Manikanta E, Vinoth Kumar L, Venkateshwarlu P, Leela Ch, Kiran P Prem
Appl Opt. 2016 Jan 20;55(3):548-55. doi: 10.1364/AO.55.000548.
Acoustic shock waves (ASWs) in the frequency range of 30-120 kHz generated during laser-induced breakdown (LIB) of ambient air using 7 ns and 30 ps pulse durations are studied. The specific frequency range and peak amplitudes are observed to be different for nanosecond (ns) and picosecond (ps) LIB. The ASW frequencies for ps-LIB lie between 90 and 120 kHz with one dominant peak, whereas for ns-LIB, two dominant peaks with frequencies in the 30-70 kHz and 80-120 kHz range are observed. These frequencies are observed to be laser pulse intensity dependent. With increasing energy of ns laser pulses, acoustic frequencies move toward the audible frequency range. The variation in the acoustic parameters, such as peak-to-peak pressures, signal energy, frequency and acoustic pulse widths as a function of laser energy, for two different pulse durations are presented in detail and compared. The acoustic emissions are observed to be higher for ns-LIB than ps-LIB, indicating higher conversion efficiency of optical energy into mechanical energy.
研究了使用7纳秒和30皮秒脉冲持续时间在环境空气激光诱导击穿（LIB）过程中产生的频率范围为30 - 120千赫兹的声冲击波（ASW）。观察到纳秒（ns）和皮秒（ps）激光诱导击穿的特定频率范围和峰值幅度有所不同。皮秒激光诱导击穿的声冲击波频率在90至120千赫兹之间，有一个主峰，而对于纳秒激光诱导击穿，观察到两个主峰，频率分别在30 - 70千赫兹和80 - 120千赫兹范围内。观察到这些频率与激光脉冲强度有关。随着纳秒激光脉冲能量的增加，声频向可听频率范围移动。详细呈现并比较了两种不同脉冲持续时间下，诸如峰峰值压力、信号能量、频率和声脉冲宽度等声学参数随激光能量的变化。观察到纳秒激光诱导击穿的声发射比皮秒激光诱导击穿的更高，表明光能到机械能的转换效率更高。
