We report on the "flash" synthesis of CdSe/ CdS core−shell quantum dots (QDs). This new method, based on a seeded growth approach and using an excess of a carboxylic acid, leads to an isotropic and epitaxial growth of a CdS shell on a wurtzite CdSe core. The method is particularly fast and efficient, allowing the controllable growth of very thick CdS shells (up to 6.7 nm in the present study) in no more than 3 min, which is considerably shorter than in previously reported methods. The prepared materials present state-of-the-art properties with narrow emission and high photoluminescence quantum yields, even for thick CdS shells. Additionally, Raman analyses point to an alloyed interface between the core and the shell, which, in conjunction with the thickness of the CdS shell, results in the observed considerable reduction of the blinking rate.

Colloidal core/shell InP/ZnSe quantum dots (QDs), recently produced using an improved synthesis method, have a great potential in life-science applications as well as in integrated quantum photonics and quantum information processing as single-photon emitters. Single-particle spectroscopy of 10 nm QDs with 3.2 nm cores reveals strong photon antibunching attributed to fast (70 ps) Auger recombination of multiple excitons. The QDs exhibit very good photostability under strong optical excitation. We demonstrate that the antibunching is preserved when the QDs are excited above the saturation intensity of the fundamental-exciton transition. This result paves the way toward their usage as high-purity on-demand single-photon emitters at room temperature. Unconventionally, despite the strong Auger blockade mechanism, InP/ZnSe QDs also display very little luminescence intermittency ("blinking"), with a simple on/off blinking pattern. The analysis of single-particle luminescence statistics places these InP/ZnSe QDs in the class of nearly blinking-free QDs, with emission stability comparable to state-of-the-art thick-shell and alloyed-interface CdSe/CdS, but with improved single-photon purity.

Hybrid silicon nitride (SiN)-quantum-dot (QD) microlasers coupled to a passive SiN output waveguide with a 7 µm diameter and a record-low threshold density of 27 µJ cm are demonstrated. A new design and processing scheme offers long-term stability and facilitates in-depth QD material and device characterization, thereby opening new paths for optical communication, sensing, and on-chip cavity quantum optics based on colloidal QDs.

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The generation of an octave spanning supercontinuum covering 488 nm to 978 nm (at -30 dB) is demonstrated for the first time on-chip. This result is achieved by dispersion engineering a 1 cm long Si 3 N 4 waveguide and pumping it with an 100 fs Ti:Sapphire laser emitting at 795 nm. This work offers a bright broadband source for biophotonic applications and frequency metrology. OCIS codes:(320.6629) Supercontinuum Generation; (190.4390) Nonlinear optics, integrated optics. http://dx.doi.org/10.1364/XX.99.099999Over the last decade, the progress of supercontinuum (SC) generation in photonic crystal fibers [1][2][3] has led to a series of advancements in spectroscopy [4], optical coherence tomography [5] and precise frequency metrology [6]. Recently SC generation on integrated CMOS compatible waveguide platforms has been attracting significant attention. Previous efforts mostly aimed at the telecom wavelength window [7] for WDM communication and at the mid-infrared range [8] for spectroscopic sensing. However, a SC covering the red to near-infrared spectral window where tissue and cells possess low absorption and scattering coefficients could offer particular advantages for biological applications such as bioimaging [9] and Raman spectroscopy [10,11].To produce a SC below 1 μm on a CMOS-compatible integrated platform, there are two main hurdles to overcome: transparency of the waveguide and phase matching. The first one can be addressed by using silicon nitride as the waveguide material rather than silicon [12]. Recently a SC down to 665 nm has been obtained using a silicon nitride waveguide pumped at 1335 nm [13]. The second hurdle is to obtain anomalous dispersion required for efficient SC generation in Si 3 N 4 waveguides. * Corresponding author: haolan.zhao@ugent.be At visible wavelengths, this is not trivial because Si 3 N 4 possesses a strong normal material dispersion due the proximity to the material bandgap. The strong normal material dispersion thus needs to be compensated by the waveguide dispersion. A frequency comb using a silicon nitride microcavity has been demonstrated with comb lines down to 765 nm circumventing this requirement by using a combination of χ(2) and χ(3) nonlinear processes [14] yet it requires careful dispersion management. In this letter, inspired by the work on silicon platform [15,16], we implement a similar method to achieve anomalous dispersion in a silicon nitride waveguide by partially underetching the silicon oxide underneath the Si 3 N 4 waveguide core. We demonstrate an SC ranging from 488 nm to 978 nm when pumping the waveguide at 795 nm. To the best of our knowledge, this is the first demonstration of an octave spanning supercontinuum extending in the sub-500 nm wavelength range on an integrated platform. It constitutes a first step to a fully integrated broadband source for e.g. biophotonic applications.The waveguide used in the experiment is fabricated in a CMOS pilot line at imec [17]. A 300 nm-thick silicon nitride film is grown via low-pressure chemical vapor deposit...