arXiv subjects

Yurii A. Vlasov

Publications and source records attributed to Yurii A. Vlasov.

7 recordsLinked to original sources

arXiv2012

Breaking the cavity linewidth limit of resonant optical modulators

Microring optical modulators are being explored extensively for energy-efficient photonic communication networks in future high-performance computing systems and microprocessors, because they can significantly reduce the power consumption of optical transmitters via the resonant circulation of light. However, resonant modulators have traditionally suffered from a trade-off between their power consumption and maximum operation bit rate, which were thought to depend oppositely upon the cavity linewidth. Here, we break this linewidth limitation using a silicon microring. By controlling the rate at which light enters and exits the microring, we demonstrate modulation free of the parasitic cavity linewidth limitations at up to 40 GHz, more than 6x the cavity linewidth. The device operated at 28 Gb/s using single-ended drive signals less than 1.5 V. The results show that high-Q resonant modulators can be designed to be simultaneously low-power and high-speed, features which are mutually incompatible in typical resonant modulators studied to date.

physics.optics↗

arXiv2010

Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides

All-optical signal processing is envisioned as an approach to dramatically decrease power consumption and speed up performance of next-generation optical telecommunications networks. Nonlinear optical effects, such as four-wave mixing (FWM) and parametric gain, have long been explored to realize all-optical functions in glass fibers. An alternative approach is to employ nanoscale engineering of silicon waveguides to enhance the optical nonlinearities by up to five orders of magnitude, enabling integrated chip-scale all-optical signal processing. Previously, strong two-photon absorption (TPA) of the telecom-band pump has been a fundamental and unavoidable obstacle, limiting parametric gain to values on the order of a few dB. Here we demonstrate a silicon nanophotonic optical parametric amplifier exhibiting gain as large as 25.4 dB, by operating the pump in the mid-IR near one-half the band-gap energy (E~0.55eV, lambda~2200nm), at which parasitic TPA-related absorption vanishes. This gain is high enough to compensate all insertion losses, resulting in 13 dB net off-chip amplification. Furthermore, dispersion engineering dramatically increases the gain bandwidth to more than 220 nm, all realized using an ultra-compact 4 mm silicon chip. Beyond its significant relevance to all-optical signal processing, the broadband parametric gain also facilitates the simultaneous generation of multiple on-chip mid-IR sources through cascaded FWM, covering a 500 nm spectral range. Together, these results provide a foundation for the construction of silicon-based room-temperature mid-IR light sources including tunable chip-scale parametric oscillators, optical frequency combs, and supercontinuum generators.

physics.optics↗

arXiv2009

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 (red-shift of 140 +/- 10 pm per atomic layer) without affecting the group-velocity dispersion and third-order dispersion. Additionally, differential tuning of 110 +/- 30 pm per monolayer of the slow-light TE-like and TM-like modes was observed. This passive post-fabrication process has potential applications including the tuning of chip-scale optical interconnects, as well as Raman and parametric amplification.

physics.optics↗

arXiv2005

Coupling into the slow light mode in slab-type photonic crystal waveguides

Coupling of external light signals into a photonic crystal waveguide becomes increasingly inefficient as the group velocity of the waveguiding mode slows down. We have systematically studied the efficiency of coupling in the slow light regime for samples with different truncations of the photonic lattice at the coupling interface. Inverse power law dependence is found to best fit the experimental scaling of the coupling loss on the group index. Coupling efficiency is found to be significantly improved up to group indices of 100 for a truncation of the lattice that favors the appearance of the photonic surface states at the coupling interface in resonance with the slow light mode.

physics.optics↗

arXiv2005

Transmission of Slow Light through Photonic Crystal Waveguide Bends

The spectral dependence of a bending loss of cascaded 60-degree bends in photonic crystal (PhC) waveguides is explored in a slab-type silicon-on-insulator system. Ultra-low bending loss of (0.05+/-0.03)dB/bend is measured at wavelengths corresponding to the nearly dispersionless transmission regime. In contrast, the PhC bend is found to become completely opaque for wavelengths range corresponding to the slow light regime. A general strategy is presented and experimentally verified to optimize the bend design for improved slow light transmission.

physics.optics↗

arXiv2005

Mapping the optical properties of slab-type two-dimensional photonic crystal waveguides

We report on systematic experimental mapping of the transmission properties of two-dimensional silicon-on-insulator photonic crystal waveguides for a broad range of hole radii, slab thicknesses and waveguide lengths for both TE and TM polarizations. Detailed analysis of numerous spectral features allows a direct comparison of experimental data with 3D plane wave and finite-difference time-domain calculations. We find, counter-intuitively, that the bandwidth for low-loss propagation completely vanishes for structural parameters where the photonic band gap is maximized. Our results demonstrate that, in order to maximize the bandwidth of low-loss waveguiding, the hole radius must be significantly reduced. While the photonic band gap considerably narrows, the bandwidth of low-loss propagation in PhC waveguides is increased up to 125nm with losses as low as 8$\pm$2dB/cm.

physics.optics↗

arXiv2004

Observation of surface states in a truncated two-dimensional photonic crystal slab

The effect of lattice termination on the surface states in a two-dimensional truncated photonic crystal slab is experimentally studied in a high index contrast silicon-on-insulator system. A single-mode silicon strip waveguide that is separated from the photonic crystal by a trench of variable width is used to evanescently couple to surface states in the surrounding lattice. It is demonstrated that the dispersion of the surface states depends strongly on the specific termination of the lattice.

physics.optics↗