This PDF file contains the front matter associated with SPIE Proceedings Volume 12746, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Traditional endoscopes relay images through a bundle of optical fibres, one fibre for each pixel in the image. However, in principle even one of these fibres carries enough spatial modes to relay an entire image, but modal dispersion means the resulting image is scrambled. As a solution to this, various groups world-wide are using aberration correction techniques to create a scanning spot at the exit of the fibre to raster-scan an object, the backscattered light from this spot is measured to give an image. The current limitation is that the aberration correction depends upon the bend of the fibre, meaning that once imaging is achieved, the fibre cannot be moved. We will present our latest work on high-speed aberration correction and choice of fibre, demonstrating that bends of several 10s of degrees can be achieved without degradation in image quality. Our work opens the route to fibre-based imaging systems being deployed in dynamic situations for various inspection and healthcare applications.

Subwavelength arrays of quantum emitters feature unique and largely design-able nonlinear optical properties. As a generic example we study a sub-wavelength sized ring of identical dipoles with an extra identical absorbing emitter at the center. For a 9-ring one finds the most efficient antenna configuration to direct single incoming photons to the center without re-emission. Interestingly, for very tiny structures sizes below a tenth of a wavelength, a full quantum description predicts an even larger absorption enhancement than a mean field model using a classical dipole approximation. We identify the origin of the enhancement in the appearance of a collective dark state with dominant center occupation. By special design of the center absorber one thus can harness the same efficiency enhancement also at different wavelengths and for other geometric structures. On the one hand this idea could be the basis of a new generation of highly efficient and selective nano antennas, while on the other hand, it could be an important piece towards understanding the surprising efficiency of natural light harvesting molecules. Adding gain via active dipoles in such nano ring systems allows to design minimalist laser like classical light sources. In the nonlinear operating regime at stronger pump fields these systems transform to non-classical light sources with tailor-able spatio-temporal emission upon coherent illumination.

We demonstrate that gradual interfaces between lossy conductive media support propagation of a novel kind of surface electromagnetic wave, which is different from the more well-known surface plasmon polaritons. Potential applications of these novel surface waves to monitor water surface and the seawater-ice interface, as well as other environmental sensing applications in the RF and optical domain are discussed.

Super-resolution, structured illumination microscopy (SIM) is an ideal modality for imaging live cells due to its relatively high speed and low photon-induced damage to the cells. SIM consists of two generic components: (i) sample illumination by a sinusoidal pattern and (ii) computational reconstruction of a super-resolution image. The rate-limiting step in observing a super-resolution image in SIM is the reconstruction speed of the algorithm required to form a single image from as many as nine raw images. These reconstruction algorithms impose a significant computing burden due to a complex workflow and a large number of calculations requiring 10-300 seconds per image nullifying real-time imaging. In this mini-review, we show how the approaches we developed to improve Hessian-SIM algorithm reconstruction speed can be used to improve other SIM image reconstruction algorithms. These approaches, which included code improvement, conversion to the GPU environment, and use of cost-effective high-performance computers produce up to 500-fold increases in image reconstruction speed.

Optomechanical systems have come to the fore in the last two decades. This field focuses upon the interaction of light with matter. It can lead to new approaches for precision measurement and the study of quantum physics. Light may both probe the system and mediate a reduction in energy of the system (cooling). In this domain, levitated optomechanics has emerged as an important direction which holds a mesoscopic particle in isolation from its surroundings. This reduces dissipation. This may be performed using optical trapping, though levitation through electrostatic or other means offer interesting alternative. Exploiting the rotational degree of freedom by spinning the trapped particle adds further value. By drawing on some of the key international work, including that from my group, I will review some of particular advances made in such rotational levitated optomechanics using birefringent particles.

Precision Agriculture stands out as one of the most promising areas for the development of new technologies around the world. Some advances from this area include the mapping of productivity areas and the development of sensors for climate and soil analysis, improving the smart use of resources during crop management and helping farmers during the decision-making stages. Among the problems of modern agriculture, the intensive and non-localized use of herbicides causes environmental issues, contributes to elevated costs in farmers’ budgets and results in applications of chemical substances in non-target organisms. Although there are many selective herbicide spraying systems available for use, the majority working principle is based upon chlorophyll detectors, thus not being able to distinguish crop plants from weeds with high accuracy in crop’s post-emergence herbicide applications (“green-on-green” application). The main objective of this study is to develop a multispectral camera system for in-crop weed recognition using Computer Vision techniques. The system was built with four monochromatic CMOS sensor cameras with monochromatic wavelength bandpass filters (green, red, near infrared and infrared) and a RGB camera. Soybean and weed plants images were captured in a controlled environment using an automated v-slot rail system to simulate the movement of a spray tractor in the field. Infrared images presented higher precision (90.5%) and recall (89.3%) values compared to the other monochromatic bands, followed by RGB (87.0% and 86.1%, respectively) and near infrared images (83.6% and 87.9%), suggesting that infrared wavelengths plays an important role in plant detection and classification. Our results state that the combination of Computer Vision and multispectral images of plants is a more efficient approach for targeting weeds among crop plants for post-emergence herbicide applications.

Objective measurements of the morphology and dynamics of label-free cells and tissues can be achieved by quantitative phase with low phototoxicity and no photobleaching. Modern quantitative optical imaging possesses a huge information capacity. The morphology and dynamics of label-free tissues can be exploited by sample-induced changes in the optical field from quantitative phase imaging. Its sensitivity to subtle changes in the optical field makes the reconstructed phase susceptible to phase aberrations. We present aberration-free high-bandwidth holographic microscopy which exploits high-throughput label-free quantitative phase imaging. Firstly, a full-bandwidth holographic reconstruction is retrieved from interferograms by establishing a holographic multiplexing framework. Based on the analyticity of band-limited signal under a diffraction-limited system, the maximum space bandwidth utilization limit in a single multiplexing hologram is increased to the maximum sensor limit. Secondly, A variable sparse splitting framework on quantitative phase aberration extraction is imported based on the alternating direction aberration-free method. By formulating the aberration extraction as a convex quadratic problem, the background phase aberration can be fast and directly decomposed with the specific complete basis functions such as Zernike or standard polynomials. Faithful high throughput phase reconstruction can be obtained by eliminating global background aberration. It opens a new route to multiplexing quantitative optical imaging and helps to improve the performance of constraint-free modern optical microscopes in various spectral regimes.