Single‐Mode Lasing from a Single 7 nm Thick Monolayer of Colloidal Quantum Wells in a Monolithic Microcavity

Abstract

In this work, monolithically-fabricated vertical cavity surface emitting lasers (VCSELs) of densely-packed, orientation-controlled, atomically flat colloidal quantum wells (CQWs) using a self-assembly method is reported and single-mode lasing from a record thin colloidal gain medium with a film thickness of 7 nm under femtosecond optical excitation is demonstrated. Specially engineered CQWs are used to demonstrate these hybrid CQW-VCSELs consisting of only a few layers to a single monolayer of CQWs and are achieved the lasing from these thin gain media by thoroughly modeling and implementing a vertical cavity consisting of distributed Bragg reflectors with an additional dielectric layer for mode tuning. Accurate spectral and spatial alignment of the cavity mode with the CQW films is secured with the help of full electromagnetic computations. While overcoming the long-pending problem of limited electrical conductivity in thicker colloidal films, such ultrathin colloidal gain media can be helpful to enable fully electrically-driven colloidal lasers.

Ultralow‐Threshold and High‐Quality Whispering‐Gallery‐Mode Lasing from Colloidal Core/Hybrid‐Shell Quantum Wells

“…[ 21,22 ] Driven by their remarkable gain properties, numerous works have been conducted on the demonstration of core/alloyed shell NPLs‐based lasers. [ 23–27 ]…”

“…To date, the majority of works using NPLs as a gain medium have adopted several optical feedback configurations including Fabry−Pérot cavity, [ 10,11,23,25,28–30 ] photonic‐crystal cavity, [ 26,31 ] distributed feedback cavity, [ 24 ] as well as random lasing cavity. [ 32 ] However, NPLs‐whispering gallery mode (WGM) lasers with ultrahigh quality ( Q ) factor and extremely small mode volume, [ 33,34 ] in which the closed feedback loop is formed via total internal reflection in the boundaries of high refractive index cavity, are rarely studied.…”

All-colloidal parity–time-symmetric microfiber lasers balanced between the gain of colloidal quantum wells and the loss of colloidal metal nanoparticles

“…7 Previously, various heterostructures of CQWs have been used as active media in optical gain and laser applications, integrating their closely packed solid films into various optical resonator structures. These specifically include active waveguides, 8 vertical-cavity surface-emitting lasers, 9,10 on-chip cavities, 11 and WGM resonators. 12,13…”

“…7 Previously, various heterostructures of CQWs have been used as active media in optical gain and laser applications, integrating their closely packed solid films into various optical resonator structures. These specifically include active waveguides, 8 vertical-cavity surface-emitting lasers, 9,10 on-chip cavities, 11 and WGM resonators. 12,13 One of the main challenges in the development of laser cavity configurations is to design a high quality-factor (Q-factor) and large resonant mode overlapping with the gain medium (Γ).…”

Self-Resonant Microlasers of Colloidal Quantum Wells Constructed by Direct Deep Patterning

“…The proposed structure has the potential to be coupled to a waveguide to be used in chip-scale photonic devices. Unlike exploitation of simple fabrication methods , such as “coffee-stain” cavities, − which have resulted in limited control over the cavity geometry, our proposed fabrication approach enables tight confinement of light, significantly enhances the directionality of the output beam, and assures in-plane laser emission propagation. Here, the devised fully colloidal laser architecture relies on self-resonating distributed Bragg reflector (DBR) grating waveguide as the gain section integrated in plane with a pair of reflectors, one of which is a highly reflective (100%) DBR grating, whereas the other is defined as a moderately reflective (90%) DBR outcoupler.…”