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In optically scattering media, the penetration depth and spatial resolution of light imaging are greatly limited. Acousto-optic imaging (AOI) is a promising hybrid approach based on frequency tagging of photons by an ultrasonic wave. However, AOI imposes stringent laser requirements: single-frequency emission, wide tunability within the therapeutic window (700-1000 nm), high peak power (~100 W) in a so-called ‘quasi-continuous' mode with long pulses of around 100 µs and a repetition rate of up to 100 Hz.The objective of this thesis is to develop a new laser source, adapted to these constraints, based on an oscillator-amplifier architecture with laser crystals doped with transition metal ions. Three amplifier materials were studied: Ti:sapphire, Cr:LiSAF and alexandrite, selected for their wide gain band in the near infrared.A central focus of the work is the development of innovative LED pumping technology using a luminescent concentrator, which had to be scaled up to meet the specifications of the laser source. To achieve this, three levers were used: increasing the unit power of the LEDs, multiplying their number, and optimising a Ce:YAG luminescent concentrator, including an innovative ‘edge' geometry. An advanced optical model was developed and validated experimentally, highlighting the critical role of losses associated with the average propagation distance, particularly due to absorption by the excited state. The pump head resulting from this work delivers up to 2.6 kW of peak power between 530 nm and 630 nm, setting a record level of performance in this spectral range.The integration of this technology into geometric multi-pass amplifiers made it possible to evaluate the performance of the three crystals. Ti:sapphire proved to be limited by insufficient gain in the quasi-continuous regime. Cr:LiSAF demonstrated a single-frequency signal at 830 nm reaching 9 W over 100 µs, but remains constrained by gain saturation and unfavourable thermal behaviour.Alexandrite has proven to be the most promising material: thanks to the long lifetime of the excited state and increasing gain with temperature, a multi-pass amplifier delivering a net gain of 34 after 16 passes and a peak power of 14 W at 761 nm has been demonstrated, setting a record for IAO. Interference effects limiting operation to 100 µs were identified and partially eliminated.This work marks a significant step forward towards more powerful optical imaging devices with greater penetration into biological tissue. Furthermore, it demonstrates the relevance of a new laser technology based on LED-pumped alexandrite, whose potential applications extend far beyond acousto-optic imaging: LiDAR, femtosecond chains, and UV lasers for microelectronics are just a few examples.