Professor Iam-Choon Khoo

Vitae

Prof. Iam-Choon Khoo received the B.Sc with First Class Honours in Physics from the University of Malaya in 1971, and the M.A. and Ph. D. degrees in Physics from the University of Rochester in 1973, and 1976 respectively. He joined Penn State in 1984 and is currently the William E. Leonhard Endowed Professor of Electrical Engineering.

Since joining Penn State, he has developed and taught several undergraduate and graduate courses, including the senior/graduate level Lasers-Principles and Applications, and the graduate level Lasers and Optical Electronics. He has also taught undergraduate courses in Fiber Optics, Electro-Optics and graduate level Nonlinear Optics, Quantum Electronics and Liquid Crystals.

Prof. Khoo is internationally known for his pioneering and leading work in liquid crystals, and in nonlinear optical phenomena and applications. At Penn State, he has established and directed the Nonlinear Optics and Liquid Crystal Research Laboratory. Over the years, his laboratory has received research funding from various Government agencies including:- the National Science Foundation, Defense Advanced Research Projects Agency, Navy Air Development, Air Force Office of Scientific Research, Air Force Phillips Laboratory, and the Army Research Office.

Currently his research programs are centered on theories and experiments on nonlinear- and electro- optics materials such as liquid crystals, fibers and nano-structured and novel refractive metamaterials and related studies of coherent optical wave mixing processes, beam/image/signal processing, optical switching and modulation, optical limiting and sensor protection applications and photonic devices enabled by unique properties of these novel optical materials.

He is the principal author of over 460 technical publications [191 refereed journal publications/proceedings and 271 technical conference presentations], 12 invited book chapters, and the author, co-author or co-editor of 7 books. Among the awards and honors he received are: the Pennsylvania State Engineering Society PSES Outstanding Research Faculty Award in l987, the Penn State University Faculty Scholar Medal for Outstanding Achievements in Physical Science and Engineering in 1988, the Fellow award of the Optical Society of America in l988, the PSES Premier Research Award in 1995, the IEEE Fellow award in 1998, and the United Kingdom Institute of Physics Fellow award in 1999. He has also served as the External Ph. D. Examiner for Trinity College [Physics], Dublin, Ireland (2001); Chalmers University [Physics], Sweden (2002) and Cambridge University [Electrical Engineering) UK (2005). He was the 2003 Sturgeon Memorial Plenary Lecturer [Cambridge University- British Liquid Crystal Society]

Current Research Program Details:
[Funded by National Science Foundation, Army Research Office, Air Force Office of Scientific Research, Defense Advanced Research Project Agency]

1."Supra-nonlinear liquid crystalline materials"
Research Program Outline:
This program of experimental and theoretical studies is focused on nematic liquid crystalline systems that exhibit record breaking high optical nonlinearities and photosensitivity. These unique combinations of nonlinear optical and optoelectronics properties are observed in nematics doped with photo-charge producing compounds such as methyl-red dye, or nano-tube, nano-rods and fullerenes. In these studies, we seek to elucidate and completely characterize the physical origins of extremely large optical nonlinearities, and to explore the feasibility of utilizing these unique materials in advanced imaging, optical modulation, mixing, limiting, holographic and adaptive optics devices. The emergent devices will be compact, and possess very wide spectral and temporal operational bandwidth, and will operate at practical low power/intensity levels.

References: “Nonlinear dynamics in laser polarization conversion by stimulated scattering in nematic liquid crystal films,” I. C. Khoo et all, Phys. Rev. E68 pp 042701-1 to -4 [2003]; I. C. Khoo, J. Ding, Y. Zhang, K. Chen and A. Diaz, “Supra-Nonlinear Photorefractive Response of Single-wall Carbon Nanotube- and C60-Doped Nematic Liquid Crystas81,” Appl. Phys. Letts. 82, pp. 3587-3589 (2003). I. C. Khoo, Kan Chen and Y. Zhang Williams, “Orientational Photorefractive Effect in undoped and CdSe Nano-Rods doped Nematic Liquid Crystal – Bulk and Interface Contributions,” IEEE J. Specioal topics in Quantum electronics JSTQE 12 (3), pp. 443-450 [2006].

2."Eye and Sensor Protection against agile frequency and multiple time-scale lasers"
Research Program Outline:
The development of powerful and tunable laser sources and the increasing spread of their use in different fields such as research, medicine, and industry, are making the protection of eyes and optical sensors a challenging problem. The absorptive fixed wavelength filters currently used in protective devices suffer from limited ambient transmission and possible saturation effects, and cannot provide broadband protection against agile frequency lasers. Nonlinear optical effects leading to variation of the transmission and refractive index with light intensity offer the possibility of wide-band, self-activated protection. This program focuses on synergetic use of nonlinear molecular photonics and fiber array optics to engineer extremely broadband [temporally and spectrally] all-optical limiters and switches. In particular, we endeavor to develop devices that are capable of wide field of view, large dynamic range, and optical limiting action against picosecond- to micro-second laser pulses and cw lasers in the entire visible spectrum as well as the near infrared. The program entails material synthesis, nonlinear fiber optic propagation modeling and the development of nonlinear image transmitting fiber faceplate.

References: I. C. Khoo, M. V. Wood, M. Y. Shih and P. H. Chen, “Extremely Nonlinear Photosensitive Liquid Crystals for Image Sensing and Sensor Protection,” Optics Express, Vol. 4, no. 11, pp 431-442 (1999); I.C. Khoo, Andres Diaz and J. Ding, “Nonlinear-absorbing Fiber Array for Large Dynamic Range Optical Limiting Application against Intense Short Laser Pulses, J. Opt. Soc. Am B21, pp. 1234-1240 [2004].

3. Tunable Negative-Zero-Positive Index Meta-Materials
Research Program Outline:
Current research and development in electro- and nonlinear- optical materials for photonic applications are largely centered on nano-structured materials that exhibit unique physical and optical properties such as Negative- and Zero refractive indices. In particular, our programs are directed at creating structure/device’s properties and functions that could be reconfigured or tuned over a very wide spectral/frequency range. Among existing materials, nematic liquid crystals clearly stand out as the preferred choice as they possess extraordinarily large electro-optics and nonlinear optical responses, allowing both electrical and/or all-optical tuning. Furthermore, they are also compatible with almost all widely used optoelectronic materials and possess very broadband [near UV-microwave] transparency and large optical birefringence. Their fluid nature allows easy incorporation into various geometries and nm-scale pore sizes (e.g. 3-D inverse opal structures, Frequency Selective Surfaces). We are also investigating the possibility of realizing bulk negative-zero index materials by dispersing various nano-spheres in electro-optics active or nonlinear optical host materials besides liquid crystals. These structures enable construction of optical filters with an unparalleled spectral tuning range. They could also exhibit negative- zero or low- index of refraction and thus will enable a host of optical devices and processes not possible with conventional optics.

References: I. C. Khoo, D. H. Werner, X. Liang, A. Diaz and B. Weiner, “Nano-sphere dispersed liquid crystals for tunable negative-zero-positive index of refraction in the optical and Terahertz regimes,” Optics Letts. 31, 2592 (2006). E. Graugnard, J. S. King, S. Jain, C. J. Summers, Y. Zhang-Williams and I. C. Khoo, “Electric field tuning of the Bragg peak in large-pore TiO2 inverse shell opals,” Phys. Rev. B72, 233105 [4 pages] (2005).

Summary of Technical Publications/Inventions
*Author/co-author/editor of 7 books and author of 12 book chapters.
* Editor of 10 Proceeding volumes [Liquid Crystal I, II, III, IV, V, VI, VII, VIII, IX, X].
* Editor-in-Chief of 15 Volumes-year of Journal [JNOPM 1991-2006].
* Authored and co-authored over 460 Technical Publications & Conference Presentations
[191 Refereed Journals and Proceedings; 271 Conference Presentations]
* Inventor in 6 invention disclosures and two US Patents:
- US Patent # 5,552,915 “Liquid Crystal Nonlinear Photorefractive Electro-Optical Storage Device Having a Liquid Crystal Film including Dopant species of C60 and C70” [9/3/1996]
- US Patent #5,589,101“Liquid Crystal Fiber Array for Optical Limiting of Laser
Pulses and for Eye/Sensor Protection” [12/31/1996].

List of Publications