Characteristics of the photoacoustic signal excited by an intensity-modulated continuous-wave laser

Abstract

The time-domain and frequency-spectrum characteristics of the photoacoustic signal excited by an intensity-modulated continuous-wave laser were obtained by calculation based on theoretical analysis, and were also compared with the characteristics of the sound signal excited by pulsed lasers. The frequency spectrum of the photoacoustic signal excited by an intensity-modulated continuous-wave laser was distributed evenly in a wider band width, and a higher signal to noise ratio (SNR) of the sound signal was achieved by a narrowband detector compared with the SNR of the sound signal excited by pulsed lasers. In order to improve the axial resolution of the photoacoustic signal excited by a continuous-wave laser, we increased the compression ratio and compressed the pulse width of the sound signal. Compared with the high pulse energy of the pulsed laser, the lower laser power of the continuous-wave laser can load a higher power density in biological tissues without damaging the tissues within a certain time.

Detection of weak optical absorption by optical-resolution photoacoustic microscopy

“…Photoacoustic imaging (PAI) is a non-invasive biomedical imaging technique that combines the merits of rich optical absorption contrast and deep ultrasound detection [1] , [2] , [3] , [4] , [5] , [6] . In PAI, acoustic waves are generated by transient light absorption and thermoelastic expansion [7] , [8] . An ultrasonic transducer or transducer array detects the acoustic waves, and forms an image that maps the original optical energy deposition.…”

A frequency-stabilized laser based on a hollow-core photonic crystal fiber CO2 gas cell and its application scheme

“…The laser frequency stabilization system is based on frequency modulation (FM) [13,14] spectroscopy with the HC-PCF cell. A schematic is shown in figure 1.…”

High efficiency sub-nanosecond electro–optical Q-switched laser operating at kilohertz repetition frequency*

“…Solid state lasers with kilohertz (kHz) level pulse repetition frequency (PRF), sub nanosecond (ns) pulse width (PW), and pulse energy higher than 1 milijoule (mJ) are very attractive for a variety of applications, such as laser ranging, microprocessing, nonlinear frequency conversion, photoacoustic imaging, surface physics, and material science. [1][2][3][4][5][6][7][8] Many techniques, including electro-optical (EO) Qswitching, passive Q-switching using saturable absorber, [9,10] mode-locking, [11] and stimulated Brillouin scattering (SBS), [12] can be used to build the lasers with PW at ns or picosecond level. In comparison with the others, EO Q-switched lasers have a lot of advantages, e.g., better controllability, easy-to-realize synchronization, high stability and reliability, etc.…”