We report the fabrication of a photonic platform consisting of single wire light-emitting diodes (LED) and photodetectors optically coupled by waveguides. MOVPE-grown (metal-organic vapor-phase epitaxy) InGaN/GaN p-n junction core-shell nanowires have been used for device fabrication. To achieve a good spectral matching between the emission wavelength and the detection range, different active regions containing either five narrow InGaN/GaN quantum wells or one wide InGaN segment were employed for the LED and the detector, respectively. The communication wavelength is ∼400 nm. The devices are realized by means of electron beam lithography on Si/SiO2 templates and connected by ∼100 μm long nonrectilinear SiN waveguides. The photodetector current trace shows signal variation correlated with the LED on/off switching with a fast transition time below 0.5 s.

ABSTRACT:Heterogeneous integration of III-V semiconductor compounds on Silicon on Insulator wafers is one the key technology for next generation on chip optical interconnects. Within this context the use of photonic crystals lasers represent a disruptive solution in terms of footprint, activation energy and ultrafast response. In this work, we propose and fabricate very compact laser sources integrated with a passive silicon waveguide circuitry, taking advantage of the efficient emission from III-V semiconductor photonic crystal nanocavities. Such micro sources often radiate only a fraction of their power into useful beams. Using a subjacent Silicon-On-Insulator waveguide we capture emitted light from the cavity, evanescently, and can also probe the cavity waveguide system in transmission in order to experimentally deduce the coupling factors.During the past decades, optical devices have played a crucial role in the domain of information and communication technology, due to their ability to bring efficient solutions to data transmission and processing. Indeed, optical communications have known tremendous development, through optical fibres backed by related devices and circuits composed of light sources, optical amplifiers, wavelength multiplexers, photodetectors, etc, which have greatly revolutionized telecommunication. Increasing attention is now being devoted to optical computer-com mainly concentrated in intra-and inter-chip interconnection applications [1,2], the convergence of optics and electronics at the chip level being a necessity for the next generation processors. Here, the issues that need to be tackled are the dispatching and sorting of the mind-boggling amount of information within small footprints and above all with reduced power consumption and dissipation [3].Thus, photonic circuits should be constituted of elements able to control perfectly the propagation of light with a view to achieve "passive" functions such as guiding and filtering as well as elements dedicated to active functions such as emission, detection, amplification, switching and a multitude of others capable of manipulating optical information at will.In this context, it is very unlikely that only one class of material will completely answer to all needs.Silicon photonics, enhanced by III-V based optical functions is considered to be as one of the key technologies combining the best of both materials leading to highly versatile hybrid photonics platform and opening up the field to large scale photonic integration. Indeed, Silicon transparency at telecom wavelengths and the high-index contrast with silica allows the fabrication of extremely compact lowloss single mode waveguides (~2dB/cm) [4,5] that can be used for bringing the information where it

We predict and experimentally observe the enhancement by three orders of magnitude of phase mismatched second and third harmonic generation in a GaAs cavity at 650 and 433 nm, respectively, well above the absorption edge. Phase locking between the pump and the harmonics changes the effective dispersion of the medium and inhibits absorption. Despite hostile conditions the harmonics resonate inside the cavity and become amplified leading to relatively large conversion efficiencies. Field localization thus plays a pivotal role despite the presence of absorption, and ushers in a new class of semiconductor-based devices in the visible and uv ranges.Since it was discovered by Franken in the 1960s, second harmonic ͑SH͒ generation has been one of the most studied phenomena in nonlinear optics ͓1͔. To date most efforts have been directed at improving the efficiency of the process by developing new materials with high effective nonlinear coefficients, accompanied by phase and group velocity matching ͓2-10͔. Consequently, most studies have been concerned with maximizing conversion efficiencies, generally achievable at or very near phase matching ͑PM͒ conditions, ensuring maximum energy transfer from the fundamental beam to the harmonics. A special effort was focused toward engineering new artificial materials capable of compensating material dispersion, for example, using quasiphase matching techniques ͓11,12͔ or structured materials ͓13͔. Outside of PM conditions, which generally coincide with low conversion efficiencies ͓3͔, the only relevant processes that have been investigated are cascaded parametric processes that can produce phase-modulation of the fundamental beam ͓14͔, pulse breaking ͓15͔ or nonlinear diffraction ͓16͔. This has caused other possible working conditions to remain largely unexplored. A relevant feature is that in all these previous studies the nonlinear material was assumed to be transparent for both fundamental and harmonics beams, since conventional wisdom holds that an absorptive material will reabsorb any generated harmonic signal.More recently, an effort was initiated to systematically study the behavior of SH and third harmonic ͑TH͒ fields in transparent and opaque materials under conditions of phase mismatch ͓17-19͔. Briefly, when a pump pulse crosses an interface between a linear and a nonlinear medium there are always three generated SH ͑and/or TH͒ components. One component is generated backward into the free space, due the presence of the interface, and the remaining components are forward moving. These components may be understood on the basis of the mathematical solution of the homogeneous and inhomogeneous wave equations at the SH frequency ͓4͔. Continuity of the tangential components of all the fields at the boundary leads to generation of the two forwardpropagating components that interfere in the vicinity of the entry surface and give rise to Maker fringes ͓2,20͔ and to energy exchange between the fundamentals and SH and/or TH beams. It turns out that while the homogeneous component tr...

The integration of two-dimensional III-V InP-based photonic crystal and silicon wire waveguides is achieved through an accurate alignment of the two optical levels using mix-and-match deep ultraviolet ͑DUV͒/electron beam lithography. The adhesively bonded structures exhibit an enhancement of light emission at frequencies where low group velocity modes of the photonic crystal line defect waveguides occur. Pulsed laser operation is obtained from these modes at room temperature under optical pumping. The laser light is coupled out of the Si waveguide via grating couplers directly to single mode fiber.

Absorption of single InGaAs self-assembled quantum dots is spatially resolved in resonance with the S to P polaron transitions around λ = 25 μm wavelength. We show that the spatial resolution down to 50 nm (λ/500) combined with the analysis of the absorption nanoscopy images provides a measurement of the homogeneous broadening at room temperature. The 2.5 ± 1 meV measured S-P homogeneous broadening supports the calculated value accounting for acoustic phonon-induced decoherence.

We demonstrate efficient surface-emitting terahertz frequency quantum cascade lasers with continuous wave output powers of 20-25 mW at 15 K and maximum operating temperatures of 80-85 K. The devices employ a resonant-phonon depopulation active region design with injector, and surface emission is realized using resonators based on graded photonic heterostructures (GPHs). GPHs can be regarded as energy wells for photons and have recently been implemented through grading the period of the photonic structure. In this paper, we show that it is possible to keep the period constant and grade instead the lateral metal coverage across the GPH. This strategy ensures spectrally singlemode operation across the whole laser dynamic range and represents an additional degree of freedom in the design of confining potentials for photons. V C 2014 AIP Publishing LLC.

We report on far field measurements on two coupled photonic crystal nanocavities. The distinct features of the antisymmetric modes (minima of intensity at zero-emission angles) allow us to demonstrate a π-phase difference between the cavity fields, a clear signature of evanescent coupling. Good agreement between experimental results and simulated radiation patterns has been found.

Photonic-crystal lasers operating on Γ-point band-edge states of a photonic structure naturally exploit the so-called "nonradiative" modes. As the surface output coupling efficiency of these modes is low, they have relatively high Q factors, which favor lasing. We propose a new 2D photonic-crystal design that is capable of reversing this mode competition and achieving lasing on the radiative modes instead. Previously, this has only been shown in 1D structures, where the central idea is to introduce anisotropy into the system, both at unit-cell and resonator scales. By applying this concept to 2D photonic-crystal patterned terahertz frequency quantum cascade lasers, surfaceemitting devices with diffraction-limited beams are demonstrated, with 17 mW peak output power. In the terahertz (THz) frequency range of the electromagnetic spectrum, several PhC design strategies have been applied to quantum cascade laser (QCL) technologies in recent years [5,6]. The goal has been to improve the shape and quality of the strongly divergent emission [5,6] and the power efficiency of the devices by using the confinement and/or the dispersion properties of periodically patterned (in 1D or 2D) metal-semiconductor-metal structures. To date, a coherent single-lobed emission with reduced divergence has been obtained in edgeemitting devices, using third-order distributed feedback (DFB) gratings [7,8], and in surface-emitting devices, using 2D PhCs [9,10] and second-order DFBs [11,12]. However, efficient power extraction and, hence, wallplug efficiency (WPE) from DFB-or PhC-patterned QCLs has been elusive. WPEs for these devices fall well below the current state-of-the-art for THz QCLs exploiting unpatterned single-plasmon waveguides, where values in the 0.5%-1% range are currently achieved at 10 K [5].The problem in achieving high WPE has a fundamental origin. 1D and 2D PhCs support two classes of modes at the high symmetry points in the band structure where PhC lasers usually operate. These modes are associated with either symmetric or antisymmetric electric field profiles on the scale of the unit cell. When located above the light line, both modes will give rise to emission but will result in constructive or destructive interference. THz frequency QCLs (and indeed all QCLs) are TM polarized, i.e., the electric field is aligned parallel to the growth (z) axis. Since surface emission originates from the in-plane components of the field in the holes/slits of 2D/1D PhCs, it is only the magnetic field component that sources the radiation [13]. As a general rule, antisymmetric modes with respect to E z are symmetric with respect to the in-plane H field in the slits/holes of the DFB/PhC and are, hence, labeled "radiative." Conversely, symmetric E z modes are antisymmetric with respect to the in-plane H field and are, hence, termed "nonradiative." In fact, radiative modes at the Γ point (k in-plane 0) naturally exhibit an emission maximum in the direction normal to the device surface. As a consequence, the following relation is always true:...