher than that of the currently and generally adopted thermo-optical modulation method;

in addition, the invention provides a brand new technical idea for integrated large-scale light field regulation and control, and related design concepts are expected to be widely applied in the fields of all-optical communication signal wavelength conversion, optical neural networks, optical phased arrays and the like.

For convenience of description, the above devices are described as being divided into various units by function, and are described separately. Of course, the functionality of the units may be implemented in one or more software and/or hardware when implementing the present application.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The application may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The application may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.

The memory may include forms of volatile memory in a computer readable medium, Random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of a computer-readable medium.

Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims (10)

1. A chip integrated all-optical modulation method based on photo-generated free carriers comprises the following steps:

step one, pump light field modulation coupling, loading a modulation signal in an X-waveband pump light field, and coupling the modulation signal into an optical modulator through a directional coupler;

step two, signal light field modulation, wherein the pumping light field generates free carriers under the action of two-photon absorption to cause the change of the refractive index of the transmission waveguide and realize the effective modulation of the phase of the Y-waveband signal light field; the optical modulator uses the pump optical field as a driving source and is composed of all passive optical devices.

2. The method according to claim 1, characterized in that it comprises in particular:

s101, preparing an optical modulator through a silicon-on-insulator standard process, and simultaneously transmitting a silicon-based waveguide of an X-waveband pump light field and a Y-waveband signal light field, and a directional coupler with the largest cross coupling coefficient of the X-waveband pump light field and the smallest cross coupling coefficient of the Y-waveband signal light field;

s102, guiding the modulated X-waveband pump light field into an optical modulator through a directional coupler and combining and transmitting the modulated X-waveband pump light field and an unmodulated Y-waveband signal light field;

s103, generating free carriers in the pumping light field under the action of two-photon absorption, changing the refractive index of the transmission waveguide, and modulating the phase distribution of the signal light field.

3. The chip integrated all-optical modulation method based on the photogenerated free carriers according to claim 2, wherein the waveguide cross-section structure is optimally designed in S101, so that the transmission loss is low, the free carrier life is short, the waveguide refractive index change is sensitive, and the waveguide length is optimally designed to take account of the low transmission loss and the large modulation depth.

4. The chip integrated all-optical modulation method based on photogenerated free carriers according to claim 2, characterized in that the pump optical field and the signal optical field in S102 need to have the same repetition frequency, similar propagation constants and near-zero timing mismatch.

5. The chip integrated all-optical modulation method based on photogenerated free carriers according to claim 2, characterized in that the S103 further converts the phase modulation into intensity modulation, polarization modulation or mode modulation through a specific optical path.

6. The chip integrated all-optical modulation method based on photo-generated free carriers according to one of claims 1 to 5, characterized in that the modulated X-band pump optical field and the unmodulated Y-band signal optical field are respectively coupled into the silicon-based waveguide through a grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pump light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler.

7. The chip integrated all-optical modulation method based on photogenerated free carriers according to claim 6, characterized in that the pumping optical field generates free carriers under the two-photon absorption effect of the silicon-based waveguide, changes the refractive index of the silicon-based waveguide and realizes the phase modulation of the signal optical field; the residual pump optical field is led out through another directional coupler; and the signal optical field which is subjected to phase modulation and the signal optical field which is not subjected to phase modulation interfere to output an intensity modulation signal.

8. The on-chip integrated all-optical modulation method based on photogenerated free carriers according to claim 7, wherein the directional coupler is composed of two parallel waveguides, the length, width and distance of the waveguides are designed, the pumping optical field of the X waveband can be evanescently coupled between the two waveguides, and the signal optical field of the Y waveband can not be evanescently coupled.

9. A system for implementing the chip integrated all-optical modulation method based on photo-generated free carriers according to claims 1-8, comprising a grating coupler, a silicon-based waveguide, an optical beam splitter, a mach-zehnder interferometer and a directional coupler, and further comprising:

the pump optical field modulation coupling subsystem is used for loading a modulation signal in an X-waveband pump optical field and coupling the modulation signal into the optical modulator through the directional coupler;

the signal light field modulation subsystem is used for generating free carriers in a pumping light field under the action of two-photon absorption, causing the change of the refractive index of the transmission waveguide and realizing the effective modulation of the phase of a Y-waveband signal light field;

the optical modulator takes a pumping optical field as a driving source and is completely composed of passive optical devices (i.e. without external electrodes);

the system comprises a silicon-based waveguide, a grating coupler, a Y-band signal optical field and an X-band pump optical field, wherein the X-band pump optical field and the Y-band signal optical field are modulated and are respectively coupled into the silicon-based waveguide through the grating coupler; the signal light field is divided to two arms of the Mach-Zehnder interferometer through the optical beam splitter; the pump light field is coupled into one arm of the Mach-Zehnder interferometer through the directional coupler; the pumping light field generates free carriers under the action of two-photon absorption of the silicon-based waveguide, the refractive index of the silicon-based waveguide is changed, and phase modulation of a signal light field is realized; the residual pump optical field is led out through another directional coupler; interfering the signal light field subjected to phase modulation and the signal light field not subjected to phase modulation to output an intensity modulation signal;

the directional coupler is composed of two parallel waveguides, the length, width and distance of the waveguides are designed, the X-waveband pumping optical field can be subjected to evanescent coupling between the two waveguides, and the Y-waveband signal optical field is not subjected to evanescent coupling.

10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method of any one of claims 1 to 8.

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