Chad Husko

Observation of femtojoule optical bistability involving fano resonances in high-Q/Vm silicon photonic crystal nanocavities

The authors observe experimentally optical bistability enhanced through Fano interferences in high-Q localized silicon photonic crystal resonances (Q∼30000 and modal volume ∼0.98 cubic wavelengths). This phenomenon is analyzed through nonlinear coupled-mode formalism, including the interplay of χ(3) effects such as two-photon absorption and related free-carrier dynamics, and optical Kerr as well as thermal effects and linear losses. Experimental and theoretical results demonstrate Fano resonance based bistable states with switching thresholds of 185μW and 4.5fJ internally stored cavity energy (∼540fJ consumed energy) in silicon for scalable optical buffering and logic.

High quality GaInP nonlinear photonic crystals with minimized nonlinear absorption

We have established a new material, indium gallium phosphide, lattice matched to gallium arsenide, for two-dimensional photonic crystals at 1.55u2002μm. We have demonstrated single-mode cavities with intrinsic Q-factor larger than one million and achieved very large self-phase-modulation coefficient 1.1×103u2002W1u2009m−1 in line-defect waveguides. Importantly, the material band gap is such that two-photon absorption, Eg>2ℏω, is completely suppressed at this important telecommunications wavelength.

Effect of multiphoton absorption and free carriers in slow-light photonic crystal waveguides

We examine the effects of multiphoton absorption, free carriers, and disorder-induced linear scattering in slow-light photonic crystal waveguides. We derive an analytic formulation for self-phase modulation including the group velocity scaling of the nonlinear phase shift in materials limited by three-photon absorption as a representative nonlinear process. We investigate the role of free carriers and derive an approximate critical intensity at which these effects begin to strongly modify the optical field. This critical intensity is employed to determine an optimal group index for the self-phase modulation in the slow-light devices. These observations are confirmed with numerical modeling.

Deterministic tuning of slow-light in photonic-crystal waveguides through the C and L bands by atomic layer deposition

We demonstrate digital tuning of the slow-light regime in silicon photonic-crystal waveguides by performing atomic layer deposition of hafnium oxide. The high group-index regime was deterministically controlled (redshift of 140±10u2002pm per atomic layer) without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential tuning of 110±30u2002pm per monolayer of the slow-light TE-like and TM-like modes was observed. This passive postfabrication process has potential applications including the tuning of chip-scale optical interconnects, as well as Raman and parametric amplification.

Observations of interior whispering gallery modes in asymmetric optical resonators with rational caustics

We propose asymmetric resonant cavities with rational caustics and experimentally demonstrate interior whispering gallery modes in monolithic silicon mesoscopic microcavities. These microcavities demonstrate unique robustness of cavity quality factor against roughness Rayleigh scattering. Distinct resonant families and directional radiation from interior whispering gallery modes are observed experimentally using angle-resolved tapered fiber measurements and near-field images, which can be used for microcavity laser and cavity quantum electrodynamics applications.

Observation of soliton pulse compression in photonic crystal waveguides

We demonstrate soliton-effect pulse compression in mm-long photonic crystal waveguides resulting from strong anomalous dispersion and self-phase modulation. Compression from 3ps to 580fs, at low pulse energies(∼10pJ), is measured via autocorrelation.

Digital resonance tuning of high-Q/V m silicon photonic crystal nanocavities by atomic layer deposition

We propose and demonstrate the digital resonance tuning of high-Q/Vm silicon photonic crystal nanocavities using self-limiting atomic layer deposition. Control of resonances of 122 plusmn 18 pm per hafnium oxide atomic layer is achieved.

Advances in III-V based photonic crystals for integrated optical processing

Compactness, massive integration of multiple functions on a single chip and power consumption are crucial for transmission of large aggregated bit rates at short distance. Efficient implementation of data processing at the optical level are very attractive. Here we present a technology for implementing ultra-fast switching with recordlow energy·recovery time product. We developed high-quality photonic crystal micro-resonators based on III-V semiconductors. The very short carrier lifetime of nano-pattened Gallium Arsenide enabled us to achieve 6 ps recovery time, thus enabling operations beyond the 100Gb/s rate. For broadband operation, highly nonlinear waveguides with low insertion loss have been demonstrated.

Negative refraction and nonlinearities in photonic bandgap nanostructures

Recent important advances in subwavelength nanostructures offer extraordinary control over the properties of light. We can now manipulate the propagation, storage, and generation of light, as well as practically prescribe light-matter interaction based on first-principles. Photonic crystals, in particular, offer the unique ability for arbitrary control of dispersion as well as ultrahigh quality factor (Q) and modal volume (Vm) nanocavities. In this talk, we will present, to our knowledge, the first near-field experimental observations of near-infrared subwavelength imaging in negative refraction photonic crystals, as well as discuss our efforts in enhanced nonlinearities in photonic crystal nanocavities.

Ultrafast all-optical bistability in AlGaAs photonic crystals

We present the design and fabrication of an all-optical bistable device in AlGaAs. The material is known to have a nonlinear figure-of-merit that is in larger silicon and thus well suited to nonlinear experiments. We employ theoretical analysis consisting of both analytical models and finite-difference time-domain (FDTD) methods to ensure robust design and to estimate the power threshold of the proposed device. The proposed nanocavity experiment suggests low powers (~102 μW) and ultra fast switching (~ps) on chip limited only by photon lifetime. This is an improvement over silicon based experiments, which have demonstrated ~ 100 nanosecond responses but intrinsically bounded by free-carrier dynamics [12]. In this manuscript, we will elaborate on theoretical and experimental considerations required to implement a low power, ultrafast bistable device that forms a fundamental building block in all-optical logic operations.