Name: Mr. Aman Dubey
S. R. Number: 01-02-00-10-22-24-1-25228
Title: Frequency-selective light emitting diode based tone burst excitation for photoacoustic sensing
Date & Time: July 07, 2026 (Tuesday) & 10:00 AM
Venue: SV Narasaiah Auditorium, IAP
Abstract:
Photoacoustic sensing is a hybrid technique that combines the high optical absorption contrast with time (depth) resolved acoustic measurement, making it attractive for biomedical sensing, material characterization, and chemical analysis. Conventional photoacoustic systems predominantly employ high-energy pulsed laser sources that generate broadband acoustic signals but are often expensive, bulky, and require stringent laser safety measures. Frequency-domain photoacoustic techniques provide frequency-selective excitation but require continuous-wave optical sources, precise modulation, and phase-sensitive detection, resulting in increased system complexity and comparatively lower signal-to-noise ratio. Although high-power light-emitting diodes (LEDs) have emerged as compact, low-cost alternatives for photoacoustic excitation, their relatively low optical pulse energy results in generation of weak photoacoustic signals with limited control over the generated acoustic spectrum.
This thesis investigates a programmable LED-based tone-burst excitation methodology for frequency-selective photoacoustic sensing. A theoretical framework is developed to describe finite tone-burst photoacoustic excitation by extending the conventional photoacoustic wave equation using Green’s function analysis. The developed model establishes analytical relationships between burst excitation parameters, the generated photoacoustic spectrum, and the temporal response of the ultrasonic transducer, demonstrating how the excitation frequency, burst length, and pulse repetition period independently govern the spectral characteristics of the generated photoacoustic signal. A temporal overlap criterion is further developed to explain the conditions responsible for burst-induced signal enhancement. The developed model also explains the origin of harmonic components generated under finite burst excitation and establishes the conditions required for burst-induced signal enhancement. To the best of our knowledge, this work presents the first theoretical and experimental investigation of programmable LED-based frequency-selective tone-burst excitation for photoacoustic sensing.
To validate the proposed approach, a programmable LED excitation system was designed and developed to generate both conventional single-pulse and frequency-selective tone-burst excitation waveforms for photoacoustic signal generation. The system comprises of a microcontroller-based waveform generator, a high-speed LED driver, a power switching stage, an energy storage unit, and a high-power near-infrared LED array operating at 850 nm. The excitation system was designed to deliver high-current nanosecond optical pulses while ensuring stable operation under programmable burst excitation. Electrical characterization demonstrated stable operation over the required operating range and the capability to drive low-impedance high-power LED loads with good linearity and repeatability. The system enables independent control of excitation frequency, burst length, pulse width, and pulse repetition period, allowing systematic investigation of burst excitation over the 1-5 MHz frequency range. Experimental results demonstrated signal amplitude enhancement of up to 70% near the transducer centre frequency, corresponding to an improvement of up to 5 dB in signal-to-noise ratio compared with conventional single-pulse LED excitation. The measured spectral characteristics were found to be in good agreement with the developed theoretical model. The developed sensing platform was further evaluated for quantitative photoacoustic sensing using copper sulphate (CuSO₄) solutions prepared over a concentration range of 0.25-2 mg/mL. The measured photoacoustic response exhibited a strong linear relationship with concentration (R² = 0.92) while maintaining less than 5% measurement variation, demonstrating the capability of the proposed system for reliable concentration estimation using compact LED excitation.
Overall, the thesis demonstrates that programmable LED-based tone-burst excitation provides a simple and effective approach for achieving electronically controllable, frequency-selective photoacoustic signal generation using compact LED excitation. The combination of theoretical analysis, programmable excitation, hardware development, and experimental validation provides a practical foundation for low-cost, portable photoacoustic sensing systems for future biomedical, chemical, and industrial applications.
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ALL ARE WELCOME