Phonon imaging in 3D with a fibre probe

Abstract

We show for the first time that a single ultrasonic imaging fibre is capable of simultaneously accessing 3D spatial information and mechanical properties from microscopic objects. The novel measurement system consists of two ultrafast lasers that excite and detect high-frequency ultrasound from a nano-transducer that was fabricated onto the tip of a single-mode optical fibre. A signal processing technique was also developed to extract nanometric in-depth spatial measurements from GHz frequency acoustic waves, while still allowing Brillouin spectroscopy in the frequency domain. Label-free and non-contact imaging performance was demonstrated on various polymer microstructures. This singular device is equipped with optical lateral resolution, 2.5 μm, and a depth-profiling precision of 45 nm provided by acoustics. The endoscopic potential for this device is exhibited by extrapolating the single fibre to tens of thousands of fibres in an imaging bundle. Such a device catalyses future phonon endomicroscopy technology that brings the prospect of label-free in vivo histology within reach.

Brillouin Interaction between Two Optical Modes Selectively Excited in Weakly Guiding Multimode Optical Fibers

“…High-frequency real-time ultrasound imaging [ 14 ] can provide exquisite visualizations of tissue to guide minimally invasive procedures. With this device, broad-bandwidth ultrasound generation is achieved through the photoacoustic excitation of a special composite coating on the distal end of the multimode optical fiber by a pulsed laser [ 15 ]. Although most commercial sensing systems rely on measurements of the transmitted or reflected fundamental mode of single-mode optical fibers, more recent developments have focused on multimodal architectures that considerably widen the sensing modalities, especially in the chemical and biological fields [ 16 , 17 , 18 , 19 , 20 ].…”

Dispersive coherent Brillouin scattering spectroscopy

“…An acousto-optical technique can meet this demand: Brillouin scattering spectroscopy interrogates material’s mechanical properties from an inelastic light scattering by a phonon, referred to as Brillouin light scattering [8] . It non-invasively reads out the viscoelastic properties of small-scale materials with high spatial resolution [9] , [10] , [11] . Brillouin scattering spectroscopy has various applications, including phonon physics studies [12] , [13] , [14] and characterization of solids [15] , [16] , [17] , liquids [18] , [19] , [20] , and biological samples [21] , [22] , [23] , [24] , [25] , [26] , [27] .…”

Directly and instantly seeing through random diffusers by self-imaging in scattering speckles

“…In the past decades, there have been increasing interests in coherent and incoherent imaging through scattering media. To enable imaging through this challenging condition, it is an emerging topic to extract spatial information through scattering by employing the active control of light with the aid of prior knowledge of objects or media, or combined with post-imaging recovery processes, i.e., computational imaging of hidden objects [4][5][6][7][8][9][10][11][12]. Many powerful computational imaging approaches have been reported, utilizing interference (such as holography [13]) and interference-less methods [14], transmission matrix [15,16], active wavefront shaping techniques [17,18] for precise light control and smart computational imaging through scattering media [19][20][21][22][23][24].…”

“…However, all aforementioned imaging technologies through scattering media require sophisticated optical setups (e.g. [4][5][6][7][8][9][10][11][12][13][14][15][16]) or time-consuming post computational reconstruction with carefully adjusted parameters for the pre-processing of the speckle and/or the autocorrelation (e.g. ).…”