Lithium Niobate Electro-Optic Modulation Device without an Overlay Layer Based on Bound States in the Continuum.

Electro-optic modulation devices are essential components in the field of integrated optical chips. High-speed, low-loss electro-optic modulation devices represent a key focus for future developments in integrated optical chip technology, and they have seen significant advancements in both commercial and laboratory settings in recent years. Current electro-optic modulation devices typically employ architectures based on thin-film lithium niobate (TFLN), traveling-wave electrodes, and impedance-matching layers, which still suffer from transmission losses and overall design limitations.

Microwave photonic radar system with improved SNR performance utilizing optical resonant amplification and random Fourier coefficient waveforms.

A microwave photonic (MWP) radar system with improved signal-to-noise ratio (SNR) performance is proposed and experimentally demonstrated. By improving the SNR of echoes through properly designed radar waveforms and resonant amplification in the optical domain, the proposed radar system can detect and image weak targets that were previously hidden in noise. Echoes with a common low-level SNR obtain high optical gain and the in-band noise is suppressed during resonant amplification.

Miniature Fourier Transform Spectrometer Based on Thin-Film Lithium Niobate.

A miniature Fourier transform spectrometer is proposed using a thin-film lithium niobate electro-optical modulator instead of the conventional modulator made by titanium diffusion in lithium niobate. The modulator was fabricated by a contact lithography process, and its voltage-length and optical waveguide loss were 2.26 V·cm and 1.

Low-loss, ultracompact n-adjustable waveguide bends for photonic integrated circuits.

Countless waveguides have been designed based on four basic bends: circular bend, sine/cosine bend, Euler bend (developed in 1744) and Bezier bend (developed in 1962). This paper proposes an n-adjustable (NA) bend, which has superior properties compared to other basic bends. Simulations and experiments indicate that the NA bends can show lower losses than other basic bends by adjusting n values.

Investigation of signal-to-noise ratio performance of microwave photonic links enhanced by optical injection locking and channelized spectrum stitching.

A signal-to-noise ratio (SNR) improvement method for microwave photonic (MWP) links enhanced by optical injection locking (OIL) and channelized spectrum stitching (CSS) is investigated and experimentally demonstrated. By exploiting the resonant amplification characteristics of OIL, both optical gain and in-band noise suppression of the input radio frequency signal can be achieved. The injection bandwidth is channelized to further suppress noise during OIL, and the input signal can be well reconstructed by spectrum stitching in the digital domain.

Simultaneous frequency up/down converting interface based on a single hardware incorporating two phase-correlated photonic mixers.

A novel photonic frequency up/down-converting interface (FCI) with the capability of up-converting an intermediate frequency (IF) signal to a radio frequency (RF) signal and simultaneously down-converting a RF signal to a low IF signal is proposed, and a new application scenario, where both up and down frequency conversion stages of a deramp-on-receive linearly frequency modulated (LFM) continuous wave (CW) radar system are replaced by the FCI, is demonstrated. The five-port photonic FCI can be seen as two ultra-wideband phase-correlated photonic RF mixers incorporated in a single hardware, and the working frequency range of the FCI is up to Ka-band. The FCI is tested by an LFM waveform with 1GHz bandwidth in a deramp-on-receive LFM CW imaging radar system.

Scalable distributed microwave photonic MIMO radar based on a bidirectional ring network.

A scalable distributed microwave photonic multiple-input-multiple-output (MIMO) radar is proposed based on a bidirectional ring network. The network is constructed with a fiber ring on which a local node and several remote nodes are distributed. In the local node, radar signals are generated over different optical wavelengths based on external modulation.

Wideband reconfigurable signal generation based on recirculating frequency-shifting using an optoelectronic loop.

A novel photonic-assisted reconfigurable wideband signal generator for linearly frequency-modulated (LFM) signals generation is proposed and experimentally demonstrated. A frequency-shifting recirculating optoelectronic (FSRO) loop is employed to shift and stitch a seed signal repeatedly in the time and the frequency domains through feedback modulation. After experiencing multiple recirculation, a time duration and bandwidth extended LFM signal with a quadratically varying phase of no phase discontinuity is generated.

Microwave photonic de-chirp receiver for breaking the detection range swath limitation.

A novel microwave photonics-based de-chirp radar receiver which breaks the limitation of the detection range swath is proposed and demonstrated. In the proposed receiver, a multi-channel time-division photonics de-chirp processing is implemented to increase the detection range swath. A linear frequency modulated pulse train is sent to multiple reception channels and temporally delayed in the optical domain to form reference signal replicas, enabling time-division photonics-de-chirp processing with echoes reflected from different distance regions so that the total detection range swath is increased and determined by the number of reference replicas.

Redox state and photoreduction control using X-ray spectroelectrochemical techniques - advances in design and fabrication through additive engineering.

The design and performance of an electrochemical cell and solution flow system optimized for the collection of X-ray absorption spectra from solutions of species sensitive to photodamage is described. A combination of 3D CAD and 3D printing techniques facilitates highly optimized design with low unit cost and short production time. Precise control of the solution flow is critical to both minimizing the volume of solution needed and minimizing the photodamage that occurs during data acquisition.

Practical two-dimensional beam steering system using an integrated tunable laser and an optical phased array.

A practical two-dimensional beam steering solid-state system based on the synthesis of one-dimensional wavelength tuning and a one-dimensional optical phased array is demonstrated and investigated. The system incorporates an integrated multiple-channel-interference widely tunable laser, an integrated 32-channel optical phased array, an offline phase error correction unit, and home-made control electronics. The introduction of the integrated tunable laser avoids the traditional bulky light source fed into the optical phased array, making the architecture promising to be miniaturized.

Microwave photonic radar with a fiber-distributed antenna array for three-dimensional imaging.

A microwave photonic (MWP) radar with a fiber-distributed antenna array for three-dimensional (3D) imaging is proposed and demonstrated for the first time. Photonic frequency doubling, wavelength-division multiplexing and radio-over-fiber techniques are employed for radar signal generation, replication, and distribution. Based on the delay-dependent beat frequency division, parallel de-chirp processing is completed in the center office (CO), leading to multi-channel 2D ISAR imaging and further 3D reconstruction.

Novel RF-source-free reconfigurable microwave photonic radar.

A novel reconfigurable microwave photonic (MWP) radar has been proposed and experimentally demonstrated. At a transmitting end, a microwave signal with a large bandwidth and ultra-low phase noise is generated by a Fourier domain mode locking optoelectronic oscillator. At a receiving end, photonics-based de-chirp processing is implemented by phase-modulating light waves in a dual-drive Mach-Zehnder modulator and mixing the modulated light waves at a photodetector.

Channelized photonic-assisted deramp receiver with an extended detection distance along the range direction for LFM-CW radars.

A novel photonic-assisted deramp receiver extends detection distance along range direction of linearly-frequency-modulated continuous wave (LFM-CW) radars is proposed. A dual-polarization quadrature phase shift keying (DP-QPSK) modulator is used to modulate an optical frequency-comb (OFC) to generate orthogonally polarized optical signals. Then the orthogonally polarized optical signals are coherently detected with an optical local oscillator (OLO), which is generated by modulating the other OFC with the RF-reference signal on a null-biased Mach-Zehnder modulator (MZM).

Reconfigurable multi-band microwave photonic radar transmitter with a wide operating frequency range.

A photonics-assisted multi-band radar transmitter operating in a wide frequency range has been proposed and experimentally demonstrated. The multi-band radar transmitter incorporates a tunable optoelectronic oscillator (OEO), a low-frequency RF source and a microwave photonic frequency-converting link. In the frequency-converting link, a single tone with ultra-low phase noise and a low-frequency narrow-band RF signal that are generated respectively by the OEO and the RF source, are mixed, frequency converted and bandwidth multiplied to generate multi-band transmission signals.

Wide-band RF receiver based on dual-OFC-based photonic channelization and spectrum stitching technique.

A novel wide-band RF receiver based on a dual-OFC-based channelization and spectrum stitching technique is proposed and demonstrated experimentally. In the scheme, a dual-OFC-based channelizer is utilized as the front-end to slice the RF signals into multiple channels. In the back-end, through the channel estimation and spectrum stitching, the received signals can be well reconstructed in the digital domain.

Chirped-pulse-based broadband RF channelization implemented by a mode-locked laser and dispersion.

Based on chirped pulses, a wideband radio frequency (RF) channelized receiver that can easily support hundreds of channels is proposed. The mixing chirped pulses and its own delayed copy produces an equivalent RF local oscillation (LO). The LO frequency can be changed by simply setting the delay between the two paths.

Feedforward linearization for RF photonic link with broadband adjustment-free operation.

Linearization of radio frequency (RF) photonic link is critical for advance applications because a nonlinear transfer function of electro-optic modulation limits link dynamic range. Although numerous approaches to suppress third order intermodulation distortion (IMD3) have been demonstrated in previous literatures, many schemes need attendant link optimization when an input RF carrier frequency is tuned over a broad band. In this paper, we propose and demonstrate an adjustment-free linearization approach where high dynamic range could be kept during RF frequency tuning.

Real-time frequency-to-time mapping based on spectrally-discrete chromatic dispersion.

Traditional photonics-assisted real-time Fourier transform (RTFT) usually suffers from limited chromatic dispersion, huge volume, or large time delay and attendant loss. In this paper we propose frequency-to-time mapping (FTM) by spectrally-discrete dispersion to increase frequency sensitivity greatly. The novel media has periodic ON/OFF intensity frequency response while quadratic phase distribution along disconnected channels, which de-chirps matched optical input to repeated Fourier-transform-limited output.

Demonstration of a microwave photonic synthetic aperture radar based on photonic-assisted signal generation and stretch processing.

A microwave photonic synthetic aperture radar (MWP SAR) is developed and experimentally demonstrated. In the transmitter, microwave photonic frequency doubling is used to generate a linearly-frequency-modulated (LFM) radar signal; while in the receiver, photonic stretch processing is employed to receive the reflection signal. The presented MWP SAR operates in Ku band with a bandwidth of 600MHz, and is evaluated through a series of inverse SAR imaging tests both in a microwave anechoic chamber and in a field trial.

Optically tunable Fano resonance in a grating-based Fabry-Perot cavity-coupled microring resonator on a silicon chip.

A grating-based Fabry-Perot (FP) cavity-coupled microring resonator on a silicon chip is reported to demonstrate an all-optically tunable Fano resonance. In the device, an add-drop microring resonator (MRR) is employed, and one of the two bus waveguides is replaced by an FP cavity consisting of two sidewall Bragg gratings. By choosing the parameters of the gratings, the resonant mode of the FP cavity is coupled to one of the resonant modes of the MRR.

Experimental demonstration of a multi-wavelength distributed feedback semiconductor laser array with an equivalent chirped grating profile based on the equivalent chirp technology.

We report, to the best of our knowledge, the first realization of a multi-wavelength distributed feedback (DFB) semiconductor laser array with an equivalent chirped grating profile based on equivalent chirp technology. All the lasers in the laser array have an identical grating period with an equivalent chirped grating structure, which are realized by nonuniform sampling of the gratings. Different wavelengths are achieved by changing the sampling functions.

Transverse load sensing based on a dual-frequency optoelectronic oscillator.

We propose and experimentally demonstrate a fiber-optic sensor implemented based on a dual-frequency optoelectronic oscillator (OEO) for transverse load sensing. In the OEO loop, a phase-shifted fiber Bragg grating (PS-FBG) is employed to which a transverse load is applied to introduce a birefringence to create two orthogonally polarized notches, which leads to the generation of two oscillating frequencies. The beat frequency between the two oscillating frequencies is a function of the load force applied to the PS-FBG.

Dynamic range improvement of a microwave photonic link based on bi-directional use of a polarization modulator in a Sagnac loop.

A novel microwave photonic link (MPL) with an improved spurious-free dynamic range (SFDR) based on a bidirectional use of a polarization modulator (PolM) in a Sagnac loop is proposed and demonstrated. The PolM in the loop functions, in conjunction with a polarization controller and a polarization beam combiner, as a Mach Zehnder modulator (MZM), which only modulates the incident light wave along the clockwise direction, leaving the counter-clockwise light wave unmodulated due to the velocity mismatch. Two clockwise intensity-modulated signals along two paths (Path 1 and Path 2) are generated, with one (Path 2) combined with the non-modulated light wave from the counter-clockwise direction to suppress part of the optical carrier.

A wideband 360° photonic-assisted microwave phase shifter using a polarization modulator and a polarization-maintaining fiber Bragg grating.

A novel approach to implementing a wideband microwave photonic phase shifter by a joint use of a polarization modulator (PolM) and a polarization-maintaining fiber Bragg grating (PM-FBG) is proposed and experimentally demonstrated. A microwave signal to be phase shifted is applied to the PolM. Two phase-modulated signals along the two principal axes of the PolM are generated and sent to the PM-FBG.