Search Results (678)

This paper presents the design and fabrication of a 1.65 μm tapered semiconductor laser based on an InGaAlAs multiple quantum well structure (grown) on InP. Through theoretical modeling and parametric optimization simulations, it was established that an etching depth of 0.8 μm for the ridge waveguide and a taper angle of 6° effectively confine the optical field and suppress high-order mode lasing. Based on these optimized parameters, a tapered semiconductor laser with a ridge width of 2 μm and a cavity length of 2000 μm was successfully fabricated. Systematic characterization was conducted under continuous-wave operation at 25 °C. The device exhibits outstanding overall performance: a maximum continuous-wave output power of 19.3 mW, a peak wavelength of 1653 nm, a spectral line width of 0.793 nm, and a side-mode suppression ratio (SMSR) as high as 49 dB, demonstrating excellent spectral purity. Far-field measurements further reveal that at an injection current of 30 mA, the vertical and horizontal far-field divergence angles are 41.02° and 15.26°, respectively, with a well-defined Gaussian beam profile. This study provides an effective technical approach for the design and fabrication of high-performance semiconductor lasers in the 1.65 μm band. The developed device shows significant potential for applications in free-space optical communication, LiDAR, and gas sensing. Full article

We demonstrate an integrated core-pumped 4-core erbium-doped fiber amplifier (4C-EDFA) that achieves a record-low differential core gain of 0.5 dB across the whole C-band. This is enabled by utilizing a 4C-EDF with a minimal core-dependent absorption coefficient and passive devices with low core-dependent loss. The 4C-EDFA also exhibits an average gain of 15.50 dB, an average output power of 22.5 dBm, and a maximum noise figure of 4.91 dB. Furthermore, simulations on a 4-core fiber (4CF) transmission link confirm that the proposed 4C-EDFA can support transmission exceeding 10,000 km with a minimal inter-core Q² difference of only 0.5 dB. Here, Q² is defined as the ratio of the mean received signal levels to the corresponding noise variances. It is a critical metric in optical systems to quantify the signal quality, which highlights its potential for high-capacity and long-haul uncoupled 4CF systems. Full article

With the rapid deployment of artificial intelligence (AI) data centers, demand for optical modules surges—alongside faster upgrades and stricter low-power requirements. However, traditional optical driver integrated circuits (ICs) rely on device-specific customization, which lengthens driver design cycles, delays module deployment, and raises costs, becoming a bottleneck for optical module evolution. To address these issues, this work proposes a unified optical transmitter electronic integrated circuit (EIC) design approach featuring synergistic driver-laser/modulator co-design and a versatile output driver (VOD). The VOD can be configured into three output impedance states (open-drain, differential 50-$\Omega$, or differential 100-$\Omega$), enabling it to drive various optical devices like distributed feedback lasers (DFBs), vertical-cavity surface-emitting lasers (VCSELs), electro-absorption modulated lasers (EMLs), and Mach-Zehnder modulators (MZMs) with a single design, minimizing device-specific customization. Meanwhile, its power consumption is also adjustable to maximize the power efficiency. The proposed design approach demonstrates the potential to address the critical interoperability, cost, and power challenges faced by AI data centers, providing a scalable template for next-generation coherent and 4-level pulse amplitude modulation systems and facilitating rapid deployment. Full article

Aiming to address the insulation and power supply challenges faced by electrical measurement in ultra-high voltage (UHV) environments, this study proposes and implements a nitrogen-vacancy (NV) center magnetic sensing system based on Power over Fiber (PoF) technology. The system adopts a high-voltage and low-voltage separation design, realizing the isolated transmission of electrical energy and the reliable recovery of measurement signals through an optical fiber link. The sensing unit on the high-voltage side is composed of NV center sensors, microwave excitation modules, and signal processing modules. Its power supply is provided by an independently developed high-power laser power converter (LPC) assembly via 830 nm optical fiber laser transmission. Under an optical input of 10 W, this assembly can achieve an electrical output of 4.88 W with a conversion efficiency of 48.9%. The experimental results show that the system can operate stably in a simulated UHV environment; by optimizing modulation parameters, the optimal magnetic measurement sensitivity reaches 6.1 nT/Hz^1/2. This research provides a safe and reliable solution for the power supply and precise sensing of high-potential side equipment in UHV scenarios, and demonstrates the application potential of PoF technology in advanced sensing for power systems. Full article

Ytterbium-doped femtosecond fiber lasers are widely used in scientific research, industrial processing, and other fields due to their high quantum efficiency, wide gain bandwidth, and compact structure. This article addresses the problems of low processing efficiency and difficulty in increasing the average power of femtosecond lasers. A high repetition rate fiber chirped pulse amplification system is built, which uses a high repetition rate Figure-9 fiber laser as the seed source and an acousto-optic modulator (AOM) to shape the dense pulse train in the time domain. The main amplification stage uses a large mode field ytterbium-doped fiber to achieve full fiberization of the amplification system, and a volume grating (VBG) is selected as the pulse compressor to make the laser system highly integrated. When the repetition rate is 67.5 MHz, the compressed output laser has an average power of 20.5 W, a pulse width of 447 fs, a pulse train energy of 750 μJ, a spot ellipticity of 0.96, and a beam quality M² better than 1.4 ($M_x^2=1.33$, $M_y^2=1.16$). Full article

A high-power single-frequency continuous-wave wideband continuously tunable dual-wavelength laser at 1064/532 nm is presented in this paper. Firstly, a thermally insensitive cavity containing a type-I phase-matching LiB₃O₅ crystal and an uncoated quartz etalon was specially designed, which provided the fundamental condition for the generation of a high-power single-frequency 1064 nm and 532 nm laser. By carefully optimizing the mode matching, the maximal output powers of 13.3 W at 1064 nm and 12.5 W at 532 nm were achieved when the pump power was 63.7 W, and the total optical–optical efficiency of 40.5% was achieved. After the transmission peak of etalon was locked to the oscillating frequency of the resonator, the continuous frequency tuning ranges of the achieved laser were as wide as 26.75 GHz at 1064 nm and 53.5 GHz at 532 nm. Full article

Leveraging our developed Global–Local Integrated Topology inverse design algorithm, we designed an efficient, compact, and symmetrical power splitter on a silicon-on-insulator platform. This device achieves a low insertion loss of 0.18 dB and a power imbalance of <0.0002 dB between its output ports within an ultra-compact footprint of 5.5 µm × 2.5 µm. The splitter, combined with an ultra-compact 0–π phase shifter measuring only 4.5 µm × 0.9 µm on the silicon-on-insulator platform, forms an ultra-compact inverse-designed integrated photonic matrix compute core, thus enabling the function of matrix operations in optical neural networks. Through a networked cascade of power splitters and phase shifters, this silicon-based photonic matrix compute core achieves an integration density of ~26,000 computational units/mm². Moreover, it attained 99.05% accuracy in handwritten digit recognition (0–9) and exhibited strong robustness against fabrication errors, maintaining >80% accuracy with >0.9 probability under simulated random fabrication errors. Full article

We demonstrate a dual-wavelength broad-area diode laser system with narrow linewidth and wide spectral tunability using a composite external cavity comprising a volume Bragg grating and a Littrow-type transmission grating. One wavelength is stabilized at 780.25 nm with a linewidth of ~0.13 nm, while the other achieves a continuous tuning range of 772.24–786.43 nm with a linewidth of ~0.17 nm. The system exhibits a side-mode suppression ratio exceeding 20 dB across the entire tuning range. At a dual-wavelength separation of 4.29 nm, the total output power reaches 2.62 W. Additionally, we successfully validate the system’s potential for nonlinear optical applications. Full article

In this research, precision temperature sensing for electromagnetically harsh environments was achieved utilizing a low-threshold frequency-stable optoelectronic oscillator (OEO) leveraging stimulated Brillouin scattering (SBS). The sensing mechanism relied on the temperature-dependent frequency shift in the SBS-induced notch filter. By embedding this filter in the OEO feedback loop, the oscillator’s output frequency was locked to the difference between the optical carrier frequency and the SBS notch center frequency. The temperature variations were translated into microwave frequency shifts through OEO oscillation, which was quantified with heterodyne detection. To suppress environmental perturbations, a Faraday rotation mirror (FRM) was integrated at the fiber end, creating a dual-pass SBS interaction that simultaneously enhanced the vibration immunity and reduced the SBS power threshold by 2.7 dB. The experimental results demonstrated a sensitivity of 1.0609 MHz/°C (R² = 0.999) and a long-term stability of ±0.004 °C. This innovative scheme demonstrated significant advantages over conventional SBS-OEO temperature sensing approaches, particularly in terms of threshold reduction and environmental stability enhancement. Full article

With the global energy transition and decarbonization goals, tower-type solar thermal power generation is increasingly important for dispatchable clean energy due to its high efficiency, thermal storage capacity, and regulation performance. However, current research focuses on ideal conditions, ignoring real geographical constraints on heliostat layout and environmental impacts on receiver performance. More practical scene modeling and performance evaluation methods are urgently needed. To address these issues, we propose a heliostat field simulation algorithm based on heat loss mechanisms and real site characteristics. The algorithm includes optical performance evaluation (cosine efficiency, shading, truncation, atmospheric transmittance) and heat loss mechanisms (radiation, convection, conduction) for realistic net heat output estimation. Experiments revealed the following: (1) higher central towers improve optical efficiency by increasing solar elevation angle; (2) radiation losses dominate at high power and tower height, while convection losses dominate at low power and tower height. Using the Economic-Integrated Score (EIS) optimization algorithm, we achieved optimal tower and receiver configuration with 40.22% average improvement over other configurations (maximum 3.9× improvement). This provides a scientific design basis for improving tower-type solar thermal systems’ adaptability and economy in different geographical environments. Full article

In laser wireless power transmission systems, the powersphere serves as a spherical enclosed receiver that performs photoelectric conversion, achieving uniform light distribution within the cavity through infinite internal light reflection. However, in practical applications, the high level of light absorption displayed by photovoltaic cells leads to significant disparities in light intensity between directly irradiated regions and reflected regions on the inner surface of the powersphere, resulting in poor light uniformity. One approach aimed at addressing this issue uses a spectroscope to split the incident beam into multiple paths, allowing the direct illumination of all inner surfaces of the powersphere and reducing the light intensity difference between direct and reflected regions. However, experimental results indicate that light transmission through lenses introduces power losses, leading to improved uniformity but reduced output power. To address this limitation, this study proposes a method that utilizes multiple incident laser beams combined with a centrally positioned spherical reflector within the powersphere. A wireless power transmission system model was developed using optical simulation software, and the uniformity of the intracavity light field in the system was analyzed through simulation. To validate the design and simulation accuracy, an experimental system incorporating semiconductor lasers, spherical mirrors, and a powersphere was constructed. The data from the experiments aligned with the simulation results, jointly confirming that integrating a spherical reflector and distributed incident lasers enhances the uniformity of the internal light field within the powersphere and improves the system’s efficiency. Full article

A solar-pumped Ce:Nd:YAG laser amplifier design is proposed to address the challenge of scaling output power in solar-pumped laser oscillators while maintaining high beam quality. The design employs a 1.33 m² flat Fresnel lens with a 2 m focal length as a primary concentrator, which is combined with a secondary homogenizing concentrator, featuring 40 mm × 40 mm input aperture, 200 mm length, and 11.3 mm × 26 mm output aperture, to provide efficient coupling and uniform distribution of solar radiation onto a 2.9 mm thick Ce:Nd:YAG slab with 11.3 mm × 26 mm surface area and two beveled corners. This geometry enables multiple total internal reflections of a 1064 nm TEM₀₀ mode seed laser beam inside the slab, ensuring efficient interaction with the active Ce³⁺ and Nd³⁺ ions in the gain medium. Performed numerical analysis shows that the present approach can deliver a uniform solar pump power density of 2.5 W/mm² to the slab amplifier. This value is 2.05-times higher than the numerically calculated power density incident on the Nd:YAG slab of the previous solar-pumped amplifier that achieved the highest continuous-wave laser gain of 1.64. Furthermore, the optimized slab geometry with 0.44 width-to-height ratio allows the seed laser to undergo 32 internal reflections, extending its optical path length by a factor of 1.45 compared to the earlier design. These numerical achievements, combined with the Ce:Nd:YAG medium’s capacity to deliver nearly 1.57-times more laser power than Nd:YAG, reveal the potential of proposed design to yield a gain enhancement factor of 4.16, making the first solar-pumped Ce:Nd:YAG amplifier a promising solution toward energy-efficient, sustainable solutions for terrestrial and space applications. Full article

The development of reconfigurable photonic integrated circuits (PICs) demands photonic devices with high-efficiency tuning capabilities, yet conventional thermo-optic and electro-optic methods suffer from limited index modulation and excessive power consumption. To overcome these limitations, we propose an etchless and tunable silicon nitride waveguide mode converter based on low-loss phase change material, antimony triselenide (Sb₂Se₃). By depositing an Sb₂Se₃ layer on the silicon nitride wafer and using a laser-induced phase transition technique, we can write and erase the waveguide structure in the phase change wafer without waveguide etching, where the input/output waveguide is a strip waveguide and the conversion region is built using a tilted subwavelength grating structure. From the results, the obtained TE₀-TE₁ mode conversion efficiency, crosstalk, and insertion loss are higher than 96%, lower than −16 dB, and lower than 0.4 dB at a wavelength of 1.55 µm, respectively. The proposed device enables post-fabrication tuning of the grating duty cycle, allowing working wavelength adjustment for the same device. Furthermore, the device exhibits scalability to other higher-order mode conversions (e.g., TE₀-TE₂). Consequently, we expect that such devices could have important uses in programmable and multifunctional PICs. Full article

The combination of polypyrrole (PPy) with graphene has attracted extensive attention as a nonlinear optical material with various optoelectronic applications. Here, we describe the development of PPy nanoplates prepared using a simple spin-coating method. The appropriate volume of the dropped PPy solution was determined to be 50 drops by comparing the surface morphologies, chain structures, elementary compositions, and optical properties of PPy saturable absorbers (SAs). The hybrid PPy/graphene heterostructure SA was obtained using the wet transfer process of a graphene layer. This approach led to significant improvements in optical properties, including a ~7.2% increase in linear optical absorption, a 2.5-fold increase in modulation depth, and a third decrease in saturable intensity at 1550 nm due to the additional optical absorption and the π-π interaction between PPy nanoplates and the graphene layer. By inserting the PPy/graphene heterostructure SA into the passively mode-locked fiber laser cavity, 1559 nm ultrashort laser pulses were generated, with an average output power of 1.24 mW, a 815 fs pulse width, and a repetition frequency of 3.26 MHz. Our experimental results demonstrate that the prepared PPy SA has excellent nonlinear optical characteristics, providing a new opportunity for the generation of ultrashort laser pulses. Full article

High-order linear polarization (LP) modes and vortex beams carrying orbital angular momentum (OAM) are highly useful in various fields. High-order LP modes provide higher thresholds for nonlinear effects, reduced sensitivity to distortions, and better energy extraction in high-power lasers. OAM beams are useful in optical communication, imaging, particle manipulation, and fiber sensing. The ability to switch between these mode outputs enhances system versatility and adaptability, supporting advanced applications both in research and industry. This paper presents the design of a 19 × 1 photonic lantern capable of outputting 19 LP modes and 16 OAM modes with low loss. Using the beam propagation method, we simulated and analyzed the mode evolution process and insertion loss, and we calculated the transmission matrix of the photonic lantern. The results indicate that the designed device can efficiently evolve into these modes with a maximum insertion loss not exceeding 0.07 dB. Furthermore, an adaptive control system was developed by introducing a mode decomposition system at the output and combining it with the Stochastic Parallel Gradient Descent (SPGD) + basin hopping algorithm. Simulation results show that this system can produce desired modes with over 90% mode content, demonstrating promising application prospects in switchable high-order mode systems. Full article