Automated Nanoscale Absolute Accuracy Alignment System for Transfer Printing

20 µm Micro-LEDs Mass Transfer via Laser-Induced In Situ Nanoparticles Resonance Enhancement

Ultrafast laser is expected as a promising strategy for micro-LEDs (µ-LEDs) transfer due to its inherent property of suppressing thermal effects. However, its ultrahigh peak power and the unclear transfer mechanism make its transfer quality and efficiency unsatisfactory. Here, the study reports the high-precision mass transfer of 20 µm fine-pitch µ-LEDs via in situ nanoparticles (NPs) resonance enhancement in burst mode ultraviolet picosecond laser irradiation. This technique suppresses the thermal melting effect and rapid cooling behavior of plasma by temporal modulation of the burst mode, generating NPs-induced resonance enhancement that accurately and controllable drives a single unit up to tens of thousands of µ-LEDs. The transfer of large µ-LED arrays with more than 180 000 chips is also demonstrated, showing a transfer yield close to 99.9%, a transfer speed of 700 pcs s-1, and a transfer error of <±1.2 µm. The transferred µ-LEDs perform excellent optoelectronic properties and enable reliable device operation regardless of complex strain environments, providing a reliable strategy for preparing broader classes of 3D integrated photonics devices.

Machine Learning Inspired Nanowire Classification Method based on Nanowire Array Scanning Electron Microscope Images

Background

This article introduces an innovative classification methodology to identify nanowires within scanning electron microscope images.

Methods

Our approach employs advanced image manipulation techniques in conjunction with machine learning-based recognition algorithms. The effectiveness of our proposed method is demonstrated through its application to the categorization of scanning electron microscopy images depicting nanowires arrays.

Results

The method's capability to isolate and distinguish individual nanowires within an array is the primary factor in the observed accuracy. The foundational data set for model training comprises scanning electron microscopy images featuring 240 III-V nanowire arrays grown with metal organic chemical vapor deposition on silicon substrates. Each of these arrays consists of 66 nanowires. The results underscore the model's proficiency in discerning distinct wire configurations and detecting parasitic crystals. Our approach yields an average F1 score of 0.91, indicating high precision and recall.

Conclusions

Such a high level of performance and accuracy of ML methods demonstrate the viability of our technique not only for academic but also for practical commercial implementation and usage.

Additive GaN Solid Immersion Lenses for Enhanced Photon Extraction Efficiency from Diamond Color Centers

Effective light extraction from optically active solid-state spin centers inside high-index semiconductor host crystals is an important factor in integrating these pseudo-atomic centers in wider quantum systems. Here, we report increased fluorescent light collection efficiency from laser-written nitrogen-vacancy (NV) centers in bulk diamond facilitated by micro-transfer printed GaN solid immersion lenses. Both laser-writing of NV centers and transfer printing of micro-lens structures are compatible with high spatial resolution, enabling deterministic fabrication routes toward future scalable systems development. The micro-lenses are integrated in a noninvasive manner, as they are added on top of the unstructured diamond surface and bonded by van der Waals forces. For emitters at 5 μm depth, we find approximately 2× improvement of fluorescent light collection using an air objective with a numerical aperture of NA = 0.95 in good agreement with simulations. Similarly, the solid immersion lenses strongly enhance light collection when using an objective with NA = 0.5, significantly improving the signal-to-noise ratio of the NV center emission while maintaining the NV's quantum properties after integration.

Integrating a Nanowire Laser in an on-Chip Photonic Waveguide

We report a simple and facile integration strategy of a laser source in passive photonic integrated circuits (PICs) by deterministically embedding semiconductor nanowires (NWs) in waveguides. InP NWs laid on a SiN slab are buried by a polymer layer which also acts as an electron-beam resist. With electron-beam lithography, hybrid polymer-SiN waveguides are formed with precisely embedded NWs. The lasing behavior of the waveguide-embedded NWs is confirmed, and more importantly, the NW lasing mode couples into the hybrid waveguide and forms an in-plane guiding mode. Multiple waveguide-embedded NW lasers are further integrated in complex photonic structures to illustrate that the waveguiding mode supplied by the NW lasers could be manipulated for on-chip signal processing, including power splitting and wavelength-division multiplexing. This integration strategy of an on-chip laser is applicable to other PIC platforms, such as silicon and lithium niobate, and the top cladding layer could be changed by depositing SiN or SiO₂, promising its CMOS compatibility.

High precision integrated photonic thermometry enabled by a transfer printed diamond resonator on GaN waveguide chip

We demonstrate a dual-material integrated photonic thermometer, fabricated by high accuracy micro-transfer printing. A freestanding diamond micro-disk resonator is printed in close proximity to a gallium nitride on a sapphire racetrack resonator, and respective loaded Q factors of 9.1 × 10⁴ and 2.9 × 10⁴ are measured. We show that by using two independent wide-bandgap materials, tracking the thermally induced shifts in multiple resonances, and using optimized curve fitting tools the measurement error can be reduced to 9.2 mK. Finally, for the GaN, in a continuous acquisition measurement we record an improvement in minimum Allan variance, occurring at an averaging time four times greater than a comparative silicon device, indicating better performance over longer time scales.