The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm(-2)) and high quality factors (Q ∼ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 10(16) cm(-3). Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors

The arbitrary control of electromagnetic waves is a key aim of photonic research. Although, for example, the control of freely propagating waves (PWs) and surface waves (SWs) has separately become possible using transformation optics and metamaterials, a bridge linking both propagation types has not yet been found. Such a device has particular relevance given the many schemes of controlling electromagnetic waves at surfaces and interfaces, leading to trapped rainbows, lensing, beam bending, deflection, and even anomalous reflection/refraction. Here, we demonstrate theoretically and experimentally that a specific gradient-index meta-surface can convert a PW to a SW with nearly 100% efficiency. Distinct from conventional devices such as prism or grating couplers, the momentum mismatch between PW and SW is compensated by the reflection-phase gradient of the meta-surface, and a nearly perfect PW-SW conversion can happen for any incidence angle larger than a critical value. Experiments in the microwave region, including both far-field and near-field characterizations, are in excellent agreement with full-wave simulations. Our findings may pave the way for many applications, including high-efficiency surface plasmon couplers, anti-reflection surfaces, light absorbers, and so on.

http://www.physics.fudan.edu.cn/tps/people/lzhou/papers/84-NM%2011,426.pdf

Gradient-index meta-surfaces as a bridge linking propagating waves and surface waves

Reliable, efficient electrically pumped silicon-based lasers would enable full integration of photonic and electronic circuits, but have previously only been realized by wafer bonding. Here, we demonstrate continuous-wave InAs/GaAs quantum dot lasers directly grown on silicon substrates with a low threshold current density of 62.5 A cm–2, a room-temperature output power exceeding 105 mW and operation up to 120 °C. Over 3,100 h of continuous-wave operating data have been collected, giving an extrapolated mean time to failure of over 100,158 h. The realization of high-performance quantum dot lasers on silicon is due to the achievement of a low density of threading dislocations on the order of 105 cm−2 in the III–V epilayers by combining a nucleation layer and dislocation filter layers with in situ thermal annealing. These results are a major advance towards reliable and cost-effective silicon-based photonic–electronic integration.

/pdf/electrically-pumped-continuous-wave-iii-v-quantum-dot-lasers-rmg1qnqnyt.pdf

Electrically pumped continuous-wave III–V quantum dot lasers on silicon

A laser frequency comb is a broad spectrum composed of equidistant narrow lines. Initially invented for frequency metrology, such combs enable new approaches to spectroscopy over broad spectral bandwidths, of particular relevance to molecules. The performance of existing spectrometers — such as crossed dispersers employing, for example, virtual imaging phase array etalons, or Michelson-based Fourier transform interferometers — can be dramatically enhanced with optical frequency combs. A new class of instruments, such as dual-comb spectrometers without moving parts, enables fast and accurate measurements over broad spectral ranges. The direct self-calibration of the frequency scale of the spectra within the accuracy of an atomic clock and the negligible contribution of the instrumental line-shape will enable determinations of all spectral parameters with high accuracy for stringent comparisons with theories in atomic and molecular physics. Chip-scale frequency comb spectrometers promise integrated devices for real-time sensing in analytical chemistry and biomedicine. This Review gives a summary of the developments in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy with frequency combs. Frequency comb spectroscopy is a recent field of research that has blossomed in the past five years. This Review discusses developments in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy with frequency combs.

Frequency comb spectroscopy

The conversion from spatial propagating waves to surface plasmon polaritons (SPPs) has been well studied, and shown to be very efficient by using gradient-index metasurfaces. However, feeding energies into and extracting signals from functional plasmonic devices or circuits through transmission lines require the efficient conversion between SPPs and guided waves, which has not been reported, to the best of our knowledge. In this paper, a smooth bridge between the conventional coplanar waveguide (CPW) with 50 Ω impedance and plasmonic waveguide (e.g., an ultrathin corrugated metallic strip) has been proposed in the microwave frequency, which converts the guided waves to spoof SPPs with high efficiency in broadband. A matching transition has been proposed and designed, which is constructed by gradient corrugations and flaring ground, to match both the momentum and impedance of CPW and the plasmonic waveguide. Simulated and measured results on the transmission coefficients and near-filed distributions show excellent transmission efficiency from CPW to a plasmonic waveguide to CPW in a wide frequency band. The high-efficiency and broadband conversion between SPPs and guided waves opens up a new avenue for advanced conventional plasmonic integrated functional devices and circuits.

Broadband and high-efficiency conversion from guided waves to spoof surface plasmon polaritons

We demonstrate an ultra-low threshold nanowire laser monolithically integrated on a (001) silicon substrate. By using a V-groove template we were able to reduce the laser threshold by one order of magnitude (0.19pJ per pulse) compared with our earlier devices and dramatically increased the yield throughout the wafer.

https://biblio.ugent.be/publication/5872540/file/5872556.pdf

InP nanowire lasers epitaxially grown on (001) silicon ‘V-groove’ templates

Silicon-on-insulator material structure allows for very high light confinement in the silicon core due to its high refractive index. The advantages of this technology include the possibility to miniaturize devices and integrate different functions on a single chip, reduction of optical loss and power consumption and potential perspectives for low cost mass production in CMOS technology line. Together with these advantages some new problems appear in comparison to weakly guided light in silica-on-silicon components, causing additional challenges for researchers to be solved. Besides much higher demands for fabrication accuracy, high refractive index contrast introduces additional optical input/output coupling problems as well as much higher polarization sensitivity of nanophotonic structures. Here we will propose some solutions for these problems and illustrate them with designed and fabricated components.

Interfacing of silicon-on-insulator nanophotonic circuits to the real world

Based on hybrid plasmonic waveguides, microdisk resonators with radii of 0.5 µm and FSRs of about 200 nm are simulated and experimentally demonstrated. Thermal tuning of the devices in 6 nm range is also presented.

A sub-wavelength microdisk resonator based on hybrid plasmonic waveguides

An ultrasmall polarization rotator based on asymmetrical Si nanowires is presented. Almost 100% polarization rotation is achieved with a very small beat length (~10 m). And a broad 3-dB bandwidth (~120 nm) is obtained.

An ultrasmall polarization rotator based on Si nanowire

A novel epitaxial lateral overgrowth (ELOG) technology-based monolithic integration platform for silicon photonics is demonstrated. High quality, defect-free InP ELOG mesa has been experimentally obtained on silicon by using hydride vapor phase epitaxy (HVPE). The proposed platform provides unique advantages for the realization of active devices on silicon.

Zhechao Wang

Papers

InP nanowire lasers epitaxially grown on (001) silicon ‘V-groove’ templates

Interfacing of silicon-on-insulator nanophotonic circuits to the real world

A sub-wavelength microdisk resonator based on hybrid plasmonic waveguides

An ultrasmall polarization rotator based on Si nanowire

A monolithic integration platform for silicon photonics