Janusz Murakowski

Dispersion-based optical routing in photonic crystals

We present and experimentally validate self-collimation in planar photonic crystals as a new means of achieving structureless confinement of light in optical devices. We demonstrate the ability to arbitrarily route light by exploiting the dispersive characteristics of the photonic crystal. Propagation loss as low as 2.17 dB/mm is observed, and proposed applications of these devices are presented.

Fabrication and characterization of three-dimensional silicon tapers

We present the fabrication of 3D adiabatically tapered structures, for efficient coupling from an optical fiber, or free-space, to a chip. These structures are fabricated integrally with optical waveguides in a silicon-on-insulator wafer. Fabrication involves writing a single grayscale mask in HEBS glass with a high-energy electron beam, ultra-violet grayscale lithography, and inductively coupled plasma etching. We also present the experimentally determined coupling efficiencies of the fabricated tapers using end-fire coupling. The design parameters of the tapered structures are based on electromagnetic simulations and are discussed in this paper.

Self-collimation in photonic crystal structures: a new paradigm for applications and device development

In this paper, we report on the development of the self-collimation phenomenon in photonic crystal structures for integrated optics applications. In addition, detailed numerical analysis, design procedures, fabrication and characterization techniques are included. Applications presented in this paper include: channelless waveguiding, orthogonal bending of light, tunable beam splitter, all-optical analog-to-digital converter, reconfigurable optical switch, chemical/gas sensor and a three-dimensional optical interconnect bus.

High-efficiency coupling structure for a single-line-defect photonic-crystal waveguide

We present the design and fabrication of a planar structure for coupling light from a multimode feed waveguide into a single-line-defect photonic-crystal waveguide. Finite-difference time-domain calculations predict a coupling efficiency of greater than 90%, and preliminary experimental results indicate successful coupling through a single-line-defect photonic-crystal waveguide. Device design, fabrication, and characterization are presented.

Gas-absorption spectroscopy with electronic terahertz techniques

In this paper, we present the first gas-absorption spectra measured with an all-electronic terahertz spectrometer. This instrument uses phase-locked microwave sources to drive GaAs nonlinear transmission lines that produce picosecond pulses, enabling measurement of broad-band spectra. By sweeping the fundamental excitation, however, the spectrometer can also measure single lines with hertz-level precision, a mode of operation not readily available with optoelectronic terahertz techniques. Since this system is based on integrated circuits, it could ultimately function as an inexpensive gas-sensing system, e.g., for vehicle emissions, an application for which we analyze the sensitivity of a prototypical system.

Photonic Crystal Structures and Applications: Perspective, Overview, and Development

In this paper, we present an overview of milestone achievements in the research and development of photonic crystal structures and their perspective applications. We highlight challenges in the analysis techniques, device design, efficient coupling techniques, and fabrication and characterization techniques for both planar and three-dimensional structures. We discuss extensively progress to date to overcome various aspects in the available modeling and simulation tools as well as the necessary fabrication procedures to produce functional photonic crystal structures and devices. Hence, the goal of the work presented in this paper is to present key building blocks, which will in turn facilitate the full utilization of the unique spatial and temporal properties of photonic crystal structures

Radiometric Millimeter-wave detection via optical upconversion and carrier suppression

We report a novel technique for radiometric detection of radiation in the millimeter-wave regime based on optical modulation. Millimeter-wave energy modulated onto an optical carrier is detected using a low-bandwidth photodetector with optical filtering to suppress the carrier. Using this technique, we have achieved noise-equivalent powers as low as 20 pW/spl radic/Hz for a 44-GHz narrow-band signal using chopping techniques. Such detection was implemented using commercially available components and without RF or optical amplification. Further improvements in sensitivity are expected as the setup is optimized for operation in the frequency band of interest.

Subwavelength imaging by a flat cylindrical lens using optimized negative refraction

We experimentally demonstrate subwavelength imaging by a “flat cylindrical” lens using negative refraction. A two-dimensional photonic crystal whose dispersion at the second band provides group velocity opposite to the phase velocity for electromagnetic waves is employed to realize the flat lens, and the working frequency is chosen so that the effective refractive index is approximately equal to −1.0. Experiment demonstrated the imaging of a point source in both amplitude and phase in the millimeter-wave regime. By measuring the field distributions in the object plane and image plane, we observed amplification of evanescent waves and subwavelength size image. The image of two incoherent sources with subwavelength distance showed two resolvable spots, which served to further verify subwavelength resolution.

Three-dimensional photonic crystal flat lens by full 3D negative refraction

We present the experimental demonstration of imaging by all-angle negative refraction in a 3D photonic crystal flat lens at microwave frequencies. The flat lens is made of a body-centered cubic photonic crystal (PhC) whose dispersion at the third band results in group velocity opposite to phase velocity for electromagnetic waves. We fabricated the photonic crystal following a layer-by-layer process. A microwave imaging system was established based on a vector network analyzer, where two dipoles work as the source and the detector separately. By scanning the volume around the lens with the detector dipole, we captured the image of the dipole source in both amplitude and phase. The image of two incoherent sources separated by 0.44lambda showed two resolvable spots, which served to verify sub-wavelength resolution.

High-efficiency broad-band transmission through a double-60/spl deg/ bend in a planar photonic Crystal single-line defect waveguide

We present two designs to improve the transmission of a conventional double-60/spl deg/ bend in a single-line defect planar photonic crystal waveguide by locally optimizing the shape and the size of air holes of a photonic crystal lattice at the corners. We fabricate these devices on a silicon-on-insulator substrate and characterized them using tunable laser sources over a wavelength range from /spl lambda/=1.259 /spl mu/m to /spl lambda/=1.641 /spl mu/m. As we show, over a 9% bandwidth, less than 1-dB loss/bend was observed. In order to theoretically validate these experimental results, the three-dimensional finite-difference time-domain simulations are performed and found to agree with the experimental results.