Solid-state single-photon sources: recent advances for novel quantum materials

In this review, we describe the current landscape of emergent quantum materials for quantum photonic applications. We focus on three specific solid-state platforms: single emitters in monolayers of transition metal dichalcogenides, defects in hexagonal boron nitride, and colloidal quantum dots in perovskites. These platforms share a unique technological accessibility, enabling the rapid implementation of testbed quantum applications, all while being on the verge of becoming technologically mature enough for a first generation of real-world quantum applications. The review begins with a comprehensive overview of the current state-of-the-art for relevant single-photon sources in the solid-state, introducing the most important performance criteria and experimental characterization techniques along the way. We then benchmark progress for each of the three novel materials against more established (yet complex) platforms, highlighting performance, material-specific advantages, and giving an outlook on quantum applications. This review will thus provide the reader with a snapshot on latest developments in the fast-paced field of emergent single-photon sources in the solid-state, including all the required concepts and experiments relevant to this technology.Comment: 35 pages, 8 figures, review pape

A Multiple Height Transfer Interferometric Technique and Its Applications

Absolute distance interferometric metrology is one of the most useful techniques for dimensional measurements. Without movement, measurements can be made without ambiguity, by using either one or several synthetic wavelengths. Synthetic wavelengths result from the beating of two or more wavelengths in multiple-wavelength interferometry (MWI), or a wavelength scan in wavelength-scanning interferometry (WSI). However, conventional MWI requires accurate wavelength information for a large measurement range, while WSI is limited by a mode-hop-free laser tuning range. A multiple height-transfer interferometric technique (MHTIT) is proposed based on concepts from both MWI and WSI. Using multiple accurately calibrated reference heights, this technique preserves the capabilities to determine the optical path difference (OPD) unambiguously without accurate wavelength information, and yet does not require the laser to be continuously tuned. A multiple reference height calibration artifact is proposed and installed in a holographic measuring system. Applying the MHTIT with the calibration artifact, the metrology system measurement range is increased from 5 mm to over 100 mm without accurate wavelength information. Three-dimensional images of discontinuous surface heights obtained from a variety of automotive parts demonstrate the applicability of the MHTIT in workshop environments. We present an uncertainty analysis, analyzing the primary sources of uncertainties that limit the performance of the MHTIT and discuss how errors can be minimized. The measurement uncertainty is experimentally demonstrated to be about 0.3 µm for 50.8 mm at a confidence level of 95% for two discontinuous surfaces under lab environments. Another application of the MHTIT for measuring the thickness of a transparent plate is investigated. WSI can measure the thickness of transparent plates by differentiating OPDs from multiple surface interferences in the Fourier domain. However, nonlinear laser tuning deviates the measurement result from the correct value. We propose a wavelength-stepping method for application to thickness measurements of transparent plates. Systematic errors caused by nonlinearity in laser source stepping are reduced with accurate synthetic wavelengths measured by the MHTIT. A 10-µm step height standard etched on a 25 mm × 25 mm × 3 mm quartz block is measured to demonstrate the proposed method with sub-micron accuracy.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91426/1/haoyu_1.pd

Multiplexed optical fibre sensors for civil engineering applications

Fibre-optic sensors have been the focus of a lot of research, but their associated high cost has stifled their transferral from the laboratory to real world applications. This thesis addresses the issue of multiplexing, a technology that would lower the cost per unit sensor of a sensor system dramatically. An overview of the current state of research of, and the principles behind, multiplexed sensor networks is given. A new scheme of multiplexing, designated W*DM, is developed and implemented for a fibre Bragg grating (FBG) optical fibre sensor network. Using harmonic analysis, multiplexing is performed in the domain dual to that of the wavelength domain of a sensor. This scheme for multiplexing is compatible with the most commonly used existing schemes of WDM and TDM and thus offers an expansion over, and a resultant cost decrease from, the sensor systems currently in use. This research covered a theoretical development of the scheme, a proof of principle, simulated and experimental analysis of the performance of the multiplexed system, investigation into sensor design requirements and related issues, fabrication of the sensors according to the requirements of the scheme and the successful multiplexing of eight devices (thus offering an eightfold increase over current network capacities) using this scheme. Extensions of this scheme to other fibre sensors such as Long Period Gratings (LPGs) and blazed gratings were also investigated. Two LPGs having a moiré structure were successfully multiplexed and it was shown that a blazed Fabry Perot grating could be used as a tuneable dual strain/refractive index sensor. In performing these tests, it was discovered that moiré LPGs exhibited a unique thermal switching behaviour, hereto unseen. Finally the application of fibre sensors to the civil engineering field was investigated. The skill of embedding optical fibre in concrete was painstakingly developed and the thermal properties of concrete were investigated using these sensors. Field tests for the structural health monitoring of a road bridge made from a novel concrete material were performed. The phenomenon of shrinkage, creep and cracking in concrete was investigated showing the potential for optical fibre sensors to be used as a viable research tool for the civil engineer

Interfaces of resistance in the image-machine of control

My creative practice addresses two research questions: how does ubiquitous computation affect the visual operations of the contemporary control society and what does this mean for the use of visual media in contesting such control? Through photographic and video work in digital formats, I explore the movements and arrests of informatic flows that constitute the operation of control, and the potential for resistance that may be felt in the turbulence of the interface, as a dynamic threshold where such flows meet. In this turn to the interface, I theorise the impacts of computationality on the loss of the image as a stable site of representational resistance, with the unsettling of perspectival representation in the topology of informational space and the ambiguity of a digital visuality whose software hides as it shows. When brought together with recent work on the de-materialisation wrought by informational Capital, the digital image comes to be seen as an instantiation of anxiety about the abstracted nature of power that increasingly operates as control. It is less to the digital image itself, but rather to the circulations and patternings of data expressed as light on the screen, that we must attend if we are to confront the digital visuality of control. The ‘image-machine of control’ is the infrastructure that modulates these data circulations and patternings through inciting the making, sharing and watching of images. Drawing on affect theory, I emphasise the role that affects of insecurity, at the level of the dividuated subject and the abstracted socius, play in inciting an interactivity with the screen on which the State and Corporation alike rely for their accumulation and circulation of data. The digital-visual interface, being the encounter with the screen, becomes a sitemoment to explore its dynamic boundary condition, whose turbulence of data flows may open up ‘lines of flight’ from the striated grid of control. These lines of flight help us see beyond the workings of the faciality system, and the subject-object relations of the gaze. Specificity of positioning in scopic regimes of control still matters, but posthumanist theorising suggests that such positioning be understood as vector and not point, whose movements we need to stay in touch with. Using digital photography to open up the everyday practice of image-making to its potential to disrupt the informatic flows of control, my first photographic work, medium specific, makes use of photomontage to look at the topology of informational space through its ‘folds’, as a first experiment in disrupting the tempo of the image-machine’s visual incitements through a ‘pleating’ of its data. I use haptic photography in the pieces figure ground, surface gaze and touch light to stay in touch with the smooth space of the interface as a time-space of contingency, potentially resistant to the gridded striations of control. My exploration of the contingency of the interface continues with two video works, look screen and moving still, which address its vibrational ontology. I put the concept of the vibrational interface to use in confronting the rhythms of control deployed by the image-machine. Being a rhythm of not only circulation but also capture, not merely movement but also arrest, I suggest that understanding the ontology of the interface in terms of its vibrational forces is useful for disrupting, through its moving stillness, the rhythm of flow and stasis on which control depends. Both videos use visual and sonic vibrations to set up counter-rhythms and oscillations, whose trembling may release energies for change

Light-sheet microscopy: a tutorial

This paper is intended to give a comprehensive review of light-sheet (LS) microscopy from an optics perspective. As such, emphasis is placed on the advantages that LS microscope configurations present, given the degree of freedom gained by uncoupling the excitation and detection arms. The new imaging properties are first highlighted in terms of optical parameters and how these have enabled several biomedical applications. Then, the basics are presented for understanding how a LS microscope works. This is followed by a presentation of a tutorial for LS microscope designs, each working at different resolutions and for different applications. Then, based on a numerical Fourier analysis and given the multiple possibilities for generating the LS in the microscope (using Gaussian, Bessel, and Airy beams in the linear and nonlinear regimes), a systematic comparison of their optical performance is presented. Finally, based on advances in optics and photonics, the novel optical implementations possible in a LS microscope are highlighted.Peer ReviewedPostprint (published version

New optical techniques and hardware for studying live cell dynamics

This thesis was previously held under moratorium from 12/02/2019 to 21/05/2021.Fluorescence optical microscopy has become an integral technique in the life sciences and has opened the door to investigating live biological specimens non-invasively at sub-cellular spatial resolutions with high specificity and temporal resolutions. One of the limiting factors of optical microscopy is that the spatial resolution is dictated by the diffraction limit of light.;This work shows the first use of LEDs to carry out widefield axial super-resolution standing wave microscopy with high temporal resolution. The technique was used to image red blood cell membrane dynamics in real time with no increase in photobleaching or toxicity rates compared to standard widefield imaging. This work also presents 3D computational reconstructions of the data allowing for easier visualisation and the possibility of carrying out further quantitative analysis.;Following on from Chapter 2, is an investigation into the development and application of multi-wavelength standing wave microscopy on live specimens in both emission and excitation modalities. These techniques are henceforth referred to in this thesis as TartanSW. This investigation found that using multiple excitation wavelengths allowed for a reduction in the nodal contribution of the images resulting in obtaining 32.3 % more spatial information about the structure of the specimen. It is also shown that by taking the difference images between each excitation channel the standing wave antinodal planes could be reduced in thickness enabling axial resolutions on the order of 55 nm when imaging live cell experiments.;The multi-emission technique was shown that it could be applied to be applied to imaging biological specimens using both widefield and confocal microscopy. However, the widefield data was not in line with the expected theoretical structure. There is the possibility of using plane ordering though to infer the directionality of a specimen structure and extract height maps though further work to develop computational tools to enable this will have to be implemented.;Finally, this thesis describes the work carried out making use of a new high-brightness 340 nm LED to develop a fast switching 340/380 nm illuminator and demonstrate its application for ratiometric Fura-2 Ca2+ imaging of live cell specimens with sub-5 nM precision that supports full frame video-rate temporal resolutions.Fluorescence optical microscopy has become an integral technique in the life sciences and has opened the door to investigating live biological specimens non-invasively at sub-cellular spatial resolutions with high specificity and temporal resolutions. One of the limiting factors of optical microscopy is that the spatial resolution is dictated by the diffraction limit of light.;This work shows the first use of LEDs to carry out widefield axial super-resolution standing wave microscopy with high temporal resolution. The technique was used to image red blood cell membrane dynamics in real time with no increase in photobleaching or toxicity rates compared to standard widefield imaging. This work also presents 3D computational reconstructions of the data allowing for easier visualisation and the possibility of carrying out further quantitative analysis.;Following on from Chapter 2, is an investigation into the development and application of multi-wavelength standing wave microscopy on live specimens in both emission and excitation modalities. These techniques are henceforth referred to in this thesis as TartanSW. This investigation found that using multiple excitation wavelengths allowed for a reduction in the nodal contribution of the images resulting in obtaining 32.3 % more spatial information about the structure of the specimen. It is also shown that by taking the difference images between each excitation channel the standing wave antinodal planes could be reduced in thickness enabling axial resolutions on the order of 55 nm when imaging live cell experiments.;The multi-emission technique was shown that it could be applied to be applied to imaging biological specimens using both widefield and confocal microscopy. However, the widefield data was not in line with the expected theoretical structure. There is the possibility of using plane ordering though to infer the directionality of a specimen structure and extract height maps though further work to develop computational tools to enable this will have to be implemented.;Finally, this thesis describes the work carried out making use of a new high-brightness 340 nm LED to develop a fast switching 340/380 nm illuminator and demonstrate its application for ratiometric Fura-2 Ca2+ imaging of live cell specimens with sub-5 nM precision that supports full frame video-rate temporal resolutions