Tunable Operation Research Articles

Generation of orbital angular momentum light based on mechanically induced long-period fiber gratings using 3D printing technique

• An OAM beam generator was proposed with broadband and tunable operation wavelength. • OAM generation was achieved by employing 3D-printed mechanically induced few-mode fiber gratings. • By adjusting applied pressures and inclination angle of few-mode fibers, the operation wavelength can be tuned. • The operational bandwidth can be broadened by employing cascaded few-mode fiber gratings. We propose and experimentally demonstrate an orbital angular momentum (OAM) beam generation method based on mechanically induced few-mode fiber gratings fabricated using 3D printing technique. Experimental results indicate that the transmission depth at resonance wavelength of few-mode fiber gratings with axially uniform refractive index could be adjusted when different lateral pressures are applied onto the few-mode fibers, and hence mode coupling efficiency between the fundamental core mode and LP 11 mode could be controlled in this way. In addition, by changing the inclination angle of the few-mode fibers with respect to direction perpendicular to the mask grooves, the resonance wavelength of the few-mode grating could be changed as well. Besides uniform fiber gratings, we have also investigated the spectral broadening property of the few-mode cascaded fiber grating, and a 10-dB spectral bandwidth up to 114 nm is obtained experimentally. Our proposed OAM light generation method based on mechanically induced fiber gratings using 3D printing technique possesses several desirable merits such as low cost, ease of operation, flexibility in grating structure and no damage to fiber medium, which is anticipated to provide low lost and flexible solution to generation of broadband OAM light for future OAM-based communication systems.

Varactor-Based Phase Shifters Operating in Differential Pairs for Beam-Steerable Antennas

A concept of varactor-based phase shifter operating in differential pair for beam-steerable antennas is presented in this article. The basic phase-tuning unit consists of a microstrip transmission line and several shorted-stub-terminated varactors loaded on its edge. A pair of these phase-tuning units working in differential mode can achieve a full 360° phase shift, which allows a low loss and simple structure. An accurate equivalent circuit model for this phase shifter is developed for fast calculation allowing the design and optimization of the structure with a genetic algorithm (GA). A pair of phase-tuning units, each including three stub-loaded varactors, is identified as a practical solution to produce a continuously tunable phase difference nearly covering 0°–360°, with two symmetrical 11°-wide blind zones and a maximum insertion loss of 2.04 dB. A 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times4$ </tex-math></inline-formula> beam-steerable dielectric resonator antenna (DRA) array is then designed, fabricated, and tested to demonstrate the practicality of the proposed phase shifter. The measured results illustrate that the array is able to continuously scan from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 45^\circ $ </tex-math></inline-formula> to 45°, with a tunable operating frequency band from 4.75 to 5.25 GHz. All these findings suggest that the proposed phase shifter concept is promising and practical to realize beam-scanning antennas.

Calibrated Photoacoustic Spectrometer Based on a Conventional Imaging System for In Vitro Characterization of Contrast Agents.

Photoacoustic (PA) imaging systems are spreading in the biomedical community, and the development of new PA contrast agents is an active area of research. However, PA contrast agents are usually characterized with spectrophotometry or uncalibrated PA imaging systems, leading to partial assessment of their PA efficiency. To enable quantitative PA spectroscopy of contrast agents in vitro with conventional PA imaging systems, we have developed an adapted calibration method. Contrast agents in solution are injected in a dedicated non-scattering tube phantom imaged at different optical wavelengths. The calibration method uses a reference solution of cupric sulfate to simultaneously correct for the spectral energy distribution of excitation light at the tube location and perform a conversion of the tube amplitude in the image from arbitrary to spectroscopic units. The method does not require any precise alignment and provides quantitative PA spectra, even with non-uniform illumination and ultrasound sensitivity. It was implemented on a conventional imaging setup based on a tunable laser operating between 680 nm and 980 nm and a 5 MHz clinical ultrasound array. We demonstrated robust calibrated PA spectroscopy with sample volumes as low as 15 μL of known chromophores and commonly used contrast agents. The validated method will be an essential and accessible tool for the development of new and efficient PA contrast agents by improving their quantitative characterization.

Experimental demonstration of dispersion-diversity multicore fiber optical beamforming.

Phased array antenna (PAA) beam-steering in high radiofrequency bands will be key for upcoming 5G & Beyond wireless communications systems. As a compact and efficient solution to provide tunable beam steering simultaneously to parallel antenna distribution and connectivity, we experimentally demonstrate, for the first time to our knowledge, tunable optical beamforming implemented on a dispersion-diversity multicore optical fiber. The uniqueness of this fiber lies in the fact that each one of its seven step-index trench-assisted cores has been tailored to provide the required chromatic dispersion to enable tunable optical true-time delay line operation. Continuous 1D beam-steering was demonstrated by measuring the radiating pattern of an in-house fabricated 8-element PAA in an anechoic chamber at the radiofrequency of 26 GHz, sweeping the beam-pointing angle from -43° up to 40° by varying the operating optical wavelength from 1542.50 up to 1548.28 nm. Next-generation fiber-wireless communications systems will benefit from the demonstrated dispersion-diversity MCF optical beamforming in terms of flexibility, versatility, capacity, and connectivity along with reduced size, weight, and power consumption.

Quantum-Dash Laser-Based Tunable 50/75 GHz mmW Transport System for Future L-Band Networks

Tunable 50/75 GHz millimeter wave (mmW) transmission system has been demonstrated employing self-injection locked quantum-dash laser diode comb source (SIL QDCS) in the challenging 1610 nm region. The generated 50/75 GHz mmW beat-tones exhibited low phase noise of −64 dB/Hz at 1 kHz offset and narrow radio-frequency (RF) linewidths of ~1 kHz at the transmitter end. A 4 GBd (8 Gb/s) quadrature phase-shift keying (QPSK) data stream is successfully transmitted over both mmW carriers and across various channels <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">viz. 2</i> m wireless (WL) link, 11.6 km single-mode-fiber (SMF) – 2 m WL link, and 11.6 km SMF – 6 m free-space-optics (FSO) – 2 m WL link, thus affirming the potential of quantum-dash laser diode (QDLD) in high-frequency mmW applications. This work is a potential step towards realizing next-generation high-frequency tunable mmW optical-RF convergent hybrid networks operation in L-band, and one such possible proposal with a single QDCS is presented.

Control of carbon deposition over methane-fueled SOFCs through tuning the O/C ratio at the anode/electrolyte interface

Direct methane SOFCs can use abundant methane fuel economically and efficiently. Ni-based anode supports are deemed as the best candidate for practical applications owing to their low-cost, chemical compatibility, and high catalytic activity. However, the Ni-based anodes are prone to degradation due to carbon deposition using methane fuel. For the first time, this experimental study, coupling with simulation, discloses the direct causes of carbon deposition are highly depended on the O/C ratio at anode/electrolyte interface, and can be controlled through tuning the mass transfer within anodes, by means of optimizing pore structure of anode-support, methane concentration of input gas, and the operating current density. It is found that more methane transferred to the anode/electrolyte interface can improve power output while resulting in a low O/C ratio at the interface, thus causing carbon deposition. On the contrary, increasing the operating current density and lowering the input methane concentration can reduce the O/C ratio at the interface, thus the carbon deposition over Ni-based anodes can be diminished, and even eliminated. By experimental and numerical analysis, this work points out the O/C ratio is key to the carbon deposition of methane-fueled SOFC, and also provides a facile strategy to mitigate the carbon deposition through tuning anode microstructure and operation parameters such as operating current density, inlet methane concentration.

Tunable and Reconfigurable Logic Gates With Electrolyte-Gated Transistor Array Co-Integrated With Neuromorphic Synapses

A tunable and reconfigurable logic gates based on an electrolyte-gated transistor (EGT) array are co-integrated with neuromorphic synapses. The tunable and reconfigurable operations of the various logic gates are controlled by analog conductance modulation with nonvolatility of the fabricated EGT. The EGT array was uniformly fabricated on an entire 4-in wafer with the aid of CMOS compatible processes. Initiated-chemical vapor deposition (i-CVD) method was adopted for the deposition of the ultrathin polyethylene glycol dimethacrylate (pEGDMA) electrolyte layer. Therefore, the logic gates could be co-integrated with synaptic devices on the same in-plane substrate for integrability. Basic inverter operation with switching threshold tunability ranging from −1 to +1 V was demonstrated with good operational stability. In addition, NAND and NOR gate operations were realized by modulating the conductance level of a specified cell in the array configuration.

Watt-Level and Tunable Operations of 3 μm-Class Dysprosium ZrF₄ Fiber Laser Pumped at 1.69 μm

In this Letter, we used a home-made high-power and -brightness random Raman fiber laser (RRFL) at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.69~\mu \text{m}$ </tex-math></inline-formula> as the pump to demonstrate free-running and widely tunable operations of dysprosium (Dy)-doped ZrF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> fiber laser in the 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> mid-infrared (MIR) region. In an optimal F-P cavity arrangement, the maximum output power of 1.92 W with a slope efficiency of 18.3% was achieved at 2.992 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , indicating the highest power level of Dy fiber lasers under near-infrared (NIR) pumping. Using a modified scheme, in which a ruled diffraction grating (RDG) in a Littrow configuration was adopted as the wavelength selector and output coupler, the laser wavelength could be continuously tuned in the >700 nm range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.710\sim 3.415~\mu \text{m}$ </tex-math></inline-formula> , almost entirely covering the emission bands accessed by erbium (Er) and holmium (Ho) ions in this region. To our knowledge, this is the widest level (in terms of wavelength domain), to date, from not only a Dy laser, but a rare-earth-doped laser at any wavelengths. Additionally, the possibility of further extending the tuning range has been also predicted by preliminary modeling, validated by the experimental data. These results highlight the great potential of this NIR pumped Dy fiber laser for developing high-performance coherent source at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 3~\mu \text{m}$ </tex-math></inline-formula> .

(Industrial Electrochemistry and Electrochemical Engineering Division Student Achievement Award) Reactive Separations to Remediate and Valorize Nitrogen-Polluted Wastewaters

Anthropogenic perturbations to the global nitrogen cycle due to industrial Haber-Bosch fertilizer production threaten large-scale food production, energy inputs for chemical manufacturing, and protection of water quality. Enabling a sustainable food-energy-water nexus requires feeding a growing population while minimizing environmental impacts. In this talk, I introduce Electrodialysis and Nitrate Reduction (EDNR), a novel electrochemical process that couples water purification with electrified ammonia production from nitrogen-polluted wastewaters.The EDNR reactor consists of three chambers and operates in two stages (Figure 1), with the influent entering the middle chamber and products recovered from the left and right chambers. In Stage 1, influent nitrate () and ammonium () are separated via electrodialysis (ED) and ammonia is recovered in the right chamber. In Stage 2, ammonia is synthesized from the electrochemical nitrate reduction (NR) in the left chamber. EDNR enables rational design of electrochemical environments in each chamber (e.g., electrolyte pH; cationic and anionic constituents; species concentrations) through tunable operating parameters such as applied potential, electrolyte flow rate, and duration of the ED and NR stages. This modular, tunable design facilitates robust water remediation and ammonia production from wastewaters of transient composition.We have demonstrated proof-of-concept EDNR reactors using titanium foil (left chamber, NR electrode), Ti/IrO2-Ta2O5 mesh (left and middle chambers, ED electrode), and platinum foil (right chamber, ED electrode). With recirculating batches of simulated wastewater (100 ppm + 500 ppm ), 75% influent NH4 + was recovered into the right chamber and 25% influent was converted to in the left chamber after three EDNR cycles. As the rate-limiting stage, NR on titanium merited further fundamental investigation. In particular, the reasons for titanium’s electrocatalytic NR performance remain largely unclear to date, especially regarding the role of the role of titanium hydride (TiHx, 0<x<2), which forms during NR. Rationally implementing Ti-catalyzed NR requires improved understanding of how near-surface Ti-hydride forms and influences NR activity and selectivity. Through systematic synchrotron x-ray characterization of Ti-hydride electrodes, electrochemical testing, and density functional theory calculations, we found that near-surface hydride content plays a relatively minor role in steering NR performance compared to applied potential and electrolyte effects. Put in context, our results help prioritize how EDNR operation can be optimized for ammonia production. As a validated platform with ongoing work to improve performance, EDNR shows great potential in realizing sustainable and distributed water remediation and ammonia production.

Cylindrical Metalens for Generation and Focusing of Free-Electron Radiation.

Metasurfaces constitute a powerful approach to generate and control light by engineering optical material properties at the subwavelength scale. Recently, this concept was applied to manipulate free-electron radiation phenomena, rendering versatile light sources with unique functionalities. In this Letter, we experimentally demonstrate spectral and angular control over coherent light emission by metasurfaces that interact with free-electrons under grazing incidence. Specifically, we study metalenses based on chirped metagratings that simultaneously emit and shape Smith–Purcell radiation in the visible and near-infrared spectral regime. In good agreement with theory, we observe the far-field signatures of strongly convergent and divergent cylindrical radiation wavefronts using in situ hyperspectral angle-resolved light detection in a scanning electron microscope. Furthermore, we theoretically explore simultaneous control over the polarization and wavefront of Smith–Purcell radiation via a split-ring-resonator metasurface, enabling tunable operation by spatially selective mode excitation at nanometer resolution. Our work highlights the potential of merging metasurfaces with free-electron excitations for versatile and highly tunable radiation sources in wide-ranging spectral regimes.

Energy-efficient synaptic devices based on planar structured h-BN memristor

Synapses with short-term plasticity (STP) and long-term plasticity (LTP) behaviors are the key factors for the development of complex neuromorphological systems. Two dimensional (2D) materials have shown great potential at synaptic devices because of their unique properties. In this work, synaptic devices with a planar structure using insulated 2D hexagonal boron nitride (h-BN) as resistance switching (RS) medium were studied for the first time. Different from vertical h-BN synaptic devices, planar h-BN synaptic devices support in-plane transport of metal ions through nanoscale channels, which weakens the influence of material defects, morphology, thickness and uniformity on device performance. The Ag/h-BN/Ag planar structured synaptic devices exhibited low switching voltage (< 1 V), high On/Off ratio (> 108), wide range of tunable operation current (0.1 nA–1 mA), and coexistence of volatile (SET power ≤ 50 nW) and non-volatile (SET power ≥ 700 nW) RS characteristic. In addition, the multi-stage resistance states could be modulated by setting different SET power. The device efficiently mimicked the STP and LTP synaptic functions, and the energy consumption per synaptic event was as low as 170 fJ/spike for STP and 540 fJ/spike for LTP, respectively. In addition, the multi-memory states of synaptic devices could be obtained by adjusting the postsynaptic current (PSC).

Ultrawideband Frequency Synthesis Using the Compact Tunable Transmission Line (CTTL)

Due to the rapid adoption of mmW bands for 5G communications, the complexity of transceiver systems must increase to operate over ever further separated frequency bands. In more traditional sub-6-GHz bands, software-defined radio (SDR) techniques allow for unified, multiband RF front ends; however, maintaining this ultrawideband or ultrawide tunable operation at mmW frequencies poses many challenges. One such challenge is ultrawideband mmW frequency synthesis, a challenge for which we present a new lumped/distributed tunable LC structure, the compact tunable transmission line (CTTL). In this article, we observe how the CTTL enables a state-of-the-art −203-dBc/Hz FOM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{T}$ </tex-math></inline-formula> multioctave tunable mmW VCO, achieving a >4 octave tuning range with output up to 51 GHz. To analyze the CTTL in comparison to conventional tunable LC VCOs, we develop a new phase noise and oscillator figure-of-merit (FOM) model that provides an analysis framework for wide LC tuning. This new model is verified against simulation for conventional tuning and then is used to show how the CTTL provides a higher <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> and, therefore, better oscillator performance compared with existing LC tuning methods in the case of multioctave frequency synthesis. This analysis is then confirmed by the measured results of the manufactured CTTL VCO.

Acoustic performance of sonic metacage consisting of Helmholtz’s resonator columns with internal partitions

The quest for a quiet environment has led to numerous efforts to shield noise at the source or develop an efficient acoustic proof system. We present a three-dimensional sonic crystal acoustic metacage structure for hybrid purposes of noise shielding and natural ventilation. The metacage prototype comprises sixteen cylindrical sonic crystal column structures (C2 and K2 types) placed at a regular distance along the circular periphery. Each column consists of two semi-cylindrical long cavities with slit channels, which allow the sound wave to enter the Helmholtz cavities and are responsible for sound attenuation. Numerical simulations and experimental measurements are used to demonstrate the efficacy of the acoustic metacage. Experimental measurements display the maximum sound insertion loss values of 20.8 dBA and 11.9 dBA for K2 type sonic crystal metacage, respectively, when the sound source is placed outside and inside the cage. For C2 type sonic crystal metacage, two sound insertion loss peaks with maximum values of 19.8 dBA and 10.4 dBA have been achieved at 2500 Hz when the sound source is kept outside and inside. The numerical results suggest the frequency tuning capabilities by adjusting the metacage size. Also, the modular design features enable the tunable operating frequency to meet different requirements.

Intrinsic variation effect in memristive neural network with weight quantization

To analyze the effect of the intrinsic variations of the memristor device on the neuromorphic system, we fabricated 32 × 32 Al2O3/TiO x -based memristor crossbar array and implemented 3 bit multilevel conductance as weight quantization by utilizing the switching characteristics to minimize the performance degradation of the neural network. The tuning operation for 8 weight levels was confirmed with a tolerance of ±4 μA (±40 μS). The endurance and retention characteristics were also verified, and the random telegraph noise (RTN) characteristics were measured according to the weight range to evaluate the internal stochastic variation effect. Subsequently, a memristive neural network was constructed by off-chip training with differential memristor pairs for the Modified National Institute of Standards and Technology (MNIST) handwritten dataset. The pre-trained weights were quantized, and the classification accuracy was evaluated by applying the intrinsic variations to each quantized weight. The intrinsic variations were applied using the measured weight inaccuracy given by the tuning tolerance, RTN characteristics, and the fault device yield. We believe these results should be considered when the pre-trained weights are transferred to a memristive neural network by off-chip training.

Performing broadband and tunable mathematical operations based on acoustic reconfigurable metasurfaces

Acoustic metasurfaces can manipulate acoustic waves at subwavelength scales, thus proved to have advantages in constructing novel compact analog computing (CAC) systems. Here, we design an acoustic CAC system based on a nondispersive focusing metasurface (FM) and a reconfigurable reflective metasurface (RRM), which can perform broadband and tunable mathematical operations. The nondispersive FM consists of the sandwich-like-structured units, featuring the non-dispersive effective refractive indexes and high transmission efficiency. The RRM is formed by the amplitude modulator (AM) and π/2-phase modulator (π/2-PM), where the moving regions in the AM and π/2-PM can control the reflection amplitude and phase distribution of RRM, respectively. The numerical results show that the proposed CAC system can perform spatial differentiation and integration on the incident acoustic wave in the frequency range from 3.0 kHz to 3.9 kHz. This work promises the broadband and tunability that are critical for practical computing devices, paving the way towards acoustic computing applications, wave processing and manipulations.

Theoretical and simulation study of dynamically tunable sensor based on liquid crystal-modulated Fano resonator in terahertz band

A liquid crystal-modulated Fano resonator is designed, which has high sensitivity, tunable operating band and adjustable sensing range at the same time. The Fano resonator is constructed by attaching a ring above a main channel and connecting a groove beneath it. With the interaction of the discrete mode provided by the ring and the continuous mode provided by the groove, a Fano resonator can be produced with a pretty high sensitivity. Moreover, by infiltrating liquid crystals into the inner layer of the ring cavity, the resonant frequency of the Fano resonator can be shifted freely by adjusting the biasing voltage across the liquid crystals. The margin of the shifted frequency can achieve 57 GHz for the first-order resonance around 1.609 THz, and 140 GHz for the second-order resonance around 2.694 THz, respectively. Meanwhile, the liquid crystal infiltrated Fano resonator achieves a favorable sensitivity in terms of figure of merit (FOM) as high as 6.02 × 104. The novel Fano resonator is pretty attractive for sensing applications that require high sensitivity, tunable operating band and adjustable sensing range at the same time, paving the way for developing flexible terahertz systems in the coming future.

Spectral broadening of a mixed Nd: CYGA crystal with tunable laser operation beyond 1100 nm.

A broader emission band of the novel Nd: CaY0.9Gd0.1AlO4 (Nd: CYGA) mixed crystal was proved by the introduction of Gd3+ ions in Nd: CaYAlO4 (Nd: CYA) crystal, and a diode-pump tunable Nd: CYGA laser operation was achieved successfully. Due to the broad emission spectrum with the full width at half maximum (FWHM) of 23 nm, a tuning range of 32 nm from 1075 nm to 1107 nm was achieved, and the results were considered to be the first time for Nd-doped crystals to be tuned to such a long wavelength at 1107 nm, which promotes the further development of near-infrared tunable lasers. The maximum output power was 1.05 W at the center wavelength of 1081.4 nm, corresponding to the slope efficiency of 26.6%. Furthermore, we also demonstrated a continuous-wave 1105 nm laser with the output power of 53 mW. Our work indicates that Nd: CYGA crystal is a potential Nd-doped gain medium for generating all-solid-state near-infrared lasers.

Varactor-Controlled SRR-Integrated Frequency-Reconfigurable Multifunctional Vivaldi Antenna: A proposed concept

A novel multifunctional exponentially tapered slot (Vivaldi) antenna exhibiting tunable frequency-notched and tunable narrow-band operation is proposed in this article. Integration of multiple varactor-coupled split-ring resonators (VC-SRRs) into the feed region of the Vivaldi yields a wideband tunable frequency-notched response upon suitable tuning of the varactor diodes. Furthermore, the VC-SRR-loaded Vivaldi, when augmented with suitably located switches connecting the slot line, yields a tunable narrow-band performance over an octave bandwidth centered around 5.25 GHz.

Continuous Real-Time Circuit Reconfiguration to Maximize Average Output Power in Cognitive Radar Transmitters

A spectrum sharing radar can be guided by a cognitive decision process to determine the optimal radar operating frequency as the spectral environment changes. This decision process utilizes spectrum sensing or spectral prediction to determine the optimal radar transmission for a given situation. The radar transmitter power amplifier performance varies with frequency and bandwidth of the applied waveform, thus adaptive impedance tuners are useful in maximizing the transmitted power and radar range as the transmission frequency range is varied. Since high power handling is required in radar transmissions, and mechanically actuated impedance tuners presently demonstrate the best power handling, the time required to tune is often orders of magnitude greater than the pulse repetition interval. As such, the relatively lengthy impedance tuning operations should be guided to maximize the average output power as the system transitions between different center frequencies, bandwidths, and waveforms over time. This article presents an algorithm that performs impedance tuning with an evanescent-mode cavity tuner based on an average performance gradient computed for multiple transmit pulses. Comparison of test results with traditionally measured amplifier load-pull data shows that the transmitter is effectively optimized for maximum average output power.

Ultrafast operation on a novel Nd:LaMgAl11O19 disordered crystal laser

A 5 at.% Nd:LaMgAl11O19 (Nd:LMA) disordered crystal was successfully fabricated by the Czochralski method. A continuous wide tuning range of roughly 38 nm (1051 nm ∼ 1089 nm) was obtained for the tuning operation. The performance of diode-pumped passively mode-locked Nd:LMA laser was successfully achieved for the first time. By employing a semiconductor saturable absorber mirror (SESAM), a continuous-wave mode-locked (CWML) laser with pulse duration of 11.2 ps was delivered, corresponding repetition rate was 55 MHz. The maximum average output power was 122 mW at a central wavelength of 1054.7 nm. These results indicated that the Nd:LMA was a promising laser material.