All-optical optoacoustic microscopy based on probe beam deflection technique

Abstract

Optoacoustic (OA) microscopy using an all-optical system based on the probe beam deflection technique (PBDT) for detection of laser-induced acoustic signals was investigated as an alternative to conventional piezoelectric transducers. PBDT provides a number of advantages for OA microscopy including (i) efficient coupling of laser excitation energy to the samples being imaged through the probing laser beam, (ii) undistorted coupling of acoustic waves to the detector without the need for separation of the optical and acoustic paths, (iii) high sensitivity and (iv) ultrawide bandwidth. Because of the unimpeded optical path in PBDT, diffraction-limited lateral resolution can be readily achieved. The sensitivity of the current PBDT sensor of 22 μV/Pa and its noise equivalent pressure (NEP) of 11.4 Pa are comparable with these parameters of the optical micro-ring resonator and commercial piezoelectric ultrasonic transducers. Benefits of the present prototype OA microscope were demonstrated by successfully resolving micron-size details in histological sections of cardiac muscle.

Looking at sound: optoacoustics with all-optical ultrasound detection

“…Instead of detecting ultrasound based on changes in the intensity of a probe beam, which requires an interface between two media of different RI, ultrasound can additionally be detected based on the deflection of the probe beam crossing the acoustic field (Fig. 1b ) 30 , 31 . The acoustic waves alter the RI of the medium and interact with the electric field of the probe laser beam, deflecting it in proportion to the pressure gradient of the acoustic wave.…”

Advanced optoacoustic methods for multiscale imaging of in vivo dynamics

“…However, an epi-illumination approach is generally preferred as it produces less acoustic distortions, particularly for thick samples. To date, multiple epi-illumination-based systems have been suggested [27–31]. The lateral resolution can further be enhanced with super-resolution approaches based on several non-linear mechanisms [32–37].…”

Infrared spectra of micro-structured samples with microPhotoacoustic spectroscopy and synchrotron radiation

“…Several other detection methods are also utilised, including cantilever deflection caused by the pressure wave, the deflection of a probe laser beam by the pressure and density gradients in proximity to the sample surface, the shift in peak resonance of a micro-ring resonator, or sample thickness modulation as detected by a Fabry-Perot interferometer. [2][3][4] The intensity of the PA signal is a function of the absorption coefficient. Under appropriate conditions, the wavelength dependence of the PA intensity is equivalent to the absorption spectrum of the sample, closely resembling the spectrum derived from a conventional transmission measurement.…”