A method for improving the output stability of material-based saturable absorber mode-locked fiber laser

Abstract

A method for improving the output stability of a material-based saturable absorber mode-locked fiber laser belongs to the field of laser technology. The material is applied to a mode-locked fiber laser as a saturable absorber. When the mode-locked pulse output by the laser is in an unstable state under a pump power of not less than 20 mW, an external light source is used to continuously irradiate the material saturable absorber device, and the mode-locked pulse output by the laser changes from an unstable state to a stable state. The method of the invention is simple, accurate and reliable.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a method for improving the output stability of a material-based saturable absorber mode-locked fiber laser. Background Art

[0002] In passively mode-locked fiber lasers, saturable absorbers play an important role in the generation and evolution of ultrafast laser pulses. When a beam of light passes through a saturable absorber, the transmittance of light with different intensities is different in the saturable absorption region, with high transmittance in the strong light part and low transmittance in the weak light part. Saturable absorbers are divided into material saturable absorbers and artificial saturable absorbers. Material saturable absorbers include: semiconductor saturable absorber mirrors and new two-dimensional materials; artificial saturable absorbers include: nonlinear multimode interference, nonlinear polarization evolution, nonlinear light ring mirrors, etc.

[0003] New two-dimensional materials have gradually become ideal saturable absorbers for passively mode-locked fiber lasers due to their wide spectral absorption characteristics, controllable photoelectric response, easy integration, and low cost. For example, graphene, as a mode-locking element, can generate pulses at a low-power pump threshold; molybdenum disulfide is applied to fiber lasers as a saturable absorber to obtain mode-locked pulse output. Various new two-dimensional material saturable absorbers have been successfully applied to ultrafast fiber lasers, but the stability of new two-dimensional materials as saturable absorbers is still the key to commercialization. Some people use electric field and other control methods to actively control the saturable absorption characteristics of new two-dimensional materials to maintain the long-term working stability of lasers, such as the output pulse stability achieved by actively controlling the characteristics of graphene saturated absorbers by electric field. This paper proposes a new method to improve the stability of material saturable absorber devices (saturable absorbers with light modulation performance), that is, by continuously irradiating the material saturable absorber device with an external light source (illumination light source and lasers of various frequencies), the output characteristics of the saturable absorber are controlled, so as to improve the stability of the output mode-locked pulse. Summary of the invention

[0004] A method for improving the output stability of a material-based saturable absorber mode-locked fiber laser, characterized in that the material is applied as a saturable absorber to a mode-locked fiber laser, and when the mode-locked pulse output by the laser is in an unstable state under a pump power of not less than 20 mW, an external light source is used to continuously irradiate the material saturable absorber device, and the mode-locked pulse output by the laser changes from an unstable state to a stable state. The material is a material that can be used as a saturable absorber in a laser to achieve mode locking.

[0005] The external light source includes an illumination light source and lasers of various frequencies.

[0006] Advantages and positive effects:

[0007] The material saturable absorption device is continuously irradiated with an external light source, and the output pulse is switched from an unstable state to a stable state, thereby improving the stability of the output pulse. The method of the invention is simple, accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 All-fiber 1T'-MoTe controlled by external laser irradiation 2 Schematic diagram of the structure of a light saturable absorption device

[0009] Figure 2 Based on 1T'-MoTe 2 Diagram of the experimental setup of passively mode-locked erbium-doped fiber laser with optical modulator and its measurement system.

[0010] Figure 3 Based on 1T'-MoTe 2 Output characteristics of soliton pulses generated by the passively mode-locked erbium-doped fiber laser of the optical modulator, (a) autocorrelation signal fitting pulse width is 530fs (b) output spectrum, central wavelength is 1563nm, 3dB bandwidth is 4.5nm (c) time-sequential pulse sequence (d) RF spectrum, inset: measurement range is 1GHz spectrum.

[0011] Figure 4 (a) Unstable pulse state in the spectrum when no external laser irradiation is applied (b) Unstable pulse state in the spectrum when external laser irradiation is applied (c) Non-steady-state pulse spectrum monitored by DFT when no external laser irradiation is applied (b) Steady-state pulse spectrum monitored by DFT when external laser irradiation is applied. DETAILED DESCRIPTION

[0012] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0013] Example 1

[0014] All-fiber 1T'-MoTe controlled by continuous irradiation of external laser (980nm laser) 2 The schematic diagram of the saturable absorption device is as follows: Figure 1 As shown, it is applied to the mode-locked erbium-doped fiber laser and tested, as shown in Figure 2 As shown, Figure 2 The front part is the experimental device diagram, and the back part is the measurement system. 2 The output characteristics of soliton pulses generated by passively mode-locked erbium-doped fiber lasers with optical modulators are shown in Figure 3As shown, a stable pulse output with a central wavelength of 1562.5nm and a pulse width of 530fs is obtained, and the signal-to-noise ratio is greater than 80dB. When the pump power is increased (greater than 20mW), the output pulse becomes unstable. The present invention uses time-stretched dispersion Fourier transform technology (DFT) to monitor the dynamic change process of the output mode-locked pulse. DFT technology, also known as real-time Fourier transform technology, uses large dispersion components to map the spectrum of ultrashort optical pulses into a stretched time domain waveform, so the waveform seen on the oscilloscope after passing through the DFT system is a spectral shape. The external laser (980nm laser) did not irradiate the 1T'-MoTe 2 When the saturable absorption device is used, the spectrum and spectral information obtained from the DFT system are as follows: Figure 4 4 (a), 4 (c). The external light source continuously irradiates 1T'-MoTe 2 When the saturable absorption device is used, the spectrum and spectral information obtained from the DFT system are as follows: Figure 4 4 (b) and 4 (d). By comparing the two, it can be found that the external laser (980nm laser) continuously irradiates 1T'-MoTe 2 The saturable absorber device can actively regulate the state of the laser output pulse, so that the output pulse state switches from an unstable state to a stable state. This shows that the external laser (980nm laser) continuous irradiation method can improve the output pulse stability of the material-based saturable absorber.

[0015] Example 2

[0016] The external light source (980nm laser) can be replaced with an illumination light source and lasers of various frequencies to 2 Continuous irradiation control of the saturable absorption device will also stabilize the pulse sequence it outputs.

[0017] Example 3

[0018] 1T'-MoTe 2 Replacing it with any two-dimensional material as a saturable absorber, applying it to the laser to achieve mode locking, and using an external light source to continuously irradiate and control it, will also stabilize the output laser pulse sequence.

Claims

1. A method for improving the output stability of a material-based saturable absorber mode-locked fiber laser, characterized in that: The material is applied as a saturable absorber in a mode-locked fiber laser. When the mode-locked pulse output by the laser is in an unstable state under a pump power of not less than 20mW, an external light source is used to continuously irradiate the saturable absorber device of the material, and the mode-locked pulse output by the laser changes from an unstable state to a stable state.

2. A method for improving the output stability of a material-based saturable absorber mode-locked fiber laser according to claim 1, characterized in that: The material is any two-dimensional material and can be used as a saturable absorber and applied to a laser to achieve mode locking.

3. A method for improving the output stability of a material-based saturable absorber mode-locked fiber laser according to claim 1, characterized in that: The external light source is lasers of various frequencies.

4. A method for improving the output stability of a material-based saturable absorber mode-locked fiber laser according to claim 3, characterized in that: The light source is an illumination light source.

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