CN105390913B - Auxiliary chamber pumps erbium-ytterbium co-doped fiber amplifier - Google Patents

Abstract

The invention discloses an auxiliary cavity pumped erbium-ytterbium co-doped optical fiber amplifier, which comprises a signal input terminal (1), an isolator (2), a pumping source (3), a pumping/signal combiner (4), a front Retroreflective fiber grating (5), erbium-ytterbium co-doped fiber (6), retroreflective fiber grating (7), output port (8); wherein: the laser output from the pump source (3) is sequentially combined by the pump signal Beamer (4), forward reflection fiber grating (5), are sent into the erbium-ytterbium co-doped fiber (6), and the laser is pumped; the laser signal to be amplified is input from the input terminal (1), and passes through The signal end of the isolator (2), the pump signal beam combiner (4), the forward reflection fiber grating (5), enters the erbium-ytterbium co-doped fiber (6), and after the laser signal is amplified, it passes through the output port ( 8) Output. The invention can effectively suppress Yb-ASE and improve the stability and pump conversion efficiency of the erbium-ytterbium co-doped optical fiber amplifier.

Description

Auxiliary Cavity Pumped Erbium-Ytterbium Co-doped Fiber Amplifier

technical field

The invention relates to the field of fiber lasers, in particular to an erbium-ytterbium co-doped fiber amplifier with an auxiliary resonant cavity.

Background technique

Erbium-ytterbium co-doped fiber amplifiers operate at a wavelength of 1.5 microns, which has the advantage of being "eye-safe", and has important applications in laser processing, laser ranging and other fields. Compared with the ordinary erbium-doped fiber amplifier, the gain fiber of this amplifier is doped with two rare earth ions of erbium (Er) and ytterbium (Yb) at the same time. The doping of ytterbium ions can effectively reduce the concentration quenching effect of erbium ions, increase its doping concentration, and expand the selection range of pump wavelengths, so the erbium-ytterbium co-doped fiber amplifier can obtain higher output power. However, after the doping of ytterbium ions, the pump photons will be absorbed by the ytterbium ions first, pumping them from the ground state to the upper energy level, and then the ytterbium ions in the excited state will transfer energy to the surrounding erbium ions through cross relaxation, pump it from the ground state to the upper energy level. Finally, the signal in the 1.5 micron band is amplified by the stimulated emission transition between the upper energy level of the erbium ion and the ground state. This is an indirect pumping method. Since the rate of energy transfer from ytterbium ions to erbium ions through cross relaxation is limited, when the pumping rate is greater than the energy transfer rate between the two, the energy transfer will have a bottleneck effect, resulting in the upper energy level of ytterbium ions in the gain medium The number density increases. Since the energy cannot be transferred to the surrounding erbium ions immediately, these excited ytterbium ions will produce spontaneous emission (Yb-ASE) in the ytterbium ion radiation band (1 micron band) when they transition to the ground state. On the one hand, energy will be wasted and the pump conversion efficiency of the amplifier will be reduced. On the other hand, as the pump continues to increase, self-oscillation or self-pulsation effects will eventually occur, resulting in unstable output power of the amplifier, and even permanent damage to the device. Eliminating Yb-ASE and its resulting self-oscillation and self-pulsation under high-power pumping is the key to improving the performance of Er-Yb co-doped fiber amplifiers.

Contents of the invention

In order to overcome the influence of Yb-ASE and the self-excited oscillation and self-pulsation caused by high-power pumping on the stability and efficiency of the erbium-ytterbium co-doped fiber amplifier, the present invention proposes an auxiliary cavity pumped erbium-ytterbium co-doped fiber Amplifier, introduce a high-reflectivity fiber grating pair with a suitable wavelength in the 1 micron band into the traditional erbium-ytterbium co-doped fiber amplifier to form a resonant cavity with auxiliary pumping effect, and improve stability through the auxiliary pumping effect of the resonant cavity High power erbium ytterbium co-doped fiber amplifier with pump conversion efficiency.

The present invention proposes an auxiliary cavity pumped erbium-ytterbium co-doped fiber amplifier, comprising a signal input terminal 1, an isolator 2, a pump source 3, a pump signal combiner 4, a forward reflection fiber grating 5, an erbium-ytterbium co-doped Doped fiber 6, retroreflective fiber grating 7, output end 8; wherein:

The laser light output by the pump source 3 is sent into the erbium-ytterbium co-doped fiber 6 through the pump signal beam combiner 4 and the forward reflection fiber grating 5 in order to pump the amplifier; the laser signal to be amplified is input The input from terminal 1 passes through the isolator 2, the signal terminal of the pump signal combiner 4, the forward reflection fiber grating 5, and enters the erbium-ytterbium co-doped fiber 6 in sequence. After the laser signal is amplified, it is output through the output terminal 8.

The reflection wavelengths of the forward-reflecting fiber grating and the backward-reflecting fiber grating are consistent and both are located in the emission band of ytterbium ions, that is, the 1 micron band; the two form an auxiliary cavity, which acts as an auxiliary pump for the amplifier.

The pigtails constituting the output end 8 are polished at an angle; the angle is typically 8 degrees.

The forward-reflecting fiber grating 5 and the backward-reflecting fiber grating 7 are a high-reflectivity fiber grating pair with a suitable wavelength in the 1 micron band, and a resonant cavity with an auxiliary pumping effect is formed by the two, effectively shortening the required gain Fiber length.

Compared with the prior art, the invention can effectively suppress Yb-ASE and improve the stability and pump conversion efficiency of the erbium-ytterbium co-doped fiber amplifier.

Description of drawings

Figure 1 is a schematic diagram of an auxiliary cavity-pumped erbium-ytterbium co-doped fiber amplifier;

Figure 2 is a schematic diagram of the power evolution results of pumping, signal, forward fiber grating reflection, and backward fiber grating reflection in the gain fiber after the auxiliary cavity is introduced;

Fig. 3 is the grating wavelength change curve diagram of the corresponding optical fiber of the maximum output signal power and optimum fiber length when adopting the fiber grating of different wavelengths, wherein: a, the change curve of the signal power after amplification with the fiber grating wavelength; b, the best Variation curve of fiber length with fiber grating wavelength;

Reference signs: 1. input terminal, 2. isolator, 3. pump source, 4. pump signal beam combiner, 5. forward reflection fiber grating, 6. erbium-ytterbium co-doped fiber, 7. backward reflection Fiber Bragg grating, 8, output end.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram of the principle of auxiliary cavity pumped erbium-ytterbium co-doped fiber amplifier. The laser signal to be amplified has a wavelength of 1550nm and a power of 100mW. The signal is input from the input terminal 1, and enters the erbium-ytterbium co-doped fiber 6 through the isolator 2, the pump signal combiner 4, and the forward reflection fiber Bragg grating 5 in sequence, and after being amplified, it passes through the back reflection fiber Bragg grating 7, and then passes through the output terminal 8 output.

In order to prevent the adverse effects of end face reflections, the 8 pigtails at the output end are polished to a certain angle (usually 8 degrees). In this example, the central wavelength of the pump source is 976nm, and the power is 10W. The optimal gain fiber length obtained through optimization is 3.25m. The working principle is that the forward reflection fiber grating and the backward reflection fiber grating with the same wavelength form a resonant cavity. Under high-power pumping, laser oscillations of corresponding wavelengths will be generated in the resonator, which can well suppress the generation of Yb-ASE. The laser in the resonant cavity will be reabsorbed by the gain fiber during the resonance process, which can increase the power of the output signal under the same pump power, that is, improve the pump conversion efficiency.

As shown in Figure 2, when the wavelength of the forward and backward reflection FBG is 1028nm, and the peak reflectivity is 99.9%, the power evolution curve of the pump light, signal light, and forward/backward reflection FBG reflection light in the gain fiber . It can be seen that laser resonance is formed after introducing a pair of high reflectivity fiber gratings.

As shown in FIG. 3 , it is the corresponding relationship between the maximum output signal power and the optimal fiber length when fiber gratings with different wavelengths are used for synchronization. (a) is the variation curve of the signal power with the wavelength of the FBG; (b) is the variation curve of the optimal fiber length with the wavelength of the FBG. As a comparison, in the case of the same pump and signal parameters, the output power of the common Erbium-Ytterbium co-doped amplifier is 3.64W, and the corresponding optimal fiber length is 3.15m, as shown in Figures (a) and (b) respectively. line shown. It can be seen from Figure 3 that (1) if the reflection wavelength of the FBG is selected between 1010nm and 1066nm, the power of the amplified output signal can be improved to varying degrees; (2) the shorter the wavelength of the FBG, the better The fiber length is also shorter, even shorter than the optimal fiber length for common erbium-ytterbium co-doped fiber amplifiers.

When the fiber grating wavelength is 1028nm, the amplified signal power reaches 4.69W, which is 28.8% higher than that without an auxiliary cavity, and the optimal fiber length is 3.25m, which is almost the same as that without an auxiliary cavity.

In summary, it can be seen that the introduction of an auxiliary cavity with a suitable wavelength can significantly improve the pump conversion efficiency of the amplifier, and the laser oscillation in the auxiliary cavity can also effectively suppress the spontaneous emission and random oscillation in ordinary erbium-ytterbium co-doped fiber amplifiers. improve its stability.

Claims (3)

1. a kind of auxiliary chamber pumps erbium-ytterbium co-doped fiber amplifier, which is characterized in that the amplifier include signal input part (1), Isolator (2), pumping source (3), pump signal bundling device (4), forward reflection fiber grating (5), erbium and ytterbium codoping gain fibre (6), retroreflection optical fiber grating (7), output end (8)；Wherein：

The laser of a pair of of pumping source (3) output is sent sequentially via pump signal bundling device (4), forward reflection fiber grating (5) Enter erbium-ytterbium co-doped fiber (6), pumping is carried out to the amplifier；Laser signal to be amplified is inputted by input terminal (1), is passed through successively Cross isolator (2), the signal end of pump signal bundling device (4), forward reflection fiber grating (5), into erbium-ytterbium co-doped fiber (6), the laser signal is amplified, is exported via output end (8).

2. a kind of auxiliary chamber as described in claim 1 pumps erbium-ytterbium co-doped fiber amplifier, which is characterized in that forward reflection optical fiber Grating is consistent with the reflection wavelength of retroreflection optical fiber grating and is respectively positioned on the emission band of ytterbium ion, i.e. 1 micron waveband；The two Auxiliary chamber is constituted, auxiliary pumping action is played to amplifier.

3. a kind of auxiliary chamber as described in claim 1 pumps erbium-ytterbium co-doped fiber amplifier, which is characterized in that the forward reflection The high reflectance fiber grating of fiber grating (5) and the retroreflection optical fiber grating (7) as 1 micron waveband suitable wavelength It is right, a resonant cavity for having auxiliary pumping effect is formed by the two, effectively shortens required gain fibre length.