Frequency-Modulated Pulse Waveform Measurement Based on Lens Array and Fiber Bundle
【Abstract】This study proposes a method based on lens array and fiber bundle for measuring frequency-modulated pulse waveforms. Grade-index fiber can provide a large receiver aperture that allows optimum laser energy transmission and performing measurements a wide dynamical range. Lens array can decrease the drift of laser spot on the fiber end face. Combining these two benefits, the system will have a high transmission efficiency from the laser near field to the fiber bundle. Results indicate that the proposed method can perform high-accuracy measurements of frequency-modulated pulse waveforms, with the measurement contrast ratio reaching 630:1.
【Keywords】 laser optics; waveform measurement; lens array; fiber bundle; coupling efficiency; contrast ratio;
 Liao B. Theoretical study of FM to AM issue on ICF facility [D]. Shanghai: University of Chinese Academy of Sciences, 2006: 50–51 (in Chinese).
 Liu L Q, Zhang Y, Geng Y C, et al. Propagation characteristics of small-bandwidth pulsed beams with smoothing by spectral dispersion in high power laser system [J]. Acta Physica Sinica, 2014, 63 (16): 164201 (in Chinese).
 Sun Z H, Dong J, Xia Y W, et al. Temporal profile measurement of frequency modulation beams for high power laser facility [J]. Chinese Journal of Lasers, 2013, 40 (11): 1102009 (in Chinese).
 Li L, Zhang B, Xia Y W, et al. Pulse temporal profile measurement technology of frequency modulation based on self-focusing lens coupling optical fiber sampling for high power laser facility [J]. Chinese Journal of Lasers, 2017, 44 (5): 0504002 (in Chinese).
 Leng Y X. Shanghai superintense ultrafast laser facility [J]. Chinese Journal of Lasers, 2019, 46 (1): 0100001 (in Chinese).
 Kong X, Yan S S, Yu J W, et al. Reliability analysis of pulse width measurement in parameter measurement of petawatt-class laser [J]. Chinese Journal of Lasers, 2017, 44 (11): 1104001 (in Chinese).
 Lu Z G, Xia Y W, Tang J, et al. Pulse-shape measurement technology for multi-beams infrared laser [J]. Infrared and Laser Engineering, 2011, 40 (6): 1129–1132 (in Chinese).
 Xia Y W, Sun Z H, Zhao R C, et al. Improvement of infrared temporal profile measurement system for SG-Ⅲ prototype laser facility [J]. Infrared and Laser Engineering, 2012, 41 (6): 1453–1457 (in Chinese).
 Ermolaeva G M. Low-dispersion optical fiber highly transparent in the UV spectral range [J]. Optical Engineering, 2004, 43 (12): 2896–2903.
 Xiao Z G, Li B C. Single-lens coupling efficiency of a fundamental Gaussian beam to an optical fiber [J]. Opto-Electronic Engineering, 2008, 35 (8): 29–34 (in Chinese).
 Zhang S Q, Zhang Z, Cai L, et al. Laser injecting method from free space beam to single-mode fiber using single lens [J]. High Power Laser and Particle Beams, 2014, 26 (3): 031006 (in Chinese).
 Hirooka T, Hori Y, Nakazawa M. Gaussian and sech approximations of mode field profiles in photonic crystal fibers [J]. IEEE Photonics Technology Letters, 2004, 16 (4): 1071–1073.
 Chen X K, Zhang L, Wu Z Y. Coupling efficiency of free-space laser coupling into single mode fiber and photonic crystal fiber [J]. Chinese Optics, 2013, 6 (2): 208–215 (in Chinese).
 Tang Q, Yang L, Guo Y J, et al. Research of sampling and propagating characteristics of high power ultraviolet nanosecond laser pulse [J]. Chinese Journal of Lasers, 2013, 40 (9): 0905006 (in Chinese).
 Yang Y H, Yang W, Jiang T, et al. Investigation on characteristics of stimulated Raman threshold in a single mode fiber [J]. Acta Optica Sinica, 2014, 34 (1): 0129001 (in Chinese).
 Sun L Y, Huang M S, Huang J F, et al. Research on SBS threshold in single-mold fiber [J]. Journal of Beijing Institute of Petro-Chemical Technology, 2013, 21 (2): 9–12 (in Chinese).