Guanghui Ren

• PhD
• Senior research fellow at RMIT University

The surge in data driven by socio‐economic development has presented enormous challenges to data centers, catalyzing the swift advancement of optical interconnect technology. Advanced optical multiplexers and modulators are increasingly applied to optical interconnects in data centers, offering robust solutions to mitigate the impact of this data d...

Mode-division multiplexing is a common technology in photonic integrated circuits, which can combine various optical mode signals into one single channel such as a multimode waveguide to improve the communication system’s capacity. Optical mode switch plays a critical role in mode-division multiplexing, which can switch the optical signal into diff...

Van der Waals (vdWs) heterojunction photodetectors based on 2D transition metal dichalcogenides are widely utilized in optoelectronic detection, where the band structure of the heterojunction plays a crucial role in determining the performance of the photodetector. In this study, a WSe2/WS2 vdWs heterostructure photodetector with a type‐II band ali...

Lithium niobate on insulator (LNOI) attracts extensive attention from academic and industrial communities due to LN’s excellent electro-optic (EO) properties, which also brings bright prospects for achieving high-speed and large-capacity photonic integrated circuits (PICs) including active and passive components such as modulator, filter, and multi...

We report ring resonators on a silicon germanium on silicon platform operating in the mid-infrared wavelength range around 3.5 - 4.6 {\mu}m with quality factors reaching up to one million. Advances in fabrication technology enable us to demonstrate such high Q-factors, which put silicon germanium at the forefront of mid-infrared integrated photonic...

Photonic time-delay reservoir computing schemes usually employ an input mask as a means of performance enhancement. However, input masking usually necessitates a domain conversion, requiring a signal to be treated before sending it to the reservoir. More recent implementations have explored further ways of performance enhancement, whether through o...

Research on microwave signal measurement techniques is risen, driven by the expanding urgent demands of wireless communication, global positioning systems, remote sensing and 6G networks. In stark contrast with traditional electronic-based realization, the implementations of microwave signal measurement systems based on integrated compact photonic...

Feedback control plays a crucial role in improving system accuracy and stability for a variety of scientific and engineering applications. Here, we theoretically and experimentally investigate the implementation of feedback control in microwave photonic (MWP) transversal filter systems based on optical microcomb sources, which offer advantages in a...

Microwave transversal filters, which are implemented based on the transversal filter structure in digital signal processing, offer a high reconfigurability for achieving a variety of signal processing functions without changing hardware. When implemented using microwave photonic (MWP) technologies, also known as MWP transversal filters, they provid...

Fourier domain mode-locked optoelectronic oscillator (FDML OEO) is a crucial component for the upcoming sixth-generation (6G) communication era, as it can break the limitation of mode building time in the conventional OEO and generate high-quality frequency-tunable microwave signals or waveform such as linearly chirped microwave waveform (LCMW) for...

Over the past two decades, there has been a surge of interest in photonic integrated circuits (PICs) to enable low‐cost industrial mass manufacture of miniaturized optical systems while simultaneously improving performance and energy efficiency following the trajectory of electronics and large‐scale integration. An essential characteristic of any P...

The rise of two-dimensional (2D) material provides a confined geometry and yields methods for guiding electrons at nanoscale. The 2D material-enabled electronic devices, which can interact and transduce the subtle...

Harnessing non-spatial properties of photons as if they represent an additional independent coordinate underpins the emerging synthetic dimension approach. It enables probing of higher-dimensional physical models within low-dimensional devices, such as on a planar chip where this method is relatively nascent. We demonstrate an integrated thin-film...

Graphene oxide (GO) nanosheets, as one of the most studied graphene derivatives, have demonstrated an intrinsically strong physisorption-based gas–matter behavior, owing to its enhanced volume–surface ratio and abundant surface functional groups. The exploration of efficient and cost-effective synthesis methods for GO is an ongoing task. In this wo...

The capability to identify the frequency of unknown microwave signals with an ultra‐wide measurement bandwidth is highly desirable in radar astronomy, satellite communication, and 6G networks. Compared to electronic solutions, the integrated photonic technology‐enabled dynamic instantaneous frequency measurement (DIFM) approach is attractive as it...

Photonic metamaterials interact with light at the micro–nano scale, enabling unprecedented optical manipulation capabilities, which play a key role in nonlinear optics, spin optics, negative index, and zero index materials. Recently, thin‐film lithium niobate on insulator (LNOI) has emerged as a promising platform for integrated photonics due to it...

Photonic switches play a vital role in optical communications and computer networks for establishing and releasing connections of optical signals. With the growing demand for ultra‐compact switches in high‐speed optical computing and communications, thermally reconfigurable optical switches have gained significant attention. These switches offer si...

An ultra-broadband TM-pass polarizer is designed, fabricated, and experimentally demonstrated based on subwavelength grating (SWG) metamaterials in a lithium niobate on an insulator (LNOI) platform. According to our simulation, the designed device is predicted to work at a 220 nm wavelength range from 1460 to 1680 nm, covering the S-, C-, L-, U-ban...

Mode division multiplexing (MDM) has been widely studied in silicon photonic integrated circuits to increase data interconnection and processing capacity. Mode multiplexers and converters are important components in MDM systems. This paper proposes a novel asymmetric adiabatic taper-based device as the mode multiplexer and converter for TE0 and TE1...

We experimentally implement microcomb-based microwave photonic transversal signal processors and test their accuracy for differentiation, integration, and Hilbert transform. A global picture quantifying the impact of different error sources on the overall performance is provided.

Bragg gratings are important components in integrated photonics, however, efficiently a ccessing t he r eflected wa ves re mains ch allenging. He re, we de monstrate an asymmetric Bragg grating mode coupler in thin-film lithium niobate with 1 dB insertion loss.

We propose and experimentally demonstrate four different feedback control methods employed in microcomb-based RF photonic transversal filter systems to enhance their accuracy and stability. Detailed characterizations are carried out to compare the performance of different methods.

Harnessing non-spatial properties of photons as if they represent an additional independent coordinate underpins the emerging synthetic dimension approach. It enables probing of higher-dimensional physical models within low-dimensional devices, such as on a planar chip. We demonstrate an integrated thin-film lithium niobate ring resonator that, und...

On-chip photonic neural networks (PNN) are emerging as an attractive solution for artificial neural networks due to their high computing density, low energy consumption, and compact size. Matrix-vector multiplication (MVM) plays a key role in on-chip PNN, and can achieve high-speed multiply-accumulate operation. Most current schemes implement MVM b...

Microwave photonic (MWP) transversal signal processors offer a compelling solution for realizing versatile high-speed information processing by combining the advantages of reconfigurable electrical digital signal processing and high-bandwidth photonic processing. With the capability of generating a number of discrete wavelengths from micro-scale re...

Microwave photonic (MWP) signal processors, which process microwave signals based on photonic technologies, bring advantages intrinsic to photonics such as low loss, large processing bandwidth, and strong immunity to electromagnetic interference. Optical microcombs can offer a large number of wavelength channels and compact device footprints, which...

Metal oxysulfides are an emerging group of sensitive materials for high‐performance NO2 sensing owing to their room‐temperature operation capacity, excellent selectivity of NO2, the part‐per‐billion‐leveled limit of detection, as well as high stability against the ambient environment. Here, the room‐temperature NO2 sensing performances of zinc oxys...

Optical equalization can be used for chromatic dispersion compensation in optical communication systems to improve the system performance; however, optical signal processing (OSP) is generally specifically designed for transmission channels, that is non-adaptive to dynamic transmission distortions compared with digital signal processing (DSP). In t...

We report on a low dark current density P-B-i-N extended short-wavelength infrared photodetector with atomic layer deposited (ALD) ${{\rm Al}_2}{{\rm O}_3}$ A l 2 O 3 passivation based on a InAs/GaSb/AlSb superlattice. The dark current density of the ${{\rm Al}_2}{{\rm O}_3}$ A l 2 O 3 passivated device was reduced by 38% compared to the unpassivat...

High-speed electro-optic modulators are key components in modern communication networks and various applications that require chip-scale modulation with large bandwidth, high modulation efficiency, and compact footprint. However, fundamental trade-offs make it challenging to achieve these metrics simultaneously, and thus new methodologies must be e...

Ridge resonators are a recently introduced integrated photonic circuit element based on bound states in the continuum (BICs) which can produce a single, sharp resonance over a broad wavelength range with high extinction ratio. However, to excite these resonators, a broad beam of laterally unbound slab mode is required, resulting in a large device f...

Metasurfaces, composed of micro-nano-structured planar materials, offer highly tunable control over incident light and find significant applications in imaging, navigation, and sensing. However, highly efficient polarization devices are scarce for the extended shortwave infrared (ESWIR) range (1.7~2.5 μm). This paper proposes and demonstrates a hig...

Lithium niobate on insulator (LNOI) has emerged as a promising platform for photonic integrated circuits (PICs) due to the excellent electro‐optic (EO) properties of lithium niobate (LN). However, such a platform still lacks many critical passive components with superior performance for constructing PICs. The 3 dB power splitters are one of the imp...

Lithium niobate on insulator (LNOI) platforms promise unique advantages in realizing high-speed, large-capacity, and large-scale photonic integrated circuits (PICs) by leveraging lithium niobate’s attractive material properties, which include electro-optic and nonlinear optic properties, low material loss, and a wide transparency window. Optical mo...

On-chip photonic neural network (PNN) is emerging as an attractive solution for artificial neural networks due to its high computing density, low energy consumption, and compact size. Matrix-vector multiplication (MVM) plays a key role in on-chip PNN, which can achieve high-speed multiply-accumulate operation. Most of the current schemes implement...

The emerging 2D nanomaterials with unique optical properties are promising for next‐generation miniatured on‐chip devices. One of the prerequisites is to precisely measure their optical parameters during their implementation. However, the inherent features of 2D layers, including limited lateral dimensions and ultra‐small thicknesses, are not favor...

Reconfigurable optical directed logic circuits (RODLC) aim to perform arbitrary logic operations using the optical switch network, in which the electrical signals regarded as the logic operands are applied to the optical switch to control the propagation of light over time, and the logic operation results are obtained at the output ports of the opt...

Metasurfaces have shown an unprecedented ability to modulate electromagnetic waves at subwavelength scales, especially polarized optical metasurfaces, applied for imaging, navigation and detection. In this work, a kind of efficient all-dielectric diatomic metasurface for polarization and phase changing, consisting of a pair of GaAs nanopillar and n...

Grating‐assisted contra‐directional couplers are important optical components in photonic integrated circuits (PICs), which can serve as fundamental building blocks for optical (de)multiplexers, switches, filters, and splitters, among others. Recently, lithium niobate on insulator (LNOI) has emerged as an attractive PIC platform with many important...

Reservoir computing is an analog bio-inspired computation scheme for efficiently processing time-dependent signals, the photonic implementations of which promise a combination of massive parallel information processing, low power consumption, and high-speed operation. However, most of these implementations, especially for the case of time-delay res...

Thin-film lithium niobate on insulator (LNOI) is emerging as one of the promising platforms for integrated photonics due to the excellent material properties of lithium niobate, which includes a strong electro-optic effect, high second-order optical nonlinearity, a large optical transparency window, and low material loss. Although direct etching of...

Lithium niobate on insulator (LNOI) is a promising platform for realizing high‐performance photonic integrated circuits (PICs) for communication applications due to LN's excellent electro‐optic properties. Multimode photonic devices are attractive as they can improve the communication capacity of PICs by multiplexing orthogonal modes. For connectin...

Lithium niobate on insulator (LNOI) is a promising platform for high-speed photonic integrated circuits (PICs) that are used for communication systems due to the excellent electro-optic properties of lithium niobate (LN). In such circuits, the high-speed electro-optical modulators and switches need to be integrated with passive circuit components t...

Programmable photonic integrated circuits (PICs), offering diverse signal processing functions within a single chip, are promising solutions for applications ranging from optical communications to artificial intelligence. While the scale and complexity of programmable PICs are increasing, their characterization, and thus calibration, becomes increa...

In this contribution, we simulate, design, and experimentally demonstrate an integrated optical isolator based on spatiotemporal modulation in the thin-film lithium niobate on insulator waveguide platform. We used two cascaded travelling wave phase modulators for spatiotemporal modulation and a ring resonator as a wavelength filter to suppress the...

High efficiency and a compact footprint are desired properties for electro-optic modulators. In this paper, we propose, theoretically investigate and experimentally demonstrate a recirculating phase modulator, which increases the modulation efficiency by modulating the optical field several times in a non-resonant waveguide structure. The 'recyclin...

Monolithic Photonic Integrated Circuits In article number 2200121, Yonghui Tian, Guanghui Ren and co‐workers experimentally demonstrate a monolithic photonic integrated circuit (PIC) for high‐speed data communication application on the thin‐film lithium niobate on insulator (LNOI) platform. The proposed PIC shows high data modulation rate of 70 Gbp...

Two-dimensional (2D) semiconductors, derived from the layered bulk crystals, have been attracting considerable interest due to their atomically thin structures that lead to unique electronic, optical, and surface properties. However, many important semiconductors, such as noble metal chalcogenides and their derivatives, are difficult to directly ex...

Two-dimensional (2D) or ultrathin metal sulfides have been emerging candidates in developing high-performance gas sensors given their physisorption-dominated interaction with target gas molecules. Their oxysulfide derivatives, as intermediates between oxides and sulfides, were recently demonstrated to have fully reversible responses at room tempera...

Programmable photonic integrated circuits (PICs) are dense assemblies of tunable elements that provide flexible reconfigurability to enable different functions to be selected; however, due to manufacturing variations and thermal gradients that affect the optical phases of the elements, it is difficult to guarantee a stable correspondence between th...

We present a novel approach to high bandwidth laser frequency modulation. A lithium niobate chip is used as an intracavity electro-optic modulator in a tunable cateye external cavity diode laser. The modulator is conveniently integrated with the cateye output coupler, providing a unique approach to high bandwidth frequency stabilization and linewid...

Programmable photonic integrated circuits (PICs), offering diverse signal processing functions within a single chip, are promising solutions for applications ranging from optical communications to artificial intelligence. While the scale and complexity of programmable PICs is increasing, the characterization, and thus calibration, of them becomes i...

High efficiency and a compact footprint are desired properties for electro-optic modulators. In this paper, we propose, theoretically investigate and experimentally demonstrate a recirculating phase modulator, which increases the modulation efficiency by modulating the optical field several times in a non-resonant waveguide structure. The 'recyclin...

On-chip stimulated Brillouin scattering (SBS) that results from enhanced light-sound interactions, has recently demonstrated great applicability and versatility for signal generation and manipulation. Progress toward realizing fully integrated Brillouin photonic circuits is promising; however, the control and routing of on-chip optical waves requir...

Reservoir computing is an analog bio-inspired computation model for efficiently processing time-dependent signals, the photonic implementations of which promise a combination of massive parallel information processing, low power consumption, and high speed operation. However, most implementations, especially for the case of time-delay reservoir com...

The manipulation of optical modes directly in a multimode waveguide without affecting the transmission of undesired signal carriers is of significance to realize a flexible and simple structured optical network-on-chip. In this Letter, an arbitrary optical mode and wavelength carrier access scheme is proposed based on a series of multimode microrin...

Lithium niobate on insulator (LNOI) has been demonstrated as a promising platform for photonic integrated circuits (PICs), thanks to its excellent properties such as strong electro‐optic effect, low material loss, and wide transparency window. Herein, a monolithic PIC for high‐speed data communication application on a lithium‐niobate‐etchless platf...

Subwavelength Gratings In article number 2200130, Yonghui Tian and colleagues experimentally demonstrate compact subwavelength grating (SWG) waveguides on a LNOI platform for on‐chip mode and polarization manipulation. To overcome the limitation of direct etching waveguide fabrication, a silicon nitride thin film was deposited onto the surface of L...

Metal oxides modified with dopants and defects are an emerging class of novel materials supporting the localized surface plasmon resonance across a wide range of optical wavelengths, which have attracted tremendous research interest particularly in biological applications in the past decade. Compared to conventional noble metal-based plasmonic mate...

Resonant optical phenomena related to Fano resonances have elegantly applied to highly sensitive sensor. Here, we explore the photonic Fano formula based on the model of two directly coupled loss-loss and gain-loss optical microcavities using the temporal coupled-mode theory. The dependence of the Fano formula (the asymmetric parameter and the redu...

Lithium niobate on insulator (LNOI) has emerged as a promising platform for photonic integrated circuits, with a fast‐growing toolbox of components. This paper proposes, designs, and experimentally demonstrates compact subwavelength grating (SWG) waveguides on an LNOI platform for on‐chip mode and polarization manipulation. To overcome the limitati...

We present a novel photonic time-delay reservoir computing architecture based on an asymmetric reconfigurable Mach-Zehnder interferometer. Our simulation results show excellent performance on benchmark tasks such as NARMA10. We also explore a novel energy-efficient technique for reconfiguring the memory capacity of the system through coupling modul...

Lithium niobate on insulator (LNOI) has been demonstrated as a promising platform for photonic integrated circuits (PICs), thanks to its excellent properties such as strong electro-optic effect, low material loss and wide transparency window. In this paper, we propose and demonstrate a monolithic PIC for high-speed data communication application on...

Lithium niobate on insulator (LNOI) has emerged as a promising platform for photonic integrated circuits, with a fast-growing toolbox of components. In this paper, we propose, design and experimentally demonstrate compact subwavelength grating (SWG) waveguides on a LNOI platform for on-chip mode and polarization manipulation. To overcome the limita...

(De)Multiplexing Technologies In article number 2100529, Yonghui Tian, Arnan Mitchell, Yikai Su, and co-workers experimentally demonstrated mode and polarization-division multiplexing on a thin-film lithium niobate on insulator (LNOI) platform. By introducing silicon nitride as a loading material atop the LNOI photonics chip, the devices can be int...

Photonic integrated circuits (PICs) are capable of providing advanced signal processing functions in small footprints; however, their operation is affected by fabrication tolerances in addition to dynamically changing thermal and acoustic effects. Thus, it can be difficult to tune PICs to accurately implement desired functionality, even those with...

In this contribution, we present an experimental demonstration of high extinction TE-pass polarizers by using lateral leakage in the thin film lithium niobate on insulator waveguides, achieving a TM mode polarization suppression of 262 dB/cm.

We report the simulation and experimental demonstration of an integrated electro-optic modulator based isolator/circulator on the lithium niobate on insulator optical waveguide platform, achieving 20dB theoretical and 9dB experimental isolation.

We describe an advanced integrated optical phase modulator design that harnesses a light recycling approach with up to 3 passes to increase the efficiency of its electro-optical response. The device was fabricated on a SiN loaded lithium niobate on insulator platform and exhibited an up to 8 times enhanced modulation response for an equivalent opti...

Reversible H2 gas sensing at room temperature has been highly desirable given the booming of the Internet of Things (IoT), zero-emission vehicles, and fuel cell technologies. Conventional metal oxide-based semiconducting gas sensors have been considered as suitable candidates given their low-cost, high sensitivity, and long stability. However, the...

Mode and polarization-division multiplexing technologies (MDM and PDM) can offer considerable parallelism for optical multiplexing biosensors, complex optical neural networks, and high-capacity optical interconnects, while requiring only a single-wavelength laser source. Thanks to the mature fabrication processes of silicon nitride and superior mat...

Electro-optic (EO) modulators, which convert signals from the electrical to optical domain plays a key role in modern optical communication systems. Lithium niobate on insulator (LNOI) technology has emerged as a competitive solution to realize high-performance integrated EO modulators. In this Letter, we design and experimentally demonstrate a Mac...

Fiber-optic gas sensors have been considered a low-cost, effective, and robust approach for monitoring nitrogen dioxide (NO2) gas which is a major toxic gaseous pollutant. The integration of functional nanoscale materials provides additional dimensions for realizing ultra-sensitive and selective NO2 detection, however, the trade-off is the need for...