Multi-wavelength narrow linewidth laser

Abstract

The invention relates to a multi-wavelength narrow-linewidth laser, comprising: a reflective optical amplifier for generating seed light; the input end of the comb filter is connected with the output end of the reflective optical amplifier; the wavelength division multiplexer is provided with an input end and at least two output ends, and the input end of the wavelength division multiplexer is connected with the output end of the comb filter; the multi-wavelength narrow linewidth laser meets the following condition: [delta] fch (WDM) = m * [delta] f (filter), delta f (WDM) lt; [delta] f (filter); and fFSR (WDM) gt; [delta] f (gain); wherein delta f (filter) is the frequency interval of the comb filter, delta fch (WDM) is the frequency channel interval of the wavelength division multiplexer, delta f (WDM) is the 3dB bandwidth of a single channel of the wavelength division multiplexer, m is a positive integer not less than 2, delta f (gain) is the 3dB gain bandwidth of the reflective optical amplifier, and fFSR (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, and particularly to a multi-wavelength narrow linewidth laser. Background Art

[0002] Wavelength Division Multiplexing (WDM) technology has shown broad application prospects in multiple fields such as optical communication, optical interconnection, optical computing, and optical sensing due to its unique parallel transmission ability and high bandwidth utilization efficiency. With the continuous progress of WDM technology and the expansion of application fields, the demand for low-cost and high-performance multi-channel multi-wavelength light sources is also continuously increasing.

[0003] Traditional multi-wavelength light sources require a laser array composed of multiple independent high-performance single-wavelength lasers. Their manufacturing process is complex. During the process of continuous frequency modulation, each wavelength channel needs to be controlled separately. Therefore, such multi-wavelength light sources not only have high power consumption and large volume, but also are costly, and the operation steps required to achieve continuous frequency modulation are 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 volume, and complex continuous frequency modulation operation steps of existing multi-wavelength light sources.

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

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

[0007] A reflective optical amplifier for generating seed light;

[0008] A comb filter, the input end of which is connected to the output end of the reflective optical amplifier; and

[0009] A wavelength division multiplexer having one input end and at least two output ends, the input end of which is 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] wherein, Δf (filter)is the frequency interval of the comb filter, Δf ch(WDM) is the main frequency channel interval 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 transmissive and reflective structure, and a high-reflection film is arranged on the side of the reflective optical amplifier away from the comb filter, and the high-reflection film and the reflector enclose a resonant cavity.

[0017] In some embodiments, the multi-wavelength narrow linewidth laser further includes a phase shifter, and the phase shifter is 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, the optical power amplifiers correspond to the reflectors one by one, and the optical power amplifiers are connected to the output ends of the corresponding reflectors to increase the laser output power of the corresponding reflectors.

[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 frequencies of its respective frequency channels through an electrical signal.

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

[0023] The number of output ends 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 3 dB gain bandwidth endpoint values of the reflective optical amplifier are F1 and F2, where F1 < F2;

[0027] The central frequencies of 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 have 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 selects and filters the modes of the laser by cascading a comb filter and a wavelength division multiplexer, realizing the output of multi-wavelength narrow linewidth laser. Compared with the method of laser array, the multi-wavelength narrow linewidth laser of the present invention has the advantages of small volume, low cost, and simple preparation.

[0034] 2. For the cascaded structure of the comb filter and the wavelength division multiplexer, the comb filter first screens the seed light generated by the reflective optical amplifier and outputs a large number of narrow spectral signals with different frequencies. When satisfying Δf ch(WDM) = m×Δf (filter) and δf(WDM) <Δf (filter) Under the conditions of the two conditions, in coordination with the tuning of the comb filter, then each frequency channel of the wavelength division multiplexer is used to perform secondary screening on the output light of the comb filter, enhancing the mode selection ratio of the laser. The line width of the laser finally output can be further compressed, and at the same time, multiple output channels are provided for the multi-wavelength narrow line width 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 spectral range of the wavelength division multiplexer), therefore, based on f FSR(WDM) >Δf (gain) This relational expression, one of the frequency channels corresponding to the output port will be used as the main frequency channel, and the remaining corresponding frequency channels will be used as secondary frequency channels. Further based on the mode competition theory of the laser, only the optical signal in the main frequency channel can meet the threshold condition, and then laser is output from the corresponding output port. The optical signals in the secondary frequency channels cannot form laser output because they do not meet the threshold condition, thus ensuring stable single-wavelength narrow line width laser output at each output port.

[0036] 4. Based on Δf ch(WDM) = m×Δf (filter) 、δf (WDM) <Δf (filter) And f FSR(WDM) > Δf (gain) These three relational expressions, by simply tuning the comb filter, the multi-wavelength lasers output from each output end of the wavelength division multiplexer can be synchronously and continuously frequency modulated. Therefore, its continuous frequency modulation method is simple and can meet the application requirements of scenarios including FMCW lidar. Description of the Drawings

[0037] Figure 1 It is the topology diagram of the multi-wavelength narrow line width laser in Embodiment 1 of the present invention;

[0038] Figure 2 It is the parameter schematic diagram of the multi-wavelength narrow line width laser in Embodiment 1 of the present invention;

[0039] Figure 3 It is the topology diagram of the multi-wavelength narrow line width laser in Embodiment 2 of the present invention;

[0040] Figure 4 It is the planar structure schematic diagram of the multi-wavelength narrow line width laser in Embodiment 3 of the present invention;

[0041] Figure 5 It is the planar structure schematic diagram of the multi-wavelength narrow line width laser in Embodiment 4 of the present invention;

[0042] Figure 6 This is a schematic plan view of the multi-wavelength narrow linewidth laser in the fifth embodiment 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 implementation manners

[0045] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the detailed implementation manners of the present invention with reference to the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0046] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation 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 thus should not be construed as limiting the present invention.

[0047] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0048] In the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may mean 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 mean 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 mean 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 can 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 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] See 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 an 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 the 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 the 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, in other words F2 - F1 = Δf (gain) .

[0055] The center frequencies of the respective 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 a tuning electrode to allow the comb filter 2 to adjust the center frequencies of its respective frequency channels simultaneously through an electrical signal.

[0056] The number of output terminals of the wavelength division multiplexer 3 is N, and these N output terminals are ch1, ch2,..., chN in sequence. The center frequencies of the respective frequency channels of the wavelength division multiplexer 3 are..., 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 terminal of the wavelength division multiplexer 3 will correspond to multiple frequency channels, and each output terminal can output the optical signal in the corresponding frequency channel when the threshold condition is met. Taking the output terminal ch1 as an example, the frequency channels with center frequencies of..., f -1 ch1 , f ch1 , f +1 ch1 , f +2 ch1 ,... correspond to the output terminal ch1, and the optical signal in the frequency channels with center frequencies of..., f -1 ch1 , f ch1 , f +1 ch1 , f +2 ch1 ,... will be output through the output terminal ch1 when the threshold condition is met. By analogy, the frequency channels with center frequencies of..., f -2 chN , f -1 chN , fchN , f +1 chN ,... the corresponding output terminal chN of the frequency channel with a center frequency of..., f -2 chN , f -1 chN , f chN , f +1 chN ,... the optical signals in the frequency channels 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 elaborated in this embodiment.

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

[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 channels with center frequencies of f ch1 , f ch2 ,... f chN can be regarded as a group of frequency channels, and the frequency channels with center frequencies of f ch(WDM) , f

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

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

[0061] It should be particularly noted that, on the basis of meeting the basic characteristics of the foregoing device, the multi-wavelength narrow linewidth laser of this embodiment further satisfies: 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, and δf (WDM) is the 3dB bandwidth of a single channel of the wavelength division multiplexer 3.

[0062] Regarding the relationship f FSR(WDM) > Δf (gain) , in this embodiment, it is specifically manifested as: f -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 satisfy 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 the relationship Δf ch(WDM) = m×Δf (filter) , when the relationship f ch1 -δf (WDM) / 2 ≤ f n ≤ f ch1 +δf (WDM) / 2 is satisfied, the following will also be satisfied at the same time ≤ ,..., ≤ ≤ 。

[0064] Exemplarily, in some other embodiments, the comb filter 2 can be tuned according to requirements to satisfy 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,... The similar situations are not elaborated in this embodiment.

[0065] The comb filter 2 filters the continuous-frequency light generated by the reflective optical amplifier 1. Based on the above relational expressions, 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 optical signals with center frequencies of f n , f n+1 ,..., f n+（N-1）m . The bandwidths of each frequency channel in the transmission spectrum of the comb filter 2 are very narrow, providing a basis for the linewidth compression and continuous frequency tuning of the subsequent multi-wavelength laser.

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

[0067] Based on the relational expression of δf (WDM) <Δf (filter) , taking the frequency channel with a center frequency of f ch1 of the wavelength division multiplexer 3 as an example, this channel only allows the optical signal with a frequency of f n output by the comb filter 2 to pass through, and the optical signals with frequencies of f n-1 and f n+1 output by the comb filter 2 cannot enter the wavelength division multiplexer 3 with a center frequency of f ch1The frequency channels. The other frequency channels of the wavelength division multiplexer 3 have similar characteristics, which will not be elaborated in this embodiment. In other words, each frequency channel of the wavelength division multiplexer 3 only allows one of the frequency optical signals output by the comb filter 2 to pass through, thereby realizing the function of secondary filtering after the comb filter 2 and increasing the mode selection ratio of the laser.

[0068] Based on the foregoing f FSR(WDM) > Δf (gain) From this relational expression, it can be seen that in addition to the frequency channel with the center frequency of f ch1 , f ch2 ,..., f chN of the wavelength division multiplexer 3, for the remaining frequency channels (such as the frequency channels with the center frequencies of f +1 ch1 and f -1 chN ), even if there is an optical signal output by the comb filter 2, this optical signal must not be within the 3dB gain bandwidth of the reflective optical amplifier 1. Therefore, the corresponding frequency energy is very small and cannot form a laser output. Thus, each output end ch1, ch2,..., chN of the wavelength division multiplexer 3 can only output single-frequency laser, and the corresponding output frequencies are f n , f n+m ,..., f n+（N-1）m , thereby 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 frequency channels of the wavelength division multiplexer 3 with the center frequencies of f ch1 , f ch2 ,..., f chN are used as the main frequency channels, and Δf ch(WDM) is the center frequency interval between adjacent two 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 frequencies. In addition, based on Δf ch(WDM) = m×Δf (filter) and δf (WDM) <Δf (filter) the two relational expressions, the wavelength division multiplexer 3 performs secondary filtering on the laser output by the comb filter 2, increasing the mode selection ratio of the laser.

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

[0073] 3. It is only necessary to continuously tune the comb filter 2 under the condition that f chK -δf (WDM) / 2 ≤ f n ≤ f chK +δf (WDM) / 2, and the frequencies of f n , f n+m ,..., f n+（N-1）m can be changed synchronously, and then the multi-wavelength laser output by the laser can be synchronously and continuously frequency-modulated to meet the usage requirements of the FMCW lidar.

[0074] Preferably, the wavelength division multiplexer 3 is designed with 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 significantly and fluctuate, so as to maintain the stability of the optical power output by the laser.

[0075] Further preferably, the loss difference between any two main frequency channels of the wavelength division multiplexer 3 is less than 1 dB, so as to ensure that the optical signals in each main frequency channel of the multi-wavelength narrow linewidth laser simultaneously meet the threshold conditions, and the optical power in each main frequency channel is substantially the same, and then ensure that the power difference between the different frequency lasers output by the final laser is small.

[0076] Embodiment 2

[0077] Referring to Figure 3 , 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 an 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 the 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 the side of the reflective optical amplifier 1 close to 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 reflection unit array have the same performance and structural parameters. Therefore, this embodiment has the same working principle as the first embodiment and will not be elaborated herein.

[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 the optical power amplifiers 6 matches the number of the reflectors 4, so that the optical power amplifiers 6 correspond to the reflectors 4 one by one. The optical power amplifier 6 is connected to the output end of the corresponding reflector 4 to optically amplify the laser with a specific frequency output from the reflector 4.

[0080] Embodiment Three

[0081] Refer to Figure 4 , 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 reflection unit 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 reflection unit 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 11 is provided on the side of the reflective optical amplifier 1 away from the comb filter 2. The reflectivity of the high-reflection film 11 is greater than 90%. The high-reflection film 11 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.

[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 reflection unit array have the same performance and structural parameters. Therefore, this embodiment has the same working principle as the first embodiment and will not be elaborated herein.

[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 antireflection film is provided on the side of the reflective optical amplifier 1 close to the comb filter 2. The antireflection film is provided with a certain inclination angle to reduce the residual reflection, and the reflectivity of the antireflection film is less than <0.01%. The phase shifter 5, the comb filter 2, the wavelength division multiplexer 3, and the 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-based silicon nitride), or LNOI (thin-film lithium niobate). The comb filter 2 in this embodiment is fabricated by an up-down type high-quality factor (Q value) microring resonator to further narrow the linewidth of the laser output during continuous frequency modulation. The wavelength division multiplexer 3 is based on a flat-top arrayed waveguide grating AWG, an etched diffraction grating, or a cascaded Mach-Zehnder interferometer to allow the wavelength division multiplexer 3 to be designed with a flat-top response and reduce the laser output power fluctuation during continuous frequency modulation. The reflective optical amplifier 1 and the photonic integrated chip are hybrid integrated by end-to-end docking, avoiding the use of discrete optical components such as lenses, which greatly improves 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 the grating parameters.

[0085] Embodiment 4

[0086] See Figure 5 , 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 unit 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 unit 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 to a reflector 4. The reflector 4 is a transmissive and reflective structure. A high-reflection film 11 is provided on the side of the reflective optical amplifier 1 away from the comb filter 2. The reflectivity of the high-reflection film 11 is greater than 90%. The high-reflection film 11 and the reflector 4 enclose a resonant cavity. 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.

[0087] Compared with Embodiment 1, the reflective optical amplifier 1, the comb filter 2, the wavelength division multiplexer 3, the phase shifter 5, and the reflector unit array in this embodiment have the same performance and structural parameters. Therefore, this embodiment has the same working principle as Embodiment 1 and will not be elaborated 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 antireflection film is provided on one side of the reflective optical amplifier 1 close to the comb filter 2. The antireflection film is provided with a certain inclination angle to reduce the residual reflection, and the reflectivity of the antireflection film is less than <0.01%. The phase shifter 5, the comb filter 2, the wavelength division multiplexer 3, and the 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-based silicon nitride), or LNOI (thin-film lithium niobate). The comb filter 2 in this embodiment is fabricated by an up / down-loading type high-quality factor (Q value) micro-ring resonator to further narrow the linewidth of the laser output during the continuous frequency modulation process. The wavelength division multiplexer 3 is based on a flat-top arrayed waveguide grating AWG to allow the wavelength division multiplexer 3 to be designed with a flat-top response and reduce the laser output power fluctuation during continuous frequency modulation. The reflective optical amplifier 1 and the photonic integrated chip are hybrid integrated by end-to-end docking, avoiding the use of discrete optical components such as lenses, and greatly improving the integration of the laser.

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

[0090] Embodiment Five

[0091] See Figure 6 , 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 unit 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 unit 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 to a reflector 4. The reflector 4 is a transmissive / reflective structure. A high-reflection film 11 is provided on the side of the reflective optical amplifier 1 away from the comb filter 2. The reflectivity of the high-reflection film 11 is greater than 90%. The high-reflection film 11 and the reflector 4 enclose a resonant cavity. 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.

[0092] Compared with Embodiment One, the reflective optical amplifier 1, the comb filter 2, the wavelength division multiplexer 3, the phase shifter 5, and the reflector unit array in this embodiment have the same performance and structural parameters. Therefore, this embodiment has the same working principle as Embodiment One and will not be elaborated 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 antireflection film is provided on the side of the reflective optical amplifier 1 close to the comb filter 2. The antireflection film is provided with a certain inclination angle to reduce the residual reflection, and the reflectivity of the antireflection film is less than <0.01%. The phase shifter 5, the comb filter 2, the wavelength division multiplexer 3, and the 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-based silicon nitride), or LNOI (thin-film lithium niobate). The comb filter 2 in this embodiment is prepared by an up-down type high-quality factor (Q value) microring resonator to further narrow the linewidth of the laser output during the continuous frequency modulation process. The wavelength division multiplexer 3 is based on a flat-top arrayed waveguide grating AWG to allow the wavelength division multiplexer 3 to be designed with a flat-top response and reduce the laser output power fluctuation during continuous frequency modulation.

[0094] The reflectivity of the reflector 4 has an important impact on the threshold, output power, laser linewidth, etc. of the laser. Different system losses or output power requirements often require matching different reflectivity parameters. If the reflector 4 selects a Bragg reflector or a Sagnac loop reflector, once designed and fabricated, the reflectivity and transmittance are fixed values and cannot be adjusted.

[0095] Based on this, the reflector 4 in this embodiment is a Sagnac loop reflector based on a Mach-Zehnder (MZI) switch. Its reflectivity (or transmittance) is related not only to the parameters of the coupler it is connected to but also to the phase difference between the two arms of the MZI. After the device is fabricated, the reflectivity of the reflector 4 can be flexibly adjusted by controlling the phase difference between the two arms of the MZI, so as to match the actual system loss and ensure the high-performance working state of the laser. Theoretically, the reflectivity adjustment range of the reflector 4 in this embodiment is between 0 - 100% by adjusting the phase difference between the two arms of the MZI.

[0096] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0097] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A multi-wavelength narrow linewidth laser, characterized in that, Comprising: A reflective optical amplifier (1) for generating seed light; A comb filter (2) whose input end is connected to the output end of the reflective optical amplifier (1); and A wavelength division multiplexer (3) having one input end and at least two output ends, and the input end of the wavelength division multiplexer (3) is 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) ; Among them, Δf (filter) is the frequency interval of the comb filter (2), and Δf ch(WDM) is the main frequency channel interval 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, and 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, wherein The multi-wavelength narrow linewidth laser further includes a reflection unit array, the reflection unit array includes 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 transmissive and reflective structure, and a high reflection film (11) is provided on the side of the reflective optical amplifier (1) away from the comb filter (2), and the high reflection film (11) and the reflector (4) enclose a resonant cavity.

3. The multi-wavelength narrow linewidth laser according to claim 2, wherein The multi-wavelength narrow linewidth laser further includes a phase shifter (5) connected between the output end of the reflective optical amplifier (1) and the input end of the comb filter (2) for adjusting the phase in the resonant cavity.

4. The multi-wavelength narrow linewidth laser according to claim 3, wherein 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) correspond to the reflectors (4) one by one, and the optical power amplifiers (6) are connected to the output ends of the corresponding reflectors (4) for increasing 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, wherein The comb filter (2) has a tuning electrode to allow the comb filter (2) to simultaneously adjust the center frequencies of its respective frequency channels through an electrical signal.

8. The multi-wavelength narrow linewidth laser according to claim 7, wherein The center frequency of one of the frequency channels of the comb filter (2) is f n , where n is a positive integer; The number of output ports 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 , where 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, wherein The 3dB gain bandwidth end point values of the reflective optical amplifier (1) are F1 and F2, where F1 < F2; The center frequencies of 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 have a flat top response, and the loss difference between any two main frequency channels of the wavelength division multiplexer (3) is less than 1dB.

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