We propose a 1950nm high average power, large pulse energy narrow-linewidth nanosecond pulse fiber laser. A closed-loop temperature control technique is employed in the design of the seed laser driving circuit system to ensure high power, high wavelength stability, and ultra-low noise characteristics. The acousto-optic modulator (AOM) is used to modulate the pulse of a continuous seed laser, and the rise time of the output pulse can be controlled to obtain the desired pulse shape and width. A master oscillating power amplifier (MOPA) structure is adopted to amplify the modulated power of the laser. Amplified by cascade amplification technique, the average output power of the pulse with the output pulse train has a repetition rate of 10MHz is 3.5W and the pulse width is 300ns, corresponding to a peak power of 1.17kW and a pulse energy of 350μJ. This type of fiber laser has vast possibilities of application especially in lidar and high-precision measurement.
High-power picosecond lasers have a wide range of applications in high-precision drilling, solar cell cutting, and ultrafast spectroscopy. The main oscillator power amplifier (MOPA) technology is an effective scheme to generate high-power picosecond pulses. The thermal effect of the laser gain medium significantly impacts both the laser power output and beam quality. This paper prioritizes constructing a thermal effect model of the gain medium and simulates the temperature field distribution inside the crystal under different pumping modes. Then the pulse string picosecond laser output was successfully realized using the self-developed picosecond fiber seed laser and a two-stage end-face pumped traveling wave amplifier. The maximum average output power of 26.1 W, 28 W, and 29.6 W was obtained when the pulse string contained 2, 5, and 10 sub-pulses, respectively, corresponding to pulse energies of 130.5 µJ, 140 µJ, and 148 µJ at a repetition rate of 200 kHz.
Marine instruments deployed in seawater inevitably experience biofouling, which severely reduces their service life and hinders ocean monitoring. Marine biofouling greatly affects the service life of marine optical instruments and thus has a detrimental impact on ocean monitoring. The fouling community exhibits an attachment succession phenomenon. Macroscopic fouling organisms have adherent and stubborn attachments, whereas microorganisms during early fouling stages are easy to remove, but excessive cleaning also greatly increases energy consumption. Therefore, monitoring biofouling and selecting appropriate removal timing is critical. Due to the complex and dynamic nature of the marine environment, in-situ detection of microbial fouling on optical window of marine optical instrument is challenging because of many factors such as target characteristics, seawater turbidity, light refraction and scattering. Currently, there are no mature technologies available for in-situ fouling detection so as to remove timely micro fouling. To solve this problem, this study deployed thin poly methyl methacrylate (PMMA) coupons within the coastal seawaters of Qingdao, followed by in-situ mapping of photoacoustic signals using a self-built excitation and detection platform, along with along with of transmittance spectrum analysis on fouled PMMA thin films using PerkinElmer LAMBDA750. By combining results from both techniques with microscopic morphology analysis, we explored the relationship between microbial fouling and photoacoustic signal. The research results will provide a novel approach and technical basis for in-situ detection and timely clearance of microbial fouling on optical windows of marine optical instruments.
In this work, an all-fiber high-power cascaded master-oscillator power amplifier (MOPA) system emitting frequency-stabilized single-frequency laser pulses at 1550 nm is presented. An external cavity laser diode with a narrow linewidth of 5 kHz is used as the seed source. Owing to the use of frequency locking components and a matched closed-loop system, the seed source has stable output frequency and power. The on-off extinction ratio of 80 dB is achieved by using digital and analog acousto-optic modulators in series. Then the seed laser is amplified by a three-stage cascaded all-fiber amplifier consisting of two pre-amplifiers and one main amplifier. The MOPA system delivers 200-ns laser pulses with a peak power of 800 W at a repetition rate of 10 kHz. The output laser has an operating linewidth close to the transform-limited. The polarization-extinction ratio is 20 dB, and the optical signal-to-noise ratio is higher than 45 dB. The monolithic all-fiber Erbium-Ytterbium co-doped pulsed fiber amplifier can be used as the high-energy radar transmitter of compact long-distance coherent Doppler lidar systems.
We demonstrated a 3.8 kW-level all-fiberized high-brightness laser with the structure of MOPA (master oscillator power amplification). The maximum output power is ~3894 W with the SRS (stimulated Raman scattering) intensity 10 dB below and ~3812 W with the SRS intensity 20 dB below. The spectrum has a central wavelength of 1080 nm with an FWHM (full width at half-maximum) bandwidth of ~2.2 nm. The slope efficiency of the fiber amplifier with respect to the pump power is ~81%. With a 25-μm-core ytterbium-doped gain fiber of the amplifier and 30-μm-core output fiber, the laser can keep a high beam quality (M2 ) which is estimated to be about 2.6 below.
A frequency-tunable Q-switched laser operation at 1064 nm pumped by a wavelength-locked 878 nm semiconductor diode was reported. Under CW operation mode, the maximum output power of 30.5 W was obtained while the pumping power was 55.9 W, and the light-light conversion efficiency was 54.56 %; While in the Q-switching operation mode, the maximum output power of 24.93 W was obtained when the pumping power was 53.05 W, and the light-light conversion efficiency was 46.54 %. Provides stable operation in Q-switching mode between 60 kHz and 300 kHz repetition frequency with a pulse width range of 22.5 ns to 24 ns. The laser with beam quality M 2x=1.21 and M2y=1.33 was obtained.
In this article, a fiber-solid hybrid amplification picosecond laser system is developed. The maximum single pulse energy of the fiber seed source can exceed 50 nJ and the beam quality factor M2 is less than 1.10. After two-stage traveling-wave amplifiers, the final average power of 23.6 W was obtained, corresponding to the maximum single pulse energy of 118 μJ with a repetition rate of 200 kHz. The research results of this article can provide an effective reference for the implementation of a higher-power Nd: YVO4 laser system.
An erbium-doped fiber laser based on nonlinear polarization rotation (NPR) mode-locking is proposed. On account of the multi-mode interference filtering effect introduced by the laser cavity multi-mode fiber, by adjusting the cavity polarization controllers, the laser generates dual-wavelengths of 1533.48 nm/1547.61 nm, 1549.16 nm/1561.94 nm, 1533.14 nm/1562.96 nm, and triple-wavelengths of 1533.43 nm, 1548.46 nm and 1562.68 nm, corresponding to 388.95 kHz, 388.93 kHz and 388.91 kHz, respectively. The compact structure of the system has potential applications in spectroscopy, optical communication, optical sensing and other fields.
Using ytterbium doped single-clad/double-clad fiber amplifiers, different amplification experiments were conducted on narrow pulse width picosecond light, and the influence of self-phase modulation on pulse frequency domain characteristics during amplification was analyzed. A self developed picosecond oscillator based on semiconductor saturable absorber mirror (SESAM) mode locking is used to directly enter the main amplifier device. The oscillator has a pulse width of 6.8 ps, a repetition rate of 20.76 MHz, and a center wavelength of 1064.3 nm. After amplification, the maximum output power is 315 mW, with an energy of about 15 nJ. The phenomenon of spectral changes caused by selfphase modulation of picosecond pulsed light during amplification is explored. When the output pulse optical power is about 200 mW and the pulse energy is about 10 nJ, and the injection power is 39.4 mW, 134 mW, 229.2 mW, and 326.8 mW, respectively, the corresponding spectral widths are 0.187 nm, 0.522 nm, 0.53 nm, and 0.588 nm, respectively. Experimental research shows that under the same output pulse energy conditions, the smaller the injected optical power, the better the output pulse spectral morphology. As the injected optical power decreases, the effect of pulse shape on self-phase modulation in fiber lasers decreases.
We mainly study the conversion efficiency of Erbium/Ytterbium (Er/Yb) co-doped silicate glass fiber (Nufern PM-EYDF-12/130-HE) under different pump wavelengths, pump methods, gain fiber length and input signal power. Through a series of experimental studies, it is found that the hybrid pump mode of multi-mode pump diodes at 976 nm and 915 nm/940 nm are more efficient than that of single-wavelength pumping. When the input signal power is 85 mW, the fiber length is 3.9 m, the hybrid pump power of 976 nm and 940 nm is 10 W respectively, the output optical power can reach 6.41 W, and the optical-to-optical conversion efficiency is 33.7 %, and the signal-to-noise ratio (SNR) is more than 45 dB. When the hybrid pump power of 976 nm and 915 nm is 10 W respectively, the output power can reach 6.31 W, and the PPCE is 33 %. Under the condition of 20 W reverse pump power, the optical-to-optical efficiency of 976 nm, 915 nm and 940 nm single-wavelength pump is 30.7 %, 25.2 % and 21.7 % respectively.
In recent years, 1.3 μm lasers have been widely used in laser medical treatment, optical fiber communication and optoelectronic countermeasures, etc. In this paper, the unstable cavity structure with double pump cavity connected in series and the method to optimize the thermal lens effect are used to obtain a maximum 41 W average power of continuous-wave laser. Meanwhile, the pulsed laser is realized through an acousto-optic Q switch and the repetition rate can be adjusted in the range of 1~10 kHz. The maximum single pulse energy can reach 8.44 mJ with the repetition frequency of 1 kHz, corresponding to 65 kW peak power. In the future, the output power will be further improved by optimizing the laser, which will be beneficial to expand the applications in related fields.
In recent years, picosecond lasers have developed rapidly and have been widely used in many fields such as precision processing, spectroscopy, ranging and medical treatment. A picosecond laser system with fiber-solid hybrid amplification is developed. Firstly, the central wavelength, polarization state and spectral width of the fiber seed source are optimized. The maximum energy can reach 100 nJ and the beam quality factor M2 is less than 1.10. Furthermore, double-end pump structure is used to amplify the optical power of the seed. The output power are 2.24 W and 10.8 W at 100 kHz and 13 MHz, respectively. The pulse width is 10.2 ps. By optimizing the design of optical path and thermal management technology, a better beam quality M2=1.2 is obtained. The research ideas and experimental results of this paper can provide an effective solution for further improving the power of amplifier.
Based on an all-fiber master oscillator power amplifier (MOPA) structure, a 1950-nm narrow-linewidth, single-mode, high peak power nanosecond pulsed fiber laser was developed. The seed source is a distributed feedback (DFB) semiconductor laser with a linewidth of 0.5 MHz. A precise and stable closed-loop temperature control technology is used to design the driving circuit of the seed laser, which ensures the stability of the laser wavelength and power, and greatly reduces the frequency and intensity noise of the laser. The continuous seed laser is modulated by an acousto-optic modulator (AOM). At the same time, the high-frequency control technology of acousto-optic modulator and cascade amplification technology are used to realize the continuous adjustable of laser pulse shape (Gaussian pulse or square wave pulse), repetition rate (1 kHz ~ 300 kHz) and pulse width (50 ns ~ 500 ns) of 2.0 μm band single frequency laser. This laser is very suitable for coherent lidar applications
The applications of femtosecond lasers are undergoing a period of explosive growth in the laser micromachining market. We demonstrated an all-normal-dispersion figure-8 mode-locked fiber oscillator using a nonlinear amplifying loop mirror, delivering laser pulses with 8.2-nJ pulse energy. The spectral bandwidth of 10 nm is realized at the repetition rate of 10 MHz. The pulse width of the chirped pulses is 6.7 ps and the output pulses can be compressed to below 200 fs. An all-normal-dispersion figure-9 laser is also presented in this letter. The repetition rate of the laser can be improved to 25.7 MHz. Owing to their compact sizes, high stability and superior self-starting ability, the all-normal-dispersion figure-8 and figure-9 lasers have the potential to be used in industrial grade femtosecond laser systems.
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