Laser Module Research Articles

Programmable spin and transport of a living shrimp egg through photoacoustic pressure.

In the fields of biomedicine and microfluidics, the non-contact capture, manipulation, and spin of micro-particles hold great importance. In this study, we propose a programmable non-contact manipulation technique that utilizes photoacoustic effect to spin and transport living shrimp eggs. By directing a modulated pulsed laser toward a liquid-covered stainless-steel membrane, we can excite patterned Lamb waves within the membrane. These Lamb waves occur at the interface between the membrane and the liquid, enabling the manipulation of nearby particles. Experimental results demonstrate the successful capture, spin, and transport of shrimp eggs in diameter of 220 µm over a distance of about 5 mm. Calculations indicate that the acoustic radiation force and torque generated by our photoacoustic manipulation system are more than 299.5 nN and 41.0 nN·mm, respectively. The system surpasses traditional optical tweezers in terms of force and traditional acoustic tweezers in terms of flexibility. Consequently, this non-contact manipulation system significantly expands the possibilities for applications in various fields, including embryo screening, cell manipulation, and microfluidics.

Programmable photoacoustic manipulation of microparticles in liquid

Particle manipulation through the transfer of light or sound momentum has emerged as a powerful technique with immense potential in various fields, including cell biology, microparticle assembly, and lab-on-chip technology. Here, we present a novel method called Programmable Photoacoustic Manipulation (PPAM) of microparticles in liquid, which enables rapid and precise arrangement and controllable transport of numerous silica particles in water. Our approach leverages the modulation of pulsed laser using digital micromirror devices (DMD) to generate localized Lamb waves in a stainless steel membrane and acoustic waves in water. The particles undergo a mechanical force of about several µN due to membrane vibrations and an acoustic radiation force of about tens of nN from the surrounding water. Consequently, this approach surpasses the efficiency of optical tweezers by effectively countering the viscous drag imposed by water and can be used to move thousands of particles on the membrane. The high power of the pulsed laser and the programmability of the DMD enhance the flexibility in particle manipulation. By integrating the benefits of optical and acoustic manipulation, this technique holds great promise for advancing large-scale manipulation, cell assembly, and drug delivery.

Improving ranging performance of SiPM LiDAR in low SNR conditions through an echo processing method and laser pulse modulation

Due to its numerous advantages such as high gain and low operating bias, the silicon photomultiplier (SiPM) holds great potential in LiDAR applications. However, it is more jittery at weak echoes and more sensitive to ambient light, making its ranging performance at low signal-to-noise ratios (SNRs) severely deteriorated. To enhance the ranging performance of SiPM LiDAR under low SNR, a novel echo processing method, to the best of our knowledge, was proposed based on the statistical property of SiPM responses and validated under relatively intensive sunlight (>50klx) using a self-developed LiDAR system. At the same time, laser pulse width modulation and multi-pulse laser emission are used in ranging experiments to maximize the advantages of this method. It has shown that increasing the laser pulse width within a certain range can improve ranging performance, and that emitting multiple laser pulses improves ranging performance more significantly. Utilizing a three-pulse laser with a peak power of only 3.2 W, a target 122 m away was ranged with a precision of 6.53 cm with only five accumulations.

Ultrafast nonlinear optical response of layered violet phosphorus for femtosecond noise-like pulse generation

As a new member of two-dimensional (2D) phosphorene, 2D layered violet phosphorus (VP) has unique optoelectronic properties and good environmental stability, showing its huge advantages in optoelectronic applications. In this paper, the ultrafast nonlinear optical (NLO) properties of layered VP nanosheets at 1 µm band were explored, which exhibit an obvious saturable absorption response with a modulation depth of ∼1.97%. Meanwhile, the fast and slow carrier lifetimes of VP nanosheets at 1µm band were also determined as 295.9 fs and 2.36 ps, respectively, which are much shorter than that of most reported 2D materials. The excellent saturable absorption response combined with ultrashort carrier lifetimes indicate the prospect of layered VP nanosheets as a fast saturable absorber (SA) for ultrafast laser modulation. Then we demonstrated a Yb-doped fiber laser based on the VP-deposited taper-shaped fiber (TSF) SA, which delivers stable Q-switched mode-locked (QSML) pulses, dual-wavelength mode-locked pulses and 404-fs noise-like pulses. This work fully demonstrates the great potential of 2D VP materials for 1 µm ultrashort laser pulse generation.

High-speed and high-precision measurement of biaxial in-plane displacements: tens of nanometers principle error suppression in microprobe sensors

When the microprobe sensor is faced with the demand of high-speed biaxial displacement measurement, due to the characteristics of phase generated carrier (PGC) technology, accompanying optical intensity modulation (AOIM) and unfavorable phase modulation depth (PMD) will bring about the tens of nanometer cyclic nonlinear errors, further hindering high-speed and high-precision measurement. Herein, a light source intensity stabilization system based on semiconductor optical amplifier (SOA) feedback control is achieved to eliminate the error caused by AOIM in the presence of high-frequency and large-amplitude laser modulation. Based on this, the reasons for large nonlinear errors in biaxial measurements and the inability to ensure the stability of the accuracy of multiple measurement axes are methodically examined, and an effective nonlinear error elimination methodology based on the normalized amplitude correction of active temperature scanning is proposed. The continuity and linearity of the temperature scanning are also discussed. The performed experiments show that the above approach is capable of reducing the displacement demodulation error from the nanometer scale to the sub-nanometer scale. Further, the nonlinear error is reduced to within 0.1 nm for both measurement axes and the performance becomes consistent. The dual-axis measurement resolution of the microprobe sensor reaches 0.4 nm and the measurement speed is better than 1.2 m/s with the standard deviation of lower than 0.5 nm.

Efficient single-pixel imaging based on a compact fiber laser array and untrained neural network

This paper presents an efficient scheme for single-pixel imaging (SPI) utilizing a phase-controlled fiber laser array and an untrained deep neural network. The fiber lasers are arranged in a compact hexagonal structure and coherently combined to generate illuminating light fields. Through the utilization of high-speed electro-optic modulators in each individual fiber laser module, the randomly modulated fiber laser array enables rapid speckle projection onto the object of interest. Furthermore, the untrained deep neural network is incorporated into the image reconstructing process to enhance the quality of the reconstructed images. Through simulations and experiments, we validate the feasibility of the proposed method and successfully achieve high-quality SPI utilizing the coherent fiber laser array at a sampling ratio of 1.6%. Given its potential for high emitting power and rapid modulation, the SPI scheme based on the fiber laser array holds promise for broad applications in remote sensing and other applicable fields.Graphical

Low-power-consumption modulation of short-cavity DBR laser on SiO2/Si substrate

We developed short-active-length distributed Bragg reflector (DBR) lasers to reduce the power consumption of chip-to-chip optical interconnects. These lasers have buried bulk InGaAsP waveguides to increase the coupling efficiency between the active region and DBR to 99.79% from the 98.14% of our previous DBR lasers that had InP channel waveguides. We achieved continuous wave operation of 5- to 80-µm active-length DBR lasers and the 5-µm-long laser consumed 24 fJ/bit with a 10-Gbps NRZ signal. The threshold current of the 5-µm laser was 51 µA, which compares favorably to our previous 10-µm DBR lasers with a threshold current of 170 µA.

Control of quality factor of atomic force microscopy cantilever by cavity optomechanical effect

The effective quality factor of the cantilever plays a fundamental role in dynamic mode atomic force microscopy. Here we present a technique to modify the quality factor of an atomic force microscopy cantilever within a Fabry–Perot optical interferometer. The experimental setup uses two separate laser sources to detect and excite the oscillation of the cantilever. While the intensity modulation of the excitation laser drives the oscillation of the cantilever, the average intensity can be used to modify the quality factor via optomechanical force without changing the fiber-cantilever cavity length. The technique enables users to optimize the quality factor for different types of measurements without influencing the deflection measurement sensitivity. An unexpected frequency shift was observed and modelled as temperature dependence of the cantilever’s Young’s modulus, which was validated using finite element simulation. The model was used to compensate for the thermal frequency shift. The simulation provided relations between optical power, temperature, and frequency shift.

Broadband High-Precision Faraday Rotation Spectroscopy with Uniaxial Single Crystal CeF3 Modulator

We present a low-noise (<10 µrad/Hz) broadband Faraday Rotation Spectroscopy method which is feasible for near-ultraviolet through near-infrared wavelengths. We demonstrate this in the context of a high-precision spectroscopy experiment using a heated Pb vapor cell and two different lasers, one in the UV (368 nm) and a second in the IR (1279 nm). A key element of the experimental technique is the use of a uniaxial single crystal CeF3 Faraday modulator with excellent transmission and optical rotation properties across the aforementioned wavelength range. Polarimeter performance is assessed as a function of crystal orientation and alignment, AC modulation amplitude, laser power, and laser wavelength. Crystal-induced distortion of the (6p2)3P0→(6p2)3P1 (1279 nm) and (6p2)3P1→(6p7s)3P0 (368 nm) spectral lines due to misalignment-induced birefringence is discussed and modeled using the Jones calculus.

Simple modulation of Lissajous MEMS laser beam scanning with reconfigurable structured light patterns for 3D imaging

Structured light 3D imaging systems commonly employ panel-based projectors or 1-axis MEMS mirrors with beam expander lens to project multi-frame barcodes or dot clouds, addressing challenges posed by objects with multi-scale feature sizes. However, these methods often result in large system volumes due to the required projection multi-lens modules, high hardware costs, or limited light pattern generation capabilities that hindering measurement precision enhancement. This paper introduces an innovative approach to reconfigurable spatial light pattern projection using a single bi-axial MEMS mirror with Lissajous scanning. In contrast to the pixel-by-pixel pre-defined image patterns encoding of conventional 2D laser beam scanning, the proposed method simply aligns the MEMS bi-axial resonance frequencies with laser pulse modulation, enabling the projection of diverse structured light patterns such as stripes, lines, dot matrices, and random dot clouds, which can adapt to different 3D imaging algorithms demands. It eliminates the need for multi-frame encoding and streamlines data caching, simplifies digital logic hardware. A prototype 3D imaging system was developed to demonstrate the mathematical model for laser modulation and the technical feasibility based on the proposed principle. Beyond its lens-free essence, the system supports focal-free optics and a compact projection form factor, which accommodates to a broad range of projection distances and field-of-views based on object’s location. 3D depth map of polynomial surface and blocks objects are extracted through single-frame pattern projection with a relative high accuracy. The presented modulation theory for diverse structured light pattern generation opens avenues for versatile and compact 3D imaging applications of LiDAR and robotic 3D vision.

Fluorescence modulation of quantum dots in subsurface defects of optical elements by a linearly polarized light.

The limited excitation efficiency of quantum dots in the detection of subsurface defects in optical elements by quantum dot fluorescence gives rise to insufficient accuracy. To enhance the excitation efficiency of quantum dots, we studied the modulation of the polarization direction of linearly polarized incident light on quantum dot fluorescence. We first apply density matrix evolution theory to study the quantum dots interacting with linearly polarized incident light and emitting fluorescence. The fluorescence intensity exhibits cosine oscillations versus modulated laser polarization. It reaches a maximum value at the polarization angle zero, and then decreases as the angle becomes larger until π/2. The experimental results for the quantum dot in both solutions and subsurface defect of optical elements confirmed these results. For optical elements tagged with CdSe/ZnS quantum dots, the fluorescence intensity increases by 61.7%, and the area for the detected subsurface defects increases by 142.9%. Similarly, for C and InP/ZnS quantum dots, there are also increases in both the fluorescence intensity and the area of subsurface defects. Our study suggests that the subsurface defect detection in optical elements by the linearly polarized incident light could enhance the detection accuracy of subsurface defects in optical elements, and potentially achieve super-resolution imaging of subsurface defects.

Line-Spacing-Multiplied Optical Frequency Comb Generation Using an Electro-Optic Talbot Laser and Cross-Phase Modulation in a Fiber

An optical frequency comb (OFC) generator based on an electro-optic Talbot laser and cross-phase modulation (XPM) in a high nonlinear fiber (HNLF) is designed and demonstrated. The Talbot laser is an electro-optic frequency shifting loop that is used to produce repetition rate-multiplied pulses, and these pulses work as a pump signal that induces the XPM process in the HNLF to modulate the phase of a probe signal. At the output of the HNLF, OFCs with a multiplied line spacing can be generated. The effects of the pump power and the HNLF length on the performance of the generated OFCs are theoretically analyzed. In the experiments, the line spacing of the generated OFCs is multiplied to be 10 GHz, 15 GHz, and 20 GHz with a factor of 2, 3, and 4, respectively. The center of the OFCs is tuned in a 4 nm range by adjusting the wavelength of the probe signal.

Continuous wave and active Q-switched operation of Watt-level LED-pumped two-rod Nd,Ce:YAG laser

Abstract In this paper, we demonstrated a high-performance LED-side-pumped two-rod Nd,Ce:YAG laser with continuous-wave (CW) and acousto-optical (A-O) Q-switched operation. A symmetrical shaped flat-flat cavity with two identical LED-side-pumped laser modules was employed for power scalability. In the CW regime, the maximum output average power of laser at 1064 nm was 4.41 W, corresponding to the highest optical conversion efficiency of 5.3% and a slope efficiency of 12.4%. In the active Q-switched regime, the pulse energy of laser was as high as 0.89 mJ at a repetition rate of 800 Hz with a pulse width of 457.2 ns, corresponding to the highest peak output power was 1.94 kW and the M2 factor was measured to be about 8.8. To the best of our knowledge, this is the first demonstration and the highest performance of an CW LED-side-pumped two-rod laser Nd,Ce:YAG with watt-level output reported so far.

Highly sensitive mid-infrared methane remote sensor using a deep neural network filter.

A novel mid-infrared methane remote sensor integrated on a movable platform based on a 3.291-µm interband cascade laser (ICL) and wavelength modulation spectroscopy (WMS) is proposed. A transmitting-receiving coaxial, visualized optical layout is employed to minimize laser energy loss. Using a hollow retro-reflector remotely deployed as a cooperative target, the atmospheric average methane concentration over a 100-meter optical range is measured with high sensitivity. A deep neural network (DNN) filter is used for second harmonic (2f) signal denoising to compensate for the performance shortcomings of conventional filtering. Allan deviation analysis indicated that after applying the DNN filter, the limit of detection (LOD) of methane was 86.62 ppb with an average time of 1 s, decreasing to 12.03 ppb with an average time of 229 s, which is a significant promotion compared to similar work reported. The high sensitivity and stability of the proposed sensor are shown through a 24-hour continuous monitoring experiment of atmospheric methane conducted outdoors, providing a new solution for high-sensitivity remote sensing of atmospheric methane.

Ultra-compact exciton polariton modulator based on van der Waals semiconductors

With the rapid emergence of artificial intelligence (AI) technology and the exponential growth in data generation, there is an increasing demand for high-performance and highly integratable optical modulators. In this work, we present an ultra-compact exciton-polariton Mach–Zehnder (MZ) modulator based on WS2 multilayers. The guided exciton-polariton modes arise in an ultrathin WS2 waveguide due to the strong excitonic resonance. By locally exciting excitons using a modulation laser in one arm of the MZ modulator, we induce changes in the effective refractive index of the polariton mode, resulting in modulation of transmitted intensity. Remarkably, we achieve a maximum modulation of −6.20 dB with an ultra-short modulation length of 2 μm. Our MZ modulator boasts an ultra-compact footprint area of ~30 μm² and a thin thickness of 18 nm. Our findings present new opportunities for the advancement of highly integrated and efficient photonic devices utilizing van der Waals materials.

Miniaturizing a coherent beam combining system into a compact laser diode module.

We present a laser module with dimensions of 76×43×15m m 3 that for the first time to our knowledge realizes a coherent beam combination in such a compact device, using two tapered amplifiers seeded by a distributed Bragg reflector ridge waveguide laser diode operating at 761nm in a single longitudinal mode. The generated combined optical power is up to 5W continuous wave with a combing efficiency of 85%. The phase of the system is controlled by the current in the ridge waveguide section of one of the tapered amplifiers. The phase-stabilization process is automated using a reverse hill-climbing algorithm and an ATmega328P microcontroller.

High-reliability infrared broadband thin-film polarizing beam splitter with ZnSe compensation layers.

Thin-film polarizing beam splitters (PBSs) fulfill a pivotal role in laser beam splitting, modulation, shaping and isolation. In this study, a high-reliability infrared broadband thin-film PBS was developed. To correct for tensile stress in Ge/YbF3 multilayer coatings, ZnSe compensation layers were incorporated in the multilayer design. The effects of different symmetrical periods on the spectral properties of the infrared PBS were systematically discussed. The infrared PBS operated at 45° and in the long-wave infrared (LWIR) band. Using the percent of optical extrema monitoring (POEM) strategy combined with the high-temperature optical constants (HTOC) of Ge film, the infrared PBS was precisely fabricated on ZnSe substrates. Subsequently, the spectral performance and film reliability of the infrared PBS were carefully characterized. Specifically, the transmittance of p-polarization surpassed 96%, while the extinction ratio exceeded 100:1 within the 10.6 ± 0.15 µm band. The infrared PBS demonstrated commendable environmental reliability, in addition to exhibiting excellent spectral characteristics.

A COMSOL novel micromirror matrix model for digital image display

Digital micromirror devices (DMD) have gained significant attention in various scientific and industrial domains due to their potential for spatial light and laser modulation. However existing micromirrors designs often face limitations in terms of rotation angles, voltage consumption, and stability time for some type of applications. In this paper, we address these issues by exploring micromirror structure materials, more precisely, the materials for the torsion bar. To achieve this, we have used COMSOL Multiphysics knowing to provide accurate predictive simulation results, to design a micromirror model incorporating three inclination modes: unidirectional, bidirectional, and a user-defined free mode. Through extensive simulations, we have compared different materials for the torsion bar of the micromirror and have evaluated their performance in terms of voltage consumption, stability time, rotation angles and electric energy consumption. Aluminum 3008-H18 emerged as the optimal choice, exhibiting a stability time of 40 μs and achieving a maximum tilt of 12.75 degrees. The micromirror system has demonstrated stable position within the voltage range (from 0 volts to 27 volts) and maximum electric energy consumption of 7.72 × 10−8 μJ. Our micromirror design features a 10 × 10 μm reflective element capable of achieving a maximum inclination of ±12.75 degrees. To enhance the capabilities of the micromirror, an 8 × 8 micromirror matrix has been developed, enabling collective and coordinated movements of individual micromirrors. Also, a process for translating digital images into micromirror states has been devised, enabling accurate image display on the matrix. Simulation results demonstrate the effectiveness of the micromirror matrix design and the image processing script, images displayed on the micromirror matrix exhibit high accuracy, faithfully reproducing desired patterns in the primary images. Overall, our proposed micromirror model and micromirror matrix model offer enhanced performance, versatility, and accuracy, enabling a diverse array of simulations across scientific research and industrial domains.

Pilot Study to Demonstrate Improvement in Skin Tone and Texture by Treatment with a 1064 nm Q-Switched Neodymium-Doped Yttrium Aluminum Garnet Laser.

The 1064 nm Q-switched neodymium-doped yttrium aluminum garnet (QS Nd:YAG) laser was developed to treat unwanted pigmentation in the skin such as lentigines caused by photoaging, and tattoos from dye/ink insertion. This laser has also been used for non-ablative epidermal rejuvenation (skin toning). To evaluate changes in skin tone, skin texture and overall improvement after a series of treatments with the QS Nd:YAG laser. Participants received seven full-face treatments with M22 or Stellar M22, a 1064 nm QS Nd:YAG laser, at 2-week intervals. The investigators and participants evaluated the improvement in skin tone and texture at 1, 3 and 6 months after the last treatment. Patient satisfaction, patient discomfort, downtime and adverse events were recorded. Histological changes in the treated area were also evaluated. Thirteen women with a median age of 45 years (range, 34-61 years) were included in the study. The majority of the participants (53.9%) had skin type VI. One month after the last treatment session, 38% of participants reported good to very good improvement. This value increased to 100% participant improvement at both the 3-month and 6-month follow-up visits. The reduction in melanin index and the histological analysis demonstrated that the laser procedure contributed to a reduction in epidermal melanin content. Treatments were not associated with high levels of pain or discomfort. The most common immediate post-treatment response was erythema and edema. Most participants were satisfied with the resulting treatment outcome. Skin treatment with the 1064 nm QS Nd:YAG laser module on the M22 and Stellar M22 devices, using a large spot size, low fluence, moderately high repetition rate, improves skin tone and texture in patients with skin types II-VI.

Free space optical communication system: a review of practical constraints, applications, and challenges

Abstract FSO (free space optical) communication holds emanated position in the role of propitious innovation with exorbitant-speed using the data transmission mechanism without the wire, propounding an accomplishable explication to the surging need for bandwidth in communication networks. This research paper probes into the improvements and obstacles in FSO communication systems, pursuing to anticipate a compendious encapsulation of the state-of-the-art establishment in this discipline. The evaluation incorporates a meticulous inspection of vital constituents such as laser sources, modulators, and receivers, elucidating their contribution to accomplishing coherent data transfer. The scrutinizing also investigates innumerable atmospheric circumstances affecting FSO links, including weather conditions and turbulence, and puts forward ingenious approaches to alleviate their repercussion on communication performance. Furthermore, the paper explores the homogenization of ultra-modern signal processing techniques to amplify the credibility and robustness of FSO systems, corroborating seamless communication even in challenging environments. Moreover, the research inquiries into the neoteric experimental framework and real-world execution of FSO communication, shedding light on heuristic contemplation, and substantiating theoretical unearthing. The conclusion of this research shells out treasures perception of the ongoing attempt to optimize FSO communication for variegated applications, including, inter-satellite communication, high-speed internet access, and last-mile connectivity. As FSO perpetuates progress, this paper suffices as a recent and inclusive resource for researchers, engineers, and policymakers maneuvering the edges of optical communication technologies.