Wei-Chao Chiu

Monolithically integrated low-loss silicon photonic wires and three-dimensional tapered couplers fabricated by self-profile transformation

A subwavelength silicon photonic wire integrated with three-dimensional (3D) tapered couplers fabricated through self-profile transformation is presented. Unlike the conventional process of defining the silicon wire by etching, the profile transformation, which is induced by surface diffusion of silicon atoms during hydrogen annealing, is applied on as-etch silicon structures to make photonic wires. Additionally, this process is able to reduce sidewall roughness to be less than 1nm, substantially meliorating the unwanted scattering loss. Exploiting this technology, the authors demonstrated that the photonic wire has low propagation loss of 1.26dB∕cm and the 3D tapered coupler has coupling efficiency of 54%.

Monolithic Integration of 2-D Multimode Interference Couplers and Silicon Photonic Wires

A new technology using hydrogen annealing and thermal oxidation is proposed to fabricate a very compact 2-D multimode interference coupler monolithically integrated with two-layer silicon photonic wires. Two devices, a 1 × 1 cross-power coupler and a 1 × 22 power splitter, are presented and characterized. The experimental result shows that a 3-dB transmission bandwidth of 1.1 nm, and the on-chip coupler losses of 8.6 dB and 2.84 dB were accomplished for the 1 × 1 cross-power coupler and the 1 × 22 power splitter. This paper demonstrates the possibility of realizing 3-D photonic integration for silicon-on-insulator lightwave circuits.

Optical phase modulators using deformable waveguides actuated by micro-electro-mechanical systems

An optical phase modulator is presented by using micro-electro-mechanical systems to actuate deformable silicon waveguides. Via mechanically stretching the waveguide length, the optical path is extended, resulting in a phase shift. The experimental results show that a phase shift of near 0.4π is achieved at 200 V for both TE- and TM-polarized waves by cascading six phase modulation units, agreeing well with the theoretical prediction. The power consumption is estimated to be smaller than 0.2 mW at 200 V, mainly resulting from the leakage current.

Fabrication of Low-Loss Silicon Photonic Wires by Self-Profile Transformation and Applications in 3-D Photonic Integration and Nonlinear Optics

A new technology using self-profile transformation is introduced to make subwavelength silicon photonic wires with very smooth surface. Due to the smooth surface, the propagation loss was measured to be as low as 1.26 dB/cm. Moreover, 2-D beam spot-size converters and 2-D multimode interference couplers were demonstrated to monolithically integrate the photonic wires, showing the possibility of 3-D photonic integration. Owing to the low-insertion loss of the wires, various nonlinear optical processes such as four-wave mixing and spontaneous Raman emission were observed with low-pump power of just tens of milliwatts.

Monolithic integration of three-dimensional multimode interference couplers with silicon photonic wires via self-profile transformation

A novel 3-D MMI coupler with silicon photonic wires is demonstrated using self-profile transformation for the first time. The preliminary simulation results show the low excess loss of 0.27 dB.

Low-Loss Silicon Wire Waveguides with 3-D Tapered Couplers Fabricated by Self Profile Transformation

A novel low-loss silicon wire waveguide as well as 3-D tapered couplers is demonstrated by self profile transformation for the first time. The preliminary experimental results show the propagation loss is 2 dB/cm and the coupler loss is 2.7 dB.

Micro-particle transport manipulation by guided-wave optical interference

In this paper, we demonstrate that micro-particle is able to be transported by two types of integrated photonic devices; one is directional couplers and the other is multimode interferometers. Micro-particles are propelled by the evanescent wave and guided by the interference pattern of optical field inside the devices. By properly designing the device length and operation wavelength, micro-particles can be switched to either one of the output ports connecting the devices.