Gain-switched Ti:sapphire laser-based photoacoustic imaging

Abstract

We demonstrate photoacoustic (PA) imaging using a compact gain-switched Ti:sapphire laser. Additionally, a simple laser configuration is provided. The Ti:sapphire laser is pumped using a frequency-doubled pulsed neodymium-doped yttrium aluminum garnet pulse laser operating at a repetition rate of 10 Hz, with a pump energy of 37 mJ. No water cooling is required for the Ti:sapphire crystal. The output pulse energy and pulse duration of the laser are 13.6 mJ and 11 ns, respectively. Thus, the power conversion efficiency is 36.7%. As the end mirror in a laser cavity is adjusted in a horizontal direction, the output wavelength can be tuned within a range of 725-880 nm with a spectral bandwidth of approximately 1 nm. The laser has a small footprint size of 50 cm×35 cm including even laser pumping. Because the near-infrared region has significant advantages in the context of absorption and scattering in biological tissues, our laser can be used for PA imaging. Apart from obtaining PA images of a tube filled with indocyanine green immersed in water and placed under chicken breast tissue, our laser system could also be used for the simultaneous PA and ultrasound (US) dual-modality imaging of blood vessels lying beneath the skin of a human middle finger. We used a commercially available US machine for the PA and US dual-modality imaging.

Backward wave optical parametric oscillation in a waveguide

“…It would reduce the pump pulse energy and peak power at threshold to about 15 nJ and 70 W, respectively. That would put the BWOPO waveguide technology in the realm of mode-locked laser oscillators as well as compact narrowband gain-switched fiber and solidstate lasers [34,35]. The unique spectral features of counter-propagating down-conversion should allow for the generation of high-purity and narrowband single photons in a ready for integration package, offering exciting prospects in applications such as photoacoustic spectroscopy, molecular spectroscopy as well as in quantum technologies .…”

Platform for quantitative multiscale imaging of tissue composition

“…This system was built to be modular so that more imaging modalities could be added to provide complementary contrasts and additional imaging scales. For example, the system has the components to perform photoacoustic imaging using the Titanium:Sapphire laser and the US transducer [66], which would give contrast for tissue components including hemoglobin, melanin, lipids, and water [9]. In addition, the US system could run with different transducers, allowing either higher resolution with higher frequency transducers, or new imaging modes such as shear wave imaging [67].…”

Photoacoustic imaging probe for detecting lymph nodes and spreading of cancer at various depths

“…We used a compact gain-switched Ti: sapphire laser pumped by a frequency-doubled Nd:YAG pulse laser (Ultra, Quantel Laser) operated at an output energy of 37 mJ with a 532-nm wavelength, 10-Hz repetition rate, and 11-ns pulse duration. 17 The pulsed laser was coupled into a connectorized multimode optical fiber cable (#HP-2020-10A3CH-040E, Fiberguide industries) with a 1000-μm core and 0.22 numerical aperture. The optical fiber cable was connected at the PAI probe as shown in Fig.…”