The interrogation of polarisation state of light is a developing technique in biomedical imaging. As polarised light interacts with structural changes in tissue, it has seen use in differentiation between (pre)cancerous and noncancerous tissue, for example. In biomedical imaging rapid diagnostics using minimally invasive techniques is desirable. Endoscopy is already very prevalent in medicine and therefore miniaturisation of polarimetry systems onto endoscopic platforms is a natural development. Flexibility of such a device allows navigation to more complicated parts of the body. All polarimetric systems consist of a polarisation state generator (PSG) and a polarisation state analyser (PSA) which need to be integrated into such a system. A rigid endoscope capable of imaging a full 4×4 Mueller matrix has been developed by Qi et al. This endoscope achieves the polarisation state generation a rigid rotating sheath. Partial polarimetric endoscopy which captures a 3×3 Mueller matrix has also been demonstrated and is easier to achieve since it does not require quarter wave plates in the generator or analyser. Clancy et al and Qi et al both demonstrate a rigid polarimetric endoscopy using a stereo endoscope and a standard rigid endoscopy, respectively. Integration of polarisation state analyser and generator into the tip has been demonstrated using complex mechanical designs. However questions have been raised regarding the electromagnetic compatibility of such a system due to the presence of motors in the tip. Forward et al present a flexible 3×3 fibre based probe that uses diced polarisers orientated at the horizontal, vertical, and -45 degree positions to generate and acquire the necessary polarisation states. This work presents an imaging probe designed to enable in-vivo polarimetry measurements using a micro camera on the tip as a sensor. A 3×3 Mueller matrix image of crossed linear polarisers, captured using a micro camera is demonstrated. This device demonstrates the potential of micro camera sensors in providing 2-dimensional polarimetry data in a flexible endoscopic system. For a device to be used in a clinical setting it needs to be capable of providing data rapidly when it is needed, as well as being navigable to the target location. A fibre optically illuminated endoscope with micro-camera sensor allows for rapid switching of illumination fibres using backend illumination systems as well as rapid acquisition of data. Optical fibres enable the probe to be rigid or flexible depending on application, and the camera at the tip ensures consistent image quality regardless of application area. An idealised system and its potential future of polarimetry in translational biophotonic devices is also discussed.
The biophotonics box enables multidisciplinary/interdisciplinary and self-paced learning with at-home experiments using low-resource components. Experiments can increase the interest of students in STEM subjects by emphasizing the real-life applications in biology and medicine.
Quantum Key Distribution (QKD) directly exploits the quantum phenomenon of entanglement to allow the secure sharing of a cryptographic key for information encoding. The current generation of QKD devices typically operate over dedicated and expensive private ‘dark fiber’ networks, where they are limited in transmission range to 200-300km due to the lack of quantum repeaters. This paper is concerned with an alternative approach that can lift this range limit by exploiting QKD over free-space links between satellites. Typically, commercial QKD systems rely on phase encoding of information on single photons, and more recently on continuously variable schemes with more powerful lasers. However, these protocols are not suitable for communications through atmosphere. On the other hand, QKD by polarization-entanglement holds great promise for satellite-based QKD encoded communications links if the entangledphoton source can be packaged in a compact, robust and commercially-viable form. This paper will describe the development and packaging of an entangled-photon source utilizing space-qualified telecoms packaging techniques, resulting in a compact device that targets satellite deployment. The key design choices that impact performance in a space environment will be discussed and the results of device characterization in the laboratory environment will be shared.
A dual modality fibre sensing system for simultaneous monitoring of temperature and acoustic disturbances in power cables is demonstrated. The system combines Raman OTDR (Optical Time-Domain Reflectometry) and Rayleigh phase- OTDR and is based on a single shared laser source. The performance of the system is demonstrated with absolute temperature measurements in heated fibre sections and detection of echoes from disturbance events. To the best of our knowledge, this is the first single-source simultaneous temperature and disturbance sensing in single-mode fibre. Finally, it is demonstrated that localised temperature variations and acoustic disturbances, such as cable strumming and strike, can be detected in an onshore 30 kV power cable.
This paper will present developments in narrow-linewidth semiconductor-disk-laser systems using novel frequencystabilisation schemes for reduced sensitivity to mechanical vibrations, a critical requirement for mobile applications. Narrow-linewidth single-frequency lasers are required for a range of applications including metrology and highresolution spectroscopy. Stabilisation of the laser was achieved using a monolithic fibre-optic ring resonator with free spectral range of 181 MHz and finesse of 52 to act as passive reference cavity for the laser. Such a cavity can operate over a broad wavelength range and is immune to a wide band of vibrational frequency noise due to its monolithic implementation. The frequency noise of the locked system has been measured and compared to typical Fabry-Perotlocked lasers using vibration equipment to simulate harsh environments, and analysed here. Locked linewidths of < 40 kHz have been achieved. These developments offer a portable, narrow-linewidth laser system for harsh environments that can be flexibly designed for a range of applications.
Commercially available supercontinuum sources continue to experience a strong growth in a wide range of industrial and scientific applications. In addition, there is a significant research effort focused on extending the wavelength coverage both towards UV and Mid-IR. Broadband sources covering these wavelength regions have received significant attention from potential users, as there is a wide array of applications for which there are few suitable alternative light sources – if any. Our developments in the field of Mid-IR supercontinuum sources have been based on radical approaches; such as soft glasses and novel pumping schemes, whereas shifting the spectrum further towards the UV has been based on sophisticated microstructure fiber designs. Here we present our latest developments in tailoring the power and spectral coverage of spatially coherent broadband supercontinuum sources.
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