Shih-Hsiang Hsu

Ultrahigh vacuum chemically assisted ion beam etching system with a three grid ion source

A chemically assisted ion beam etching system has been developed which performs high quality, highly anisotropic etching of AlGaAs/GaAs at relatively low ion energies (200 eV). The use of three grid ion optics in a Kaufman ion source allows etching at low energies with reasonable rates without loss of profile verticality. All ultrahigh vacuum etching chamber construction with a high throughput turbomolecular pump and high vacuum loadlock provide routine high quality etching of AlGaAs without the use of etch chamber cryo panels or cryo pumps. Low ion energy and a clean vacuum environment permit the use of a single level, non hard baked photoresist mask. Benefits include high pattern resolution and fidelity, low mask erosion rate, good dimensional control, and easy, complete mask stripping as well as reduced substrate damage.

Etch‐mask of pyrolytic‐photoresist thin‐film for self‐aligned fabrication of smooth and deep faceted three‐dimensional microstructures

Etch‐mask thin‐film material that is particulate‐free and topographically smooth has been created from a standard photoresist spun onto standard semiconductor substrates such as gallium arsenide, indium phosphide, and silicon, and then pyrolyzed by exposing to a temperature of 300 °C in air atmosphere for 1 min on a standard laboratory hot‐plate. The resulting pyrolytic‐photoresist thin‐film is chemically inert to many standard organic solvents including the solvent of photoresist itself and to many inorganic reagents used in semiconductor processing. Therefore the pyrolytic‐photoresist can be patterned by sulfur hexafluoride reactive ion etching via a standard photoresist mask. Upon stripping the standard photoresist in a mixture of 1:1/acetone:developer agitated ultrasonically, the remaining patterned pyrolytic‐photoresist performs as an excellent etch‐mask in chemically assisted ion beam etching and reactive ion etching systems. Thus it can be a key material in the multilayer masking technique used to ...

Mycobacterium tuberculosis DNA Detection Using Surface Plasmon Resonance Modulated by Telecommunication Wavelength

A surface plasmon resonance sensor for Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) is developed using repeatable telecommunication wavelength modulation based on optical fiber communications laser wavelength and stability. MTB DNA concentrations of 1 μg/mL and 10 μg/mL were successfully demonstrated to have the same spectral half-width in the dip for optimum coupling. The sensitivity was shown to be −0.087 dB/(μg/mL) at all applied telecommunication wavelengths and the highest sensitivity achieved was 115 ng/mL without thiolated DNA immobilization onto a gold plate, which is better than the sensor limit of 400 ng/mL possible with commercial biosensor equipment.

Waveguide coupled photodiode using reflector and metal coplanar waveguide for optical triplexing applications

The monitoring photodiode is the key building block for an optical triplexer at wavelengths of 1310, 1490, and 1550 nanometers. The InGaAs/InP photodetectors were proposed and fabricated to be monolithi-cally integrated with AlGaAs/GaAs optical waveguides using total internal reflection coupling. The metal coplanar waveguides on top of the polyimide planarization and passivation layer were then connected to illustrate the high speed monitoring functions. The full width half maximum of the temporal response and 3-dB bandwidth for the optical waveguide coupled photodiodes demonstrated 29.5 ps and 11 GHz, respectively. The bit error rate performance of this integrated photodiode at 10 Gbit/s with 2(7)-1 long pseudo-random bit sequence NRZ input data also showed error-free operation.

Surface Plasmon Resonator Using High Sensitive Resonance Telecommunication Wavelengths for DNA Sensors of Mycobacterium Tuberculosis with Thiol-Modified Probes

Various analytes can be verified by surface plasmon resonance, thus continuous improvement of this sensing technology is crucial for better sensing selection and higher sensitivity. The SPR sensitivity on the wavelength modulation is enhanced with increasing wavelengths. The telecommunication wavelength range was then utilized to detect Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) under two situations, without immobilization and with 5′-thiol end labeled IS6100 DNA probes, for SPR sensitivity comparison. The experimental data demonstrated that the SPR sensitivity increased more than 13 times with the wavelength modulation after immobilization. Since the operating wavelength accuracy of a tunable laser source can be controlled within 0.001 nm, the sensitivity and resolution on immobilized MTB DNA were determined as 1.04 nm/(μg/mL) and 0.9 ng/mL, respectively.

Polarization-dependent loss compensation on silicon-wire waveguide tap by complex refractive index of metals

A photodetector can be applied onto a silicon-wire waveguide tap to monitor light signals on waveguides. To meet the complexity of optical integrated circuits, the proposed photodetector would be positioned onto a wafer base instead of being employed and terminated at the edge end of an optical component. Because the silicon-wire-based optical directional coupler shows an undesirably high level of polarization-dependent loss on the tap port compared with the primary port, the complex refractive index of the reflective metal layer was proposed integrated into the direction-changing tap region, made using a 54.7 degrees angle from anisotropic silicon wet etching. This structure compensates for the polarization dependent loss of the tapping signal power for the primary port monitoring.

MicroRNA Biosensing Using Telecommunication Wavelength-Interrogated Waveguide-Coupled Surface Plasmon Resonance

The surface plasmon resonance (SPR) detection for very small molecules, such as cancer diagnosis microRNA (miRNA), is very challenging. Due to the high precision and stability control in optical fiber communications, the telecommunication wavelength was interrogated to detect 21-mer DNA from several-nanometer long miRNA for high sensitivity and high resolution through waveguide-coupled SPR.

A Simple Optical Interconnection Integrated with Low Birefringence Silicon-on-insulator Waveguide

5 mum thick silicon-on-insulator waveguide was demonstrated to low birefringence of 4.6times10-5. Instead of complex processing from 3D mode size converter, the high numerical aperture fiber was utilized as the bridge between corresponding waveguide and SMF-28 fiber to get competitively coupling loss of 0.4 dB.

Biosensing Using Microring Resonator Interferograms

Optical low-coherence interferometry (OLCI) takes advantage of the variation in refractive index in silicon-wire microring resonator (MRR) effective lengths to perform glucose biosensing using MRR interferograms. The MRR quality factor (Q), proportional to the effective length, could be improved using the silicon-wire propagation loss and coupling ratio from the MRR coupler. Our study showed that multimode interference (MMI) performed well in broad band response, but the splitting ratio drifted to 75/25 due to the stress issue. The glucose sensing sensitivity demonstrated 0.00279 meter per refractive-index-unit (RIU) with a Q factor of ∼30,000 under transverse electric polarization. The 1,310 nm DFB laser was built in the OLCI system as the optical ruler achieving 655 nm characterization accuracy. The lowest sensing limitation was therefore 2 × 10−4 RIU. Moreover, the MRR effective length from the glucose sensitivity could be utilized to experimentally demonstrate the silicon wire effective refractive index with a width of 0.45 μm and height of 0.26 μm.

Birefringence characterization on SOI waveguide using optical low coherence interferometry

An optical low-coherence interferome-try was utilized to characterize the birefringence on 5-µm thick silicon-on-insulator waveguides. The SMF-28 fiber was taken as a baseline to demonstrate 2.6×10⁻³ waveguide birefringence with 5-µm width and 2.5-µm etch depth.