Search

In this paper, we show that patterned metallic surfaces can support localized resonant modes if a suitable defect in the periodicity of the structure is introduced. For those modes, optical losses due to radiative leakage perpendicular to the metallic plane can be significantly reduced by properly tuning the geometry of the defect-mode surface cavity. A design strategy based on the investigation of the electromagnetic field in the reciprocal space is suggested. [ABSTRACT FROM AUTHOR]

We demonstrate experimentally that the fiber to fiber total insertion loss into a single-mode waveguide in a suspended photonic crystal membrane can be reduced to less than 10 dB (input, output, and propagation) without introducing any supplementary processing step (e.g., polymer deposition and etching). This is achieved through a suitable design of the waveguide end-facets minimizing the impedance mismatch and thereby the residual reflectance at the waveguide ends. [ABSTRACT FROM AUTHOR]

The typical approaches to generate heralded single photons rely on parametric processes, with the advantage of generating highly entangled states at the price of a random pair emission. To overcome this limit, degenerate spontaneous Four-Wave-Mixing is a reliable technique which combines two pump photons into a pair of signal and idler photons via Kerr nonlinear optical effect. By exploiting the intrinsic small confinement volume and thermally tuning the resonances of a 20 μm-long Photonic Crystal cavity, we efficiently generate time-energy entangled photon pairs and heralded single photons at a large maximum on-chip rate of 22 MHz, using 36 μW of pump power. We measure time-energy entanglement with net visibility up to 96.6 % using 1 second integration time constant. Our measurements demonstrate the viability of Photonic Crystal cavities to act as an alternative and efficient photon pair source for quantum photonics. The generation of entangled photon pairs in an integrated platform is important for quantum technologies. This work experimentally demonstrates time-energy entangled photon pair generation from a suspended InGaP photonic crystal cavity with high pair generation rate, using a bichromatic lattice and thermal tuning. [ABSTRACT FROM AUTHOR]

A Finite Difference Time Domain approach is used to design and to optimize quantum-well based infrared photodetectors. Results showing the influence of some parameters on the performance of these devices are presented and discussed. [ABSTRACT FROM AUTHOR]

The potential of GaAs-based photonic crystals for fast all-optical switching in the telecom spectral range is exploited by controlling the surface recombination and, thereby, the carrier relaxation dynamics. The structure is entirely coated with a layer of aluminium oxide using atomic layer deposition. This results in a carrier lifetime of about 10 ps, as determined by spectrally resolved pump-probe measurements. We show that the nonlinear response of the resonator is optimized when it is excited with a few-picoseconds pulse. This dynamics is perfectly captured by our model accounting for the carrier diffusion with an impulse response function. Moreover, the suppression of photo-induced oxidation is revealed to be crucial to demonstrate all-optical operation at GHz rates with average coupled pump power of 0.5 mW (hence 100 fJ/bit). The switching window is 12 ps wide (1/e), as resolved by homodyne pump-probe measurements. The devices respond to a sequence of closely spaced pump pulses demonstrating a gating window close to 10 ps, with a contrast as high as 7 dB. [ABSTRACT FROM AUTHOR]

We perform spatially dependent tuning of a GaInP photonic crystal cavity using a continuous wave violet laser. Local tuning is obtained by laser heating of the photonic crystal membrane. The cavity resonance shift is measured for different pump positions and for two ambient gases: He and N2. We find that the width of the temperature profile induced in the membrane depends strongly on the thermal conductivity of the ambient gas. For He gas, a narrow spatial width of the temperature profile of 2.8 μm is predicted and verified in experiment. [ABSTRACT FROM AUTHOR]

The influence of scattering and two-photon absorption on the optical loss in GaAs-Al[sub 2]O[sub 3] semiconductor nonlinear waveguides has been studied using femtosecond pulses. By deploying a scattering technique, loss coefficients were evaluated over an extended wavelength range of 1.3-2.1 μm in the near-infrared. A systematic study involving intensity and wavelength dependence of the loss revealed the presence of two-photon absorption for wavelengths below 1.6 μm. A simple nonlinear transmission study enabled the separation of the two-photon absorption coefficient from scattering and linear absorption. The calculated two-photon absorption coefficients were ∼9-20 cm/GW. [ABSTRACT FROM AUTHOR]

Mode locking is predicted in a nanolaser cavity forming an effective photonic harmonic potential. The cavity is substantially more compact than a Fabry-Perot resonator with a comparable pulsing period, which is here controlled by the potential. In the limit of instantaneous gain and absorption saturation, mode locking corresponds to a stable dissipative soliton, which is very well approximated by the coherent state of a quantum mechanical harmonic oscillator. This property is robust against noninstantaneous material response and nonzero phase-intensity coupling. [ABSTRACT FROM AUTHOR]

We report on a new approach of a low phase noise electro-optomechanical oscillator directly working in the GHz frequency range. The developed nanoscale oscillator is a one-dimensional photonic crystal made of gallium phosphide (GaP), heterogeneously integrated on silicon-on-insulator circuitry. Based on the strong interaction between the optical mode at the telecommunication wavelength and the mechanical mode in GHz, ultra-pure mechanical oscillations are enabled and directly imprinted on an optical carrier. Further stabilization is achieved with a delayed optoelectronic feedback loop using integrated electro-mechanical self-injection. We achieve a short-term stability of 0.7 Hz linewidth and a long-term stability with an Allan deviation below 10 -7 Hz/Hz at 10 s averaging time, which represents an important step toward fully integrated optomechanical oscillators. Integrability and the low phase noise of this oscillator address some of the most important needs of optoelectronic oscillators and pave the way toward on-chip integrated microwave oscillators for microwave applications such as RADARs., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

We theoretically investigate the noise properties of harmonic cavity nanolasers by introducing a model of coupled equations of evolution of the modes, taking spontaneous emission into account. This model is used to predict the noise among the nanolaser Hermite-Gaussian modes, both in continuous wave and mode-locked regimes. In the first case, the laser noise is described in terms of noise modes, thus illustrating the role of the laser dynamics. In the latter case, this leads to the calculation of the fluctuations of the pulse train parameters. The influence of the different laser parameters, including the amount of saturated absorption and the Henry factors, on the noise of the mode-locked regime is discussed in details.

We theoretically and experimentally investigate type II second harmonic generation in III-V-on-insulator wire waveguides. We show that the propagation direction plays a crucial role and that longitudinal field components can be leveraged for robust and efficient conversion. We predict that the maximum theoretical conversion is larger than that of type I second harmonic generation for similar waveguide dimensions and reach an experimental conversion efficiency of 12%/W, limited by the propagation loss.

We theoretically analyze the robustness to potential distortion of mode-locking in a harmonic cavity nanolaser sustaining oscillation of Hermite-Gaussian modes. Different types of imperfections of the harmonic potential that create the Hermite-Gaussian modes are considered: the non-parabolicity of the potential and the possible random errors in the shape of the potential. The influence of the different laser parameters, including the Henry factors of the gain medium and the saturable absorber, on the robustness of the mode-locked regime is discussed in detail.

We report a new class of Optical Parametric Oscillators, based on a 20 μm -long semiconductor Photonic Crystal Cavity and operating at Telecom wavelengths. Because the confinement results from Bragg scattering, the optical cavity contains a few modes, approximately equispaced in frequency. Parametric oscillation is reached when these high Q modes are thermally tuned into a triply resonant configuration, whereas any other parametric interaction is strongly suppressed. The lowest pump power threshold is estimated to 50 - 70 μW . This source behaves as an ideal degenerate Optical Parametric Oscillator addressing the needs in the field of quantum optical circuits, paving the way to the dense integration of highly efficient nonlinear sources of squeezed light or entangled photons pairs., Competing Interests: Additional Information The authors declare no competing interests.

Mode locking is predicted in a nanolaser cavity forming an effective photonic harmonic potential. The cavity is substantially more compact than a Fabry-Perot resonator with a comparable pulsing period, which is here controlled by the potential. In the limit of instantaneous gain and absorption saturation, mode locking corresponds to a stable dissipative soliton, which is very well approximated by the coherent state of a quantum mechanical harmonic oscillator. This property is robust against noninstantaneous material response and nonzero phase-intensity coupling.

Resonant cavities with high quality factor and small mode volume provide crucial enhancement of light-matter interactions in nanophotonic devices that transport and process classical and quantum information. The production of functional circuits containing many such cavities remains a major challenge, as inevitable imperfections in the fabrication detune the cavities, which strongly affects functionality such as transmission. In photonic crystal waveguides, intrinsic disorder gives rise to high- Q localized resonances through Anderson localization; however their location and resonance frequencies are completely random, which hampers functionality. We present an adaptive holographic method to gain reversible control on these randomly localized modes by locally modifying the refractive index. We show that our method can dynamically form or break highly transmitting necklace states, which is an essential step toward photonic-crystal-based quantum networks and signal processing circuits, as well as slow light applications and fundamental physics., Competing Interests: The authors declare no competing financial interest.

Generating and amplifying light in silicon (Si) continues to attract significant attention due to the possibility of integrating optical and electronic components in a single material platform. Unfortunately, silicon is an indirect band gap material and therefore an inefficient emitter of light. With the rise of integrated photonics, the search for silicon-based light sources has evolved from a scientific quest to a major technological bottleneck for scalable, CMOS-compatible, light sources. Recently, emerging two-dimensional materials have opened the prospect of tailoring material properties based on atomic layers. Few-layer phosphorene, which is isolated through exfoliation from black phosphorus (BP), is a great candidate to partner with silicon due to its layer-tunable direct band gap in the near-infrared where silicon is transparent. Here we demonstrate a hybrid silicon optical emitter composed of few-layer phosphorene nanomaterial flakes coupled to silicon photonic crystal resonators. We show single-mode emission in the telecommunications band of 1.55 μm ( E g = 0.8 eV) under continuous wave optical excitation at room temperature. The solution-processed few-layer BP flakes enable tunable emission across a broad range of wavelengths and the simultaneous creation of multiple devices. Our work highlights the versatility of the Si-BP material platform for creating optically active devices in integrated silicon chips.

A two dimensional photonic crystal (PhC) resonator, based on a recent design concept, entirely embedded in Silica, is fabricated in a CMOS full-process multiproject wafer, including additional steps such as implantation, metalization, Germanium deposition and planarization. A large loaded Q-factor (5.9 × 10 5 ) is achieved without removal of the silica cladding. A statistical analysis over 56 devices leads to an average value for the loaded Q of 4 × 10 5 , in close agreement with calculations. An upper boundary for the fabrication disorder is estimated to 1.2 nm.

We demonstrate that conformal encapsulation using atomic layer deposition of GaAs nano-cavity resonator made of photonic crystal cavity prevents photo-induced oxidation. This improvement allows injecting a large quantity of energy in the resonator without any degradation of the material, thus enabling spectral stability of the resonance. We prove second harmonic and third harmonic generation over more than one decade of pump power variation, thanks to this encapsulation, with a total efficiency (ηSHG = 8.3 × 10 -5 W -1 and ηTHG = 1.2 × 10 -3 W -2 ) and a large net output energy for both operations (PSHGout=0.2nW and PTHGout=8pW).

Ga 0.51 In 0.49 P is a promising candidate for thermally tunable nanophotonic devices due to its low thermal conductivity. In this work we study its thermo-optical response. We obtain the linear thermo-optical coefficient dn/dT=2.0±0.3·10 -4   K -1 by investigating the transmission properties of a single mode-gap photonic crystal nanocavity.

Weakly coupled high-Q nanophotonic cavities are building blocks of slow-light waveguides and other nanophotonic devices. Their functionality critically depends on tuning as resonance frequencies should stay within the bandwidth of the device. Unavoidable disorder leads to random frequency shifts which cause localization of the light in single cavities. We present a new method to finely tune individual resonances of light in a system of coupled nanocavities. We use holographic laser-induced heating and address thermal crosstalk between nanocavities using a response matrix approach. As a main result we observe a simultaneous anticrossing of 3 nanophotonic resonances, which were initially split by disorder.

We demonstrated a twofold acceleration of the fast time constant characterizing the recovery of a p-doped indium-phosphide photonic crystal all-optical gate. Time-resolved spectral analysis is compared to a three-dimensional drift-diffusion model for the carrier dynamics, demonstrating the transition from the ambipolar to the faster minority carrier dominated diffusion regime. This opens the perspective for faster yet efficient nanophotonic all-optical gates.

Heat dissipation is improved in nonlinear III-V photonic crystal waveguides owing to the hybrid III-V/Silicon integration platform, allowing efficient four-wave mixing in the continuous-wave regime. A conversion efficiency of -17.6  dB is demonstrated with a pump power level below 100 mW in a dispersion-engineered waveguide with a flat group index of 28 over a 10 nm bandwidth.

Near the band edge of photonic crystal waveguides, localized modes appear due to disorder. We demonstrate a new method to elucidate spatial profile of the localized modes in such systems using precise local tuning. Using deconvolution with the known thermal profile, the spatial profile of a localized mode with quality factor (Q) > 10 5 is successfully reconstructed with a resolution of 2.5 μm.

The dispersion of a coupled resonator optical waveguide made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the inherent dispersive cavity mode profile; i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. We formulate a dispersive mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.

A compact (15µm × 15µm) and highly-optimized 2×2 optical switch is demonstrated on a CMOS-compatible photonic crystal technology. On-chip insertion loss are below 1 dB, static and dynamic contrast are 40 dB and >20 dB respectively. Owing to efficient thermo-optic design, the power consumption is below 3 mW while the switching time is 1 µs.

We demonstrate the generation of an octave-spanning supercontinuum in InGaP membrane waveguides on a silicon substrate pumped by a 1550-nm femtosecond source. The broadband nature of the supercontinuum in these dispersion-engineered high-index-contrast waveguides is enabled by dispersive wave generation on both sides of the pump as well as by the low nonlinear losses inherent to the material. We also measure the coherence properties of the output spectra close to the pump wavelength and find that the supercontinuum is highly coherent at least in this wavelength range.

We propose high index contrast InGaP photonic wires as a platform for the integration of nonlinear optical functions in the telecom wavelength window. We characterize the linear and nonlinear properties of these waveguide structures. Waveguides with a linear loss of 12 dB/cm and which are coupled to a single mode fiber through gratings with a -7.5 dB coupling loss are realized. From four wave mixing experiments, we extract the real part of the nonlinear parameter γ to be 475 ± 50 W(-1)m(-1) and from nonlinear transmission measurements we infer the absence of two-photon absorption and measure a three-photon absorption coefficient of (2.5 ± 0.5) x 10(-2) cm(3)GW(-2).

We haves realized and measured a GaAs nanocavity in a slab photonic crystal based on the design by Kuramochi et al. [Appl. Phys. Lett. 88, 041112 (2006)]. We measure a quality factor Q=700,000, which proves that ultrahigh Q nanocavities are also feasible in GaAs. We show that owing to larger two-photon absorption in GaAs nonlinearities appear at the microwatt level and will be more functional in gallium arsenide than in silicon nanocavities.