# Recent Progress in on‐Demand Transfer‐Enabled Integration of Wavelength‐Scale Light Sources

## TL;DR

This paper reviews recent advances in using micro-transfer-printing to integrate tiny light sources onto photonic circuits for faster data processing.

## Contribution

A novel micro-transfer-printing method enables precise, on-demand placement of microlasers and optical components on photonic chips.

## Key findings

- Micro-transfer-printing allows deterministic placement of optical structures with sub-micrometer precision.
- The technique supports integration of diverse light sources like microring lasers and quantum dots onto compact photonic platforms.
- PDMS-assisted printing is shown to overcome previous integration challenges and improve device performance.

## Abstract

The growing demand for massive and high‐speed data processing within compact photonic circuits has highlighted a critical challenge: the efficient integration of high‐quality ultrasmall light sources and emitters onto next‐generation integration platforms. Despite notable advancements achieved through conventional and cutting‐edge strategies, integration technologies utilizing the micro‐transfer‐printing technique—employing microstructured polymeric stamps, such as polydimethylsiloxane (PDMS)—have garnered considerable attention. This innovative approach facilitates heterogeneous integration by enabling the deterministic placement of micro‐ and nanoscale optical structures and materials with sub‐micrometer alignment onto diverse photonic integration platforms. This review paper presents recent developments in the micro‐transfer‐enabled integration of light sources across four representative categories of devices and materials: microdisk and microring cavity lasers, photonic crystal nanobeam lasers, semiconductor nanowire lasers and LEDs, and quantum light sources based on semiconductor quantum dots and localized emitters in two‐dimensional materials. For each category of light source integration, we analyze the application of micro‐transfer‐printing in relation to the overall integration configuration, the desired optical properties, device performance optimization, and resolution of challenges and limitations encountered in previous methodologies. Collectively, these demonstrations position PDMS‐assisted micro‐transfer‐printing not merely as a fabrication technique but as an innovative integration paradigm that connects diverse material systems and device architectures.

A novel integration technology using micro‐transfer‐printing, demonstrating individually and selectively addressable pick‐up of a microlaser on a growth wafer and on‐demand integration at a predetermined location on the compact PIC chip.