A broadband on-chip beam combining device

Abstract

The present invention belongs to the field of photonic integrated chips, and more specifically, relates to a broadband on-chip beam combining device, an active in-band beam combining device and an ultra-wideband beam combining device composed of Mach-Zehnder interferometers. The device consists of multiple input ports, with a part for long wavelengths and a part for short wavelengths. The input optical wavelength can be any wavelength within the bandwidth range of the multimode interference coupler. By energizing the heating arm of the active in-band beam combining device, push-pull output can be achieved. The ultra-wideband beam combining device has high power, low loss and large bandwidth, and can achieve on-chip beam combining with a wavelength interval of several thousand nanometers. The broadband on-chip beam combining device provided by the present invention has high power, low loss and large bandwidth, can achieve beam combining with a wavelength interval of several thousand nanometers, has push-pull output, and is compact in structure and small in area.

Description

Technical Field

[0001] The present invention belongs to the field of photonic integrated chips, and more specifically, relates to a broadband on-chip beam combining device. Background Art

[0002] With the increasing maturity of semiconductor processing technology, people gradually bond chips of different wavelengths to the same substrate. Therefore, the device for laser beam combining has become a key component for realizing multi-wavelength, broadband, and high-power lasers. Laser beam combining plays a crucial role in improving the power, efficiency, and beam quality of various laser systems, and is applied in fields such as long-distance free-space optical communication and material processing. There are two methods for realizing laser beam combining, namely coherent beam combining and wavelength beam combining. Coherent beam combining uses the phase difference generated by two beams of light to form coherent interference for beam combining, which is applicable to a relatively small wavelength range. Wavelength beam combining usually combines lasers of different wavelengths through a waveguide array grating or a filter. Its advantage is that it does not require an exact phase relationship and can perform broadband beam combining.

[0003] There are mainly three types of devices for realizing wavelength beam combining, namely a directional coupler (DC), a multimode interference coupler (MMI), and a waveguide array grating (AWG).

[0004] The directional coupler (DC) consists of two parallel waveguides. Due to the phase difference of π between two different modes, the field strength oscillates between the two waveguides. The directional coupler is the most common way to realize beam splitting and beam combining in optical fiber systems, with small additional loss and simple structure. However, its disadvantages are small bandwidth and process tolerance, and the splitting ratio is highly sensitive to wavelength. Manufacturing uncertainties, especially changes in photolithography exposure, etching, and waveguide thickness, easily degrade the performance of the coupler. Moreover, due to the small process tolerance, the coupling distance cannot be too small, resulting in a relatively large length of the entire coupler.

[0005] The multimode interference coupler (MMI) can design different numbers of input and output ports according to actual needs to achieve N×M port beam splitting or beam combining. It has the advantages of small volume, small loss, insensitivity to wavelength, and large process tolerance. The disadvantage is that it cannot achieve a very large bandwidth. Because of these advantages, the multimode interference coupler is increasingly widely used in photonic integrated chips. Usually, a tapered waveguide is added between the strip waveguides at the input and output ends and the multimode interference region to make the mode spot more matched and reduce the loss of the device.

[0006] An arrayed waveguide grating (AWG) consists of input waveguides, two free propagation regions, an array of waveguides, and output waveguides. A phase difference is generated by the length difference of the arrayed waveguides, and light of the same wavelength interferes, while light of different wavelengths is focused on different output ports. According to the reversibility of the optical path, the function of wavelength division multiplexing is achieved. The arrayed waveguide grating has low loss and crosstalk, can be made into both broadband and narrowband, has multiple channels and a large process tolerance. However, the disadvantages are that there are many parameters to consider, the design is complex, the device size is large, and it is relatively sensitive to temperature. Summary of the Invention

[0007] To overcome the above-mentioned defects in the prior art, the present invention provides a broadband on-chip beam combining device with high power, low loss, large bandwidth, compact structure, and small area.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is: a broadband on-chip beam combining device, including a plurality of active broadband beam combining devices based on Mach-Zehnder interferometers as input ends and an ultra-wideband beam combining device as an output end; the input end of the active broadband combiner has two input ports, the output end has one output port, and a plurality of active broadband beam combining devices are connected in a binary tree structure. The two active broadband beam combining devices at the last stage are connected to the ultra-wideband beam combining device through the first curved waveguide, thereby realizing the beam combination of light.

[0009] In one embodiment, the active broadband beam combining device includes a first multimode interference coupler, a second curved waveguide, a first heating arm, a second heating arm, a third curved waveguide, and a second multimode interference coupler; the first multimode interference coupler has two input ports and two output ports, and the second multimode interference coupler has two input ports and one output port; the two output ports of the first multimode interference coupler are respectively connected to the input ends of the first heating arm and the second heating arm through the second curved waveguide, and the output ends of the first heating arm and the second heating arm are respectively connected to the two input ports of the second multimode interference coupler through the third curved waveguide.

[0010] In one embodiment, the output port of the second multimode interference coupler of the upper-level active broadband beam combining device is connected to one of the input ports of the first multimode interference coupler of the lower-level active broadband beam combining device; the adjacent two-level active broadband beam combining devices are connected through a fourth curved waveguide.

[0011] In one embodiment, among the multiple input ports of the active broadband beam combining device, a part is the optical path of short wavelengths and a part is the optical path of long wavelengths; the wavelength spacing within each band is defined according to the bandwidths of the first multimode interference coupler and the second multimode interference coupler.

[0012] In one embodiment, within the same time domain, the laser of one wavelength within the band will sequentially pass through two first multimode interference couplers and a second multimode interference coupler, and finally be input into the ultra-wideband beam combining device through the first curved waveguide; the laser is input from an input port of one of the multiple active broadband beam combining devices, separated into two lights with equal power after passing through the first multimode interference coupler, the phases are modulated through the first heating arm and the second heating arm, combined into a light with very low loss on the second multimode interference coupler, and finally input into the ultra-wideband beam combining device through the first curved waveguide.

[0013] In one embodiment, after the input light passes through the first multimode interference coupler, the output port with a larger optical path leads the output port with a smaller optical path. By heating the first heating arm or the second heating arm, the phase difference between the lights at the two input ports before entering the second multimode interference coupler is 0 or an integer multiple of 2π; wherein, the functions of the first heating arm and the second heating arm are to modulate the equally powered but incoherent lights passing through the first multimode interference coupler to equal phases or a difference of an integer multiple of 2π, so that the light power of the light combined on the second multimode interference coupler reaches the maximum.

[0014] Among them, the methods of modulating light through the first heating arm and the second heating arm include thermo-optic modulation, electro-optic modulation, and carrier modulation. The modulation method can also be other forms, not limited to the above three methods.

[0015] In one embodiment, the active broadband beam combining device has a push-pull output. When lights of two different wavelengths enter the active broadband beam combining device, the phase difference between the two lights generated after one wavelength of light is split is 0 or an integer multiple of 2π, and the phase difference between the two lights generated after the other wavelength of light is split is an odd multiple of π. This phase condition is the best beam splitting condition. The optical powers of different beam splitting and beam combining can be adjusted according to actual situations.

[0016] In one embodiment, the ultra-wideband beam combining device includes a fifth curved waveguide and a tapered coupler; the fifth curved waveguide is used to control the spacing of the tapered coupler and thus control the coupling length; the tapered coupler includes a cross waveguide and a through waveguide, and the light in the cross waveguide is coupled to the through waveguide by changing the bandwidth of the tapered waveguide, thereby realizing the beam combining of light.

[0017] In one embodiment, for the cross waveguide, by gradually reducing the width of the tapered waveguide to reduce the effective refractive index, the light of the long wavelength is coupled to the through waveguide; for the through waveguide, by gradually increasing the width of the tapered waveguide to increase the effective refractive index, the light of the short wavelength is not coupled to other waveguides and can all remain in the through waveguide.

[0018] In one embodiment, the coupling efficiency can be changed by adjusting the spacing of the tapered coupler and the tapered waveguide of the tapered coupler. At the same coupling length, the wavelength at which the transmission efficiencies of the cross waveguide and the through waveguide are equal is defined as the cross wavelength. As the length of the coupler changes, the cross wavelength also shifts. Therefore, the coupling efficiency can be finely adjusted by changing the spacing of the coupler and the slope of the tapered waveguide.

[0019] In the present invention, the broadband on-chip beam combining device mainly includes two parts: an active in-band beam combining device composed of a Mach-Zehnder interferometer and an ultra-wideband beam combining device. The device consists of multiple input ports, with some for long wavelengths and some for short wavelengths. The input optical wavelength can be any wavelength within the bandwidth range of the multimode interference coupler. By energizing the heating arm of the active in-band beam combining device, push-pull output can be achieved. The ultra-wideband beam combining device has high power, low loss, and a large bandwidth, and can achieve on-chip beam combining with a wavelength interval of several thousand nanometers.

[0020] Compared with the prior art, the beneficial effects are as follows: A broadband on-chip beam combining device provided by the present invention has high power, low loss, and a large bandwidth, can achieve beam combining with a wavelength interval of several thousand nanometers, has push-pull output, and has a compact structure and a small area. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0022] Figure 2 It is a schematic diagram of the structure of the active broadband beam combining device of the present invention.

[0023] Figure 3 It is a schematic diagram of the structure of the ultra-wideband beam combining device of the present invention.

[0024] Figure 4 It is a schematic diagram of the preparation process of the ultra-wideband beam combining device of the present invention.

[0025] Reference Numerals: 1, active broadband beam combining device; 2, ultra-wideband beam combining device; 3, first bending wave; 4, fourth bending wave; 5, first multimode interference coupler; 6, second bending waveguide; 7, first heating arm; 8, second heating arm; 9, third bending waveguide; 10, second multimode interference coupler; 11, fifth bending waveguide; 12, tapered coupler; 13, cross waveguide; 14, through waveguide; 15, first port; 16, second port; 17, third port; 18, fourth port. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The present invention will be described below in conjunction with specific embodiments. Among them, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams, rather than physical diagrams, and should not be construed as a limitation to this patent; in order to better illustrate the embodiments of the present invention, some components in the accompanying drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0027] In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and should not be construed as a limitation to this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances. In addition, if there is a description involving "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly indicating the quantity of the technical features indicated. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text is to include three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time.

[0028] Embodiment 1:

[0029] As Figure 1 shown, a broadband on-chip beam combining device includes a plurality of active broadband beam combining devices 1 based on Mach-Zehnder interferometers as input ends and an ultra-wideband beam combining device 2 as an output end; the input end of the active broadband beam combiner has two input ports, and the output end has one output port. A plurality of active broadband beam combining devices 1 are connected in a binary tree structure, and the two active broadband beam combining devices 1 at the last stage are connected to the ultra-wideband beam combining device 2 through the first bent waveguide 3, thereby realizing the beam combining of light.

[0030] Among them, the active broadband beam combiner device 1 includes a first multimode interference coupler 5, a second bent waveguide 6, a first heating arm 7, a second heating arm 8, a third bent 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 to the input ends of the first heating arm 7 and the second heating arm 8 through the second bent waveguide 6, and the output ends of the first heating arm 7 and the second heating arm 8 are respectively connected to the two input ports of the second multimode interference coupler 10 through the third bent waveguide 9.

[0031] Specifically, the output port of the second multimode interference coupler 10 of the upper-level active broadband beam combiner device 1 is connected to one of the input ports of the first multimode interference coupler 5 of the lower-level active broadband beam combiner device 1; adjacent two-level active broadband beam combiner devices 1 are connected through a fourth bent waveguide 4. A part of the multiple input ports of the active broadband beam combiner device 1 is the optical path of short wavelength, and a part is the optical path of long wavelength; the wavelength spacing within each band is defined according to the bandwidths of the first multimode interference coupler 5 and the second multimode interference coupler 10.

[0032] In addition, within the same time domain, the laser of one wavelength within the band will sequentially pass through two first multimode interference couplers 5 and one second multimode interference coupler 10, and finally be input into the ultra-wideband beam combiner device 2 through the first bent waveguide 3; the laser is input from one of the input ports of multiple active broadband beam combiner devices 1, is separated into two lights with equal power after passing through the first multimode interference coupler 5, and then the phase is modulated through the first heating arm 7 and the second heating arm 8, and is combined into a light with very small loss on the second multimode interference coupler 10, and finally is input into the ultra-wideband beam combiner device 2 through the first bent waveguide 3.

[0033] The output port with a larger optical path leads the output port with a smaller optical path by π / 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 between the lights input from the two input ports before being input into the second multimode interference coupler 10 is 0 or an integer multiple of 2π; among them, the functions of the first heating arm 7 and the second heating arm 8 are to modulate the equal-power but incoherent lights passing through the first multimode interference coupler 5 to equal phases or a difference of an integer multiple of 2π, so that the optical power of the lights combined on the second multimode interference coupler 10 reaches the maximum.

[0034] Among them, the active broadband beam combiner device 1 has a push-pull output. When two lights with different wavelengths enter the active broadband beam combiner device 1, the phase difference between the two beams of light generated after one of the wavelengths is split is an integer multiple of 0 or 2π, and the phase difference between the two beams of light generated after the other wavelength is split is an odd multiple of π. This phase situation is the best beam splitting situation. The optical powers of different beam splitting and beam combining can be adjusted according to the actual situation.

[0035] In this embodiment, the active in-band broadband beam combiner device based on MZI is as Figure 2 shown, which is a device with 2 input ports and 1 output port composed of a 2×2 MMI and a 1×2 MMI. The multimode interference coupler MMI is the main device of the active in-band beam combiner device, and its principle is based on the self-imaging effect proposed by Tabolt. When a single-mode light excites multimode light in the multimode interference region, the phenomenon that one or more images of the output light field appear periodically along the direction of the light field transmission is called the self-imaging effect. In order to increase the number of ports and reduce the wavelength spacing of the input, taking Figure 1 as an example, 8 input ports and 4 output ports are used for the first-stage beam combining, and the wavelength spacing is within the bandwidth of the MMI. The second-stage beam combining adopts the same structure as the first-stage beam combining, and the number of ports is 4 input ports and 2 output ports. The output port is connected to the ultra-wideband beam combiner device 2.

[0036] According to theoretical derivation, for one MMI, if a beam of light is input from the first port 15, then this beam of light will be split into two beams of light with different phases and output from the third port 17 and the fourth port 18, and no matter how long the multimode interference region is, the phase of the fourth port 18 is π / 2 larger than that of the third port 17. In the 1×2 MMI, since the input port is at the center position of the width of the multimode interference region and has symmetry, the two output beams of light have no phase difference. Therefore, in order to make the two beams of light coherently interfere at the output port, it is necessary to heat the first heating arm 7 to introduce a phase difference of π / 2.

[0037] The transmission constant of the first heating arm 7 is

[0038]

[0039] The transmission constant of the second heating arm 8 is

[0040]

[0041] Among them, n is the refractive index of the waveguide, is the thermo-optic coefficient of the material, ΔT is the changed temperature, and λ is the wavelength of the input light.

[0042] Therefore, the phase change is

[0043]

[0044] By simultaneously solving equations (1), (2), and (3), the arm length d for heating and the temperature ΔT for heating can be designed.

[0045] The inter-band ultra-wideband combiner can achieve ultra-widebandwidth and high-power output, as Figure 3 shown. The ultra-wideband combiner device 2 includes a fifth bent waveguide 11 and a tapered coupler 12; the fifth bent waveguide 11 is used to control the spacing of the tapered coupler 12 and thus control the coupling length; the tapered coupler 12 includes a cross waveguide 13 and a through waveguide 14. By changing the bandwidth of the tapered waveguide, the light in the cross waveguide 13 is coupled to the through waveguide 14, thereby achieving the beam combination of light. For the cross waveguide 13, by gradually reducing the width of the tapered waveguide, the effective refractive index is reduced, and the light with a long wavelength is coupled to the through waveguide 14; for the through waveguide 14, by gradually increasing the width of the tapered waveguide, the effective refractive index is increased, so that the light with a short wavelength is not coupled to other waveguides.

[0046] For example, 850 nm and 3600 nm are selected as the wavelength limit values, the width of the cross waveguide 13 is 2 μm, the width of the through waveguide 14 is 1 μm, the center wavelengths of the input light are 1650 nm and 2 μm respectively, and the parameter to be designed is the coupling length. Through the simulation of the EME (eigenmode expansion) solver, the relationship between the wavelength and the transmission efficiency at different coupling lengths can be obtained. At the same coupling length, the wavelength at which the transmission efficiencies of the cross waveguide 13 and the through waveguide 14 are equal is defined as the cross wavelength. As the length of the coupler decreases, the cross wavelength redshifts. In addition, by finely adjusting the spacing of the tapered coupler 12 and the width of the tapered waveguide, the slope of the curve can be changed. By scanning the coupling length with the EME solver, the coupling length and the transmission efficiency under different wavelength conditions can also be obtained. Since the coupling lengths of the through waveguide 14 and the cross waveguide 13 are the same, what needs to be obtained is the point where the curves of the 850 nm band and the 2 μm band cross with as high an efficiency as possible. Similarly, the slope of the curve can be changed by finely adjusting the spacing of the tapered coupler 12 and the width of the tapered waveguide.

[0047] Embodiment 2

[0048] The other structures of this embodiment are the same as those of Embodiment 1. The difference is that in this embodiment, 16 input ports and 8 output ports are used for the beam combination of the first stage, and the wavelength spacing is within the bandwidth of the MMI. The second-stage beam combination uses the same structure as the first-stage beam combination, with 8 input ports and 4 output ports, and the wavelength spacing is within the bandwidth of the MMI. The third-stage beam combination also uses the same structure as the first-stage beam combination, with 4 input ports and 2 output ports, and the 2 output ports are connected to the ultra-wideband combiner device 2.

[0049] Embodiment 3

[0050] This embodiment provides a preparation method for a broadband on-chip beam combining device, as Figure 4 shown, including the following steps:

[0051] 1. Spin coating: Drop 13 drops of ARP 6200.1 on the sample and place the sample on a spin coater at a rotation speed of 3500 r / min;

[0052] 2. Baking the film: Bake on a hot plate at 180 °C for 10 min;

[0053] 3. Exposure: Define the device pattern by EBL (electron beam lithography);

[0054] 4. Development: Immerse in xylene for 2 min;

[0055] 5. Fixing: Immerse in IPA (isopropyl alcohol) for 30 s;

[0056] 6. Post-baking: Bake on a hot plate at 142 °C to reduce the roughness of the waveguide sidewalls;

[0057] 7. Etching: Etch the waveguide device structure by RIE (reactive ion etching);

[0058] 8. Cladding growth: Grow a cladding of a certain thickness by PECVD (plasma enhanced chemical vapor deposition);

[0059] 9. Planarization: Chemical mechanical polishing;

[0060] 10. Spin coating: Drop PMMA A7 on the sample and place the sample on a spin coater at a rotation speed of 3000 r / min;

[0061] 11. Baking the film: Bake on a hot plate at 170 °C for 3.5 min;

[0062] 12. Exposure: Define the heater shape by EBL;

[0063] 13. Development: Immerse in MIBK (methyl isobutyl ketone) for 2 min;

[0064] 14. Fixing: Immerse in IPA (isopropyl alcohol) for 1 min;

[0065] 15. Evaporation: Evaporate 200 nm of NiCr alloy using an electron beam evaporation device;

[0066] 16. Lift-off: Immerse the sample in acetone to strip the metal, and then clean it with IPA and pure water;

[0067] 17. Spin coating: Drop PMMA A7 on the sample and place the sample on a spin coater at a rotation speed of 3000 r / min;

[0068] 18. Baking the film: Bake on a hot plate at 170 °C for 3.5 min;

[0069] 19. Exposure: EBL defines the shape of the gold electrode;

[0070] 20. Development: Immerse in MIBK for 2 min;

[0071] 21. Fixing: Immerse in IPA for 1 min;

[0072] 22. Evaporation: Evaporate 10 nm of Ti and 300 nm of Au using an electron beam evaporation device;

[0073] 23. Stripping: Immerse the sample in acetone to strip the metal, and then clean it with IPA and pure water;

[0074] 24. Cleaving: Cut with a diamond along a certain crystal orientation, and the sliced section has a waveguide cross-section for edge coupling with the optical fiber used for testing;

[0075] 25. Wire bonding: Connect the electrode to the PCB interface using an ultrasonic ball wire bonder.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A broadband on-chip beam combining device, characterized in that, it includes a plurality of active broadband beam combining devices (1) based on tunable Mach-Zehnder interferometers as input ends and an ultra-wideband beam combining device (2) as an output end; the input end of the active broadband beam combiner has two input ports, the output end has one output port, and a plurality of active broadband beam combining devices (1) are connected in a binary tree structure. The two active broadband beam combining devices (1) at the last stage are connected to the ultra-wideband beam combining device (2) through a first bent waveguide (3), so as to realize the beam combining of light; the active broadband beam combining device (1) includes a first multimode interference coupler (5), a second bent waveguide (6), a first heating arm (7), a second heating arm (8), a third bent 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 to the input ends of the first heating arm (7) and the second heating arm (8) through the second bent waveguide (6), and the output ends of the first heating arm (7) and the second heating arm (8) are respectively connected to the two input ports of the second multimode interference coupler (10) through the third bent waveguide (9); the output port of the second multimode interference coupler (10) of the upper-level active broadband beam combining device (1) is connected to one of the input ports of the first multimode interference coupler (5) of the lower-level active broadband beam combining device (1); adjacent two-level active broadband beam combining devices (1) are connected through a fourth bent waveguide (4).

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

3. The broadband on-chip beam combining device according to claim 2, characterized in that, within the same time domain, the laser of one wavelength within the band will sequentially pass through two first multimode interference couplers (5) and one second multimode interference coupler (10), and finally be input into the ultra-wideband beam combining device (2) through the first bent waveguide (3); the laser is input from one of the input ports of the multiple active broadband beam combining devices (1), is separated into two lights with equal power after passing through the first multimode interference coupler (5), then the phases are modulated by the first heating arm (7) and the second heating arm (8), and are combined into a beam of light with very low loss on the second multimode interference coupler (10), and finally are input into the ultra-wideband beam combining device (2) through the first bent waveguide (3).

4. The broadband on-chip beam combining device according to claim 3, characterized in that, After the input light passes through the first multimode interference coupler (5), the output port with a longer optical path leads the output port with a shorter optical path by π / 2; by heating the first heating arm (7) or the second heating arm (8), the phase difference between the lights input into the two input ports before entering the second multimode interference coupler (10) is 0 or an integer multiple of 2π; wherein, the first heating arm (7) and the second heating arm (8) are used to modulate the equal-power but incoherent lights passing through the first multimode interference coupler (5) to equal phases or a phase difference that is an integer multiple of 2π, so that the optical power of the lights combined by the second multimode interference coupler (10) reaches the maximum.

5. The broadband on-chip beam combining device according to any one of claims 1 to 4, characterized in that the ways of modulating light by the first heating arm and the second heating arm include thermo-optic modulation, electro-optic modulation, and carrier modulation.

6. The broadband on-chip beam combining device according to claim 3 or 4, characterized in that the active broadband beam combining device (1) has a push-pull output. When lights of two different wavelengths enter the active broadband beam combining device (1), the phase difference between the two beams of light generated after one wavelength of light is split is 0 or an integer multiple of 2π, and the phase difference between the two beams of light generated after the other wavelength of light is split is an odd multiple of π.

7. The broadband on-chip beam combining device according to any one of claims 1 to 4, characterized in that the ultra-wideband beam combining device (2) includes a fifth bent waveguide (11) and a tapered coupler (12); the fifth bent waveguide (11) is used to control the spacing of the tapered coupler (12) and thus control the coupling length; the tapered coupler (12) includes a cross waveguide (13) and a through waveguide (14), and by changing the bandwidth of the tapered waveguide, the light in the cross waveguide (13) is coupled to the through waveguide (14), thereby realizing the beam combining of light.

8. The broadband on-chip beam combining device according to claim 7, characterized in that for the cross waveguide (13), by gradually reducing the width of the tapered waveguide to reduce the effective refractive index, the long-wavelength light is coupled to the through waveguide (14); for the through waveguide (14), by gradually increasing the width of the tapered waveguide to increase the effective refractive index, the short-wavelength light is not coupled to other waveguides and all remains in the through waveguide (14); the coupling efficiency can be changed by adjusting the spacing of the tapered coupler (12) and the tapered waveguide of the tapered coupler (12).

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