Edge-Emitting Silicon Nanocrystal Distributed Feedback Laser with Extremely Low Exciton Threshold

Abstract

The successful integration of a laser into the silicon photonic chip has long been the holy grail of silicon photonics. Among the various methods addressing this challenge, silicon nanocrystal (Si NC) lasers remain a tempting but debated topic due to their complex carrier recombination process. Here we demonstrate an optically pumped edge-emitting first-order distributed feedback Si NC laser by utilizing a versatile nanoimprint lithography method incorporating a composite working stamp. Upon femtosecond pulsed laser pumping, we find that the lasing threshold in exciton number per NC down to 0.021 is unusually low compared with other quantum dot gain materials. To understand this interesting behavior, we have performed systematic transient spectrum experiments on its photoluminescence and transient absorption aimed at revealing the role of selftrapping states in the carrier recombination process. Our results suggest that such states in well passivated Si NCs can be regarded as metastable states that intercept hot electrons and with a time delay, release them back to the conduction band, acting like electron reservoirs that continuously feed the active lasing state as its upper levels. In this perspective, we conclude that the surface states can benefit the buildup of population inversion and lead to inhibition of the Auger process as they temporarily localize the hot electrons outside the NC core and have verified our conclusion by numerical and experimental results, respectively. Our results provide critical information on processes related to Si NC lasing and will aid attempts at Si lasers on-chip.

Self-trapped excitons in soft semiconductors

“…STE-related materials have a wide range of potential applications, such as in solar cells, 213,214 luminescent solar concentrators, 215,216 lasing, 217,218 photocatalysts, 219 sensors 220 and scintillators. 221 Scintillators based on STE-related nanostructures were reported and self-absorption characteristics from STE emission were attributed to the high light yield.…”

Thirty Years in Silicon Photonics: A Personal View

“…This could explain the few late observations of gain [66][67][68]. Eventhough, claims for lasing in distributed feedback structures appeared [69], the use of Si-NC as an active laser medium seems improbable. Therefore, alternative approaches are now dominating the research and development of a silicon photonic laser, where either quantum dots and other materials are cointegrated in the silicon chip [70][71][72][73], or hereogeneous integration and chip bonding of III-V semiconductors are used to make a hybrid III-V laser on silicon [74,75,75,76], or, finally, nonlinear effects are exploited [77].…”

Highly efficient nonlinear optical emission from a subwavelength crystalline silicon cuboid mediated by supercavity mode

“…So far, a variety of strategys have been suggested to enhance the quantum efficiency of Si and most of them rely on band diagram engineering 7 . Quantum size effect and defect states are utilized to enhance the quantum efficiencies of Si quantum dots 8 – 12 and porous Si 13 , respectively. In addition, efficient white light emission was also observed in Au/Si alloy nanoparticles fabricated by using laser ablation 14 .…”