Superprism Phenomena Research Articles

Superprism phenomenon in two-dimensional magnetophotonic crystals: Experiment and numerical simulation

Magneto-optical phenomena in quasi two-dimensional magnetophotonic crystals (Q-2D MPCs) have been investigated experimentally and numerically. Multiple Bragg diffraction was shown to be responsible for enhancement of the Faraday rotation and for alteration of its sign in spectra of experimental samples fabricated from bismuth-substituted yttrium iron garnet. It was shown that, for the magnetic superprism effect–control of the light propagation direction by the external magnetic, materials with much larger magneto-optical activity than that of experimental samples are necessary. Spectra obtained by numerical simulations were in a good agreement with experimental ones. Magnetic superprism effect was demonstrated for model samples and parameters necessary for alteration flow of light in quasi-2D MPCs were obtained.

The light intensity-dependent superprism phenomenon in nonlinear photonic crystals

We investigate the light intensity-dependent superprism phenomenon in the two-dimensional Kerr nonlinear photonic crystal (PhC) by nonlinear finite-difference time-domain (FDTD) technique. Results show that when the intensity of the self-pumping beam is increased from 70 to 300 W/μm, the refraction angle of the beam can be tuned about 10 degree. Furthermore, when the input power is high enough, the wave vector can be rotated by the local refractive index interfaces induced by the pumping power. By monitoring the transmission efficiency at different depths in PhCs, the propagating beam is found to undergo several states which correspond to different power loss mechanisms.

Superprism phenomena in waveguide-coupled woodpile structures fabricated by two-photon polymerization

Here we give theoretical as well as experimental evidence for wavelength dependent super-refraction phenomena in waveguide coupled superprisms based on polymer woodpile structures. The photonic crystals were fabricated by means of the two-photon polymerization technique and have a partial band gap at near infrared wavelengths. To visualize the superprism effect the light propagating inside the woodpile structure was imaged using a CCD for a continuous range of wavelengths slightly above the band gap frequency. We were able to demonstrate a change of propagation direction from +50 degrees (positive refraction) to -10 degrees (negative refraction) with respect to the crystal surface normal for a wavelength range between 860 nm and 960 nm. Our results show the great potential of these low refractive index three-dimensional crystals, fabricated in a very fast and single-step process, to serve directly as functional micro-optical devices in the near infrared wavelength regime.

Superprism phenomenon based on holographic polymer dispersed liquid crystal films

The polarization-dependent superprism phenomenon was demonstrated using holographic polymer-dispersed liquid crystal (HPDLC) films. The HPDLC film is designed and fabricated using three coplanar beams. The fabricated HPDLC film contained two-dimensional ordered nano-sized LC domains (∼150nm in diameter) embedded in a polymer matrix; its periodicity was estimated to be ∼350nm. The dispersion of white light from this HPDLC superprism was ∼50°, and the deflection of light output from it was consistent with the theoretical value obtained by the plane wave expansion method.

Superprism phenomena in polymeric woodpile structures

An analysis of the optical properties of photonic woodpile structures is presented. We demonstrate large superprism phenomena inside polymeric woodpile structures having a refractive index of less than n=1.6. Due to the low contrast in refractive indices the structures investigated do not possess a complete photonic band gap. Nevertheless, their photonic band structures show strong anisotropy at frequencies slightly above the band gap in the (Γ-X) direction, leading to an extreme sensitivity to the angle and the frequency of the incident light in the propagation direction inside the crystal. Furthermore, if the woodpile structure is arranged in a prism-like shape, the transmitted beam outside the crystal shows a strong sensitivity to the frequency and angle of the incident light.

Experimental evidence for superprism phenomena in SOI photonic crystals

A first experimental demonstration of a planar superprism in silicon microphotonics technology using silicon on insulator (SOI) substrates is presented. Experimental results for anomalous wavelengthdependent angular dispersion in SOI triangular lattice planar photonic crystals are reported. An angular swing of 14 degrees is measured for light propagating near the Gamma-K direction as the input wavelength is changed from 1295 nm to 1330 nm, which corresponds to an angular dispersion of 0.4 degrees /nm. For the Gamma-M direction, a negative wavelength dispersion has been recorded. An opposite sign angular deviation of 21 degrees is observed as the input wavelength is changed from 1316 nm to 1332 nm, i.e. a dispersion of 1.3 degrees /nm.

Tuning of anisotropic optical properties of two-dimensional dielectric photonic crystals

We study the control of the anisotropic optical properties of the two-dimensional (2D) dielectric photonic crystals (PCs) in a long-wavelength limit. It is achieved either by distorting the symmetry of 2D PCs or by changing the dielectric constant of one of two constituents, for example, that of liquid crystals infiltrated in 2D PCs. Our calculations show that the decrease of dielectric constant per strain in the direction of strain is larger than the one normal to the strain direction. The variation of birefringence observable from the studied structures is calculated to be larger than the birefringence of quartz. Thus the tuning of principal refractive indices of 2D PC would be very attractive for the applications in the polarization optical devices. We have also discussed the effects of strain on the other optical properties of PCs such as the superprism phenomena.

Superprism phenomenon in three-dimensional macroporous polymer photonic crystals

The superprism phenomenon is the extremely large angular dispersion experienced by a light beam when entering a photonic crystal. This arises from the anisotropy of the photonic band structure. Strong anisotropy can be present even in systems without a complete photonic band gap. Here, we describe a theoretical investigation of the superprism effect in three-dimensional macroporous polymer photonic crystals formed from colloidal crystal templates. From the complete photonic band structure, an equal-energy surface (dispersion surface) is obtained. The propagation direction inside the photonic crystal is determined by the gradient of this surface. Using this formalism, we explore the extreme sensitivity of the propagation direction to various input parameters, including the input angle, the light frequency, and the composition of the photonic lattice. Such effects can be exploited for sensing and filtering applications.

Wavelength demultiplexers based on the superprism phenomena in photonic crystals

We numerically analyze microscale wavelength-division-demultiplexing devices based on superprism phenomenon and waveguiding in photonic crystals. A few simple wavelength demultiplexers, which are composed of two photonic crystal structures that have different band structures and are in close contact with each other, are designed and simulated with the finite-difference time-domain method. It is found that depending on frequency, each demultiplexer diffracts incident waves in different directions, and couples them into different output photonic-crystal waveguides with low cross talk.

Extraordinary refraction and dispersion in two-dimensional photonic-crystal slabs

Studies of the refraction and dispersion properties of two-dimensional (2D) photonic-crystal (PC) slab waveguides are reported. The photonic band structure is strongly modified in a slab PC, and only a small number of bands satisfy the guiding conditions imposed by the lack of translation symmetry in the direction perpendicular to the slab; however, it was found that a significant number of the guided modes retain the giant refraction and strong dispersion properties discovered previously in pure 2D PCs. A small change in incident angle resulted in a dramatic change in refraction angle. Furthermore, the dispersion surface exhibited a strong dependence on the frequency, resulting in a superprism effect similar to what has been predicted for pure 2D PCs. In the silicon-based slab PC studied, refraction angles as high as nearly 70 degrees were predicted for incident angles of less than 7 degrees , and frequency components differing by 3% were separated by 15 degrees . The demonstration of giant refraction and superprism phenomena in slab waveguide PCs open the possibility of developing new classes of optical devices that can, for example, be used to develop 2D optical integrated circuits for communications and computing.

Superprism phenomena in planar photonic crystals

We utilize the anomalous dispersion of planar photonic crystals near the dielectric band edge to control the wavelength-dependent propagation of light. We typically observe an angular swing of up to 10/spl deg/ as the input wavelength is changed from 1290 nm to 1310 nm, which signifies an angular dispersion of 0.5 degree/nm. Such a strong angular dispersion is of the order required for wavelength-division multiplexing systems. This is the first demonstration of the "superprism" effect in a planar configuration with a small lattice.

Photonic crystals for micro lightwave circuits using wavelength-dependent angular beam steering

Light-beam steering that is extremely wavelength dependent has been demonstrated by using photonic crystals fabricated on Si. The scanning span reached 50° with only a 1% shift of incident wavelength at around 1 μm. The resulting angular dispersion is two orders of magnitude larger than that achieved with conventional prisms or gratings. The application of such superprism phenomena promises to enable the fabrication of integrated micro lightwave circuits that will allow more efficient use of wavelength resources when used in wavelength multiplexers/demultiplexers or dispersion compensators by enabling lower loss and broader bandwidth.

Superprism phenomena in photonic crystals: toward microscale lightwave circuits

The superprism phenomenon, the dispersion of light 500 times stronger than the dispersion in conventional prisms, was demonstrated at optical wavelengths in photonic crystals (PC's) fabricated on Si. Drastic light-beam steering in the PC's was achieved by slightly changing the incident wavelength or angle. The scanning span reached 50/spl deg/ with only a 1% shift of incident wavelength, and reached 140/spl deg/ with only a 14/spl deg/ shift of the incident angle at wavelengths around 1 /spl mu/m. The propagation direction was quantitatively interpreted in terms of highly anisotropic dispersion surfaces derived by photonic band calculation. The physics behind this demonstration will open a novel field called photonic crystalline optics. The application of these phenomena promises to enable the fabrication of integrated microscale lightwave circuits (/spl mu/LC's) on Si with large scale integrated (LSI)-compatible lithography techniques. Such /spl mu/LC's will allow more efficient use of wavelength resources when used in wavelength multiplexers/demultiplexers or dispersion compensators by enabling lower loss and broader bandwidth.

Superprism phenomena in photonic crystals

Extraordinary angle-sensitive light propagation, which we call a superprism phenomenon, was demonstrated at optical wavelength in photonic crystals with three-dimensional-periodic structure fabricated on Si substrate. The propagation beam was swung from $\ensuremath{-}90\ifmmode^\circ\else\textdegree\fi{}$ to $+90\ifmmode^\circ\else\textdegree\fi{}$ with a slight change in the incident angle within $\ifmmode\pm\else\textpm\fi{}12\ifmmode^\circ\else\textdegree\fi{}.$ This effect together with wavelength sensitivity is at least two orders of magnitude stronger than that of the conventional prism. The incident-angle dependence including negative refraction and multiple beam branching was interpreted from highly anisotropic dispersion surfaces derived by photonic band calculation. These phenomena will be available to fabricate microscale light circuits on Si with LSI-compatible lithography techniques.