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A theoretical investigation of electronic properties of self-assembled InAs/InP quantum dots (QDs) is presented, utilizing a novel two-step modeling approach derived from a double-capping procedure following QD growth processes, a method pioneered in this study. The electronic band structure of the QD is calculated by the newly established accurate two-step method, i.e., the improved strain-dependent, eight-band k p method. The impact of various QD structural parameters (e.g., height, diameter, material composition, sublayer, and inter-layer spacer) on electronic states' distribution and transition energies is investigated. Analysis of carrier dynamics within QDs includes intraband and interband transitions. The calculation of the carrier transitions between two atomic states, providing insights into optical gain or loss within QDs, is in terms of dipole matrix element, momentum matrix element, and oscillation strength, etc. In addition, the time-domain, traveling-wave method (i.e., rate equations coupled with traveling-wave equations) is used to investigate the optical properties of QD-based lasers. Several optical properties of the QD-based lasers are investigated, such as polarization, gain bandwidth, two-state lasing, etc. Based on the aforementioned method, our key findings include the optimization of carrier non-radiative intraband relaxation through sublayer manipulation, wavelength control through emission blue-shifting and gain bandwidth via variation of sublayer, polarization control of QDs photoluminescence via excited states' transitions, and the enhancement of two-state lasing in InAs/InP QD lasers by thin inter-layer spacers. This review offers comprehensive insights into QDs electronic band structures and carrier dynamics, providing valuable guidance for optimizing QD-based lasers and their potential designs. [ABSTRACT FROM AUTHOR]

In this paper, two wavelength division multiplexing (WDM) optical communication systems employing an enhanced L-shape hybrid fiber amplifier (E-L-shape-HFA) are designed and simulated. Both scenarios utilize a combination of the second-order stimulated Raman scattering (SO-SRS) and a tunable optical filter (TOF) technique. One system consists of 16 channels, while the other has 23 channels. Three different frequency ranges: short band (S-band), conventional band (C-band), and long band (L-band) are covered. The integration of two techniques SO-SRS and TOF has been enhanced the system's performance to meet the tremendous development of the optical communication systems nowadays. The first scenario results achieved high average gain ( G av. ) of 35 dB and wide flat gain bandwidth of 75 nm expanded from 1520 to 1595 nm. In addition, the second scenario results achieved an ultra-wide flat gain bandwidth of 110 nm extended from 1515 to 1625 nm and G av. of 26 dB. Furthermore, a desirable average noise figure (NFav.) of 4 dB has been obtained for both scenarios at input signal power of − 25 dBm. Moreover, the system is examined and optimized at input signal power range from − 25 to 20 dBm a step of 5 dbm in terms of bit error rate (BER) and quality factor (Q-factor). [ABSTRACT FROM AUTHOR]

Polarization-insensitive semiconductor optical amplifiers (SOAs) in all-optical networks can improve the signal-light quality and transmission rate. Herein, to reduce the gain sensitivity to polarization, a multi-quantum-well SOA in the 1550 nm band is designed, simulated, and developed. The active region mainly comprises the quaternary compound InGaAlAs, as differences in the potential barriers and wells of the components cause lattice mismatch. Consequently, a strained quantum well is generated, providing the SOA with gain insensitivity to the polarization state of light. In simulations, the SOA with ridge widths of 4 µm, 5 µm, and 6 µm is investigated. A 3 dB gain bandwidth of >140 nm is achieved with a 4 µm ridge width, whereas a 6 µm ridge width provides more output power and gain. The saturated output power is 150 mW (21.76 dB gain) at an input power of 0 dBm but increases to 233 mW (13.67 dB gain) at an input power of 10 dBm. The polarization sensitivity is <3 dBm at −20 dBm. This design, which achieves low polarization sensitivity, a wide gain bandwidth, and high gain, will be applicable in a wide range of fields following further optimization. [ABSTRACT FROM AUTHOR]

The growing need for high-performance folded cascode CMOS OTAs in various fields, such as electronics and communications, requires them to operate with wide bandwidth, high voltage gain, compact devices, and low power consumption. Recent research indicates that implementing the water cycle algorithm (WCA) can greatly improve the performance of the folded cascode CMOS operational transconductance amplifier (OTA). This is due to the WCA's ability to perform both global search and local exploration efficiently. Notably, the OTA in question is constructed using 0.18µm TSMC technology and operates with a voltage supply of ±1.8V. The results of the simulation were collected using PSPICE software (version 17.4). These design solutions demonstrate exceptional efficiency, delivering significant amplification, high frequency, and minimal power usage. In addition, the paper demonstrates the implementation and simulation outcomes of a folded cascode CMOS operational transconductance amplifier utilizing the water cycle algorithm, MATLAB was employed for this purpose. Using WCA in the design of an OTA for folded cascode CMOS OTA results in significant improvements in performance metrics. Experiences a significant increase in voltage gain, with an increase in gain bandwidth by a factor of five compared to the algorithm-free design. In addition, power consumption is reduced by 15.5%, and the common mode rejection ratio is improved by 15.18% compared to the non-WCA folded cascode CMOS OTA design. The results highlight the effectiveness of the WCA technique as a powerful optimization strategy to improve the performance of folded cascode CMOS OTA. [ABSTRACT FROM AUTHOR]

This paper provides a detailed exploration of CMOS operational amplifiers (Op-Amps) aimed at enhancing understanding of their development, design, and application. To achieve this, a comprehensive examination of the common characteristics, parameters, and bibliographic reviews of Op-Amps, distinguishing among various chosen operational amplifiers. A comprehensive bibliographic review of the operational amplifier's keywords between 2008 and 2018 has also been conducted. A bibliometric analysis of 4997 documents from the Web of Science (WOS) Collection is conducted using VOSviewer software. Furthermore, an analysis and comparison of these Op-Amps across functional aspects relevant to industrial and biomedical applications, emphasising the salient characteristics of each technique. After the survey, a novel Op-Amp design is proposed, incorporating a differential amplifier at the first stage, along with a compensating capacitor and a high gain stage. The biasing circuitry is replaced with an active load resistor (MOS transistor), simplifying layout design, and reducing the amplifier's area and power consumption compared to traditional two-stage designs. The power source for this design is 3.3 V. This designed operational amplifier achieved a gain of 62.9449 dB, a high CMRR of 92.8079 dB, and a unity gain bandwidth of 33 MHz, and the optimised layout area is 0.001476 μm2. The proposed circuit was designed and simulated utilising the Cadence Virtuoso 180 nm CMOS process. The simulation results show that the desired criteria have been met. Additionally, the challenges and future possibilities in analog circuits, laying the groundwork for research in both analogue and digital circuits to tackle complex real-world issues have been addressed.

This work clarifies the analysis of the theoretical study of noise and transmission gain characteristics of semiconductor optical amplifiers (SOAs), which are relevant in the novel local area optical communication systems. We investigated the effects of noise on AlGaAs/GaAs SOA transmission performance through the measurement of output power, optical gain, the optical signal-to-noise ratio, and noise figure. It was observed that noise has a dramatic effect on SOAs' operation transmission efficiency, and the performance of the amplifier structure may be limited. If the drive current and injection power at the SOA can be changed and its active region length modified, then the variation of gain, optical signal-to-noise ratio, and noise figure at the output of the structure can be obtained. [ABSTRACT FROM AUTHOR]

Polarization-insensitive semiconductor optical amplifiers (SOAs) in all-optical networks can improve the signal-light quality and transmission rate. Herein, to reduce the gain sensitivity to polarization, a multi-quantum-well SOA in the 1550 nm band is designed, simulated, and developed. The active region mainly comprises the quaternary compound InGaAlAs, as differences in the potential barriers and wells of the components cause lattice mismatch. Consequently, a strained quantum well is generated, providing the SOA with gain insensitivity to the polarization state of light. In simulations, the SOA with ridge widths of 4 µm, 5 µm, and 6 µm is investigated. A 3 dB gain bandwidth of >140 nm is achieved with a 4 µm ridge width, whereas a 6 µm ridge width provides more output power and gain. The saturated output power is 150 mW (21.76 dB gain) at an input power of 0 dBm but increases to 233 mW (13.67 dB gain) at an input power of 10 dBm. The polarization sensitivity is

In this study, a wideband transmitarray antenna consisting of a new two-layer unit-cell is proposed. In the proposed unit cell, a double cross slot ring (DCSR) is etched on a square patch which support feed angle variation up to 40°. The first layer of the antenna has 169 elements, whereas in the second layer the unit-cells in the fifth-ring are removed such that it has 144 elements, so the antenna has a non-uniform two-layer structure. The proposed non-uniform structure has wider gain bandwidth than the uniform structure. In order to confirm the simulation, a prototype of the antenna is manufactured and tested. The measured results reveal that the antenna has 31% (9.95–13.62 GHz), 41.4% (9.85–15 GHz) and 46% (9.48–15.15 GHz) gain bandwidth for the 1-dB, 2-dB, and 3-dB criterion, respectively. Additionally, the maximum gain of 21.64 dB at 10.6 GHz with an aperture efficiency of 27.45% is achieved. So, the proposed structure has broadband performance which is an appropriate choice for broadband applications in communication systems. [ABSTRACT FROM AUTHOR]

A double-layer element consisting of a spider-shaped structure on the top layer and a pair of concave arms with a circular ring on the middle layer is proposed for the wideband reflectarray with low cross-polarization characteristics. The unit cell offers a linear and wider phase range of 800 ∘ . Based on the proposed unit cell, an offset-fed reflectarray with an octagonal aperture comprising 6769 unit cells is constructed at 11.725 GHz. The reflectarray offers 1 dB and 3 dB gain bandwidths of 25.2% and 32.3%, respectively, with an operating frequency range of 10–13.85 GHz. A peak gain of 31.2 dBi with an aperture efficiency of 42% is achieved. The cross-polarization levels are less than the co-polarization by 40 dB over the entire operating band. [ABSTRACT FROM AUTHOR]

A wideband dual-polarized metal lens is proposed in this article for millimeter-wave (mm-wave) applications. Compared with the traditional lens, the focal length of the proposed novel metal lens can be of any value in theory; in other words, the focal diameter ratio ($f/D$) can be arbitrarily adjusted. The metal 3-D printed technology is used to reduce the fabrication cost. The unit cell of the lens is a square open-ended waveguide. Since the phase velocity of the electromagnetic wave in the metal waveguide is faster than that in the air, the phase compensation can be controlled by adjusting the height of each unit of the lens. It helps to realize the conversion from the quasi-spherical wave of the feed source to the plane wave radiation of the lens. Due to the use of symmetrical elements, the lens can support different dual-polarized radiation (dual-linear polarization and dual-circular polarization). Considering the processing cost and design difficulty, a metal lens with $9\times $ 9 unit cells was processed to verify our design. The $f/D$ is selected as 1. Simulated results for the lens antenna show a peak aperture efficiency (AE) of 43.8% and 38% for linearly polarized (LP) and circularly polarized (CP) radiation, respectively. The antenna shows a stable pattern and wide 3 dB gain bandwidth (26–40 GHz), which covers the entire Ka-band. The measured results of the lens demonstrate a peak gain of 24 dBi and 23 dBic for LP and CP radiation with an aperture of about $7.5\,\,\lambda \times 7.5\,\,\lambda $ ($\lambda $ is the free space wavelength at 30 GHz). The proposed lens features a wide gain bandwidth with dual polarization, low cost, and good radiation performance, which is well suited for mm-wave wireless applications. [ABSTRACT FROM AUTHOR]

A novel wideband reflectarray antenna based on a sub-wavelength Archimedes spiral unit cell is proposed in this paper. The size of the unit cell is fixed to 0.39 λ 0 ( λ 0 -the free space wavelength at 5.8 GHz), and the reflection phase variation can be obtained by changing the inward extension length of the arms. After the element simulation analysis, a smooth and almost linear reflection phase curve is achieved. The phase range can reach more than 500°, which is enough to meet the phase shift requirement of the reflectarray. Based on the proposed unit cell, a 10 × 10-element reflectarray with the size of 220 mm×220 mm is designed, fabricated, and measured. The measured result agrees well with the simulations, which show relatively wide 1- and 3-dB gain bandwidths of 20.7% (5.57–6.77 GHz) and 31.4% (5.31–7.13 GHz), respectively. The measured gain at its working frequency of 5.8 GHz is 18.9 dBi with an aperture efficiency of 34.2%. Furthermore, the cross-polarization levels of the proposed antenna are less than −25 dB, which attributes to all the elements that are arranged mirror symmetrically. [ABSTRACT FROM AUTHOR]

A prior-knowledge-guided deep-learning-enabled (PK-DL) synthesis method is proposed for enhancing the transmission bandwidth and phase shift range of metacells used for the design of metalens antennas. The algorithm of conditional deep convolutional generative adversarial network (cDCGAN) is utilized in the proposed deep-learning (DL) method. Prior knowledge, including well-known fundamental electromagnetic theorems and experience in antenna design, is purposely applied at the early stage of the proposed method to strategically guide and speed up the synthesis. The proposed intelligent method provides the design of pixelated metacells with high degrees of freedom so that the key performance of the synthesized metacells exceeds the existing limit of conventional design methods by generating a rich profusion of cell patterns. For example, the synthesized triple-layer metacell achieves the −1 dB phase shift range of 330° breaking the limit of 308° derived by existing techniques. The proposed synthesis method also provides the additional capability to flexibly control the phase shift not only at the center frequency but also over a frequency range of interest. A Ku-band metalens antenna formed with the synthesized metacells demonstrates the achieved 1 and 3 dB gain bandwidths increase by 52.2% and 42.6%, respectively, compared to the metalens antenna using the well-known Jerusalem cross (JC) metacells. The proposed method extends the capability for the synthesis of metacells and metalens antennas with enhanced performance. [ABSTRACT FROM AUTHOR]

In this paper, a single-stage Super Class-AB operational transconductance amplifier (OTA) using current reuse technique is presented. It is based on two scaled current mirrors located at the tail current nodes of input pairs, reusing the current through the cross-coupled input pairs by a current gain factor of α, and delivering new currents to the output branch, enhancing the overall transconductance (G m) by a factor of (1+α). With adaptive biasing and local common mode feedback (LCMFB), slew rate (SR), open loop gain (A OL) and gain-bandwidth product (GBW) are improved. An prototype has been designed in TSMC 0.18-μm CMOS process. Post-simulation shows the positive and negative slew rate of 22V/μs and −38.3V/μs, respectively, a GBW of 3.72 MHz, a DC gain of 65.6 dB with a phase margin of 69.2° for a capacitive load of 70 pF. The proposed OTA consumes a total power of 16.2 μW under a 1.8V supply voltage. • Transconductance is enhanced through current reuse by a factor of (1+α). • Slew rate, open loop gain and gain-bandwidth of the OTA are simulated and analyzed. • Adaptive biasing and local common mode feedback are utilized. [ABSTRACT FROM AUTHOR]

A double-layer element consisting of a spider-shaped structure on the top layer and a pair of concave arms with a circular ring on the middle layer is proposed for the wideband reflectarray with low cross-polarization characteristics. The unit cell offers a linear and wider phase range of 800∘. Based on the proposed unit cell, an offset-fed reflectarray with an octagonal aperture comprising 6769 unit cells is constructed at 11.725 GHz. The reflectarray offers 1 dB and 3 dB gain bandwidths of 25.2% and 32.3%, respectively, with an operating frequency range of 10–13.85 GHz. A peak gain of 31.2 dBi with an aperture efficiency of 42% is achieved. The cross-polarization levels are less than the co-polarization by 40 dB over the entire operating band.

Developing semiconductors with broad gain bandwidth has always been at the forefront of laser technologies. The variation in feedback resonators can provide a useful tool for producing a relatively wide range of discrete lasing wavelengths. However, the lasing wavelength range is limited by the fundamental gain bandwidth of the semiconductor itself. Gain bandwidth engineering for full‐color range lasing though remains a daunting challenge. Considering the abundant energy levels of organic semiconductors, the authors stride over the barrier of the gain bandwidth limitation and demonstrate the dynamically tunable amplification/lasing across the entire emission range by leveraging on Förster resonance energy transfer (FRET)‐assisted guest–host blends. The unprecedented tunability in amplification and lasing is governed by energy transfer process, which enables them to achieve wavelength‐tunable semiconductor lasers spanning the full visible region of the electromagnetic spectrum. Their distributed feedback (DFB) lasers using these guest–host blends as gain media cover almost all CIE color gamut (94%), which is 170% more perceptible colors than standard Red Green Blue color space. These insights can guide the versatile and convenient design of organic semiconductor materials transcending the current gain bandwidth limitation, paving the way for next generation of optoelectronic devices. [ABSTRACT FROM AUTHOR]

A new structure for improving the performance of recycling folded cascode (RFC) operational transconductance amplifier (OTA) is presented. The improvement has been achieved using two current recycling stages. The first current recycled stage acts as an adaptive biasing current source for the second stage. Compared to the RFC OTA, the proposed OTA shows a significant improvement in slew rate (SR), gain-band-width (GBW), and DC gain. Simulation results in 0.18 µm standard CMOS technology exhibit that the proposed OTA achieves an about three times improvement in SR, 12.4 dB DC gain enhancement, and approximately two times increase in gain bandwidth compared to the RFC OTA. The proposed OTA consumes 433 µW @1.8 V which makes it appropriate for low-power applications. [ABSTRACT FROM AUTHOR]

In this article, corrugated conductor plates with slow wave properties are used as slow wave unit cell structures to increase the aperture efficiency of the transmitarray antenna. The slow wave structure is composed of a simple conductive plate and a corrugated conductor plate facing each other. Two types of unit cells are considered for the design of the transmitarray antenna. In the first type, the spacing and height of the corrugated sections are constant, and only by changing the number of the corrugation the phase shift is created. In the second type, the distance of the corrugated sections and the number of the corrugation is constant, and only by varying the corrugated height, the phase shift is controlled. These slow wave structures can easily cover 360° and are also suitable for large transmitarray. An array of such two types of slow wave unit cell structure is placed in front of the horn antenna and the aperture efficiency of the antenna is improved by the required phase correction. The transmitarray antenna based on the second type of the unit cell is fabricated and measurement results indicate that the transmitarray antenna has a maximum aperture efficiency of 89.4% at the frequency of 10.5 GHz and 1‐dB gain bandwidth of 30%. [ABSTRACT FROM AUTHOR]

The objective of this work is to investigate and compare the impact of forward, backward and bidirectional pumping methods in repeater less distributed Raman fiber amplifier system and to analyze its benefits in long haul optical communication links. The effect of different pump wavelengths and pump powers are also analyzed. By adjusting the forward pump power as well as backward pump powers carefully, the transmission performance can be improved. The pump power ratio is adjusted to 20% so that the degradation of signal due to non-linear effect is reduced. The distributed gain and pump penetration depth for different pump power ratios are also examined. A comparison of different pumping methods reveals that bidirectional pumping gives the optimum performance in terms of higher gain and lower noise figure when compared to single pumps and unidirectional pumping. Low pump power ratios lead to better transmission performance than higher pump ratios due to lesser non-linear effects. The simulation results indicate that signal power evolution decreases with the increase in length of the fiber. It is also found that the pump power is more relevant during the first 50 km of the distributed fiber line and it decreases as it goes beyond 100 km. By choosing the optimum pumping methods and number of pumps, Raman Amplifiers can be used in almost all places where optical amplifiers are required. [ABSTRACT FROM AUTHOR]

In this study, the relationship between thermal sensitivity of a CMOS operational transconductance amplifier (OTA) and other parameters of the OTA such as gain bandwidth (GBW), DC gain, settling time, slew rate (SR), etc. is analyzed and discussed. For the first time, it is shown that although some techniques such as adaptive biasing and DC gain enhancement can be utilized to improve the transient response of a CMOS-OTA by increasing the input stage's gain, DC gain, GBW and SR, yet this causes a significant increase in the thermal sensitivities of the CMOS-OTA, so that, the reliability of accurate operation of the CMOS-OTA under variation in ambient temperature effectively decreases. This paper concludes that a reconciliation of the thermal reliability with improvement of the CMOS-OTA parameters should be considered when the CMOS-OTA is designed and implemented. This point is the contribution of this work that has not been considered and addressed in any other works. Simulated results performed using 0.18 μ m SILTERRA CMOS process technology and real experimental results are presented that explicitly verify the theoretical results. [ABSTRACT FROM AUTHOR]

Simple and efficient frequency compensation technique for a four‐stage amplifier is presented in this study. Using a differential feedback stage and a single Miller capacitor on its output, the frequency compensation network is formed. The proposed configuration is described via matrix description. Meanwhile, an analytical transfer function is calculated. The proposed amplifier demonstrates low die occupation because of the small value of the compensation capacitor while shows acceptable frequency response regarding gain bandwidth and phase margin values. In addition, the design procedure is simple compared to the previous state‐of‐the‐art. The HSPICE circuit simulator and TSMC 0.18 µm CMOS technology were exploited to verify theoretical presentation. [ABSTRACT FROM AUTHOR]

A wideband triple-stacked CMOS distributed power amplifier (DPA) is implemented using a commercial 65-nm CMOS process. To enhance the output power, a triple-stacked field effect transistor (FET) is used as a gain cell in the DPA. Double inductive peaking, in which inductors are inserted at each gate and each interstage of the gain cells, is used to enhance the gain bandwidth. By analyzing the trans-conductance characteristics in the triple-stacked gain cell, interstage inductive peaking (IIP) is used to boost the gain in the mid-band frequency, and gate-inductive peaking (GIP) is used to extend the gain bandwidth in the high-edge frequency. The proposed double inductive peaking ideally enables the gain bandwidth of triple-stacked DPAs to increase from 22 to 44 GHz. The proposed DPA obtains a measured power gain of 11–15.7 dB and a measured output power of 12.8–21.7 dBm from dc to 38 GHz. [ABSTRACT FROM AUTHOR]

An approach to implement single-ended power-efficient static class-AB Miller op-amps with symmetrical and significantly enhanced slew-rate and accurately controlled output quiescent current is introduced. The proposed op-amp can drive a wide range of resistive and capacitive loads. The output positive and negative currents can be much higher than the total op-amp quiescent current. The enhanced performance is achieved by utilizing a simple low-power auxiliary amplifier with resistive local common-mode feedback that increases the quiescent power dissipation by less than 10%. The proposed class AB op-amp is characterized by significantly enhanced large-signal dynamic, static current efficiency, and small-signal figures of merits. The dynamic current efficiency is 15.6 higher, the static current efficiency is 10.6 times higher, and the small-signal figure of merit is 2.3 times higher than the conventional class-A op-amp. A global figure of merit that determines an op-amp’s ultimate speed is 6.33 times higher than the conventional class A op-amp.

Highly integrated multilayered printed circuit board-based patch antenna arrays are proposed in this study for 60 GHz wireless communications. Electromagnetic coupling between two stacked patches is used to achieve the broadband performance. Different structures of single element antennas, two-element antenna arrays and four-element antenna arrays are presented. The two compact four-element antenna arrays show < −10 dB impedance bandwidth of 13 and 14.6% with 12 dBi peak gain. The arrays have the 3 dB gain bandwidth of 9 and 13%. A single column, four-element sub-array is used to design 4 × 16 antenna array. This array delivers 20.8 dBi peak gain with 13% impedance and gain bandwidth. Furthermore, a two-element series fed array is used to realise a 2 × 16 phased antenna array. This array is fed through a 16 × channel radio frequency IC to achieve the beam steering in [inline-formula] range.

An approach for the radiation pattern reshaping for TM12 mode is proposed in this communication. Initially, the working principle is theoretically investigated by far-field calculation. It demonstrates that by decreasing two key factors, $n$ and $W/\lambda $ , the radiation of TM12 mode could be effectively transformed into the broadside type without sidelobes. Thus, after combining with the fundamental TM10 mode, the proposed approach is well suited for dual-band or wideband applications. Finally, a wideband prototype is designed, fabricated, and tested. The simulated and measured results are found to be in good agreement with each other, illustrating that the proposed antenna simultaneously achieves compact dimensions, wide bandwidth (18.6%), stable broadside gain (8.55–10.07 dBi), and low cross polarization (−22 dB). [ABSTRACT FROM AUTHOR]

This paper reports the development of a wideband resonant cavity antenna (RCA). The RCA device was obtained by using an optimized aperture-coupled coplanar waveguide fed wideband patch antenna and a metamaterial-based superstrate design. The wideband behavior is based on the effects of Fabry–Perot cavity on either side of the resonant frequency of the metamaterial superstrate and the finite size of the superstrate to obtain enhanced gain around this frequency. In addition, the metamaterial superstrate in this paper contains two identical layers of a frequency selective surface (FSS) based on a 2-D patch array rather than dissimilar arrays as used in the previous studies. Two such FSS layers are assembled using a laser micromachined polymethyl methacrylate rim and an SU8-based bonding method. The air spacer based metamaterial design offers better performance by minimizing the dielectric loss between the metallic patch arrays and also offers flexibility in the control of the separation between the two FSS layers as well as resulting in a lightweight RCA device. The RCA device was designed to operate in the X-band. The dimensions of the compact RCA device are $45\times 45\times24$ mm3. The gain of the device was measured to be ~13 dBi with a 3-dB bandwidth of 46% and a corresponding 1-dBi-ripple bandwidth as wide as 40%. The measured impedance bandwidth was 44%. [ABSTRACT FROM AUTHOR]

Abstract The Er3+/Yb3+-codoped lead phosphate (PPbKANErYb) glasses have been prepared by using melt quenching technique and characterized through spectroscopic studies such as absorption, emission, decay and upconversion measurements. An intense near-infrared (NIR) emission at 1.53 μm was observed which has been explained based on the effective energy transfer from Yb3+ to Er3+ ions. The absorption (4I 15/2 → 4I 13/2) and emission cross-section (4I 13/2 → 4I 15/2) of 1.53 μm emission band was calculated and found to be of the order of 6.76 × 10−21 and 7.9 × 10−21cm2, respectively, by using the McCumber theory. The PPbKANErYb glasses exhibit higher luminescence intensity (more than 3 times) and full width at half maxima (55 nm) compared to 1.0 mol % Er3+ singly doped glass (50 nm). All the decay curves of the 4I 13/2 level exhibited single exponential nature and the lifetimes increased (1760, 1776, 1942 and 2830 μs) with the increase of Yb 2 O 3 (0.5, 1.0, 2.0 and 3.0 mol %) concentration. Intense red band at 670 nm corresponding to 4F 9/2 → 4I 15/2 transition and green emission bands at around 530 and 555 nm corresponding to 2H 11/2 → 4I 15/2 and 4S 3/2 → 4I 15/2 , transitions, respectively, have been observed under the excitation of 980 nm. The intensity of the upconversion emissions is found to be increased with the increase of Yb3+ ion concentration and its mechanism have been explained. The luminescence decay curves of the 4S 3/2 → 4I 15/2 upconversion luminescence of Er3+/Yb3+ codoped PPbKAN glasses under the infrared excitation of 980 nm have been evaluated. The results reveal that the investigated glasses might be potential candidates for optical fiber amplifiers/laser sources at 1.55 μm band. Graphical abstract Image 1 Highlights • Effect of Yb3+ on luminescence of Er3+ in lead phosphate glasses was studied. • The lifetimes of 4I 13/2 → 4I 15/2 level of Er3+ increased in the presence of Yb3+. • The 4S 3/2 → 4I 15/2 luminescence decay curves with λ exc = 980 nm have been evaluated. • Increase of power enhanced the I UP and further increase leads to thermal quenching. • The Er3+/Yb3+: lead phosphate glasses found to be suitable for optical fiber amplifiers. [ABSTRACT FROM AUTHOR]

Using well-calibrated TCAD simulation we explore, for the first time, the impact of buried oxide (BOX) thickness and dielectric constant on the analog circuit performance of 30-nm ultra-thin body germanium-on-insulator (GeOI) pMOSFETs. Our findings show that GeOI MOSFETs with a 20 nm SiO 2 BOX offer lower subthreshold leakage current, high transconductance, improved transconductance generation factor and high intrinsic voltage gain. Furthermore, while GeOI MOSFETs with a 20 nm thin HfO 2 BOX exhibit the lowest output conductance and highest voltage gain, GeOI MOSFETs with a 200 nm thick HfO 2 BOX yield the highest transconductance and unity gain cut-off frequency. Moreover, we design common source amplifiers using GeOI pMOSFETs, analyze and optimize their performance. Our results show that the highest amplifier gain of 6.18 and gain bandwidth of 15.32 GHz are obtained with 20 nm HfO 2 BOX while the highest bandwidth of 3.85 GHz is achieved at BOX thickness of 200 nm. [ABSTRACT FROM AUTHOR]

We investigate the influence of gain fiber on dissipative soliton pairs in passively mode-locked (PML) fiber laser based on black phosphorus (BP) as a saturable absorber. Numerical simulations show that we can generate the dissipative soliton pairs in PML fiber laser when the gain fiber parameters (gain saturation energy and gain bandwidth) are in an appropriate dynamic range, and the dissipative soliton pairs become unstable once the range is exceeded. Then we analyze the dynamic evolution of the dissipative soliton pairs and the influence of gain fiber on the pulse separation, peak power, and single-pulse energy of the dissipative solitons pairs. [ABSTRACT FROM AUTHOR]

Two-dimensional materials such as graphene or black phosphorus have attracted attention of researches in the field of ultra-fast photonics. In this paper, the structure of the passively mode-locked Er-doped fiber laser based on black phosphorus as a new saturable absorber has studied by modeling and analysis. The dissipative solitons characteristics in passively mode-locked Er-doped fiber laser are obtained in the simulation. The research focuses on analyzing the influence of gain bandwidth and gain saturation energy on the pulse duration, peak power, and single-pulse energy of the dissipative solitons. [ABSTRACT FROM AUTHOR]

This paper describes techniques for high-energy laser pulse amplification in multi-PW femtosecond laser pulses. Femtosecond laser pulses can be generated and amplified in laser media with a broad emission spectral bandwidth, like Ti:sapphire crystals. By chirped pulse amplification (CPA) techniques, hundred-Joule amplified laser pulses can be obtained. Multi-PW peak-power femtosecond pulses are generated after recompression of amplified chirped laser pulses. The characteristics and problems of large bandwidth laser pulses amplification in Ti:sapphire crystals are discussed. An alternative technique, based on optical parametric chirped pulse amplification (OPCPA) in nonlinear crystals, is presented. Phase-matching conditions for broad bandwidth parametric amplification in nonlinear crystals are inferred. Ultra-broad phase matching bandwidth of more than 100 nm, able to support the amplification of sub-10 fs laser pulses, are demonstrated in nonlinear crystals, such as Beta Barium Borate (BBO), Potassium Dideuterium Phosphate (DKDP), and Lithium Triborate (LBO). The advantages and drawbacks of CPA amplification in laser crystals and OPCPA in nonlinear crystals are discussed. A hybrid amplification method, which combines low-medium energy OPCPA in nonlinear crystals with high energy CPA in large aperture laser crystals, is described. This technique is currently used for the development of 10-PW laser systems, with sub-20 fs pulse duration and more than 1012 intensity contrast of output femtosecond pulses.