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Abstract Dissipative Kerr soliton microcombs in microresonators have enabled fundamental advances in chip-scale precision metrology, communication, spectroscopy, and parallel signal processing. Here we demonstrate polarization-diverse soliton transitions and deterministic switching dynamics of a self-stabilized microcomb in a strongly-coupled dispersion-managed microresonator driven with a single pump laser. The switching dynamics are induced by the differential thermorefractivity between coupled transverse-magnetic and transverse-electric supermodes during the forward-backward pump detunings. The achieved large soliton existence range and deterministic transitions benefit from the switching dynamics, leading to the cross-polarized soliton microcomb formation when driven in the transverse-magnetic supermode of the single resonator. Secondly, we demonstrate two distinct polarization-diverse soliton formation routes – arising from chaotic or periodically-modulated waveforms via pump power selection. Thirdly, to observe the cross-polarized supermode transition dynamics, we develop a parametric temporal magnifier with picosecond resolution, MHz frame rate and sub-ns temporal windows. We construct picosecond temporal transition portraits in 100-ns recording length of the strongly-coupled solitons, mapping the transitions from multiple soliton molecular states to singlet solitons. This study underpins polarization-diverse soliton microcombs for chip-scale ultrashort pulse generation, supporting applications in frequency and precision metrology, communications, spectroscopy and information processing.

High-spectral-purity frequency-agile room-temperature THz sources are foundational elements for imaging, sensing, metrology, and communications. Here a parametric oscillator-photomixer chip with coherent 2.8-octave tunable THz radiation is achieved.

Optical frequency combs can provide phase-coherent links between optical frequencies and microwaves, allowing for precise optical frequency generation; however current technologies require external optical references or multiple power-intensive peripherals that make them less suitable for on-chip applications. Here, the authors present phase stabilization of a frequency microcomb without nonlinear processes nor external optical reference signals.

Dissipative Kerr solitons (DKSs) in microresonators have boosted the development of the chip-scale ultrastable microcomb sources, and thrived in both fundamental physics and a wide range of applications. Among various DKS states, single DKS, double DKS, and a perfect soliton crystal could be identified simply based on the optical spectrum. Especially, the double DKS state, due to its two-pulse-interference nature, has recently found its own application in microwave photonics, such as reconfigurable rf filters. However, the traditional method to generate double DKS usually yields stochastically relative positions of the DKS in the cavity, which limits the versatility of the application. Here a method to deterministically generate double DKSs with fixed relative positions assisted by the dual-pump driven scheme in a 97-GHz Si_{3}N_{4} microresonator is demonstrated. Via the dual-pump scheme, not only has the single soliton been repeatably generated, double DKS with deterministic relative positions has also been realized through backward tuning. The effects of pump wavelength tuning and pump power on the relative positions are investigated. A direct bridge between the relative positions and the avoided mode crossing induced modulated cw background is established. This work not only provides insight to DKS dynamics in a dual-pump scheme, but also improves the versatility of double-DKS based applications in microwave photonics.

A compact wideband optical switch assisted by graphene nanosheet heater is demonstrated by shifting the bandedge of the photonic crystal waveguides (PhCWG) through current-induced heating. The high heating efficiency of graphene and the high light-matter interactions in slow-light PhCWG are combined to enhance the heating efficiency and extinction ratio. The extinction ratio is increased from 15 dB to 22 dB and the tuning bandwidth is up to 20 nm with only 28 K temperature change. Our measurements match well with simulation results, suggesting an effective way for CMOS compatible chip-scale integrated graphene microheater switch.

Abstract Wearable photonics offer a promising platform to complement the thriving complex wearable electronics system by providing high‐speed data transmission channels and robust optical sensing paths. Regarding the realization of photonic computation and tunable (de)multiplexing functions based on system‐level integration of abundant photonic modulators, it is challenging to reduce the overwhelming power consumption in traditional current‐based silicon photonic modulators. This issue is addressed by integrating voltage‐based aluminum nitride (AlN) modulator and textile triboelectric nanogenerator (T‐TENG) on a wearable platform to form a nano‐energy‐nano‐system (NENS). The T‐TENG transduces the mechanical stimulations into electrical signals based on the coupling of triboelectrification and electrostatic induction. The self‐generated high‐voltage from the T‐TENG is applied to the AlN modulator and boosts its modulation efficiency regardless of AlN's moderate Pockels effect. Complementarily, the AlN modulator's capacitive nature enables the open‐circuit operation mode of T‐TENG, providing the integrated NENS with continuous force sensing capability which is notably uninfluenced by operation speeds. Furthermore, a physical model is proposed to describe the coupled AlN modulator/T‐TENG system. With the enhanced photonic modulation and the open‐circuit operation mode enabled by synergies between the AlN modulator and the T‐TENG, optical Morse code transmission and continuous human motion monitoring are demonstrated for practical wearable applications.

We experimentally demonstrate a spectrometer, which consists of an arrayed waveguide grating (AWG), tunable microring resonator (MRR) array, and waveguide-coupled Ge-on-Si photodetector, all integrated onto a single chip. The spectrometer achieves high resolution (0.1 ± 0.029 nm) and large bandwidth (25.4 nm) in 9 channels with a small footprint of 3 × 3 mm2. It has high potential to enable a high-performance spectrometer for applications such as environmental monitoring, spectroscopy, biological and chemical sensing, etc.

Abstract For the sensitive high-resolution force- and field-sensing applications, the large-mass microelectromechanical system (MEMS) and optomechanical cavity have been proposed to realize the sub-aN/Hz1/2 resolution levels. In view of the optomechanical cavity-based force- and field-sensors, the optomechanical coupling is the key parameter for achieving high sensitivity and resolution. Here we demonstrate a chip-scale optomechanical cavity with large mass which operates at ≈77.7 kHz fundamental mode and intrinsically exhibiting large optomechanical coupling of 44 GHz/nm or more, for both optical resonance modes. The mechanical stiffening range of ≈58 kHz and a more than 100th-order harmonics are obtained, with which the free-running frequency instability is lower than 10−6 at 100 ms integration time. Such results can be applied to further improve the sensing performance of the optomechanical inspired chip-scale sensors.

Chaotic behaviour of optomechanical systems has only recently been investigated and observed. Here, Wuet al. study the chaos dynamics in a silicon platform where coupled electron-hole plasma dynamics is possible, providing a route towards chip-scale mesoscopic nonlinear dynamics.

In this paper, we report a compact wavelength-flattened directional coupler (WFDC) based chemical sensor featuring an incorporated subwavelength grating (SWG) structure for the mid-infrared (MIR). By incorporating a SWG structure into directional coupler (DC), the dispersion in DC can be engineered to allow broadband operation which is advantageous to extract spectroscopic information for MIR sensing analysis. Meanwhile, the Bragg reflection introduced by the SWG structure produces a sharp trough at the Bragg wavelength. This sharp trough is sensitive to the surrounding refractive index (RI) change caused by the existence of analytes. Therefore, high sensitivity can be achieved in a small footprint. Around fivefold enhancement in the operation bandwidth compared to conventional DC is achieved for 100% coupling efficiency in a 40 µm long WFDC experimentally. Detection of dichloromethane (CH2Cl2) in ethanol (C2H5OH) is investigated in a SWG-based WFDC sensor 136.8 µm long. Sensing performance is studied by 3D finite-difference time domain (FDTD) simulation while sensitivity is derived by computation. Both RI sensing and absorption sensing are examined. RI sensing reveals a sensitivity of −0.47% self-normalized transmitted power change per percentage of CH2Cl2 concentration while 0.12% change in the normalized total integrated output power is realized in the absorption sensing. As the first demonstration of the DC based sensor in the MIR, our device has the potential for tertiary mixture sensing by utilizing both changes in the real and imaginary part of RI. It can also be used as a broadband building block for MIR application such as spectroscopic sensing system.

In nonlinear microresonators driven by continuous-wave (cw) lasers, Turing patterns have been studied in the formalism of the Lugiato-Lefever equation with emphasis on their high coherence and exceptional robustness against perturbations. Destabilization of Turing patterns and the transition to spatiotemporal chaos, however, limit the available energy carried in the Turing rolls and prevent further harvest of their high coherence and robustness to noise. Here, we report a novel scheme to circumvent such destabilization, by incorporating the effect of local mode hybridizations, and we attain globally stable Turing pattern formation in chip-scale nonlinear oscillators with significantly enlarged parameter space, achieving a record-high power-conversion efficiency of 45% and an elevated peak-to-valley contrast of 100. The stationary Turing pattern is discretely tunable across 430 GHz on a THz carrier, with a fractional frequency sideband nonuniformity measured at 7.3×10^{−14}. We demonstrate the simultaneous microwave and optical coherence of the Turing rolls at different evolution stages through ultrafast optical correlation techniques. The free-running Turing-roll coherence, 9 kHz in 200 ms and 160 kHz in 20 minutes, is transferred onto a plasmonic photomixer for one of the highest-power THz coherent generations at room temperature, with 1.1% optical-to-THz power conversion. Its long-term stability can be further improved by more than 2 orders of magnitude, reaching an Allan deviation of 6×10^{−10} at 100 s, with a simple computer-aided slow feedback control. The demonstrated on-chip coherent high-power Turing-THz system is promising to find applications in astrophysics, medical imaging, and wireless communications.

An effective 2-D self-consistent solution of Schrodinger-Poisson (SP) within the effective mass approximation was used to gain insight into the capacitance-voltage [C([V.sub.g])] features of cylindrical gate-all-around n- and p-channel Si nanowire MOS structures. The studies related to the density-of-states features of the Si channel from the capacitance-voltage characteristics at room temperature measurements are also presented.

Several simulations are conducted for the calibration of the various charge-based capacitance measurement techniques that are used for the nanoscale devices. The various effects of charge injection and numerical error in the technique are also discussed.

n-Type and p-type dipoles are incorporated in TaN gate stacks by forming terbium (Tb)- and aluminum (Al)-based interlayers (ILs), respectively, and a detailed study is conducted on the effect of combining n-type and p-type dipoles into the same TaN gate stack for metal gate work function tunability. The concept of manipulating interface dipoles of opposing polarity for metal gate work function tunability has opened new ways for achieving multiple work functions by using a single metal gate and a simple integration scheme.