Po-Tsung Lee

This study demonstrates an end-coupling configuration that integrates a III–V slotted nanobeam (NB) laser into an air-clad silicon-on-insulator waveguide. This integration is realized by simultaneously assembling and wedging two identical NBs into a waveguide notch in a single step via a mechanically guided transfer-printing technique. The assembled NB features a novel nanoslot with a V-shaped cross-section and a minimum width of approximately 6 nm, enabling extreme field concentration at the slot opening─a characteristic highly beneficial for enhancing light–matter interaction with the surrounding media. By incorporating reduced lattice periods on the NBs and a multimode interference (MMI) coupler design on the silicon waveguide, a theoretical unidirectional coupling efficiency exceeding 80% is achieved for the V-slotted mode. Statistical analysis across multiple devices confirms uniformly high laser emission coupling into the silicon waveguides within the MMI coupling bandwidth. Furthermore, we investigate the impact of various transfer-printing misalignments on the coupling, confirming its robustness and uniformity within the achievable tolerances of our process. These findings provide a reliable approach to implementing slotted active devices in silicon-based photonic circuits, offering significant advantages for diverse applications requiring enhanced light–matter interactions.

This work presents, to our knowledge, a novel hybrid integration in an end-coupling configuration by directly wedging III-V photonic crystal nanobeam (NB) lasers into silicon-based waveguides. The nanocavity, featuring a reduced lattice period on one side, achieves a theoretical unidirectional coupling efficiency exceeding 92% into the silicon waveguide without requiring additional mode converters. By employing a highly accurate transfer printing technique assisted by two-dimensional mechanical guidance, this wedging configuration exhibits highly unidirectional coupling from the NB lasers into the silicon-based waveguides, along with low wavelength dependence and significant tolerance to transfer printing misalignments. Furthermore, wedging the NB lasers into single and double U-bend waveguides with long propagation lengths produces significant planar emission, thereby initially confirming the feasibility of this configuration as a nano-light source for photonic circuits.

In this study, we developed 1D photonic crystal (PhC) nano-light emitters embedded in a polydimethylsiloxane thin film approximately 15 m thick. By attaching this film to a piezoelectric substrate of polyvinylidene fluoride (PVDF), we achieved a reversible emission wavelength shift of 1.4 nm in response to bending induced by the PVDF substrate, with an applied voltage of 80 V. Additionally, we demonstrated a significant wavelength tuning range exceeding 22 nm and stable tuning across various voltage levels. This work presents what we believe is a novel laminated configuration for mechanically tuning the wavelength of PhC nano-light emitters, highlighting its potential applications in flexible photonics.

The integration of thick homoepitaxial layers on silicon carbide (SiC) substrates is critical for enabling high-voltage power devices, yet it remains challenged by substrate surface quality and wafer geometry evolution. This study investigates the relationship between substrate preparation—particularly chemical mechanical planarization (CMP)—and the impact on wafer bow, total thickness variation (TTV), local thickness variation (LTV), and defect propagation during epitaxial growth. Seven 150 mm, 4° off-axis, prime-grade 4H-SiC substrates from a single ingot were processed under high-volume manufacturing (HVM) conditions and grown with epitaxial layers ranging from 12 μm to 100 μm. Metrology revealed a strong correlation between increasing epitaxial thickness and geometric deformation, especially beyond 31 μm. Despite initial surface scratches from CMP, hydrogen etching and buffer layer deposition significantly mitigated scratch propagation, as confirmed through defect mapping and SEM/FIB analysis. These findings provide a deeper understanding of the substrate-to-epitaxy integration process and offer pathways to improve manufacturability and yield in thick-epilayer SiC device fabrication.

Revolutionizing semiconductor fabrication, ALD, ALE, and NBE deliver atomic-scale precision, driving unprecedented performance and scalability in next-generation miniaturized devices.

We propose and realize a 1D photonic crystal nanocavity laser embedded in a polydimethylsiloxane (PDMS) thin film. The nanolaser in PDMS exhibits a significant optical response to structural deformation. It can be attached to object surfaces or integrated into different configurations, enabling the detection of different quantities that induce strain in the film. In experiments, this nanolaser can detect temperature variations or micrometer-scale bending degrees by attaching it to a temperature-controllable or bendable plate, respectively. Moreover, we further utilize the film as a diaphragm of a chamber to demonstrate its potential as a highly sensitive pressure gauge and chemical sensor. By adjusting the thickness of the PDMS thin film and the position of the nanolaser, we experimentally achieved a minimum detectable gas pressure variation of 0.12 kPa and a sensing dynamic range of 46 dB. We also investigate the optical response of the nanolaser to the swelling of the PDMS thin film induced by different organic solvents in experiments. The experimental wavelength shift rates over time are proportional to different chemical vapors’ PDMS swelling ratios, which can be used to identify specific chemical vapors within the chamber that induce PDMS swelling. Based on the experimental results and the capability of reattaching to different objects or configurations, we believe that our PhC nanolaser demonstrated herein holds significant potential as a highly sensitive mechanical and chemical sensor.

In this report, we introduce a 1D photonic crystal (PhC) nanocavity with waveguide-like strain amplifiers within a soft polydimethylsiloxane substrate, presenting it as a potential candidate for highly sensitive pressure and position optical sensors. Due to its substantial optical wavelength response to uniform pressure, laser emission from this nanocavity enables the detection of a minimum applied uniform pressure of 1.6‰ in experiments. Based on this feature, we further studied and elucidated the distinct behaviors in wavelength shifts when applying localized pressure at various positions relative to the PhC nanocavity. In experiments, by mapping wavelength shifts of the PhC nanolaser under localized pressure applied using a micro-tip at different positions, we demonstrate the nanocavity’s capability to detect minute position differences, with position-dependent minimum resolutions ranging from tens to hundreds of micrometers. Furthermore, we also propose and validate the feasibility of employing the strain amplifier as an effective waveguide for extracting the sensing signal from the nanocavity. This approach achieves a 64% unidirectional coupling efficiency for leading out the sensing signal to a specific strain amplifier. We believe these findings pave the way for creating a highly sensitive position-sensing module that can accurately identify localized pressure in a planar space.