CN114825002A - Ultrashort-cavity multi-wavelength single-frequency laser based on doping of different rare earth nanoparticles - Google Patents

Abstract

The invention belongs to the technical field of fiber lasers, in particular to an ultra-short cavity multi-wavelength single-frequency laser doped based on different rare earth nanoparticles. An ultrashort-cavity multi-wavelength single-frequency laser doped with different rare earth nanoparticles includes a pump source, a fiber wavelength division multiplexer, a Bragg grating group, a gain fiber, and a high-reflection mirror arranged in sequence along the optical path; the Bragg grating group An ultra-short linear laser resonator is formed with a high-reflection mirror; the gain fiber is located in the resonator, one end of which is connected to the grid region of the Bragg grating group, and the other end is attached to the high-reflection mirror; the gain fiber is doped Optical fibers of rare earth ions encapsulated by two or more nanoparticles. The invention utilizes the gain fiber doped with different rare earth nanoparticles to realize the ultra-short cavity dual-wavelength laser, not only the structure is far more compact and stable than the existing dual-wavelength laser, and the production cost is low, and the output wavelength spacing is large, good wavelength selectivity.

Description

Ultrashort-cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping

technical field

The invention belongs to the technical field of fiber lasers, in particular to an ultra-short cavity multi-wavelength single-frequency laser doped based on different rare earth nanoparticles.

Background technique

Single-frequency fiber lasers have the advantages of narrow linewidth, low noise, and long coherence length. They have important applications in coherent optical communication, high-precision coherent ranging, coherent lidar, high-precision spectroscopy and gravitational wave detection. Especially in high-precision coherent ranging, the single-frequency laser has a very high measurement accuracy due to its extremely narrow linewidth. However, in some special application environments, such as in atmospheric detection, due to the uneven distribution and random fluctuation of atmospheric refractive index, certain measurement errors are often caused, thereby increasing the uncertainty of ranging. In order to reduce the error in the measurement process and increase the accuracy of the system, two-color interferometry is usually used to compensate for the distance error caused by the refractive index of air. Compared with the traditional coherent ranging system, the two-color coherent measurement system needs to use two single-frequency lasers with different wavelengths as the detection light source at the same time, and the distance between the two wavelengths is required to be large enough to reduce the error introduced by the calculation.

Two-color single-frequency light sources can usually be obtained in two ways. One is by combining two single-frequency lasers with different wavelengths. In this way, two laser systems need to be built separately, and then the two lasers are combined by an additional system. The laser beam combination is performed, so the system is more complicated and the cost is higher. Another way is to use a dual-wavelength single-frequency fiber laser as the light source. There are also two implementation ways for dual-wavelength single-frequency fiber lasers. One is based on a gain fiber, but the two wavelengths generated by this solution are relatively small. And it is necessary to suppress intra-cavity mode competition; the second is to use two kinds of gain fibers to achieve, this scheme usually adopts a double-ring cavity structure and a structure in which two kinds of gain fibers are cascaded into the same linear cavity. The lasers of these structures usually need to insert more Therefore, the structure of this type of laser is complex, the output efficiency is low, and the stability is poor.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the present invention provides an ultra-short cavity multi-wavelength single-frequency laser based on doping of different rare earth nanoparticles. The laser adopts ultra-short cavity structure, which has the advantages of compact structure, high efficiency and stable output. The laser is based on optical fibers doped with different rare-earth nanoparticles as the gain medium and thus can provide multiple wavelengths with sufficiently large spacing.

The technical solution adopted by the present invention to solve the technical problem is as follows: an ultra-short cavity multi-wavelength single-frequency laser doped with different rare earth nanoparticles, including a pump source, a fiber wavelength division multiplexer, a Bragg grating group, a pump source, a fiber wavelength division multiplexer, a Bragg grating group, A gain fiber and a high-reflection mirror; the Bragg grating group and the high-reflection mirror form an ultra-short linear laser resonator; the gain fiber is located in the resonator, one end of which is connected to the grid region of the Bragg grating group, and the other end is connected to the high-reflection mirror The gain fiber is an optical fiber doped with rare earth ions wrapped by two or more nanoparticles.

As a preferred mode of the present invention, the rare earth ions are selected from at least two of Nd ³⁺ , Yb ³⁺ , Er ³⁺ , Tm ³⁺ , Ho ³⁺ , and the doping amount is 5at%~20at% , used to provide laser gain in different wavelength bands.

Further preferably, the length of the resonant cavity is 1.5 cm.

Further preferably, the pumping source is a continuous pumping source or a pulsed pumping source.

Further preferably, the optical fiber wavelength division multiplexer includes three ports, one of which is used as the output end of the dual-wavelength laser, and the wavelength output range is greater than 1000 nm, and the other two ports are respectively connected to the pump source and the laser resonator.

Further preferably, the Bragg grating group is a low-reflectivity Bragg grating with a reflectivity of 50% to 99%, which has two reflection wavelengths in the same grating region, wherein the short-wavelength grating region is located inside the resonator cavity, and the long-wavelength grating region is located inside the resonant cavity. It is located outside the resonator, and the length of the gate region is less than 1 mm.

Further preferably, the Bragg grating group is a polarization-maintaining grating or a non-polarization-maintaining grating.

Further preferably, the high-reflection mirror is coated with a broadband dielectric film, and the reflectivity is not less than 99.9%.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention adopts a compact ultra-short cavity structure to obtain dual-wavelength single-frequency laser output, which is not only far more compact and stable in structure than the existing dual-wavelength lasers, but also low in production cost, and can achieve strong output laser wavelength selectivity. , large spacing and other advantages, solve the problems of the current dual-wavelength single-frequency laser output wavelength spacing is small and the laser structure is complex, poor stability, and difficult to manufacture.

2. The gain fiber used in the present invention provides laser gain in different wavelength bands by doping different rare earth ions, and the rare earth ions are wrapped by nanoparticles, so that mutual interference between different rare earth ions will not occur, and their respective luminescent characteristics will be maintained, which solves the problem. The problem of laser instability caused by energy transfer between rare earth ions in traditional multi-rare earth doped fibers can meet the band requirements of different applications and has wide applicability.

Description of drawings

1 is a schematic structural diagram of an ultra-short-cavity multi-wavelength single-frequency laser based on different rare earth nanoparticle doping provided by the present invention;

2 is a schematic diagram of a doping structure of the gain fiber according to Embodiment 1 of the present invention;

3 is a schematic structural diagram of a Bragg grating group provided by the present invention;

Fig. 4 is the output spectrogram of Example 1 of the present invention;

Among them, 1. Pump source; 2. Optical fiber wavelength division multiplexer; 3. Bragg grating group; 4. Gain fiber; 5. High reflection mirror; 6. Nanoparticles; 7. Rare earth A ³⁺ ; 8. Rare earth B ³⁺ .

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided so that a thorough and complete understanding of the present disclosure will be provided.

Embodiment 1 The structure of the ultrashort cavity dual-wavelength single-frequency laser based on different rare earth nanoparticles doping provided in this embodiment is shown in Figure 1, including a 976 nm pump source 1, a fiber wavelength division multiplexing, and a 976 nm pump source arranged in sequence along the optical path. 2, Bragg grating group 3, gain fiber 4 and high reflection mirror 5.

Among them, the pump source 1 is used to transmit the pump laser, the Bragg grating group 3 and the high reflection mirror form an ultra-short linear laser resonator, and a temperature control system is arranged outside the resonator to adjust and maintain the temperature of the laser resonator. The fiber wave The demultiplexer 2 connects the pump source 1 and the resonator, and injects the 976 nm pump laser emitted from the pump source into the resonator.

The pump source 1 described in this embodiment is a continuous pump source, and the center wavelength is 976 nm.

The optical fiber wavelength division multiplexer 2 described in this embodiment includes three ports, one of which is used as the output end of the dual-wavelength laser with a wavelength output range of 1000-1600 nm, and the other two ports are respectively connected with the pump source 1 and Bragg grating group 3.

The Bragg grating group 3 provided in this embodiment is shown in FIG. 3 . It is a low-reflectivity Bragg grating with a reflectivity of 50% to 99% and a grating region length of 0.5 mm. There are two reflection wavelengths in this grating region, respectively are 1064 nm and 1550 nm, where the short-wavelength grating region is located inside the resonator, and the long-wavelength grating region is located outside the resonator. The Bragg grating group 3 is a non-polarization-maintaining grating, so dual-wavelength laser output can be realized.

The gain fiber 4 provided in this embodiment is an Er/Yb nanoparticle co-doped fiber. As shown in FIG. 2 , the fiber contains Y ₂ O doped with two different rare earth ions, Er ³⁺ ions 7 and Yb ³⁺ ions 8 ₃ nanoparticles 9, rare earth Er ³⁺ 7 and rare earth Yb ³⁺ 8 are respectively wrapped in different Y ₂ O ₃ nanoparticles 9 and do not interfere with each other. The doping amounts of Er ³⁺ ions 7 and Yb ³⁺ ions 8 in the gain fiber are 10 at% and 10 at%, respectively. Among them, Er ³⁺ provides laser gain at 1550 nm wavelength, Yb ³⁺ provides laser gain at 1064 nm wavelength, and the length of Er/Yb nanoparticle co-doped fiber is 1 cm.

As the laser gain medium, the Er/Yb nanoparticle co-doped gain fiber is located in the resonant cavity. One end of the fiber is directly connected to the gate region of the Bragg grating group 3 by welding, and the other end is attached to the high-reflection mirror, which is used to provide the intracavity system at the same time. Laser gain in the 1 μm and 1.5 μm bands. The cavity length of the laser resonator is only 1.5 cm, which ensures a sufficiently large longitudinal mode interval in the cavity. At the same time, the Bragg grating group 3 is a dual-wavelength narrow-band grating, and the two center wavelengths are located at 1 μm and 1.5 μm respectively, which are used to realize the wavelength and mode The choice of , finally realizes the output of 1 μm and 1.5 μm dual-wavelength single-frequency laser, as shown in Figure 4.

The high-reflection mirror 5 in this embodiment is coated with a broadband dielectric film, and the reflectivity is not less than 99.9%.

Embodiment 2 The structure of the ultra-short cavity dual-wavelength single-frequency laser based on different rare earth nanoparticles doping provided in this embodiment is shown in Figure 1, including a 976 nm pump source 1, a fiber wavelength division multiplexing, and a 976 nm pump source 1 arranged in sequence along the optical path. 2, Bragg grating group 3, gain fiber 4 and high reflection mirror 5.

Among them, the pump source 1 is used to transmit the pump laser, the Bragg grating group 3 and the high reflection mirror form an ultra-short linear laser resonator, and a temperature control system is arranged outside the resonator to adjust and maintain the temperature of the laser resonator. The fiber wave The demultiplexer 2 connects the pump source 1 and the resonator, and injects the 976 nm pump laser emitted from the pump source into the resonator.

The pump source 1 described in this embodiment is a pulsed pump source, and the center wavelength is 976 nm to realize pulsed dual-wavelength single-frequency laser output.

The optical fiber wavelength division multiplexer 2 described in this embodiment includes three ports, one of which is used as the output end of the dual-wavelength laser with a wavelength output range of 1000-1600 nm, and the other two ports are respectively connected with the pump source 1 and Bragg grating group 3.

The Bragg grating group 3 in this embodiment is a low-reflectivity Bragg grating with a reflectivity of 50% to 99% and a grating region length of 0.5 mm. There are two reflection wavelengths in this grating region, 1064 nm and 1940 nm, respectively. The short-wavelength grating region is located inside the resonator cavity, and the long-wavelength grating region is located outside the resonant cavity. The Bragg grating group 3 is a non-polarization-maintaining grating, so dual-wavelength laser output can be realized.

The gain fiber provided in this embodiment is a Yb/Tm nanoparticle co-doped gain fiber. The optical fiber contains Y ₂ O ₃ nanoparticles doped with two different rare earth ions, Yb ³⁺ ions and Tm ³⁺ ions, and rare earth Yb ^{3+ ions} . The ions and Tm ³⁺ ions are encapsulated in different Y ₂ O ₃ nanoparticles, respectively, without interfering with each other. The doping amounts of Yb ³⁺ ions and Tm ³⁺ ions in the gain fiber are 10at% and 15at%, respectively. Among them, Yb ³⁺ provides laser gain at 1064 nm wavelength, Tm ³⁺ provides laser gain at 1940 nm wavelength, and the length of Yb/Tm nanoparticle co-doped gain fiber is 1 cm.

The Yb/Tm nanoparticle co-doped gain fiber is used as the laser gain medium, which is located in the resonator cavity. One end of the fiber is directly connected to the gate region of the Bragg grating group 3 by welding, and the other end is attached to the high-reflection mirror, which is used to provide the intracavity at the same time. Laser gain in the 1 μm and 2 μm bands. The cavity length of the laser resonator is only 1.5 cm, which ensures a sufficiently large longitudinal mode interval in the cavity. At the same time, the Bragg grating group 3 is a dual-wavelength narrow-band grating, and the two center wavelengths are located at 1 μm and 2 μm respectively, which are used to realize the wavelength and mode Finally, the output of 1 μm and 2 μm dual-wavelength single-frequency laser is realized.

The high-reflection mirror 5 in this embodiment is coated with a broadband dielectric film, and the reflectivity is not less than 99.9%.

Embodiment 3 The structure of the ultra-short cavity three-wavelength single-frequency laser based on different rare earth nanoparticles doping provided in this embodiment is shown in Figure 1, including a 976 nm pump source 1, a fiber wavelength division multiplexing, and a 976 nm pump source arranged in sequence along the optical path. 2, Bragg grating group 3, gain fiber 4 and high reflection mirror 5.

Among them, the pump source 1 is used to transmit the pump laser, the Bragg grating group 3 and the high reflection mirror form an ultra-short linear laser resonator, and a temperature control system is arranged outside the resonator to adjust and maintain the temperature of the laser resonator. The fiber wave The demultiplexer 2 connects the pump source 1 and the resonator, and injects the 976 nm pump laser emitted from the pump source into the resonator.

The pump source 1 described in this embodiment is a pulsed pump source, and the center wavelength is 976 nm to realize pulsed dual-wavelength single-frequency laser output.

The optical fiber wavelength division multiplexer 2 described in this embodiment includes three ports, one of which is used as the output end of the dual-wavelength laser with a wavelength output range of 1000-1600 nm, and the other two ports are respectively connected with the pump source 1 and Bragg grating group 3.

The Bragg grating group 3 described in this embodiment is a low-reflectivity Bragg grating with a reflectivity of 50% to 99% and a grating region length of 0.5 mm. There are three reflection wavelengths in this grating region, which are 1064 nm and 1550 nm respectively. and 1940nm, where the short-wavelength grating region is located inside the resonator cavity, and the long-wavelength grating region is located outside the resonant cavity. The Bragg grating group 3 is a non-polarization-maintaining grating, so three-wavelength laser output can be realized.

The gain fiber 4 provided in this embodiment is an Er/Yb/Tm nanoparticle co-doped fiber, and the fiber contains Y ₂ O ₃ doped with three different rare earth ions: Er ³⁺ ions, Yb ³⁺ ions, and Tm ³⁺ ions Nanoparticles, rare earth Er ³⁺ , rare earth Yb ³⁺ , rare earth Tm ³⁺ are encapsulated in different Y ₂ O ₃ nanoparticles respectively, and will not interfere with each other. The doping amounts of Er ³⁺ ions, Yb ³⁺ ions and Tm ³⁺ ions in the gain fiber are 10at%, 10at% and 15at%, respectively. Among them, Er ³⁺ provides laser gain at 1550 nm wavelength, Yb ³⁺ provides laser gain at 1064 nm wavelength, Tm ³⁺ provides laser gain at 1940 nm wavelength, and the length of the Er/Yb/Tm nanoparticle co-doped fiber is 1 cm.

As the laser gain medium, the Er/Yb/Tm nanoparticle co-doped fiber is located in the resonant cavity. One end of the fiber is directly connected to the gate region of the Bragg grating group 3 by welding, and the other end is attached to the high-reflection mirror to provide the cavity at the same time. Laser gain in the 1 μm, 1.5 μm and 2 μm bands. The cavity length of the laser resonator is only 1.5 cm, which ensures a sufficiently large longitudinal mode interval in the cavity. At the same time, the Bragg grating group 3 is a three-wavelength narrow-band grating whose center wavelengths are located at 1 μm, 1.5 μm, and 2 μm, respectively. The selection of wavelength and mode finally realizes the output of 1 μm, 1.5 μm and 2 μm three-wavelength single-frequency laser.

Embodiment 4 The structure of the ultrashort cavity four-wavelength single-frequency laser based on different rare earth nanoparticles doping provided in this embodiment is shown in Figure 1, including a 976 nm pump source 1, a fiber wavelength division multiplexing, and a 976 nm pump source 1 arranged in sequence along the optical path 2, Bragg grating group 3, gain fiber 4 and high reflection mirror 5.

Among them, the pump source 1 is used to transmit the pump laser, the Bragg grating group 3 and the high reflection mirror form an ultra-short linear laser resonator, and a temperature control system is arranged outside the resonator to adjust and maintain the temperature of the laser resonator. The fiber wave The demultiplexer 2 connects the pump source 1 and the resonator, and injects the 976 nm pump laser emitted from the pump source into the resonator.

The pump source 1 described in this embodiment is a pulsed pump source, and the center wavelength is 976 nm to realize pulsed dual-wavelength single-frequency laser output.

The optical fiber wavelength division multiplexer 2 described in this embodiment includes three ports, one of which is used as the output end of the dual-wavelength laser with a wavelength output range of 1000-1600 nm, and the other two ports are respectively connected with the pump source 1 and Bragg grating group 3.

The Bragg grating group 3 described in this embodiment is a low-reflectivity Bragg grating with a reflectivity of 50% to 99% and a grating region length of 0.5 mm. There are two reflection wavelengths in this grating region, which are 1064 nm and 1550 nm respectively. nm, where the short-wavelength grating region is located inside the resonator, and the long-wavelength grating region is located outside the resonator. The Bragg grating group 3 is a polarization-maintaining grating, so four-wavelength laser output can be realized.

The gain fiber 4 provided in this embodiment is an Er/Yb nanoparticle co-doped fiber. The optical fiber contains Y ₂ O ₃ nanoparticles doped with two different rare earth ions, Er ³⁺ ions and Yb ³⁺ ions, and rare earth Er ^{3+ ions} . , Rare earth Yb ³⁺ are encapsulated in different Y ₂ O ₃ nanoparticles respectively, and they will not interfere with each other. The doping amounts of Er ³⁺ ions and Yb ³⁺ ions in the gain fiber are 10at% and 10at%, respectively. Among them, Er ³⁺ provides laser gain at 1550 nm wavelength, Yb ³⁺ provides laser gain at 1064 nm wavelength, and the length of Er/Yb nanoparticle co-doped fiber is 1 cm.

As the laser gain medium, the Er/Yb nanoparticle co-doped fiber is located in the resonant cavity. One end of the fiber is directly connected to the gate region of the Bragg grating group 3 by welding, and the other end is attached to the high-reflection mirror, which is used to simultaneously provide the intracavity 1 Laser gain in μm and 1.5 μm bands. The cavity length of the laser resonator is only 1.5 cm, which ensures a sufficiently large longitudinal mode interval in the cavity. At the same time, the Bragg grating group 3 is a dual-wavelength narrow-band grating, and the two center wavelengths are located at 1 μm and 1.5 μm respectively, which are used to realize the wavelength and mode Finally, the output of the four-wavelength single-frequency laser in the 1 μm and 1.5 μm bands is realized.

Example 5 The structure of the ultra-short cavity dual-wavelength single-frequency laser based on different rare earth nanoparticles doping provided in this example is shown in Figure 1, including a 976 nm pump source 1, a fiber wavelength division multiplexing, and a 976 nm pump source arranged in sequence along the optical path. device 2 , Bragg grating group 3 , Er/Yb nanoparticle co-doped gain fiber 4 and high reflection mirror 5 .

Among them, the pump source 1 is used to transmit the pump laser, the Bragg grating group 3 and the high reflection mirror form an ultra-short linear laser resonator, and a temperature control system is arranged outside the resonator to adjust and maintain the temperature of the laser resonator. The fiber wave The demultiplexer 2 connects the pump source 1 and the resonator, and injects the 976 nm pump laser emitted from the pump source into the resonator.

The pump source 1 described in this embodiment is a continuous pump source, and the center wavelength is 976 nm.

The optical fiber wavelength division multiplexer 2 described in this embodiment includes three ports, one of which is used as the output end of the dual-wavelength laser with a wavelength output range of 1000-1600 nm, and the other two ports are respectively connected with the pump source 1 and Bragg grating group 3.

The Bragg grating group 3 described in this embodiment is a low-reflectivity Bragg grating with a reflectivity of 50% to 99% and a grating region length of 0.5 mm. There are two reflection wavelengths in this grating region, which are 1064 nm and 1550 nm respectively. nm, where the short-wavelength grating region is located inside the resonator, and the long-wavelength grating region is located outside the resonator. The Bragg grating group 3 is a non-polarization-maintaining grating, so dual-wavelength laser output can be realized.

The gain fiber 4 provided in this embodiment is an Er/Yb nanoparticle co-doped fiber, and the optical fiber contains Y ₂ O ₃ nanoparticles 9 doped with two different rare earth ions, Er ³⁺ ions and Yb ³⁺ ions, and rare earth Er ^{3 +} 7 and rare earth Yb ³⁺ 8 are encapsulated in different Y ₂ O ₃ nanoparticles 9 respectively, and do not interfere with each other. The doping amounts of Er ³⁺ ions and Yb ³⁺ ions in the gain fiber are 10at% and 10at%, respectively. Among them, Er ³⁺ provides laser gain at 1550 nm wavelength, Yb ³⁺ provides laser gain at 1064 nm wavelength, and the length of gain fiber 4 is 1 cm.

As the laser gain medium, the Er/Yb nanoparticle co-doped fiber is located in the resonant cavity. One end of the fiber is directly connected to the gate region of the Bragg grating group 3 by welding, and the other end is attached to the high-reflection mirror, which is used to simultaneously provide the intracavity 1 Laser gain in μm and 1.5 μm bands. The cavity length of the laser resonator is only 1.5 cm, which ensures a sufficiently large longitudinal mode interval in the cavity. At the same time, the Bragg grating group 3 is a dual-wavelength narrow-band grating, and the two center wavelengths are located at 1 μm and 1.5 μm respectively, which are used to realize the wavelength and mode Finally, the output of 1 μm and 1.5 μm dual-wavelength single-frequency laser is realized.

The high-reflection mirror 5 in this embodiment is a saturable absorption mirror, coated with a broadband dielectric film, and the reflectivity is not less than 99.9%. Realize passive Q-switched dual-wavelength single-frequency laser output.

Claims (9)

1. An ultra-short cavity multi-wavelength single-frequency laser doped with different rare earth nanoparticles, including a pump source, a fiber wavelength division multiplexer, a Bragg grating group, a gain fiber, and a high-reflection mirror arranged in sequence along the optical path; the Bragg The grating group and the high-reflection mirror form an ultra-short linear laser resonator; the gain fiber is located in the resonator, one end of which is connected to the grid region of the Bragg grating group, and the other end is attached to the high-reflection mirror; it is characterized in that: the The gain fiber is a fiber doped with rare earth ions wrapped by two or more nanoparticles. 2. The ultrashort-cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping according to claim 1, wherein the rare earth ions are selected from Nd ³⁺ , Yb ³⁺ , Er ³⁺ , Tm ³⁺ , at least two of Ho ³⁺ , the doping amount is 5at%~20at%. 3 . The ultrashort-cavity multi-wavelength single-frequency laser based on doping of different rare earth nanoparticles according to claim 1 , wherein the length of the resonant cavity is 1.5 cm. 4 . 4 . The ultrashort-cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping according to claim 1 , wherein the pump source is a continuous pump source or a pulsed pump source. 5 . 5. The ultrashort-cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping according to claim 1, wherein the fiber wavelength division multiplexer comprises three ports, one of which is used as a dual-wavelength laser The output end of , the wavelength output range is greater than 1000 nm, and the other two ports are respectively connected to the pump source and the laser resonator. 6 . The ultra-short cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping according to claim 1 , wherein the Bragg grating group is a low-reflectivity Bragg grating with a reflectivity of 50% to 99%. 7 . . 7 . The ultrashort-cavity multi-wavelength single-frequency laser based on different rare-earth nanoparticles doping according to claim 6 , wherein the Bragg grating group has two reflection wavelengths in the same grating region, wherein the short-wavelength grating region has two reflection wavelengths. 8 . It is located inside the resonant cavity, and the long-wavelength grating region is located outside the resonant cavity. 8 . The ultrashort-cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping according to claim 6 , wherein the Bragg grating group is a polarization-maintaining grating or a non-polarization-maintaining grating. 9 . 9. The ultra-short cavity multi-wavelength single-frequency laser based on different rare earth nanoparticles doping according to any one of claims 1-8, wherein the high-reflection mirror is coated with a broadband dielectric film, and the reflectivity is not less than 99.9%.

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