Yinlei Hao

Fano-resonance-based Mach-Zehnder optical switch employing dual-bus coupled ring resonator as two-beam interferometer

A kind of Mach-Zehnder optical switch with a dual-bus coupled ring resonator as a two-beam interferometer is proposed and investigated. The analysis based on the transfer matrix method shows that a sharp asymmetric Fano line shape can be generated in the transmission spectra of such a configuration, which can be used to significantly reduce the phase change required for switching. Meanwhile, it can also be found that complete extinctions can be achieved in both switching states if the structural parameters are carefully chosen and the phase bias is properly set. Through tuning the phase difference between the arms of the Mach-Zehnder interferometer, complete extinction can be easily kept within a large range of the ring-bus coupling ratios in the OFF state. By properly modulating the phase change in the ring waveguide, the shift of the resonant frequency and the asymmetry of the transmission spectra can be controlled to finally enable optical switching with a high extinction ratio, even complete extinction, in the ON state. The switching functionality is verified by the finite-difference time-domain simulation.

Trade-off between optical modulation amplitude and modulation bandwidth of silicon micro-ring modulators.

An analytic model is developed to study the dynamic response of carrier-depletion silicon ring modulators. Its validity is confirmed by a detailed comparison between the modeled and the measured small signal frequency response of a practical device. The model is used to investigate how to maximize the optical modulation amplitude (OMA) and how the OMA could be traded for the bandwidth by tuning the coupling strength and the operation wavelength. Our calculation shows that for a ring modulator with equal RC time constant and photon lifetime, if its operation wavelength shifts from the position of the maximum OMA towards the direction that is away from the resonance, the 3dB modulation bandwidth increases ~2.1 times with a penalty of 3 dB to the OMA.

Low crosstalk 1/spl times/2 thermooptic digital optical switch with integrated S-bend attenuator

We propose and demonstrate a 1times2 thermooptic digital optical switch with variable optical attenuators that are integrated with the S-bend waveguides connecting the output of the Y-switch with a standard fiber array. With a total heating power of 140 mW applied to the switch, we have achieved less than -42-dB optical crosstalk. The wavelength response of the switch is flat across the entire C-band. The average polarization-dependent loss of the switch is about 0.49 dB

Dual Mach-Zehnder Based Integrated X-Type Ratiometric Wavelength Monitor on Glass

We design and fabricate an integrated ratiometric wavelength monitor based on ion-exchange waveguides on glass. The device consists of two unbalanced Mach-Zehnder interferometers acting as edge filters. They are designed to have X-type spectral response. Their output ratio is monotonic to the wavelength in the functional range of the wavelength monitor. The measured resolution is ~ 0.1 nm ranging from 1522 to 1576 nm, which can potentially be improved to 15 pm after packaged. The polarization dependency of the device is also discussed. Our work makes it possible to build a high performance integrated sensing and detecting optical system on one single chip.

Broadband Graphene/Glass Hybrid Waveguide Polarizer

In this letter, a broadband planar-lightwave-circuit-type graphene/glass hybrid waveguide polarizer has been demonstrated. The polarizing effect of the polarizer is based on the difference in the attenuation between the two orthogonally polarized guided modes. The buried depth and the width of the ion-exchange glass waveguide are optimized to 2.6 and 11.5 μm, respectively. The polarization extinction ratio of the polarizer is ~27 dB in the telecommunication band with ~4-mm graphene coating length along the propagation direction. In addition, the polarization extinction ratio can be further increased by decreasing the chemical potential of the graphene film.

Long-wave infrared 1 × 2 MMI based on air-gap beneath silicon rib waveguides

The undercut long-wave infrared (LWIR) waveguide components with air-gap beneath are analyzed and fabricated on the Si-wafer with simple manufacturing process. A 1 × 2 multimode interference (MMI) splitter based on this structure is presented and measured under the 10.6 μm wavelength experimental setup. The uniformity of the MMI fabricated is 0.76 dB. The relationship among the output power, slab thickness and air-gap width is also fully discussed. Furthermore, undercut straight waveguides based on SOI platform are fabricated for propagation loss evaluation. Ways to reduce the loss are discussed either.

Enhancement of nonreciprocal phase shift by using nanoscale air gap

A novel magneto-optical (MO) waveguide with a nanoscale air gap (NAG) is presented. By using an NAG, the nonreciprocal phase shift (NPS) of the MO waveguide can be enhanced. A linear transition model is proposed to theoretically explain the NPS of the MO waveguide with the NAG. Simulation result shows that when the NAG thickness is less than 10 nm, the MO waveguide exhibits an NPS more than four times that of the MO waveguide without the NAG.

Novel dispersive and focusing device configuration based on curved waveguide grating (CWG)

Configuration of a novel compact dispersive and focusing device based on a Curved Waveguide Grating (CWG) is presented, which is essentially an integrated optic wavelength demultiplexer consisting of a curved stripe waveguide with tilted grating, a slab waveguide adjacent to it, and a set of output waveguides locate on focal line of the curved waveguide. Underlying wavelength demultiplexing mechanism of CWG is theoretically illustrated by employing the Fourier optics approach. Analysis shows that device based on CWG possesses fine wavelength resolution, compact configuration, and potentially low cost as well, which make it a promising wavelength demultiplexer, or a network performance monitor, in DWDM optical networks.

Ultracompact Electrooptic Silicon Modulator With Horizontal Photonic Crystal Slotted Slab

In this letter, an ultracompact silicon-based Mach-Zehnder amplitude modulator is proposed. The modulator is realized by infiltrating electrooptic polymers into horizontal photonic crystal slotted slab (HPCSS) waveguides. The optical mode in the phase modulation arms is strongly constrained horizontally by the photonic crystal band gap and vertically by the horizontal slotted slab. The band diagram and group velocity dispersion of the linear defect waveguide in the HPCSS are analyzed. A V ¿ ·L product of 1.4 mV·cm and a bandwidth of over 83 GHz can be obtained.

Charge-density flux model for electric-field-assisted ion exchange in glass

A model based on the charge-density flux (CDF) is proposed for the electric-field-assisted (EFA) ion-exchange, which is suitable for various EFA ion exchanging processes. Theoretical analysis shows that the CDF model is equivalent to the voltage model when the local temperature change around the glass wafer is negligible when a constant voltage is applied to the ion exchanging process. However, our experiments show that the CDF model is more applicable than the voltage model because the constant-voltage scheme shows a positive feedback process and the local temperature rising is unavoidable in the ion exchanging process. Our further experiments also show that the EFA ion exchanging process can be conveniently characterized by the proposed CDF model with the monitored electrical current, no matter the EFA ion exchanging process is with a constant-voltage/current scheme, a mixed scheme, or even a scheme with random voltage change, while additional complicated measures will be required to characterize the EFA ion exchanging process with the traditional voltage model.