Surface-emitting red, green, and blue colloidal quantum dot distributed feedback lasers (original) (raw)
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Multi-wavelength colloidal quantum dot lasers in distributed feedback cavities
Science China Information Sciences, 2020
Lasers with multi-wavelength colloidal quantum dots (CQDs) can be achieved using complex grating structures and flexible substrate. The structure contains graduated periods and rectangular cavity fabricated through interference lithography, which acts as the distributed feedback cavity. A layer of densely packed CQD film is deposited on the cavity via spin coating technique. The performance of CQD lasers based on different distributed feedback cavities is investigated. Multi-wavelength lasing is achieved based on a flexible rectangular cavity.
On-Chip Single-Mode Distributed Feedback Colloidal Quantum Dot Laser under Nanosecond Pumping
ACS Photonics, 2017
We report on a hybrid integrated distributed feedback (DFB) laser fabricated using the colloidal quantum dots (QDs)/silicon nitride (SiN) integration platform. The DFB laser is fabricated with a CMOS-compatible process and consists of a waveguide stack in which a QD layer is embedded between two SiN layers to enhance the coupling of the QD to the optical waveguide mode. Following characterization of the intrinsic properties of the CdSe/CdS core/shell QDs using transient absorption spectroscopy, we demonstrate singlemode lasing upon nanosecond optical pumping. With a 7 ns pump pulse, the lasing threshold is 270 μJ/cm 2. This result attests to the potential of colloidal QDs as an enabling gain material for integrated SiN photonics, and it showcases the design versatility of hybrid integrated photonics platforms based on colloidal QDs.
Azimuthally Polarized, Circular Colloidal Quantum Dot Laser Beam Enabled by a Concentric Grating
ACS Photonics
Since optical gain was observed from colloidal quantum dots (CQDs), research on CQD lasing has been focused on the CQDs themselves as gain materials and their coupling with optical resonators. Combining the advantages of a CQD gain medium and optical microcavity in a laser device is desirable. Here, we show concentric circular Bragg gratings intimately incorporating CdSe/CdZnS/ZnS gradient shell CQDs. Because of the strong circularly symmetric optical confinement in two dimensions, the output beam CQD-based circular grating distributed feedback laser is found to be highly spatially coherent and azimuthally polarized with a donut-like cross section. We also observe the strong modification of the photoluminescence spectrum by the grating structures, which is associated with modification of optical density of states. This effect confirmed the high quality of the resonator that we fabricated and the spectral overlap between the optical transitions of the emitter and resonance of the cavity. Single mode lasing has been achieved under a quasi-continuous pumping regime, while the position of the lasing mode can be conveniently tuned via adjusting the thickness of the CQD layer. Moreover, a unidirectional output beam can be observed as a bright circular spot on a screen without any collimation optics, presenting a direct proof of its high spatial coherence.
Advanced Materials, 2021
Pb‐chalcogenide colloidal quantum dots (CQDs) are attractive materials to be used as tuneable laser media across the infrared spectrum. However, excessive nonradiative Auger recombination due to the presence of trap states outcompetes light amplification by rapidly annihilating the exciton population, leading to high gain thresholds. Here, a binary blend is employed of CQDs and ZnO nanocrystals in order to passivate the in‐gap trap states of PbS‐CQD gain medium. Using transient absorption, a fivefold increase is measured in Auger lifetime demonstrating the suppression of trap‐assisted Auger recombination. By doing so, a twofold reduction is achieved in amplified spontaneous emission (ASE) threshold. Finally, by integrating the proposed binary blend to a distributed feedback (DFB) resonator, single‐mode lasing emission is demonstrated at 1650 nm with a linewidth of 1.23 nm (0.62 meV), operating at a low lasing threshold of ≈385 μJ cm–2. The Auger suppression in this system has allowe...
Microsecond-sustained lasing from colloidal quantum dot solids
Nature communications, 2015
Colloidal quantum dots have grown in interest as materials for light amplification and lasing in view of their bright photoluminescence, convenient solution processing and size-controlled spectral tunability. To date, lasing in colloidal quantum dot solids has been limited to the nanosecond temporal regime, curtailing their application in systems that require more sustained emission. Here we find that the chief cause of nanosecond-only operation has been thermal runaway: the combination of rapid heat injection from the pump source, poor heat removal and a highly temperature-dependent threshold. We show microsecond-sustained lasing, achieved by placing ultra-compact colloidal quantum dot films on a thermally conductive substrate, the combination of which minimizes heat accumulation. Specifically, we employ inorganic-halide-capped quantum dots that exhibit high modal gain (1,200 cm(-1)) and an ultralow amplified spontaneous emission threshold (average peak power of ∼50 kW cm(-2)) and ...
A solution-processed 1.53 μm quantum dot laser with temperature-invariant emission wavelength
Optics Express, 2006
Sources of coherent, monochromatic short-wavelength infrared (1-2 mum) light are essential in telecommunications, biomedical diagnosis, and optical sensing. Today's semiconductor lasers are made by epitaxial growth on a lattice-matched single-crystal substrate. This strategy is incompatible with integration on silicon. Colloidal quantum dots grown in solution can, in contrast, be coated onto any surface. Here we show a 1.53 mum laser
Quantum dot lasers: breakthrough in optoelectronics
Thin Solid Films, 2000
Semiconductor heterostructures with self-organized quantum dots (QDs) have experimentally exhibited properties expected for zerodimensional systems. When used as active layer in the injection lasers, these advantages help to strongly increase material gain and differential gain, to improve temperature stability of the threshold current, and to provide improved dynamic properties. Molecular beam epitaxy (MBE) represents a developed technology well suited for fabrication of self-organized QDs. Optimization of deposition parameters can ensure that the self-organized islands are small (,10 nm), have a similar size and shape and form dense arrays. Saturation material gain is as high as 150000 cm 21 compared with QW values of about 3000 cm 21. Maximum differential gain reported for QD lasers approaches 10 212 cm 2 and exceeds the QW laser values by about three orders of magnitude. Direct observation of relaxation oscillations reveals present cutoff frequencies close to 10 GHz. High internal (.96%) and differential (70%) ef®ciencies at 300 K are realized. Using the novel concept of electronically-coupled QDs and oxide-de®ned 10 mm apertures, CW lasing with J th 180 A/cm 2 , is realized in surface-emitting QD lasers (300 K). Wall-plug ef®ciencies are up to 16%. Total currents as low as 68 mA are measured for 1mm apertures. GaAs-based lasers for the 1.3 mm range with low J th (65 A/cm 2) at room temperature (RT) are realized using InAs/InGaAs/GaAs QDs obtained by activated spinodal decomposition. In stripes the lasing occurs via the QD ground state (J th 90 A/cm 2) for cavity lengths L. 1 mm (uncoated). Differential ef®ciency is 55% and internal losses are 1.5 cm 21. A characteristic temperature near RT is 160 K. 3W CW operation at RT is achieved. The recent progress in lasers based on self-organized MBE QDs already made it possible to fabricate devices with dramatically improved characteristics as compared to recent QW devices for the most important commercial applications.
Single-mode light source fabrication based on colloidal quantum dots
2009
There are huge market demands for innovative, cheap and efficient light sources, including light emitting devices, such as LEDs and lasers. However, the light source development in the visible spectral range encounters significant difficulties these years. The available visible wavelength LEDs or lasers are few, large and expensive. The main challenge lies at the lack of efficient light media. Semiconductor nanocrystal quantum dots (QDs) have recently commanded considerable attention. As a result of quantum confinement effect, the emission color of these QDs covers the whole visible spectral range and can be modified dramatically by simply changing their size. Such spectral tunability, together with large photoluminescence quantum yield and photostability, make QDs attractive for potential applications in a variety of light emitting technologies. However, there are still several technical problems that hinder their application as light sources. One main issue is how to fabricate these QDs into a solid state device while still retaining their original optical emission properties. A vacuum assisted micro-fluidic fabrication of guided wave devices has demonstrated low waveguide propagation loss, lower crosstalk, and improved waveguide structures. We report herein the combination of the excellent emission properties of QDs and novel vacuum assisted micro-fluidic photonic structure fabrication technique to realize single-mode efficient light sources.