Search Results (17)

With the rapid growth of data center demand driven by AI, high-speed optical modules (such as 800G and 1.6T) have become critical components. Traditional 800G modules face issues such as complex processes and large sizes due to the separate packaging of EML chips, AlN substrates, and capacitors. This study proposes a high-speed EML module based on silicon integration, where resistors, capacitors, and AuSn soldering areas are integrated onto the silicon substrate, enabling the bonding of the EML chip, reducing packaging costs, and enhancing scalability. Key achievements include: the development of a 100G EML chip; the fabrication of a high-speed silicon integrated carrier; successful Chip-on-Carrier (COC) packaging and testing, with a laser output power of 10 mW, extinction ratio of 10 dB, and bandwidth greater than 40 GHz; and reliability verified through 500 h of aging tests. This study provides an expandable solution for next-generation high-speed optical interconnects. Full article

This paper presents a highly stable and integrated silicon-based carrier with broad application prospects. Traditional 800 G optical modules employ architectures based on aluminum nitride (AlN) carriers with externally mounted capacitors. However, such AlN-based architectures suffer from issues including high process complexity, elevated costs, poor environmental temperature adaptability, and difficulties in systematic crosstalk optimization. To address these challenges, this study conducted research on coplanar waveguide (CPW) transmission line structure design and optimization, high-density capacitor design and process implementation, and multi-channel crosstalk suppression. Based on these investigations, a silicon-based integrated carrier was designed and fabricated, incorporating resistors, capacitors, high-speed signal lines, and preformed AuSn structures. Test results demonstrate that the CPW transmission line structures fabricated on the silicon carrier exhibit excellent radio frequency performance with transmission losses below 1 dB within 67 GHz. The developed high-density capacitor structure achieves a remarkable capacitance density of 26.83 nF/mm² and withstands voltages exceeding 24 V at 1 μA current, reaching state-of-the-art levels. This paper also proposes crosstalk reduction solutions including increased channel spacing, the addition of wave-absorbing materials, and the implementation of metal barriers. Experimental results confirm that the developed integrated carrier demonstrates outstanding performance and reliability in high-frequency communications and optoelectronic devices. Full article

A novel simplifying Volterra structure algorithm is proposed for an intensity modulation direct detection (IM-DD) optical fiber short distance communication system using the decision feedback equalization algorithm (DFE). Based on this algorithm, the signal damage for the four-level pulse amplitude modulation signal (PAM-4) is compensated, which is caused by device bandwidth limitation and dispersion during transmission. Experiments have been carried out using a 25 GHz Electro-absorption Modulated Laser (EML), showing that PAM-4 signals can transmit over 10 km in standard single-mode fiber (SSMF). The 112 Gbps and 128 Gbps signals can reach the error rate threshold of KP4-FEC (BER = 2 × 10⁻⁴) and HD-FEC (BER = 3.8 × 10⁻³), respectively. The simplified principle and process of the proposed Volterra-based equalization algorithm are presented. Experimental results show that the algorithm complexity is greatly reduced by 75%, which provides effective theoretical support for the commercial application of this algorithm. Full article

We report an electro-absorption modulator integrated with a distributed feedback Bragg laser fabricated by butt-joint technology. The lasing wavelength of the EML laser was 1311.71 nm, the output power was 10.04 mW when the current of the DFB section was 100 mA, the side-mode suppression ratio was greater than 50 dB, and the small-signal bandwidth was 29.40 GHz when the bias voltage of the modulator was −2 V. A 50 Gb/s data transmission over a single-mode fiber of up to 10 km was realized, which could be used as a light source for 50 G passive optical network systems. Full article

A novel AlGaInAs/InP electro-absorption modulated laser (EML) with a simple fabrication process is proposed, in which the electro-absorption modulator (EAM) has a 10 nm blueshift induced by quantum well intermixing (QWI) and is monolithically integrated with a sidewall grating distributed-feedback (DFB) laser working at 1.55 μm wavelength. The extent of the QWI process is characterized by a diffusion length. The quantum confined Stark effect (QCSE) is simulated in terms of extinction ratio (ER) and chirp for bias electric fields from 0 kV/cm to 200 kV/cm and for different amounts of intermixing. The results indicate that for a 150 µm-long EAM with a 10 nm blueshift induced by QWI, an ER of 40 dB is obtained at 2.5 V reverse bias with no penalty in chirp compared to an as-grown quantum well (QW) and the insertion loss at 0 V bias is 0.11 dB for 1.55 µm operation wavelength. The simulated –3 dB bandwidth of the electrical to optical power response is 22 GHz. Full article

Selective area epitaxy (SAE) using metal–organic chemical vapor deposition (MOCVD) is a crucial fabrication technique for lasers and photonic integrated circuits (PICs). A low-cost, reproducible, and simple process for the mass production of semiconductor lasers with specific structures was realized by means of SAE. This paper presents a review of the applications of SAE in semiconductor lasers. Growth rate enhancement and composition variation, which are two unique characteristics of SAE, are attributed to a mask. The design of the mask geometry enables the engineering of a bandgap to achieve lasing wavelength tuning. SAE allows for the reproducible and economical fabrication of buried heterojunction lasers, quantum dot lasers, and heteroepitaxial III–V compound lasers on Si. Moreover, it enables the fabrication of compact photonic integrated devices, including electro-absorption modulated lasers and multi-wavelength array lasers. Results show that SAE is an economical and reproducible method to fabricate lasers with desired structures. The goals for SAE applications in the future are to improve the performance of lasers and PICs, including reducing the defects of the grown material introduced by the SAE mask and achieving precise control of the thickness and composition. Full article

In the past, the waveguide electroabsorption effect has generally been used as an intensity modulator for quasi-monochromatic light, such as lasers. Here, we study how this effect affects polychromatic light spectra. We find that for light with a Gaussian distribution spectrum, the spectral peak shift (red shift or blue shift) can be controlled by the magnitude of the applied voltage, as long as the center wavelength and the spectral band are properly selected. This result can be used as a data transmission scheme at the integrated chip level or in free space. It may offer a good option for some other light sources, such as low-cost LED or ELED (edge emitting LED), with wider spectral bandwidths. Full article

A quad, small form-factor pluggable 28 Gbps optical transceiver design scheme is proposed. It is capable of transmitting 50 Gbps of data up to a distance of 40 km using modulation signals with a level-four pulse-amplitude. The proposed scheme is designed using a combination of electro-absorption-modulated lasers, transmitter optical sub-assembly, low-cost positive-intrinsic-native photodiodes, and receiver optical sub-assembly to achieve standard performance and low cost. Moreover, the hardware and firmware design schemes to implement the optical transceiver are presented. The results confirm the effectiveness of the proposed scheme and the performance of the manufactured optical transceiver, thereby confirming its applicability to real industrial sites. Full article

We investigated the application of a semiconductor optical amplifier (SOA) and an SOA electro-absorption modulator (SOA-EAM) as attractive, low-cost solutions in passive optical networks (PONs). The main characteristics of an SOA with optimal performance for phase and amplitude modulation were tested. Additionally, a 10 Gb/s bidirectional transmission with an optical network unit (ONU) transmitter integrated with a distributed feedback (DFB) laser, electro-absorption modulator (EAM), and SOA was designed. The upstream (US) and downstream (DS) receiver sensitivities at the forward error correction (FEC) level reached −29.5 dBm and −33.5 dBm for back-to-back (BtB) fiber and −28.9 dBm and −33.1 dBm for 20 km fiber. For multichannel transmission, the US receiver sensitivities reached −28.8 dBm and −28.2 dBm for BtB and 20 km fibers, and the DS receiver sensitivities reached −33 dBm and −32.6 dBm for BtB and 20 km fibers, respectively. Full article

We report the theoretical and experimental study of calibration-free heterodyne phase-sensitive dispersion spectroscopy (HPSDS) in the mid-infrared using a direct current modulated mid-infrared quantum cascade laser (QCL). The modulation of QCL current at several hundred MHz or higher generates the synchronous frequency and intensity modulation of the QCL emission. An analytical model of the phase of the beat note signal in HPSDS is derived by considering the absorption and dispersion processes and incorporating the QCL modulation parameters. In the experiment, a 4.5 μm QCL modulated at 350 MHz was used to measure N₂O at 200 Torr in a 10 cm gas cell. The N₂O concentrations inferred from the analytical model were compared with the nominal values to show good agreement over the concentration range of 189−805 ppm with a standard deviation <3%. When the QCL wavelength was locked at the line-center of the molecular transition, it was of interest to find that the theoretical model was simplified to that used for near-infrared HPSDS with an electro-optical modulator for laser modulation. Full article

A highly sensitive photoacoustic (PA) microcavity gas sensor for leak detection is proposed. The miniature and low-cost gas sensor mainly consisted of a micro-electro-mechanical system (MEMS) microphone and a stainless-steel capillary with two small holes opened on the side wall. Different from traditional PA sensors, the designed low-power sensor had no gas valves and pumps. Gas could diffuse into the stainless-steel PA microcavity from two holes. The volume of the cavity in the sensor was only 7.9 μL. We use a 1650.96 nm distributed feedback (DFB) laser and the second-harmonic wavelength modulation spectroscopy (2f-WMS) method to measure PA signals. The measurement result of diffused methane (CH₄) gas shows a response time of 5.8 s and a recovery time of 5.2 s. The detection limit was achieved at 1.7 ppm with a 1-s lock-in integral time. In addition, the calculated normalized noise equivalent absorption (NNEA) coefficient was 1.2 × 10⁻⁸ W·cm⁻¹·Hz^−1/2. The designed PA microcavity sensor can be used for the early warning of gas leakage. Full article

This paper describes a fabrication process for realizing Indium-Phosphide-based photonic-integrated circuits (PICs) with a high level of integration to target a wide variety of optical applications. To show the diversity in PICs achievable with our open-access foundry process, we illustrate two examples: a fully-integrated 20 Gb/s dual-polarization electro-absorption-modulated laser, and a balanced detector composed of avalanche photodiodes for detection of 28 Gb/s optical signals. On another note, datacenters are increasingly relying on hybrid integration of PICs from different technology platforms to increase transmission capacity, while simultaneously lowering cost, size, and power consumption. Several technology platforms require surface coupling rather than the traditional edge coupling to couple the light from one PIC to another. To accommodate the surface-coupling approach in our integration platform, we have developed a strategy to transfer the following optical Input/Output devices into our fabrication process: grating couplers, and vertical mirrors. In addition, we introduced etched facets into the process to improve the usability of our edge-coupling elements. We believe that the additional flexibility in Input/Output interfacing combined with the integration of multiple devices onto one PIC to reduce the number of PIC-to-PIC alignments can contribute significantly to the development of compact, low-cost, and high-performance datacenter modules. Full article

Directly modulated long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered for the implementation of sliceable bandwidth/bitrate variable transceivers for very high capacity transmission (higher than 50 Gb/s per wavelength) in metropolitan area systems characterized by reduced cost, power consumption, and footprint. The impact of the frequency chirp measured for InP VCSELs with different kinds of design (high-bandwidth very short cavity and widely-tunable with micro electro-mechanical systems (MEMS) top mirror) is analyzed in case of discrete multitone (DMT) direct modulation in combination with 25-GHz wavelength selective switch (WSS) filtering. The maximum transmitted capacity for both dual side- and single side-band DMT modulation is evaluated as a function of the number of crossed nodes in a mesh metro network, comparing VCSEL based transmitters performance also with the case of external electro-absorption modulator use. Finally, the maximum reach achieved based on the received optical signal to noise ratio (OSNR) and the fiber span length is discussed. The results confirm the possibility to use directly-modulated long-wavelength VCSELs for the realization of sliceable bandwidth/bitrate variable transmitters targeting 50-Gb/s capacity per polarization, also in the presence of 5 crossed WSSs for reaches of hundreds of kilometers in multi-span Erbium-doped fiber amplified (EDFA) metro links supported by coherent detection. Full article

This work presents pulsed laser deposition as a method to obtain unoxidized LaNi₅ nanoscale films and describes their temperature and thickness dependent electrical conductivity and the spectral dispersions of some optical properties. AB₅-type rare earth element (REE)-nickel compounds are currently studied from both theoretical and practical points of view. Special challenges are posed during the preparation of these nanomaterials, which can be overcome using finely tuned parameters in a preparation process that always involves the use of high energies. Film deposition was made by laser—induced vaporization, with short and modulated impulses and electro–optical tuning of the quality factor, mainly on glass and one SiO₂ substrate. Deposition geometry dependent linear thickness increase, between 1.5–2.5 nm per laser burst, was achieved. Film structures and phase compositions were determined using XRD and discussed in comparison with films obtained by similar deposition procedures. Temperature and scale dependent properties were determined by studying electrical conductivity and optical properties. Electrical conductivity was measured using the four-probe method. The observed semiconductor-like conductivity for film thicknesses up to 110 nm can be explained by thermal activation of electrons followed by inter-insular hopping or quantum tunneling, which, on the other hand, modulates the material’s native metallic conductance. Films with thicknesses above this value can be considered essentially metallic and bulk-like. The spectral behaviors of the refractive index and absorption coefficient were deduced from differential reflectance spectroscopy data acquired on a broad ultraviolet, visible, near- and mid-infrared (UV-VIS-NIR-MIR) domain, processed using the Kramers-Krönig formalism. Their study led to the identification of the allowed interband transitions. Electronic behavior in the energy bands near the Fermi level and in the surface and interface-states was described, discussing the differences between experimental data and the classical free-electron theoretical model applied for the bulk intermetallic alloy, in correlation with theoretical optical properties or experimental X-ray photoelectron spectroscopy (XPS) results from references. However, the dielectric-like shape of the reflectance of the thinnest film was in accordance with the Lorentz–Drude model. Full article

We experimentally investigate the transmission performance of 56 Gb/s four-level pulse amplitude modulation (PAM-4) over 30-km standard single mode fiber (SMF) using a C-band EML for low-cost metro and short-reach wavelength division multiplexing (WDM) applications. Bit error rate (BER) performance below the HD-FEC threshold is achieved for up to 30-km maximum reported distance without employing dispersion compensation fiber (DCF) in the link. Full article