Passive wavelength selective polarization rotator in a hybrid waveguide platform.

Polarization rotation and wavelength filtering are key functionalities used to build complex photonic integrated circuits. Both these functionalities have been demonstrated in various material and device platforms. We propose, for the first time, a fully passive wavelength selective polarization rotation in silicon nitride/amorphous silicon hybrid waveguide.

Linear and nonlinear characterization of a broadband integrated Si-rich silicon nitride racetrack ring resonator for on-chip applications.

We demonstrate the linear and nonlinear characterization of a plasma-enhanced chemical vapor deposited silicon-rich silicon nitride (SRSN) racetrack ring resonator for on-chip applications within the telecommunication wavelength range. The SRSN waveguide parameters are optimized by employing the refractive index profile measured by ellipsometry to achieve flat dispersion in the telecom band. Furthermore, we measure the thermo-optic coefficient of the micro-resonator by analyzing the temperature-dependent transmission spectra and assess it to be 3.

Polarization independent grating in a GaN-on-sapphire photonic integrated circuit.

In this work, we report the realization of a polarization-insensitive grating coupler, single-mode waveguide, and ring resonator in the GaN-on-sapphire platform. We provide a detailed demonstration of the material characterization, device simulation, and experimental results. We achieve a grating coupler efficiency of -5.

Thin-film wafer-scale mid-IR Fabry Perot cavity gas sensor.

We demonstrate a miniaturized wafer-scale optical gas sensor that combines the gas cell, an optical filter, and integrated flow channels. We present the design, fabrication and characterization of an integrated cavity-enhanced sensor. Using the module, we demonstrate absorption sensing of ethylene down to 100 ppm level.

Nonlinear spectral broadening of a dual-carrier electro-optic frequency comb in a graphene oxide cladded silicon-rich nitride hybrid waveguide.

We demonstrate a detailed theoretical analysis describing the generation of an electro-optic comb (EOC) in the near-IR range through discrete phase and amplitude modulation driven by radio frequency (RF) signal generators. Furthermore, the generated EOC spectra suffer nonlinear spectral broadening while propagating through a hybrid Si-rich nitride (SRN) waveguide structure integrated with two-dimensional (2D) layered graphene oxide (GO) films. We perform a detailed analysis to investigate the influence of GO layers, pump wavelength detuning, and other waveguide parameters on the evolution of comb spectra propagating through the hybrid waveguide structure.

Guided mode resonance aided polarization insensitive in-plane spectral filters for an on-chip spectrometer.

We demonstrate an on-chip in-plane polarization independent multi-spectral color filter in the visible to near-infrared wavelength band. We experimentally show a four-channel transmission and in-plane spectral filter characteristics spanning a 400-nm spectral range. Engineered 2D guided mode resonance structures in a silicon nitride-on-sapphire substrate are used to realize the filters.

Polar Semiconducting Scandium Nitride as an Infrared Plasmon and Phonon-Polaritonic Material.

The interaction of light with collective charge oscillations, called plasmon-polariton, and with polar lattice vibrations, called phonon-polariton, are essential for confining light at deep subwavelength dimensions and achieving strong resonances. Traditionally, doped-semiconductors and conducting metal oxides (CMO) are used to achieve plasmon-polaritons in the near-to-mid infrared (IR), while polar dielectrics are utilized for realizing phonon-polaritons in the long-wavelength IR (LWIR) spectral regions. However, demonstrating low-loss plasmon- and phonon-polaritons in one host material will make it attractive for practical applications.

Comprehensive grating enabled silicon nitride fiber-chip couplers in the SNIR wavelength band.

We present silicon nitride grating enabled fiber-chip coupling in the sub-near-infrared band. We present a comprehensive design and simulation and experimental demonstration of uniform and apodized grating couplers, with and without bottom reflectors. The mode engineering yields a best efficiency of -1.

On-chip silicon nano-slab photodetector integrated wavelength division de-multiplexer in the 850 nm band.

We present an on-chip photodetector integrated wavelength filter on a SiN-on-silicon-on-insulator (SOI) platform in the 850 nm wavelength window. The wavelength filter is designed using an echelle grating with a distributed Bragg reflector as the grating reflectors. We present the design and experimental realization of a six-channel wavelength filter with a channel spacing of 10 nm.

High-efficiency vertical fibre-to-polymer waveguide coupling scheme for scalable polymer photonic circuits.

Polymer photonic circuits offer a versatile platform for various applications, including communication, sensing and optical signal processing. Though polymers offer broadband, linear and nonlinear optical properties, the coupling between an optical fibre and a polymer waveguide has been a challenge. In this work, we propose and demonstrate a wafer-scale vertical coupling scheme for polymer waveguides.

On-chip silicon photonics based grating assisted vibration sensor.

We present a compact, highly sensitive and scalable on-chip photonic vibration measurement scheme for vibration sensing. The scheme uses a silicon photonic diffraction-grating based sensor integrated underneath a silicon cantilever. We demonstrate a static and dynamic measurement sensitivity (ΔT/Δgap) of 0.

Microwave power induced resonance shifting of silicon ring modulators for continuously tunable, bandwidth scaled frequency combs.

We demonstrate a technique to continuously tune center frequency and repetition rate of optical frequency combs generated in silicon microring modulators and bandwidth scale them. We utilize a drive frequency dependent, microwave power induced shifting of the microring modulator resonance. In this work, we demonstrate center frequency tunability of frequency combs generated in silicon microring modulators over a wide range (∼8nm) with fixed number of lines.

Enhanced nonlinear spectral broadening and sub-picosecond pulse generation by adaptive spectral phase optimization of electro-optic frequency combs.

We utilize adaptive optimization to enhance the spectral broadening of an amplified electro-optic frequency comb with a 25 GHz repetition rate in a highly nonlinear fiber and subsequently generate sub-picosecond pulses. The spectral phase of the comb is adaptively optimized by a Fourier pulse shaper in a closed control loop with the HNLF output spectrum as the process variable to be optimized. Enhanced spectral broadening also increases the stimulated Brillouin scattering threshold allowing increased power scaling and thereby boosting the bandwidth by a factor of more than 13 times over the initial comb.

Broadly tunable and low power penalty radio frequency phase shifter using a coupled silicon microcavity.

We present a continuously tunable silicon photonics assisted radio frequency (RF) phase shifter using a coupled microring resonator. Using the coupled cavity, we demonstrate a sub-1 dB power penalty for a RF bandwidth of 34.5 GHz (9-43.

Optical frequency comb based on nonlinear spectral broadening of a phase modulated comb source driven by dual offset locked carriers.

We demonstrate a versatile technique to generate a broadband optical frequency comb source in the C-band. This is accomplished by nonlinear spectral broadening of a phase modulated comb source driven by dual frequency offset locked carriers. The locking is achieved by setting up a heterodyne optical frequency locked loop to lock two phase modulated electro-optic 25 GHz frequency combs sourced from individual seed carriers offset by 100 GHz, to within 6.

Enhanced all-optical cavity-tuning using graphene.

All-optical tuning of the resonance of an optical cavity is used to realise optical signal-processing including modulation, switching, and signal-routing. The tuning of optical resonance is dictated by the two primary effects induced by optical absorption: charge-carrier-generation and heat-generation. Since these two effects shift the resonance in opposite directions in a pure silicon-on-insulator (SOI) micro-ring resonator as well as in a graphene-on-SOI system, the efficiency and the dynamic range of all-optical resonance-tuning is limited.

High efficiency DBR assisted grating chirp generators for silicon nitride fiber-chip coupling.

Silicon Nitride (SiN) is emerging as a promising material for a variety of integrated photonic applications. Given its low index contrast however, a key challenge remains to design efficient couplers for the numerous platforms in SiN photonics portfolio. Using a combination of bottom reflector and a chirp generating algorithm, we propose and demonstrate high efficiency, grating couplers on two distinct SiN platforms.

Alignment-tolerant broadband compact taper for low-loss coupling to a silicon-on-insulator photonic wire waveguide.

We experimentally demonstrate a broadband, fabrication-tolerant compact silicon waveguide taper (34.2 μm) in a silicon-on-insulator wire waveguide. The taper works on multimode interference along the length of the taper.

Broadly tunable wideband optical single sideband generation using self-coupled silicon resonator.

We propose and demonstrate a tunable broadband optical single sideband generation using self-coupled silicon micro-ring resonator. We exploit self-coupling in a ring cavity to generate tunable resonance splitting. Using the proposed device, single sideband with carrier signal is generated from a double sideband signal.

High-speed waveguide integrated silicon photodetector on a SiN-SOI platform for short reach datacom.

We present a waveguide integrated high-speed Si photodetector integrated with a silicon nitride (SiN) waveguide on an silicon-on-insulator (SOI) platform for short reach data communication in a 850 nm wavelength band. We demonstrate a waveguide couple Si pin photodetector responsivity of 0.44 A/W at 25 V bias.

Carbon-nanotube-on-waveguide thermo-optic tuners.

We demonstrate on-waveguide thermo-optic tuners based on solution-processed metallic carbon nanotubes (CNTs) on silicon-on-insulator (SOI) and silicon nitride (SiN) microring resonators operating around 1550 nm. On SOI microring resonators using planarized wire waveguides, a thermo-optic power efficiency of 29 mW/FSR and a thermal transient of 1.3 μs are achieved.

Compact broadband low-loss taper for coupling to a silicon nitride photonic wire.

We demonstrate an ultra-compact waveguide taper on a silicon nitride platform. The proposed taper provides a coupling efficiency of 95% at a length of 19.5 μm in comparison to the standard linear taper of length 50 μm, which connects a 10 μm wide waveguide to a 1 μm wide photonic wire.

Real-time compensation of errors in refractive index shift measurements of microring sensors using thermo-optic coefficients.

We report a method for compensation of errors caused by temperature fluctuations in refractive index measurements using Silicon photonic microring sensors. The method involves determination of resonance wavelength shifts caused by thermal fluctuations using real-time measurement of on-chip temperature variations and thermo-optic coefficient (TOC) of analyte liquids. Resistive metal lines patterned around Silicon microrings are used to track temperature variations and TOC of analyte is calculated by measuring wavelength shifts caused by controlled increments in device temperature.

Generation of tunable, high repetition rate optical frequency combs using on-chip silicon modulators.

We experimentally demonstrate tunable, highly-stable frequency combs with high repetition-rates using a single, charge injection based silicon PN modulator. In this work, we demonstrate combs in the C-band with over eight lines in a 20-dB bandwidth. We demonstrate continuous tuning of the center frequency in the C-band and tuning of the repetition-rate from 7.

On-chip optical transduction scheme for graphene nano-electro-mechanical systems in silicon-photonic platform.

We present a scheme for on-chip optical transduction of strain and displacement of graphene-based nano-electro-mechanical systems (NEMS). A detailed numerical study on the feasibility of three silicon-photonic integrated circuit configurations is presented: the Mach-Zehnder interferometer (MZI), the micro-ring resonator, and the ring-loaded MZI. An index sensing based technique using an MZI loaded with a ring resonator with a moderate Q-factor of 2400 can yield a sensitivity of 28  fm/Hz and 6.