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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.

CMOS compatibility and 8-inch manufacturability have been highly desired in MEMS technology. In this article, we demonstrate a MEMS pyroelectric IR detector using CMOS compatible AlN and 8-inch semiconductor wafer technology. This AlN pyroelectric detector detects IR over wavelength ranging from 5 $\mu \text{m}$ to 14 $\mu \text{m}$ . In addition, this detector is designed to have added mechanical stiffness for improved device integrity. The detectors are fabricated with different sensing area dimensions to compare their performance. The best performing detector has an NEP $\sim \,\,8.87\times 10^{\text {-9}}\,\,\text {W/}\sqrt {\text {Hz}} $ and ${D} ^\ast \,\,\sim \,\,6.04\times 10^{{6}}\,\,{\text {cm}\sqrt {\text {Hz}}}/ \text {W}$ . These pyroelectric detectors are designed and built with the consideration to enable ease of monolithic integration with other components to form an integrated gas sensor system. This includes enabling detection of illumination from the front side and using an absorber stack that consists of CMOS dielectric layers. Subsequently, they will form a crucial part of the architectures for miniature photonics-based gas sensors. Their performance is a first step towards 8-inch wafer level CMOS-compatible manufacturable photonics gas sensors. [2020-0157]

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.

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.

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

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.

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.

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.

The dispersive nonlinear refractive index of ultra-silicon-rich nitride, and its two-photon and three-photon absorption coefficients are measured in the wavelength range between 0.8 µm–1.6 µm, covering the O- to L – telecommunications bands. In the two-photon absorption range, the measured nonlinear coefficients are compared to theoretically calculated values with a simple parabolic band structure. Two-photon absorption is observed to exist only at wavelengths lower than 1.2 μm. The criterion for all-optical switching through the material is investigated and it is shown that ultra-silicon-rich nitride is a good material in the three-photon absorption region, which spans the entire O- to L- telecommunications bands.

CO 2 gas sensing responses are measured using our in-house fabricated CMOS-MEMS ScAlN-based pyroelectric detector with 12% Sc doped concentration. Leveraging on mid-IR absorption behavior of CO 2 gas caused by interaction of CO 2 with light at 4.26 µm wavelength, our ScAlN-based pyroelectric detector successfully detect CO 2 gas response ranging from CO 2 concentrations of 5000 ppm down to 200 ppm. Gas channel lengths are varied from 6 cm to 10 cm and their respective CO 2 responses are measured. Finally, with N2 as the reference gas, we calculate the gas response percentage change of CO 2 gas at different gas channel lengths and concentration.

Main complementary metal-oxide-semiconductor (CMOS)-compatible photonics platforms, i.e., silicon and silicon nitride, rely on Kerr nonlinearities for near-instantaneous modulation of optical signals. Kerr nonlinearities emerge due to the third-order susceptibility (χ(3)) and lead to several nonlinear optical processes, including the four-wave mixing (FWM). FWM is the underlying process of many applications, such as parametric amplification, optical sampling, all-optical wavelength conversion, and demultiplexing and therefore has an indispensable role in optical signal processing. The full potential of on-chip nonlinear processes can be efficiently unlocked by tuning the light-matter interactions at a greater extent via manipulating both material and structural properties of integrated photonic devices. We employ photonic crystal waveguides (PhCWgs) to engineer the structural properties of a waveguide by introducing two-dimensional periodicity in the plane of light propagation. In addition to structural engineering, the chosen material platform aims to bypass the limitations of existing CMOS-compatible platforms: the compositionally engineered ultra-silicon-rich nitride (USRN : Si7N3), eliminates two-photon absorption at 1.55 μm and possesses an order of magnitude higher Kerr nonlinearity compared to stoichiometric silicon nitride at telecommunication wavelengths. Here, we present four-wave mixing in a USRN-based, CMOS-compatible, PhCWg leading to on/off optical parametric signal gain reaching 3 dB, and a large instantaneous idler conversion efficiency of −1 dB experimentally. Enhancement of the Kerr nonlinearity in the presence of a sizable and near-constant group index allows us to demonstrate a large on/off gain per unit length of 333 dB/cm on an ultra-compact, 97 μm-long PhCWg.

We present the optical and electrical properties of AlN-based and 12% doped ScAlN-based pyroelectric detectors fabricated on 8-inch wafers respectively. Both AlN and ScAlN materials are deposited at a temperature of ~200oC, making them potential candidates for CMOS compatible MEMS pyroelectric detectors. FTIR spectroscopy is used to measure the absorption of these pyroelectric detectors over the wavelength range of ~2–14 μm and the results show absorption improvement up to ~75% for ScAlN-based pyroelectric detectors compared to that of AlN-based pyroelectric detectors at the wavelength of 4.26 μm where CO2 gas absorption of IR radiation is anticipated. Higher output current (~3-fold increase) is also observed from ScAlN-based pyroelectric detectors. Other than pyroelectric coefficient that contributes to improved performance for ScAlN-based pyroelectric detectors, we believe that absorptivity of the device also plays a major role in the performance of pyroelectric IR detectors. The results obtained from the study of the electrical and optical properties of AlN-based and ScAlN-based CMOS compatible MEMS pyroelectric detectors will bring forth potential applications of these detectors onto multi-functional integrable and monolithic platforms.

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.

Pyroelectric IR detector is fabricated using ScAlN with 12% doped Sc as the pyroelectric sensing material. Dielectric layers that act as absorber are added on top of the ScAlN to help in IR absorption. This ScAlN-based pyroelectric detector is characterized by illumination from a MEMS thermal emitter with a sinusoidal input waveform. D* is measured to be as high as 1.87 x 107 (cm√Hz)/W at a frequency of 13 Hz. The optical absorptance of this device at 4.26 μm CO 2 gas absorption wavelength is around 0.75, measured using FTIR. CO 2 gas sensing measurement detects electrical signal changes of ~50-100 μV.

CMOS-MEMS pyroelectric detectors based on 12%-doped ScAlN are fabricated using 8-inch MEMS wafer technology and characterized. The ScAlN pyroelectric material is deposited at a low temperature of ~200oC. The results show D* as high as 4.3 x 107 (cm√Hz)/W and NEP as low as 1.26 x 10-9 W/√Hz. This is the first demonstration of a functional CMOS-MEMS pyroelectric detector using ScAlN as the pyroelectric sensing material. Compared to AlN that usually presents D* in the range of 105-106, Sc-doped AlN brings on the promise of better performing CMOS-MEMS pyroelectric detectors that could be miniaturized, integrated with CMOS circuits and provide wider applications.

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.

With the emerging trend in miniaturization of complete optical sensor on a silicon platform for gas sensing applications, this paper presents a promising candidate towards monolithic gas sensor with features of 1) a CMOS compatible Aluminum Nitride (AlN)-based pyroelectric infrared detector (PID); 2) customized micropower high-precision CMOS integrated readout circuits. In the PID design, the sensitivity and device integrity are improved with optimized sensing area and modified layer structure. In the readout circuits, to amplify the pico-amperes current from detector, a tunable resistive transimpedance amplifier (TIA) with robust pseudo-resistor in series is proposed to achieve reduced variations against process-voltage-temperature (PVT). A micropower incremental analog-to-digital converter (ADC) is designed to digitize the voltage output from TIA. In addition, to compensate the drifts induced by local temperature change around the detector, an accurate BJT-based temperature sensor is integrated in the circuits as well. Fabricated in an 8-inch wafer, the AlN-based PID with sensing area of 0.29 mm2 achieves the detectivity of 6.04× 106 cm√ Hz/W. The readout circuits are implemented in a 40nm-CMOS process, consuming total power of 24.5 μW under 1.2-V supply. Simulation results show that the TIA gain variation is 11-bit resolution over 1 kHz bandwidth, and the temperature error over -20 °C − 80 °C is ±0.65 °C (3σ) without any calibration.

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.

We demonstrate NDIR CO2 gas sensing using CMOS compatible MEMS ScAlN-based pyroelectric detectors. The ScAlN-based pyroelectric detectors are fabricated using 8-inch wafer level technology with 12 % Sc-doped AlN deposited at a temperature of ∼200 °C. Together with a blackbody thermal emitter, a 10 cm long enclosed gas channel with only inlet and outlet holes connected to tubings, and testing using 2 different reference gases (N2 and synthetic air), measurements show voltage signal drop due to CO2 gas absorption at the 4.26 μm wavelength at CO2 gas concentrations ranging from 5000 ppm down to 25 ppm. The signal change due to the CO2 gas response ranges from ∼2% at 100 ppm CO2 concentration to ∼40 % at 5000 ppm CO2 gas concentration for both CO2 gas measured in N2 and in synthetic air. CO2 gas response times are also measured for CO2 gas in N2 and in synthetic air at concentrations of 5000 ppm, 1000 ppm and 400 ppm. The gas response times measured around 2 s and lower. Introduction of humidity show some minor effect (

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.

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.

Infrared gas sensors have been proven promising for broad applications in Internet of Things and Industrial Internet of Things. However, the lack of miniaturized light sources with good compatibility and tunable spectral features hinders their widespread utilization. Herein, a strategy is proposed to increase the radiated power from microelectromechanical-based thermal emitters by coating with graphene oxide (GO). The radiation can be substantially enhanced, which partially stems from the high emissivity of GO coating demonstrated by spectroscopic methods. Moreover, the sp2 structure within GO may induce plasmons and thus couple with photons to produce blackbody radiation and/or new thermal emission sources. As a proof-of-concept demonstration, the GO-coated emitter is integrated into a multifunctional monitoring platform and evaluated for gas detection. The platform exhibits sensitive and highly selective detection toward CO2 at room temperature with a detection limit of 50 ppm and short response/recovery time, outperforming the state-of-the-art gas sensors. This study demonstrates the emission tailorability of thermal emitters and the feasibility of improving the associated gas sensing property, offering perspectives for designing and fabricating high-end optical sensors with cost-effectiveness and superior performance. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) Accepted version

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.

The appeal of on-chip broadband supercontinuum generation (SCG) comes from its potential to pave the way to full integration of various ultrafast optics applications in frequency metrology, wavelength division multiplexing, and sensing. However, the generation of octave-spanning supercontinuum requires either the use of exceedingly short femtosecond pulses or large footprints. One promising method to achieve broadband supercontinuum is to exploit the high-order soliton fission. Bragg solitons leverage the large anomalous dispersion at the photonic band edge of nonlinear Bragg gratings, therefore they can facilitate high-order soliton fission in much shorter waveguide lengths and significantly lower powers. Soliton dynamics, especially fission, on CMOS-compatible platforms have been limited due to the nonlinear losses such as two-photon absorption and free carrier effects in silicon or low optical nonlinearities in traditional silicon nitride. We use compositionally engineered ultra-silicon-rich nitride (USRN) that possesses a large Kerr nonlinearity in the absence of two-photon absorption. Utilizing ideal nonlinear properties of USRN platform in conjunction with our monolithically integrated cascaded grating-waveguide design, we experimentally demonstrate × 4 spectral broadening enhancement, from 79 nm in the 7 mm long reference waveguide to 311 nm at the cascaded Bragg grating and waveguide device of the same footprint, using input pulses of 1.68 ps FWHM. This result is promising for generating wide supercontinuum, without the need to use sub-picosecond pulses or increasing the device footprint, by exploiting the high-order soliton dynamics availed through the simple photonic chip design consisting of a nonlinear Bragg grating and nonlinear waveguide.

Heterogeneously integrated heterocore microcavity III–V semiconductor lasers on silicon-on-insulator (SOI) are fabricated and demonstrated in this paper. The heterocore microcavity is realized via ultrathin silicon dioxide interlayer bonding of III–V on SOI and dual hard mask technique. The dual hard mask technique utilizes flowable oxide and silicon nitride as etch masks for III–V and SOI etchings, respectively, and hence, a single lithography is required in the fabrication. Compact optical-pumped heterocore microdisk lasers are demonstrated and their lasing performances are characterized.

In this paper, electrically pumped III–V quantum-well lasers bonded on SiO2 with a metal-coated etched-mirror are reported. There are three key features for the device demonstrated: (i) The metal-coated etched-mirror ensures that the lasers can be used as on-chip light source and provides high reflectance, but requires no additional fabrication steps due to our process design, (ii) the bonded III–V on SiO2 enables high-light confinement in the active region due to high index contrast between III–V and SiO2. Moreover, it promises a flexible choice of host substrate, in which the silicon substrate could also be replaced with other materials, and (iii) the active III–V region is sufficiently close to the SiO2 interlayer, allowing the laser mode to overlap with SiO2. This facilitates effective optical coupling with in-plane passive waveguides, which can be fabricated from thin film of amorphous silicon, silicon nitride or other waveguide materials, to form a subsystem on chip through in-plane integration. The laser devices demonstrated have the lowest threshold of 50 mA, a maximum output power of 9 mW, and a differential quantum efficiency of 27.6%.

Plasmonic near-field transducer (NFT) facilitates optical power transfer into a nano-spot in the recording media for heat-assisted magnetic recording. Typically, impedance matching is a condition for maximum power transfer between a given source and load. Even for waveguide-NFT-media stack system, we verify that matching the impedances of waveguide and media-stack at NFT resonance maximizes power transfer. However, it is not a sufficient condition. Since, NFT guides the light into the media-stack as symmetric and asymmetric optical modes, higher conversion of dielectric mode into a mode that exhibits maximum coupling into the media is the second condition for maximizing the power transfer into the media. In this study, operating wavelength range, material refractive indices, and NFT geometrical parameters are considered in the design space for maximizing the efficiency of an exemplary taper-based NFT structure. We first estimate the maximum efficiency and compare with the benchmark efficiency of “ideal” version of the considered NFT to confirm that the obtained efficiency is maximum. At maximum efficiency point, we show that the impedance matching between waveguide and high-index media stack is enhanced and mode-conversion efficiency into asymmetric plasmon mode is also enhanced because of high-index contrast feeding waveguide and suitable operating wavelength range.

Light-delivery system for heat-assisted magnetic recording consists of laser, waveguide, and plasmonic near-field transducer (NFT). The overall efficiency of light-delivery system is determined by the efficiency of optical power transfer from waveguide to media via the plasmonic NFT and coupling of light from laser to waveguide. In this paper, we present an overall efficiency optimization of the light-delivery system, including the waveguide-NFT-media coupling efficiency by improving the waveguide mode–plasmon mode conversion and waveguide-media-stack impedance matching and laser-to-waveguide coupling efficiency using multi-layer graded refractive-index (GRIN) cladding layer. We show that a high refractive-index waveguide improves waveguide mode-to-asymmetric plasmon mode conversion and also improves characteristic impedance matching with the media stack resulting in a maximal optical power transfer efficiency of $\sim 11.5$ % between the waveguide and the media via a taper-based NFT. The multi-layer GRIN cladding structure acts as a collimating lens with a high numerical aperture, which can achieve laser-to-waveguide coupling efficiency of $\sim 90$ % in our numerical example. Therefore, the overall optimization shows that the efficiency of light-delivery system can reach $\sim 9$ %–10%.

In this paper, we fabricate and demonstrate a functional complementary metal-oxide-semiconductor (CMOS) compatible pyroelectric uncooled thermal detector using 12% doped Scandium Aluminum Nitride (ScAlN) as the sensing layer. The ScAlN pyroelectric material is deposited at a temperature of ∼200 °C over an 8-in. wafer area. This detector has shown, in general, improved performance compared to AlN, with specific detectivity as high as ∼ 6.08 × 10 7 cm Hz / W and noise equivalent power as low as ∼ 8.85 × 10 − 10 W / Hz. The results show the specific detectivity of ScAlN-based pyroelectric detectors in the range of 107 cm Hz / W, which is an improvement compared to AlN-based pyroelectric detectors which report specific detectivity typically in the range of 105–106 cm Hz / W. This promising result opens up the opportunities for a CMOS compatible, 8-in. wafer-level manufacturable lead-free pyroelectric detector toward low cost and high throughput, allowing microelectromechanical systems (MEMS) and CMOS integration for increased applications in CMOS–MEMS integrated devices utilizing pyroelectric detectors.

Emerging compositionally engineered complementary metal-oxide-semiconductor (CMOS)-compatible platforms have been employed for high efficiencies in various on-chip applications, including optical parametric amplification and wavelength conversion. Combining the novel nonlinear optics platforms such as ultra-silicon-rich nitride (USRN: Si7N3) with periodic waveguide structures can lead to further enhancement of material nonlinearities via the slow light effect and enable ultra-compact devices. Four-wave mixing in a USRN-based, CMOS-compatible, photonic crystal waveguide (PhCWg) leading to on/off optical parametric signal gain reaching 3 dB, and a large instantaneous idler conversion efficiency of −1 dB is explored experimentally. Enhancement of Kerr nonlinearity in the presence of a sizable and near-constant group index allows the findings on an ultra-compact, 97 μm-long PhCWg, equivalent to a large on/off gain per unit length of 333 dB/cm.