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(In, Ga) alloy droplets are used to catalyse the growth of (In, Ga)As nanowires by molecular beam epitaxy on Si(111) substrates. The composition, morphology and optical properties of these nanowires can be tuned by the employed elemental fluxes. To incorporate more than 10% of In, a high In/(In+Ga) flux ratio above 0.7 is required. We report a maximum In content of almost 30% in bulk (In, Ga)As nanowires for an In/(In+Ga) flux ratio of 0.8. However, with increasing In/(In+Ga) flux ratio, the nanowire length and diameter are notably reduced. Using photoluminescence and cathodoluminescence spectroscopy on nanowires covered by a passivating (In, Al)As shell, two luminescence bands are observed. A significant segment of the nanowires shows homogeneous emission, with a wavelength corresponding to the In content in this segment, while the consumption of the catalyst droplet leads to a spectrally-shifted emission band at the top of the nanowires. The (In,Ga)As nanowires studied in this work provide a new approach for the integration of infrared emitters on Si platforms. [ABSTRACT FROM AUTHOR]

Integrated quantum photonic circuits require the efficient coupling of photon sources to photonic waveguides. Hybrid plasmonic/photonic platforms are a promising approach, taking advantage of both plasmon modal confinement for efficient coupling to a nearby emitter and photonic circuitry for optical data transfer and processing. In this work, we established directional quantum dot (QD) emission coupling to a planar TiO2 waveguide assisted by a Yagi-Uda antenna. Antenna on waveguide is first designed by scaling radio frequency dimensions to nano-optics, taking into account the hybrid plasmonic/photonic platform. Design is then optimized by full numerical simulations. We fabricate the antenna on a TiO2 planar waveguide and deposit a few QDs close to the Yagi-Uda antenna. The optical characterization shows clear directional coupling originating from antenna effect. We estimate the coupling efficiency and directivity of the light emitted into the waveguide. [ABSTRACT FROM AUTHOR]

This paper describes the recent advances in device designs and optical transmission applications of semiconductor optical amplifiers (SOA). The device advances described are quantum-dot-based SOA and photonic-integrated circuits using SOA. The use of nonlinear properties of SOAs in high-speed optical transmission is discussed. [ABSTRACT FROM AUTHOR]

Abstract We present an integrated optical phased array (OPA) which embeds in-line optical amplifiers and phase modulators to provide beam-forming capability with gain and beam steering in the 1465–1590 nm wavelength range. We demonstrate up to 21.5 dB net on-chip gain and up to 35.5 mW optical output power. The OPA circuit is based on an InP photonic integration platform and features the highest measured on-chip gain and output power level recorded in an active OPA (i.e., with amplification), to the best of our knowledge. Furthermore, the OPA enables the independent control of both amplitude and phase in its arms and through this we demonstrate programmable beam shaping for two cases. First, we carried out a Gaussian apodization of the power distribution profile in the OPA emitter waveguides, leading to 19.8 dB sidelobe suppression in the far-field beam, which is the highest value recorded for active OPAs, and then we demonstrated beam forming of 0th, 1st, and 2nd order 1D Hermite–Gaussian beams in free-space.

Integrated silicon photonics has sparked a significant ramp-up of investment in both academia and industry as a scalable, power-efficient, and eco-friendly solution. At the heart of this platform is the light source, which in itself, has been the focus of research and development extensively. This paper sheds light and conveys our perspective on the current state-of-the-art in different aspects of application-driven on-chip silicon lasers. We tackle this from two perspectives: device-level and system-wide points of view. In the former, the different routes taken in integrating on-chip lasers are explored from different material systems to the chosen integration methodologies. Then, the discussion focus is shifted towards system-wide applications that show great prospects in incorporating photonic integrated circuits (PIC) with on-chip lasers and active devices, namely, optical communications and interconnects, optical phased array-based LiDAR, sensors for chemical and biological analysis, integrated quantum technologies, and finally, optical computing. By leveraging the myriad inherent attractive features of integrated silicon photonics, this paper aims to inspire further development in incorporating PICs with on-chip lasers in, but not limited to, these applications for substantial performance gains, green solutions, and mass production.

We present an integrated optical phased array (OPA) which embeds in-line optical amplifiers and phase modulators to provide beam-forming capability with gain and beam steering in the 1465–1590 nm wavelength range. We demonstrate up to 21.5 dB net on-chip gain and up to 35.5 mW optical output power. The OPA circuit is based on an InP photonic integration platform and features the highest measured on-chip gain and output power level recorded in an active OPA (i.e., with amplification), to the best of our knowledge. Furthermore, the OPA enables the independent control of both amplitude and phase in its arms and through this we demonstrate programmable beam shaping for two cases. First, we carried out a Gaussian apodization of the power distribution profile in the OPA emitter waveguides, leading to 19.8 dB sidelobe suppression in the far-field beam, which is the highest value recorded for active OPAs, and then we demonstrated beam forming of 0th, 1st, and 2nd order 1D Hermite–Gaussian beams in free-space. [ABSTRACT FROM AUTHOR]

A modelling routine has been developed to quantify effects present in p-modulation doped 1.3 μm InAs/InGaAs quantum dot laser and modulator devices. Utilising experimentally verified parameters, calculated modal absorption is compared to measurements, prior to simulation of structures under reverse and forward bias. Observed broadening and a reduction of absorption in p-doped structures is attributed primarily to increased carrier scattering rates and can bring benefit when structures are configured as optical modulators with enhancements in the figure of merit. However, increased carrier scattering limits the maximum modal gain that can be achieved for lasers. The state filling caused by p-doping only marginally reduces absorption but assists laser operation with increased differential gain and gain magnitude at lower current densities. [ABSTRACT FROM AUTHOR]

We present a novel fabrication approach to an integrated nanophotonic platform, based on a III-V membrane bonded to a Si substrate with benzocyclobutene (BCB). The process incorporates a hybrid lithography strategy combining deep-UV and electron-beam lithography on the same wafer. We report for the first time the usage of deep-UV scanner lithography for the fabrication of the active-passive tapers and sub-micron waveguides on the same wafer, which enables better critical dimension control, uniformity, and reproducibility. The platform uses an active-passive butt-joint interface and includes components such as distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, electro-optical (EO) and electro-absorption (EA) modulators, and sub-micron ultra-confined passive waveguides, all monolithically integrated into a single membrane layer. The active devices have a heat sink achieved by ultra-thin BCB bonding. Lasers demonstrate up to 26 mW of optical power in the waveguide and a direct modulation bandwidth of up to 21 GHz. The modulators show static extinction up to 28.8 dB.

In this paper, we present our process design kits (PDKs) component performances for different wavelengths in the visible to near-infrared (VIS-NIR) range on Shanghai Industrial μTechnology Research Institute's (SITRI's) 200 mm silicon nitride (SiN) photonics platform. SiN waveguide platform has emerged as a promising technology due to its low optical loss, relatively high refractive index, and transparency across the VIS-NIR spectrum. The industrialization of SiN platforms requires matured PDKs. On SITRI's 200 mm SiN photonics platform, we developed PDKs using both Plasma-Enhanced Chemical Vapor Deposition (PECVD) and Low-Pressure Chemical Vapor Deposition (LPCVD) processes, with SiN layers of 180 nm and 150 nm thicknesses, respectively. The fabricated waveguides exhibit low propagation loss, ranging from 2.5 dB/cm to 0.34 dB/cm from 532 nm to 860 nm. Additionally, we present a low bending loss which is less than 0.06 dB/90° with a radius of 100 μm. Furthermore, the loss of the linear grating coupler (LGC) is less than 2.6 dB at 785 nm. We have also achieved low-loss splitters, including 1 × 2 multimode interference (MMI) coupler, and directional coupler (DC), with a minimum excess loss of 0.03 dB. Additionally, micro ring resonator with high quality (Q) factors of 146,000 has been demonstrated. Our work on developing these PDKs will open new opportunities for researchers and developers to design and fabricate advanced photonic devices on the SiN platform in SITRI's 200 mm fabrication line.

Broadband terahertz spectroscopy is a valuable analytical tool in science and a promising technology for industrial non-destructive, non-contact testing, e.g. thickness measurements of thin dielectric layers. Optoelectronic conversion using photomixers is a widespread approach for coherent terahertz spectroscopy. State-of-the-art spectrometers consist of discrete, fiber-based components, leading to complex and costly setups. In cost-sensitive applications, this prevents the use of these spectrometers. We developed a terahertz spectrometer based on a dedicated photonic integrated circuit and commercial electronic integrated circuits to overcome these limitations. The photonic subsystem can be connected to commercial tunable lasers and provides the optical signal processing to drive the photoconductive antennas. The electronic subsystem includes the required drivers, analog signal processing, and data acquisition. Combined, the system measures $10 \times 16 \times 7.5$ cm3 only. We compare both subsystems individually and as a whole to state-of-the-art lab equipment in terms of spectral performance and measurement speed. Due to the flexibility in measurement modes, the integrated system can be adapted to specific measurement tasks, e.g. 2.8 THz-wide spectra within 0.5 s for high-speed, or 3.6 THz bandwidth with >80 dB dynamic range in less than 3 minutes for high-precision. This is the first realization of a terahertz spectrometer based on photonic and electronic integration rivaling state-of-the-art and non-integrated commercial spectrometers. This approach paves the way for compact and economic terahertz systems, providing access to terahertz technology for cost-sensitive sectors in research and industry.

Multi-photon lithography has emerged as a powerful tool for photonic integration, allowing to complement planar photonic circuits by 3D-printed freeform structures such as waveguides or micro-optical elements. These structures can be fabricated with a high precision on the facets of optical devices and enable highly efficient package-level chip–chip connections in photonic assemblies. However, plain light transport and efficient coupling is far from exploiting the full geometrical design freedom offered by 3D laser lithography. Here, we extended the functionality of 3D-printed optical structures to manipulation of optical polarisation states. We demonstrate compact ultra-broadband polarisation beam splitters (PBSs) that can be combined with polarisation rotators and mode-field adapters into a monolithic 3D-printed structure, fabricated directly on the facets of optical devices. In a proof-of-concept experiment, we demonstrate measured polarisation extinction ratios beyond 11 dB over a bandwidth of 350 nm at near-infrared telecommunication wavelengths around 1550 nm. We demonstrate the viability of the device by receiving a 640 Gbit/s dual-polarisation data signal using 16-state quadrature amplitude modulation (16QAM), without any measurable optical-signal-to-noise-ratio penalty compared to a commercial PBS.

On-chip optical dispersion compensation and wavelength division multiplexing/demultiplexing (WDM) are highly demanded functions for optical communications. In this work, we proposed a multichannel dispersion compensation structure based on chirped multimode grating within a counter-directional coupler (CMG-CDC). Simultaneous wavelength division multiplexing and demultiplexing can be realized within a compact footprint. A device design for four-channel CMG-CDC at the C/L (1530–1565 nm) band is presented with a channel spacing of 20 nm assisted by a grooved multimode waveguide structure. The average dispersion for all channels is about −2.25 ps/nm with a channel bandwidth of about 3.1 nm. The device is highly compact and highly scalable, which makes it rather convenient for increasing the group velocity dispersion (GVD) and channel number, indicating flexible applications for versatile systems, including typically coarse wavelength division multiplexer four-lane (CWDM4) transceivers. [ABSTRACT FROM AUTHOR]

Efficient mode conversion is crucial for hybrid photonic systems. We present efficient light transition from a standard single-mode fiber (SMF) to a subwavelength-diameter microfiber via a relatively short tapered fiber. Numerical simulations were performed to design the tapered morphology with high transmittance (approximately 86%) for the fundamental modes. The designed tapered fiber was successfully fabricated on the top of a cleaved SMF tip by the direct laser writing (DLW) method. For the 1550 nm wavelength, the transmittance from the standard SMF to the subwavelength-diameter microfiber was determined to be 77%, accompanied by a change in the effective mode area from 38 μm2 to 0.47 μm2 within a very short length of 150 μm. Our result demonstrated the versatility of the DLW technique for boosting the mode conversion efficiency of fiber-to-chip devices, enabling various applications in the future. [ABSTRACT FROM AUTHOR]

Wafer-level mass production of photonic integrated circuits (PIC) has become a technological mainstay in the field of optics and photonics, enabling many novel and disrupting a wide range of existing applications. However, scalable photonic packaging and system assembly still represents a major challenge that often hinders commercial adoption of PIC-based solutions. Specifically, chip-to-chip and fiber-to-chip connections often rely on so-called active alignment techniques, where the coupling efficiency is continuously measured and optimized during the assembly process. This unavoidably leads to technically complex assembly processes and high cost, thereby eliminating most of the inherent scalability advantages of PIC-based solutions. In this paper, we demonstrate that 3D-printed facet-attached microlenses (FaML) can overcome this problem by opening an attractive path towards highly scalable photonic system assembly, relying entirely on passive assembly techniques based on industry-standard machine vision and/or simple mechanical stops. FaML can be printed with high precision to the facets of optical components using multi-photon lithography, thereby offering the possibility to shape the emitted beams by freely designed refractive or reflective surfaces. Specifically, the emitted beams can be collimated to a comparatively large diameter that is independent of the device-specific mode fields, thereby relaxing both axial and lateral alignment tolerances. Moreover, the FaML concept allows to insert discrete optical elements such as optical isolators into the free-space beam paths between PIC facets. We show the viability and the versatility of the scheme in a series of selected experiments of high technical relevance, comprising pluggable fiber-chip interfaces, the combination of PIC with discrete micro-optical elements such as polarization beam splitters, as well as coupling with ultra-low back-reflection based on non-planar beam paths that only comprise tilted optical surfaces. Based on our results, we believe that the FaML concept opens an attractive path towards novel PIC-based system architectures that combine the distinct advantages of different photonic integration platforms.

Abstract We demonstrate a compact heterodyne Laser Doppler Vibrometer (LDV) based on the realization of optical frequency shift in the silicon nitride photonic integration platform (TriPleX). We theoretically study, and experimentally evaluate two different photonic integrated optical frequency shifters (OFSs), utilizing serrodyne and single-sideband (SSB) modulation. Both OFSs employ stress-optic modulators (SOMs) based on the non-resonant piezoelectrical actuation of lead zirconate titanate (PZT) thin-films, deposited on top of the silicon nitride waveguides with a wafer-scale process. To improve the modulation bandwidth of the SOMs we investigate a novel configuration of the electrodes used for the actuation, where both electrodes are placed on top of the PZT layer. Using this top-top electrode configuration we report frequency shift of 100 kHz and 2.5 MHz, and suppression ratio of the unwanted sidebands of 22.1 dB and 39 dB, using the serrodyne and the SSB OFS, respectively. The best performing SOM structure induces 0.25π peak-to-peak sinusoidal phase-shift with 156 mW power dissipation at 2.5 MHz. We use the SSB-OFS in our compact LDV system to demonstrate vibration measurements in the kHz regime. The system comprises a dual-polarization coherent detector built in the PolyBoard platform, utilizing hybrid integration of InP photodiodes (PDs). High quality LDV performance with measurement of vibration frequencies up to several hundreds of kHz and displacement resolution of 10 pm are supported with our system.

We demonstrate a compact heterodyne Laser Doppler Vibrometer (LDV) based on the realization of optical frequency shift in the silicon nitride photonic integration platform (TriPleX). We theoretically study, and experimentally evaluate two different photonic integrated optical frequency shifters (OFSs), utilizing serrodyne and single-sideband (SSB) modulation. Both OFSs employ stress-optic modulators (SOMs) based on the non-resonant piezoelectrical actuation of lead zirconate titanate (PZT) thin-films, deposited on top of the silicon nitride waveguides with a wafer-scale process. To improve the modulation bandwidth of the SOMs we investigate a novel configuration of the electrodes used for the actuation, where both electrodes are placed on top of the PZT layer. Using this top-top electrode configuration we report frequency shift of 100 kHz and 2.5 MHz, and suppression ratio of the unwanted sidebands of 22.1 dB and 39 dB, using the serrodyne and the SSB OFS, respectively. The best performing SOM structure induces 0.25π peak-to-peak sinusoidal phase-shift with 156 mW power dissipation at 2.5 MHz. We use the SSB-OFS in our compact LDV system to demonstrate vibration measurements in the kHz regime. The system comprises a dual-polarization coherent detector built in the PolyBoard platform, utilizing hybrid integration of InP photodiodes (PDs). High quality LDV performance with measurement of vibration frequencies up to several hundreds of kHz and displacement resolution of 10 pm are supported with our system. [ABSTRACT FROM AUTHOR]

RF photonic transversal signal processors, which combine reconfigurable electrical digital signal processing and high-bandwidth photonic processing, provide a powerful solution for achieving adaptive high-speed information processing. Recent progress in optical microcomb technology provides compelling multi-wavelength sources with a compact footprint, yielding a variety of microcomb-based RF photonic transversal signal processors with either discrete or integrated components. Although they operate based on the same principle, the processors in these two forms exhibit distinct performances. This paper presents a comparative investigation of their performances. First, we compare the performances of state-of-the-art processors, focusing on the processing accuracy. Next, we analyze various factors that contribute to the performance differences, including the tap number and imperfect response of experimental components. Finally, we discuss the potential for future improvement. These results provide a comprehensive comparison of microcomb-based RF photonic transversal signal processors implemented using discrete and integrated components and provide insights for their future development. [ABSTRACT FROM AUTHOR]

The integration of high-quality III–V light sources on the Si platform has encountered a challenge that demands a highly precise on-demand addressability of single devices in a significantly reduced integration area. However, simple schemes to address the issue without causing major optical losses remain elusive. Here, we propose a waveguide-integrated microlaser-on-silicon in which the III–V/Si integration requires only a small micron-sized post structure with a diameter of <2 µm and enables efficient light coupling with an estimated coupling efficiency of 44.52%. Top-down fabricated high-quality microdisk cavities with an active gain medium were precisely micro-transferred on a small Si-post structure that was rationally designed in the vicinity of a strip-type Si waveguide (WG). Spectroscopic measurements exhibit successful lasing emission with a threshold of 378.0 µW, bi-directional light coupling, and a propagation of >50 µm through the photonic Si WG. Numerical study provides an in-depth understanding of light coupling and verifies the observations in the experiment. We believe that the proposed microlaser-on-Si is a simple and efficient scheme requiring a minimum integration volume smaller than the size of the light source, which is hard to achieve in conventional integration schemes and is readily applicable to various on-demand integrated device applications. [ABSTRACT FROM AUTHOR]

Current development trends concerning miniaturizing of electronics and photonics systems are aiming at assembly and 3D co-integration of a broad range of technologies including MEMS, microfluidics, wafer level optics, multilayered structures with through-silicon vias connection, and silicon photonics. Modern integration processes impose severe requirements on the design and functionality of research and assembly setups and their parts. In this work we demonstrate a simple, reliable, and cost-effective reconfigurable vacuum sample holder that ensures fast reconfiguration for electronic and photonic integration using laser assisted bonding (LAB) processes. The design is compatible with IR through-silicon microscopy with top and bottom irradiation/illumination architectures, which makes this concept instrumental for a large variety of research, assembly, lithography, and wafer bonding setups.

Planetary, lunar, and deep space exploration has become the frontier of remote sensing science, and three-dimensional (3D) positioning imaging technology is an important part of lunar and deep space exploration. This paper presents a novel passive 3D imaging method based on the photonics integrated interference computational imaging system. This method uses a photonics integrated interference imaging system with a complex lens array. The midpoints of the interference baselines formed by these lenses are not completely overlapped. The distance between the optical axis and the two lenses of the interference baseline are not equal. The system is used to obtain the complex coherence factor of the object space at a limited working distance, and the image evaluation optimization algorithm is used to obtain the clear images and 3D information of the targets of interest. The simulation results show that this method is effective for the working scenes with targets located at single or multiple limited working distances. The sharpness evaluation function of the target presents a good unimodality near its actual distance. The experimental results of the interference of broad-spectrum light show that the theoretical basis of this method is feasible. [ABSTRACT FROM AUTHOR]

We report for the first time the direct growth of quantum dot (QD) lasers with electrical pumping on 300 mm Si wafers on both a planar template and in-pocket template for in-plane photonic integration. O-band lasers with five QD layers were grown with molecular beam epitaxy (MBE) in a 300 mm reactor and then fabricated into standard Fabry–Perot ridge waveguide cavities. Edge-emitting lasers are demonstrated with high yield and reliable results ready for commercialization and scaled production, and efforts to make monolithically integrated lasing cavities grown on silicon-on-insulator (SOI) wafers vertically aligned and coupled to SiN waveguides on the same chip show the potential for 300 mm-scale Si photonic integration with in-pocket direct MBE growth. [ABSTRACT FROM AUTHOR]

On-chip optical dispersion compensation and wavelength division multiplexing/demultiplexing (WDM) are highly demanded functions for optical communications. In this work, we proposed a multichannel dispersion compensation structure based on chirped multimode grating within a counter-directional coupler (CMG-CDC). Simultaneous wavelength division multiplexing and demultiplexing can be realized within a compact footprint. A device design for four-channel CMG-CDC at the C/L (1530–1565 nm) band is presented with a channel spacing of 20 nm assisted by a grooved multimode waveguide structure. The average dispersion for all channels is about −2.25 ps/nm with a channel bandwidth of about 3.1 nm. The device is highly compact and highly scalable, which makes it rather convenient for increasing the group velocity dispersion (GVD) and channel number, indicating flexible applications for versatile systems, including typically coarse wavelength division multiplexer four-lane (CWDM4) transceivers.

Photonic integration brings the promise of significant cost, power and space savings and propels the real applications of microwave photonic technology. In this paper, a multiband radio frequency (RF) signal simultaneous receiver using an optical bandpass filter (OBPF) integrated with a photodetector (PD) on a chip is proposed, which was experimentally demonstrated. The OBPF was composed of ring-assisted Mach–Zehnder interferometer with a periodical bandpass response featuring a box-like spectral shape. The OBPF was connected to a PD and then integrated onto a single silicon photonic chip. Phase-modulated multiband RF signals transmitted from different locations were inputted into the OBPF, by which one RF sideband was filtered out and the phase modulation to intensity modulation conversion was realized. The single sideband with carrier signals were then simultaneously detected by the PD. A proof-of-concept experiment with the silicon photonic integrated chip was implemented to simultaneously receive four channels of 8 GHz, 12 GHz, 14 GHz and 18 GHz in the X- and Ku-bands. The performance of the integrated microwave photonic multiband receiver—including the receiving sensitivity, the spurious free dynamic range, the gain and the noise figure across the whole operation frequency band—was characterized in detail. [ABSTRACT FROM AUTHOR]

We propose a parity-baseline segmented planar imaging method with more frequency components by changing different baseline selection to achieve better imaging in the rotational process. A theoretical model of the parity-baseline segmented planar imaging system with rotational operation is built to analyze the imaging effect. The simulation results show that the imaging quality of the parity-baseline segmented planar imaging system has an approximately 20% increase by rotation compared with the conventional system. In addition, the CLEAN algorithm in radio astronomy imaging is also applied to the parity-baseline segmented planar imaging system, and the image quality is further improved by 55%. Such a new imaging method holds great potential toward astronomical observation and detection. [ABSTRACT FROM AUTHOR]

Efficient mode conversion is crucial for hybrid photonic systems. We present efficient light transition from a standard single-mode fiber (SMF) to a subwavelength-diameter microfiber via a relatively short tapered fiber. Numerical simulations were performed to design the tapered morphology with high transmittance (approximately 86%) for the fundamental modes. The designed tapered fiber was successfully fabricated on the top of a cleaved SMF tip by the direct laser writing (DLW) method. For the 1550 nm wavelength, the transmittance from the standard SMF to the subwavelength-diameter microfiber was determined to be 77%, accompanied by a change in the effective mode area from 38 μm2 to 0.47 μm2 within a very short length of 150 μm. Our result demonstrated the versatility of the DLW technique for boosting the mode conversion efficiency of fiber-to-chip devices, enabling various applications in the future.

RF photonic transversal signal processors, which combine reconfigurable electrical digital signal processing and high-bandwidth photonic processing, provide a powerful solution for achieving adaptive high-speed information processing. Recent progress in optical microcomb technology provides compelling multi-wavelength sources with a compact footprint, yielding a variety of microcomb-based RF photonic transversal signal processors with either discrete or integrated components. Although they operate based on the same principle, the processors in these two forms exhibit distinct performances. This paper presents a comparative investigation of their performances. First, we compare the performances of state-of-the-art processors, focusing on the processing accuracy. Next, we analyze various factors that contribute to the performance differences, including the tap number and imperfect response of experimental components. Finally, we discuss the potential for future improvement. These results provide a comprehensive comparison of microcomb-based RF photonic transversal signal processors implemented using discrete and integrated components and provide insights for their future development.

In this work, a prototype of 10G Combo-PON OLT transceiver based on photonic integrated circuits (PIC) is proposed and demonstrated. Key optical components for Combo-PON OLT transceiver, including high-power DFB laser, micro-ring modulator and WDM, have been developed and validated. The Combo-PON OLT transceiver integrated four XGS-PON/GPON ports and all ports comply with I-TUT G.984.2 Class C+ standard. The advantages and disadvantages of PIC in PON application are analyzed. The analysis shows that PIC can also provide a cost and power-efficient way to implement the next generation PON transceiver for high density PON ports.

In this work, a prototype of 10G Combo-PON OLT transceiver based on photonic integrated circuits (PIC) is proposed and demonstrated. Key optical components for Combo-PON OLT transceiver, including high-power DFB laser, micro-ring modulator and WDM, have been developed and validated. The Combo-PON OLT transceiver integrated four XGS-PON/GPON ports and all ports comply with I-TUT G.984.2 Class C+ standard. The advantages and disadvantages of PIC in PON application are analyzed. The analysis shows that PIC can also provide a cost and power-efficient way to implement the next generation PON transceiver for high density PON ports. [ABSTRACT FROM AUTHOR]

In many application scenarios, silicon (Si) photonics favors the integration of III-V gain material onto Si substrate to realize the on-chip light source. In addition to the current popular integration approaches of III-V-on-Si wafer bonding or direct heteroepitaxial growth, a newly emerged promising solution of epitaxial regrowth on bonded substrate has attracted a lot of interests. High-quality III-V material realization and successful laser demonstrations show its great potential to be a promising integration platform for low-cost, high-integration density and highly scalable active-passive photonic integration on Si. This paper reviews recent research work on this regrowth on bonded template platform including template developments, regrown material characterizations and laser demonstrations. The potential advantages, opportunities and challenges of this approach are discussed.

The integration of high-quality III–V light sources on the Si platform has encountered a challenge that demands a highly precise on-demand addressability of single devices in a significantly reduced integration area. However, simple schemes to address the issue without causing major optical losses remain elusive. Here, we propose a waveguide-integrated microlaser-on-silicon in which the III–V/Si integration requires only a small micron-sized post structure with a diameter of 50 µm through the photonic Si WG. Numerical study provides an in-depth understanding of light coupling and verifies the observations in the experiment. We believe that the proposed microlaser-on-Si is a simple and efficient scheme requiring a minimum integration volume smaller than the size of the light source, which is hard to achieve in conventional integration schemes and is readily applicable to various on-demand integrated device applications.

We report for the first time the direct growth of quantum dot (QD) lasers with electrical pumping on 300 mm Si wafers on both a planar template and in-pocket template for in-plane photonic integration. O-band lasers with five QD layers were grown with molecular beam epitaxy (MBE) in a 300 mm reactor and then fabricated into standard Fabry–Perot ridge waveguide cavities. Edge-emitting lasers are demonstrated with high yield and reliable results ready for commercialization and scaled production, and efforts to make monolithically integrated lasing cavities grown on silicon-on-insulator (SOI) wafers vertically aligned and coupled to SiN waveguides on the same chip show the potential for 300 mm-scale Si photonic integration with in-pocket direct MBE growth.

We demonstrate the Mach-Zehnder interferometer (MZI) silicon-based electro-optic modulators in the short-wave mid-infrared 2 μm band. The waveguide structure and doping position of the devices are optimized by simulation. The devices are manufactured on a 220 nm silicon-on-insulator (SOI) platform, and are measured through self-built short-wave mid-infrared measurement platform. The device with the length of 3.5 mm has a measured modulation efficiency of 1.853 V cm at 3 V reverse bias. The highspeed characterization is also performed, and the device with the length of 3.5 mm has a data rate of over 20 Gb/s at the voltage swing of 2.8 V pp with on-off keying (OOK) modulation formats. The modulation speed of the 2 mm device can reach over 40 Gb/s with 4-level pulse amplitude modulation (PAM-4) formats at a voltage swing of 2.5 V pp. • A MZI electro-optic modulator in MIR based on SOI platform is designed. • The simulated bandwidth is 35.81 GHz for a 3.5 mm length modulator. • The modulation speed of the 2 mm device can reach over 40 Gb/s with PAM-4 formats. • The 3.5 mm device has a data rate of over 20 Gb/s with OOK modulation formats. [ABSTRACT FROM AUTHOR]

Structured light, also known as tailored light, shaped light, sculpted light, or custom light, refers to a series of special light beams with spatially variant amplitudes and phases, polarization distributions, or more general spatiotemporal profiles. In the past decades, structured light featuring distinct properties and unique spatial or spatiotemporal structures has grown into a significant research field and given rise to many developments from fundamentals to applications. Very recently, integrated structured light manipulation has become an important trend in the frontier of light field manipulation and attracted increasing interest as a highly promising technique for shaping structured light in an integrated, compact, and miniaturized manner. In this article, we give a comprehensive overview of recent advances in integrated structured light manipulation (generation, processing, detection, and application). After briefly introducing the basic concept and development history of structured light, we present representative works in four important aspects of integrated structured light manipulation, including multiple types of integrated structured light generation, many sorts of integrated structured light processing, diverse forms of integrated structured light detection, and various kinds of integrated structured light applications. We focus on summarizing the progress of integrated structured light manipulation from basic theories to cutting-edge technologies, to key devices, and to a wide variety of applications, from orbital angular momentum carrying light beams to more general structured light beams, from passive to active integration platforms, from micro-nano structures and metasurfaces to 2D photonic integrated circuits and 3D photonic chips, from in-plane to out-of-plane, from multiplexing to transformation, from linear to nonlinear, from classical to quantum, from optical communications to optical holography, imaging, microscopy, trapping, tweezers, metrology, etc. Finally, we also discuss in detail the future trends, opportunities, challenges, and solutions, and give a vision for integrated structured light manipulation. [ABSTRACT FROM AUTHOR]

Planetary, lunar, and deep space exploration has become the frontier of remote sensing science, and three-dimensional (3D) positioning imaging technology is an important part of lunar and deep space exploration. This paper presents a novel passive 3D imaging method based on the photonics integrated interference computational imaging system. This method uses a photonics integrated interference imaging system with a complex lens array. The midpoints of the interference baselines formed by these lenses are not completely overlapped. The distance between the optical axis and the two lenses of the interference baseline are not equal. The system is used to obtain the complex coherence factor of the object space at a limited working distance, and the image evaluation optimization algorithm is used to obtain the clear images and 3D information of the targets of interest. The simulation results show that this method is effective for the working scenes with targets located at single or multiple limited working distances. The sharpness evaluation function of the target presents a good unimodality near its actual distance. The experimental results of the interference of broad-spectrum light show that the theoretical basis of this method is feasible.

Heterogeneous integration of electro-optic (EO) crystal thin film on insulator has become an attractive platform to achieve high-performance and compact modulators. While there has been some impressive research on the development of such modulators, a critical consideration is the relatively complex heterogeneous-integrating process. In this work, we demonstrate EO modulators based on lead zirconate titanate (PZT) crystal thin film on SiO2/Si substrate, where the PZT is epitaxially-grown via the straightforward chemical solution deposition method. The presented device exhibits a voltage–length product VπL of 1.4 V·cm and a propagation loss of 1.8 dB/cm at the wavelength of 1550 nm. The measured 3-dB bandwidth of a 5 mm-long device is 12 GHz, which can be improved by further optimizing the travelling-wave electrodes. The proposed technique should enable low-cost and mass-production of power-efficient modulators and to promote the development of photonic integration. [ABSTRACT FROM AUTHOR]

Integrated photonics are fast-developing research field for next generation information technology. Current silicon photonic integrated chips strongly benefit from low-cost and high-density integration properties of existing CMOS technology. But limited by the physical properties of silicon, it is not a perfect material for different types of optoelectronic devices, such as laser sources, modulators, and infrared detectors. Therefore, heterogeneous integration is proposed by combining the advantages of CMOS process and superior opto-electric properties of heterogenous material systems, that can be an essential step towards next generation integrated optoelectronic chips. Here, this paper introduces the rapid progress of integrated photonics nationally and worldwide, while discusses the potential directions and opportunities in this field. [ABSTRACT FROM AUTHOR]

Quantum dot (QD) lasers epitaxially grown on Si have already been demonstrated to show record low threshold, high temperature tolerance, and low feedback sensitivity. When grown on the silicon photonic chip and integrated with Si waveguides (WGs), QD lasers offer considerable economical and foundry‐scalable solutions to on‐chip light sources. Yet, a technology that enables both growth and integration of QD lasers on a silicon photonic chip has not been demonstrated. Herein, a novel device platform which enables integration of the QD active region with passive WG structures is designed. By doing so, complex and high‐performance lasers such as distributed Bragg reflector lasers, mode‐locked lasers, and sampled grating distributed Bragg reflector tunable lasers are demonstrated in this platform. The same laser epitaxial stack can be easily grown on the substrate of a silicon photonic chip to allow light coupling from QD laser cavities to the silicon WGs. [ABSTRACT FROM AUTHOR]

Whispering-gallery mode (WGM) microlasers are potential light sources for photonic integrated circuits and optical information processing. In this paper, an integrated twin circular-side octagon microlaser (TCOM) composed of two identical circular-side octagon microcavities (COMs) is proposed and demonstrated for realizing lasing mode control. In a TCOM, we found a global mode with the mode field of an “8” pattern (labeled “8” mode) in addition to weak coupling modes of traditional four-bounce modes. The “8” mode belongs to the whole coupled cavity and is insensitive to the refractive index offset of coupled COMs, but the weak coupling modes are strongly sensitive to the refractive index offset. Lasing mode transformation from multiple coupled modes to a single “8” mode is demonstrated by adjusting the refractive index offset through injection currents. Weak coupling modes for directly connected TCOMs and lasing mode control make the COM a potential unit for large-scale photonic integration and optical information processing. [ABSTRACT FROM AUTHOR]

Photonics-based techniques spearhead the generation of high-frequency signals in the millimeter-and Terahertz wave, crucial for ultrabroadband mobile wireless link development. Photonic integration is enabling to provide the photonic approach with added advantages of energy-efficiency, flexibility and scalability, in addition to signal quality. We present an optical heterodyne system based on a novel dual laser module containing two InP-Si3N4 hybrid lasers with intracavity wavelength selective optical filters with output optical power per laser of up to 15 dBm (31 mW), wide wavelength tuning of about 60 nm, and narrow optical linewidth below 100 kHz. To the best of our knowledge, we present for the first time the continuous-wave generation of RF frequencies over a wide tuning range from C-band (4 GHz – 8-GHz) to W-band (75 GHz – 110 GHz) achieving record low RF electrical linewidth around 108 kHz and long-term drift < 12 MHz with two free-running lasers. This is the best beat-note linewidth obtained with such an integrated source in a free-runnning regime and with a wide tuning range ever reported. [ABSTRACT FROM AUTHOR]

Abstract Focusing grating couplers for the excitation of the fundamental transverse-magnetic (TM) mode in integrated silicon photonic waveguides are designed and characterized under the boundary conditions of a photonic BiCMOS foundry. Two types of waveguide geometries are considered – a nanowire and a rib waveguide. Wafer-scale experimental results for nanowire TM grating couplers are in excellent agreement with numerical investigations and demonstrate a robust behavior on the wafer. The mean coupling loss and the 3σ interval are -3.9 ± 0.3 dB. The on wafer variation is three times lower than for the fundamental transverse-electric (TE) polarization. Similarly, the coupling in rib waveguides is examined as well. The results indicate that the rib waveguides require a modified geometry when designed for TM. In general, the nanowire waveguide type is more suitable for TM coupling, showing a stable and repeatable performance.

Monitoring the state of the optical network is a key enabler for programmability of network functions, protocols and efficient use of the spectrum. A particular challenge is to provide the SDN-EON controller with a panoramic view of the complete state of the optical spectrum. This paper describes an architecture for compact on-chip spectrometry targeting high resolution across the entire C-band to reliably and accurately measure the spectral profile of WDM signals in fixed and flex-grid architectures. An industry standard software tool is used to validate the performance of the spectrometer. The fabrication of the proposed design is found to be practical.

A review of photonic integrated optical phased array (OPA) for space optical communication is presented. We review and summarize the typical works of the photonic integrated OPAs with one-dimensional and two-dimensional optical antenna array in recent years. The basic components of the photonic integrated OPA are introduced separately, including optical coupler, optical power division network, phase shifter, and optical antenna. In addition, the configuration of the optical antenna array and the control circuit are introduced for OPA beam steering. The basic principle and experiment setup for testing the radiation properties of the OPA are presented. A proof-of-concept nonuniform silicon integrated OPA with 64 antennas is designed and a one-dimensional beam steering range of 28° is achieved with beam width of about 0.25°. The challenges and development trends of large-scale integrated OPA chip applied in space optical communication are also discussed.

Photonic integration brings the promise of significant cost, power and space savings and propels the real applications of microwave photonic technology. In this paper, a multiband radio frequency (RF) signal simultaneous receiver using an optical bandpass filter (OBPF) integrated with a photodetector (PD) on a chip is proposed, which was experimentally demonstrated. The OBPF was composed of ring-assisted Mach–Zehnder interferometer with a periodical bandpass response featuring a box-like spectral shape. The OBPF was connected to a PD and then integrated onto a single silicon photonic chip. Phase-modulated multiband RF signals transmitted from different locations were inputted into the OBPF, by which one RF sideband was filtered out and the phase modulation to intensity modulation conversion was realized. The single sideband with carrier signals were then simultaneously detected by the PD. A proof-of-concept experiment with the silicon photonic integrated chip was implemented to simultaneously receive four channels of 8 GHz, 12 GHz, 14 GHz and 18 GHz in the X- and Ku-bands. The performance of the integrated microwave photonic multiband receiver—including the receiving sensitivity, the spurious free dynamic range, the gain and the noise figure across the whole operation frequency band—was characterized in detail.

We propose a parity-baseline segmented planar imaging method with more frequency components by changing different baseline selection to achieve better imaging in the rotational process. A theoretical model of the parity-baseline segmented planar imaging system with rotational operation is built to analyze the imaging effect. The simulation results show that the imaging quality of the parity-baseline segmented planar imaging system has an approximately 20% increase by rotation compared with the conventional system. In addition, the CLEAN algorithm in radio astronomy imaging is also applied to the parity-baseline segmented planar imaging system, and the image quality is further improved by 55%. Such a new imaging method holds great potential toward astronomical observation and detection.

We present operation of a photonically integrated wavelength reference at 780 nm using a dual beam geometry. The dual beams are generated by a pair of extreme mode converting grating beam expanders that generate a pair of overlapped, counter-propagating beams inside the volume of a microfabricated vapor cell. We perform spectroscopy of rubidium and a characterize the stability of laser locked to a sub-Doppler transition at 780 nm. By stabilizing the laser to a known transition in an atomic vapor, this device can serve as a quantum wavelength reference. The dual beam geometry also enables investigation of two-photon absorption in a three-level ladder configuration in rubidium using excitation at 780 nm + 776 nm.