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Nonlinear propagation in periodic media has been studied for decades, yielding demonstrations of numerous phenomena including strong temporal compression and slow light generation. Gap solitons, that propagate at frequencies inside the stopband, have been observed in optical fibres but have been elusive in photonic chips. In this manuscript, we investigate nonlinear pulse propagation in a chip-based nonlinear Bragg grating at frequencies inside the stopband and observe clear, unequivocal signatures of gap soliton propagation, including slow light, intensity-dependent transmission, intensity-dependent temporal delay and gap soliton compression. Our experiments which are performed in an on-chip ultra-silicon-rich nitride (USRN) Bragg grating with picosecond time scales, reveal slow light group velocity reduction to 35%–40% of the speed of light in vacuum, change in the temporal delay of 7 ps at low peak powers between 15.7 W–36.6 W, which is accompanied by up to 2.7× temporal compression of input pulses. Theoretical calculations using the nonlinear coupled mode equations confirm the observations of intensity-dependent temporal delay. Of fundamental importance, this demonstration opens up on-chip platforms for novel experimental studies of gap solitons as the basis of all-optical buffers, delay lines and optical storage.

The generation of optical pulse trains from continuous-wave light has attracted growing attention in recent years because it provides a simple way to obtain high repetition rate ultrashort pulses. While pulse generation has been extensively demonstrated in optical fibers, pulse train generation from weak, continuous wave light in photonic chips has posed significant challenges because of the short interaction length and therefore difficulty in acquiring sufficient new frequency content, and/or absence of the appropriate dispersion environment. In this manuscript, we report the pulse train generation of a low continuous-wave signal to 18 ps, by leveraging cross-phase modulation induced by co-propagating pump pulses with a peak power of 3.7 W in an ultra-silicon-rich nitride grating. The pulse train generation dynamics are documented both experimentally and theoretically to arise from cross-phase modulation-induced generation of new spectral content, and dispersive re-phasing. This is a new approach in which picosecond pulse generation may be achieved from low power, continuous-wave light.

We demonstrate a complementary metal–oxide–semiconductor (CMOS)-compatible optical parametric Bragg amplifier on an ultra-silicon-rich nitride chip. The amplifier design incorporates advantageous group index properties in a nonlinear Bragg grating to circumvent phase matching limitations arising from the bulk material and waveguide dispersion. The grating structure further augments the effective nonlinear parameter of 800 W−1/m, considerably lowering the power required for the observation of strong parametric gain. On/off optical parametric gain of 20 dB is achieved using a low peak power of 1.6 W, in good agreement with numerical calculations. This represents a 7 dB improvement in the parametric gain compared to the absence of grating enhancement which is attributed to the Bragg grating induced superior phase matching.

Dispersion impairments are a well-known limitation in data center communications, limiting both the usable data rates and reaches. Several companies today adopt silicon photonics as a core technology in their transceiver products. This presents an opportunity for silicon photonics-based dispersion management technologies to be integrated with the transceiver transmitter or receiver. In this manuscript, we present a ring-resonator based, tunable dispersion compensation device, providing dispersion ranging as wide from + 12.9 × 103ps/nm to −12.3 × 103ps/nm. Thermo-optic tuning from 20°C to 70°C is demonstrated to allow continuous wavelength tuning across 200 GHz. High-speed experiments using 25 Gb/s non-return-to-zero data propagating through 20 km of single mode fiber show that a significant improvement in the eye diagram is achieved after compensation with the ring-resonator device. We demonstrate a significant improvement in the BER from 10−3 to 10−11 for data rates of 25 and 25.78125 Gb/s.

Bragg-soliton dynamics in a 2-stage ultra-silicon-rich-nitride (USRN) chip-based device, consisting of a cladding-apodized modulated Bragg grating (CMBG) stage and a USRN channel waveguide stage, is studied and optimized for enhanced supercontinuum generation. We observe that the enhancement is strongly dependent on the Bragg-soliton effect temporal compression developing in the CMBG stage, which is linked to both device and input pulse parameters. With the optimal parameter combination, a supercontinuum spanning 610 nm at the −30 dB level is experimentally demonstrated in the 2-stage USRN device, representing a 5× enhancement compared to that in a reference waveguide. Good agreement is obtained between the experimentally measured supercontinuum and simulations based on the generalized nonlinear Schrödinger equation and is consistent with design rules based on Bragg soliton compression. This device provides an encouraging path to generate supercontinuum in compact chip-based platforms, which does not need ultrashort, femtosecond scale pulses, greatly relaxing the pulse width and pulse power requirement.

Chemical vapor deposition-based growth techniques allow flexible design of complementary metal-oxide semiconductor (CMOS) compatible materials. Here, we report the deuterated silicon-rich nitride films grown using plasma-enhanced chemical vapor deposition. The linear and nonlinear properties of the films are characterized, and we experimentally confirm that the silicon-rich nitride films grown with SiD4 eliminates Si–H and N–H related absorption. The performance of identical waveguides for films grown with SiH4 and SiD4 are compared demonstrating a 2 dB/cm improvement in line with that observed in literature. Waveguides fabricated on the SRN:D film are further shown to possess a nonlinear parameter of 95 W−1 m−1, with the film exhibiting a linear and nonlinear refractive index of 2.46 and 9.8 $$\times$$ × 10–18 m2W−1 respectively.

We experimentally demonstrate picosecond pulse generation from a low-power continuous-wave signal, generating 18ps pulses, by leveraging cross-phase modulation of pump pulses with a low peak power of 3.7 W in an ultra-silicon-rich nitride Bragg grating.

We demonstrate high-speed transmission of 30Gbaud NRZ and PAM4 data using a silicon nitride microresonator frequency comb. We achieve bit-error-rates below the FEC limit and a low power penalty of 0.1dB compared to B2B characterization.

A 1.2-octave-spanning supercontinuum generation is demonstrated in a 3-mm-long ultra-silicon-rich-nitride waveguide using 17pJ, 500fs pulses. The generated supercontinuum possesses a spectral coherence (|g12|) exceeding 0.94 on average across the measured wavelength range.

We demonstrates the first optical prametric amplification using nonlinear Bragg grating where enhanced phase matching is enabled by utilizing the rapid increase and decrease in effective index near the stopband. An on/off parametric gain of 20dB is achieved in a 3-mm ultra-silicon rich nitride Bragg grating at a low peak power of 1.6W.

A silicon nitride Bragg grating device is demonstrated to compensate for dispersion in a 20km single-mode fiber. Multiple normal dispersion magnitudes can be accessed in a single stopband with blue detuning at low insertion loss.

Ultra-silicon-rich nitride with refractive indices ~ 3 possesses high nonlinear refractive index-100× higher than stoichiometric silicon nitride and presents absence of two-photon absorption, making it attractive to be used in nonlinear integrated optics at telecommunications wavelengths. Despite its excellent nonlinear properties, ultra-silicon-rich nitride photonics devices reported so far still have fairly low quality factors of [Formula: see text], which could be mainly attributed by the material absorption bonds. Here, we report low temperature plasma-deposited dichlorosilane-based ultra-silicon-rich nitride (Si

We demonstrate slot waveguides on ultra-silicon-rich nitride designed for optimal high group index birefringence $( > 1)$ . High speed characterization using 30Gb/s non-return-to-zero and 56Gb/s pulsed amplitude modulation 4 data are performed on fabricated waveguides showing error-free performance.

Three-dimensional monolithically integrated polymer microtoroid resonator-waveguide system and nested-double-spiral waveguides are fabricated and characterized. Transmission of 30Gb/s non-return-to-zero data and 28Gb/s pulse amplitude modulation-4 data is demonstrated.

Infrared (IR)-emitting RE doped materials have been extensively used to fabricate active components of integrated optical devices in various fields, such as fiber amplifiers, telecommunications, optoelectronics, and waveguides. Among various RE elements, trivalent erbium ions (Er 3+) are of great interest since their emissive behavior span the low loss telecommunication window of 1300–1650 nm. In this paper, we report two types of polymeric waveguide amplifiers. 8 cm long, lithographically patterned spiral waveguides provide 8 dB of gain using a 980 nm pump power of 95 mW. Gain is observed from 1530 to 1590 nm. We further report the first demonstration of polymeric waveguide amplifiers fabricated using 3D printing methods based on two-photon lithography, paving the way for rapid prototyping of active 3D printed devices and active photonic devices which may transcend planar limitations.

Topological boundary states are well localized eigenstates at the boundary between two different bulk topologies. As long as bulk topology is preserved, the topological boundary mode will endure. Here, we report topological nonlinear parametric amplification of light in a dimerized coupled waveguide system based on the Su-Schrieffer-Heeger model with a domain wall. The good linear transmission properties of the topological waveguide arising from the strong localization of light to the topological boundary is demonstrated through successful high-speed transmission of 30 Gb/s non-return-to-zero and 56 Gb/s pulse amplitude 4-level data. The strong localization of a co-propagating pump and probe to the boundary waveguide is harnessed for efficient, low power optical parametric amplification and wavelength conversion. A nonlinear tuning mechanism is shown to induce chiral symmetry breaking in the topological waveguide, demonstrating a pathway in which Kerr nonlinearities may be applied to tune the topological boundary mode and control the transition to bulk states.

Optical pulses are fundamentally defined by their temporal and spectral properties. The ability to control pulse properties allows practitioners to efficiently leverage them for advanced metrology, high speed optical communications and attosecond science. Here, we report 11× temporal compression of 5.8 ps pulses to 0.55 ps using a low power of 13.3 W. The result is accompanied by a significant increase in the pulse peak power by 9.4×. These results represent the strongest temporal compression demonstrated to date on a complementary metal–oxide–semiconductor (CMOS) chip. In addition, we report the first demonstration of on-chip spectral compression, 3.0× spectral compression of 480 fs pulses, importantly while preserving the pulse energy. The strong compression achieved at low powers harnesses advanced on-chip device design, and the strong nonlinear properties of backend-CMOS compatible ultra-silicon-rich nitride, which possesses absence of two-photon absorption and 500× larger nonlinear parameter than in stoichiometric silicon nitride waveguides. The demonstrated work introduces an important new paradigm for spectro-temporal compression of optical pulses toward turn-key, on-chip integrated systems for all-optical pulse control.

Bragg solitons are solitary waves which form as a result of the nonlinearity in the medium and the dispersion induced by a Bragg grating. We present recent results covering the dynamics of Bragg solitons. Temporal compression, fission and enhanced, coherent supercontinuum generation and tunable spectral broadening are experimentally demonstrated.

Nonlinear integrated optics leveraging platforms with high nonlinear figure of merit offer energy efficient optical signal processing capabilities. Over the last five years, CMOS-compatible ultra-silico-rich nitride (USRN) has emerged as a promising platform on which to implement various nonlinear optics functions. Bandgap engineered to maximize the Kerr nonlinearity while maintaining two-photon absorption free behavior at telecommunications wavelengths, USRN possesses a nonlinear refractive index that is 100× larger than that in stoichiometric silicon nitride. In this article, we review the recent progress made in USRN-based nonlinear integrated optics devices. The impacts it has made spanning from high gain optical parametric amplification and observations of soliton effects in photonic waveguides and photonic crystal waveguide structures will be discussed. Finally, we assess the future outlook of CMOS-compatible USRN-based nonlinear optics.

Strong temporal compression in an integrated ultra-silicon-rich nitride temporal compressor consisting of separate nonlinear and anomalously dispersive stages is demonstrated. 11× compression of 5.8ps pulses at a low input peak power of 13.3W and 9.4× increase in the pulse peak power is achieved.

Nonlinear optical characterization of Silicon-Rich Nitride waveguides fabricated using deuterated silane are presented. Fourier Transform Infrared Spectroscopy reveals the absence of Si-H and N-H related bonds known to cause optical absorption close to a wavelength of 1550nm.

Integrated photonic nanostructures provide powerful degrees of design freedom for the engineering of light confinement and advanced lightwave manipulation functions. The ability to tailor field profiles in these on-chip devices allows enhanced light-matter interaction, strong modal confinement and the ability to engineer dispersion. Here, we present recent developments in photonic integrated circuits towards the generation of solitons, amplification, and optical waveform manipulation. By harnessing CMOS platforms with a high nonlinear figure of merit, the existence of on-chip Bragg solitons, Bragg soliton fission and solitons in photonic waveguides are experimentally observed. These demonstrations are made possible by 1,000X larger dispersion close to the band edge in on-chip Bragg gratings, an effect that arises from the interaction of forward and backward propagating fields. In addition, efficient parametric processes facilitate wavelength conversion of light and high gain amplification of signals. These efficient nonlinear mechanisms provide a possible pathway in which to realize new approaches to efficiently manipulate optical waveforms.

Parametric wavelength conversion of 30Gbps Non-Return-Zero data using degenerate four wave mixing was performed in ultra-silicon-rich nitride waveguides. A power penalty of 1.2dB was achieved at a bit error rate of 10-4.

Nonlinear CMOS Photonics allows for seamless integration with CMOS electronics and ease of manufacturability. We discus developments in USRN-based nonlinear optics. We demonstrate 8.7 soliton-effect compression in USRN waveguides, on-chip Bragg-soliton compression and fission.

Temperature tuning of spectral broadening induced by a nonlinear grating is experimentally demonstrated. The bandwidth is observed to decrease as temperature increases, corresponding to a red-shift in the high dispersion region of the Bragg grating.

An integrated polymer microtoroid resonator system fabricated using single-step, two-photon polymerization laser lithography is reported. The integrated microtoroid-waveguide system includes an integrated coupling waveguide for ease of optical coupling and has a quality factor of 16,000. We further demonstrate a nested double-spiral waveguide that allows higher spatial density of data, akin to a macroscopic form of space-division multiplexing. Experimental characterization reveals good transmission properties in the double-spiral waveguide device. In addition, the waveguides are demonstrated to support 30 Gb/s nonreturn-to-zero and 28 Gb/s pulse amplitude modulation 4 high-speed data.

Supercontinuum generation (SCG) through soliton fission provides high‐brightness, spectrally‐rich light needed for hyperspectral imaging, broadband spectroscopy, and fluorescence microscopy. The prospect of miniaturization has led to many demonstrations of this phenomenon in integrated platforms. However, due to the moderate dispersion and nonlinearity generally available in channel waveguides, femtosecond pulses have typically been required to date, as the use of picosecond pulses would require unpractically long devices to achieve soliton fission. Here, spectral bandwidth enhancement of the supercontinuum process through Bragg grating induced soliton‐effect compression and soliton fission is demonstrated. This approach uses picosecond pulses on a complementary metal oxide semiconductor (CMOS)‐compatible, millimeter‐scale platform, consisting of a monolithically integrated cladding‐modulated Bragg grating with a channel waveguide. The strong dispersion near the stopband of the grating enables compression and fission of picosecond higher‐order solitons, which enhances the spectral broadening in the channel waveguide. A 4.3 spectral bandwidth enhancement is reported, with respect to a reference waveguide of the same length. The output spectra are further studied both through simulations and experiments and determined to possess high spectral coherence. These results highlight a simple route to significantly augment the bandwidth of nonlinear processes such as SCG while maintaining low power and compact footprint.

Broadband Silicon-On-Insulator (SOI) directional couplers are designed based on a combination of curved and straight coupled waveguide sections. A design methodology based on the transfer matrix method (TMM) is used to determine the required coupler section lengths, radii, and waveguide cross-sections. A 50/50 power splitter with a measured bandwidth of 88 nm is designed and fabricated, with a device footprint of 20 μm × 3 μm. In addition, a balanced Mach-Zehnder interferometer is fabricated showing an extinction ratio of >16 dB over 100 nm of bandwidth.

On-chip waveguide amplifiers offer higher gain in small device sizes and better integration with photonic devices than the commonly available fiber amplifiers. However, on-chip amplifiers have yet to make its way into the mainstream due to the limited availability of materials with ideal light guiding and amplification properties. A low-loss nanostructured on-chip channel polymeric waveguide amplifier was designed, characterized, fabricated and its gain experimentally measured at telecommunication wavelength. The active polymeric waveguide core comprises of NaYF4:Yb,Er,Ce core-shell nanocrystals dispersed within a SU8 polymer, where the nanoparticle interfacial characteristics were tailored using hydrolyzed polyhedral oligomeric silsesquioxane-graft-poly(methyl methacrylate) to improve particle dispersion. Both the enhanced IR emission intensity from our nanocrystals using a tri-dopant scheme and the reduced scattering losses from our excellent particle dispersion at a high solid loading of 6.0 vol% contributed to the outstanding optical performance of our polymeric waveguide. We achieved one of the highest reported gain of 6.6 dB/cm using a relatively low coupled pump power of 80 mW. These polymeric waveguide amplifiers offer greater promise for integrated optical circuits due to their processability and integration advantages which will play a key role in the emerging areas of flexible communication and optoelectronic devices.

An on-chip Coarse wavelength Division Multiplexing (CWDM) has been designed, fabricated and experimentally measured, yielding 9 multiplexed wavelength channels spanning S+C+L band. The average channel crosstalk is −25 dB. All channels cover the CWDM central wavelengths stipulated by ITU standard.

Nonlinear phenomena at the 1550nm wavelength are studied in ultra-silicon-rich nitride devices. Photonic crystals in one are demonstrated to introduce 1000x enhancement in the group velocity dispersion properties and a 40x increase in the nonlinear parameter. The large Kerr nonlinearity and negligible two-photon absorption allow strong nonlinear effects including 42.5dB optical parametric gain and Bragg soliton based temporal compression to be demonstrated.

Nonlinear photonics devices are designed and fabricated on bandgap engineered ultra-silicon-rich nitride (USRN). The USRN films are compositionally engineered to possess a bandgap of 2.1 eV to eliminate two-photon absorption at $1.55 \mu{\mathrm{m}}$ while maintaining a large linear and nonlinear refractive index of 3.1 and 2.8 × 10−13 cm2/ W respectively. We present nanopho-tonic devices periodic in one and two dimensions that introduce an engineered group index profile. The devices are designed to possess a specific dispersion profile that enables slow-light behavior and augmented waveguide nonlinear parameters to be observed. Photonic crystal waveguides with flat band region engineered at the $1.55 \mu{\mathrm{m}}$ region show a ×40 enhancement increase in the nonlinear parameter, providing an effective nonlinear parameter of 1.97 × 104 W−l/m. One-dimensional photonic crystals are designed with effective index modulation effected in the device cladding, and demonstrated to exhibit augmented anomalous dispersion on the band edge while maintaining high transmission. Consequently, the reduced dispersive length combined with the large intrinsic nonlinearity in the material enables time and spectrally resolved characterizations of soliton formation, temporal compression and soliton fission to be experimentally observed. This represents one of the first observations of Bragg solitons on a chip, with the largest soliton-effect pulse compression to date with a compression factor of × 4.

We demonstrate pulse compression using ultra-silicon-rich nitride grating devices. Frequency chirp from a waveguide is temporally synchronized by a dispersive grating to achieve temporal compression by a factor of 4.3. When reversed, spectral compression of 2.3× is achieved.

We demonstrate the optical pulse compression of 2ps laser down to 230fs pulse resulting in 8.7 times compressed using a USRN waveguide. The process is facilitated by high-order soliton formation arising from a large nonlinear parameter and anomalous group velocity dispersion.

Energy bands in AB-stacked bilayer graphene are featured by the co-presence of trigonal warping and a Mexican hat structure around each Dirac point, and electrically modulatable band edges with the modulation valley-dependent (valley-independent) in the case of in-plane (vertical) fields. This theoretical work takes into account the foregoing realistic features and exploits them for valleytronic applications. Specifically, it investigates in detail electrical valley transport in the armchair direction, in AB-stacked bilayer graphene lateral quantum structures with an interface, a single barrier, and double barriers, respectively, and demonstrates that due to the band structure features as well as an involved interplay among them, such structures harbor an interesting potential for valley filtering. An analysis of transmitted current valley polarization is provided. Optimization of the structures for the polarization is explored. The thermal effect on valley filtering is examined. Sizable polarizations of 88% (97%) and 23% (27%) at low and room temperatures, respectively, are shown to be achievable in the case of one-barrier (double-barrier) structures.

It has been fundamentally important and technologically challenging to elucidate the migration behavior of solute atoms in solvents, which can help to understand the growth of nanoparticles. Recently, ascribed to the booming development of start-of-the-art liquid environmental transmission electron microscopes (LETEMs), it has become possible to disclose, in situ, the phase segregation mechanism of elementary units in a solvent at the nanoscale. In addition, bombardment with an electron beam can induce a locally positive potential, with the application of low-conductive Si3N4 and water in LETEMs. Such merits can enable modification of the dynamic distribution and reductive behavior of the solute ions in water solutions. Herein we report the migration and segregation behaviors of Au atoms in a solvent during real time, by exploiting a charging effect in a dilute HAuCl4 water solution under electron irradiation. As a consequence, the growth kinetics of Au nanoparticles can be successfully controlled with an accelerated kinetics model. Through dynamically capturing the segregation behavior of the hydrated atoms, a resultant size-controlling mechanism is clarified with three cycles of nanoparticle growth behavior. A new insight is consequently gained into microscopically manipulating the hydrothermal synthesis of nanomaterials.