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. 2022 Mar 29;22(7):2621.
doi: 10.3390/s22072621.

Fully Customized Photoacoustic System Using Doubly Q-Switched Nd:YAG Laser and Multiple Axes Stages for Laboratory Applications

Unsang Jung  1 , Jin Hyuck Choi  2 , Han Tae Choo  3 , Gyu Ug Kim  3 , Jaemyung Ryu  3 , Hojong Choi  4
Affiliations

Fully Customized Photoacoustic System Using Doubly Q-Switched Nd:YAG Laser and Multiple Axes Stages for Laboratory Applications

Unsang Jung et al. Sensors (Basel). .

Abstract

We developed a customized doubly Q-switched laser that can control the pulse width to easily find weak acoustic signals for photoacoustic (PA) systems. As the laser was constructed using an acousto-optic Q-switcher, in contrast to the existing commercial laser system, it is easier to control the pulse repetition rate and pulse width. The laser has the following control ranges: 10 Hz-10 kHz for the pulse repetition rate, 40-150 ns for the pulse width, and 50-500 μJ for the pulse energy. Additionally, a custom-made modularized sample stage was used to develop a fully customized PA system. The modularized sample stage has a nine-axis control unit design for the PA system, allowing the sample target and transducer to be freely adjusted. This makes the system suitable for capturing weak PA signals. Images were acquired and processed for widely used sample targets (hair and insulating tape) with the developed fully customized PA system. The customized doubly Q-switched laser-based PA imaging system presented in this paper can be modified for diverse conditions, including the wavelength, frequency, pulse width, and sample target; therefore, we expect that the proposed technique will be helpful in conducting fundamental and applied research for PA imaging system applications.

Keywords: customized laser system; doubly Q-switch; photoacoustic system.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Schematic of the developed doubly Q-switched Nd:YAG laser and (b) the implemented laser optical system.
Figure 2
Figure 2
(a) Measured spectrum of the doubly Q-switched 1064 nm Nd:YAG laser, (b) pulse train of the AO Q-switched 1064 nm Nd:YAG laser.
Figure 3
Figure 3
Comparison of single pulse signals for (a) doubly, (b) AO, (c) Cr:YAG passively Q-switched 1064 nm Nd:YAG laser.
Figure 4
Figure 4
Characteristics of developed doubly Q-switched 1064 nm Nd:YAG laser. (a) Comparison of output energy according to incident pump power, (b) comparison of output pulse width according to incident pump power, (c) comparison of output pulse width according to pulse repetition rate, (d) stability of output energy, according to the sample numbers.
Figure 5
Figure 5
Connection structure for the modules of the implemented PA imaging system: (a) optics platform and (b) data-processing structure.
Figure 6
Figure 6
Implemented PA imaging system: (a) optical system combined with each developed area; (b) laser-delivery optics; (c) overall structure of the fabricated sample stage.
Figure 7
Figure 7
Experimental setup for PA imaging: (a) experimental setup; (b) sample target used.
Figure 8
Figure 8
Experimental results for the PA imaging system obtained using insulating tape and hair: (a) original imaging result for insulating tape; (b) 3D reconstruction result for insulating tape; (c) insulating tape imaging result view of x- and y-axes; (d) result view of y- and z-axes; (e) result view of x- and z-axes; (f) original imaging result for the hair; (g) 3D reconstruction result for the hair; (h) hair imaging result view of x- and y-axes; (i) result view of y- and z-axes; (j) result view of x- and z-axes.
Figure 9
Figure 9
Reconstructed hair PA image results: (a) MIP image result; (b) PA image result by depth; (c) 3D rotation view of the hair PA image result; (b,c) are video clips (ref. attachment file).
See this image and copyright information in PMC

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