Diode Output Research Articles

High thermal stability and high-performance efficiency capability of light sources–based rate equation models in optical fiber transmission systems

Abstract This paper clarified the high thermal stability and high-performance efficiency capability of silicon light sources–based rate equation models in the optical fiber transmission systems. The laser diode and light emitting diode output power variations are measured with input injection current under various ambient temperature effects. The light source differential quantum efficiency is demonstrated for both LED and laser diode with different injection input current and various temperature variations. The LED/laser diode light source external efficiency is clarified with different injection input current and various temperature variations. The LED/laser diode light source total efficiency is measured with different injection input current and various temperature variations. As well as the laser diode and light emitting diode, threshold current variations are demonstrated clearly with input injection current under room temperature and various spectral thermal effects. The laser diode and light emitting diode power dissipation variations are measured with input injection current under room temperature and various spectral thermal effects.

Design and Implementation of a Power Semiconductor-Based Switching Mode Laser Diode Driver.

Fiber lasers are commonly used in many industrial applications, such as cutting, welding, marking, and additive manufacturing. In a fiber laser system, the driver of a pumping source using a laser diode (LD) module and its dynamic control capability directly affect the performance of the fiber laser system. The commercial design of pumping source drivers for high-power fiber lasers is mainly based on a linear-type DC power supply, which has two major drawbacks, i.e., lower efficiency and bulk. In this regard, this paper proposes for the first time a new design approach with a programmable switching mode laser diode driver using a power semiconductor device (PSD)-based full-bridge phase-shifted (FB-PS) DC-DC converter for driving a 200 W optical power laser diode module. In this paper, the characteristics of a laser diode module and the system configuration of the proposed laser diode driver are first introduced. Then, a current control scheme using the concept of phase angle shifting to achieve a fast dynamic current tracking feature is explained. The proposed current control technique with a fully digital control scheme is then addressed. Next, dynamic mathematical models of the laser diode driver system and controllers are derived, and the quantitative design detail of the controller is presented. To confirm the correctness of the proposed control scheme, a simulation study on a typical control case is performed in PSIM 9.1 software environment. To verify the effectiveness of the proposed LD driver, a digital signal processor is then used as the control core to construct a hardware prototype implementation for performing experimental tests. Results obtained from simulation and hardware tests show highly satisfactory driving performances in the laser diode's output current command tracking control.

Compact optically pumped magnetometer light source stabilization with regulated feedbacks

Optically pumped magnetometers (OPMs) are very sensitive to magnetic field and have the advantages of portability and low cost. In the miniaturized OPM, a vertical cavity surface emitting laser (VCSEL) diode is utilized to generate the laser light for both pumping and probing, the stability of which significantly affects the sensor’s performance. Therefore, precisely control of the light source is required. This paper proposes a novel method of stabilizing the laser diode output by using a close-loop control with two feedbacks, namely: the measurement of the diode temperature and the output signal of the photodetector. The control coefficients of these two feedbacks are regulated dynamically according to the operating state of the OPM. The experimental results show that after operating for 1000 s, the Allan deviation of the photodetector signal is 3.98 ×10−4 for the proposed method, as a comparison, the Allan deviation is 2.56 ×10−2 for a conventional close-loop control technology. The proposed method performs better for long-time operations. A compact OPM is developed and tested, which employ the proposed scheme to control the output of the VCSEL diode. The experiment results show that a sensitivity of 16 fT/Hz1/2 @ 10 Hz is achieved and the OPM can operate stably in a long time.

Five parameters extraction of single diode PV model by metaheuristic optimization method by identified built-up data

Precision calculation of unknown photovoltaic (PV) modules or single diode models for PV cell specifications under various environmental conditions is needed to build a sunlight-based PV framework. Installing a PV system requires knowledge of all parameters, modeling, and optimization techniques because PV system analysis and configuration help generate renewable energy. This concept requires accurate modeling and calculation of identified and unknown parameters. The single-diode model is simple and accurate for different mathematical equations. Streamlining calculations requires distinguishing this nonlinear model. The current investigation calculated five unknown parameters and compared them with particle swarm optimization (PSO) and wind-driven optimization (WDO) optimization results. The said approach utilizes MATLAB software, analytical as well as optimization methods, and manufacturing data. The suggested method is simple, fast, and accurate for calculating diode ideality factor (A), output currents (Io), series resistance (Rs), Shunt resistance (Rsh), and photocurrent (Iph).

Design for a low-cost heterodyne frequency domain-diffuse optical spectroscopy system.

A design for a low-cost, heterodyne, frequency domain-diffuse optical spectroscopy system is presented and validated. The system uses a single wavelength of 785 nm and a single detector to illustrate the capability, but is built in a modular fashion to make it easily expandable to additional wavelengths and detectors. The design incorporates methods to allow software-based control over the system operating frequency, laser diode output amplitude, and detector gain. Validation methods include characterization of electrical designs as well as determination of the system stability and accuracy using tissue-mimicking optical phantoms. The system requires only basic equipment for its construction and can be built for under .

Microcontroller-Based Thermoelectrically Stabilized Laser Diode System

This work aims to describe the development of a prototype laser diode system along with its driver circuit and a stable microcontroller-based thermo-electric cooling system. The laser diode driver circuit was designed and simulated by using NI Multisim. The driver circuit was built using two LM317 ICs to control the voltage across the laser diode and current through the laser diode. The laser diode output power varies by varying the current across the laser diode through the driver circuit. The temperature of the laser diode rises with time, affecting the output power of the laser diode during a long period of operation. A microcontroller-based cooling system was designed and fabricated using thermoelectric coolers. The microcontroller controls the cooling system ON/OFF period to maintain the laser diode at a particular temperature by removing the excess heat produced during the lasing action. The laser diode with a microcontroller-based cooling system shows that the laser diode output power remains stable during a long period of operation.

Control of Ni/β-Ga2O3 Vertical Schottky Diode Output Parameters at Forward Bias by Insertion of a Graphene Layer.

Controlling the Schottky barrier height () and other parameters of Schottky barrier diodes (SBD) is critical for many applications. In this work, the effect of inserting a graphene interfacial monolayer between a Ni Schottky metal and a β- semiconductor was investigated using numerical simulation. We confirmed that the simulation-based on Ni workfunction, interfacial trap concentration, and surface electron affinity was well-matched with the actual device characterization. Insertion of the graphene layer achieved a remarkable decrease in the barrier height (), from 1.32 to 0.43 eV, and in the series resistance (), from 60.3 to 2.90. However, the saturation current () increased from to (A/cm2). The effects of a graphene bandgap and workfunction were studied. With an increase in the graphene workfunction and bandgap, the Schottky barrier height and series resistance increased and the saturation current decreased. This behavior was related to the tunneling rate variations in the graphene layer. Therefore, control of Schottky barrier diode output parameters was achieved by monitoring the tunneling rate in the graphene layer (through the control of the bandgap) and by controlling the Schottky barrier height according to the Schottky–Mott role (through the control of the workfunction). Furthermore, a zero-bandgap and low-workfunction graphene layer behaves as an ohmic contact, which is in agreement with published results.

Abstracts from the World Federation for Laser Dentistry—Asia Pacific Division Virtual Conference July 16–17, 2021

Abstracts from the World Federation for Laser Dentistry—Asia Pacific Division Virtual Conference July 16–17, 2021

Penstabilan Daya Dioda Laser Secara Otomatis Sebagai Sumber Cahaya Pada Sensor Optik

Since the invention of laser beam in the 1960s, the application extends to all areas, even revolutionizedseveral fields of technology. Laser is the most widely used in electronic applications as the laser diode. Theimportant application of laser diodes is as a light source for an optical sensor on the sensor either directly orusing the optical fiber. In the application as light source in optical sensor applications, especially on the principleof change in intensity, the stability of laser diode output power is a variable that should be received the necessaryattention. So that, it is needed a Power Control which will automatically control the output power of laser beam.In this study we designed the power stability circuits using the APC LD 2000. The measurement results show thatthe stability strongly depended on the injection electric current area. When it was be operated in the largerinjection electric current area, the laser diode power tobecame larger and more stable than using with themedium or the lower injection electric current.

Analysis Of Power Generation Photovoltaic Array 9×10 Wp Under Shading Effect

There are several problems that can interfere with the performance of large-scale PV. One that enhances PV performance is shading on a PV module, that make interferes PV performance. This research studied about the effect of shading on the performance of large-scale PV systems through testing a 9 × 10 Wp miniature PV array and simulation using Matlab software. The use of diodes on a PV module can be done to prevent damage to the PV module due to shading. Through the power-voltage (P-V) and current-voltage (I-V) characteristic curves the effect of shading and the use of bypass and blocking diodes can be determined. Shading effect gave in a decrease in power in the PV module. From the results of this study note that the bypass diode and blocking diode output power generated by the PV module can be optimal.

On the impact of LED power uncertainty on the accuracy of 2D and 3D Visible Light Positioning

This paper presents a simulation study of the impact of Light Emitting Diode (LED) output power uncertainty on the accuracy of Received Signal Strength (RSS)-based two-dimensional (2D) and three-dimensional (3D) Visible Light Positioning (VLP). The actual emitted power of a LED is never exactly equal to the value that is tabulated in the datasheet, with possible variations (or tolerances) up to 20%. Since RSS-based VLP builds on converting estimated channel attenuations to distances and locations, this uncertainty will impact VLP accuracy in real-life setups. For 2D, a typical configuration with four LEDs is assumed here, and a Monte-Carlo simulation is executed to investigate the distribution of the resulting positioning errors for four tolerance values at seven locations. It is shown that median errors are the highest just below the LEDs, when using a traditional Least-Squares minimization metric. When tolerance values on the LED power increase from 5% to 20%, median errors vary from at most 2 cm to at most 10 cm. Maximal errors can be as high as 17 cm just below the LED, already for tolerance values of only 5%, and increase up to 40 cm for tolerance values of 20%. An alternative cost metric using normalized Least-Squares minimization makes the errors spatially more homogeneously distributed and reduces them by 35%. For a 3D case, median errors of around 5 cm for a tolerance value of 5% increase to as much as 22 cm for a tolerance value of 20%. As the receiver heights increase, positioning errors decrease significantly.

The study of operation modes of the self-magnetically insulated ion diode.

The operation modes of a self-magnetically insulated ion diode were studied. The plasma formation at the anode surface was found to be accompanied by an electron leakage current due to the bipolar high voltage pulse. The emitting anode surface and ion beam density distribution were investigated at the ion diode output area. The characteristics of the electron leakage current are presented depending on the ion diode operation mode. The area of the emitting anode surface was approximately 25%-30% of the total anode area. The electron leakage current reaches up to 6.5 kA in the ion diode.

半导体激光器光束匀化系统的光学设计

In order to improve the uniformity of the laser diode beam, a homogenization system combined aspheric and microlens lens array was designed. The aspheric homogenization lens was designed by using ray tracing in the direction of the fast axis, and the microlens array was used to segment and overlay the beam in the slow axis direction. Laser diode output beam passed through the honogenizing system, the energy homogenization of the square spot can be obtained on the target surface. By using Zemax optical software to simulate the single tube and array, the feasibility of the optical system was verified. The influence of target dynamic range change on uniformity was obtained, and the influence of the change of the distance between micro-cylindrical lens arrays and the rotation of fast-axis homogenizing lens on the uniformity was studied. The homogeneity of single tube and laser array on the output surface was over 90%, and the energy efficiency was 95.4% and 96.2%, respectively. The design results have certain reference value for the beam homogenization of laser diode.

On the Theory of Compensated Bipolar Beams

One-dimensional flows of charged particles with opposite charge signs moving in the same direction are investigated, including an electron diode (or a diode with negative ions) shot by positive ions and an ion diode pierced by relativistic electrons. Variants with different degrees of space charge compensation at the diode output and the case of full charge, current, and magnetic-field (electromagnetic) compensation are discussed.

Iodine-stabilized single-frequency green InGaN diode laser.

A 520-nm InGaN diode laser can emit a milliwatt-level, single-frequency laser beam when the applied current slightly exceeds the lasing threshold. The laser frequency was less sensitive to diode temperature and could be finely tuned by adjusting the applied current. Laser frequency was stabilized onto a hyperfine component in an iodine transition through the saturated absorption spectroscopy. The uncertainty of frequency stabilization was approximately 8×10-9 at a 10-s integration time. This compact laser system can replace the conventional green diode-pumped solid-state laser and applied as a frequency reference. A single longitudinal mode operational region with diode temperature, current, and output power was investigated.

Simulation of high-power 8-mm band avalanche-oscillator diodes

The results of computer simulation of 8-mm band high-power avalanche-oscillator diodes (AOD) based on abrupt reverse biased p–n junctions with constant voltage have been presented. It is shown that AOD synchronously generate two oscillations in p- and n-regions of p–n junction, respectively. A technique is proposed for determining the parameters that ensure the diode operation in the mode of coherent oscillations. It is shown that the diode output power in this operation mode increases at the expense of summing-up the electron and hole components. The dynamic range of output power and the electronic efficiency are also determined.

Enhancement of Weak Lidar Signal Based on Variable Frequency Resolution EMD

A new high-resolution approach is presented for noise reduction in lidar signals using variable frequency resolution empirical mode decomposition. Avalanche photo diode (APD) output single-channel low signal-noise ratio (SNR) real data are decomposed into multi-scale components and reconstructed with less noise. The key is to have a fine scale signal in each component. Based on the non-symmetric signal and the symmetric noise on the timeline in APD data, the proposed approach is highly effective in distinguishing between signal and noise by choosing an appropriate frequency resolution, compared with the conventional multiscale method. Real examples are examined with real data, signal separation is obtained in the components, and the −22.4 dB low SNR has been enhanced by the component product.

Monolithic all-fiber repetition-rate tunable gain-switched single-frequency Yb-doped fiber laser.

We report a monolithic gain-switched single-frequency Yb-doped fiber laser with widely tunable repetition rate. The single-frequency laser operation is realized by using an Yb-doped distributed Bragg reflection (DBR) fiber cavity, which is pumped by a commercial-available laser diode (LD) at 974 nm. The LD is electronically modulated by the driving current and the diode output contains both continuous wave (CW) and pulsed components. The CW component is set just below the threshold of the single-frequency fiber laser for reducing the requirement of the pump pulse energy. Above the threshold, the gain-switched oscillation is trigged by the pulsed component of the diode. Single-frequency pulsed laser output is achieved at 1.063 μm with a pulse duration of ~150 ns and a linewidth of 14 MHz. The repetition rate of the laser output can be tuned between 10 kHz and 400 kHz by tuning the electronic trigger signal. This kind of lasers shows potential for the applications in the area of coherent LIDAR etc.

A Novel Buck–Boost AC–AC Converter With Both Inverting and Noninverting Operations and Without Commutation Problem

This paper proposes a new type of ac–ac converter which can operate as traditional noninverting buck and boost converters, and inverting buck–boost converter as well. The proposed converter uses six unidirectional current flowing and bidirectional voltage blocking switches, implemented by six reverse blocking insulated-gate bipolar transistors (IGBTs) or series mosfet –diode pairs, two input and output filter capacitors, and one inductor. It has no shoot-through problem of voltage source (or capacitor) even when all switches are turned-on, and therefore, pulsewidth modulation dead-times are not needed resulting in high-quality waveforms, and solves the commutation problem without using bulky and lossy RC snubbers or dedicated soft-commutation strategies. It has smaller switching losses because only two switches out of six are switched at high frequency during each half-cycle of input voltage, and it can use power MOSFETs as body diode never conducts, making it immune from mosfet failure risk which otherwise may occur due to poor reverse recovery problem of body diode. The noninverting buck–boost mode of the proposed converter can be used in applications with both step-up and step-down demand, while the inverting buck–boost mode can also be used in its application as dynamic voltage restorer. Detailed analysis of the proposed converter is given, and experimental results are also provided.

Low-level laser therapy/photobiomodulation in the management of side effects of chemoradiation therapy in head and neck cancer: part 2: proposed applications and treatment protocols.

There is a large body of evidence supporting the efficacy of low-level laser therapy (LLLT), more recently termed photobiomodulation (PBM) for the management of oral mucositis (OM) in patients undergoing radiotherapy for head and neck cancer (HNC). Recent advances in PBM technology, together with a better understanding of mechanisms involved and dosimetric parameters may lead to the management of a broader range of complications associated with HNC treatment. This could enhance patient adherence to cancer therapy, and improve quality of life and treatment outcomes. The mechanisms of action, dosimetric, and safety considerations for PBM have been reviewed in part 1. Part 2 discusses the head and neck treatment side effects for which PBM may prove to be effective. In addition, PBM parameters for each of these complications are suggested and future research directions are discussed. Narrative review and presentation of PBM parameters are based on current evidence and expert opinion. PBM may have potential applications in the management of a broad range of side effects of (chemo)radiation therapy (CRT) in patients being treated for HNC. For OM management, optimal PBM parameters identified were as follows: wavelength, typically between 633 and 685nm or 780-830nm; energy density, laser or light-emitting diode (LED) output between 10 and 150mW; dose, 2-3J (J/cm(2)), and no more than 6J/cm(2) on the tissue surface treated; treatment schedule, two to three times a week up to daily; emission type, pulsed (<100Hz); and route of delivery, intraorally and/or transcutaneously. To facilitate further studies, we propose potentially effective PBM parameters for prophylactic and therapeutic use in supportive care for dermatitis, dysphagia, dry mouth, dysgeusia, trismus, necrosis, lymphedema, and voice/speech alterations. PBM may have a role in supportive care for a broad range of complications associated with the treatment of HNC with CRT. The suggested PBM irradiation and dosimetric parameters, which are potentially effective for these complications, are intended to provide guidance for well-designed future studies. It is imperative that such studies include elucidating the effects of PBM on oncology treatment outcomes.