Photorefractive acousto-optic imaging in thick scattering media at 790 nm with a Sn_2P_2S_6:Te crystal

Abstract

Acousto-optic imaging is based on ultrasound modulation of multiply scattered light in thick media. We experimentally demonstrate the possibility to perform a self-adaptive wavefront holographic detection at 790nm, within the optical therapeutic window where absorption of biological tissues is minimized. A high-gain Te-doped Sn(2)P(2)S(6) crystal is used for this purpose. Optical absorbing objects embedded within a thick scattering phantom are imaged by use of pulsed ultrasound to get a dynamic millimetric axial resolution. Our technique represents an interesting approach for breast cancer detection.

Ultrasound-modulated optical tomography at new depth

“…Transition to 1064 nm optical wavelength also allows us to further increase, if needed for deeper imaging and/or better SNR, the signal beam incident intensity without violating the safety limit (1 W∕cm 2 ) at 1064 nm. 11 Moreover, photorefractive crystals operating at this wavelength, for example GaAs 31 and Sn 2 P 2 S 6 ∶Te, 16 can have a response time less than 1 ms under a 1 W∕cm 2 illumination, potentially accommodating the speckle decorrelation induced by physiological motion in vivo. Therefore, to further enhance the system toward in vivo applications such as the diagnosis of early stage breast cancer, it will be upgraded to 1064 nm in the near future.…”

“…To enhance the signal detection sensitivity, various detection schemes have been developed, such as parallel detection based on a CCD camera, 12,13 interferometry without 14 or with photorefractive crystals (PRC), 6,7,15,16 and Fabry-Perot interferometry 8,17 or spectral hole burning-based spectral filtering detection. 18 These detection schemes have been employed for conventional optical contrast imaging, multi-wavelength imaging, 19 mechanical contrast imaging, 20,21 quantitative measurement of optical properties, 15,22 real-time monitoring of thermal necrosis, 23 as well as assisting optical near-infrared spectroscopy 24 and diffuse optical tomography.…”

Lock-in camera based heterodyne holography for ultrasound-modulated optical tomography inside dynamic scattering media

“…[20][21][22] Recently, Ramaz's group demonstrated the promise of Sn 2 P 2 S 6 :Te and Nd:YVO 4 crystals for UOT, because of their short response times. 23,24 However, these crystals usually work in a narrow range of wavelengths. The third type of method uses a pixel array, i.e., a camera, to detect the tagged light.…”

Optical phase conjugation in Nd:YVO_4 for acousto-optic detection in scattering media

“…Usually, these non-linear interactions are performed using photo-refractive crystals such as SPS [2], BSO [3] or GaAs [4] or, in the case of phase conjugation (PC), spatial light modulators (SLM) [5] can also be used. Those methods have proven to be efficient and gives good results on static samples.…”