Author Affiliations
Abstract
Strong-Field and Ultrafast Photonics Lab, Institute of Laser Engineering, Beijing University of Technology, Beijing 100124, China
The self-formation of periodic subwavelength ripples by linear polarized femtosecond laser scanning planar and non-planar tungsten targets on the employed laser wavelength, scanning speed, and energy fluence are examined systematically. The results show that, for a certain laser wavelength, the scanning conditions have no obvious effect to the morphological features of grating structures in the threshold range of laser fluence. The spatial structured period of gratings can be self-consistently interpreted by recently presented physical model of surface two-plasmon resonance. The subwavelength structures on cylindrical surface would be a good method to realize unique surface functions on complex surface of micro-devices.
320.2250 Femtosecond phenomena 310.6628 Subwavelength structures,nanostructures 220.4000 Microstructure fabrication 350.3390 Laser materials processing Chinese Optics Letters
2016, 14(12): 123202
北京工业大学激光工程研究院, 强场与超快光子实验室, 北京 100124
在气压为1.33×10-4 Pa 和衬底温度为室温条件下，利用飞秒激光剥落石墨的方法在无催化层的硅(Si)衬底上加工碳纳米薄膜；探究了激光能量和沉积时间对碳纳米薄膜成膜情况的影响。通过拉曼光谱对碳纳米薄膜表面物质的组成进行了分析；利用扫描电镜(SEM)和原子力显微镜(AFM)来显示薄膜的表面结构；实验结果显示，辐照时间对ID/IG 的比值以及碳晶粒的大小都有显著的影响，并且高能量的飞秒激光脉冲能够促进碳晶粒的结晶。同时，在高能量的激光脉冲下沉积碳纳米薄膜，在Si表面发现了特殊图案的碳纳米结构：雪花状，方块状及四角星状。
薄膜 飞秒激光 脉冲激光沉积 碳纳米结构
Author Affiliations
Abstract
Strong-field and Ultrafast Photonics Lab, Institute of Laser Engineering, Beijing University of Technology, Beijing 100124, China
The films of few-layer graphene are formed through laser exfoliation of a highly ordered pyrolytic graphite (HOPG), without a catalytic layer for the growth process. The femtosecond (fs) laser exfoliation process is investigated at different laser fluences and substrate temperature. For fs laser exfoliation of HOPG, the few-layer graphene is obtained at 473 K under an optimal laser fluence. The formation of few-layer graphene is explained by removal of intact graphite sheets occurred by an optimal laser fluence ablation. The new insights may facilitate the controllable synthesis of large area few-layer graphene.
160.0160 Materials 310.0310 Thin films 350.0350 Other areas of optics Chinese Optics Letters
2015, 13(2): 021601
Author Affiliations
Abstract
Strong-Field and Ultrafast Photonics Lab, Institute of Laser Engineering, Beijing University of Technology, Beijing 100124, China
The periodic ripple structures on wolfram and titanium surfaces are induced experimentally by linear polarized femtosecond laser pulses at small incident angles. The structural features show a material difference in the s- and p-polarized laser irradiation. The interspace between the ripples increases significantly for p-polarized laser irradiation when it exceeds a threshold angle, and the ripples’ periodicities are larger than the wavelength of the incident p-polarized femtosecond laser; however, no significant change in the period of the ripples is observed with increasing incident angle for s-polarized laser irradiation. To explain these phenomena we propose a resonant absorption mechanism, by which the experimental observations can be interpreted.
100.0118 Imaging ultrafast phenomena 180.0180 Microscopy 350.0350 Other areas of optics Chinese Optics Letters
2015, 13(7): 071001
根据ErP5O14的吸收和荧光光谱,用Judd—Ofelt理论计算了在此晶体中Er3+的强度参数Ωλ（或τλ）,由此计算了激光能级辐射跃迁速率、辐射寿命、荧光分支比和积分发射截面等光谱参数。提出了在Peap与强度参数的总和之间存在直线关系的经验公式。讨论了ErP5O14作为激光材料的可能性。
本工作根据Jndd-Ofelt理论,利用28个吸收光谱支项,19组方程计算了实验与理论振子强度,均方根偏差仅为1.9×10~(-7).用最小二乘法拟合实验与理论振子强度所得到的三个Ω_λ唯像强度参数为:Ω_2-0.19×10~(20)cm~2;Ω_4=1.68×10~(-20)cm~2;Ω_6=0.62×10~(-2)cm~2.然后,计算了自发辐射电偶和磁偶跃迁几率,辐射寿命,荧光分支比与各激发态的辐射电偶和磁偶振子强度.并示出了0.3～0.2μm波段内的荧光光谱.
研究了HoP5O14晶体生长,测定了它的结构,分析了它的晶面与几何外形。研究了吸收、激发、荧光及红外光谱。首次测出了HoP5O14晶体中Ho3+的5I7—5I8跃迁在2.046微米。
