Photonic Crystal Heterostructure Cavity Research Articles

Enhanced Photon-Pair Generation Based on Thin-Film Lithium Niobate Doubly Resonant Photonic Crystal Cavity

In this work, a doubly resonant photonic crystal (PhC) cavity is proposed to enhance second harmonic generation (SHG) efficiency and photon pair generation rate (PGR). Through the exploration of geometry parameters, a band-edge mode within the light cone is identified as the first harmonic (FH) mode, and a band-edge mode outside the light cone is designated as the second harmonic (SH). Subsequently, by increasing the layers of the core region, a heterostructure PhC cavity is designed. The results showcase a doubly resonant PhC cavity achieving a 133/W SHG efficiency and a photon pair generation rate of 3.7 × 108/s. The exceptional conversion efficiency is attributed to the high quality factors Q observed in the FH and SH modes with values of approximately 280,000 and 2100, respectively. The remarkably high Q factors compensate for nonlinear efficiency degradation caused by detuning, simultaneously making the manufacturing process easier and more feasible. This work is anticipated to provide valuable insights into efficient nonlinear conversion and photon pair generation rates.

Superconducting nanowire single-photon detector implemented in a 2D photonic crystal cavity

The combination of efficient single-photon generation, manipulation, and detection on a single chip poses a major challenge for quantum photonics and all-optical quantum computing. Among a multitude of detection technologies, waveguide-integrated superconducting nanowire single-photon detectors stand out as they promise near-unity detection efficiencies at outstanding timing accuracy and speed. Here, by exploiting the concept of critical coupling, we present the integration of a short nanowire into a two-dimensional double heterostructure photonic crystal cavity to realize an integrated single-photon detector with excellent performance metric. The complete detector characterization reveals on-chip detection efficiencies of almost 70% at telecom wavelengths, recovery times of 480 ps, and vanishingly low dark count rates. Our design paves the way for the implementation of compact on-chip detector arrays and time-multiplexed single-detector schemes.

Low index contrast heterostructure photonic crystal cavities with high quality factors and vertical radiation coupling

We report here design and experimental demonstration of heterostructure photonic crystal cavities resonating near the Γ point with simultaneous strong lateral confinement and highly directional vertical radiation patterns. The lateral confinement is provided by a mode gap originating from a gradual modulation of the hole radii. High quality factor resonance is realized with a low index contrast between silicon nitride and quartz. The near surface-normal directional emission is preserved when the size of the core region is scaled down. The influence of the cavity size parameters on the resonant modes is also investigated theoretically and experimentally.

Band edge– and defect mode–induced emission from a photonic crystal heterostructure cavity

We numerically modeled and experimentally investigated a photonic crystal (PhC) heterostructure cavity with a three-dimensionally (3D) ordered colloidal PhC made from rhodamine-B dye-doped polymer colloids sandwiched between two identical dielectric multilayer stacks, for its influence on dye emission. In this cavity, we utilized the effect of overlap of the defect cavity mode of a multilayer stack with the band edge of 3D PhC to achieve enhancement and spectral narrowing in dye emission. The other defect modes, which do not overlap with the band edge, do not show this effect.

Vectorial Near-Field Imaging of Silicon Heterostructure Cavities in Air-Slot Waveguides

Air-slot photonic nanocavities have many relevant advantages for hybrid integration of external light emitters/absorbers in Si-based optoelectronic devices. Still an experimental major drawback is the difficulty of performing near-field polarization mapping of the photonic modes localized in air-regions. Here, we demonstrate that near-field resonant transmission can achieve high-fidelity vectorial imaging of the electric-field distribution of a nanocavity mode in the challenging case of a silicon heterostructure photonic-crystal cavity realized in an air-slot waveguide where the mode is localized both in air and dielectric regions. We discern and control the in-plane independent polarization components of the electric field of the photonic mode by exploiting the Fano imaging technique. The use of metallic coated aperture near-field probes allows to map the two polarizations with a deep sub-wavelength imaging ( $\lambda $ /15) resolution.

SOI Slotted Photonic Crystal Cavities Spanning From 1.3 to <inline-formula> <tex-math notation="LaTeX">$1.6~\mu \text{m}$ </tex-math></inline-formula> With <inline-formula> <tex-math notation="LaTeX">$Q/V$ </tex-math></inline-formula> Factors Above 800 000

A series of slot Si-on-SiO2 photonic crystal heterostructure cavities with resonant wavelengths ranging from 1.28 to $1.6~\mu \text{m}$ is reported. These cavities, presenting $Q/V$ factors typically around 800 000, can be used for the hybrid integration of various active materials within the silicon photonics platform.

Enhanced and suppressed spontaneous emission from a buried heterostructure photonic crystal cavity

We study spontaneous emission control in a buried-heterostructure (BH) photonic crystal (PhC) cavity in which InGaAsP quantum wells (QWs) are embedded in an InP PhC. Spontaneous emission from QW-PhC cavities have been extensively investigated, but they suffer from poor carrier confinement and surface non-radiative recombination. Therefore, the clear spontaneous emission control has been only observed in quantum dots PhC cavities. The present study shows that the BH-QW-PhC cavities can exhibit distinctive spontaneous emission control in QW-PhCs. We observed large emission-rate ratio between the on- and off-resonant conditions of 30:1. This is the highest ratio reported for QW-PhCs.

Photonic crystal nanocavities fabricated from chalcogenide glass fully embedded in an index-matched cladding with a high Q-factor (>750,000)

We have designed and fabricated a 2-D photonic crystal hetero-structure cavity in the chalcogenide glass Ge(11.5)As(24)Se(64.5) that is fully embedded in a cladding with refractive index of 1.44. The low index contrast of this structure (≈1.21) means that high-Q resonances cannot be obtained using standard hetero-structure cavity designs based on W1 waveguides. We show that reducing the waveguide width can substantially improve light confinement, leading to high-Q resonances in a hetero-structure cavity. Numerical simulations indicate intrinsic Q(v) > 10(7) are possible with this approach. Experimentally, an optical cavity with a high intrinsic Q(v)>7.6 x 10(5) was achieved in a structure with a theoretical Q(v) = 1.7 x 10(6).

Nested Photonic Crystal Cavity for On-Chip Wavelength Conversion

We propose a nested photonic crystal (PhC) cavity configuration for on-chip wavelength conversion applications based on adiabatic tuning of a resonator. The structure consists of a statically formed heterostructure PhC cavity embedded within a second, outer heterostructure cavity. The latter is subsequently formed by dynamic tuning of the slab refractive index. Switching between two distinct cavities, by combining structural change with index change, significantly extends the achievable frequency conversion range.

Optical resonances created by photonic transitions

We show that a high-Q optical resonance can be created dynamically, by inducing a photonic transition between a localized state and a one-dimensional continuum through refractive index modulation. In this mechanism, both the frequency and the external linewidth of a single resonance are specified by the dynamics, allowing complete control of the resonance properties. An example using photonic crystal heterostructure cavity is demonstrated with numerical simulation. We also show that the reported effect can be accomplished with realistic index modulation strength and frequencies.

Wavelength conversion by interband transition in a double heterostructure photonic crystal cavity

Optical wavelength conversion over an ultrawide spectral range based on an intermodal transition induced by dynamic tuning of a double heterostructure photonic crystal cavity is numerically demonstrated. Exploiting the inherently large spectral separation between the eigenmodes and the field symmetries to suppress multiple mode couplings, a normalized wavelength shift of about 25% with feasible index tuning is achievable by coupling only two resonances.

Optical properties of photonic crystal heterostructure cavity lasers

We design, fabricate, and test photonic crystal heterostructure cavity lasers in the InP material system. A heterostructure cavity is formed by interfacing two different photonic crystals such that a dispersion maximum of the inner lattice lies within the band gap of the surrounding lattice. Feedback to slow light modes of the central region results in a lower threshold and single mode operation. The use of a kagome lattice as the inner defect area increases the semiconductor volume as well as the modal overlap with the gain material. We use a simulation technique to verify experimentally observed single mode operation as well as to quantify the effects of the heterostructure cavity formation.

Electro-optical modulator in a polymerinfiltrated silicon slotted photonic crystal waveguide heterostructure resonator

We present a novel concept of a compact, ultra fast electro-optic modulator, based on photonic crystal resonator structures that can be realized in two dimensional photonic crystal slabs of silicon as core material employing a nonlinear optical polymer as infiltration and cladding material. The novel concept is to combine a photonic crystal heterostructure cavity with a slotted defect waveguide. The photonic crystal lattice can be used as a distributed electrode for the application of a modulation signal. An electrical contact is hence provided while the optical wave is kept isolated from the lossy metal electrodes. Thereby, well known disadvantages of segmented electrode designs such as excessive scattering are avoided. The optical field enhancement in the slotted region increases the nonlinear interaction with an external electric field resulting in an envisaged switching voltage of approximately 1 V at modulation speeds up to 100 GHz.

Coupled photonic crystal heterostructure nanocavities

We show the first experimental demonstration of multiple heterostructure photonic crystal cavities being coupled together to form a chain of coupled resonators with up to ten cavities. This system allows us to engineer the group velocity of light over a wide range. Devices were fabricated using 193 nm deep UV lithography and standard silicon processing technology. Structures were analysed using both coupled resonator and photonic bandstructure theory, and we highlight the discrepancies arising from subtle imperfections of the fabricated structure.