In this article, we present the investigation of bias-dependent carrier dynamics of ErAs:In(Al)GaAs superlattice (SL) photoconductors and compare the results to a theoretical model. The carrier dynamics for materials without InAlAs layer can be modeled by a monoexponential decay that features a linear decrease in the carrier lifetime with bias. For a 10 mW laser power, the bias-free lifetime for this material is 440 fs and decreases to 97 fs at 72 kV/cm. For materials consisting of an SL with an absorbing InGaAs and a high-barrier InAlAs layer, the carrier lifetime determined by differential transmission features a bias-dependent fast decay ( $\sim$ 100 fs) followed by a bias-independent slower decay ( $\sim$ 2.5 ps). The share of charges being trapped with the fast decay can go up to 83% at 80 kV/cm. Terahertz (THz) spectra for different biasing conditions were recorded in order to confirm the decrease of carrier lifetime. The reduction of the lifetime shifts the lifetime rolloff toward higher frequencies. The data show a maximum of 6 dB improvement in power for the high-frequency components, in agreement with theoretical expectations. The optimized time domain spectroscopy spectrum shows a peak dynamic range of 110 dB with more than 6 THz bandwidth. The maximum emitted THz power outcoupled through an uncoated silicon-lens with $\sim$ 30% reflection loss was 472 $\pm$ 35 $\mu$ W.

We report record-setting quantum-dot lasers integrated on Si for multifunctional integrated systems. Efficient coupling of laser output to Si waveguides was achieved with 13 GHz 3-dB bandwidth, 60 dB side-mode-suppression-ratio, and 26 kHz fundamental linewidth.

We report a novel solution to the high temperature reliability of InAs quantum dot lasers grown on (001) Si. Negligible degradation was observed after 1800 h aging, giving an extrapolated lifetime of two million hours.

Many-body localization (MBL) has attracted significant attention because of its immunity to thermalization, role in logarithmic entanglement entropy growth, and opportunities to reach exotic quantum orders. However, experimental realization of MBL in solid-state systems has remained challenging. Here, we report evidence of a possible phonon MBL phase in disordered GaAs/AlAs superlattices. Through grazing-incidence inelastic X-ray scattering, we observe a strong deviation of the phonon population from equilibrium in samples doped with ErAs nanodots at low temperature, signaling a departure from thermalization. This behavior occurs within finite phonon energy and wavevector windows, suggesting a localization-thermalization crossover. We support our observation by proposing a theoretical model for the effective phonon Hamiltonian in disordered superlattices, and showing that it can be mapped exactly to a disordered 1D Bose-Hubbard model with a known MBL phase. Our work provides momentum-resolved experimental evidence of phonon localization, extending the scope of MBL to disordered solid-state systems.

Coherent optical states consist of a quantum superposition of different photon number (Fock) states, but because they do not form an orthogonal basis, no photon number states can be obtained from it by linear optics. Here we demonstrate the reverse, by manipulating a random continuous single-photon stream using quantum interference in an optical Sagnac loop, we create engineered quantum states of light with tunable photon statistics, including approximate weak coherent states. We demonstrate this experimentally using a true single-photon stream produced by a semiconductor quantum dot in an optical microcavity, and show that we can obtain light with g^{(2)}(0)→1 in agreement with our theory, which can only be explained by quantum interference of at least 3 photons. The produced artificial light states are, however, much more complex than coherent states, containing quantum entanglement of photons, making them a resource for multiphoton entanglement.

We present a new mechanism, the moiré effect, which leads to the appearance of dislocations in interference patterns. Remote interference dislocations in condensate of indirect excitons originate from the moiré effect and evidence exciton superfluidity.

Interference patterns provide direct measurement of coherent propagation of matter waves in quantum systems. Superfluidity in Bose–Einstein condensates of excitons can enable long-range ballistic exciton propagation and can lead to emerging long-scale interference patterns. Indirect excitons (IXs) are formed by electrons and holes in separated layers. The theory predicts that the reduced IX recombination enables IX superfluid propagation over macroscopic distances. Here, we present dislocation-like phase singularities in interference patterns produced by condensate of IXs. We analyze how exciton vortices and skyrmions should appear in the interference experiments and show that the observed interference dislocations are not associated with these phase defects. We show that the observed interference dislocations originate from the moiré effect in combined interference patterns of propagating condensate matter waves. The interference dislocations are formed by the IX matter waves ballistically propagating over macroscopic distances. The long-range ballistic IX propagation is the evidence for IX condensate superfluidity.

Regrown quantum-dot distributed feedback lasers on Si demonstrate record performance, with a threshold current of 10 mA, an intrinsic linewidth of 41.2 kHz, a side-mode suppression ratio of 57.5 dB, and a maximum power of 11.7 mW.

Significant improvements in III–V/Si epitaxy have pushed quantum dots (QDs) to the forefront of Si photonics. For efficient, scalable, and multifunctional integrated systems to be developed, a commercially viable solution must be found to allow efficient coupling of the QD laser output to Si waveguides. In this work, the design, fabrication, and characterization of such a platform are detailed. Record‐setting evanescent QD distributed feedback lasers on Si with a 3 dB modulation bandwidth of 13 GHz, a threshold current of 4 mA, a side‐mode‐suppression‐ratio of 60 dB, and a fundamental linewidth of 26 kHz, are reported. The maximum temperature during the backend III/V process is only 200 °C, which is fully compatible with CMOS process thermal budgets. The whole process is substrate agnostic and hence can leverage previous development in QD lasers grown on Si and benefit from the economy of scale. The broadband and versatile nature of the QD lasers and the Si‐on‐insulator low‐loss waveguiding platform can be expanded to build fully functional photonic integrated circuits throughout the O band.

The performance of multi-electron spin qubits is examined by comparing exchange oscillations in coupled single-electron and multi-electron quantum dots in the same device. Fast (> 1 GHz) exchange oscillations with a quality factor Q > 15 are found for the multi-electron case, compared to Q 2 for the single-electron case, the latter consistent with previous experiments. A model of dephasing that includes voltage and hyperfine noise is developed that is in good agreement with both single- and multi-electron data, though in both cases additional exchange-independent dephasing is needed to obtain quantitative agreement across a broad parameter range.

In article number 2100057, John E. Bowers, Yating Wan, Chao Xiang, and co-workers report record-setting quantum dot (QD) distributed feedback lasers on Si with a 3-dB modulation bandwidth of 13 GHz, a threshold current of 4 mA, a side-mode-suppression-ratio of 60 dB, and a fundamental linewidth of 26 kHz. The broadband QD lasers and the Si-on-insulator waveguiding platform can be expanded to build fully functional photonic integrated circuits throughout the O band.

We studied both experimentally and theoretically attractive dipolar interaction in bilayers of indirect excitons (IXs) with built-in dipole moments and found monotonic IX energy reduction with density and spatial attraction between IX clouds.

ErAs:In(Al)GaAs photoconductors have proven to be outstanding devices for photonic terahertz (0.1–10 THz) generation and detection with previously reported sub-0.5 ps carrier lifetimes. We present the so far most detailed material characterization of these superlattices composed of ErAs, InGaAs, and InAlAs layers grown by molecular beam epitaxy. The variation of the material properties as a function of the ErAs concentration and the superlattice structure is discussed with focus on source materials. Infrared spectroscopy shows an absorption coefficient in the range of 4700–6600 cm−1 at 1550 nm, with shallow absorption edges toward longer wavelengths caused by absorption of ErAs precipitates. IV characterization and Hall measurements show that samples with only 0.8 monolayers of electrically compensated ErAs precipitates (p-delta-doped at 5×1013 cm−2) and aluminum-containing spacer layers enable high dark resistance (∼10–20 MΩ) and high breakdown field strengths beyond 100 kV/cm, corresponding to >500 V for a 50 μm gap. With higher ErAs concentration of 1.6 ML (2.4 ML), the resistance decreases by a factor of ∼40 (120) for an otherwise identical superlattice structure. We propose a theoretical model for calculation of the excess current generated due to heating and for the estimation of the photocurrent from the total illuminated current. The paper concludes with terahertz time-domain spectroscopy measurements demonstrating the strengths of the material system and validating the proposed model.

Regrown quantum-dot distributed feedback lasers on (001) Si demonstrated a SMSR of 50 dBm, a threshold current density of 440 A/cm 2 , a CW operation temperature of 70°C, and a path towards high-volume, low-cost transceivers.

Direct epitaxial growth of III-V light sources on Si photonic chips is promising to realize low-cost and high-functionality photonic integrated circuits. Historically, high temperature reliability of such devices has been the major roadblock due to crystalline defects from heteroepitaxy. Here, by reducing the threading dislocation densities to ∼ 1 × 1 0 6 c m − 2 and efficiently removing misfit dislocations above and below the active region, 1.3 µm InAs quantum-dot lasers directly grown on industry standard on-axis Si (001) show record-breaking reliability at 80°C. The hero device shows minimum degradation after more than 1200 h of constant current stress. Statistical analysis shows an extrapolated lifetime of over 22 years for the median devices, bringing these devices one big step closer to real world applications.

We report on the repulsive and attractive interactions between indirect excitons in a system of separated coupled quantum wells.

We demonstrate UV contact-lithographically fabricated III-V field effect transistors examined over a bandwidth of 100 GHz to 11.8 THz. The zero-bias device reaches a noise equivalent power as low as 250 pW/ √ Hz at 0.6 THz which then increases as f at higher frequencies. The responsivity is modeled by a simple equivalent circuit, showing good agreement over the frequency range of 2 decades. The FETs have been characterized using a photomixer, a quantum cascade laser and a free electron laser, proofing the versatility and large applicability of the detection concept.