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Lasers and Laser Optics|182 Article(s)
Engineered quasi-phase-matching for laser techniques [Invited]
X. P. Hu, P. Xu, and S. N. Zhu
The quasi-phase-matching (QPM) technique has drawn increasing attention due to its promising applications in areas such as nonlinear frequency conversion for generating new laser light sources. In this paper, we will briefly review the main achievements in this field.Wegive a brief introduction of the invention ofQPMtheory, followed by the QPM-material fabrication techniques. When combing QPM with the solid-state laser techniques, various laser light sources, such as single-wavelength visible lasers and ultraviolet lasers, red–green–blue three-fundamentalcolor lasers, optical parametric oscillators in different temporal scales, and passive mode-locking lasers based on cascaded second-order nonlinearity, have been presented. The QPM technique has been extended to quantum optics recently, and prospects for the studies are bright. The quasi-phase-matching (QPM) technique has drawn increasing attention due to its promising applications in areas such as nonlinear frequency conversion for generating new laser light sources. In this paper, we will briefly review the main achievements in this field.Wegive a brief introduction of the invention ofQPMtheory, followed by the QPM-material fabrication techniques. When combing QPM with the solid-state laser techniques, various laser light sources, such as single-wavelength visible lasers and ultraviolet lasers, red–green–blue three-fundamentalcolor lasers, optical parametric oscillators in different temporal scales, and passive mode-locking lasers based on cascaded second-order nonlinearity, have been presented. The QPM technique has been extended to quantum optics recently, and prospects for the studies are bright.
Photonics Research
- Publication Date: Dec. 15, 2013
- Vol. 1, Issue 4, 04000171 (2013)
Coherent beam combination of fiber lasers with a strongly confined tapered self-imaging waveguide: theoretical modeling and simulation
Rumao Tao, Xiaolin Wang, Hu Xiao, Pu Zhou, and Lei Si
Coherent beam combination (CBC) of fiber lasers based on self-imaging properties of a strongly confined tapered waveguide (SCTW) is studied systematically. Analytical formulas are derived for the positions, amplitudes, and phases of the N self-images at the output of a SCTW, which are important for quantitative analysis of waveguide-based CBC. The formulas are verified with numerical examples by a finite difference beam propagation method (FDBPM) and the errors of the analytical expressions are studied. This study shows that the analytical formulas agree well with the FDBPM simulation results when the taper angle is less than 1.4° and the phase distortion is less than λ/10. The relative errors increase as the taper angle increases. Based on the theoretical model and the FDBPM, we simulated the CBC of fiber laser array and compared the CBC based on the tapered waveguide with that based on the nontapered one. The effects of input beam number, aperture fill factor, and taper angle on the combination performance have been studied. The study reveals that a beam which has near-diffraction limited beam quality (M2≤1.41) and a single beam without side lobe in the far field can be achieved with tapered-waveguide-based CBC. It is shown that beam quality depends on input beam number, aperture fill factor, and taper angle. There exists a best fill factor which will increase as input beam number increases. The tolerance of the system on the fill factor and the taper angle is studied, which is 0.45t0.67 and θ0.8°, respectively. The results may be useful for practical, high-power fiber laser systems. Coherent beam combination (CBC) of fiber lasers based on self-imaging properties of a strongly confined tapered waveguide (SCTW) is studied systematically. Analytical formulas are derived for the positions, amplitudes, and phases of the N self-images at the output of a SCTW, which are important for quantitative analysis of waveguide-based CBC. The formulas are verified with numerical examples by a finite difference beam propagation method (FDBPM) and the errors of the analytical expressions are studied. This study shows that the analytical formulas agree well with the FDBPM simulation results when the taper angle is less than 1.4° and the phase distortion is less than λ/10. The relative errors increase as the taper angle increases. Based on the theoretical model and the FDBPM, we simulated the CBC of fiber laser array and compared the CBC based on the tapered waveguide with that based on the nontapered one. The effects of input beam number, aperture fill factor, and taper angle on the combination performance have been studied. The study reveals that a beam which has near-diffraction limited beam quality (M2≤1.41) and a single beam without side lobe in the far field can be achieved with tapered-waveguide-based CBC. It is shown that beam quality depends on input beam number, aperture fill factor, and taper angle. There exists a best fill factor which will increase as input beam number increases. The tolerance of the system on the fill factor and the taper angle is studied, which is 0.45t0.67 and θ0.8°, respectively. The results may be useful for practical, high-power fiber laser systems.
Photonics Research
- Publication Date: Oct. 07, 2013
- Vol. 1, Issue 4, 04000186 (2013)
Theoretical analysis of a quasi-Bessel beam for laser ablation
Pinghui Wu, Chenghua Sui, and and Wenhua Huang
A quasi-Bessel beam (QBB) is suitable for laser ablation because it possesses a micrometer-sized focal spot and long depth of focus simultaneously. In this paper, the characterizations of QBBs formed by the ideal axicon and oblate-tip axicon are described. Strong on-axis intensity oscillations occur due to interference between the QBB and the refracted beam by the oblate tip. Using the axicon for laser ablation was theoretically investigated. Simple analytical formulas can be used to predict the required laser parameters, including the laser pulse energy, the generated fluence distributions, and the beam diameters. A quasi-Bessel beam (QBB) is suitable for laser ablation because it possesses a micrometer-sized focal spot and long depth of focus simultaneously. In this paper, the characterizations of QBBs formed by the ideal axicon and oblate-tip axicon are described. Strong on-axis intensity oscillations occur due to interference between the QBB and the refracted beam by the oblate tip. Using the axicon for laser ablation was theoretically investigated. Simple analytical formulas can be used to predict the required laser parameters, including the laser pulse energy, the generated fluence distributions, and the beam diameters.
Photonics Research
- Publication Date: May. 15, 2014
- Vol. 2, Issue 3, 03000082 (2014)
Graphene oxide paper as a saturable absorber for Er- and Tm-doped fiber lasers
Jakub Boguslawski, Jaroslaw Sotor, Grzegorz Sobon, Rafal Kozinski, Krzysztof Librant, Magdalena Aksienionek, Ludwika Lipinska, and Krzysztof M. Abramski
In this work pulse generation in both the 1.5 and 2 μm spectral ranges using a graphene oxide (GO)-paper-based saturable absorber in Er- and Tm-doped fiber lasers is presented. The article describes the fabrication method of GO paper and its characterization. The performance of both lasers is discussed in detail. Stable, mode-locked operation provides 613 fs and 1.36 ps soliton pulses centered at 1565.9 and 1961.6 nm in Er- and Tm-doped fiber lasers, respectively. Furthermore, scaling of spectral width, and hence the pulse duration, by increasing the number of GO paper layers in the Er-doped laser is described. The versatility and simplicity ofGOpaper fabrication combined with the possibility of scaling the optical spectrum full width at half-maximum are essential features that make it a good candidate for ultrafast low-power mode-locked lasers operating in different spectral regions. In this work pulse generation in both the 1.5 and 2 μm spectral ranges using a graphene oxide (GO)-paper-based saturable absorber in Er- and Tm-doped fiber lasers is presented. The article describes the fabrication method of GO paper and its characterization. The performance of both lasers is discussed in detail. Stable, mode-locked operation provides 613 fs and 1.36 ps soliton pulses centered at 1565.9 and 1961.6 nm in Er- and Tm-doped fiber lasers, respectively. Furthermore, scaling of spectral width, and hence the pulse duration, by increasing the number of GO paper layers in the Er-doped laser is described. The versatility and simplicity ofGOpaper fabrication combined with the possibility of scaling the optical spectrum full width at half-maximum are essential features that make it a good candidate for ultrafast low-power mode-locked lasers operating in different spectral regions.
Photonics Research
- Publication Date: Jul. 15, 2015
- Vol. 3, Issue 4, 04000119 (2015)
Optimization of spectral distortion in a ytterbium-doped mode-locked fiber laser system
Fuqiang Lian, Zhongwei Fan, Zhenao Bai, Xiaohui Li, and Qi Jie Wang
A method for optimizing the spectral distortion of an ultrafast pulse in a polarization-maintaining picosecond linear-cavity fiber laser with a one-stage fiber amplifier is proposed and demonstrated. The mechanism of control of the spectral distortion in the fiber system has been investigated. The experimental and theoretical results illustrate that the filtering effect of a fiber Bragg grating can effectively decrease the spectral oscillatory distortion accumulated by self-phase modulation. Injected into a Nd:YAG regenerative amplifier, the ultrafast pulse could produce high pulse energy of 1.2 mJ at a repetition rate of 1 kHz. A method for optimizing the spectral distortion of an ultrafast pulse in a polarization-maintaining picosecond linear-cavity fiber laser with a one-stage fiber amplifier is proposed and demonstrated. The mechanism of control of the spectral distortion in the fiber system has been investigated. The experimental and theoretical results illustrate that the filtering effect of a fiber Bragg grating can effectively decrease the spectral oscillatory distortion accumulated by self-phase modulation. Injected into a Nd:YAG regenerative amplifier, the ultrafast pulse could produce high pulse energy of 1.2 mJ at a repetition rate of 1 kHz.
Photonics Research
- Publication Date: May. 21, 2015
- Vol. 3, Issue 4, 04000129 (2015)
Modification of wettability of stainless steel by picosecond laser surface microstructuring
Zongjie Bao, Chengwei Wang, Yang Zhang, and Quan-Zhong Zhao
We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy. We report on the modification of the wettability of stainless steel by picosecond laser surface microstructuring in this paper. Compared with traditional methods, picosecond laser-induced surface modification provides a fast and facile method for surface modification without chemical damage and environmental pollution. As a result of treatment by 100 ps laser pulses, microstructures are fabricated on the stainless steel sample surface, contributing to the increase of the contact angle from 88° to 105°, which realizes a transformation from hydrophilicity to hydrophobicity. The morphological features of fabricated microstructures are characterized by scanning electron microscopy and optical microscopy.
Photonics Research
- Publication Date: Jun. 06, 2015
- Vol. 3, Issue 4, 04000180 (2015)
High-peak-power passivelyQ-switched Nd:YAG/Cr4+:YAG composite laser with multiple-beam output
T. Dascalu, G. Croitoru, O. Grigore, and N. Pavel
We report on the design, realization, and output performance of a diode-pumped high-peak-power passively Q-switched Nd:YAG∕Cr4:YAG composite medium onolithic laser with four-beam output. The energy of a laser pulse was higher than 3 mJ with duration of 0.9 ns. The proposed system has the ability to choose independently the focus of each beam. Such a laser device can be used for multipoint ignition of an automobile gasoline engine, but could also be of interest for ignition in space propulsion or in turbulent conditions specific to aeronautics. We report on the design, realization, and output performance of a diode-pumped high-peak-power passively Q-switched Nd:YAG∕Cr4:YAG composite medium onolithic laser with four-beam output. The energy of a laser pulse was higher than 3 mJ with duration of 0.9 ns. The proposed system has the ability to choose independently the focus of each beam. Such a laser device can be used for multipoint ignition of an automobile gasoline engine, but could also be of interest for ignition in space propulsion or in turbulent conditions specific to aeronautics.
Photonics Research
- Publication Date: Nov. 15, 2016
- Vol. 4, Issue 6, 06000267 (2016)
73 nJ, 109 fs Yb-doped fiber laser at 19 MHz repetition rate in amplifier similariton regime
Yizhou Liu, Yifan Cui, Jian Zhang, Aimin Wang, and Zhigang Zhang
We report femtosecond pulse generation in an amplifier similariton oscillator and a prechirped fiber amplifier system. The final output power is 1.4 W, and the fundamental repetition rate is 19.1 MHz after a single state fiber amplifier. The pulsewidth is 109 fs. We report femtosecond pulse generation in an amplifier similariton oscillator and a prechirped fiber amplifier system. The final output power is 1.4 W, and the fundamental repetition rate is 19.1 MHz after a single state fiber amplifier. The pulsewidth is 109 fs.
Photonics Research
- Publication Date: Aug. 25, 2015
- Vol. 3, Issue 5, 05000248 (2015)
Propagation of high-power fiber laser with high-order-mode content
Rumao Tao, Long Huang, Pu Zhou, Lei Si, and Zejin Liu
Propagation properties of high-power fiber laser with high-order-mode (HOM) content are studied numerically for the first time to the best of our knowledge. The effect of HOM on the propagation property is evaluated by the power in the bucket (PIB) metric. It is shown that PIB is mainly dependent on HOM content rather than the relative phase between the fundamental mode and HOM. The PIB in vacuum is more than 80% when the power fraction of the HOM is controlled to be less than 50% at 5 km. The relative phase has an impact on the peak intensity position and concentration of the far-field intensity distribution. If an adaptive optics system is used to correct the peak intensity deviation, the results indicate that there exists a maximal value of PIB as relative phase increases. Such effect is weakened when propagating in turbulence. Compared to the laser beams without HOM, laser beams with HOM content are less influenced by the turbulence and can reduce average intensity fluctuation. The results may be useful in the design of a high-power fiber laser system. Propagation properties of high-power fiber laser with high-order-mode (HOM) content are studied numerically for the first time to the best of our knowledge. The effect of HOM on the propagation property is evaluated by the power in the bucket (PIB) metric. It is shown that PIB is mainly dependent on HOM content rather than the relative phase between the fundamental mode and HOM. The PIB in vacuum is more than 80% when the power fraction of the HOM is controlled to be less than 50% at 5 km. The relative phase has an impact on the peak intensity position and concentration of the far-field intensity distribution. If an adaptive optics system is used to correct the peak intensity deviation, the results indicate that there exists a maximal value of PIB as relative phase increases. Such effect is weakened when propagating in turbulence. Compared to the laser beams without HOM, laser beams with HOM content are less influenced by the turbulence and can reduce average intensity fluctuation. The results may be useful in the design of a high-power fiber laser system.
Photonics Research
- Publication Date: May. 11, 2015
- Vol. 3, Issue 4, 04000192 (2015)
Wavelength-swept fiber laser based on bidirectional used linear chirped fiber Bragg grating
Lin Wang, Minggui Wan, Zhenkun Shen, Xudong Wang, Yuan Cao, Xinhuan Feng, and Bai-ou Guan
A wavelength-swept fiber laser is proposed and successfully demonstrated based on a bidirectional used linear chirped fiber Bragg grating (LC-FBG). The wavelength-swept operation principle is based on intracavity pulse stretching and compression. The LC-FBG can introduce equivalent positive and negative dispersion simultaneously, which enables a perfect dispersion matching to obtain wide-bandwidth mode-locking. Experimental results demonstrate a wavelength-swept fiber laser that exhibits a sweep rate of about 5.4 MHz over a 2.1 nm range at a center wavelength of 1550 nm. It has the advantages of simple configuration and perfect dispersion matching in the laser cavity. A wavelength-swept fiber laser is proposed and successfully demonstrated based on a bidirectional used linear chirped fiber Bragg grating (LC-FBG). The wavelength-swept operation principle is based on intracavity pulse stretching and compression. The LC-FBG can introduce equivalent positive and negative dispersion simultaneously, which enables a perfect dispersion matching to obtain wide-bandwidth mode-locking. Experimental results demonstrate a wavelength-swept fiber laser that exhibits a sweep rate of about 5.4 MHz over a 2.1 nm range at a center wavelength of 1550 nm. It has the advantages of simple configuration and perfect dispersion matching in the laser cavity.
Photonics Research
- Publication Date: Apr. 18, 2017
- Vol. 5, Issue 3, 03000219 (2017)
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