Studies In Mesoscopics And Quantum Microscopies

This thesis begins with a foundational section on quantum optics. The single-photon detectors used in the first chapter were obtained through the Advanced Laboratory Physics Association (ALPhA), which brokered reduced cost for educational use, and the aim of the single-photon work presented in Chapter 1 is to develop modules for use in Illinois Wesleyan\u27s instructional labs beyond the first year of university. Along with the American Association of Physics Teachers, ALPhA encourages capstone-level work, such as Chapter 1 of this honors thesis, which is explicitly designed to play the role of passing on, to a next generation of physics majors, materials that can play a central role in their curriculum. Thus, although such work had previously been done at other institutions, the value added by this work has to do with the impact upon the local curriculum, and the utility of the collation o of these materials into one single, easily accessible form. Beyond its first chapter, this thesis extends into my research projects, each of which, in the long term, carries a motivation that connects back to questions raised in the studies described in Chapter 1. While the first chapter describes ways in which we can experimentally study the ``spin\u27\u27 polarization state of a single photon, the second deals extends the discussion of how information may be encoded into the angular momentum of light, and some of its potential long-term consequences, e.g., for experiments involving optical traps that may someday test for the (controversial) hypothesized existence of a boundary between the microscopic (quantum) and macroscopic (classical) domains. Here, too, the work presented builds upon a body of work in the recent research literature. The final chapter deals with the creation of meso-scale systems for use in advanced optical traps studies. Each of these last two chapters points towards opportunities in physics research that are tentative in nature and, as such, constitute research that is very much aspirational. The citations provided, while not exhaustive, point both towards some of the more useful resources discovered during this work, and to some ongoing controversies in the field. At the same time, these chapters also aim to delineate concrete, specific steps that we have taken, which we believe are of immediate interest in their own rights

Mechanical Evidence of the Orbital Angular Momentum to Energy Ratio of Vortex Beams

We measure, in a single experiment, both the radiation pressure and the torque due to a wide variety of propagating acoustic vortex beams. The results validate, for the first time directly, the theoretically predicted ratio of the orbital angular momentum to linear momentum in a propagating beam. We experimentally determine this ratio using simultaneous measurements of both the levitation force and the torque on an acoustic absorber exerted by a broad range of helical ultrasonic beams produced by a 1000-element matrix transducer array. In general, beams with helical phase fronts have been shown to contain orbital angular momentum as the result of the azimuthal component of the Poynting vector around the propagation axis. Theory predicts that for both optical and acoustic helical beams the ratio of the angular momentum current of the beam to the power should be given by the ratio of the beam’s topological charge to its angular frequency. This direct experimental observation that the ratio of the torque to power does convincingly match the expected value (given by the topological charge to angular frequency ratio of the beam) is a fundamental result

Experimental implementation of wavefront sensorless real-time adaptive optics aberration correction control loop with a neural network

Recently, deep neural network (DNN) based adaptive optics systems were proposed to address the issue of latency in existing wavefront sensorless (WFS-less) aberration correction techniques. Intensity images alone are sufficient for the DNN model to compute the necessary wavefront correction, removing the need for iterative processes and allowing practical real-time aberration correction to be implemented. Specifically, we generate the desired aberration correction phase profiles utilizing a DNN based system that outputs a set of coefficients for 27 terms of Zernike polynomials. We present an experimental realization of this technique using a spatial light modulator (SLM) on real physical turbulence-induced aberration. We report an aberration correction rate of 20 frames per second in this laboratory setting, accelerated by parallelization on a graphics processing unit. There are a number of issues associated with the practical implementation of such techniques, which we highlight and address in this paper

Optical Cloaking by Aberation Correction

Light incident on a material is scattered and then continues its propagation in seemingly random directions. If one can force light to pass through a material and not scatter, however, then one could “see” through the material. This scattering of light can be described as aberration within the light. A technique used for “Aberration Correction” is adding phase-shifts to regions of light allowing for all wave fronts of light to interfere in a constructive manner. This is accomplished in the use of a Spatial Light Modulator (SLM). The SLM, an array of linearly aligned crystals, allow for added phase shifts to light incident on the SLM. By shifting the phase of light, it is possible to allow light to pass through some material without having the light be scattered by the material. This case allows for one to “see” through the material, on account of the light passing through the material rather than being scattered by it. This technology has potential to be used for non-invasive surgeries as well as being a strong starting point for research into optical cloaking. If a procedure for allowing light to pass through a material is developed, then the procedure could be used for the purpose of Optical Cloaking. By expanding the region in which one “sees” through a material so that one encloses the entire material, one would cloak the entire material rather than “see” through some region of it. This procedure would have applications in both medical and military technology

Demonstration of Ion Trap Principles

Particle trapping is a state-of-the-art technology, which already a powerful tool for scientists working with micro- and nano-components. Much interest now revolves around length scales where quantum mechanical effects become pronounced. Quantum mechanics forms our only framework for understanding many problems in solid-state physics (e.g., magnetism), and is playing an ever more important role in applied chemistry, biochemistry and many other areas. Trapping technologies provide a test bed for systematic exploration of fundamental paradigms, offering enhancements to our understanding of key mechanisms and, perhaps, opportunities for quantum information technology. We have assembled a Newtonian Lab demonstration trap, demonstrating key principles of an ion trap, as a first step toward more advanced particle-trapping technology. This system utilizes a low-frequency alternating voltage to trap charged micro-particles. We have confirmed that trapping has occurred, by scattering visible laser beams off the trapped particles. Our next step is to explore designs for a hybrid combination of high-frequency optical tweezers with the sort of low-frequency electrostatic trap we have demonstrated, with the goal of stabilizing particles trapped in low-pressure atmospheres, where it may be possible to achieve cooling towards the quantum mechanical ground state of at least one degree of freedom