Che-Yun Lin

On-chip methane sensing by near-IR absorption signatures in a photonic crystal slot waveguide

We demonstrate a 300 μm long silicon photonic crystal (PC) slot waveguide device for on-chip near-infrared absorption spectroscopy, based on the Beer-Lambert law for the detection of methane gas. The device combines slow light in a PC waveguide with high electric field intensity in a low-index 90 nm wide slot, which effectively increases the optical absorption path length. A methane concentration of 100 ppm (parts per million) in nitrogen was measured.

Effective in-device r 33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides

We design and fabricate a 320 nm slot for an electro-optic (E-O) polymer infiltrated silicon photonic crystal waveguide. Because of the large slot width, the poling efficiency of the infiltrated E-O polymer (AJCKL1/amorphous polycarbonate) is significantly improved. When coupled with the slow light effect from the silicon photonic crystal waveguide, an effective in-device r(33) of 735 pm/V, which to our knowledge is a record high, is demonstrated, which is ten times higher than the E-O coefficient achieved in thin film material. Because of this ultrahigh E-O efficiency, the V(π)L of the device is only 0.44 V mm, which is to our knowledge the best result of all E-O polymer modulators.

Electro-optic polymer infiltrated silicon photonic crystal slot waveguide modulator with 23 dB slow light enhancement

A silicon/organic hybrid modulator integrating photonic crystal (PC) waveguide, 75 nm slot, and electro-optic (EO) polymer is experimentally demonstrated. Slow light in PC waveguide and strong field confinement in slot waveguide enable ultraefficient EO modulation with a record-low Vπ×L of 0.56 V mm and an in-device effective r33 of 132 pm/V. This result makes it the most efficient EO polymer modulator demonstrated to date. The modulated signal shows strong wavelength dependence and peak enhancement of 23 dB near the band edge of defect mode, which confirms the signature of the slow light effect.

Spontaneous emission from planar microstructures

Abstract The alteration of spontaneous emission characteristics in terms of the spontaneous lifetime and spectral emission characteristics are discussed for dipoles in the presence of nearby planar reflecting interfaces and cavities, specifically for the case of semiconductors. For dipoles closely spaced to absorbing metal mirrors, significant lifetime change is possible. Analysis and experimental data are presented for light emitting diodes. For dielectric Fabry-Perot microcavities, the expected lifetime change is small, but significant modification in the radiation pattern of the emitted light occurs. It is shown that the spectral characteristics of emission have a sensitive dependence on the dipole location in the cavity. Comparison is made between a classical against a quantum treatment of the spontaneous emission modification due to the cavity.

Photonic crystal slot waveguide absorption spectrometer for on-chip near-infrared spectroscopy of xylene in water

We experimentally demonstrate a 300 μm long silicon photonic crystal slot waveguide near-infrared absorption spectrometer. Based on Beer–Lambert absorption law, our on-chip absorption spectrometer combines slow light in a photonic crystal waveguide with a high electric field intensity in a low-index 75 nm wide slot, which effectively increases the optical absorption path length of the analyte. We demonstrate near-infrared absorption spectroscopy of xylene in water, with a polydimethyl siloxane sensing phase for xylene extraction from water. Xylene concentrations up to 100 ppb (parts per billion) (86 μg/l) in water were measured.

Highly Linear Broadband Optical Modulator Based on Electro-Optic Polymer

In this paper, we present the design, fabrication, and characterization of a traveling-wave directional coupler modulator based on electro-optic polymer, which is able to provide both high linearity and broad bandwidth. The high linearity is realized by introducing Δβ -reversal technique in the two-domain directional coupler. A traveling-wave electrode is designed to function with bandwidth-length product of 302 GHz·cm , by achieving low microwave loss, excellent impedance matching, and velocity matching, as well as smooth electric-field profile transformation. The 3-dB bandwidth of the device is measured to be 10 GHz. The spurious-free dynamic range of 110 dB ±3 Hz2/3 is measured over the modulation frequency range of 2-8 GHz. To the best of our knowledge, such high linearity is first measured at the frequency up to 8 GHz. In addition, a 1 × 2 multimode interference 3-dB splitter, a photobleached refractive index taper, and a quasi-vertical taper are used to reduce the optical insertion loss of the device.

High dynamic range electric field sensor for electromagnetic pulse detection

We design a high dynamic range electric field sensor based on domain inverted electro-optic (E-O) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices. Experimental results demonstrate effective detection of electric field from 16.7V/m to 750KV/m at a frequency of 1GHz, and spurious free measurement range of 70dB.

Wideband group velocity independent coupling into slow light silicon photonic crystal waveguide

We experimentally demonstrate efficient optical coupling into a slow light photonic crystal waveguide (PCW) that is independent of the group velocity of the guided mode. With a group index taper to match the group velocity between a strip waveguide and a PCW, the optical coupling efficiency is nearly constant throughout the spectrum of the defect-mode, including the slow light region near the band edge. Compared to strip-PCW butt-coupling without a group index taper, our measurement results show a 20 dB enhancement in coupling efficiency with 5 dB less Fabry–Perot fluctuations. The measurements show excellent agreement with two-dimensional finite-difference time domain simulations.

Methods to array photonic crystal microcavities for high throughput high sensitivity biosensing on a silicon-chip based platform

We experimentally demonstrate a method to create large-scale chip-integrated photonic crystal sensor microarrays by combining the optical power splitting characteristics of multi-mode interference (MMI) power splitters and transmission drop resonance characteristics of multiple photonic crystal microcavities arrayed along the length of the same photonic crystal waveguide. L13 photonic crystal microcavities are employed which show high Q values (~9300) in the bio-ambient phosphate buffered saline (PBS) as well as high sensitivity, experimentally demonstrated to ~98 atto-grams. Two different probe antibodies were specifically detected simultaneously with a control sample, in the same experiment.

Large optical spectral range dispersion engineered silicon-based photonic crystal waveguide modulator.

We present a dispersion engineered slow light silicon-based photonic crystal waveguide PIN modulator. Low-dispersion slow light transmission over 18 nm bandwidth under the silica light line with a group index of 26.5 is experimentally confirmed. We investigate the variations of the modulator figure of merit, V(π) × L, as a function of the optical carrier wavelength over the bandwidth of the fundamental photonic crystal waveguide defect mode. A large signal operation with a record low maximum V(π )× L of 0.0464 V · mm over the low-dispersion optical spectral range is demonstrated. We also report the device operation at 2 GHz.