1：Experimental Design and Method Selection:

The study involves developing a theoretical model based on the frequency domain solution of the photoacoustic wave equation, improving upon previous work by Erkol et al. An experimental setup is established to validate this model using distilled water as the medium, with measurements of PA signals under various laser parameters.

2：Sample Selection and Data Sources:

Distilled water is used due to its known physical parameters and strong absorption at 1550 nm wavelength. Data is collected from PA signals generated by laser pulses.

3：List of Experimental Equipment and Materials:

Includes a diode laser (LPSC-1550-FC, Thorlabs Inc.), optical fiber (SMF-28-J9, Thorlabs Inc.), aspheric fiber collimators (CFS2-1550, CFS5-1550, Thorlabs Inc.), driver module (Picolas LDP-V 50-100 V3.3), arbitrary/function generator (AFG3021B, Tektronix), membrane hydrophone (HMA-0200, Onda Inc.), preamplifier (Boteg Inc.), final amplifier (AD8331-EVAL, Analog Devices Inc.), and oscilloscope/data logger (Picoscope 3206MSO).

4：3), arbitrary/function generator (AFG3021B, Tektronix), membrane hydrophone (HMA-0200, Onda Inc.), preamplifier (Boteg Inc.), final amplifier (AD8331-EVAL, Analog Devices Inc.), and oscilloscope/data logger (Picoscope 3206MSO). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The laser diode is pulsed using the driver module triggered by the function generator. PA signals are generated in distilled water, detected by the hydrophone, amplified, and measured with the oscilloscope. Frequency spectra are analyzed using FFT and processed with Matlab.

5：Data Analysis Methods:

Theoretical calculations are compared with experimental results. Frequency domain analysis is performed using FFT, and accuracy is assessed by comparing fundamental frequencies.