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Prof. David J. Hagan

Prof. David J. Hagan

Professor and Associate Dean
CREOL, The College of Optics and Photonics
University of Central Florida

P.O. Box 162700

Orlando FL 32816-2700
United States

tel: 407 823 6817
E-mail: hagan@creol.ucf.edu
Web: HTTP://www.creol.ucf.edu

Area of Expertise

Nonlinear Optics, Nonlinear Spectroscopy, Optical Switching and limiting. Peer-reviewed publishing


David Hagan is a Professor of Optics and the Associate Dean at the College of Optics and Photonics, University of Central Florida. He is the editor-in-chief of the open-access journal, "Optical Materials Express". His current research interests include nonlinear optical characterization of materials, nonlinear optical processes in semiconductors and organics, nanostructure enhancement of optical nonlinearities and applications of nonlinear optics in optical power limiting and switching. He is a Fellow of OSA and Senior Member of IEEE.

Lecture Title(s)

An introduction to the nonlinear optical properties of materials.
I will review the various processes that lead to nonlinear optical (NLO) effects from a broad and historical perspective. This will illustrate the tremendous advances in nonlinear optics that have occurred since the development of the laser in the early 1960s. I will particularly focus on nonlinear self-action, such as nonlinear absorption and refraction, and how these effects may be applied to Optical Switching. We will show how nonlinear absorption and refraction are related and show that there are limits on the magnitude of nonlinear coefficients. It has long been the goal of NLO to find materials that exhibit very strong nonlinear effects. In order to achieve this, it is necessary to develop techniques for highly accurate and unambiguous characterization of the NLO properties. We will describe in detail the major methods we employ for the characterization of nonlinear refraction and absorption in materials. In particular, I will concentrate on techniques developed in my research group: Z-Scan; beam deflection and excite-probe with white light continuum. We will show how nonlinear absorption and refraction are related and show that there are limits on the magnitude of nonlinear coefficients.

Extremely nondegenerate nonlinear optics for IR detection and optical switching
Two-photon absorption (2PA) in semiconductors has long been known to scale as the inverse third power of the energy gap, i.e. E_g^(-3), which limits the 2PA coefficients available in large gap semiconductors. However it is also known that in the highly nondegenerate case, where the input wavelengths are very different, the 2PA rate can be greatly enhanced over the degenerate case. We have verified this for several direct gap semiconductors in pump-probe transmission experiments with femtosecond and picosecond pulses, where we showed that, in many direct-gap semiconductors, nondegenerate 2PA coefficients are enhanced approximately 100-fold over the degenerate case. Based on this effect, one may obtain sensitive gated detection of weak IR radiation using conventional semiconductor photodiodes. We have demonstrated this with standard GaN and GaAs photodiodes. The minimum detected IR pulse energy in GaN is as low as 20 pJ energy as compared to 200 pJ for a standard cooled MCT detector. It is worth noting that this process does not use IR crystals or phase-matching, as employed by (2) upconversion detection. In this talk, I will show how this detection scales to other semiconductors and how one may optimize device geometries for practical detection.

A guide to publishing your work in peer-reviewed journals
In this presentation, I give some advice on steps to take in preparing to write your manuscript and on journal selection, considering the novelty of the work and who your audience is intended to be. I will give an introduction to ethical issues, including who should be included as authors, properly citing the works of others integrity and completeness of data, and on obtaining permissions. I will also discuss the peer-review process, describing how it works and how to give your paper the best chance of being fairly and quickly reviewed.

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