Optical microfluidic waveguides and solution lasers of colloidal semiconductor quantum wells

Microfluidics has become an important technology platform offering many applications including point-of-care systems, lab-on-a-chip (LOC) devices, and drug delivery and separation. For this technology to reach its full potential, many improvements and components are being heavily researched and utilized to help broaden the range of its applications. One such important application is the implementation of lasers in microfluidic networks. Microfluidic lasers are being employed as sensors and light sources for use in chemical and biological reaction promoting and flow cytometry. Microfluidic amplified spontaneous emission (ASE) and lasing using fluorescent dyes embedded in liquid-liquid waveguides has been previously reported. The performance of these devices may be significantly improved using colloidal semiconductor quantum wells, also known as nanoplatelets (NPLs), which possess optical properties desirable for lasing. In this work, different than previous works, optical microfluidic waveguides and solution lasers of NPLs are proposed and demonstrated. To this end, a Fabry-P´erot cavity is created in a microfluidic channel encapsulated with polydimethylsiloxane (PDMS) to achieve in-solution lasing with NPLs. The microfluidic devices are fabricated using soft lithography and implemented as a platform for observing optical gain from NPLs. Because of its many advantages over other materials for microfluidic devices, such as its ease of fabrication, solvent compatibility, transparency and availability, PDMS is chosen as the base material for our microfluidic device. Combined with the desirable optical properties of the NPLs, PDMS can provide easy integration of laser media into flexible microfluidic networks. Using capillary as well as pressure-driven flows, record low optical gain thresholds were achieved. Using capillary forces, single-mode lasing was demonstrated on an on-chip Fabry-P´erot cavity from red-emitting NPLs. The use of pressure-driven flow allowed for the observation of gain from a liquid-liquid waveguide. These microfabricated NPL solution lasers have the potential to provide compact and inexpensive coherent light sources for applications in microfluidics and integrated optics.