This Small Business Innovation Research (SBIR) Phase I project is focused on technology to improve microscopy through the development of an advanced spatial light modulator (SLM). Improved microscopy is required for many different applications, but perhaps the most compelling is the better understanding cellular physiology. The inability to view dynamic, live processes with high resolution limits the understanding of cellular division, cellular signaling, the contraction and relaxation of muscle cells, and the absorption of nutrients by epithelial cells. A better understanding of these processes could lead to many medical improvements. Recent advances in microscopy involve the integration of SLMs to improve imaging capabilities, e.g. fluorescence holographic microscopy, double?]helix photoactivated localization microscopy, and instantaneous spatial light interference microscopy. Most of this work has been performed utilizing display chips. Much better results may be obtained with an SLM designed for microscopy. One problem utilizing commercially available liquid crystal SLMs is poor optical efficiency. Most of the loss is due to the inability of the liquid crystal to modulate phase for any polarization state, forcing the elimination of half of the light. The proposed project will develop a technique that would enable an SLM to phase modulate any random polarization state, thereby more than doubling the light efficiency.
The broader impact/commercial potential of this project will result in improved microscopy resolution, which could in turn lead to better scientific understanding in any field that currently utilizes light microscopy. It is envisioned that the majority of improvements will occur in the cellular biology field due mainly to the current difficulty in viewing such processes as live cellular division. However, other areas of improvement would likely include such applications as holographic optical trapping and even telescopes, providing better vision through our turbulent atmosphere. The commercial impacts of this proposed project will occur in multiple areas and different points in time. It is anticipated that the initial market will be scientific research and development community using these advanced spatial light modulators to develop many new applications. Once a promising application has been developed, then instrument companies will begin to integrate these SLMs into new microscope systems for the research and development community, as well as medical laboratories. The proposed advanced SLM could result in driving an entirely new test and measurement equipment industry.
Liquid crystal on silicon (LCOS) spatial light modulators (SLMs) are general purpose tools that use high-resolution, dynamic holography to control the wavefront of an optical system. This capability is currently revolutionizing the optical sensing, probing and manipulation techniques being used in a variety of nano-, micro- and macro-applications, for example: Holographic optical trapping for blood sorting, drug research, nano electronics assembly, forensics, etc. Wavelength/spectral manipulation for generating/shaping ultra-fast pulses and producing structured light illumination for microscopy applications Wavefront encoding for optical communication encryption Wavelength selectable switching (WSS) which enables reconfigurable optical add drop multiplexers (ROADMs) for optical communications Adaptive optics in free-space optical communications, lidar systems, lightweight flexible optical trains, etc. IR scene projectors for hardware in the loop testing Non-mechanical beam steering to replace gimbal assemblies and bring about conformal-aperture operation for active and passive EO systems. A primary drawback of using LCOS SLM assemblies in several of the above applications has been the polarization dependence of the liquid crystal phase modulator. In this effort, Boulder Nonlinear Systems (BNS) has successfully demonstrated a polarization independent (PI) LCOS SLM. The proposed concept was first demonstrated with a single-pixel cell and then implemented as a 256×256 array in Phase I. In the follow-on Phase IB effort, BNS integrated the PI modulator with a mirror coated, 256x256 backplane. This high efficiency (HE) assembly was used to demonstrate and verify our assumptions that the 7.5 µm pixel design developed in Phase I will provide sufficient voltage for driving a HE version of the PI modulator. Thus, the Phase I efforts lead the way for developing a 2k×2k LCOS backplane through a follow-on Phase II effort. In summary, Boulder Nonlinear Systems has determined that a large format, high-efficiency, polarization insensitive, LCOS SLM, such as that needed for enhanced resolution microscopy applications, can be developed. As part of this effort, a 256x256 HE-PI SLM prototype was delivered to the University of Colorado to further research and educational activities in the area of super-resolution microscopy. This high-efficiency, polarization-independent device will provide new capabilities by addressing critical throughput requirements for applying SLMs to light-starved microscopy applications. The demonstrated polarization-independent SLM enables new applications for SLMs and will greatly simplify the optical setup for many of the current applications. BNS SLM designs have already overcome the constraints of display technologies by creating high-performance, optically flat, low-ripple devices. This Phase I effort has now overcome the remaining constraint of polarization dependence. An emerging area of interest in telecommunications is wavelength selective switching for next-generation optical routers. Microscopy applications for this technology include: structured illumination for improved resolution; wavefront correction to correct for media, thermal, and optical system impacts on resolution. Remote sensing applications include: precision non-mechanical beam steering; wavefront correction for turbulence and system aberrations mitigation; compressive sensing; and agile beam control for simultaneous dwell and scan. All of these application areas will greatly benefit from an optically flat, high-resolution, polarization-independent spatial light modulator.
