High-power light source for assisting EYDFA to output 1.5 [mu] m wave band based on 1 [mu] m wave band signal light

Abstract

The invention relates to a high-power light source in the technical field of laser, in particular to a high-power light source for assisting an EYDFA to output a 1.5-micron wave band based on 1-micron wave band signal light, which absorbs untransferred pump light by introducing the signal light in the 1-micron wave band, further inhibits spontaneous radiation amplification of 1-micron wave band ytterbium ions, and improves the output efficiency of the 1-micron wave band ytterbium ions. The wavelength of the selected 1-micron-band signal light is located at the reabsorption wavelength of the EYDFA at the same time, the 1-micron-band signal light absorbing redundant pump light is reabsorbed by the EYDFA, energy is further transferred to erbium ions, and the conversion efficiency and output power of 1.5-micron-band laser are improved.

Description

Technical Field

[0001] The present invention relates to a high-power light source in the field of laser technology, and in particular to a high-power light source capable of outputting a 1.5 μm band through an Erbium-Ytterbium co-doped fiber amplifier (EYDFA) assisted by 1 μm signal light. Background Art

[0002] Lasers emitting at wavelengths between 1.53 and 1.62 μm, located in the 1.5 μm band and eye-safe within the atmospheric window, have significant application potential. Erbium-doped fibers exhibit radiation characteristics in this wavelength range, but their absorption cross-section is small and prone to concentration quenching when the erbium ion doping concentration is high. Increasing the core diameter of the doped fiber can enhance erbium ion absorption, but this results in low beam quality. Currently, the most effective approach is to increase pump light absorption by doping with ytterbium ions, subsequently transferring energy to the erbium ions, thereby achieving high beam quality and high power output in this wavelength range. However, when the pump rate exceeds the energy transfer rate, energy transfer between the ytterbium and erbium ions in erbium-ytterbium co-doped fibers reaches a bottleneck. When high pump power is injected, this bottleneck prevents some of the pump energy from being transferred, resulting in amplification of spontaneous emission from the ytterbium ions in the 1 μm band. This can lead to self-oscillation in the fiber and laser damage.

[0003] Several solutions have been proposed to address this issue. First, adjusting the concentration ratio of erbium and ytterbium ions in the fiber can effectively improve pump energy transfer efficiency. However, if the erbium ion concentration is too high, this approach can lead to pairing-induced concentration quenching, limiting output power. Second, off-peak pumping (i.e., shifting the pump wavelength to the maximum absorption point of the erbium-ytterbium co-doped fiber, for example, to 915 nm, 940 nm, or 1018 nm) can reduce pump absorption per unit length (while maintaining total absorption), thereby lowering the pump rate and alleviating the bottleneck effect and promoting energy transfer. However, even with high-power pumping, this approach still suffers from the amplification of spontaneous emission from ytterbium ions in the 1 μm band, limiting power increases. Third, in-band pumping at 1480 / 1535 nm can effectively suppress spontaneous emission from ytterbium ions in the 1 μm band. However, the high-power 1480 / 1535 nm in-band pumping required for this approach is relatively difficult to obtain.

[0004] In summary, the existing methods all have certain limitations in suppressing the spontaneous emission amplification of ytterbium ions in the 1 um band and improving the output power in the 1.5 um band. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention proposes a method for outputting a 1.5 μm high-power light source using an EYDFA (Emergency Dynamics Factorization) assisted by 1 μm signal light. This method introduces a 1 μm signal light to absorb the undiverted pump light, thereby suppressing the spontaneous emission amplification of ytterbium ions in the 1 μm band. It should be further noted that the 1 μm signal light wavelength selected by the present invention coincides with the reabsorption wavelength of the EYDFA. The 1 μm signal light that absorbs excess pump light will be reabsorbed by the EYDFA, further transferring energy to the erbium ions, thereby improving the conversion efficiency and output power of the 1.5 μm laser.

[0006] The technical solution adopted by the present invention is to use 1 μm-band signal light to assist EYDFA in outputting a 1.5 μm-band high-power light source, including a 1.5 μm-band pump laser, a 1 μm-band pump laser, a wavelength division multiplexer, a laser diode, a pump signal combiner, an erbium-ytterbium co-doped fiber, a cladding light filter, and an optical fiber output end cap. The laser diode, the pump signal combiner, and the erbium-ytterbium co-doped fiber constitute the EYDFA system, and the cladding light filter and the optical fiber output end cap constitute the laser output module. The 1.5 μm pump laser is used to provide 1.5 μm signal light. Its central wavelength is located in the erbium ion radiation region of the erbium-ytterbium co-doped fiber, covering a range of approximately 1.53-1.62 μm, i.e., the 1.5 μm band. The 1 μm pump laser is used to provide 1 μm signal light; its central wavelength is located in the ytterbium ion radiation region and reabsorption region of the Er / Yb co-doped fiber, covering a range of approximately 0.93-1.04 μm. The selection of the 1 μm signal light is crucial. It must be located in the ytterbium ion radiation region (0.93-1.14 μm) to ensure that the signal light can absorb excess pump light and suppress the amplification of 1 μm spontaneous emission. It must also be located in the reabsorption band of the Er / Yb co-doped fiber (0.90-1.04 μm) to ensure that the amplified 1 μm signal light can be reabsorbed by the Er / Yb co-doped fiber and further converted into 1.5 μm signal light. The wavelength division multiplexer is used to inject the signal light output by the 1.5 μm band pump laser and the 1 μm band pump laser into the signal input end of the pump signal combiner, thereby connecting to the EYDFA system; Laser diodes are used to provide pump light for Erbium-Ytterbium co-doped optical fibers; The pump signal combiner is used to transmit the pump light output by the laser diode and the signal light output by the wavelength division multiplexer into the erbium-ytterbium co-doped optical fiber; Erbium-ytterbium co-doped fiber is used to provide gain for 1.5 μm and 1 μm signal lights, and has a length of 1 to 50 m. The erbium-ytterbium co-doped fiber achieves population inversion by absorbing pump light transmitted by the pump-signal combiner, thereby providing gain for the 1.5 μm and 1 μm signal lights output by the pump-signal combiner. Selecting the length of the erbium-ytterbium co-doped fiber in the present invention is key to achieving high-power 1.5 μm laser output. When pump light is injected, the 1.5 μm and 1 μm signal lights compete for pump energy for gain amplification. If the erbium-ytterbium co-doped fiber is too short, the gain gained by the 1 μm signal light is greater than the reabsorption, resulting in some pump energy being extracted by the 1 μm signal light, reducing the efficiency of 1.5 μm signal light generation. When the fiber reaches a certain suitable length, the reabsorption of the 1 μm signal light band is greater than the gain. The signal light will be completely reabsorbed by the erbium-ytterbium co-doped fiber, and the energy will be further transferred to the 1.5 μm signal light band, thereby increasing the output power of the laser in this band. The laser output module is used for high-power laser output. It includes a cladding light filter to filter out light in the cladding, thereby improving the output beam quality, and a fiber output end cap to reduce the power density at the laser output interface, thereby reducing laser damage caused by excessive power density at the output fiber interface under high-power output conditions.

[0007] The 1 um band pump laser and the 1.5 um band pump laser can be continuous lasers or pulsed lasers.

[0008] The wavelength division multiplexer can be a filter-type wavelength division multiplexer or a wavelength division multiplexer manufactured by a fused taper method.

[0009] The output fiber pigtail of the laser diode can be 105 / 125 um, 135 / 155 um or 200 / 220 um multimode fiber.

[0010] The pump arm pigtail of the pump signal combiner uses an optical fiber that matches the output pigtail of the laser diode; the number of pump arms of the pump signal combiner can be 1, 2, 4, 6, 8, 16, or 32; the pumping mode can be forward pumping, backward pumping, or bidirectional pumping.

[0011] The present invention has the following technical effects: The present invention can achieve high-power output in the 1.5 μm band. The key to achieving high-power 1.5 μm laser output lies in two key points: first, the spontaneous emission amplification of ytterbium ions in the 1 μm band is effectively suppressed, and second, all pump energy is used to amplify the signal light power in the 1.5 μm band. The spontaneous emission amplification of ytterbium ions in the 1 μm band occurs due to the following reasons: when the pump rate exceeds the energy transfer rate from ytterbium ions to erbium ions, some pump light cannot be transferred, resulting in an accumulation of inverted populations between the upper and lower energy levels of the ytterbium ions. The ytterbium ions then spontaneously transition from a high energy level to a low energy level, thereby amplifying the spontaneous emission of ytterbium ions. As the pump power increases, although the 1.5 um band power of erbium ion radiation will increase, the spontaneous radiation amplification of ytterbium ions in the 1 um band will also be enhanced. When the pump power increases to a certain level, the spontaneous radiation amplification of ytterbium ions in the 1 um band will cause the fiber to self-oscillate and cause laser damage, thereby limiting the improvement of the 1.5 um band laser power. The present invention can effectively achieve high-power output in the 1.5 um band by introducing a 1 um band signal light that is located both in the EYDFA ytterbium ion radiation region and in the reabsorption region, and controlling the length of the erbium-ytterbium co-doped fiber. On the one hand, the 1 um band signal light located in the ytterbium ion radiation region will consume the pump light that cannot be transferred for the stimulated radiation amplification of its own signal light, thereby suppressing the spontaneous radiation amplification at the 1 um band, and promoting the further improvement of the 1.5 um band laser power. On the other hand, the 1 μm-band signal light wavelength selected in the present invention is located at the reabsorption wavelength of EYDFA. When the erbium-ytterbium co-doped fiber reaches a certain length, its 1 μm-band signal light gain is less than the reabsorption, resulting in the 1 μm-band signal light that absorbs excess pump light being reabsorbed by the erbium-ytterbium co-doped fiber, further transferring energy to erbium ions, improving the pump energy transfer efficiency (this means that ultimately all pump energy is transferred to erbium ions), thereby improving the conversion efficiency and output power in the 1.5 μm band. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of a 1.5 μm band high-power light source output based on 1 μm band signal light-assisted EYDFA of the present invention. In the figure: 11 is a 1.5 μm band pump laser, 12 is a 1 μm band pump laser, 2 is a wavelength division multiplexer, 3 is a laser diode, 4 is a pump signal combiner, 5 is an erbium-ytterbium co-doped fiber, 61 is a cladding light filter, and 62 is a fiber output end cap; Figure 2This is a schematic diagram of the structure of an EYDFA-assisted 1.55 μm high-power light source output based on 1 μm-band signal light according to an embodiment of the present invention. In the figure, 11 is the first pump laser, 12 is the second pump laser, 2 is the wavelength division multiplexer, 31 is the first laser diode, 32 is the second laser diode, 4 is the pump signal combiner, 5 is the erbium-ytterbium co-doped fiber, 61 is the cladding light filter, and 62 is the fiber output end cap. Figure 3 is the absorption radiation curve of Erbium-Ytterbium co-doped fiber; Figure 4 This is the energy level structure diagram of Erbium-Ytterbium co-doped optical fiber; Figure 5 These are the curves showing the changes in the power of two signal lights at different positions in the Er / Ytterbium co-doped gain fiber. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0014] Figure 1 Schematic diagram of the structure of the present invention based on the 1um band signal light to assist EYDFA output 1.5um band high power light source; Figure 1 As shown, based on the 1 μm band signal light, the EYDFA is assisted to output a 1.5 μm band high-power light source, including a 1.5 μm band pump laser 11, a 1 μm band pump laser 12, a wavelength division multiplexer 2, a laser diode 3, a pump signal combiner 4, an erbium-ytterbium co-doped fiber 5, a cladding light filter 61, and a fiber output end cap 62; wherein the laser diode 3, the pump signal combiner 4 and the erbium-ytterbium co-doped fiber 5 constitute the EYDFA system, and the cladding light filter 61 and the fiber output end cap 62 constitute the laser output module; An embodiment of the present invention is based on a 1.03 um signal light-assisted EYDFA output 1.55 um high-power light source, such as Figure 2As shown. It includes a first pump laser 11, a second pump laser 12, a wavelength division multiplexer 2, a first laser diode 31, a second laser diode 32, a pump signal combiner 4, an erbium-ytterbium co-doped fiber 5, a cladding light filter 61, and an optical fiber output end cap 62; the pigtails of the first pump laser 11 and the second pump laser 12 are connected to the input pigtail of the wavelength division multiplexer 2 by low-loss fusion splicing; the output pigtail of the wavelength division multiplexer 2 and the signal input pigtail of the pump signal combiner 4 are connected by low-loss fusion splicing. The output pigtails of the first laser diode 31 and the second laser diode 32 are connected to the pump input pigtail of the pump signal combiner 4 by low-loss fusion splicing; the output pigtail of the pump signal combiner 4 is connected to the input pigtail of the erbium-ytterbium co-doped optical fiber 5 by low-loss fusion splicing; the output pigtail of the erbium-ytterbium co-doped optical fiber 5 is connected to the laser output module 6 by low-loss fusion splicing; wherein the cladding light filter 61 and the optical fiber output end cap 62 together constitute the laser output module 6; In this embodiment, the central wavelength of the first pump laser 11 is 1.03 μm, and the output fiber pigtail is GDF 10 / 130; the central wavelength of the second pump laser 12 is 1.55 μm, and the output fiber pigtail is SM-GDF-1550; the input fiber and the output fiber of the wavelength division multiplexer 2 are both SM-GDF-1550, with an operating wavelength of 1.03 / 1.55 μm and an operating bandwidth of approximately 10 nm; in order to output high-power laser, two laser diodes are used as pump light sources, and the laser output wavelengths of the first laser diode 31 and the second laser diode 32 are both 976 nm, the output fiber pigtails are both 105 / 125 μm, and the output power is approximately 60 W; the pump arm input pigtail of the pump signal combiner 4 matches the output pigtails of the first laser diode 31 and the second laser diode 32, the signal input end pigtail of the pump signal combiner 4 matches the output pigtail of the wavelength division multiplexer 2, and the signal output end pigtail of the pump signal combiner 4 matches the input pigtail of the erbium-ytterbium co-doped fiber 5; the core / cladding size of the erbium-ytterbium co-doped fiber 5 is 25 / 300um, the numerical aperture is 0.09, the cladding absorption coefficient at a wavelength of 976 nm is approximately 7 dB / m, and the fiber length is 5 m. Figure 3 The absorption-radiation curve of the Er-Yb co-doped fiber 5 shows that 1.03 μm falls within the reabsorption wavelength of Er-Yb co-doped fiber 5. Because 1.03 μm falls within the reabsorption wavelength of Er-Yb co-doped fiber 5, the Er-Yb co-doped fiber 5 used here is sufficiently long (approximately 35 dB absorption) to ensure complete absorption of the 1.03 μm signal light, thereby improving the conversion efficiency and output power of the output 1.55 μm signal light.

[0015] In this embodiment, the principle of 1.55 um laser amplification is as follows: a first pump laser 11 with a central wavelength of 1.03 um and a second pump laser 12 with a central wavelength of 1.55 um are injected into the EYDFA through the wavelength division multiplexer 2. In the EYDFA, the erbium-ytterbium co-doped fiber 5 (its energy level structure is shown in FIG. Figure 4 The ytterbium ions in the laser diode 31 and the second laser diode 32 absorb the pump light and are converted from the ground state to the ground state. 2 F [7 / 2] Transition to the excited state 2 F [5 / 2], the excited ytterbium ions transfer the absorbed pump light energy to the erbium ions through sensitization. In this process, the erbium ions gain energy and change from the ground state to 4 I [15 / 2] Transition to a high energy state 4 I [11 / 2]. In the high energy state, the lifetime of erbium ions is only 1ns, after which they rapidly undergo a non-radiative transition to a metastable state. 4 I [13 / 2], the lifetime of erbium ions in the metastable energy state is relatively long, about 10 ms, so it can be 4 I [15 / 2] and energy levels 4 I [13 / 2], the accumulation forms a sufficient number of particle inversions. When the 1.55 um signal light passes through, in the metastable state 4 I [13 / 2] Erbium ions generate stimulated radiation to amplify the power of 1.55 um signal light, and then reduce it to 4 I [15 / 2] energy level, ultimately achieving power amplification of 1.55 um laser.

[0016] In this embodiment, the reasons for the effective suppression of ytterbium ion spontaneous emission amplification and the high power output at 1.55 μm are as follows: when the pump rate is higher than the energy transfer rate from ytterbium ions to erbium ions, some pump light cannot be transferred, resulting in a population accumulation of inversions between the upper and lower energy levels of the ytterbium ions. When the 1.03 μm signal light transmitted by the first pump laser 11 passes through, this energy is absorbed by the 1.03 μm signal light and used for stimulated emission amplification, thereby suppressing the spontaneous emission amplification caused by the ytterbium ions' spontaneous transition from a high energy level to a low energy level. In addition, although the 1.03 μm light gains energy and achieves power amplification, its wavelength is at the reabsorption wavelength of the erbium-ytterbium co-doped fiber. Therefore, the 1.03 μm light will be reabsorbed and retransferred to the 1.55 μm light, thereby increasing the output power of the 1.55 μm light. Figure 5The power curves of the two signal beams at different locations on the erbium-ytterbium co-doped fiber are shown. As the two signal beams propagate along the fiber, the power of the 1.03 μm signal beam first increases and then decreases. At the output end of the 5 m erbium-ytterbium co-doped fiber, the 1.03 μm signal beam has almost no power output, while the 1.55 μm signal beam has a power of approximately 59 W.

Claims

1. Based on 1µm band signal light, the EYDFA is assisted to output a 1.5µm band high-power light source, characterized by: It includes a 1.5 μm pump laser, a 1 μm pump laser, a wavelength division multiplexer, a laser diode, a pump signal combiner, an erbium-ytterbium co-doped fiber, a cladding light filter, and an optical fiber output end cap. The laser diode, the pump signal combiner, and the erbium-ytterbium co-doped fiber form the EYDFA system, while the cladding light filter and the optical fiber output end cap form the laser output module. The 1.5 μm pump laser is used to provide 1.5 μm signal light. Its central wavelength is located in the erbium ion radiation region of the erbium-ytterbium co-doped fiber, covering the range of 1.53-1.62 μm, i.e., the 1.5 μm band. The 1 μm-band pump laser is used to provide 1 μm-band signal light; its central wavelength is located in the ytterbium ion radiation region and reabsorption region of the erbium-ytterbium co-doped fiber, covering a range of 0.93-1.04 μm; The wavelength division multiplexer is used to inject the signal light output by the 1.5 μm band pump laser and the 1 μm band pump laser into the signal input end of the pump signal combiner, thereby connecting to the EYDFA system; Laser diodes are used to provide pump light for Erbium-Ytterbium co-doped optical fibers; The pump signal combiner is used to transmit the pump light output by the laser diode and the signal light output by the wavelength division multiplexer into the erbium-ytterbium co-doped optical fiber; Erbium-ytterbium co-doped fiber is used to provide gain for 1.5 μm band signal light and 1 μm band signal light, with a length of 1 m to 50 m. Laser output module is used for high power laser output.

2. The method according to claim 1, wherein: The 1 um band pump laser and the 1.5 um band pump laser are continuous lasers or pulsed lasers.

3. The method according to claim 1, wherein the 1 μm band signal light is used to assist the EYDFA in outputting a 1.5 μm band high-power light source, characterized in that: The wavelength division multiplexer is a filter-type wavelength division multiplexer or a wavelength division multiplexer prepared by a fused taper method.

4. The method according to claim 1, wherein: The output pigtail of the laser diode is a multimode optical fiber with a size of 105 / 125 um, 135 / 155 um or 200 / 220 um.

5. The method according to claim 1, wherein: The pump arm pigtail of the pump signal combiner uses an optical fiber that matches the output pigtail of the laser diode; the number of pump arms of the pump signal combiner is 1, 2, 4, 6, 8, 16, and 32; the pumping mode adopts forward pumping, backward pumping, or bidirectional pumping.

6. The method according to claim 1, wherein: The laser output module includes a cladding light filter: used to filter out the light in the cladding to improve the output beam quality; and a fiber output end cap: used to reduce the power density of the laser output interface to reduce laser damage caused by excessive power density at the output fiber interface under high power output conditions.

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