Tomoyuki Izuhara

Magneto-optical nonreciprocal phase shift in garnet/silicon-on-insulator waveguides

We demonstrate the integration of a single-crystal magneto-optical film onto thin silicon-on-insulator (SOI) waveguides by use of direct wafer bonding. Simulations show that the high confinement and asymmetric structure of SOI allows an enhancement of approximately 3x over the nonreciprocal phase shift achieved in previous designs; this value is confirmed by our measurements. Our structure will allow compact magneto-optical nonreciprocal devices, such as isolators, integrated on a silicon waveguiding platform.

Single-crystal barium titanate thin films by ion slicing

Thin barium titanate films, 0.5–8 μm thick, are obtained from a single-crystal bulk sample using ion slicing. The process, based on ion implantation and anodic bonding, separates thin films having areas of ∼1×1 cm2, from bulk crystals. The quality of the film is characterized by measurement of surface roughness and dielectric properties. The film permittivity retains its single-crystal value.

Direct wafer bonding and transfer of 10-μm-thick magnetic garnet films onto semiconductor surfaces

Bonding between liquid-phase-epitaxy-grown yttrium iron garnet films and various semiconductors is realized by direct wafer bonding. The semiconductor substrates can serve as a platform for integration or as a “handle” platform for the transfer of mesoscopic garnet films. To effect film transfer, a sacrificial layer is formed in the garnet by deep ion implantation prior to bonding. Shear stress at the garnet/semiconductor interface can be controlled by temperature tuning during the bonding process. A debonding temperature threshold of ∼400 °C is found and related to the interfacial thermal stress due to difference in thermal expansion coefficients of the bonded materials. Film separation is realized by the application of thermally induced stress at the sacrificial layer.

Low-loss crystal-ion-sliced single-crystal potassium tantalate films

The dielectric response has been studied in 10-μm-thick, single-crystal potassium tantalate films formed by crystal ion slicing. Scanning microwave microscopy shows that the implanted, pre-etched samples exhibit a bulk-like permittivity and low-loss tangent (0.0009) at 1.7 GHz. The separated free-standing films have somewhat higher loss tangents due to residual-ion-induced stress. Selective relaxation of this stress by etching or annealing reduces the dielectric loss.

Integration of magnetooptical waveguides onto a III-V semiconductor surface

Optical waveguides fabricated on a yttrium iron garnet (YIG) substrate are integrated onto a semiconductor surface by using ridge waveguides patterned onto a prefabricated recess in the YIG surface. The recess separates the waveguides from the semiconductor substrate with an air-gap. This structure makes it possible to avoid coupling light within the YIG waveguides into the semiconductor substrate which has a higher refractive index. The excess optical loss due to the coupling can be as low as /spl les/0.1 dB/cm with a 1-/spl mu/m-wide air-gap. The calculated coupling loss is confirmed by comparing the guided TE and TM modes.

Integrable wide-free-spectral-range Fabry–Perot optical filters using free-standing LiNbO 3 thin films

We demonstrate the use of free-standing thin films of a complex oxide for chip-scale optical filtering. The films are used as low-order etalons with very large free spectral ranges that exceed 6.78 THz (> 50 nm at 1550 nm) and use a small chip area (< 500 microm2) when they are integrated. The films are produced by crystal ion slicing; this process exfoliates a micrometers-thin layer of single-crystal optical material from a bulk parent by means of high-energy-ion implantation. The etalons, which are 10 microm thick with Ag deposited on both surfaces, are integrated into a silica-on-silicon waveguide block.

Fabrication of patterned single-crystal SrTiO3 thin films by ion slicing and anodic bonding

A new technique for directly fabricating patterned thin films (<1μm thick) of fully single-crystal strontium titanate uses deep H+ implantation into the oxide sample, followed by anodic bonding of the sample to a Pyrex or Pyrex-on-Si substrate. The dielectric properties and crystal structure of such thin films are characterized and are found to be essentially those of the bulk single crystal.

The integration of silica and polymer waveguide devices for ROADM applications

We report on our efforts to integrate silica and polymer waveguide devices, such as arrayed waveguide gratings (AWGs), tunable lenses, optical switches, variable optical attenuators (VOAs), power taps. In particular, the realizations of various optical add/drop multiplexers and tunable dispersion compensators are discussed. The integration techniques, the design architectures and the corresponding optical performances are presented.

Photonic integrated circuits based on silica and polymer PLC

Various methods of hybrid integration of photonic circuits are discussed focusing on merits and challenges. Material platforms discussed in this report are mainly polymer and silica. We categorize the hybridization methods using silica and polymer waveguides into two types, chip-to-chip and on-chip integration. General reviews of these hybridization technologies from the past works are reviewed. An example for each method is discussed in details. We also discuss current status of our silica PLC hybrid integration technology.

Extremely thin, single-crystal films of LiNbO/sub 3/ fabricated using localized He+ ion-implantation

We demonstrate that extremely thin, i.e., /spl sim/2-3/spl mu/m, single-crystal films of LiNbO/sub 3/ can be formed on a wafer using patterned ion-implantation followed by chemical etching. Control of the membrane thickness and its waveguiding properties are demonstrated.