Wee Chong Tan

Vertically integrated As2S3 ring resonator on LiNbO3

Titanium-diffused lithium niobate (Ti:LiNbO(3)) waveguides are widely used in current fiber optic networks because of their high-speed, electro-optic modulation, and low-loss integration with standard single-mode fibers. However, they cannot achieve small ring resonators owing to their lack of a high core-to-cladding index contrast. To overcome this challenge, we vertically integrate an emerging chalcogenide glass waveguide technology on well-established Ti:LiNbO(3) waveguides. We present, to our knowledge, the first arsenic trisulfide (As(2)S(3)) race-track ring resonator with a 290.8 microm bend radius in an all-pass filter configuration, integrated on a Ti:LiNbO(3) waveguide. Vertical coupling is achieved using a unique taper design. Experimental results are shown for 10.6% coupling, 2.08 dB roundtrip loss, and a 25.4 GHz free-spectral range.

Optical characterization of a-As2S3 thin films prepared by magnetron sputtering

It is well known that thermally evaporated a-As2S3 thin films are prone to oxidation when exposed to ambient environment. These As2O3 crystals can have a devastating effect on propagating light by introducing a major source of scattering loss in submicron optically integrated circuits. Magnetron sputtering a-As2S3 not only produces films that have optical properties closer to their equilibrium state like their bulk glass counter parts, the as-deposited films also show no detectable signs of As2O3 crystals in them when they are exposed to the ambient environment. These attributes are unique to a magnetron sputtered a-As2S3 film and are probably caused by the “photoannealing” effect from the visible light emitted by the argon plasma during the sputtering process. The optical properties of a magnetron sputtered a-As2S3 film and its propagation loss on a Ti diffused LiNbO3 waveguide are reported here. The thin film results agree closely with published data on As2S3 bulk glass, and the optical properties of th...

Two-Stage Taper Enhanced Ultra-High

A hybrid optics platform consisting of LiNbO3 waveguides vertically coupled to high-index-contrast As2S3 waveguides can provide tight bend radii for ring resonators and strong tuning capability via electrical-optic effects in LiNbO3 substrate. A vertically integrated As2 S3 ring resonator having an ultranarrow free spectral range (FSR) of 0.0579 nm and side-coupled to a low-index Ti-diffused:LiNbO3 straight waveguide was designed and fabricated. Using improved design and fabrication processes, a low 1.2-dB/cm propagation loss in the ring with over 30 dB of extinction ratio was demonstrated on a fabricated 1.7-cm-long path ring resonator with a 400- μm radius, which corresponds to a calculated intrinsic quality factor-Q as high as 3.5 × 105. To our knowledge, this is the highest Q factor reported for chalcogenide ring resonator planar waveguide devices.

Q

A new waveguide platform is demonstrated that allows the bend radii to be substantially decreased for titanium-diffused lithium-niobate (LiNbO3) waveguides using vertically integrated arsenic-trisulfide (As2S3) overlay waveguides. Power is transferred from a Ti-diffused waveguide into the overlay waveguide using tapers, guided by the As2S3 waveguide through the S-bend region and transferred back into another Ti-diffused waveguide. This structure also behaves like a polarization beam splitter. We present simulation results as well as measurements to show the feasibility of achieving low loss and reduced bend radii for electrooptic waveguides.

As

Several hybrid integrated As₂S₃ Mach-Zehnder interferometers with linear tapers and grating couplers have been successfully fabricated using magnetron sputtering on LiNbO₃ substrate. It demonstrated how As₂S₃ waveguide can be integrated with the LiNbO₃ waveguide to create a hybrid interferometer for use in chalcogenide photonics. The photo-induced changes in the group and effective index of the As₂S₃ waveguide were measured and compared to values reported for films prepared by thermal evaporation. These photo-induced phenomena are found to be different from those reported for As₂S₃ bulk glass and thermally evaporated As₂S₃ film.

_{2}

A new configuration consisting of an arsenic trisulfide (As₂S₃) channel waveguide on top of an erbium (Er)-doped titanium-diffused x-cut lithium niobate (Er:Ti:LiNbO₃) waveguide has been investigated by simultaneous analytical expressions, numerical simulations, and experimentation. Both simulation and experimental results have shown that this structure can enhance the optical gain, as predicted by the analytical expressions. An As₂S₃ channel waveguide has been fabricated on top of a conventional Er:Ti:LiNbO₃ waveguide, where the higher refractive index As₂S₃ waveguide is used to pull the optical mode toward the substrate surface where the higher Er concentration yields an improved propagation gain. The relationship between the gain and As₂S₃ layer thickness has been evaluated, and the optimal As₂S₃ thickness was found by simulation and experimentation. Side integration was applied to reduce the extrapropagation loss caused by the titanium diffusion bump. The propagation gain has been improved from 1.1 to 2 dB/cm.

S

The aim of this work was to demonstrate the fabrication and characterization of erbium-doped optical waveguide amplifiers in X-cut Y-propagating lithium niobate (LiNbO3) by erbium (Er) and titanium (Ti) co-diffusion. Optical small-signal internal gains up to +0.6 dB/cm at 1531 nm were measured for the transverse electric (TE) and magnetic (TM) modes by optical pumping at 1488 nm with a coupled optical pump power of 95 mW in four different optical waveguide amplifier lengths. The Er and Ti co-diffusion process has shown adequate internal gain efficiency in dB/mW and a beneficial path for the development of LiNbO3-based integrated optical devices.