Laser Module Research Articles

Signal strength in FSO communication channels based on directly measured modulated laser with dual drive Mach–Zehnder modulators (MZMs) measured

Abstract The work clarified directly measured modulated laser with dual drive measured Mach–Zehnder modulators for signal strength in free space optics (FSO) channel. Peak power after free space communication channel at various propagation distances is measured in the optical time domain. As well as the signal level amplitude quality and data error rates after light detector at various propagation distances are also measured in the time bit period. The directly measured modulated laser with dual drive measured Mach–Zehnder modulators for signal strength in FSO communication channels is stimulated with optisystem program version 13. Peak signal power after free space communication channel at various propagation distances is measured in the optical time domain. The optimum peak signal power is achieved at 10 km distance with a value of 4.328 W. The signal level amplitude quality and data error rates after light detector at various propagation distances are also measured in the time bit period. The optimum Q level and BER level are clarified at 10 km distance with the values of 23.1164 for signal quality and 1.439 × 10−118 for minimum data error rates.

High Stability PGC-EFA-DCM Demodulation Algorithm Integrated With a PID Module

Phase generated carrier (PGC) demodulation technology has been widely used in fiber-optic interferometric sensors while nonlinearity is always accompanying with the scheme. We propose a highly stable PGC demodulation algorithm combining internal modulation, ellipse fitting algorithm (EFA), phase modulation depth ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> ) self-calibration and differential-cross-multiplying (DCM). A low frequency triangular signal is added to the laser modulation, which ensures the effectiveness of the EFA under small signal condition. And the real-time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> value is calculated by using the ellipse fitting parameters and calibrated to the optimal value of 2.63 rad by a closed loop proportion integration differentiation (PID) module. Furthermore, nonlinear distortions are suppressed by the EFA. Experimental results show that the signal-to-noise and distortion ratio (SINAD) and total harmonic distortion (THD) of the proposed scheme are improved by 13.61 dB and 0.12% than the conventional PGC-DCM algorithm. The standard deviation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> decreased from 0.0178 rad to 0.0058 rad in 1024 seconds. The dynamic range, linearity and phase resolution of the system reach 117.73 dB @ 1 kHz, 99.99% and 4.6 μrad/√Hz, respectively.

Copper laser patterning on a flexible substrate using a cost-effective 3D printer

We studied the cost effective direct laser patterning of copper (Cu) on thin polyimide substrates (PI thickness: 12.5–50 µm) using a 405 nm laser module attached to an inexpensive 3D printer. The focal length of the laser was intentionally controlled to reduce defects on patterned Cu and surface damage of PI under predetermined process conditions. The appropriate focal length was examined at various focal distances. Focal distances of − 2.4 mm and 3 mm were found for the shorter focal length (SFL) and longer focal length (LFL), respectively, compared to the actual focal length. This resulted in clean Cu line patterns without line defects. Interestingly, the SFL case had a different Cu growth pattern to that of LFL, indicating that the small difference in the laser incident angle could affect Cu precursor sintering. Cu square patterns had a lower resistivity of 70 μΩ·cm for an LFL after three or four laser scans, while the SFL showed a resistivity below 48 μΩ·cm for a one-time laser scan. The residues of the Cu precursor on PI were easily removed with flowing water and normal surfactants. However, the resistivity of the patterns decreased after cleaning. Among the scan gaps, the Cu square pattern formed at a 70 μm scan gap had the lowest sheet resistance and the least change in resistance from around 4 to 4.4 Ω/ϒ after cleaning. This result implies that the adhesion of the patterned Cu could be improved if the coated Cu precursor was well sintered under the proper process conditions. For the application of this method to bioelectronics, including biosensors, LEDs were connected to the Cu patterns on PI attached to the arm skin and worked well, even when the substrate PI was bent during power connecting.

Laser-induced thermography: An effective detection approach for multiple-type defects of printed circuit boards (PCBs) multilayer complex structure

Due to the multilayer complex structure characteristics of printed circuit boards (PCBs), multiple types of defects (Such as delamination, debonding, and breakdown damage) are likely to occur during processing and use, which affects the performance of the entire electronic component. In the present study, infrared thermography was employed to detect the multiple-type defects of PCBs. Initially, the thermal-wave diffusion model for a four-layer PCBs simulation structure induced by a sinusoidal modulation laser was built. Meanwhile, the finite element methods were utilized to solve the thermal-wave mathematical model and analyze the behavior of thermal-wave diffusion. Furthermore, a four-layer copper-clad laminate structure with flat bottom holes (FBHs) simulated delaminate defect was designed and manufactured. Finally, laser-induced lock-in thermography was adopted to detect the multiple types of actual defects (breakdown damage, delamination defect, fold defect, and micropore) of rigid or rigid-flexible PCBs. The phase characteristic image realizes the effective detection of PCBs delamination defects with a depth of 1.2 mm and microporous defects with a depth of 400 μm. The experimental results demonstrated that laser-induced thermography is suitable to detect the multiple-type defects of PCBs.

MIL-68(Al) and MIL-68(Fe) as broadband optical modulators for Q-switching fiber lasers operating at 2 and 2.9 μm

We investigated 2 and 2.9 μm mid-infrared fiber lasers passively Q-switched by MIL-68(Al) and MIL-68(Fe), which were fabricated via the hydrothermal method. The modulation depth of MIL-68(Al) was found to be 9.12% at 1.99 μm. And the modulation depths of MIL-68(Fe) were found to be 18.89% and 15.79% at 1.99 μm and 2.87 μm, respectively. We report Q-switching pulse generation in both Tm3+-doped and Ho3+/Pr3+ co-doped fiber lasers by using the as-prepared MIL-68 (M, M = Al3+, Fe3+) as SAs. The center wavelengths were at 1.99 μm and 2.87 μm, respectively. These results indicate that MIL-68(M) has wideband nonlinear optical properties and promising application prospects in the field of optical modulators at 2- and 2.9-μm mid-infrared waveband. Work clearly accessible to a broad readership.

The Motion of a Charged Particle in the Electromagnetic Field of a Polarization-Modulated Wave

This article presents an exact solution of the equation of motion of a charged particle in the electromagnetic field of a high-intensity polarization-modulated wave. Expressions for the average kinetic energy of a particle without regard to its rest energy in the case of circular and linear polarization of a modulated wave are obtained. The motion of a charged particle in the field was analyzed and expressed in terms of dependences of its average kinetic energy on the electromagnetic wave intensity and on various types of modulation depths. The contribution of each type of modulation to the energy characteristics of a charged particle was demonstrated. Solving the equation of motion of a charged particle in the electromagnetic field of a plane wave opens up possibilities for various applications related, in particular, to various developments of multi-frequency lasers and laser modulation technology. This study was proposed due to the growing interest in experiments using high-intensity femtosecond laser radiation and high-temperature plasma

CsPbBr3 Perovskite Nanocrystals for a Q-Switched Pulsed Fiber Laser in the C-Band Region.

All-inorganic perovskite nanocrystals have been widely reported as promising light-harvesting and light-emitting semiconductor nanomaterials. However, their nonlinear optical properties and laser applications have rarely been explored, especially for pulse laser modulation in the telecommunication C-band window. Herein, we experimentally demonstrated a passively Q-switched erbium-doped fiber laser (EDFL) operation at the C-band region using perovskite CsPbBr3 nanocrystals as a saturable absorber (SA). The broadband linear optical absorption in the 300-2000 nm range and the nonlinear optical absorption at the C-band range of around 1560 nm were discovered and investigated in CsPbBr3 nanocrystals. The CsPbBr3-based SA exhibited good saturable absorption performance with a modulation depth and saturation intensity equivalent to 19.1% and 10.9 MW/cm2, respectively. By integrating the CsPbBr3 SA into an EDFL cavity, a passively Q-switched operation with a central wavelength of 1560 nm, a threshold pump power of 60 mW, and the shortest pulse duration of 5.96 μs was achieved. In addition, such a Q-switching operation exhibited long-term stability. Our results indicate that the CsPbBr3 perovskite nanocrystals can serve as an efficient candidate for constructing pulsed lasers in the C-band or even longer NIR wavelength region.

Wavelength modulated diode probe laser for an interferometric cavity-assisted photothermal spectroscopy gas sensor

We report on key developments made in advancing Interferometric Cavity-Assisted Photothermal Spectroscopy (ICAPS) toward a method for rugged and cost-effective gas sensing. In ICAPS, a Fabry Perot Interferometer (FPI) is employed to transduce absorption induced and analyte specific refractive index changes occurring inside the interferometer. Periodic analyte excitation is achieved by modulation of the excitation laser’s wavelength and the photothermal signal is detected by measuring the intensity of the probe laser reflected by the FPI. Maximum sensitivity is achieved when the probe’s wavelength matches the inflection point of the FPI’s transfer function. We describe the development of a locking scheme based on current induced wavelength modulation of a cost-effective diode probe laser to keep its wavelengths at the inflection point of the FPI. Because of the diode lasers characteristics, this locking procedure causes changes in the emitted laser power, which in turn influences the sensor’s sensitivity. Therefore, a normalization procedure had to be developed to correct for this inherent probe power dependency of the ICAPS sensor’s sensitivity. First, a theoretical analysis of the photothermal signal generation is given. Then a strategy is presented for stable operation of the ICAPS sensor with constant sensitivity while actively locking the probe’s wavelength. Experimental results on the example of NO detection in N2 employing a quantum cascade laser (30 mW) emitting at 1900 cm−1 (LOD 2 ppm, NNEA of 3.3⋅10−6 W cm−1Hz−1⁄2) corroborate the validity of the developed theoretical model and demonstrate its applicability to achieve constant sensor sensitivity at different sensor set-points.

Modulation Bandwidth Enhancement and Frequency Chirp Suppression in Two-Section DFB Laser

We demonstrate a two-section distributed feedback (DFB) laser for direct modulation based on the reconstruction equivalent chirp (REC) technology. The two-section DFB laser exhibits a stable single-mode characteristic. Utilizing the photon-photon resonance (PPR) effect and detuned-loading effect, the 3-dB modulation bandwidth of the two-section DFB laser is improved from 8 GHz to 23 GHz. A 25 Gb/s non-return to zero (NRZ) signal is applied to the two-section DFB laser and eye diagrams with large open extent are obtained. In addition, the relative intensity noise is reduced to below −143 dB/Hz. The frequency chirp is also suppressed. The chirp parameter is reduced from 5.67 to 1.37, which is a small value in directly modulated DFB laser. We compared the eye diagrams after transmitting different distances, the results show that the two-section structure reduces the frequency chirp significantly. The modulation of the two-section DFB laser also has good linearity, with a 1-dB compression point of more than 18 dBm.

Coded information storage pulsed laser based on vector period-doubled pulsating solitons

Pulsating soliton is a unique local structure in nonlinear dissipative system. Different from the pulse train with equal amplitude generated by conventional average soliton, the amplitude of pulsating soliton shows a remarkable periodic fluctuation behavior. With the help of the interaction between vector solitons, vector solitons with rich multi-period pulsation phenomena are successfully obtained in the experiment and numerical simulation. Then, based on the phenomenon of multi-period pulsation of vector solitons under polarization modulation, a simple and stable information storage fiber laser is designed. By changing the rotation angle of the polarization controller to adjust the polarization state in the cavity, the regulation of vector period-doubled pulsating soliton is flexibly realized. In addition, an automatic identification program is designed to process the pulse data with binary coding, so as to realize the information storage function based on vector period-doubled pulsating soliton. This result promotes the application prospect of vector solitons in optical communication, information storage and other fields.

Optimal block replacement policy for two-dimensional products considering imperfect maintenance with improved Salp swarm algorithm

Abstract Human society is entering Industry 4.0. Engineering systems are becoming more complex, which increases the difficulties in maintenance support work. Maintenance plays a very important role in the entire life cycle of a system, and in reality, maintenance is not always perfect, and its maintenance degree is between good as new and bad as old, which should be considered in the maintenance strategy. Under the framework of two-dimensional warranty, this work proposes an optimal two-dimensional block replacement strategy based on the minimum expected warranty cost. Two-dimensional block replacement maintenance is imperfect maintenance. The failure rate reduction method is used to describe the maintenance effect of two-dimensional block replacement. In case analysis, the grid search algorithm, genetic algorithm, particle swarm optimization algorithm, and improved salp swarm algorithm (SSA) are used to find the optimal warranty scheme for the laser module. The improved SSA can converge faster and find a warranty scheme that makes the warranty cost lower. Therefore, managers can use these results to reduce costs and get a win-win extended warranty cost. Rationalization suggestions are put forward for managers to make maintenance decisions through comparative analysis and sensitivity analysis.

Multiple Tb/s Coherent Optical Transceivers for Short Reach Interconnect

This paper investigates coherent optical transceivers for short-reach interconnect, where a local oscillator laser is used to boost received optical signals for high receiver sensitivity. We review the state-of-the-art technologies and propose a miniature Mach-Zehnder modulator (mMZM) array with 3D silicon photonic-electronic integration to enable high-density, low-power multiple Tb/s coherent transceivers. For design optimization at transceiver level performances, we develop methodology and models to simulate PN junction and mMZM for high-efficiency high-speed modulation, which can be linked to system performances, including high-speed performances, receiver sensitivity, optical link budget, and coherent optical transceiver power consumption. With the optimized design and state-of-the-art technologies, we achieve highly integrated multiple Tb/s coherent transceivers with high density, high speed, and low power. Our simulation results show 3 pJ/bit for integrated driver/mMZM, 5 pJ/bit for integrated PIC/IC and 6.5 pJ/bit with transceiver optics for 6.4 Tb/s with 60 Gbaud 16QAM. Compared with conventional long phase shifter (PS) MZM (4 mm), mMZM with short PS (2.4 mm) only have an extra loss of ∼2 dB under 60 Gbaud 16QAM modulation with optimized designs. We study the scalability from 6.4 Tb/s to 12.8 Tb/s using 120 Gbaud 16QAM for intra-DC interconnect. The results show that further improvement for modulation efficiency, frequency response and laser output power are needed to enable the 12.8 Tb/s.

Narrow Linewidth External Cavity Laser Capable of High Repetition Frequency Tuning for FMCW LiDAR

A light source with well-rounded performance including the narrow linewidth, wide frequency tuning range, high repetition rate and good linearity, is highly sought-after for frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR). In this work, we report a directly frequency modulated external cavity laser with the linewidth of 5.06 kHz. The frequency tuning range of 1.1 GHz, 445.5 MHz, 228.9 MHz are demonstrated at the repetition rate of 1 kHz, 10 kHz and 100 kHz, respectively. The frequency sweep linearization is achieved by iterative learning pre-distortion. The ranging performance with the repetition rate up to 100 kHz is investigated. The signal-to-noise ratio is still higher than 35 dB while the length of delay fiber is 156 m, corresponding to a target 110 m away in free space. These results indicate that the proposed swept-frequency laser has great potential for autonomous driving applications.

Pengaruh Pemberian Agen Kontras Pewarna Sintetik pada Jaringan Biologis terhadap Hasil Pencitraan Fotoakustik

An experiment to investigate the influence of synthetic dye contrast agent in photoacoustic imaging of biological tissue was conducted in this study. This study uses a simple phocoacoustic imaging system consists of three main components, i.e., a diode laser, condenser microphone, and a custom-build X-Y stage. Characterization was performed on the main components of the system to obtain the appropriate settings on imaging the biological tissue in this study. The results of the optimal frequency and duty cycle for laser modulation in this study were 19000 Hz and duty cyle of 40%, respectively. The addition of a contrast agent aims to improve the quality of the image by comparing the sample with methylene blue contrast agent, the sample with methyl red and the sample without contrast agent. The increases of acoustic intensity level is in proportion with the contrast agent concentration. The difference in the photoacoustic images reveal that the sample with methylene blue contrast agent has the highest acoustic intensity level compared to both sample with methyl red contrast agent and the sample without contrast agent. Therefore, this research proves that a photoacoustic imaging system can be developed to image biological tissue with a contrast agent and methylene blue has greater potential than methyl red to be used as a contrast agent in photoacoustic imaging.

Design of cable pipeline fault location device based on dynamic laser scanning

Aiming at the problem that some of the spare power cable pipelines without cable are damaged, and there is no effective detection equipment to detect the blocked state of the pipeline. This paper proposed a dynamic laser scanning method for obstacles in the pipeline, and designed a power pipeline fault positioning device. The infrared laser ranging technology based on time-of-flight is used to dynamically detect the distance between obstacles in the pipeline and the laser sensor, so as to detect the status and location of pipeline blockage. Taking ARM microcontroller as the core, equipped with VL53L0X laser module, the hardware design of the device was completed, and the software program was completed based on the Keil μVision5 IDE environment. The measurement and error analysis of obstacles of two different materials are carried out. The results show that the longer the measurement distance, the larger the error, and the highest measurement error is 1.47%, which fully meets the needs of engineering measurement.

Laser direct Cu patterning utilizing a commercially available low-cost 3D printer

This study evaluated an inexpensive 3D printer (below 1000 USD) as a cost effective laser direct writing machine. This printer was applied to patterning copper (Cu) electrodes along with characterizing laser modules, such as the power stability of the laser, scan speed, pattern width against laser power, and position precision of the pattern. The laser power, controlled by a pulse width modulation signal, fluctuated by approximately 7 % and decreased by 2.1 % during the measurement period. After multiple laser scanning, the positional stability according to the thickness of the patterned Cu line showed a difference of up to 3.5 μm at the center of the line pattern. Depending on the laser power, line defects appearing at the center of the Cu patterns were observed at the focal length of the laser and disappeared at longer or shorter focal lengths. As the laser power was increased from 6.3 % to 100 %, the width of the patterned Cu lines increased from 22 to 246 μm. This appears to be due to the light scattering of the Cu crystals that form early when the laser is incident. A 143 nm thick 1 cm2 Cu pattern exhibited a resistance of 2.6 × 10−5 Ω·cm. Because this method uses a 3D printer that can control the z-height during laser processing, a Cu pattern-actuated LED on a three-dimensional glass surface was demonstrated using a set of experimental conditions based on the results.

Observation of two-wave mixing in a single-frequency fiber amplifier induced by frequency modulation.

We report on the observation of unstable two-wave mixing in a Yb-doped optical fiber amplifier induced by frequency modulation of a single-frequency laser. What is believed to be a reflection of the main signal experiences a gain much higher than that provided by the optical pumping and potentially limits power scaling under frequency modulation. We propose an explanation for the effect based on the dynamic population and refractive index gratings formed by the interference between the main signal and its slightly frequency-detuned reflection.

Novel design of phase demodulation scheme for fiber optic interferometric sensors in the advanced undergraduate laboratory

Phase modulation depth (PMD) is crucial for the phase demodulation scheme of fiber optic interferometric sensors. The novel design of phase generated carrier differential-cross-multiplying (PGC-DCM) demodulation schemes allows undergraduates to understand the operation principle of the sensors and explore the connection between the PMD and the system performance. The system mainly consists of a laser, a fiber Michelson interferometer (FMI), a data acquisition card and a host computer. The simulation signal is first applied on the sensing arm of the FMI by a piezoelectric transducer and induces the phase difference shift between the two arms. Next the signal-to-noise ratios (SNRs) of the demodulated signals from the PGC-DCM algorithms under different PMD values are tested and an optimum PMD value is found. Thus, a proportion integral differential (PID) module is designed and integrated with the demodulation algorithm to calibrate the PMD to the optimum value. An ellipse fitting algorithm (EFA) is used to estimate the real-time PMD of the system that is then fed into the PID module. The amplitude of the laser modulation signal is controlled by the PID module, which is proportional to the PMD. Moreover, the response linearity, dynamic range, total harmonic distortion and phase resolution of the system are investigated.

Semiconductor laser and polarization modulator for W-band signal generation

A photonic microwave harmonic up-conversion is experimentally demonstrated using the local oscillator (LO) to directly modulate the distributed feedback laser and externally modulate the polarization modulator simultaneously. By feeding the initial radio frequency signal generated by the LO into the system, the second and fourth harmonic photonic microwaves are eventually available through the separation of the polarization beam splitter. The steady second and fourth harmonic photonic microwaves have a linewidth of about 100 Hz and a discrepancy of up to 60 dB between the central peak and the noise floor. Undesired harmonics and sidebands in the 30 GHz, 60 GHz, and 80 GHz fourth harmonic photonic microwaves can be suppressed without the use of optical amplifiers, resulting in a clear display of both tones. The single-sideband (SSB) phase noise of this proposed system adds about 6 dB of SSB phase noise in each cumulative harmonic, which is close to the ideal state.

Effect of Scattering Parameter on Small Signal analysis in Direct Modulated Dynamic Semiconductor Lasers

Effect of scattering parameter is that the effect which it is effected on the operating characteristics of direct modulated semiconductor lasers by small signal analysis for injection current density , where this parameter is effected on amount of quantum confinement carriers density where the part of this carriers density is lost in the active region. The scattering parameter leads to appear the nonlinear gain effects which they are reduced the response frequency of the direct modulation process. We use the rate equations of the single-mode semiconductor lasers and that they have characteristics are used to continuous-wave small-signal modulation. We can presented this effect and discussion it by the simple two-port device.