ABSTRACT
Photo-acoustic imaging, also known as opto-acoustic imaging, has become a widely popular modality for biomedical applications. This hybrid technique possesses the advantages of high optical contrast and high ultrasonic resolution. Due to the distinct optical absorption properties of tissue compartments and main chromophores, photo-acoustics is able to non-invasively observe structural and functional variations within biological tissues including oxygenation and deoxygenation, blood vessels and spatial melanin distribution. The detection of acoustic waves produced by a pulsed laser source yields a high scaling range, from organ level photo-acoustic tomography to sub-cellular or even molecular imaging. This review discusses significant novel technical solutions utilising photo-acoustics and their applications in the fields of biomedicine and life sciences.
ABSTRACT
We present a polymer fibre Bragg grating sensor and its sensitivity to gamma radiation by observing the reflected spectral profile. The Bragg grating is femtosecond inscribed within a perfluorinated CYTOP fibre and the alteration of the Bragg wavelength corresponds to the total radiation dose received. Over a total dose of 41 k Gy, the fibre demonstrates a sensitivity of - 26.2 p m / k Gy and a resolution of 40 Gy. Under active consideration for the instrumentation of nuclear waste repositories, this study gives a better understanding of the effects of gamma radiation upon Bragg gratings in CYTOP fibres.
ABSTRACT
We demonstrate a largely tunable dispersion fiber Bragg grating (FBG) inscribed in a microstructured polymer optical fiber (mPOF). The bandwidth of the chirped FBG (CFBG) was achieved from 0.11 to 4.86 nm, which corresponds to a tunable dispersion range from 513.6 to 11.15 ps/nm. Furthermore, thermal sensitivity is used to compensate for the wavelength shift due to the applied strain. These results demonstrate that a CFBG in a POF is a promising technology for future optical systems.
ABSTRACT
We obtained chirped gratings by performing hot water gradient thermal annealing of uniform poly (methylmethacrylate) (PMMA) microstructured polymer optical fiber Bragg gratings (POFBGs). The proposed method's simplicity is one of its main advantages because no special phase mask or additional etching are needed. It not only enables easy control tuning of the central wavelength and chirp characteristics, but it also leads to obtain flexible grating response, compared with tapered chirped POFBGs. Therefore, a flexible and low-cost chirped POFBG devices fabrication technique has been presented by using a single uniform phase mask.
