University of Strathclyde, UK, has developed technique to be able to perform nanoscale transfer printing that can be leveraged for visible light communications, flexible optoelectronics, and photonic integrated circuits

Semiconductor nanowires, with lasing emission at room temperature, can be transferred in a controlled way to specific locations on diverse substrates and organized into bespoke spatial patterns.

Semiconductor nanowire (NW) lasers provide coherent light sources with highly localized emission and extremely small footprints. Such lasers may thus have the potential to revolutionize the field of photonics. Indeed, NW lasers are expected to play a key role in future optoelectronic systems, i.e., with applications in nanophotonic integrated circuits for on-chip communications and computing, in ultrasmall laser sensors for healthcare, and in light-cell interfaces for biological sciences. The extremely small dimensions of NW lasers, however, mean that it is technologically challenging to accurately manipulate and integrate them into functional systems. Their transition from laboratory environments to real-life, industrially relevant products is thus limited.

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In the past, several approaches have been proposed for the manipulation of NWs. These include optical tweezers, Langmuir-Blodgett assembly processes, the use of microscope probes, or contact printing techniques. All these techniques, however, have associated problems. For example, the NWs must be in solution, complex equipment is required, they provide reduced positioning accuracy, they do not allow individual NWs to be manipulated, or heterogeneous NWs cannot be integrated within the same system. The precise, simple, and efficient manipulation of single-NW lasers is thus still to be realized.

At the Institute of Photonics (IOP) of the University of Strathclyde, UK, we have thus developed a new technique—known as nanoscale transfer printing (nano-TP)—to tackle the challenge of single-NW laser manipulation. Transfer printing technology (originally introduced by John Rogers at the University of Illinois) involves the use of polymer stamps to capture semiconductor structures in a controlled manner and to subsequently release them onto diverse substrates. This approach provided a revolutionary platform for hybrid fabrication of a wide range of novel optoelectronic systems (e.g., semiconductor lasers printed on silicon substrates and LEDs printed on flexible and diamond substrates). In turn, these systems had a large impact in many different technologies, such as visible light communications, flexible optoelectronics, and photonic integrated circuits.

In our nano-TP technique we use bespoke polymer microstamps (μ-stamps), which have reduced dimensions and controlled shapes, to capture/release indium phosphide (InP) NW lasers. To fabricate (at the Australian National University) the NW lasers we used in our work, we grew vertically aligned InP NWs on an InP substrate, . Before performing our nano-TP study, we removed the NWs from the growth substrate and used mechanical means to randomly scatter them onto a silicon (Si) substrate. The final lasers have a lasing emissionat room temperature in the ∼840–890nm wavelength range.

Credit : University of Strathclyde, UK