scispace - formally typeset
Search or ask a question
Author

Yongzhong Li

Bio: Yongzhong Li is an academic researcher from Fudan University. The author has contributed to research in topics: Laser beam quality & Beam (structure). The author has an hindex of 3, co-authored 3 publications receiving 62 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the beam combining of fiber array with hexagonal ring distribution is studied in detail and theoretical analysis and numerical calculation results are given to illustrate the propagation properties of the resulting beam through free space.
Abstract: Beam combining of fiber array with hexagonal ring distribution is studied in detail. The theoretical analysis and numerical calculation results are given to illustrate the propagation properties of the resulting beam through free space. A comparison between the coherent and the incoherent case shows that high peak irradiance and good beam quality for coherent combining can be obtained in the far field. The effect of phase errors and the beam quality M2 factor are also studied. Results indicate that the element numbers should be increased to achieve high power and the space between adjacent elements should be reduced to maintain good beam quality, which is basically the same for both coherent and incoherent beam combining.

41 citations

Journal ArticleDOI
TL;DR: In this article, the effects of phase errors and beam quality M 2 factor on coherent and incoherent beam combining were studied in a fiber array with hexagonal ring distribution and the theoretical analysis and numerical calculation results were given to illustrate the propagation properties of the resulting beam through free space.

20 citations

Journal ArticleDOI
TL;DR: In this article, the phase-matching condition in a fiber is discussed and a balance among the different orders of fiber dispersion is found to achieve a widely tuning modulation instability gain for pumping around the normal dispersion regime.

6 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this paper, the current status of fiber-based optical parametric oscillators is presented with a focus on pulsed systems employing microstructure fibers, and it is shown that systems employing short (less than a few cm) optical fibers lead to superior performance in terms of wavelength tunability and output power.
Abstract: The current status of fiber based optical parametric oscillators is presented with a focus on pulsed systems employing microstructure fibers. It is shown based on standard expressions for parametric processes in optical fibers that systems employing short (less than a few cm) optical fibers lead to superior performance in terms of wavelength tunability and output power. Practical guidelines for realizing a working system are given. These devices are now practical as ultrafast pulsed-light sources and for extending the wavelengths of operation of existing mode-locked fiber lasers.

114 citations

Journal ArticleDOI
TL;DR: It is proved that traditional beam quality criteria, such as the M2 factor and the Strehl ratio, do not consider necessary information to evaluate the quality of a coherently combined laser beam, and the beam propagation factor is introduced and studied as a proper beam quality factor.
Abstract: Numerical analysis of the effects of aberrations on coherently combined fiber laser beams is presented. We prove that traditional beam quality criteria, such as the M2 factor and the Strehl ratio, do not consider necessary information to evaluate the quality of a coherently combined laser beam. The beam propagation factor (BPF) is introduced and studied as a proper beam quality factor for the coherently combined beam. Two main categories of aberrations, geometry and nongeometry factors, are numerically studied to investigate their effect on beam quality by using the BPF criterion. For a ring-distributed fiber laser array with certain vacancy factor and a RMS value of tilt error, we obtain a semianalytical equation to evaluate their effect on beam quality. We present a brief discussion of those aberrations at the end of this paper. Our generalized methodology offers a good reference for investigating coherent combining of fiber laser beams in a comprehensive way.

44 citations

Journal ArticleDOI
TL;DR: In this article, the beam quality of a coherently combined beam is studied in detail and a theoretical analysis and a numerical calculation are given to illustrate that the M 2 factor is not a proper means for evaluating the beam qualities of coherently merged beam.
Abstract: The beam quality factor for a coherently combined beam is studied in detail. A theoretical analysis and a numerical calculation are given to illustrate that the M 2 factor is not a proper means for evaluating the beam quality of a coherently combined beam. The beam propagation factor is introduced to evaluate the beam quality. The effect of phase error on the beam quality is also studied. Results indicate that the beam quality of a coherently combined beam depends mainly on the fill factor of the laser array and not on the number of lasers. It is also revealed that the allowed phase error does not change with the number of lasers in order to ensure the energy encircled in a certain bucket.

33 citations

Journal ArticleDOI
TL;DR: In this article, phase-locked partially coherent flattened beam array propagating in a turbulent atmosphere is derived based on the extended Huygens-Fresnel principle, and the beam propagation factor (BPF) is introduced to evaluate the beam quality at the receiving plane.

30 citations

Journal ArticleDOI
TL;DR: In this paper, a phase-locked ring-array GaN-based vertical-cavity surface-emitting laser (VCSEL) was demonstrated using a floral-patterned structure, based on a buried-SiO2 lateral optical confinement technique.
Abstract: A phase-locked ring-array GaN-based vertical-cavity surface-emitting laser (VCSEL) was demonstrated using a floral-patterned structure, based on a buried-SiO2 lateral optical confinement technique. This structure enabled the realization of evanescently coupled waveguides in the circumferential direction with a high differential quantum efficiency of 30%, even in a blue GaN-based VCSEL. A coupled ring array with eight optical spots produced a very narrow divergence beam of 2.8° with an on-axis far-field emission. These results, together with single-longitudinal-mode operation in the lasing spectrum, provide evidence that the proposed GaN-based VCSEL exhibits in-phase supermode operation.A phase-locked ring-array GaN-based vertical-cavity surface-emitting laser (VCSEL) was demonstrated using a floral-patterned structure, based on a buried-SiO2 lateral optical confinement technique. This structure enabled the realization of evanescently coupled waveguides in the circumferential direction with a high differential quantum efficiency of 30%, even in a blue GaN-based VCSEL. A coupled ring array with eight optical spots produced a very narrow divergence beam of 2.8° with an on-axis far-field emission. These results, together with single-longitudinal-mode operation in the lasing spectrum, provide evidence that the proposed GaN-based VCSEL exhibits in-phase supermode operation.

21 citations