Antonije M. Radojevic

LARGE ETCH-SELECTIVITY ENHANCEMENT IN THE EPITAXIAL LIFTOFF OF SINGLE-CRYSTAL LINBO3 FILMS

We report on a large etch selectivity enhancement in the epitaxial liftoff of He+-implanted single-crystal lithium niobate (LiNbO3) films upon rapid thermal annealing. A buried sacrificial layer is formed by ion implantation. Heat treatment is found to reduce the time needed for film detachment by a factor as large as 100. Implant damage and postanneal stress-induced etch selectivity become nearly independent of implantation energy upon annealing. Large (0.5×1u200acm2) 5–10-μm-thick single-crystal LiNbO3 films of excellent quality are detached in just a matter of a few hours.

Fabrication and evaluation of a freestanding pyroelectric detector made from single-crystal LiNbO 3 film

We have packaged a rectangular 3 mm x 4 mm, 10-mum-thick Z-cut lithium niobate (LiNbO(3)) film produced by crystal ion slicing (CIS) and evaluated its performance as a pyroelectric optical detector. We justify the difficulty of preparing the film by showing that the freestanding detector has much greater sensitivity than the same detector bonded to a substrate. We compare the sensitivity of three CIS-film detectors with that of a detector based on a 230-mum-thick LiNbO(3) plate and describe the detectors spatial uniformity and noise-equivalent power.

Zeroth-order half-wave plates of LiNbO 3 for integrated optics applications at 1.55 μm

Reports on fabrication and characterization of the first zeroth-order half-wave plates of LiNbO/sub 3/ obtained by crystal ion slicing (CIS). Polarization rotation was demonstrated in 10-/spl mu/m-thick freestanding LiNbO/sub 3/ films with 30-dB conversion ratios and negligible material loss. Polarization-independent performance was demonstrated in a hybrid-optic device comprising a CIS wave plate integrated with single-mode silica-based channel waveguides.

Strong nonlinear optical response in epitaxial liftoff single-crystal LiNbO3 films

We report on optical frequency mixing in epitaxial liftoff thin films of single-crystal LiNbO3 integrated onto heterogeneous planar glass platforms. These films are found to have a nonlinear optical response comparable to that of the bulk. Second-harmonic generation is investigated as a function of crystal orientation, ion implantation, and modal and temperature dispersion. Ion implantation-induced shifts in the refractive indices are shown to be useful for achieving phase matching.

Momentum-resolved excited-electron lifetimes on stepped Cu(7 7 5)

Abstract The lifetime of n=1 image-state electrons on stepped on Cu(7xa07xa05) has been measured as a function of their translational momentum, k∥. At the terrace normal this lifetime is equal to that for flat Cu(1xa01xa01), i.e. τ=18±2 fs . For motion parallel to the step orientation, the lifetime decreases symmetrically about k∥=0 and the absolute values are in close agreement with that predicted by a recent many-body theory. Contrasting data for motion perpendicular to the step edges is also presented.

Domain-engineered thin-film LiNbO 3 pyroelectric-bicell optical detector

We have fabricated a bicell detector consisting of a single freestanding film of single-crystal lithium niobate (LiNbO/sub 3/) 10-/spl mu/m thick, having two adjacent domains of opposite spontaneous polarization, and hence, two adjacent pyroelectric detector regions of equal and opposite sensitivity. The film was created by applying the process of crystal ion slicing and electric field poling (domain engineering) to a Z-cut LiNbO/sub 3/ wafer. The detectors noise equivalent power was 6 nW/spl middot/Hz/sup -1/2/ at 16 Hz, and the ambient temperature-dependent variation of the detectors response near room temperature was 0.1% K/sup -1/. The acoustic noise sensitivity measured at 100 Hz was -24 dB relative e to that of a single-domain detector.

Second-order optical nonlinearity of 10-µm-thick periodically poled LiNbO 3 films

We report on the fabrication and chic((2)) measurements of thin ~10-mum -thick films of periodically poled LiNbO(3), obtained by crystal ion slicing. The d(33) optical coefficient in the films is probed by sum-frequency generation with a short-pulse laser source at 1550 nm and compared with that of the bulk. Efficient, room-temperature TM(omega, m = 0)-to-TM(omega +omega, m = 0) mode conversion is obtained in the films. These measurements show that domain periodicity is preserved during ion implantation and that the thin films have bulklike nonlinearity and material dispersion.

Prepatterned optical circuits in thin ion-sliced single-crystal films of LiNbO 3

Crystal ion slicing was used in conjunction with conventional annealed proton exchange in Z-cut LiNbO/sub 3/ to result in prepatterned microns-thick single-crystal LiNbO/sub 3/ films with channel guides and a measured waveguide propagation loss of 0.2-0.7 dB/cm. Full optical circuit transfer, including a buffer layer and a patterned metal electrode structure for active control was demonstrated.

Hybrid-integrated polarization mode converters and low-voltage electro-optic modulators using crystal-ion-sliced LiNbO3 films

Lithium Niobate (LiNbO3) films produced by the crystal ion slicing (CIS) method are introduced in various components in use in the optical telecommunications market. The CIS technique employs high-energy ion implantation to create a narrow (~0.2 micrometers ) planar layer of localized damage, buried ~10 micrometers beneath the surface of the implanted LiNbO3 wafers. This sacrificial layer allows for slicing of microns-thick LiNbO3 films, either by selective wet chemical etching or by thermal shock. The obtained films have bulk material properties and morphology suitable for integrated optics applications. Slices of X-cut LiNbO3 were used to produce zero-order wave retarders that can be inserted in slots cut into planar lightwave circuits, resulting in TE-TM polarization mode conversion with high extinction ratio (30 dB) and low excess loss (<0.1 dB). Conventional LiNbO3 waveguide fabrication techniques were combined with the CIS process to produce CIS films of Z-cut LiNbO3 with optical circuits patterned prior to lift-off, having propagation losses typical of bulk LiNbO3 waveguides. Using thin sheets of LiNbO3, velocity- and impedance-matched modulators can be fabricated with low V(pi )L(~7.6 V.cm) and low microwave losses (0.3 db/cm.GHz1/2). The CIS film optical circuits can be integrated into hybrid systems with otherwise incompatible, yet technologically important materials platforms.

Hybrid integrated tunable optical transmitter subsystem on a chip

The need for tunable optical transmitters in optical networking is growing at a rapid rate. A tunable optical transmitter is the combination of a tunable laser, an isolator, and a modulator. Although today lasers and modulators could be integrated together on a single chip, an integrated component of this type would not be useful because the absence of an isolator between the two elements would cause optical reflections to reach the laser, leading to a high level of frequency chirp and relaxation oscillations. Therefore discrete external modulators are used, and lasers are coupled to them through discrete optical isolators. We report on recent developments in integrated active, thermo-optic, magneto-optic and electro-optic technologies that enable the production of a fully integrated tunable transmitter. This transmitter consists of a planar polymer waveguide circuit that is built on a silicon chip and in which films of a variety of materials are embedded. This subsystem on a chip includes a laser chip coupled to a thermo-optically tunable planar polymeric filter resulting in a tunable external cavity laser; an integrated magneto-optic isolator consisting of a planar polymer waveguide with inserted thin films of yttrium iron garnet for Faraday rotation, crystal ion sliced LiNbO3 for half-wave retardation, and polarizers; and an electro-optic modulator consisting of a crystal ion sliced LiNbO3 thin film patterned with a Mach-Zehnder interferometer and grafted into the polymer circuit, capable of operating with less than 5 Volts at modulation speeds up to 40 Ghz.