CN116125594A

CN116125594A - Broadband on-chip beam combining device

Info

Publication number: CN116125594A
Application number: CN202310085182.6A
Authority: CN
Inventors: 王瑞军; 王贤耿
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2023-02-08
Filing date: 2023-02-08
Publication date: 2023-05-16

Abstract

The invention belongs to the field of photonic integrated chips, and particularly relates to a broadband on-chip beam combining device. An active in-band beam combining device and an ultra-wide band beam combining device which are formed by Mach-Zehnder interferometers. The device is composed of a plurality of input ports, a part of which is long wavelength and a part of which is short wavelength. The input optical wavelength may be any wavelength within the bandwidth of the multimode interference coupler. By powering on the heating arm of the active in-band beam combining device, push-pull output can be achieved. The ultra-wide bandwidth beam combining device has high power, small loss and large bandwidth, and can realize on-chip beam combining with wavelength intervals of thousands of nanometers. The broadband on-chip beam combining device provided by the invention has the advantages of high power, small loss and large bandwidth, can realize beam combining with wavelength intervals of thousands of nanometers, and has the advantages of push-pull output, compact structure and small area.

Description

Broadband on-chip beam combining device

Technical Field

The invention belongs to the field of photonic integrated chips, and particularly relates to a broadband on-chip beam combining device.

Background

With the increasing maturity of semiconductor processing technology, one is gradually bonding chips of different wavelengths to the same substrate. Thus, laser beam combining devices become a key component for achieving multi-wavelength, broadband and high power lasers. The laser beam combining plays a vital role in improving the power, efficiency and beam quality of various laser systems, and is applied to the fields of long-distance free space optical communication, material processing and the like. There are two methods for realizing laser beam combining, namely coherent beam combining and wavelength beam combining. The coherent beam combination is to combine the two coherent interference beams by utilizing the phase difference generated by the two light beams, and is suitable for a smaller wavelength range. Wavelength combining typically requires combining lasers of different wavelengths through a waveguide array grating or filter, which has the advantage that no precise phase relationship is used and wide bandwidth combining is possible.

The devices for realizing wavelength beam combination are mainly three types, namely a Directional Coupler (DC), a multimode interference coupler (MMI) and a waveguide array grating (AWG).

The Directional Coupler (DC) is composed of two parallel waveguides, and the field intensity is oscillated between the two waveguides by the pi phase difference between the two different modes. The directional coupler is the most common mode for realizing light splitting and light combining in an optical fiber system, has small additional loss, simple structure and small bandwidth and process tolerance, and has the advantage of high sensitivity of light splitting ratio along with wavelength. Manufacturing uncertainties, particularly lithographic exposure, etching, and variations in waveguide thickness, tend to degrade the performance of the coupler. And because of small process tolerances, the coupling pitch cannot be too small, resulting in a larger overall coupler length.

The multimode interference coupler (MMI) can design different input/output port numbers according to actual demands to realize the port light splitting or light combining of N multiplied by M, and has the advantages of small volume, small loss, insensitivity to wavelength, large process tolerance and the like, and the disadvantage is that the bandwidth cannot be made to be very large. Because of these advantages, multimode interference couplers are increasingly being used in photonic integrated chips. A tapered waveguide is generally added between the strip waveguide of the input and output end and the multimode interference region, so that the mode spots are more matched, and the loss of the device is reduced.

An Arrayed Waveguide Grating (AWG) is composed of an input waveguide, two free transmission regions, an arrayed waveguide, and an output waveguide. The length difference of the array waveguide generates a phase difference, light with the same wavelength is interfered, and light with different wavelengths is focused to different output ports. According to the reversibility of the light path, the function of wavelength division multiplexing is realized. The loss and crosstalk of the array waveguide grating are small, the array waveguide grating can be made into a broadband or a narrowband, the array waveguide grating has multiple channels and large process tolerance, but the array waveguide grating has the defects of more parameters to be considered, complex design, larger size of devices and sensitivity to temperature.

Disclosure of Invention

The invention provides a broadband on-chip beam combining device which has the advantages of high power, small loss, large bandwidth, compact structure and small area, and overcomes the defects in the prior art.

In order to solve the technical problems, the invention adopts the following technical scheme: a broadband on-chip beam combining device comprises a plurality of active broadband beam combining devices based on Mach-Zehnder interferometers and an ultra-wide band beam combining device as an output end, wherein the active broadband beam combining devices are used as input ends; the active broadband beam combiner is characterized in that the input end of the active broadband beam combiner is provided with two input ports, the output end of the active broadband beam combiner is provided with an output port, a plurality of active broadband beam combining devices are connected in a binary tree structure, and the two active broadband beam combining devices at the tail stage are connected with the ultra-wide bandwidth beam combining devices through first bending waveguides, so that beam combining of light is realized.

In one embodiment, the active broadband beam combining device comprises a first multimode interference coupler, a second bending waveguide, a first heating arm, a second heating arm, a third bending waveguide and a second multimode interference coupler; the first multimode interference coupler is provided with two input ports and two output ports, and the second multimode interference coupler is provided with two input ports and one output port; the two output ports of the first multimode interference coupler are respectively connected with the input ends of the first heating arm and the second heating arm through the second bending waveguide, and the output ends of the first heating arm and the second heating arm are respectively connected with the two input ports of the second multimode interference coupler through the third bending waveguide.

In one embodiment, the output port of the second multimode interference coupler of the active broadband combining device of the upper stage is connected with one of the input ports of the first multimode interference coupler of the active broadband combining device of the lower stage; the adjacent two stages of active broadband beam combining devices are connected through a fourth bending waveguide.

In one embodiment, the plurality of input ports of the active broadband beam combining device are partially a short wavelength optical path and partially a long wavelength optical path; the wavelength spacing within each band is defined in terms of the bandwidths of the first multimode interference coupler and the second multimode interference coupler.

In one embodiment, in the same time domain, laser with one wavelength in the band sequentially passes through two first multimode interference couplers and one second multimode interference coupler and finally is input to an ultra-wide band beam combining device through a first bending waveguide; the laser is input from one input port of the active broadband beam combining device, is separated into two lights with equal power after passing through the first multimode interference coupler, then is modulated in phase by the first heating arm and the second heating arm, synthesizes a beam of light with small loss on the second multimode interference coupler, and finally is input to the ultra-wide bandwidth beam combining device through the first bending waveguide.

In one embodiment, the input light passes through the output port with a large optical path length and a small advanced optical path length after passing through the first multimode interference coupler

By heating the first heating arm or the second heating arm, the phase difference of the light of the two input ports before the light is input to the second multimode interference coupler is an integer multiple of 0 or 2 pi; the first heating arm and the second heating arm are used for modulating the light which passes through the first multimode interference coupler and is equal in power but incoherent to be equal in phase or different in integer multiple of 2 pi, so that the light power of the combined beam passing through the second multimode interference coupler is maximized.

The light modulation mode through the first heating arm and the second heating arm comprises thermo-optical modulation, electro-optical modulation and carrier modulation. The modulation method may be other methods, and is not limited to the above three methods.

In one embodiment, the active broadband combining device is a push-pull output, when two lights with different wavelengths enter the active broadband combining device, the phase difference of two lights generated after splitting of one light with the wavelength is 0 or an integral multiple of 2 pi, and the phase difference of two lights generated after splitting of the other light with the wavelength is an odd multiple of pi. This phase situation is the best beam splitting situation. The optical power of different beam splitting and combining can be adjusted according to actual conditions.

In one embodiment, the ultra-wideband combining device includes a fifth curved waveguide and a tapered coupler; the fifth bending waveguide is used for controlling the distance between the conical couplers so as to control the coupling length; the tapered coupler comprises a cross waveguide and a through waveguide, and light of the cross waveguide is coupled to the through waveguide by changing the bandwidth of the tapered waveguide, so that light combination is realized.

In one embodiment, for a crossed waveguide, long wavelength light is coupled into a straight-through waveguide by gradually decreasing the width of the tapered waveguide to decrease the effective refractive index; for the through waveguide, by gradually increasing the width of the tapered waveguide to increase the effective refractive index, short wavelength light is not coupled to other waveguides, and can be left entirely in the through waveguide.

In one embodiment, the coupling efficiency can be varied by adjusting the pitch of the tapered couplers and the tapered waveguides of the tapered couplers. At the same coupling length, wavelengths at which the transmission efficiency of the cross waveguide and the through waveguide are equal are defined as cross wavelengths. As the coupler length changes, the crossover wavelength also shifts. Thus, the pitch of the couplers and the slope of the tapered waveguide can be fine-tuned to change the coupling efficiency.

In the invention, the broadband on-chip beam combining device mainly comprises two parts: an active in-band beam combining device and an ultra-wide band beam combining device which are formed by Mach-Zehnder interferometers. The device is composed of a plurality of input ports, a part of which is long wavelength and a part of which is short wavelength. The input optical wavelength may be any wavelength within the bandwidth of the multimode interference coupler. By powering on the heating arm of the active in-band beam combining device, push-pull output can be achieved. The ultra-wide bandwidth beam combining device has high power, small loss and large bandwidth, and can realize on-chip beam combining with wavelength intervals of thousands of nanometers.

Compared with the prior art, the beneficial effects are that: the broadband on-chip beam combining device provided by the invention has the advantages of high power, small loss and large bandwidth, can realize beam combining with wavelength intervals of thousands of nanometers, and has the advantages of push-pull output, compact structure and small area.

Drawings

Fig. 1 is a schematic view of the overall structure of the present invention.

Fig. 2 is a schematic structural diagram of an active broadband beam combining device of the present invention.

Fig. 3 is a schematic structural diagram of the ultra wide band beam combining device of the present invention.

Fig. 4 is a schematic diagram of a process for fabricating an ultrawide bandwidth beam combining device of the present invention.

Reference numerals: 1. an active broadband beam combining device; 2. an ultra wide band beam combining device; 3. a first bending wave; 4. a fourth bending wave; 5. a first multimode interference coupler; 6. a second curved waveguide; 7. a first heating arm; 8. a second heating arm; 9. a third curved waveguide; 10. a second multimode interference coupler; 11. a fifth curved waveguide; 12. a tapered coupler; 13. a cross waveguide; 14. a straight-through waveguide; 15. a first port; 16. a second port; 17. a third port; 18. and a fourth port.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. The invention is described in one of its examples in connection with the following detailed description. Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to be limiting of the present patent; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

In the description of the present invention, it should be understood that, if there is an azimuth or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc., based on the azimuth or positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but it is not indicated or implied that the apparatus or element referred to must have a specific azimuth, be constructed and operated in a specific azimuth, and thus terms describing the positional relationship in the drawings are merely illustrative and should not be construed as limitations of the present patent, and specific meanings of the terms described above may be understood by those skilled in the art according to specific circumstances. In addition, if there is a description of "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" as it appears throughout is meant to include three side-by-side schemes, for example, "A and/or B", including the A scheme, or the B scheme, or the scheme where A and B meet at the same time.

Example 1:

as shown in fig. 1, a broadband on-chip beam combining device comprises a plurality of active broadband beam combining devices 1 based on mach-zehnder interferometers as input ends and an ultra-wide bandwidth beam combining device 2 as output ends; the input end of the active broadband beam combiner is provided with two input ports, the output end of the active broadband beam combiner is provided with an output port, the active broadband beam combiners 1 are connected in a binary tree structure, and the two active broadband beam combiners 1 at the tail stage are connected with the ultra-wide band beam combiners 2 through a first bending wave 3 guide, so that the beam combination of light is realized.

The active broadband beam combining device 1 comprises a first multimode interference coupler 5, a second bending waveguide 6, a first heating arm 7, a second heating arm 8, a third bending waveguide 9 and a second multimode interference coupler 10; the first multimode interference coupler 5 has two input ports and two output ports, and the second multimode interference coupler 10 has two input ports and one output port; the two output ports of the first multimode interference coupler 5 are respectively connected with the input ends of the first heating arm 7 and the second heating arm 8 through the second bending waveguide 6, and the output ends of the first heating arm 7 and the second heating arm 8 are respectively connected with the two input ports of the second multimode interference coupler 10 through the third bending waveguide 9.

Specifically, the output port of the second multimode interference coupler 10 of the active broadband beam combining device 1 of the upper stage is connected with one of the input ports of the first multimode interference coupler 5 of the active broadband beam combining device 1 of the lower stage; the adjacent two stages of active broadband beam combining devices 1 are connected through a fourth bending wave 4. The active broadband beam combining device 1 comprises a plurality of input ports, one part of which is a short-wavelength light path and the other part of which is a long-wavelength light path; the wavelength spacing within each band is defined in terms of the bandwidths of the first multimode interference coupler 5 and the second multimode interference coupler 10.

In addition, in the same time domain, laser with one wavelength in the band sequentially passes through two first multimode interference couplers 5 and one second multimode interference coupler 10, and finally is input to the ultra-wide band beam combining device 2 through the first bending wave 3; the laser is input from one input port of the active broadband beam combining device 1, is split into two lights with equal power after passing through the first multimode interference coupler 5, modulates the phase through the first heating arm 7 and the second heating arm 8, synthesizes a beam of light with small loss on the second multimode interference coupler 10, and finally is input to the ultra-wide bandwidth beam combining device 2 through the first bending wave 3.

The input light passes through the output port pi/2 with a large optical path and a small advanced optical path after passing through the first multimode interference coupler 5; by heating the first heating arm 7 or the second heating arm 8, the phase difference between the light of the two input ports before being input to the second multimode interference coupler 10 is an integer multiple of 0 or 2 pi; the first heating arm 7 and the second heating arm 8 are used for modulating the light which passes through the first multimode interference coupler 5 and is equal in power but incoherent to be equal in phase or different in integer multiple of 2 pi, so that the light power of the combined beam passing through the second multimode interference coupler 10 is maximized.

The active broadband beam combining device 1 is a push-pull output, when two lights with different wavelengths enter the active broadband beam combining device 1, the phase difference of two lights generated after splitting of one light with the wavelength is 0 or an integral multiple of 2 pi, and the phase difference of two lights generated after splitting of the other light with the wavelength is an odd multiple of pi. This phase situation is the best beam splitting situation. The optical power of different beam splitting and combining can be adjusted according to actual conditions.

In this embodiment, the active in-band broadband beam combining device based on MZI is a device with 2 input port and 1 output port composed of one 2×2MMI and 1×2MMI as shown in fig. 2. The multimode interference coupler MMI is the main device of the active in-band beam combining device, and the principle is based on the self-mapping effect proposed by Tabolt. A single-mode light excites multimode light in the multimode interference region, and the phenomenon of periodically appearing one or more images of the output light field in the light field transmission direction is referred to as the self-mapping effect. To increase the number of ports and reduce the pitch of the input wavelengths, taking fig. 1 as an example, 8-input port and 4-output port are used as the first-stage combined beam, and the wavelength pitch is within the bandwidth of the MMI. The second-stage beam combination adopts the same structure as the first-stage beam combination, and the port number is 4 input ports and 2 output ports. The output port is connected with the ultra wide band beam combining device 2.

According to a theoretical derivation, for 1 MMI, if one beam of light is input from the first port 15, this beam of light will be output from the third port 17 and the fourth port 18 after being split into two beams of light with different phases, and the fourth port 18 is pi/2 more phased than the third port 17, no matter how long the multimode interference zone is. In the 1×2MMI, the input port has symmetry at the center of the multimode interference region width, so that there is no phase difference between the two beams. Therefore, in order to cause the two light beams to interfere coherently at the output port, it is necessary to heat the first heating arm 7 to introduce a phase difference of pi/2.

The transfer constant of the first heating arm 7 is

The transfer constant of the second heating arm 8 is

Where n is the refractive index of the waveguide,

delta T is the temperature of the change, and lambda is the wavelength of the input light.

Thus the phase is changed to

The simultaneous equations (1), (2) and (3) allow the design of the heating arm length d and the heating temperature Δt.

The inter-band ultra-wideband beam combiner can realize ultra-wideband and high-power output, and as shown in fig. 3, the ultra-wideband beam combiner 2 comprises a fifth curved waveguide 11 and a tapered coupler 12; the fifth bending waveguide 11 is used for controlling the interval of the tapered coupler 12 and further controlling the coupling length; the tapered coupler 12 includes a cross waveguide 13 and a through waveguide 14, and the bandwidth of the tapered waveguide is changed to enable the light of the cross waveguide 13 to be coupled to the through waveguide 14, so as to realize the beam combination of the light. For the crossing waveguide 13, light of long wavelength is coupled to the through waveguide 14 by decreasing the effective refractive index by gradually decreasing the width of the tapered waveguide; for the through waveguide 14, the effective refractive index is increased by gradually increasing the width of the tapered waveguide so that short wavelength light is not coupled to other waveguides.

For example, the limit values of the wavelengths are selected to be 850nm and 3600nm, the width of the cross waveguide 13 is 2 μm, the width of the through waveguide 14 is 1 μm, the center wavelength of the input light is 1650nm and 2 μm, respectively, and the required design parameters are the coupling length. The relation between the wavelength and the transmission efficiency under different coupling lengths can be obtained through EME (eigenmode expansion) solver simulation. The wavelength at which the transmission efficiency of the crossing waveguide 13 and the through waveguide 14 is equal at the same coupling length is defined as the crossing wavelength. As the coupler length decreases, the crossover wavelength red shifts. Furthermore, the slope of the curve can be changed by fine tuning the pitch of the tapered coupler 12 and the width of the tapered waveguide. The coupling length and transmission efficiency under different wavelength conditions can also be obtained by scanning the coupling length through the EME solver. Since the coupling lengths of the through waveguide 14 and the crossing waveguide 13 are the same, it is necessary to obtain a point efficiency at which curves of the 850nm band and the 2 μm band cross as high as possible. The pitch of the tapered couplers 12 can also be fine-tuned and the width of the tapered waveguide changes the slope of the curve.

Example 2

Other structures of this embodiment are the same as those of embodiment 1, except that in this embodiment, 16 input ports and 8 output ports are used as the first-stage combined beams, and the wavelength interval is within the bandwidth of MMI. The second-stage beam combination adopts the same structure as the first-stage beam combination, the port number is 8 input ports and 4 output ports, and the wavelength interval is within the bandwidth of the MMI. The third-stage beam combination also adopts the same structure as the first-stage beam combination, the port number is 4 input ports and 2 output ports, and the 2 output ports are connected with the ultra-wide bandwidth beam combination device 2.

Example 3

The embodiment provides a method for preparing a broadband on-chip beam combining device, as shown in fig. 4, comprising the following steps:

1. and (3) homogenizing: dropping ARP 6200.13 on the sample and placing the sample on a spin coater, wherein the rotating speed is 3500r/min;

2. and (3) glue fixing: heating at 180deg.C for 10min;

3. exposure: EBL (electron beam exposure) defines a device pattern;

4. developing: soaking in xylene for 2min;

5. fixing: soaking in IPA (isopropyl alcohol) for 30s;

6. post-baking: baking by a hot plate at 142 ℃ to reduce the roughness of the side wall of the waveguide;

7. etching: RIE (reactive ion etching) etches the waveguide device structure;

8. growing a cladding: PECVD (plasma enhanced chemical vapor deposition) grows a cladding layer with a certain thickness;

9. flattening: chemical mechanical polishing;

10. and (3) homogenizing: dropping PMMA A7 on a sample, and placing the sample on a spin coater at a rotating speed of 3000r/min;

11. and (3) glue fixing: baking at 170deg.C for 3.5min;

12. exposure: the EBL defines a heater shape;

13. developing: MIBK (methyl isobutyl ketone) for 2min;

14. fixing: soaking in IPA (isopropyl alcohol) for 1min;

15. vapor deposition: evaporating NiCr alloy by using electron beam evaporation equipment at 200nm;

16. stripping: immersing the sample in acetone to strip the metal, and then cleaning with IPA and purified water;

17. and (3) homogenizing: dropping PMMA A7 on a sample, and placing the sample on a spin coater at a rotating speed of 3000r/min;

18. and (3) glue fixing: baking at 170deg.C for 3.5min;

19. exposure: the EBL defines the gold electrode shape;

20. developing: MIBK soaking for 2min;

21. fixing: IPA soaking for 1min;

22. vapor deposition: evaporating Ti with the thickness of 10nm and Au with the thickness of 300nm by using an electron beam evaporation device;

23. stripping: immersing the sample in acetone to strip the metal, and then cleaning with IPA and purified water;

24. splitting: cutting with diamond according to a certain crystal orientation, slicing an optical fiber with a waveguide section for testing, and performing edge coupling;

25. and (3) wire bonding: and connecting the electrode with the PCB interface by using an ultrasonic ball golden wire welding machine.

It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.

Claims

1. The broadband on-chip beam combining device is characterized by comprising a plurality of active broadband beam combining devices (1) which are used as input ends and are based on tunable Mach-Zehnder interferometers and an ultra-wide bandwidth beam combining device (2) which is used as an output end; the input end of the active broadband beam combiner is provided with two input ports, the output end of the active broadband beam combiner is provided with an output port, the active broadband beam combiners (1) are connected in a binary tree structure, and the two active broadband beam combiners (1) at the tail stage are connected with the ultra-wide band beam combiners (2) through the guide of a first bending wave (3), so that the beam combination of light is realized.

2. The broadband on-chip beam combining device according to claim 1, wherein the active broadband beam combining device (1) comprises a first multimode interference coupler (5), a second curved waveguide (6), a first heating arm (7), a second heating arm (8), a third curved waveguide (9), and a second multimode interference coupler (10); the first multimode interference coupler (5) is provided with two input ports and two output ports, and the second multimode interference coupler (10) is provided with two input ports and one output port; the two output ports of the first multimode interference coupler (5) are respectively connected with the input ends of the first heating arm (7) and the second heating arm (8) through the second bending waveguide (6), and the output ends of the first heating arm (7) and the second heating arm (8) are respectively connected with the two input ports of the second multimode interference coupler (10) through the third bending waveguide (9).

3. The broadband on-chip beam combining device according to claim 2, wherein an output port of the second multimode interference coupler (10) of the active broadband beam combining device (1) of the upper stage is connected with one of input ports of the first multimode interference coupler (5) of the active broadband beam combining device (1) of the lower stage; the adjacent two stages of active broadband beam combining devices (1) are connected through a fourth bending wave (4) in a guiding way.

4. The broadband on-chip beam combining device according to claim 2, wherein the plurality of input ports of the active broadband beam combining device (1) are partially a short wavelength optical path and partially a long wavelength optical path; the wavelength spacing within each band is defined in terms of the bandwidths of the first multimode interference coupler (5) and the second multimode interference coupler (10).

5. The broadband on-chip beam combining device according to claim 4, wherein in the same time domain, laser light of one wavelength in the band is sequentially transmitted through two first multimode interference couplers (5) and one second multimode interference coupler (10) and finally is guided to be input to the ultra-broadband beam combining device (2) through the first bending wave (3); the laser is input from one input port of the active broadband beam combining device (1), is split into two lights with equal power after passing through the first multimode interference coupler (5), modulates the phase through the first heating arm (7) and the second heating arm (8), synthesizes a beam of light with small loss on the second multimode interference coupler (10), and finally is guided and input to the ultra-wide bandwidth beam combining device (2) through the first bending wave (3).

6. The broadband on-chip beam combining device according to claim 5, wherein the output port having a large optical path length leads the output port having a small optical path length pi/2 after the input light passes through the first multimode interference coupler (5); by heating the first heating arm (7) or the second heating arm (8), the phase difference of the light of the two input ports before being input to the second multimode interference coupler (10) is an integer multiple of 0 or 2 pi; the first heating arm (7) and the second heating arm (8) are used for modulating the light which passes through the first multimode interference coupler (5) and is equal in power but incoherent to the equal phase or the integral multiple of the phase difference of 2 pi, so that the light power of the combined beam passing through the second multimode interference coupler (10) is maximized.

7. The broadband on-chip beam combining device of any of claims 1 to 6, wherein the means for modulating light by the first heating arm and the second heating arm comprises thermo-optic modulation, electro-optic modulation, carrier modulation.

8. The broadband on-chip beam combining device according to claim 5 or 6, wherein the active broadband beam combining device (1) is a push-pull output, and when two different wavelengths of light enter the active broadband beam combining device (1), a phase difference between two beams of light generated after splitting of one wavelength of light is an integer multiple of 0 or 2 pi, and a phase difference between two beams of light generated after splitting of the other wavelength of light is an odd multiple of pi.

9. The broadband on-chip beam combining device according to any of the claims 1 to 4, wherein the ultra-wideband beam combining device (2) comprises a fifth curved waveguide (11) and a tapered coupler (12); the fifth bending waveguide (11) is used for controlling the distance between the conical couplers (12) and further controlling the coupling length; the tapered coupler (12) comprises a cross waveguide (13) and a through waveguide (14), and the light of the cross waveguide (13) is coupled to the through waveguide (14) by changing the bandwidth of the tapered waveguide, so that the light beam combination is realized.

10. Broadband on-chip beam combining device according to claim 9, characterized in that for the crossing waveguide (13), light of long wavelength is coupled to the through waveguide (14) by decreasing the effective refractive index by gradually decreasing the width of the tapered waveguide; for the through waveguide (14), the effective refractive index is increased by gradually increasing the width of the tapered waveguide so that short wavelength light is not coupled to other waveguides and remains entirely in the through waveguide (14); the coupling efficiency can be changed by adjusting the pitch of the tapered coupler (12) and the tapered waveguide of the tapered coupler (12).