Saeed Farooq Khan

Learn More
A platform for the realization of tightly-confined lithium niobate photonic devices and circuits on silicon substrates is reported based on wafer bonding and selective oxidation of refractory metals. The heterogeneous photonic platform is employed to demonstrate high-performance lithium niobate microring optical resonators and Mach-Zehnder optical(More)
Electronically tunable optical true-time delay lines are proposed. The devices utilize the combination of apodised gratings and the free-carrier plasma effect to tune the enhanced delay of silicon waveguides at a fixed wavelength. Three variations of the proposed scheme are studied and compared. The compact and integrable devices can achieve tuning ranges(More)
Silicon-on-nitride ridge waveguides are demonstrated and characterized at mid-and near-infrared optical wavelengths. Silicon-on-nitride thin films were achieved by bonding a silicon handling die to a silicon-on-insulator die coated with a low-stress silicon nitride layer. Subsequent removal of the silicon-on-insulator substrate results in a thin film of(More)
High-speed, tunable integrated silicon photonic delay lines are demonstrated by cascading complementary apodized silicon grating waveguides. The cascaded grating waveguides, with inward and outward super-Gaussian apodization profiles, compensate each other's dispersion and allow high-speed operation. Characterization of the compact delay lines shows that(More)
Submicron tantalum pentoxide ridge and channel optical waveguides and microring resonators are demonstrated on silicon substrates by selective oxidation of the refractory metal, tantalum. The novel method eliminates the surface roughness problem normally introduced during dry etching of waveguide sidewalls and also simplifies fabrication of directional(More)
A novel class of high-speed and tunable integrated photonic delay lines that compromise between loss and size is proposed. The devices consist of two cascaded apodized grating waveguides and with complementary (positively and negatively modulated) refractive index profiles for dispersion compensation. It is shown that the compact tunable delay lines are(More)
Like email and conventional telephony, Voice over IP telephony is subject to spam. This paper discusses the problem of spam over IP telephony and investigates techniques which use the Session Initiation Protocol (SIP) to reject likely nuisance callers. Existing techniques include content filtering, black lists, white lists, gray lists, call rate monitoring,(More)
High-speed and tunable integrated optical delay lines are demonstrated based on silicon grating waveguides apodized by the super-Gaussian function. The submicron channel waveguides with inward-apodized gratings are fabricated by deep-ultraviolet optical lithography. Characterization of the compact delay lines shows that they offer true-time delays as long(More)
  • 1