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A diode-pumped passively Q-switched Nd:YVO4 laser operating at 914nm is demonstrated. The solid-state laser is quasi-continuously pumped at 808nm using a 35W fiber-coupled diode laser. Several Cr4+:YAG saturable absorbers with different outcoupling coefficients are utilized to optimize the overall system performance. The simple two component cavity design reduces the system complexity and enables efficient pump power conversion along with long-term stability concerning power and wavelength. Furthermore, temperature dependent stimulated-emission cross-section in the Q-switched regime is investigated by observing the evolution of the single pulse energy over a temperature range of 70 K.

Date of Conference: 3–5 February 2013 Conference name: Proceedings of SPIE,Photons Plus Ultrasound: Imaging and Sensing 2013 Photoacoustic microscopy, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping. Clinically, photoacoustic microscopy is emerging as a capable diagnostic tool. Parameters of lasers used in photoacoustic microscopy, particularly, pulse duration, energy, pulse repetition frequency, and pulse-to-pulse stability affect signal amplitude and quality, data acquisition speed and indirectly, spatial resolution. Lasers used in photoacoustic microscopy are typically Q-switched lasers, low-power laser diodes, and recently, fiber lasers. Significantly, the key parameters cannot be adjusted independently of each other, whereas microvasculature and cellular imaging, e.g., have different requirements. Here, we report an integrated fiber laser system producing nanosecond pulses, covering the spectrum from 600 nm to 1100 nm, developed specifically for photoacoustic excitation. The system comprises of Yb-doped fiber oscillator and amplifier, an acousto-optic modulator and a photonic-crystal fiber to generate supercontinuum. Complete control over the pulse train, including generation of non-uniform pulse trains, is achieved via the AOM through custom-developed field-programmable gate-array electronics. The system is unique in that all the important parameters are adjustable: pulse duration in the range of 1-3 ns, pulse energy up to 10 μJ, repetition rate from 50 kHz to 3 MHz. Different photocoustic imaging probes can be excited with the ultrabroad spectrum. The entire system is fiber-integrated; guided-beam-propagation rendersit misalignment free and largely immune to mechanical perturbations. The laser is robust, low-cost and built using readily available components. © 2013 Copyright SPIE.