Nonlinear Optics
From Self-Focusing to Liquid Crystal Nonlinear Optics
Starting from suppression of self-focusing effects in high-power laser systems we moved to reflective, absorptive and refractive nonlinearities of monomeric liquid crystals under high-power, nanosecond laser irradiation. This research is important for optical power limiting and for laser optics of high-power laser systems. More than 300 optical elements of the Laboratory for Laser Energetics Omega laser were made of liquid crystals. Among important results are athermal helical pitch unwinding of the cholesteric mirrors (both in a laser resonator and in a free space) that puts the limits of their use at high laser intensities; feedback-free kaleidoscope of hexagons in the beam with dye-doped liquid crystals; strong dependence of sign and value of nonlinear refraction on a laser-beam diameter in a presence of two-photon and excited state absorption; cumulative effects in nonlinear refraction of planar aligned liquid crystals at low pulse repetition rate (5-10 Hz) and pattern formation in a single beam without feedback in a presence of nonlinear absorption.
High-Intesity Femtosecond Laser Laboratory
His group is studying a variety of unique nonlinear optical properties of metals with femtosecond laser technique. Extreme nonlinear optical effects, such as high-order harmonics and ultrashort pulse generation can be studied in strong fields.
Integrated Nonlinear Photonics
Nonlinear optical processes have attracted long-lasting interest ever since the first observation of second-harmonic generation, which founded a broad range of applications including photonic signal processing, tunable coherent radiation, frequency metrology, optical microscopy, and quantum information processing. In general, nonlinear optical effects are fairly weak and have to rely on substantial optical power to support nonlinear wave interaction. However, high-quality nanophotonic devices are able to confine strongly the optical waves into a tiny volume/area with significant optical field inside, resulting in dramatically enhanced nonlinear optical effects to an extent inaccessible in conventional bulk media. On the other hand, operating in the micro-/nano-scopic scale offers unprecedented freedom of versatile device design that enables flexible engineering of device characteristics (such as geometry, dispersion, quality factor, optical/mechanical resonance, etc) for various application purposes. We currently explore new material platforms and innovative device designs for novel nonlinear photonic functionalities with high efficiency, long coherence, broad bandwidth, and/or large tunability.
Nonlinear Patterns for Bio-Imaging and Optomechanics for Quantum Information Science
Nonlinear Pattern Formation
Nature is nonlinear, which allows for complex and beautiful dynamics and patterns from turbulence and chaos to fractals and self-similarity. Nonlinear optical systems are relatively simple and therefore provide ideal testbeds to explore universal concepts in nonlinear pattern formation. For example, the soliton is readily observed in optical systems and has also had tremendous technological value for its role in telecommunications and for enabling ultrashort pulse sources. Research in Professor Renninger’s lab involves theoretical and experimental exploration of nonlinear optical processes in bulk, fiber, and nanophotonic systems. Beyond fundamental explorations, stable patterns are applied towards applications like nonlinear imaging deep into the brain.
Brillouin scattering and optomechanics
Brillouin scattering is a nonlinear optical effect involving the interaction of light with sound. Studied since the early days of nonlinear optics, stimulated Brillouin scattering is one of the strongest nonlinear optical effects and has enabled technological advances for sensing, microwave processing, slow and fast light, high coherence source generation, and optical phase conjugation. Professor Renninger’s lab is exploring new forms of optomechanical coupling in an array of fiber geometries for new applications from acoustic sensing with fibers to novel optical source generation. The lab is also pushing Brillouin scattering to the cryogenic and quantum limits in a new platform for quantum information processing, ultrasensitive metrology, and fundamental tests of quantum decoherence. All research directions involve both experiment and theory.
Slow and Fast Light, Quantum Imaging Techniques, Optical Metamaterials
Slow and fast light
Professor Boyd and his group are working on the development of methods that will allow them to control the group velocity of light for a variety of materials of interest in photonics. This group is presently working on a several topics in this area, including fast and slow light in erbium doped fiber amplifiers, applications of slow and fast light in telecommunications, and the use of surface plasmon polaritons to induce slow-light effects.
Quantum imaging
Professor Boyd's group is also working on the development of techniques in the field of quantum imaging, which utilizes the quantum nature of light to perform image formation with higher resolution or sensitivity than can be achieved with classical light sources. Two specific projects of current interest include the development of methods for quantum lithography and for achieving enhanced spatial resolution in microscopy.
Composite photonic materials
The goal of this research is to form nanocomposite materials with superior properties for use in nonlinear optics and laser engineering. One aspect of this work entails forming composites in such a manner that, as a consequence of local field effects, the nonlinear response of the composite is larger than that of the constituent materials. Another aspect of the work is to construct composites with a very large response by forming metal/dielectric composites. Still another aspect of this work is to form laser gain media in which the optical properties can be tailored through use of local field effects.