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RSS2020 Vol. 32, No. 12
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2020,
32: 1-2.
2020,
32: 1-1.
2020,
32: 121001.
doi: 10.11884/HPLPB202032.200186
Abstract:
In this paper, the research progress of single-frequency fiber oscillators are introduced in the terms of wavelength expansion, the development of single frequency fiber amplifiers are introduced in the terms of power scaling. Besides, the research achievements of 1 μm-band high-power narrow-linewidth fiber laser are summarized based on the techniques of generating narrow-linewidth seed sources. Then the development trend and main challenges of high-power single-frequency and narrow-linewidth fiber laser are analyzed. The key technologies of high-power narrow-linewidth fiber laser are summarized and discussed. Finally, applications in various fields based on the current development status of high-power narrow-linewidth fiber laser are introduced.
In this paper, the research progress of single-frequency fiber oscillators are introduced in the terms of wavelength expansion, the development of single frequency fiber amplifiers are introduced in the terms of power scaling. Besides, the research achievements of 1 μm-band high-power narrow-linewidth fiber laser are summarized based on the techniques of generating narrow-linewidth seed sources. Then the development trend and main challenges of high-power single-frequency and narrow-linewidth fiber laser are analyzed. The key technologies of high-power narrow-linewidth fiber laser are summarized and discussed. Finally, applications in various fields based on the current development status of high-power narrow-linewidth fiber laser are introduced.
2020,
32: 121002.
doi: 10.11884/HPLPB202032.200240
Abstract:
The output power of single fiber is limited by the thermal effects, laser damage threshold, and nonlinear optical effects. Beam combining technology has been proposed to break through the limit of single fiber and achieve higher output power fiber laser. Spectral beam combining technology has the advantages of good beam quality and simple structure, which stands out among many beam combining technologies. We review several typical kinds of spectral beam combining technologies of fiber lasers, including their principles, current status, advantages and disadvantages. The recent progress of thermal distortion of the grating was introduced and discussed from the aspects of theoretical and experimental research, and the development trend of spectral beam combining technology are prospected.
The output power of single fiber is limited by the thermal effects, laser damage threshold, and nonlinear optical effects. Beam combining technology has been proposed to break through the limit of single fiber and achieve higher output power fiber laser. Spectral beam combining technology has the advantages of good beam quality and simple structure, which stands out among many beam combining technologies. We review several typical kinds of spectral beam combining technologies of fiber lasers, including their principles, current status, advantages and disadvantages. The recent progress of thermal distortion of the grating was introduced and discussed from the aspects of theoretical and experimental research, and the development trend of spectral beam combining technology are prospected.
2020,
32: 121003.
doi: 10.11884/HPLPB202032.200180
Abstract:
The report about mode instability in 2010 has begun the history of struggling with the waste heat in fiber lasers. This paper presents a 10-year research progress of mode instability research, including physical demonstrations, physical mechanism, theoretical investigation, various impact factors and effective mitigating strategies. The most recent results on mode instability suppressing are also included as well as the future development trend of mode instability research.
The report about mode instability in 2010 has begun the history of struggling with the waste heat in fiber lasers. This paper presents a 10-year research progress of mode instability research, including physical demonstrations, physical mechanism, theoretical investigation, various impact factors and effective mitigating strategies. The most recent results on mode instability suppressing are also included as well as the future development trend of mode instability research.
2020,
32: 121004.
doi: 10.11884/HPLPB202032.200144
Abstract:
In recent years, fiber laser has been developing rapidly, and gradually applied in many fields. Further improvement of output power is still the research hotspot of fiber laser. Beam combining is an important method to scale output power of fiber laser. Beam combining requires that the sub beam is a narrow linewidth fiber laser, so the research of narrow linewidth fiber laser is of great significance for power improvement. In this paper, the development and research status of narrow linewidth high power fiber lasers are introduced in detail, and based on the current research status, the future development trend is prospected.
In recent years, fiber laser has been developing rapidly, and gradually applied in many fields. Further improvement of output power is still the research hotspot of fiber laser. Beam combining is an important method to scale output power of fiber laser. Beam combining requires that the sub beam is a narrow linewidth fiber laser, so the research of narrow linewidth fiber laser is of great significance for power improvement. In this paper, the development and research status of narrow linewidth high power fiber lasers are introduced in detail, and based on the current research status, the future development trend is prospected.
2020,
32: 121005.
doi: 10.11884/HPLPB202032.200210
Abstract:
Narrowband dissipative soliton mode-locked fiber lasers can produce transform-limited picosecond pulses. Unfortunately, due to the limitation of allowable nonlinear phase shift for the intracavity pulse, the repetition rate of the pulses generated by such lasers cannot be reduced by increasing the cavity length; the pulse energy is only below 0.1 nJ. These seriously restrict the practical application of such picosecond pulsed fiber lasers. In this paper, we propose a method that allows the cavity length to be increased to reduce the repetition rate of the narrowband dissipative soliton picosecond fiber laser pulses by extracting the pulse energy out of the cavity with a coupler to suppress the accumulation of nonlinear phase shift of the intracavity pulses. Using this method, the laser repetition rate was successfully reduced from 35.2 MHz to 1.77 MHz, and the pulse time-frequency characteristics remained unchanged. We also propose a method to suppress spectral broadening in picosecond pulse fiber amplification based on inter-stage FBG notch filtering. By simply using the inter-stage notch filter, the output pulse spectrum width after the first-stage fiber amplifier can be narrowed, allowing the second-stage fiber amplifier to further increase the pulse energy, and also, the pulse can be reshaped to be nearly Gaussian-shaped, allowing the second-stage fiber amplifier to increase the pulse energy higher by using the Gaussian pulse characteristics of the smaller spectral broadening slope. Using this method, on the premise of keeping the RMS spectral width within 0.4 nm, after a 10 ps pulse passes through a standard single-mode fiber amplifier, the pulse energy can be increased from 0.2 nJ to more than 10 nJ.
Narrowband dissipative soliton mode-locked fiber lasers can produce transform-limited picosecond pulses. Unfortunately, due to the limitation of allowable nonlinear phase shift for the intracavity pulse, the repetition rate of the pulses generated by such lasers cannot be reduced by increasing the cavity length; the pulse energy is only below 0.1 nJ. These seriously restrict the practical application of such picosecond pulsed fiber lasers. In this paper, we propose a method that allows the cavity length to be increased to reduce the repetition rate of the narrowband dissipative soliton picosecond fiber laser pulses by extracting the pulse energy out of the cavity with a coupler to suppress the accumulation of nonlinear phase shift of the intracavity pulses. Using this method, the laser repetition rate was successfully reduced from 35.2 MHz to 1.77 MHz, and the pulse time-frequency characteristics remained unchanged. We also propose a method to suppress spectral broadening in picosecond pulse fiber amplification based on inter-stage FBG notch filtering. By simply using the inter-stage notch filter, the output pulse spectrum width after the first-stage fiber amplifier can be narrowed, allowing the second-stage fiber amplifier to further increase the pulse energy, and also, the pulse can be reshaped to be nearly Gaussian-shaped, allowing the second-stage fiber amplifier to increase the pulse energy higher by using the Gaussian pulse characteristics of the smaller spectral broadening slope. Using this method, on the premise of keeping the RMS spectral width within 0.4 nm, after a 10 ps pulse passes through a standard single-mode fiber amplifier, the pulse energy can be increased from 0.2 nJ to more than 10 nJ.
2020,
32: 121006.
doi: 10.11884/HPLPB202032.200192
Abstract:
The feasibility of realizing high efficiency spectral beam combining with multilayer dielectric (MLD) gratings based on conical diffraction was analyzed. The spectral beam combining approach was designed with the incident polar angle nearly equals to the Littrow angle based on the conical diffraction theory and two unit beams were experimentally combined. The experimental results indicate that, the diffraction efficiency nearly did not change in the case of conical diffraction when θ was constant and\begin{document}$ \varphi $\end{document} ![]()
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The feasibility of realizing high efficiency spectral beam combining with multilayer dielectric (MLD) gratings based on conical diffraction was analyzed. The spectral beam combining approach was designed with the incident polar angle nearly equals to the Littrow angle based on the conical diffraction theory and two unit beams were experimentally combined. The experimental results indicate that, the diffraction efficiency nearly did not change in the case of conical diffraction when θ was constant and
2020,
32: 121007.
doi: 10.11884/HPLPB202032.200203
Abstract:
There are many kinds of nonlinear effects in the interaction between high power laser and matter. The beam of laser fusion driver is highly coherent, which greatly enhances the nonlinear effects, and inevitably limits the laser power and efficient utilization. Looking back on the development history of laser fusion driver, there is a dark line runing through the main line of improving laser output capability, which is struggling with beam coherence. The control status of beam coherence in laser fusion driver is reviewed from two aspects: restraining the nonlinear transmission effect of high power laser and suppressing the interaction between laser and plasma. In view of the potential demand, innovative technologies for the future development of high power lasers are proposed.
There are many kinds of nonlinear effects in the interaction between high power laser and matter. The beam of laser fusion driver is highly coherent, which greatly enhances the nonlinear effects, and inevitably limits the laser power and efficient utilization. Looking back on the development history of laser fusion driver, there is a dark line runing through the main line of improving laser output capability, which is struggling with beam coherence. The control status of beam coherence in laser fusion driver is reviewed from two aspects: restraining the nonlinear transmission effect of high power laser and suppressing the interaction between laser and plasma. In view of the potential demand, innovative technologies for the future development of high power lasers are proposed.
2020,
32: 121008.
doi: 10.11884/HPLPB202032.200191
Abstract:
This paper discusses the technique of the spectral beam combing (SBC) in the solid-state lasers, including the fiber laser, the Yb:YAG slab laser, and the diode laser. For the fiber lasers, we study the beam quality degeneration (BQD) in SBC due to the dispersion of three kinds of diffraction optics elements (DOE): single multi-layer dielectric (MLD) grating, a couple of MLD gratings and multiple volume Bragg gratings (VBG). We point out that, for all cases, BQD is determined by the full-width of the second-order moments instead of the full-width of half maximum in the spectrum of sub-beams. But the value of BQD depends on the DOEs. For solid-state crystal lasers, we demonstrate the feasibility of SBC in the Yb:YAG slab laser by designing an experiment for an intra-cavity SBC employing an MLD grating. The experiment results SBC of seven sub-beams and 241 W laser output, the beam quality after SBC is β≈4.1. It indicates that the output power of the Yb:YAG slab laser can be further scaled by SBC. Finally, we demonstrate a new technique to scale the output power of the laser diodes (LD), which includes the large modal external oscillation in the slow-axis and the SBC in the fast-axis simultaneously. The experiment results the SBC of nine LDs with the slow-axis width of 1 mm, the beam qualities after SBC are β≈6.3 in the slow-axis and β≈1.6 in the fast-axis. It means that beam quality after the SBC in the fast-axis is controllable.
This paper discusses the technique of the spectral beam combing (SBC) in the solid-state lasers, including the fiber laser, the Yb:YAG slab laser, and the diode laser. For the fiber lasers, we study the beam quality degeneration (BQD) in SBC due to the dispersion of three kinds of diffraction optics elements (DOE): single multi-layer dielectric (MLD) grating, a couple of MLD gratings and multiple volume Bragg gratings (VBG). We point out that, for all cases, BQD is determined by the full-width of the second-order moments instead of the full-width of half maximum in the spectrum of sub-beams. But the value of BQD depends on the DOEs. For solid-state crystal lasers, we demonstrate the feasibility of SBC in the Yb:YAG slab laser by designing an experiment for an intra-cavity SBC employing an MLD grating. The experiment results SBC of seven sub-beams and 241 W laser output, the beam quality after SBC is β≈4.1. It indicates that the output power of the Yb:YAG slab laser can be further scaled by SBC. Finally, we demonstrate a new technique to scale the output power of the laser diodes (LD), which includes the large modal external oscillation in the slow-axis and the SBC in the fast-axis simultaneously. The experiment results the SBC of nine LDs with the slow-axis width of 1 mm, the beam qualities after SBC are β≈6.3 in the slow-axis and β≈1.6 in the fast-axis. It means that beam quality after the SBC in the fast-axis is controllable.
2020,
32: 121009.
doi: 10.11884/HPLPB202032.200185
Abstract:
This paper presents the research progress of high efficiency and compact all-solid-state lasers based on Yb:YAG slab at room temperature. The laser dynamics model of Yb slab at room temperature is established. It is quantitatively analysed that the pumped laser intensity and the injected laser brightness influence the optical conversion efficiency. The method to suppress the slab-edge-effect is founded. The output power of 22.3 kW, the optical conversion efficiency of 36%, and the beam quality of 2.4 times diffraction limit, were achieved in experiment. These results lay a foundation for the key technology research of higher power laser and development of the miniaturized, lightweight and practical high power Yb slab laser.
This paper presents the research progress of high efficiency and compact all-solid-state lasers based on Yb:YAG slab at room temperature. The laser dynamics model of Yb slab at room temperature is established. It is quantitatively analysed that the pumped laser intensity and the injected laser brightness influence the optical conversion efficiency. The method to suppress the slab-edge-effect is founded. The output power of 22.3 kW, the optical conversion efficiency of 36%, and the beam quality of 2.4 times diffraction limit, were achieved in experiment. These results lay a foundation for the key technology research of higher power laser and development of the miniaturized, lightweight and practical high power Yb slab laser.
2020,
32: 121010.
doi: 10.11884/HPLPB202032.200236
Abstract:
High power semiconductor lasers are the main pump source for solid-state lasers and fiber lasers. The improvement in the performance of laser pump sources directly promotes the development of solid-state lasers, fiber lasers and other lasers. The article introduces the latest research progress of 8xx nm and 9xx nm semiconductor laser pump sources. The output power research level of 8xx nm single-emitter laser has reached 18.8 W@95 µm, the output power research level of 8xx nm laser bar has reached 1.8 kW(QCW), the output power research level of 9xx nm single-emitter laser has reached 35 W@100 µm, the output power research level of 9xx nm laser bar has reached 1.98 kW(QCW). The output power of a narrow linewidth semiconductor laser with a linewidth ＜1 nm can reach 14 W. The development trend of semiconductor laser pump source in the future is forecasted.
High power semiconductor lasers are the main pump source for solid-state lasers and fiber lasers. The improvement in the performance of laser pump sources directly promotes the development of solid-state lasers, fiber lasers and other lasers. The article introduces the latest research progress of 8xx nm and 9xx nm semiconductor laser pump sources. The output power research level of 8xx nm single-emitter laser has reached 18.8 W@95 µm, the output power research level of 8xx nm laser bar has reached 1.8 kW(QCW), the output power research level of 9xx nm single-emitter laser has reached 35 W@100 µm, the output power research level of 9xx nm laser bar has reached 1.98 kW(QCW). The output power of a narrow linewidth semiconductor laser with a linewidth ＜1 nm can reach 14 W. The development trend of semiconductor laser pump source in the future is forecasted.
2020,
32: 121011.
doi: 10.11884/HPLPB202032.200209
Abstract:
This paper summarizes the research work of North China Research Institute of Electro-Optics (NCRIEO) in the field of solid-state laser technology since 1964. In the first 30 years, NCRIEO had helped “two bombs and one satellite” and laid the foundation stone for independent and controllable development of laser gain crystals. Since then, the research on laser materials has gradually focused on industrial development, with extensive involvement in the subdivision of laser devices and breakthroughs in laser applications. This paper introduces NCRIEO’s completed key projects, important technological breakthroughs, developed professional directions and current industry status, discusses the development direction of laser technology at NCRIEO in the future.
This paper summarizes the research work of North China Research Institute of Electro-Optics (NCRIEO) in the field of solid-state laser technology since 1964. In the first 30 years, NCRIEO had helped “two bombs and one satellite” and laid the foundation stone for independent and controllable development of laser gain crystals. Since then, the research on laser materials has gradually focused on industrial development, with extensive involvement in the subdivision of laser devices and breakthroughs in laser applications. This paper introduces NCRIEO’s completed key projects, important technological breakthroughs, developed professional directions and current industry status, discusses the development direction of laser technology at NCRIEO in the future.
