Miguel Levy

Fabrication of single-crystal lithium niobate films by crystal ion slicing

We report on the implementation of crystal ion slicing in lithium niobate (LiNbO3). Deep-ion implantation is used to create a buried sacrificial layer in single-crystal c-cut poled wafers of LiNbO3, inducing a large etch selectivity between the sacrificial layer and the rest of the sample. 9-μm-thick films of excellent quality are separated from the bulk and bonded to silicon and gallium arsenide substrates. These single-crystal films have the same room-temperature dielectric and pyroelectric characteristics, and ferroelectric transition temperature as single-crystal bulk. A stronger high-temperature pyroelectric response is found in the films.

Waveguide optical isolator based on Mach–Zehnder interferometer

A waveguide optical isolator based on nonreciprocal interference is demonstrated. Ridge waveguides are fabricated in a Mach–Zehnder configuration on a single film of bismuth-, lutetium-, neodymium-iron garnet. With this design, no polarizers are required to achieve extinction in the backward propagation direction. This isolator exhibits a 19 dB extinction ratio at λ=1.54 μm. A flat wavelength dependence, to within 2 dB, has been observed in the range between 1.49 and 1.57 μm.

High transmission enhanced Faraday rotation in one-dimensional photonic crystals with defects

Photonic crystals containing defects produce enhanced Faraday rotation but existing designs have low intensity output. We show that designs with two-defects possess sufficient freedom to attain high transmission over a large range of rotation angles in very short lengths. We optimize such systems for 45/spl deg/ rotation in optical isolators.

Photonic bandgaps with defects and the enhancement of Faraday rotation

We investigate enhancement of magnetooptical rotation in periodic magnetic garnet thin-film stacks with defects using a combination of coupled-mode theory and matrix calculations. We prove that a combination of high rotation per unit length and high output is unattainable for a symmetric grating with a single central defect. We demonstrate that the addition of a second defect introduces sufficient degrees of freedom to allow high transmission for a much larger range of rotation angles than was previously possible. We present a number of designs with emphasis an achieving 45/spl deg/ rotation in very short propagation lengths.

Integrated optical isolators with sputter-deposited thin-film magnets

This letter describes the use of a compact sputter-deposited thin-film magnet that is directly integrated onto a waveguide isolator fabricated in magnetic thin-film garnets. Film magnets of different thicknesses are sputtered onto the waveguides, and isolation ratios of 29 dB are obtained with negligible excess loss. Stress-birefringent effects due to the ferromagnetic film overlayer are eliminated by the use of an aluminum compliant buffer.

Electro-optic modulation in crystal-ion-sliced z-cut LiNbO3 thin films

Electro-optic modulation is demonstrated in 10-μm-thick single-crystal LiNbO3 films obtained by crystal ion slicing. This technique uses ion implantation of single-crystal bulk samples followed by selective etching. The measured electro-optic response of these films is comparable, within experimental error, to that of single-crystal bulk LiNbO3 and is superior to previously reported values for epitaxial polycrystalline thin films. The product of half-wave voltage and modulator length, VπL, is 8 V cm. Post lift-off annealing is shown to be of key importance in improving the modulator extinction ratio.

Carbon nanotube tipped atomic force microscopy for measurement of <100 nm etch morphology on semiconductors

The use of carbon nanotubes as tips in atomic force microscopy for a systematic study of dry etching pattern transfer in GaAs is described. The GaAs samples are patterned via electron beam lithography and then etched using magnetron reactive ion or chemically assisted ion beam processing. The technique allows diagnosis, in air, of etched features with scale sizes of <100 nm.

Large magnetooptical Kerr rotation with high reflectivity from photonic bandgap structures with defects

We perform a theoretical study of enhancement of magnetooptical rotation on reflection of light from a periodic system with a defect. Using calculations based on a coupled mode approach and the transfer matrix method we demonstrate that an asymmetric placing of a single defect allows arbitrary Kerr rotations with better than 99% reflectivity from very short devices.

The on-chip integration of magnetooptic waveguide isolators

The miniaturization of optical isolators and their on-chip integration with various optoelectronic devices has been pursued for a number of years. However, reducing the standard paradigmatic construction used in commercial isolators to waveguide form requires stringent fabrication tolerances and special materials that tend to render the process difficult and costly. Thus, novel approaches in device design and materials technology are called for and are being pursued. This paper discusses the application of the Faraday and nonreciprocal phase shift effects in waveguide isolator operation, the complications that arise in the miniaturization of these devices, and the novel solutions being pursued.

Polarization rotation enhancement and scattering mechanisms in waveguide magnetophotonic crystals

Intermodal coupling in photonic band gap optical channels in magnetic garnet films is found to leverage the nonreciprocal polarization rotation. Forward fundamental-mode to high-order mode backscattering yields the largest rotations. The underlying mechanism is traced to the dependence of the grating-coupling constant on the modal refractive index and profile of the propagating beam. Large changes in polarization near the band edges are observed in first and second orders. Extreme sensitivity to linear birefringence exists in second order.