Photonic wire bonds have been developed as an interface for the collection of single photon emission from quantum dots within a Bragg waveguide. When resonantly excited from the top of the waveguide via free space excitation a low multiphoton contribution in the quantum dot emission with g(2)(0) = (9.5 ± 1.4) × 10−2 is shown. Our measurements demonstrate the ability to collect single-photon emission from a ridge waveguide into an optical fiber via photonic wire bonds at cryogenic temperatures. This allows for a seamless plug-and-play operation of the fiber-coupled single-photon source. Furthermore, the demonstrated approach allows for resonance fluorescence excitation without the need for any additional cross-polarization filtering.
The development of quantum photonic technologies will fuel a paradigm shift in data processing and communication protocols. A controlled generation of non-classical states of light is a challenging task at the heart of such technologies. Epitaxially grown self- assembled semiconductor quantum dots (QDs) offer the advantages of deterministic generation of single photons and prospects of device integration. By growing such QD structures only in designated locations on (001) Si substrate, the quantum properties of the emitted photons could be tuned with the built-in thermal stress for generating highly entangled photon pairs.
We discuss state-of-the-art mid-infrared light emitters and detectors based on the so-called 6.1 Å family of semiconductors, i.e. InAs, GaSb, and AlSb. Via epitaxial design routines, heterostructures composed of their binary, ternary or quaternary alloys allow unique features such as optically active type-II superlattices enabling light emitters and detectors suitable for the mid-infrared wavelength region. Here we compare and discuss the design differences between interband cascade infrared detectors employing Ga free Type II superlattices and resonant tunneling diodes (RTD) employing the quaternary alloy GaInAsSb. We show that by substituting the standard InAs/GaSb superlattice for a Ga-free superlattice, i.e. InAs/InAsSb, one requires an inverted carrier extraction path. Here it is needed to form a hole-ladder in the electron-barrier, instead of an electron-ladder in the hole-barrier. At elevated temperatures, we observe seven negative-differential-conductance (NDC) regions due to electrons tunnelling through the electron barriers of the seven cascade stages. The detector operates in photovoltaic mode with a cut-off wavelength of 8.5 μm. The RTD photodetector on the other hand utilizes GaInAsSb absorbers that allow efficient operation in the 2-4 μm range with significant electrical responsivity of 0.97 A/W at 2 μm. Contrary to interband cascade infrared detectors, RTD PD operate only at finite voltages and hence these devices are Shot noise limited.
We recently proposed a quantum computing platform that exploits circuit-bound photons to create cluster states and achieve one-way measurement-based quantum computations on arrays of photonically interfaced solid-state spin qubits with long coherence-times. Single photons are used for spin initialization, readout and for photon-mediated long-range entanglement creation. In this conference talk, we elaborate on the challenges that are faced during any practical implementation of this architecture by breaking it down into the key physical building blocks. We further discuss the constraints imposed on the spin qubits and the photonic circuit components that are set by the requirements of achieving fault-tolerant performance.
We present recent work on III-V semiconductor mid-infrared light emitters and detectors. The employed type-II broken bandgap alignment between InAs and GaxIn1-xSb allows for widely tunable emission and absorption wavelengths with energies below the individual material bandgaps. We demonstrate room temperature operation of GaSb-based interband cascade lasers (ICLs) emitting between 6.1 and 6.9 μm. Furthermore, we investigate ideal growth conditions for InAs/GaSb type-II superlattices (T2SL) for the implementation in interband cascade detectors (ICDs) with cut-off wavelengths up to 7.5 μm at room temperature. We focus on strain balancing different SL compositions for different cutoff wavelengths via Sb-soak and sub-monolayer (SML) growth of InSb. An ideal growth temperature of TSub=430 °C is found by comparing the quality of different sets of samples by means of high-resolution X-ray diffractometry (HRXRD) and room temperature photoluminescence (PL) measurements.
The goal of SiEPICfab is to conduct research in the fabrication of silicon photonic devices and photonic integrated circuits, and to make leading-edge silicon photonic manufacturing accessible to Canadian and international academics and industry. SiEPICfab builds on the success of the Silicon Electronic Photonic Integrated Circuits (SiEPIC) program, which has been offering research training workshops since 2008, by adding a fabrication facility “fab”. We have developed a rapid prototyping facility to support a complete ecosystem of companies involved in silicon photonics product development, including modelling, design, library development, fabrication, test, and packaging of silicon photonics. SiEPICfab allows designers to rapidly complete design-fabricate-test cycles, with technologies such as sub-wavelength sensors, PN junction ring modulators, silicon defect-based detectors, single photon detectors, single photon sources, and photonic wire bond integration of lasers and optical fibres.
We present recent progress on novel mid-infrared (MIR) light emitters and detectors. Optimized heterostructure and high-quality crystal growth allow for room temperature operation of interband cascade lasers (ICLs) with lasing wavelengths 𝜆 ≥ 6 μm. They employ asymmetric W-shaped optical quantum wells comprising highly strained layers of InAs/GaInSb/InAs with broken bandgap alignment. Furthermore, we discuss novel interband cascade detectors (ICDs) and resonant tunneling diode photodetectors (RTD-PDs) for MIR light detection. Different superlattice (SL) absorber design strategies for ICD cut-off wavelengths exceeding 𝜆 ≥ 7.0 μm are presented. SL absorbers ranging from standard InAs/GaSb SL to M-/W-shaped SL absorbers employing ternary barriers are compared.
Fast and efficient single-photon detectors are of paramount importance for a broad range of applications, e.g. in optical quantum information technologies. A variety of novel and refined photon counting devices has resulted from the need of ever better performance. One such device is the resonant tunneling diode (RTD) single-photon detector. Compared to conventional single-photon detectors, RTDs provide several advantageous characteristics. Since in RTDs a tunneling current is gated by photogenerated charge carriers, they are inherently photon-number resolving, and the RTD currentvoltage characteristic’s negative differential conductance region allows for higher functionality, e.g. the operation as an optically triggered bistable switch. Here, we present an overview on RTD single-photon detectors with a focus on the stateof- the-art, its underlying physical mechanisms as well the device limitations, and recent developments. We compare different RTD device geometries and operation schemes for enhanced detection efficiencies and operation frequencies.
For many quantum-photonic applications highly efficient and fast single-photon detectors are of utmost importance. Resonant tunneling diode (RTD) photodetectors can be operated as low-noise and high-speed amplifiers of small optically generated electrical signals. For this purpose, RTD photodetectors exploit that the tunneling current is extremely sensitive to changes in the local electrostatic potential, which enables the detection of single photogenerated minority charge carriers, and hence the detection of single photons with the capability of photon-number resolution. Here, we present different RTD device geometries and operation schemes for enhanced quantum-efficiency and operation frequencies.
Molecule and gas sensing is a key technology that is applied in multiple environmental, industrial and medical fields. In particular optical detection technologies enable contactless, nondestructive, highly sensitive and fast detection of even smallest concentrations of trace gases and molecules. During the past years, an increasing demand for mid-infrared (MIR) light sources suitable for, e.g. molecule or gas sensing applications, has driven the development and optimization of novel MIR lasers and light sources, such as quantum cascade lasers (QCL) or interband cascade lasers (ICL). Despite the progress on MIR light sources, there is still a lack in appropriate MIR detectors. Here, we present and discuss two promising and novel GaSb/InAs-based detector concepts. First, resonant tunneling diode (RTD) photodetectors as an alternative to avalanche photodetectors. In RTDs, amplification of photogenerated minority charge carriers is based on modulation of a majority charge carrier resonant tunneling current. Second, interband cascade photodetectors (ICD), in which a cascading scheme allows for fast carrier extraction and a compensation of the diffusion length limitation.
We present antimonide-based resonant tunneling photodetectors with GaSb/AlAsSb double barrier structures and pseudomorphically grown prewell emitter structures comprising the ternary compound semiconductors GaInSb and GaAsSb. Due to the incorporation of GaInSb and GaAsSb prewell emitters, room temperature resonant tunneling with peak-to-valley current ratios of up to 2.4 are shown. The room temperature operation is attributed to the enhanced Γ-Lvalley energy separation and consequently a re-population of the Γ-conduction band of the ternary compound emitter prewell with respect to bulk GaSb. By integration of a quaternary absorption layer, RTDs photodetectors with cut-off wavelengths up to 3 μm have been realized.
Gas sensing is a key technology with applications in various industrial, medical and environmental areas. Optical detection mechanisms allow for a highly selective, contactless and fast detection. For this purpose, rotational-vibrational absorption bands within the mid infrared (MIR) spectral region are exploited and probed with appropriate light sources. During the past years, the development of novel laser concepts such as interband cascade lasers (ICLs) and quantum cascade lasers (QCLs) has driven a continuous optimization of MIR laser sources. On the other hand side, there has been relatively little progress on detectors in this wavelength range. Here, we study two novel and promising GaSb-based detector concepts: Interband cascade detectors (ICD) and resonant tunneling diode (RTD) photodetectors. ICDs are a promising approach towards highly sensitive room temperature detection of MIR radiation. They make use of the cascading scheme that is enabled by the broken gap alignment of the two binaries GaSb and InAs. The interband transition in GaSb/InAs-superlattices (SL) allows for normal incidence detection. The cut-off wavelength, which determines the low energy detection limit, can be engineered via the SL period. RTD photodetectors act as low noise and high speed amplifiers of small optically generated electrical signals. In contrast to avalanche photodiodes, where the gain originates from multiplication due to impact ionization, in RTD photodetectors a large tunneling current is modulated via Coulomb interaction by the presence of photogenerated minority charge carriers. For both detector concepts, first devices operational at room temperature have been realized.
We have studied the photocurrent-voltage relation of resonant tunneling diode (RTD) photodetectors by means of electrooptical transport measurements. The investigated RTDs are based on an Al0.6Ga0.4As/GaAs double barrier resonant tunneling structure (RTS) with an integrated GaInNAs absorption layer for light sensing at the telecommunication wavelength of λ= 1.3 μm. Under illumination, photogenerated holes can be captured for accumulation in vicinity to the RTS and modulate the resonant tunneling current that is highly sensitive to changes in the local electrostatic potential. The resulting photocurrent-voltage relation is found to be a nonlinear function of the applied bias voltage, and governed by the interplay of the electronic transport properties of the RTS and the dynamics of photogenerated holes. Time-resolved photocurrent measurements were employed to analyze the dynamics of photogenerated holes. From the photocurrent-time traces the quantum-efficiency and mean lifetime of photogenerated holes can be separately determined. We found that the photoresponse is suppressed by a low quantum efficiency for bias voltages below V ≤ 1 V. In this regime, the built-in electric field prevents photogenerated holes from accumulation at the RTS. For voltages above V >1 V, the built-in field is compensated by the external bias, and η(V) takes on a constant value. In this regime, the RTD photoresponse is mainly determined by the lifetime of holes accumulated at the RTS. The lifetime is limited by thermionic carrier escape and was found to decrease exponentially with the applied bias voltage.
We demonstrate a cavity-enhanced photodetector at the telecommunication wavelength of λ = 1.3 μm based on a resonant tunneling diode (RTD). The cavity-enhanced RTD photodetector consists of three integral parts: First, a Ga0.89In0.11N0.04As0.96 absorption layer that can be grown lattice-matched on GaAs and which is light-active in the near infrared spectral region due to its reduced bandgap energy. Second, an Al0.6Ga0.4As/GaAs double barrier resonant tunneling structure (RTS) that serves as high gain internal amplifier of weak electric signals caused by photogenerated electron-hole pairs within the GaInNAs absorption layer. Third, an optical distributed Bragg reflector (DBR) cavity consisting of five top and seven bottom alternating GaAs/AlAs mirror pairs, which provides an enhanced quantum efficiency at the resonance wavelength. The samples were grown by molecular beam epitaxy. Electro-optical properties of the RTDs were studied at room temperature. From the reflection-spectrum the optical resonance at λ = 1.29 μm was extracted. The current-voltage characteristics were studied in the dark and under illumination and a wellpronounced photo-response was found and is attributed to accumulation of photogenerated holes in the vicinity of the RTS. The maximum photocurrent was found at the optical resonance of 1.29 μm. At resonance, a sensitivity of S = 3.97 × 104 A/W was observed. From the sensitivity, a noise equivalent power of NEP = 1.18 × 10-16 W/Hz1/2, and a specific detectivity of D∗ ≅ 6.74 × 1012 cm Hz1/2/W were calculated. For a single absorbed photon a photocurrent of ISP = 50 pA was determined.
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