100,457 research outputs found
Selective tuning of optical modes in a silicon comb-like photonic crystal cavity
No full textRealizing multiply resonant photonic crystal cavities with large free spectral range is key to achieve integrated devices with highly efficient nonlinear response, such as frequency conversion, four-wave mixing, and parametric oscillation. This task is typically difficult owing to the cavity modes' sensitivity to fabrication disorder, which makes it hard to reliably achieve a comb-like spectrum of equally spaced modes even when a perfect matching is theoretically predicted. Here we show that a comb-like spectrum of up to eight modes with very high quality factor and diffraction limited volumes can be engineered in the bichromatic-type potential of a two-dimensional photonic crystal cavity fabricated in a thin silicon membrane. To cope with the tight tolerance in terms of frequency spacings and resonance linewidths, we develop a permanent post-processing technique that allows the selective tuning of individual confined modes, thus achieving an almost perfect frequency matching of high Q resonances with record finesse in silicon microresonators. Our experimental results are extremely promising in view of ultra-low power nonlinear photonics in silicon
Demonstration of optical frequency combs in photonic crystal cavities
No full textWe report on the design and fabrication of high-Q silicon photonic crystal cavities operating at telecom wavelength exhibiting quasi-equally spaced resonant modes and diffraction limited mode volumes. The cavities design is based on an a bichromatic geometry, resulting in a parabolic profile of the effective confinement potential in analogy with the quantum-mechanical harmonic oscillator. This naturally leads to a nearly equal spacing of the set of resonant modes and Gaussian envelope of the field profile. The fabricated devices exhibit Q factors exceeding one million on multiple modes, as experimentally determined by resonant scattering measurements, and comb-like spectral features. The extremely large field enhancement achievable with these devices, together with the peculiar spectral properties represent a promising platform for scalable integrated nonlinear optical applications based on optical frequency combs
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Resonator fabrication for switchable two-color MIR detectors based on p-type SiGe quantum cascade injectors
No full textSiGe quantum well infrared photodetectors on strained-silicon-on-insulator
No full textWe demonstrate p-type SiGe quantum well infrared photodetectors (QWIPs) on a strained-silicon-on-insulator (sSOI) substrate. The sSOI system allows strain-balancing between the QWIP heterostructure with an average composition of Si0.7Ge0.3 and the substrate, and therefore lifts restrictions to the active material thickness faced by SiGe growth on silicon or silicon-on-insulator substrates. The realized sSOI QWIPs feature a responsivity peak at detection wavelengths around 6 μm, based on a transition between heavy-hole states. The fabricated devices have been thoroughly characterized and compared to equivalent material simultaneously grown on virtual Si0.7Ge0.3 substrates based on graded SiGe buffers. Responsivities of up to 3.6 mA/W are achieved by the sSOI QWIPs at 77 K, demonstrating the large potential of sSOI-based devices as components for a group-IV optoelectronic platform in the mid-infrared spectral region
Silicon Photonic Crystal Cavities for Integrated Quantum Photonics
No full textWe report the generation of nonclassical states of light through parametric fluorescence in a silicon photonic crystal cavity with equally spaced resonances. A bichromatic cavity design was adopted to obtain a comb-like resonance spectrum, while mode-selective tuning by laser-assisted local oxidation was used to fine adjustment of the resonance frequencies after fabrication, thus achieving almost perfect equally-spaced modes. Both stimulated and spontaneous four-wave mixing were observed. The generation of correlated single photon pairs was confirmed through coincidence measurements
Silicon Photonic Crystal Cavities for Spontaneous Four-Wave Mixing
No full textWe report the generation of nonclassical states of light through parametric fluorescence in a silicon photonic crystal cavity with equally spaced resonances in energy. The time correlation of photon pairs is confirmed by coincidence measurements
Generation of entangled photon pairs from a silicon bichromatic photonic crystal cavity
No full textIntegrated quantum photonics leverages the on-chip generation of nonclassical states of light to realize key functionalities of quantum devices. Typically, the generation of such nonclassical states relies on whispering gallery mode resonators, such as integrated optical micro-rings, which enhance the efficiency of the underlying spontaneous nonlinear processes. While these kinds of resonators excel in maximizing either the temporal confinement or the spatial overlap between different resonant modes, they are usually associated with large mode volumes, imposing an intrinsic limitation on the efficiency and footprint of the device. Here, we engineer a source of time-energy entangled photon pairs based on a silicon photonic crystal cavity, implemented in a fully CMOS-compatible platform. In this device, resonantly enhanced spontaneous four-wave mixing converts pump photon pairs into signal/idler photon pairs under the energy-conserving condition in the telecommunication C-band. The design of the resonator is based on an effective bichromatic confinement potential, allowing it to achieve up to nine close-to-equally spaced modes in frequency, while preserving small mode volumes, and the whole chip, including grating couplers and access waveguides, is fabricated in a single run on a silicon-on-insulator platform. Besides demonstrating efficient photon pair generation, we also implement a Franson-type interference experiment, demonstrating entanglement between signal and idler photons with a Bell inequality violation exceeding five standard deviations. The high generation efficiency combined with the small device footprint in a CMOS-compatible integrated structure opens a pathway toward the implementation of compact quantum light sources in all-silicon photonic platforms
High-Q/V photonic crystal cavities realized by an effective Aubry-Andre-Harper bichromatic potential
No full textWe report on the realization of high-Q/V silicon photonic crystal cavities with resonance wavelengths in the telecom window around 1.55 mu m. The cavity designs are based on an effective Aubry-Andre-Harper bichromatic potential, defined by the superposition of two one-dimensional lattices with an incommensurate ratio between their periodicity constants. This peculiar confinement mechanism allows to achieve an ultra-high-Q factor and diffraction-limited mode volume. Several photonic crystal nanocavities in a silicon membrane geometry have been realized with measured Q-factors in the one million range, as determined by resonant scattering experiments. The generality of the proposed designs and their easy implementation and scalability make these results particularly interesting for realizing highly performing photonic nanocavities on different material platforms and operational wavelengths
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