Colloidal quantum dots (QDs), as a low-cost, flexibly tunable and fabrication scalable semiconductor material, have demonstrated exceptional capabilities in many complex applications including high-quality displays, high-resolution infrared imaging, advanced spectrometry and integration into photonic circuits. This study explores combining the tunable spectral response features of QD-based photodiodes (QDPDs) with dispersive photonic integrated circuits (PICs), demonstrating a spectrometer with operational spectral range extended beyond its original free spectral range (FSR). Experimentally, two types of PbS QDPDs, with different absorption features, were integrated in cascade on the output channels of a planar concave grating (PCG) with a 90 nm FSR. The differential responses of these QDPDs to two adjacent diffraction orders of the PCG enabled the creation of a spectrometer with a spectral range of approximately 180 nm, effectively decoupling two FSRs of the PCG. The proposed cascaded QDPDs, with diverse spectral photodetection capabilities, present great potential when integrated into complex optical systems.

Colloidal quantum dots (QDs) have become a versatile optoelectronic material for emitting and detecting light that can overcome the limitations of a range of electronic and photonic technology platforms. Photonic integrated circuits (PICs), for example, face the persistent challenge of combining active materials with passive circuitry ideally suited for guiding light. Here, we demonstrate the integration of photodiodes (PDs) based on PbS QDs on silicon nitride waveguides (WG). Analyzing planar QDPDs first, we argue that the main limitation WG-coupled QDPDs face is detector saturation induced by the high optical power density of the guided light. Using the cladding thickness and waveguide width as design parameters, we mitigate this issue, and we demonstrate WG-QDPDs with an external quantum efficiency of 67.5% at 1275 nm that exhibit a linear photoresponse for input powers up to 400 nW. In the next step, we demonstrate a compact infrared spectrometer by integrating these WG-QDPDs on the output channels of an arrayed waveguide grating demultiplexer. This work provides a path toward a low-cost PD solution for PICs, which are attractive for large-scale production.

An integrated spectrometer based on arrayed waveguide grating and PbS colloidal quantum dot photodiode array was demonstrated on the silicon nitride photonic platform, operating around 1300 nm, which might be an attractive low-cost integration routine.

Monolithic integration of PbS colloidal quantum dot photodiodes on silicon nitride waveguides is demonstrated for the first time. Waveguide width and top cladding thickness are designed to meet the low saturation threshold of optical power.

Colloidal quantum dots (QDs) are an attractive light source for visible photonics, in particular their widely tunable emission wavelength, inexpensive wet-chemical synthesis and straight-forward hybrid integration can make the difference. In this work, integrated light-emitting diodes are demonstrated based on CdSe/CdS QDs, with the emission directly coupled to a silicon nitride waveguide. The devices feature a record current density of up to 100 A cm −2 and a maximum on-chip power density of almost 1.5 W cm −2 in a single-mode waveguide. Operated as detectors, the photodiodes have a low dark current of 1.5 µA cm −2 . It is anticipated, that the devices will find an application in chip-based absorption spectroscopy and bio-sensing, as they can be post-processed on foundry-fabricated waveguide platforms, at a low cost. In addition, this approach provides the missing low-loss waveguide layer, necessary for building an electrically pumped laser using colloidal QDs.

Colloidal quantum dots (QDs) have become an attractive light source for visible photonics. Here, we demonstrate the first integrated LED based on CdSe/CdS QDs, with the emission directly coupled to a silicon nitride waveguide.

Future quantum optical networks will require an integrated solution to multiplex suitable sources and detectors on a low-loss platform. Here we combined superconducting single-photon detectors with colloidal PbS/CdS quantum dots (QDs) and low-loss silicon nitride passive photonic components to show their combined operation at cryogenic temperatures. Using a planar concave grating spectrometer, we performed wavelength-resolved measurements of the photoluminescence decay of QDs, which were deterministically placed in the gap of plasmonic antennas, in order to improve their emission rate. We observed a Purcell enhancement matching the antenna simulations, with a concurrent increase of the count rate on the superconducting detectors.

The development of ultralow-loss silicon-nitride-based waveguide platforms has enabled the realization of integrated optical filters with unprecedented performance. Such passive circuits, when combined with phase modulators and low-noise lasers, have the potential to improve the current state of the art of the most critical components in coherent communications, beam steering, and microwave photonics applications. However, the large refractive index difference between silicon nitride and common III-V gain materials in the telecom wavelength range hampers the integration of electrically pumped III-V semiconductor lasers on a silicon nitride waveguide chip. Here, we present an approach to overcome this refractive index mismatch by using an intermediate layer of hydrogenated amorphous silicon, followed by the microtransfer printing of a prefabricated III-V semiconductor optical amplifier. Following this approach, we demonstrate a heterogeneously integrated semiconductor optical amplifier on a silicon nitride waveguide circuit with up to 14 dB gain and a saturation power of 8 mW. We further demonstrate a heterogeneously integrated ring laser on a silicon nitride circuit operating around 1550 nm. This heterogeneous integration approach would not be limited to silicon-nitride-based platforms: it can be used advantageously for any waveguide platform with low-refractive-index waveguide materials such as lithium niobate.

Single-photon sources and detectors are indispensable building blocks for integrated quantum photonics, a research field that is seeing ever increasing interest for numerous applications. In this work, we implemented essential components for a quantum key distribution transceiver on a single photonic chip. Plasmonic antennas on top of silicon nitride waveguides provide Purcell enhancement with a concurrent increase of the count rate, speeding up the microsecond radiative lifetime of IR-emitting colloidal PbS/CdS quantum dots (QDs). The use of low-fluorescence silicon nitride, with a waveguide loss smaller than 1 dB/cm, made it possible to implement high extinction ratio optical filters and low insertion loss spectrometers. Waveguide-coupled superconducting nanowire single-photon detectors allow for low time-jitter single-photon detection. To showcase the performance of the components, we demonstrate on-chip lifetime spectroscopy of PbS/CdS QDs. The method developed in this paper is predicted to scale down to single QDs, and newly developed emitters can be readily integrated on the chip-based platform.

We demonstrate the first heterogeneously integrated laser around 1550 nm on a silicon-nitride-on-insulator chip. Single-mode lasing at room temperature is achieved in a silicon nitride cavity comprising an adiabatically tapered III-V amplifier.

We demonstrate a strategy for the integration of C-band operating amplifiers on a silicon-nitride-on-insulator platform. A layer of hydrogenated amorphous silicon is used to bridge the index contrast between the nitride and the active device.

We developed a hybrid SiN-QDOT platform by embedding quantum dots in a SiN waveguide. Low loss waveguiding, high modal gain and lasing from mikrodisk and DFB-type devices was demonstrated.

We demonstrate the fabrication and characterization of on-chip vertically-emitting SiNx/Au nanopatch cavities containing a monolayer of colloidal quantum dots. The fabrication process is based on electron-beam lithography and deterministically positions both the cavity and the emitters within the cavity with an accuracy of 10 nm. The Purcell enhancement of the spontaneous emission of the quantum dots is studied theoretically and experimentally. The fabrication technique makes it possible to pattern the quantum dot monolayer such that the quantum dots only occupy the center of the nanopatch cavity where a Purcell factor up to 7 can be reached. The work paves the way towards scalable fabrication of bright and directive single-photon sources.

We demonstrate the deterministic incorporation of colloidal CdSe/CdS core-shell quantum dots emitting at λ = 620 nm into the gap of plasmonic Ag bowtie antennas. The antennas were fabricated using a lift-off process employing electron beam lithography and electron gun evaporation of silver on a copper seed layer. Nano-patterning of the wet-chemically synthesized quantum dots was done using a previously devised lift-off process and a state-of-the-art electron beam lithography system for the alignment. Placing colloidal quantum dots in the gap of plasmonic antennas can significantly reduce their intrinsic radiative lifetime and hence increase the emission rate for the application as a room-temperature single-photon source.

Flat transmissive lens designs for infrared sensor applications based on sub-wavelength gratings were analyzed using a finite difference time domain program (Lumerical). An initial design for broadband transmission with a design wavelength of 4 pm exhibited a drop in the transmittance for large incidence angles that caused defocusing. This was investigated numerically and a phenomenological explanation is presented. The subwavelength structure was then optimized to work also for large incidence angles. The focal spot of the proposed lens was characterized using a finite element method package (Comsol).