The primary proposed objective is to determine the feasibility of achromatic spatial modulation of the optical wavefront in microscopy. Modern microscopy methods seek to adapt traditional optical systems for optimal function with digital detection and processing systems. These methods employ devices, referred to as spatial light modulators, to manipulate the phase and amplitude of light illuminating, and/or transmitted by, a sample. Phase and amplitude of light waves in the microscope illumination and (or) imaging paths are engineered in application-specific ways;to improve resolution, acquire quantitative data in addition to observational data and increase the rate of information throughput. Current spatial light modulation devices are all wavelength dependant, thus the use microscopy methods developed through this approach is restricted. A sample's properties can only be studied one wavelength at a time. To overcome this limitation, Boulder Nonlinear Systems proposes to investigate the feasibility of incorporating alternative phase modulation methods in a liquid-crystal spatial light modulator. The proposed geometric phase modulation methods are wavelength independent. Modulation of the geometric phase will allow achromatic lateral (x-y) phase modulation of the microscope wavefront over the visible wavelength range. Implementation of this approach is currently limited by the state of the art in liquid crystal technology. However, the potential benefits of an achromatic spatial light modulator to the field of microscopy include expanded capability and increased commercial accessibility of current microscopy methods using spatial light modulators as well as new avenues for innovative applied microscopy research in biology, chemistry and nanotechnology. Potential barriers to this solution and its applicability to the field of high-resolution optical microscopy will be investigated through assessment of a proto-type programmable liquid crystal spatial light modulator device that operates using achromatic geometric phase modulation methods. Although limited in capability, this device will be used to assess whether or not further research into this approach is warranted. Such an assessment will be made by measuring the difference in chromatic performance between current liquid crystal spatial light modulation methods and geometric phase-shifting modulation in an x-y pixilated device. The marketability of this type of devices will be evaluated through demonstration of stable and uniform operation in a simple achromatic multi- focal imaging experiment.
Wave-front engineering is a multi-disciplinary microscope systems design approach, often implemented with an x-y variable light modulator, which is changing the fundamental limits of optical imaging. Implementation of developing microscope system designs at high speed (~1kHz) and without restriction with regard to wavelength (within the visible range) may allow observation of new dynamic biological and chemical processes.
