A multi-wavelength narrow-linewidth laser

Abstract

The present invention relates to a multi-wavelength narrow linewidth laser, comprising: a reflective optical amplifier, the reflective optical amplifier being used to generate seed light; a comb filter, the input end of the comb filter being connected to the output end of the reflective optical amplifier; and a wavelength division multiplexer, the wavelength division multiplexer having one input end and at least two output ends, the input end of the wavelength division multiplexer being connected to the output end of the comb filter; the multi-wavelength narrow linewidth laser satisfies: Δf ch(WDM) =m×Δf (filter) ;δf (WDM) <Δf (filter) ; and f FSR(WDM) >Δf (gain) ; where Δf (filter) is the frequency spacing of the comb filter, Δf ch(WDM) is the frequency channel spacing of the wavelength division multiplexer, δf (WDM) is the 3dB bandwidth of a single channel of the wavelength division multiplexer, m is a positive integer not less than 2, Δf (gain) is the 3dB gain bandwidth of the reflective optical amplifier, f FSR(WDM) is the free spectral range of the wavelength division multiplexer.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, in particular to a multi-wavelength narrow-linewidth laser. Background Art

[0002] Wavelength division multiplexing (WDM) technology, with its unique parallel transmission capabilities and efficient bandwidth utilization, has shown broad application prospects in multiple fields, including optical communications, optical interconnection, optical computing, and optical sensing. With the continuous advancement of WDM technology and the expansion of its application areas, the demand for low-cost, high-performance multi-channel, multi-wavelength light sources is also growing.

[0003] Traditional multi-wavelength light sources require multiple independent high-performance single-wavelength lasers to form a laser array. Their preparation process is complex, and during the continuous frequency modulation process, each wavelength channel needs to be controlled separately. Therefore, this type of multi-wavelength light source not only has high power consumption and large size, but also high cost. The operating steps required to achieve continuous frequency modulation are also very cumbersome. Summary of the Invention

[0004] Based on this, it is necessary to provide a multi-wavelength narrow-linewidth laser to address the problems of high cost, large size, and complex continuous frequency modulation operation steps of existing multi-wavelength light sources.

[0005] The technical solution provided by the present invention is:

[0006] A multi-wavelength narrow-linewidth laser, comprising:

[0007] a reflective optical amplifier, wherein the reflective optical amplifier is used to generate seed light;

[0008] a comb filter, wherein an input end of the comb filter is connected to an output end of the reflective optical amplifier; and

[0009] A wavelength division multiplexer, the wavelength division multiplexer having an input end and at least two output ends, the input end of the wavelength division multiplexer being connected to the output end of the comb filter;

[0010] The multi-wavelength narrow linewidth laser satisfies:

[0011] Δf ch(WDM) = m × Δf (filter) ;

[0012] δf (WDM) <Δf (filter) ;and

[0013] f FSR(WDM) > Δf (gain) ;

[0014] Where Δf (filter)is the frequency spacing of the comb filter, Δf ch(WDM) is the main frequency channel spacing of the wavelength division multiplexer, δf (WDM) is the 3dB bandwidth of a single channel of the wavelength division multiplexer, m is a positive integer not less than 2, Δf (gain) is the 3dB gain bandwidth of the reflective optical amplifier, f FSR(WDM) is the free spectral range of the wavelength division multiplexer.

[0015] In some embodiments, the multi-wavelength narrow linewidth laser further includes a reflection unit array, the reflection unit array includes at least two reflectors, and each output end of the wavelength division multiplexer is connected to one of the reflectors;

[0016] The reflector is a transflective structure. A high-reflection film is provided on the side of the reflective optical amplifier away from the comb filter. The high-reflection film and the reflector are arranged to form a resonant cavity.

[0017] In some embodiments, the multi-wavelength narrow linewidth laser further includes a phase shifter connected between the output end of the reflective optical amplifier and the input end of the comb filter to adjust the phase in the resonant cavity.

[0018] In some embodiments, the comb filter, the wavelength division multiplexer, the reflector, and the phase shifter are integrated on a photonic integrated chip.

[0019] In some embodiments, the multi-wavelength narrow linewidth laser further includes at least two optical power amplifiers, each of which corresponds to the reflector on a one-to-one basis. The optical power amplifier is connected to the output end of the corresponding reflector to increase the laser output power of the corresponding reflector.

[0020] In some embodiments, the reflector is a Sagnac loop reflector or a Bragg reflector.

[0021] In some embodiments, the comb filter has a tuning electrode to allow the comb filter to simultaneously adjust the center frequency of each frequency channel thereof through an electrical signal.

[0022] In some embodiments, the center frequency of one frequency channel of the comb filter is f n , n is a positive integer;

[0023] The number of output terminals of the wavelength division multiplexer is N, and the center frequency of one of the main frequency channels of the wavelength division multiplexer is f chK , 1≤K≤N and K is an integer;

[0024] The multi-wavelength narrow linewidth laser satisfies:

[0025] f chK -δf (WDM) / 2≤f n ≤f chK +δf (WDM) / 2.

[0026] In some embodiments, the 3dB gain bandwidth endpoints of the reflective optical amplifier are F1 and F2, where F1 <F2;

[0027] The center frequencies of the two sub-frequency channels of the wavelength division multiplexer are f -1 chN and f +1 ch1 , where f chN -f -1 chN =f +1 ch1 -f ch1 =f FSR(WDM) , f FSR(WDM) ≥N×Δf ch(WDM) ;

[0028] The multi-wavelength narrow linewidth laser satisfies:

[0029] f -1 chN +δf (WDM) / 2<F1≤f n ;and

[0030] F2<f +1 ch1 -δf (WDM) / 2.

[0031] In some embodiments, the transmission spectrum of the wavelength division multiplexer is designed to be a flat-top response, and the loss difference between any two main frequency channels of the wavelength division multiplexer is less than 1 dB.

[0032] The beneficial effects of the present invention are:

[0033] 1. The multi-wavelength, narrow-linewidth laser of the present invention utilizes a cascaded comb filter and wavelength division multiplexer to select and filter laser modes, achieving multi-wavelength, narrow-linewidth laser output. Compared to laser arrays, the multi-wavelength, narrow-linewidth laser of the present invention offers advantages such as compact size, low cost, and ease of fabrication.

[0034] 2. For the cascade structure of comb filter and wavelength division multiplexer, the comb filter screens the seed light generated by the reflective optical amplifier for the first time and then outputs a large number of narrow spectrum signals of different frequencies. ch(WDM) = m × Δf (filter) and δf(WDM) <Δf (filter) Under these two conditions, in conjunction with the tuning of the comb filter, each frequency channel of the wavelength division multiplexer is then used to perform secondary screening on the output light of the comb filter, thereby enhancing the mode selectivity of the laser. The laser linewidth ultimately output by the laser can be further compressed, and multiple output channels are also provided for the multi-wavelength narrow-linewidth laser of the present invention.

[0035] 3. In the wavelength division multiplexer, since each output port corresponds to multiple frequency channels (the frequency interval between different frequency channels corresponding to the same output port is determined by the free spectrum range of the wavelength division multiplexer), the frequency of the output port is determined by the free spectrum range of the wavelength division multiplexer. FSR(WDM) >Δf (gain) Based on this relationship, one of the frequency channels corresponding to the output port will serve as the primary frequency channel, and the remaining frequency channels will serve as secondary frequency channels. Furthermore, based on the theory of mode competition in lasers, only the optical signal in the primary frequency channel can meet the threshold condition and then be output from the corresponding output port to generate laser light. The optical signal in the secondary frequency channel, because it does not meet the threshold condition, ultimately cannot form laser light for output. This ensures that each output port has stable single-wavelength, narrow-linewidth laser output.

[0036] 4. Based on Δf ch(WDM) = m × Δf (filter) ,δf (WDM) <Δf (filter) and f FSR(WDM) > Δf (gain) According to the three equations, synchronous continuous frequency modulation of multi-wavelength lasers output from each output end of the wavelength division multiplexer can be achieved simply by tuning the comb filter. Therefore, its continuous frequency modulation method is simple and can meet the application requirements of scenarios including FMCW lidar. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a topological diagram of the multi-wavelength narrow linewidth laser in Example 1 of the present invention;

[0038] Figure 2 Schematic diagram of parameters of a multi-wavelength narrow-linewidth laser in Example 1 of the present invention;

[0039] Figure 3 This is a topological diagram of a multi-wavelength narrow-linewidth laser in the second embodiment of the present invention;

[0040] Figure 4 Schematic diagram of the planar structure of the multi-wavelength narrow linewidth laser in the third embodiment of the present invention;

[0041] Figure 5 Schematic diagram of the planar structure of the multi-wavelength narrow linewidth laser in the fourth embodiment of the present invention;

[0042] Figure 6 Schematic diagram of the planar structure of the multi-wavelength narrow-linewidth laser in Example 5 of the present invention.

[0043] Reference numerals:

[0044] 1. Reflective optical amplifier; 11. High-reflection film; 2. Comb filter; 3. Wavelength division multiplexer; 4. Reflector; 5. Phase shifter; 6. Optical power amplifier. DETAILED DESCRIPTION

[0045] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are 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, and therefore should not be understood as limiting the present invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0048] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0049] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0050] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element present at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0051] Embodiment 1

[0052] Refer to Figure 1 , this embodiment provides a multi-wavelength narrow linewidth laser, including: a reflective optical amplifier 1, a comb filter 2, a wavelength division multiplexer 3, a phase shifter 5 and a reflector array. The output end of the reflective optical amplifier 1 and the input end of the comb filter 2 are connected through the phase shifter 5. The wavelength division multiplexer 3 has one input end and at least two output ends. The reflector array includes at least two reflectors 4. The output end of the comb filter 2 is connected to the input end of the wavelength division multiplexer 3, and each output end of the wavelength division multiplexer 3 is connected with a reflector 4. The reflector 4 is a transmissive and reflective structure. A high-reflection film is provided on one side of the reflective optical amplifier 1 away from the comb filter 2. The high-reflection film and the reflector 4 enclose a resonant cavity, and the output light of the wavelength division multiplexer 3 partially penetrates from the reflector 4. The reflective optical amplifier 1 can generate seed light in the resonant cavity. The phase shifter 5 has a tuning electrode to adjust the phase in the resonant cavity through an electrical signal. Further preferably, an antireflection film can also be provided on one side of the reflective optical amplifier 1 close to the comb filter 2.

[0053] The specific parameters of the multi-wavelength narrow linewidth laser in this embodiment are as Figure 2 shown.

[0054] The 3dB gain bandwidth of the reflective optical amplifier 1 is Δf (gain) , where the endpoint frequency values corresponding to the 3dB gain bandwidth are F1 and F2, where F1 < F2, that is, F2 - F1 = Δf (gain) .

[0055] The center frequencies of the frequency channels of the comb filter 2 are f1, f2, ..., f n , ..., where n is a positive integer. The frequency interval of the comb filter 2 is Δf (filter) In other words, f n+1 -f n =Δf (filter) In this embodiment, the comb filter 2 has tuning electrodes to allow the comb filter 2 to simultaneously adjust the center frequencies of its various frequency channels through electrical signals.

[0056] The number of output terminals of the wavelength division multiplexer 3 is N, and these N output terminals are ch1, ch2, ..., chN. The center frequencies of the frequency channels of the wavelength division multiplexer 3 are, from small to large, ..., f -2 chN , f -1 ch1 , f -1 ch2 ,...,f -1 chN , f ch1 , f ch2 ,...,f chN , f +1 ch1 , f +1 ch2 ,...,f +1 chN , f +2 ch1 ,.... Based on the filtering characteristics of the wavelength division multiplexer 3, each output port of the wavelength division multiplexer 3 corresponds to multiple frequency channels, and each output port can output the optical signal in the corresponding frequency channel when the threshold condition is met. Taking the output port ch1 as an example, the center frequency is..., f -1 ch1 , f ch1 , f +1 ch1 , f +2 ch1 ,...The frequency channel corresponds to the output terminal ch1, and the center frequency is..., f -1 ch1 , f ch1 , f +1 ch1 , f +2 ch1 ,... The optical signal in the frequency channel will be output through the output terminal ch1 when the threshold condition is met. Similarly, the center frequency is..., f -2 chN , f -1 chN , fchN , f +1 chN ,...The frequency channel corresponds to the output terminal chN, and the center frequency is..., f -2 chN , f -1 chN , f chN , f +1 chN , ..., the optical signal in the frequency channel will be output through the output terminal chN when the threshold condition is met. The corresponding relationships of other output terminals are similar and will not be described in detail in this embodiment.

[0057] The free spectral range of wavelength division multiplexer 3 is ,Right now = = = = =...= = In other words, the free spectral range refers to the center frequency spacing between two adjacent frequency channels corresponding to the same output port.

[0058] In addition, the wavelength division multiplexer 3 also satisfies the following relationship: =...= = =...= = =...= = The center frequency is f -1 ch1 , f -1 ch2 ,...,f -1 chN The frequency channel of can be regarded as a set of frequency channels with a center frequency of f ch1 , f ch2 ,...,f chN The frequency channels of can also be considered as a group of frequency channels. In other words, Δf ch(WDM) It is the center frequency distance between two adjacent frequency channels in the same group of frequency channels.

[0059] The center frequency is f -1 ch1 , f -1 ch2 ,...,f -1 chN The frequency channel of can be regarded as a set of frequency channels with a center frequency of f ch1 , f ch2 ,...,f chNThe frequency channels of can also be considered as a group of frequency channels. In other words, Δf ch(WDM) It is the center frequency distance between two adjacent frequency channels in the same group of frequency channels.

[0060] Generally, f FSR(WDM) ≥N×Δf ch(WDM) .

[0061] It is particularly noteworthy that the multi-wavelength narrow linewidth laser of this embodiment not only meets the basic characteristics of the aforementioned devices, but also meets the following additional requirements: Δf ch(WDM) = m × Δf (filter) ,δf (WDM) <Δf (filter) and f FSR(WDM) > Δf (gain) , where m is a positive integer not less than 2, δf (WDM) is the 3dB bandwidth of single channel of wavelength division multiplexer 3.

[0062] For f FSR(WDM) > Δf (gain) This relationship is specifically expressed in this embodiment as: -1 chN +δf (WDM) / 2<F1≤f ch1 -δf (WDM) / 2,f chN +δf (WDM) / 2≤F2<f +1 ch1 -δf (WDM) / 2.

[0063] On this basis, the comb filter 2 can be tuned according to actual needs to meet f chK -δf (WDM) / 2≤f n ≤f chK +δf (WDM) / 2, 1≤K≤N and K is an integer. The value of n can be changed according to actual needs. For example, in this embodiment, f ch1 -δf (WDM) / 2≤f n ≤f ch1 +δf (WDM) / 2. It is not difficult to understand that based on Δf ch(WDM) = m × Δf (filter) This relationship is satisfied when f ch1 -δf (WDM) / 2≤f n ≤f ch1 +δf (WDM) / 2, it will also satisfy ≤ ,..., ≤ ≤ .

[0064] For example, in some other embodiments, the comb filter 2 can be tuned according to the requirements to meet the f ch2 -δf (WDM) / 2≤f n ≤f ch2 +δf (WDM) / 2,f ch3 -δf (WDM) / 2≤f n+m ≤f ch3 +δf (WDM) / 2, .... Similar situations will not be described in detail in this embodiment.

[0065] The comb filter 2 filters the continuous frequency light generated by the reflective optical amplifier 1. Based on the above relationship, it can be seen that within the 3dB gain bandwidth of the reflective optical amplifier 1, the transmission spectrum of the comb filter 2 in this embodiment will at least include a center frequency of f n , f n+1 ,...,f n+（N-1）m The bandwidth of each frequency channel in the transmission spectrum of comb filter 2 is very narrow, which provides a basis for subsequent linewidth compression and continuous frequency tuning of multi-wavelength lasers.

[0066] Based on the above analysis, we can know that the frequency of the comb filter 2 output is f n The optical signal will enter the wavelength division multiplexer 3 with a center frequency of f ch1 The frequency channel of comb filter 2 is f n+m The optical signal will enter the wavelength division multiplexer 3 with a center frequency of f ch2 The frequency channel of comb filter 2 is f n+（N-1）m The optical signal will enter the wavelength division multiplexer 3 with a center frequency of f chN frequency channel.

[0067] Based on δf (WDM) <Δf (filter) This relationship is based on the center frequency of wavelength division multiplexer 3 being f ch1 As an example, the frequency channel of the comb filter 2 is only allowed to output a frequency of f n The optical signal passes through, and the frequency output by comb filter 2 is f n-1 and f n+1 The optical signal cannot enter the wavelength division multiplexer 3 with a center frequency of f ch1The other frequency channels of wavelength division multiplexer 3 have similar characteristics and will not be described in detail in this embodiment. In other words, each frequency channel of wavelength division multiplexer 3 only allows one frequency optical signal output by comb filter 2 to pass through, thereby achieving a secondary filtering effect after comb filter 2, increasing the mode selectivity of the laser.

[0068] Based on the above f FSR(WDM) > Δf (gain) From this relationship, we can see that the wavelength division multiplexer 3 has a center frequency of f ch1 , f ch2 ,...,f chN Except for the frequency channel with a center frequency of f +1 ch1 and f -1 chN Even if there is an optical signal output by the comb filter 2 in the frequency channel, the optical signal is definitely not within the 3dB gain bandwidth of the reflective optical amplifier 1. Therefore, the energy of the corresponding frequency is very small and cannot form laser output. Therefore, each output terminal ch1, ch2, ..., chN of the wavelength division multiplexer 3 can only output single-frequency laser, and the corresponding output frequency is f n , f n+m ,...,f n+（N-1）m , thus ensuring the stable working conditions of the multi-wavelength narrow-linewidth laser.

[0069] In other words, for the multi-wavelength narrow linewidth laser of this embodiment, the center frequency of the wavelength division multiplexer 3 is f ch1 , f ch2 ,...,f chN The frequency channel is used as the main frequency channel, Δf ch(WDM) That is, the center frequency interval between two adjacent main frequency channels.

[0070] In summary, the multi-wavelength narrow linewidth laser of this embodiment has at least the following advantages:

[0071] 1. Through the filtering effect of the comb filter 2, it provides a basis for the final laser to output narrow linewidth laser and realize continuous tuning of multi-channel laser frequency. In addition, the wavelength division multiplexer 3 is based on Δf ch(WDM) = m × Δf (filter) and δf (WDM) <Δf (filter) The two relations perform secondary filtering on the laser output by the comb filter 2, thereby increasing the mode selectivity of the laser.

[0072] 2.Wavelength Division Multiplexer 3 based on f FSR(WDM) > Δf (gain)Under this condition, the optical signals in the multiple frequency channels corresponding to each output end are filtered again, reducing the mutual interference between the different frequency channels of the wavelength division multiplexer 3, so that each output end finally outputs a single frequency laser.

[0073] 3. Only need to satisfy f chK -δf (WDM) / 2≤f n ≤f chK +δf (WDM) / 2, the comb filter 2 is continuously tuned to make f n , f n+m ,...,f n+（N-1）m The synchronization changes, and then the multi-wavelength laser output by the laser is synchronized and continuously frequency modulated, meeting the use requirements of FMCW laser radar.

[0074] Preferably, the wavelength division multiplexer 3 is designed to have a flat-top response. Based on this feature, during the continuous tuning of the comb filter 2, while the frequency of the optical signal in each frequency channel of the wavelength division multiplexer 3 changes, the laser power does not change or fluctuate significantly, thereby maintaining the optical power output of the laser stable.

[0075] Further preferably, the loss difference between any two main frequency channels of the wavelength division multiplexer 3 is less than 1 dB, thereby ensuring that the optical signal in each main frequency channel of the multi-wavelength narrow linewidth laser meets the threshold condition at the same time, and the optical power in each main frequency channel is roughly the same, thereby ensuring that the power difference between the different frequency lasers output by the final laser is small.

[0076] Example 2

[0077] See also Figure 3 This embodiment provides a multi-wavelength narrow-linewidth laser, comprising: a reflective optical amplifier 1, a comb filter 2, a wavelength division multiplexer 3, a phase shifter 5, and a reflective unit array. The output of the reflective optical amplifier 1 is connected to the input of the comb filter 2 via the phase shifter 5. The wavelength division multiplexer 3 has one input and at least two outputs. The reflective unit array includes at least two reflectors 4. The output of the comb filter 2 is connected to the input of the wavelength division multiplexer 3, and each output of the wavelength division multiplexer 3 is connected to a reflector 4. The reflectors 4 are transflective structures. A high-reflective film is provided on the side of the reflective optical amplifier 1 away from the comb filter 2. The high-reflective film and the reflectors 4 form a resonant cavity, and the output light of the wavelength division multiplexer 3 partially transmits through the reflectors 4. The reflective optical amplifier 1 can generate seed light within the resonant cavity. The phase shifter 5 has a tuning electrode to adjust the phase within the resonant cavity using an electrical signal. Further preferably, an anti-reflection film can also be provided on the side of the reflective optical amplifier 1 near the comb filter 2.

[0078] Compared with the first embodiment, the reflective optical amplifier 1, the comb filter 2, the wavelength division multiplexer 3, the phase shifter 5 and the reflective unit array in this embodiment have the same performance and structural parameters. Therefore, the working principle of this embodiment is the same as that of the first embodiment and will not be repeated here.

[0079] The main difference between this embodiment and the first embodiment is that the laser further includes at least two optical power amplifiers 6. The number of optical power amplifiers 6 matches the number of reflectors 4, so that there is a one-to-one correspondence between each optical power amplifier 6 and each reflector 4. The optical power amplifiers 6 are connected to the output end of the corresponding reflector 4 to amplify the optical power of the specific frequency laser light output from the reflector 4.

[0080] Example 3

[0081] See also Figure 4 This embodiment provides a multi-wavelength, narrow-linewidth laser, comprising: a reflective optical amplifier 1, a comb filter 2, a wavelength division multiplexer 3, a phase shifter 5, and a reflective unit array. The output of the reflective optical amplifier 1 is connected to the input of the comb filter 2 via the phase shifter 5. The wavelength division multiplexer 3 has one input and at least two outputs. The reflective unit array includes at least two reflectors 4. The output of the comb filter 2 is connected to the input of the wavelength division multiplexer 3, and each output of the wavelength division multiplexer 3 is connected to a reflector 4. The reflectors 4 are transflective structures. A high-reflective film 11 with a reflectivity greater than 90% is provided on the side of the reflective optical amplifier 1 facing away from the comb filter 2. The high-reflective film 11 and the reflectors 4 form a resonant cavity, and the output light of the wavelength division multiplexer 3 partially transmits through the reflectors 4. The reflective optical amplifier 1 can generate seed light within the resonant cavity. The phase shifter 5 has a tuning electrode to adjust the phase within the resonant cavity using an electrical signal.

[0082] Compared with the first embodiment, the reflective optical amplifier 1, the comb filter 2, the wavelength division multiplexer 3, the phase shifter 5 and the reflective unit array in this embodiment have the same performance and structural parameters. Therefore, the working principle of this embodiment is the same as that of the first embodiment and will not be repeated here.

[0083] In this embodiment, the reflective optical amplifier 1 is fabricated based on a III-V active material platform, such as an InP waveguide. An anti-reflection coating is applied to the side of the reflective optical amplifier 1 near the comb filter 2. The coating is tilted to reduce residual reflection, and the reflectivity of the coating is less than 0.01%. The phase shifter 5, comb filter 2, wavelength division multiplexer 3, and reflector 4 are integrated on a photonic integrated chip. The platform of the photonic integrated chip in this embodiment can be SOI (silicon on insulator), SiN (silicon nitride on silicon), or LNOI (lithium niobate thin film). In this embodiment, the comb filter 2 is fabricated using an up-downlink high-quality microring resonator with a high quality factor (Q factor) to further narrow the laser output linewidth during continuous frequency modulation. The wavelength division multiplexer 3 is implemented using a flat-top arrayed waveguide grating (AWG), an etched diffraction grating, or a cascaded Mach-Zehnder interferometer (MZI). This allows for a flat-top response design, minimizing laser output power fluctuations during continuous frequency modulation. The reflective optical amplifier 1 and the photonic integrated chip are hybrid-integrated through end-to-end docking, avoiding the use of discrete optical elements such as lenses, thereby greatly improving the integration of the laser.

[0084] In this embodiment, the reflector 4 is a Bragg reflector, and its reflectivity and transmittance can be determined by designing and optimizing grating parameters.

[0085] Example 4

[0086] See also Figure 5 This embodiment provides a multi-wavelength narrow-linewidth laser, comprising: a reflective optical amplifier 1, a comb filter 2, a wavelength division multiplexer 3, a phase shifter 5, and a reflective unit array. The output of the reflective optical amplifier 1 and the input of the comb filter 2 are connected via the phase shifter 5. The wavelength division multiplexer 3 has an input and at least two outputs. The reflective unit array includes at least two reflectors 4. The output of the comb filter 2 is connected to the input of the wavelength division multiplexer 3, and each output of the wavelength division multiplexer 3 is connected to a reflector 4. The reflectors 4 are transflective structures. A high-reflective film 11 is provided on the side of the reflective optical amplifier 1 away from the comb filter 2. The reflectivity of the high-reflective film 11 is greater than 90%. The high-reflective film 11 and the reflectors 4 enclose a resonant cavity. The reflective optical amplifier 1 can generate seed light within the resonant cavity. The phase shifter 5 has a tuning electrode to adjust the phase within the resonant cavity via an electrical signal.

[0087] Compared with the first embodiment, the reflective optical amplifier 1, the comb filter 2, the wavelength division multiplexer 3, the phase shifter 5 and the reflective unit array in this embodiment have the same performance and structural parameters. Therefore, the working principle of this embodiment is the same as that of the first embodiment and will not be repeated here.

[0088] In this embodiment, the reflective optical amplifier 1 is fabricated based on a III-V active material platform, such as an InP waveguide. An anti-reflection coating is applied to the side of the reflective optical amplifier 1 near the comb filter 2. The coating is tilted to reduce residual reflection, and the reflectivity of the coating is less than 0.01%. The phase shifter 5, comb filter 2, wavelength division multiplexer 3, and reflector 4 are integrated on a photonic integrated chip. The platform of the photonic integrated chip in this embodiment can be SOI (silicon on insulator), SiN (silicon nitride on silicon), or LNOI (lithium niobate thin film). The comb filter 2 in this embodiment is fabricated using a high-quality (Q) microring resonator with an upload-download structure to further narrow the laser output linewidth during continuous frequency modulation. The wavelength division multiplexer 3 is implemented using a flat-top arrayed waveguide grating (AWG), allowing it to be designed with a flat-top response, minimizing laser output power fluctuations during continuous frequency modulation. The reflective optical amplifier 1 and the photonic integrated chip are hybrid-integrated through end-to-end docking, avoiding the use of discrete optical elements such as lenses, thereby greatly improving the integration of the laser.

[0089] In this embodiment, reflector 4 is a Sagnac loop reflector. Theoretically, its reflectivity R can be designed to be between 0 and 100%. Neglecting device losses, its transmittance T satisfies the following: T = 1 - R. The target reflectivity (or transmittance) can be determined by designing and optimizing the coupling coefficient of its coupler.

[0090] Example 5

[0091] See also Figure 6 This embodiment provides a multi-wavelength narrow-linewidth laser, comprising: a reflective optical amplifier 1, a comb filter 2, a wavelength division multiplexer 3, a phase shifter 5, and a reflective unit array. The output of the reflective optical amplifier 1 and the input of the comb filter 2 are connected via the phase shifter 5. The wavelength division multiplexer 3 has an input and at least two outputs. The reflective unit array includes at least two reflectors 4. The output of the comb filter 2 is connected to the input of the wavelength division multiplexer 3, and each output of the wavelength division multiplexer 3 is connected to a reflector 4. The reflectors 4 are transflective structures. A high-reflective film 11 is provided on the side of the reflective optical amplifier 1 away from the comb filter 2. The reflectivity of the high-reflective film 11 is greater than 90%. The high-reflective film 11 and the reflectors 4 enclose a resonant cavity. The reflective optical amplifier 1 can generate seed light within the resonant cavity. The phase shifter 5 has a tuning electrode to adjust the phase within the resonant cavity via an electrical signal.

[0092] Compared with the first embodiment, the reflective optical amplifier 1, the comb filter 2, the wavelength division multiplexer 3, the phase shifter 5 and the reflective unit array in this embodiment have the same performance and structural parameters. Therefore, the working principle of this embodiment is the same as that of the first embodiment and will not be repeated here.

[0093] In this embodiment, the reflective optical amplifier 1 is fabricated based on a III-V active material platform, such as an InP waveguide. An anti-reflection coating is applied to the side of the reflective optical amplifier 1 near the comb filter 2. The coating is tilted to reduce residual reflection, and the reflectivity of the coating is less than 0.01%. The phase shifter 5, comb filter 2, wavelength division multiplexer 3, and reflector 4 are integrated on a photonic integrated chip. The platform of the photonic integrated chip in this embodiment can be SOI (silicon on insulator), SiN (silicon nitride on silicon), or LNOI (lithium niobate thin film). The comb filter 2 in this embodiment is fabricated using a high-quality (Q) microring resonator with an upload-download structure to further narrow the laser output linewidth during continuous frequency modulation. The wavelength division multiplexer 3 is implemented using a flat-top arrayed waveguide grating (AWG), allowing it to be designed with a flat-top response, minimizing laser output power fluctuations during continuous frequency modulation.

[0094] The reflectivity of reflector 4 significantly impacts the laser's threshold, output power, and laser linewidth. Different system losses or output power requirements often require matching different reflectivity parameters. If a Bragg reflector or Sagnac loop reflector is used as reflector 4, its reflectivity and transmittance are fixed and cannot be adjusted once the design and fabrication are complete.

[0095] Based on this, reflector 4 in this embodiment is a Sagnac loop reflector based on a Mach-Zehnder Interconnect (MZI) switch. Its reflectivity (or transmittance) depends not only on the parameters of the connected coupler but also on the phase difference between the two arms of the MZI. After device fabrication, the reflectivity of reflector 4 can be flexibly adjusted by controlling the phase difference between the two arms of the MZI, thereby matching the actual system losses and ensuring high-performance operation of the laser. Theoretically, by adjusting the phase difference between the two arms of the MZI, the reflectivity of reflector 4 in this embodiment can be adjusted within a range of 0-100%.

[0096] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A multi-wavelength narrow linewidth laser, characterized in that: include: A reflective optical amplifier (1), wherein the reflective optical amplifier (1) is used to generate seed light; a comb filter (2), the input end of the comb filter (2) being connected to the output end of the reflective optical amplifier (1); and A wavelength division multiplexer (3), the wavelength division multiplexer (3) having an input end and at least two output ends, the input end of the wavelength division multiplexer (3) being connected to the output end of the comb filter (2); The multi-wavelength narrow linewidth laser satisfies: Δf ch(WDM) = m×Δf (filter) ; δf (WDM) <Δf (filter) ;and f FSR(WDM) > Δf (gain) ; Where Δf (filter) is the frequency spacing of the comb filter (2), Δf ch(WDM) is the main frequency channel spacing of the wavelength division multiplexer (3), δf (WDM) is the 3dB bandwidth of a single channel of the wavelength division multiplexer (3), m is a positive integer not less than 2, Δf (gain) is the 3dB gain bandwidth of the reflective optical amplifier (1), f FSR(WDM) is the free spectral range of the wavelength division multiplexer (3).

2. The multi-wavelength narrow linewidth laser according to claim 1, characterized in that: The multi-wavelength narrow linewidth laser further comprises a reflection unit array, the reflection unit array comprises at least two reflectors (4), and each output end of the wavelength division multiplexer (3) is connected to one of the reflectors (4); The reflector (4) is a transflective structure, and a high-reflection film (11) is provided on a side of the reflective optical amplifier (1) away from the comb filter (2), and the high-reflection film (11) and the reflector (4) are surrounded to form a resonant cavity.

3. The multi-wavelength narrow linewidth laser according to claim 2, characterized in that: The multi-wavelength narrow linewidth laser further comprises a phase shifter (5), which is connected between the output end of the reflective optical amplifier (1) and the input end of the comb filter (2) to adjust the phase in the resonant cavity.

4. The multi-wavelength narrow linewidth laser according to claim 3, characterized in that: The comb filter (2), the wavelength division multiplexer (3), the reflector (4) and the phase shifter (5) are integrated on a photonic integrated chip.

5. The multi-wavelength narrow linewidth laser according to claim 2 or claim 3 or claim 4, characterized in that: The multi-wavelength narrow linewidth laser further includes at least two optical power amplifiers (6), the optical power amplifiers (6) corresponding to the reflectors (4) on a one-to-one basis, and the optical power amplifiers (6) are connected to the output ends of the corresponding reflectors (4) to increase the laser output power of the corresponding reflectors (4).

6. The multi-wavelength narrow linewidth laser according to claim 2, characterized in that: The reflector (4) is a Sagnac loop reflector or a Bragg reflector.

7. The multi-wavelength narrow linewidth laser according to claim 1, characterized in that: The comb filter (2) has a tuning electrode to allow the comb filter (2) to simultaneously adjust the center frequencies of its own frequency channels through an electrical signal.

8. The multi-wavelength narrow linewidth laser according to claim 7, characterized in that: The center frequency of one frequency channel of the comb filter (2) is f n , n is a positive integer; The number of output terminals of the wavelength division multiplexer (3) is N, and the center frequency of one of the main frequency channels of the wavelength division multiplexer (3) is f chK , 1≤K≤N and K is an integer; The multi-wavelength narrow linewidth laser satisfies: f chK -δf (WDM) / 2≤f n ≤f chK +δf (WDM) / 2。 9. The multi-wavelength narrow linewidth laser according to claim 8, characterized in that: The 3dB gain bandwidth endpoint values of the reflective optical amplifier (1) are F1 and F2, where F1 <F2; The center frequencies of the two sub-frequency channels of the wavelength division multiplexer (3) are f -1 chN and f +1 ch1 , where f chN -f -1 chN =f +1 ch1 -f ch1 =f FSR(WDM) , f FSR(WDM) ≥N×Δf ch(WDM) ; The multi-wavelength narrow linewidth laser satisfies: f -1 chN +δf (WDM) / 2<F1≤f n ;and F2<f +1 ch1 -δf (WDM) / 2。 10. The multi-wavelength narrow linewidth laser according to claim 1, characterized in that: The transmission spectrum of the wavelength division multiplexer (3) is designed to be a flat-top response, and the loss difference between any two main frequency channels of the wavelength division multiplexer (3) is less than 1 dB.

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