In this paper, we demonstrate a 12.5 Gbit/s directly modulated InAs/GaAs quantum dot (QD) lasers epitaxially grown on Si (001) substrate with strong optical feedback resistance. The active region of the QD laser consists of p-modulation-doped eight-layer QDs. It is shown that the QD laser with a ridge waveguide structure of 3×600 µm 2 can operate in continuous-wave (CW) mode from 25°C to 75°C, with a maximum output power of 16.9 mW at room temperature (RT). Furthermore, small-signal measurements reveal that the laser has a 3 dB bandwidth of 3.8 GHz and 2.7 GHz at 25°C and 55°C, respectively. Non-return-to-zero (NRZ) large signal measurements reveal that the laser can achieve a maximum modulation rate of 12.5 Gbit/s at RT. Dynamic optical feedback measurements using a 10 Gbit/s signal exhibit that the QD laser has a strong optical feedback tolerance, leading to a low bit error ratio (BER) of 6×10 –6 even at a maximum feedback intensity of −9 dB. These results presented here prove the great application potential of the QD lasers on Si (001) for large scale, low-cost and isolator-free silicon photonics integrated circuits (PICs).

We demonstrate a thermally stable, high-power InAs/GaAs quantum dot (QD) four-channel distributed feedback (DFB) laser array featuring ultra-narrow linewidth and low noise. Each channel of the array delivers continuous-wave output powers exceeding 34 mW and 17 mW at 25°C and 85°C, respectively, with side-mode suppression ratios >45 dB. Furthermore, the device exhibits an ultra-narrow linewidth as low as 1.60 kHz and low relative intensity noise (RIN), with peak RIN values below -165 dB/Hz. The results presented here prove the great potential of QD DFB laser arrays for energy-efficient and cost-effective wavelength-division multiplexing (WDM) data transmission systems in uncooled operation scenarios.

We demonstrate a thermally stable, high-power InAs /GaAs quantum dot (QD) four-channel distributed feedback (DFB) laser array featuring an ultra-narrow linewidth and low noise. Each channel of the array delivers a continuous-wave output power exceeding 34 mW and 17 mW at 25 degrees C and 85 degrees C, respectively, with side-mode suppression ratios >45 dB. Furthermore, the device exhibits an ultra-narrow linewidth as low as 1.60 kHz and low relative intensity noise (RIN), with peak RIN values below 165 dB/Hz at 50 degrees C. These results demonstrate the potential of QD DFB laser arrays for energye fficient and cost-e ffective wavelength-division multiplexing data transmission systems in uncooled operation scenarios.

A numerical calculation model of the narrow ridge waveguide was established based on the effective refrac-tive index method.The relationship between the polarization characteristics and the transverse mode of the InGaAs quantum well narrow ridge waveguide semiconductor laser was studied experimentally.According to theoretical calcula-tions,the effective refractive index difference of the TM-like mode in the ridge waveguide is larger in the direction of the slow axis.The confinement factors of the TM-like mode are larger than those of the TE-like mode,and the slow-ax-is high-order mode is more likely to appear.As the height of the ridge waveguide increases,the fast-axis high-order modes are truncated,and the confinement factor of the TE00-like mode gradually increases to be similar to that of the TM00-like mode.The slow-axis high-order mode is suppressed due to its large scattering loss,theoretically achieving high polarization,and near diffraction limit beam-quality laser output.In terms of experiments,a narrow ridge wave-guide semiconductor laser with a high polarization extinction ratio and a fundamental transverse mode was fabricated by the gain polarization characteristics of quantum well materials and by designing the height and width of the ridge.

Lithium -rich manganese -based cathode (LRM) materials are considered the most promising cathode for the nextgeneration high -energy -density Li -ion batteries due to their high specific discharge capacity. However, the current mainstream LRM materials exhibit a polycrystalline morphology, and the degradation of this morphology during extended cycling exacerbates structural distortions, leading to poor cycle stability. Herein, a spinel phase encapsulated single -crystal LRM material with a particle size of about 500 nm is prepared through a simple molten -salt assistant solid-state synthesis method utilizing traditional polycrystalline LRM precursor, followed by boric acid treatment. Combined with various characterizations, the surface coating layer of obtained singlecrystal LRM materials is identified as spinel Li4Mn5O12 with a thickness of about 5 nm, which effectively enhances Li+ diffusion kinetics. Benefited from the collaborative strategy of single crystallization and spinel coating which strength Li+ conduction and suppresses particle cracking, the single -crystal LRM materials achieve a specific discharge capacity of 296.3 mAh g-1 at 0.1 C (1 C = 250 mA g-1), yielding a capacity retention of 97.4% after 300 cycles at 1 C. This study offers a universal and easy industrial scale -up approach for developing singlecrystal LRM cathode materials with long cycling stability, which promotes the commercial utilization of singlecrystal LRM cathode.

In this paper, the tunable narrow spectral semiconductor laser technology based on on-chip DBR gratings is investigated. The surface DBR grating structure and electro-thermal tuning structure were designed, determined key parameters of grating structural, and the problem of multi-peak suppression was studied. Developed manufacturing technology for surface DBR gratings and tunable technology based on micro-electrode heaters and applied them to tapered MOPA laser chips, achieving output laser spectral locking while maintaining the high brightness of tapered semiconductor lasers. The tapered MOPA laser has achieved a narrow spectral width of 40 pm and a side mode suppression ratio of 35 dB under a continuous-wave power of 10.3 W. At a microelectrode heater current of 0.22 A, the wavelength can be continuously tuned over a range of 4.3 nm, with a maximum spectral width not exceeding 60 pm.

High brightness, high power tapered diode-laser regularly consists of an index-guided ridge-waveguide section and a gain-guide tapered section. The gain match between the ridge and tapered sections were studied in this paper. The gain peak wavelength of the ridge section is expected to be larger than that in the tapered section because of the higher optical power density by numerical simulation. It is found that the gain peak mismatch between the ridge and tapered sections results in broadened optical spectra and low output powers according to the experimental results. The mismatch is suppressed by lowering the junction temperature of the ridge section which shifts the gain peak of the ridge section to a shorter wavelength. Alternatively, the shift of the gain spectra was also realized by increasing the transparency carrier density with an additional optical loss in the ridge waveguide introduced by He + ion implantation. Tapered diode lasers with such designs have a beam quality factor M2 (1/e2) = 1.1 with an output power of 8 W and a narrow spectra width of 2 nm.

High-power semiconductor laser with nearly diffraction limited narrow band emission was designed and fabricated. The monolithic master oscillator power-amplifier(MOPA)diode laser consists of distributed Bragg gratings,a narrow ridge waveguide and a tapered amplifier. The ridge waveguide with length of 8 mm and width of 3 mu m is used as the single-mode seed source. A tapered gain section with length of 7 mm and a full taper angle of 3.3 degrees amplify the seed power. The fabricated device reach an output power of 10.3 W with a slow axis beam quality M-2(1/e(2))factor of 1. 06 and an electro-optic efficiency of 50.5%. The spectral linewidth is 40 pm(3 dB),and a central wavelength tuning range of 4 nm was realized by the integrated Bragg gratings micro heater.

satisfy the need of Thulium-doped fiber laser pump source,793 nm high-power semiconductor laser emit-ters and fiber-coupled module were developed. The laser epitaxy adopts the large asymmetric optical cavity waveguide structure to reduce the mode loss. The waveguide adopts aluminum free GaInP material which improves the facet dam-aged threshold combined with vacuum cleavage passivation process. Through the optimization of epitaxial structure and facet coating,the output power of the developed laser reaches 12 W@11A,passed the 300 h aging test of 8 W. Seven single emitters were space coupled to 100 mu m 0. 22 NA fiber modules. The output power of the model is 40 W@7A, and the electro-optical efficiency is 49. 5% @ 40 W.

The considerations in the epitaxial and longitudinal design of a supper-large-optical-cavity structure di. ode laser in the 976-nm band are numerically studied and presented here. Mode control layers were designed un. derneath and up the quantum well layer to suppress the lasing of high-order transverse modes. The electron leak. age was suppressed by a band energy engineering,where the electron barrier increases from the p-waveguide layer to the p-cladding layer. The optimized structure has an internal loss of 0. 66 cm(-1),an internal quantum efficiency of 0. 954,and a full width at half maximum vertical far-field angle of 17. 4 degrees. For the resonant cavity design,a lin. er current profile along the cavity was proposed to reduce the longitudinal spatial hole burning effect,where a power penalty of 1. 0 W at 20 A is suppressed. The 4-mm-long and 100 mu m wide broad-area single emitter with the supper-large-optical-cavity epitaxial structure was designed to have a high power-efficiency of about 71% at an output power of 21 W under continuous current injection at 25 degrees C.

High-brightness tapered diode lasers generally work in the fundamental transverse mode. Still, under the condition of high power, the beam quality is often deteriorated by the influence of higher-order modes. At the junction of the device ridge waveguide and the conical amplifier, there is a great difference in the refractive index step.n, which is the key area for producing high-order modes and influencing each other. In this paper, the physical process of high-order side mode excitation in a large optical cavity InGaAs/AlGaAs conical LD was studied. The mode changes of the propagation interface were simulated by the eigenmode expansion method (EME). The effects of various separation distances of the beam spoilers were compared and verified by experiments. The results show that through the practical design of the separation distance of beam spoilers at the mode propagation interface, the tapered LD can maintain the high beam quality of M-2=1.9 at 3.2 W.

Abstract Aiming at the rapid development of the power transmission industry, with the huge number of iron towers and the large amount of tower material quality inspection work, however, the detection efficiency is low. This article analyzed five inspection items, inspection points, and their inspection data volume, which are required for tower material specification inspection, such as parts, galvanized layer, that must be performed in the tower material specification inspection, put forward the plan of tower material quality inspection system integrated by software management system and hardware detection instrument, and designed the system scheme, determined the typical testing equipment with real-time transmission function, and designed the architecture of tower material quality information management system. This system can realize the intelligentization of tower material testing, the digitization of the testing process, and the standardization of testing information management, greatly improving the efficiency and accuracy of tower material quality testing.

We analyze and experimentally verify the impact of facet reflectivity on slope efficiency and output power of 150-nm GaN-based semiconductor lasers. The results reveal that for asymmetric resonator structures, the nonlinear effect of longitude spatial hole burning can be suppressed by optimizing the facet reflectivity, thereby improving the differential quantum efficiency and maximum output power of the device. A high slope efficiency of >1.3 W . A(-1) is obtained at the facet reflectivity of 5%, and a high power output of 2. 6 W is obtained at the operating current of 3 A.

In this research, the transversal mode of 970 nm broad area laser diode based on a large optical cavity is studied. The vertical far-field patterns were measured to be dependent on the cavity caused facet loss. High-orders modes achieve lasing with higher facet loss while they can be completely suppressed by a low facet loss. The suppression of high-order modes was attributed to be an increase in the discrimination of differential quantum efficiency between high-order modes and the fundamental mode, which matches well with simulation. When the discrimination exceeds probable fluctuations, the high-order modes will be completely suppressed and lasing of single fundamental mode will achieve. According to our experiment results, the optimal resonance cavity length is about 6 mm in order to realize fundamental mode and simultaneously a high slope efficiency. As a consequence, high efficiency 970 nm broad area laser with slope efficiency over 1.07 W/A and full wavelength half maximum (FWHM) less than 2 nm@1A is demonstrated.

High-power high-efficiency broad-area diode lasers are highly efficient light sources. A study on the design of large-optical-cavity 976-nm diode lasers is presented here. Efforts were made to suppress the higher-order modes and to explore new design methods for high-power high-efficiency diode lasers. The mode distribution, confinement factor, internal optical loss and far-field pattern were numerically calculated to analyze the waveguide design. To suppress the higher order transverse modes, both gain and loss discrimination mechanisms were experimentally investigated. By adjusting the position of the active region, successful suppression of higher-order modes can be achieved. Alternatively, higher-order modes can be suppressed by increasing the cavity length, which is attributed to the discrimination of modal loss between the higher-order modes and the fundamental mode. A high-efficiency 4-mm-long broad-area single emitter with an ultralow internal optical loss of 0.27 cm-1 and an internal quantum efficiency of 93.5% was designed and fabricated. A high slope efficiency of 1.1 W/A and > 66% wall-plug efficiency was obtained at 25 degrees C under continuous current injection. The far-field divergence angles with 95% power content were 38 degrees and 9.7 degrees for the fast and slow axes, respectively, at an output power of 10.0 W.

High brightness broad area lasers with high polarization purity are highly efficient light sources for high brightness fiber coupled and direct semiconductor lasers. Effect of lateral index step on the performance of high-power broad-area 970-nm diode lasers based a large-optical-cavity waveguide structure was studied and presented here. The index step of the 80-μm wide ridge is found a key parameter to control the output power, lateral far-field angle, beam waist and polarization purity. The threshold current decreases with the increase of the etching depth while the slope efficiency increases. When gain guide lateral waveguide by very shallow etching was used, the beam waist expands to a size of more than 200 μm, which was attributed to anti-guiding effect and current spreading. When large index step is introduced by deep etching, enhanced filamentation was observed, which is attributed to an enhanced confinement of the higher order modes. What’s more, the strain introduced by the etching of the ridge can deteriorate the polarization purity. The study in this paper shows that the lateral index step should be optimized to fabricate high brightness high efficiency broad area lasers with high polarization purity.

Color centers in silicon carbide have recently attracted broad interest as high bright single photon sources and defect spins with long coherence time at room temperature. There have been several methods to generate silicon vacancy defects with excellent spin properties in silicon carbide, such as electron irradiation and ion implantation. However, little is known about the depth distribution and nanoscale depth control of the shallow defects. Here, a method is presented to precisely control the depths of the ion implantation induced shallow silicon vacancy defects in silicon carbide by using reactive ion etching with little surface damage. After optimizing the major etching parameters, a slow and stable etching rate of about 5.5 ± 0.5 nm min-1 can be obtained. By successive nanoscale plasma etching, the shallow defects are brought close to the surface step by step. The photoluminescence spectrum and optically detected magnetic resonance spectra are measured, which confirm that there were no plasma-induced optical and spin property changes of the defects. By tracing the mean counts of the remaining defects after each etching process, the depth distribution of the defects can be obtained for various implantation conditions. Moreover, the spin coherence time T2* of the generated VSi defects is detected at different etch depths, which greatly decreases when the depth is less than 25 nm. The method of nanoscale depth control of silicon vacancies would pave the way for investigating the surface spin properties and the applications in nanoscale sensing and quantum photonics.

In this research, an InGaN/GaN nanotube-based photoanode has been fabricated by nano-imprint lithography and a secondary sputtering process. The involvement of a Au nano-ring mask allowed dry etching with a high aspect ratio on the InGaN/GaN substrate. After device fabrication, the measured optical spectrum showed this innovative structure provided low reflectance and high absorbance at the wavelength around the ultraviolet range. The photoelectrochemical properties indicated optimized tube height could efficiently enhance the water splitting efficiency by 15 times at 1.23 V versus RHE by increasing the surface reactive area and tuning the optical spectrum properties. The IPCE result also demonstrated a corresponding enhancement. (C) 2019 The Japan Society of Applied Physics

In this research, the transversal mode of 970 nm broad area laser diode based on a large optical cavity is studied. The vertical far-field patterns were measured to be dependent on the cavity caused facet loss. High-orders modes achieve lasing with higher facet loss while they can be completely suppressed by a low facet loss. The suppression of high-order modes was attributed to be an increase in the discrimination of differential quantum efficiency between high-order modes and the fundamental mode, which matches well with simulation. When the discrimination exceeds probable fluctuations, the high-order modes will be completely suppressed and lasing of single fundamental mode will achieve. According to our experiment results, the optimal resonance cavity length is about 6 mm in order to realize fundamental mode and simultaneously a high slope efficiency. As a consequence, high efficiency 970 nm broad area laser with slope efficiency over 1.07 W/A and full wavelength half maximum (FWHM) less than 2 nm@lA is demonstrated.