Open AccessMHz-ultrasound generation by chirped femtosecond laser pulses from gold nano-colloidal suspensions
Author(s) -
Frances Camille P. Masim,
Wei-Chou Hsu,
ChihHung Tsai,
Hao-Li Liu,
Matteo Porta,
Mai Thanh Nguyen,
Tetsu Yonezawa,
Armandas Balčytis,
Xuewen Wang,
Saulius Juodkazis,
Koji Hatanaka
Publication year - 2016
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.24.017050
Subject(s) - optics , femtosecond , materials science , laser , pulse duration , chirp , absorption (acoustics) , femtosecond pulse shaping , physics
Strong absorption of femtosecond laser pulses in Au nano-colloidal suspensions was used to generate coherent ultrasound signals at 1-20 MHz frequency range. The most efficient ultrasound generation was observed at negative chirp values and was proportional to the pulse duration. Maximization of a dimensionless factor A ≡ αc 0 tp defined as the ratio of pulse duration tp and the time required for sound at speed c 0 to cross the optical energy deposition length (an inverse of the absorption coefficient α) given by 1/(αc 0 ). Chirp controlled pulse duration allows effective enhancement of ultrasound generation at higher frequencies (shorter wavelengths) and is promising for a high spatial resolution acoustic imaging.