Abstract
Although multiphoton-pumped lasing from a solution of chromophores is important in the emerging fields of nonlinear optofluidics and bio-photonics, conventionally used organic dyes are often rendered unsuitable because of relatively small multiphoton absorption cross-sections and low photostability. Here, we demonstrate highly photostable, ultralow-threshold multiphoton-pumped biexcitonic lasing from a solution of colloidal CdSe/CdS nanoplatelets within a cuvette-based Fabry–Pérot optical resonator. We find that colloidal nanoplatelets surprisingly exhibit an optimal lateral size that minimizes lasing threshold. These nanoplatelets possess very large gain cross-sections of 7.3 × 10−14 cm2 and ultralow lasing thresholds of 1.2 and 4.3 mJ cm−2 under two-photon (λexc=800 nm) and three-photon (λexc=1.3 μm) excitation, respectively. The highly polarized emission from the nanoplatelet laser shows no significant photodegradation over 107 laser shots. These findings constitute a more comprehensive understanding of the utility of colloidal semiconductor nanoparticles as the gain medium in high-performance frequency-upconversion liquid lasers.
Highlights
Multiphoton-pumped lasing from a solution of chromophores is important in the emerging fields of nonlinear optofluidics and bio-photonics, conventionally used organic dyes are often rendered unsuitable because of relatively small multiphoton absorption crosssections and low photostability
A solution-based gain medium can be highly desirable because of its flexibility of incorporation into optical cavities of any size and shape. Such a gain medium could be incorporated into optofluidic lasers[9,10,11], which integrate microfluidics, a liquid gain medium and optical resonators within microchannels and which have already been utilized for sensitive bio/chemical intracavity detection[12,13] and on-chip imaging[14]
The laser emission was found to be extremely photostable, enduring 4107 laser shots without photodegradation or solvent evaporation. This is advantageous to colloidal semiconductor NC-based solid state lasers where a fixed subpopulation of particles are constantly excited
Summary
Multiphoton-pumped lasing from a solution of chromophores is important in the emerging fields of nonlinear optofluidics and bio-photonics, conventionally used organic dyes are often rendered unsuitable because of relatively small multiphoton absorption crosssections and low photostability. The threshold pump intensity for MPP SE is typically much higher than that for one-photon excitation[17], making it challenging to prevent artifacts such as solvent boiling or evaporation within a practical device Overcoming these obstacles requires semiconductor nanostructures with large multiphoton absorption cross-section and reduced multiexcitonic Auger recombination rates. Colloidal quasi-two-dimensional (2D) quantum wells, known as semiconductor nanoplatelets (NPLs) have attracted much attention as a new class of solution-processable optical gain media since they retain many of the salient features of semiconductor NCs while possessing high oscillator strengths, large absorption cross-sections and strongly suppressed Auger recombination rates[29,30]
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