Stripe Width Research Articles

Impact of modal gain and waveguide design on two-state lasing in quantum well-dot lasers.

We study the current-controlled lasing switching from the ground state (GS) to the excited state (ES) transition in broad-area (stripe width 100 µm) InGaAs/GaAs quantum well-dot (QWD) and quantum well (QW) lasers. In the lasers with one QWD layer and a 0.45 µm-thick GaAs waveguide, pure GS lasing takes place up to an injection current as high as 8 A (40 kA/cm2). In contrast, in QW lasers with a similar design, ES lasing emerges already at 3 A (15 kA/cm2). The ES lasing in the QWD lasers is observed only in the devices with a waveguide thickness of 0.78 µm that supports a 2nd order transverse mode at the wavelength of the ES transition. Increasing the modal gain in the lasers with 0.78 µm-thick waveguide by using two QWD layers in the active region suppresses the ES lasing.

Glass Surface Nanostructuring by Soft Lithography and Chemical Etching.

Due to its high durability and transparency, soda lime glass holds a huge potential for several applications such as photovoltaics, optical instrumentation and biomedical devices, among others. The different technologies request specific properties, which can be enhanced through the modification of the surface morphology with a nanopattern. Here, we report a simple method to nanostructure a glass surface with soft lithography and wet-chemical etching in potassium hydroxide (KOH) solutions. Glass samples etched with a polymeric mask showed a nanopattern with stripes of widths between 220 and 450 nm and modulated heights between 50 and 200 nm. For different solution concentrations or etching times, the obtained nanopatterns led to an increase or reduction of the water contact angle. The largest increment, ~20 degrees, was achieved by etching the glass for 180 min with 30% KOH concentration, while a super-hydrophilic glass (~9° contact angle) was achieved when etching for 90 min with the same concentration. Optical characterization showed a very low influence of the nanostructured pattern on glass transparency and an increment in UV transmittance for some cases.

Deformation localisation in stretched liquid crystal elastomers

We model within the framework of finite elasticity two inherent instabilities observed in liquid crystal elastomers under uniaxial tension. First is necking, which occurs when a material sample suddenly elongates more in a small region where it appears narrower than the rest of the sample. Second is shear striping, which forms when the in-plane director rotates gradually to realign and become parallel with the applied force. These phenomena are due to the liquid crystal molecules rotating freely under mechanical loads. To capture necking, we assume that the uniaxial order parameter increases with tensile stretch, as reported experimentally during polydomain-monodomain transition. To account for shear striping, we maintain the uniaxial order parameter fixed, as suggested by experiments. Our finite element simulations capture well these phenomena. As necking in liquid crystal elastomers has not been satisfactorily modelled before, our theoretical and numerical findings related to this effect can be of wide interest. Shear striping has been well studied, yet our computed examples also show how optimal stripe width increases with the nematic penetration depth measuring the competition between the Frank elasticity of liquid crystals and polymer elasticity. Although known theoretically, this result has not been confirmed numerically by previous nonlinear elastic models.

Observations of ionospheric irregularities during a geomagnetic storm based on the C-band sentinel-1

ABSTRACT Disturbances in the ionosphere can severely affect synthetic aperture radar (SAR) acquisition and also the accuracy of differential SAR interferometry (D-InSAR) techniques. Focusing on the mid-latitudes, we report for the first time the effect of small-scale ionospheric irregularities on the interferograms generated by the C-band Sentinel-1 satellite. The interferograms obtained during the geomagnetic storm on 4 November 2021 showed finger-like stripes of phase artefacts, while the interferograms obtained on non-storm days did not show such anomalies. Such phase artefacts introduce an error greater than ± 3π in the interferogram. By further checking the gridded total electron content (TEC) from the ground-based global navigation satellite system (GNSS) network, as well as the in-situ electron density measured by ESA’s Swarm satellite, the finger-like stripes in the interferograms are found to be correlated with ionospheric bulge structures generated during the geomagnetic storm. Since both the interferogram stripes and the ionospheric bulges exhibit a comparable east-west extension, it is believed that the interferograms can also be used to reflect the small-scale structures of ionospheric bulge fringes. For example, in this case, the latitudinal width of each finger-like stripe reaches about 8 km. Our result implies that the C-band interferogram has the potential to probe the two-dimensional ionospheric structures with unprecedented resolution, which cannot be achievable by the gridded GNSS-TEC.

ИССЛЕДОВАНИЕ ПАРАМЕТРОВ ПОСТОЯННОЙ ТЕХНОЛОГИЧЕСКОЙ КОЛЕИ, ПРЕДНАЗНЧЕННОЙ ДЛЯ УХОДА ЗА ПОСЕВАМИ СЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР В ЦЕНТРАЛЬНОМ ЧЕРНОЗЕМЬЕ

A study of the parameters of the created and formed permanent tramline intended for the passage of agricultural machinery when caring for crops in the Central Black Earth Region has been completed. It has been established that the width of the lanes used for the passage of agricultural machinery propulsion depends on the type of crops cultivated and the sprayers used, as well as on the location of the tramline on the agricultural field. The average width of the lanes on straight sections when forming a constant tramline for crops, which are sown in a narrow strip method, with a self-propelled sprayer on straight sections was 500 mm, and on turning sections - 900 mm; using a trailed sprayer working in tandem with a tractor, the average stripe width on straight sections was 650 mm, and on turning sections – 900 mm. When creating a constant tramline for sugar beet crops, regardless of the type of agricultural machinery used, the average width of the stripes on straight and turning sections was 900 mm. The length of permanent tramline strips for an agricultural field having a rectangular shape was calculated, and it was found that it depends not only on the geometric shape of the field, but also on the operating parameters of the agricultural machinery used and the nature of the location of straight and turning sections. Based on the data obtained, a calculation was made of the percentage of the allocated area of the agricultural field for its creation or formation. When caring for agricultural crops that are sown in a narrow stripe method using a self-propelled sprayer, the percentage of the allocated field area under a constant tramline is 4.7, and when using a trailed sprayer working in tandem with a tractor, the percentage of the allocated area is 5.9. The percentage of the field area allocated for a constant tramline when cultivating sugar beets is 4.7 and does not depend on the type of agricultural machinery used.

The description of the first rock-dwelling species of butterfly lizard Leiolepis Cuvier, 1829 (Squamata, Agamidae) from the Khorat Plateau in northeastern Thailand.

A new species of rock-dwelling Leiolepis is described from the Khorat Plateau in northeastern Thailand. Leiolepisglaurung sp. nov. can be differentiated from all other sexual species of Leiolepis by a combination of having a black gular region with a wide medial yellow stripe, a yellow ventrum with black mottling, bright red to orange subcaudal coloration, having reduced to no expandable flanks, and having only one black transverse bar on the flanks. This is the first rocky habitat-adapted Leiolepis. Leiolepisglaurung sp. nov. demonstrates numerous ecological adaptations to survive in these rocky habitats. Leiolepis are known for their expandable flanks with bright display colors, however Leiolepisglaurung sp. nov. has reduced or no ability to expand its flanks. We hypothesize this is an adaptation to reduce their body diameter to better fit into smaller rocky burrows unlike the larger and deeper burrows constructed in looser soils by other Leiolepis species. This discovery increases the number of Leiolepis species in Thailand to six, and worldwide to 11.

Design of 16-wavelength high-power heterogeneous III-V/Si laser arrays with varying stripe width and grating period

Multi-wavelength laser array is currently one of the most attractive technologies to provide high density links for advanced optical communications and computing. The conventional scheme of varying grating period is almost impossible to achieve 8-wavelength or more. And, the optical output power of heterogeneously integrated quantum dot laser can hardly meet the commercial demand. In this paper, we report a 16-wavelength high-power heterogeneously integrated quantum dot distributed feedback laser array. To the best of our knowledge, this is the first heterogeneously integrated quantum dot laser array that tunes the lasing wavelength by combining the scheme of varying the stripe width and grating period of laser units. The effective refractive index of gratings is calculated by eigenmode expansion method. When the grating period is fixed at 198 nm, and the stripe widths of laser units are 2.00 μm, 2.25 μm, 2.60 μm and 3.15 μm, respectively, the corresponding lasing wavelengths are 1307.94 nm, 1308.49 nm, 1309.06 nm and 1309.63 nm, respectively, and the wavelength spacing of the adjacent laser units is about 100 GHz. By additionally adjusting the grating period between 196 nm and 202 nm with 2 nm spacing of grating period, a 16-wavelength QD DFB laser array is designed with the wavelength range from 1294.73 nm to 1336.09 nm. In addition, asymmetric distributed feedback grating is adopted to improve the optical output power at the front-end of laser arrays. The maximum ratio of the output power at the both end of laser units is 19.6 when the grating duty cycles of the front-end and the back-end of the λ/4 phase-shift is 0.7 and 0.5, respectively, and the grating lengths is 250 μm and 450 μm, respectively. This work will promote the performance improvement of heterogeneously integrated quantum dot lasers and develop the quantum dot lasers towards multi-wavelength.

Accurate extraction method of multi-laser stripes for stereo-vision based handheld scanners in complex circumstances

A technique for extracting multiline lasers is proposed for handheld scanner. First, a robust matching method for multi-lasers is presented in this work to distinguish every laser stripe in the left and right images by using back-projection algorithm. Then, an improved DBSCAN (Density-Based Spatial Clustering of Applications with Noise) clustering method is promoted to detect noise in the laser images caused by complex scenarios. This approach is focused on the features of the laser stripes in the images, such as normal vectors, stripe width and gray values. These parameters are used as the criteria to find the noise in the images. After the calibration results of stereo-vision and laser-matching results are combined, the 3D information of the noise parts in the laser stripes are recovered accurately. Finally, a subpixel interpolation method based on Shepard interpolation is used to achieve the precise subpixel centerline extraction of laser stripes. And the experiments further valide the effectiveness of the proposed method.

High-power 940 nm DFB laser diode with large optical cavity.

High-power laser diodes with a stable wavelength and narrow linewidth are crucial for many applications. In this study, we introduce a first-order distributed feedback (DFB) grating into an asymmetric large-cavity laser diode operating around 940 nm. This design maintains high output power and offers a wide temperature locking range. The nearly sinusoidal shape first-order grating is fabricated by ultraviolet (UV) nanoimprint lithography, inductively coupled plasma (ICP) dry etching, and wet polishing. At a heat sink temperature of 25°C, the DFB laser diode, with a 200 µm stripe width and 4 mm cavity length, achieves a maximum output power of 24.8 W and a full width at half maximum (FWHM) of 0.4 nm under continuous-wave (CW) conditions. The maximum slope efficiency is calculated to be 1.04 W/A. At an output power of 10.7 W, the device reaches a peak wall-plug efficiency of 56%. Under quasi-continuous operation at 20 A, the laser output spectrum remains locked to the DFB grating over a temperature range from -10°C to 110°C, with a temperature coefficient of 0.062 nm/°C.

A new species of Pupinidius Möllendorff, 1901 (Gastropoda, Stylommatophora, Enidae) from Jiuzhaigou, Sichuan, China.

The genus Pupinidius Möllendorff, 1901 is endemic in China and Nepal and consists of 15 species. China is the distribution centre of it with 12 species being recorded. A new species, Pupinidiuspulchellus Chen, Dai, Wu & Ouyang sp. nov. is described from Jiuzhaigou, Sichuan, China. It can be distinguished from congeneric species by the shell with wide and distinct radial stripes; the thin, slightly reflexed and reddish-brown peristome; the unpointed apex; the unfused A-1 and A-2; the sub-globular and well defined bursa copulatrix; the unexpanded diverticle and the presence of epiphallic caecum.

Relationships between internal solitary wave surface features in optical and SAR satellite images: Insights from remote sensing and laboratory

Internal solitary waves (ISWs) induce convergence and divergence of sea surface currents, manifesting as alternating bright and dark stripes in optical and synthetic aperture radar (SAR) remote sensing images. Although the relationship between ISW surface features in SAR images and ISW-induced surface currents has been extensively explored, it has not been clearly quantified in optical images. This study contrasts the surface features of the same ISWs using optical and SAR images with short time intervals and statistically analyses the 450 ISW stripe widths in the northern South China Sea and the Andaman Sea. The results demonstrate that the ISW surface features in optical and SAR images differ, with the ISW stripe widths of SAR images being 0.83 times those of optical images. Laboratory experiments are conducted to simulate the ISW surface features of optical and SAR images, which exhibit a consistent quantitative relationship with remote sensing results. Further experiments reveal that the ISW-induced free surface displacement is the cause of the differences in the ISW surface features between optical and SAR images. This research provides support for broader quantitative applications of optical remote sensing images.

Silicon‐Based 850 nm GaAs/GaAsP‐Strained Quantum Well Lasers with Active Region Dislocation Blocking Layers

A silicon‐based room temperature (RT) continuous wave (CW) operation quantum well (QW) laser emitting at 850 nm is reported in this article. By applying the dislocation filter superlattice, the threading dislocation density of the GaAs pseudosubstrate on Si is reduced to 1.8 × 107 cm−2. The metal‐organic chemical vapor deposition‐grown laser structure with GaAs/GaAsP QW and InAlAs active region dislocation blocking layer are fabricated into broad‐stripe Fabry–Perot laser diodes. A typical threshold current and threshold current density of 286 mA and 715 Acm−2 are obtained with 2 mm cavity length and 20 um stripe width samples. A 94.2 mW single‐facet output power lasing around 854 nm and a 0.314 WA−1 slope efficiency is measured under RT CW operation. After a 10‐min aging process, the tested laser can operate stably under continuous operation conditions at RT and the lifetime can be approximated using an exponential fitting curve, indicating a good life reliability of this QW laser.

Micro-structured lateral thermal lens for increased output power and narrowed beam divergence in kilowatt-class 9xx nm diode laser bars

Local temperature non-uniformity is a critical limit to power in large-area semiconductor lasers, playing a larger role than the conversion efficiency and temperature sensitivity in the most efficient modern devices. For the specific case of kilowatt-level edge-emitting diode laser bars, we demonstrate that laterally re-distributing current locally within each emitter using a customized micro-structuring of the electrical contact can flatten the thermal profile, based on the thermal design using COMSOL. The concept is demonstrated experimentally in adapted bars that contain eight broad-area emitters, each having wide (∼1100 μm) stripes and a 4 mm long resonator. Each emitter in the laser bar has an electrical contact layer that is electrically structured into parallel sub-contacts using implantation, essential to prevent lateral lasing, implemented here with a period of 29 μm. The width of the individual sub-contacts is narrowed in the device center and then monotonically increased toward the emitter edges to collect a higher proportion of heat at the edges, for a fivefold reduction in the thermal lens, despite a significant (20%) overall increase in electrical and thermal resistance. Two performance benefits are observed. First, the slope varies more slowly with average temperature, recovering (here) around half of the efficiency penalty from in-stripe temperature non-uniformity, and hence increasing the power conversion efficiency at 800 W optical output power by around 5%. Second, the lateral far field (95% power content) is narrowed by around 2° at 800 W optical output power, corresponding to a reduction of around half of the thermal contribution.

Spontaneously Integrated Multicolor InGaN Micro‐Light‐Emitting Diodes for Spectrum‐Controllable Broadband Light Sources

Spontaneously integrated multicolor InGaN micro‐light‐emitting diodes with a microstripe topography achieve selective electrical operation with four different color emissions: green, bluish‐green, bluish‐purple, and purple. The entire microstripe displays broadband emissions because the stripe topography with a convex lens‐like cross section induces a continuous emission wavelength gradient in the overgrown InGaN active layers. Since each wavelength component is distributed along the stripe direction, multiple narrow p‐electrodes are positioned side by side across the stripe width. This design supports selective current injection into the corresponding local areas. This work represents an important step for realizing broadband visible light emitters where individual wavelength components comprising the broad spectra can be modulated and switched independently.

New masquerade observations of Turkish leaf beetles (Coleoptera: Chrysomelidae)

Thirty-five observations of 25 leaf beetle species and their feeding damage are reported. The beetles belong to 13 genera. Obvious masquerade is found in 29 observations. Nine beetle species in our sample are light in color, but two, being generally light colored, have a wide dark stripe along the elytral suture, so that on the photos (and presumably to visual predators in the field) they appear dark. Feeding damage that these two are surrounded with is also dark. In six observations light colored beetles were making light colored damage. In five examples dark colored beetles were observed among both light and dark colored damage. In remaining observations dark colored beetles were making dark colored damage. Masquerade in Cassidinae and larvae of Alticini and Galerucini is reported here for the first time. In addition, observation of flea beetle interacting with ants on leaf surface and use of feeding holes to move from the upper to the lower leaf surface are reported.

High-efficiency and high-brightness broad area laser diodes with buried implantation current blocking

Buried-regrown-implant-structure (BRIS) technology combines two-step epitaxial regrowth with an intermediate ion implantation step in order to realise a buried current aperture close to the active region of a laser diode. In this paper we carry out a systematic performance comparison demonstrating the benefit of BRIS technology in single emitter broad-area lasers (BALs). We investigate stripe width W = 100 μ m and resonator length L = 4 mm single emitter lasers emitting at wavelength λ = 915 nm, comparing the performance of BRIS devices with different implantation depths with reference devices with only contact layer implantation. We show that using BRIS technology we achieve a continuous wave output power of 20 W at 57% efficiency, with a peak efficiency of 68%, and maintain a lateral brightness of 3.4 mm · mrad up to 19 W, improved over the reference devices due to reduced lateral current spreading in the BRIS devices. Further, we show results of ongoing aging experiments, which has shown no device degradation up to 5000 hours from BRIS devices.

1.3 μm InAs/GaAs quantum-dot lasers grown on planar on-axis Si (001) substrates with high slope-efficiency and low differential resistance

We report electrically pumped continuous-wave (CW) InAs/GaAs quantum dot lasers monolithically grown on planar on-axis Si (001) substrates. Combining an asymmetric waveguide epitaxy structure with aluminium-free upper cladding layers and a symmetrical cathode chip structure, 1.3 μm band lasers with low differential resistance and high slope-efficiency have been achieved. Moreover, the optimized symmetrical cathode structure of the laser chips is used to improve the slope-efficiency by reducing the differential resistance and waste heat. The Fabry–Perot broad-stripe edge-emitting lasers with 2000 μm cavity length and 15 μm stripe width achieve a single-facet output power of 73 mW, a single-facet slope efficiency of 0.165 W A−1, and a differential resistance of 1.31 Ω at ∼1.31 μm wavelength under CW conditions at room temperature (25 °C). Importantly, these results provide an effective strategy to achieve 1.3 μm wavelength band single-mode distributed feedback lasers directly on planar on-axis Si (001) substrates with high efficiency.

Assembly and Alignment of High Packing Density Carbon Nanotube Arrays Using Lithographically Defined Microscopic Water Features.

High packing density aligned arrays of semiconducting carbon nanotubes (CNTs) are required for many electronics applications. Past work has shown that the accumulation of CNTs at a water-solvent interface can drive array self-assembly. Previously, the confining interface was a large-area, macroscopic feature. Here, we report on the CNT assembly on microscopic water features. Water microdroplets are formed on 10-100 μm wide hydrophilic stripes patterned on a substrate. Exposure to CNTs dispersed in solvent accumulates CNTs at the microdroplet-solvent interface, driving their alignment and deposition at the microdroplet-solvent-substrate contact line. Compared with macroscopic methods in which the contact line uncontrollably moves across the substrate as it is pulled out of the liquids, the hydrophilic patterns and microdroplets allow pinning of the contact line. As CNTs deposit, the contact line self-translates, allowing for dense CNT packing. We realize monolayer CNT arrays aligned within ±3.9° at density of 250 μm-1 and field effect transistors with a high current density of 1.9 mA μm-1 and transconductance of 1.2 mS μm-1 at -0.6 V drain bias and 60 nm channel length.

Enhancing microalgae biomass production: Exploring improved scraping frequency in a hybrid cultivation system

Recently, hybrid systems, such as those incorporating high-rate algal ponds (HRAPs) and biofilm reactors (BRs), have shown promise in treating domestic wastewater while cultivating microalgae. In this context, the objective of the present study was to determine an improved scraping frequency to maximize microalgae biomass productivity in a mix of industrial (fruit-based juice production) and domestic wastewater. The mix was set to balance the carbon/nitrogen ratio. The scraping strategy involved maintaining 1 cm wide stripes to retain an inoculum in the reactor. Three scraping frequencies (2, 4, and 6 days) were evaluated. The findings indicate that a scraping frequency of each 2 days provided the highest biomass productivity (18.75 g total volatile solids m−2 d−1). The species’ behavior varied with frequency: Chlorella vulgaris was abundant at 6-day intervals, whereas Tetradesmus obliquus favored shorter intervals. Biomass from more frequent scraping demonstrated a higher lipid content (15.45%). Extrapolymeric substance production was also highest at the 2-day frequency. Concerning wastewater treatment, the system removed 93% of dissolved organic carbon and ∼100% of ammoniacal nitrogen. Combining industrial and domestic wastewater sources to balance the carbon/nitrogen ratio enhanced treatment efficiency and biomass yield. This study highlights the potential of adjusting scraping frequencies in hybrid systems for improved wastewater treatment and microalgae production.

High brightness edge-emitting laser diode with wavelength self-organization in ultra-broad emitting area.

We have proposed and experimentally demonstrated an efficient method for generating high power and brightness based on an ultra-broad area laser diode (UBALD). We have developed a single-emitter UBALD capable of self-organization multi-wavelength emissions for two stripe widths of 2 and 5 mm, respectively. The 2 mm UBALD delivers an output power of 55 W with a beam quality M2 of 1.3 × 25.3 and a brightness of 179 MW/(cm2·sr). The 5 mm UBALD produces an output power of 121 W with a beam quality M2 of 2.1 × 32.7 and a brightness of 192 MW/(cm2·sr). To the best of our knowledge, these results represent the highest output power and highest brightness ever achieved from a single edge-emitting LD emitter to date.