Large Divergence Angle Research Articles

Comparison of spectral beam combining based on reflecting volume Bragg grating, with and without collimating lenses

AbstractOn the basis of the principle of spectral beam combining (SBC), a simple combining system using a reflecting volume Bragg grating as a combiner was designed in which two focusing lenses were used to control the incident angles of input beams, and two concave lenses were used to solve the problem of beam divergence caused by focusing lenses. The effects of the beam divergence angle (DA) on diffraction efficiency and beam quality were analyzed theoretically. The simulation results showed that a larger DA will reduce diffraction efficiency and lead to deterioration of beam quality. In the SBC experiment, the performances of the output beam with and without concave lenses were compared. The experimental results showed that, when the concave lenses were not inserted, the measured output power was 503 mW with a combining efficiency of 85.3% and the beam quality factor of 1.68. The experiment further showed that the combined power was 566 mW with a combining efficiency of 96% and a beam quality factor of 1.31 when concave lenses were used.

Transmission and homogenization of laser-driven proton beams with broadband spectra

<p indent="0mm">Over the past few decades, laser accelerators made continuous progress. Thanks to the ultra-high electric field gradient (100 GV/m) generated by the interaction of laser and plasma, protons can be accelerated to MeV energy at a micron scale, being expected to be a new generation of widely used compact accelerators. The laser-driven proton beam has the characteristics of μm-level size (point source), ampere-level peak current, broadband energy spectrum, and large divergence angle. Irradiation applications need a uniform dose distribution, requiring the transformation from a point source to a large area of uniformly distributed particles. Increase of utilization efficiency requires that beams with energy spread as large as possible can be transmitted, while the chromatic aberrations pose a challenge to the homogenization of the beams, including the homogenization of the beams with the same energy and different initial divergence angles, and the homogenization of the beams with different energies. The weak focusing of the constant gradient magnetic field can focus in the horizontal and vertical directions at the same time, and analyze the energy in the horizontal direction. The integration of focusing and energy analysis can achieve achromatic transmission, or significantly reduce the influence of chromatic aberrations. This paper studies the transmission characteristics of proton beams in weak-focusing magnetic fields. The homogenized transformation for protons with the same energy in the horizontal direction from a point to a large area by point-to-parallel imaging is demonstrated. Point-to-parallel imaging is not a necessary condition for homogenization; transformation without point-to-parallel imaging in the vertical direction also obtains good homogeneity. The conditions for positional achromaticity in the horizontal direction are explored, and the transmission and homogenization of proton beams with 20% energy spread can be achieved with appropriate design. In positional achromatic transmission, the chromatic aberrations still have influence, causing the proton beam with large energy spread to deviate from the center of the beamline in the horizontal direction. In order to reduce the influence of chromatic aberrations, a special steering magnet is designed after the weak-focusing magnet to correct the divergence angle in the horizontal direction. The relationship between the correction amount of divergence angle and the position in the horizontal direction is obtained through parameter scanning, which can be well fitted by a 4 order polynomial. After correcting the divergence angle, the proton beam with large energy spread returns to the center of the beamline at the beamline exit. With a slit and energy spectrum shaping, proton beams with 80% energy spread can be obtained for irradiation with better uniformity. When the deflection radius is designed to be <sc>0.65 m,</sc> the weak-focusing beamline can transmit proton beams with <sc>1–20 MeV</sc> energy, 80% energy spread, and an initial divergence angle of ±50 mrad. After changing the magnetic field direction, electron beams with <sc>1–200 MeV</sc> energy, 40% energy spread can be transmitted. The transmission and homogenization of the proton beam with 80% energy spread greatly improves the utilization efficiency. Higher energy particle beams can be delivered using superconducting or pulsed magnet technology. The study found that the influence of chromatic aberrations is much larger in the beam transmission with a quadrupole triplet lens (strong focusing), and as energy cannot be accurately analyzed, it is difficult to improve. In comparison, the weak-focusing magnetic fields have significant advantages for beam homogenization.

Experimental demonstration of blue light transmitter with 30 Mbps modulated rate and 1.69 W optical power for underwater wireless optical communication based on chip-on-board light-emitting diode array

Recently, a light-emitting diode (LED) was used as an optical source in the transmitter for underwater wireless optical communication (UWOC) because it has a large divergence angle that makes establishing the communication link easier. In practice, there are several discrete LEDs in the transmitter to enlarge its output power. However, with the increase in the number of LEDs, the parasitic resistance and inductance in the light source is larger too, which affects the quality of the modulated signal. Also, using more discrete LEDs enlarges the luminous surface, which is disadvantageous to improving the tolerance to water pressure for UWOC equipment. To reduce such influences, a transmitter is proposed with a chip-on-board LED array because it has a smaller luminous surface, parasitic resistance, and inductance. Using such a transmitter, a UWOC system is established and tested in a large experimental tank. The results show that it could realize a 19 m communication distance with a 30 Mbps rate in water with an attenuation coefficient that is about 0.26 m − 1. The output power is 1.69 W, and the radiation intensity is approximately a Lambert distribution with a 120 deg divergence angle. Further analysis shows that the communication distance could increase to 90.5 m in clear water with a 0.02 m − 1 attenuation coefficient, and the emission light could cover 86.5% of the solid angle of the hemisphere space. The speed is higher than the same class light source in the previous sea trails, and the combination performance of angle coverage area, distance, and speed is suitable for ocean engineering. The proposed method is useful, simple, low-cost, and pragmatic, which makes it easy to popularize and apply.

On Optimizing the Divergence Angle of an FSO-Based Fronthaul Link in Drone-Assisted Mobile Networks

In a free space optics (FSO)-based drone-assisted mobile network, a drone-mounted base station (DBS) can be rapidly deployed over a place of interest to relay traffic between Internet of Things (IoT) devices and a macro base station (MBS), and FSO is applied as the fronthaul solution between the DBS and the MBS to provide a high link capacity at a long distance. However, due to inevitable optical beam misalignment, having a smaller divergence angle of the optical beam may increase the outage probability of the FSO-based fronthaul link. On the other hand, having a larger divergence angle may reduce the capacity of the FSO-based fronthaul link. So, it is critical but challenging to determine the divergence angle in order to optimize the tradeoff between minimizing the outage probability and maximizing the capacity for the FSO-based fronthaul link in the context of the FSO-based drone-assisted mobile network. In this article, we formulate an optimization problem to determine the optimal divergence angle that can minimize the link outage probability, while guaranteeing the capacity of the FSO-based fronthaul link no less than the threshold. The link outage and capacity aware divergence angle (LEARN) algorithm is designed to efficiently solve the problem. The performance of LEARN is demonstrated via extensive simulations.

Efficient Emission Outcoupling from Perovskite Lasers into Highly Directional and Long‐Propagation‐Length Bloch Surface Waves

AbstractHalide perovskite micro‐ and nanolasers have become a novel platform for efficient generation of coherent emission in the whole visible range. However, the laser emission outcoupling from the perovskite microcrystals faces a number of problems related to large divergence angle, light‐soaking by a substrate, and high losses in the case of coupling with nanowaveguides. Here the perovskite nano‐ and microlasers are proposed to be integrated with a photonic crystal supporting Bloch surface waves (BSWs), which are coupled directly from the perovskite lasers with the efficiency of over 16%. The BSWs exciting at 535‐nm wavelength show high in‐plane directivity, down to 9, and long‐propagation length, up to 50 m. Moreover, a pronounced beam steering effect for the generated laser emission is demonstrated by varying the pumping laser beam position, which provides an additional degree of freedom for in‐plane control of the lasing mode outcoupling.

Beamline design with weak-focusing magnetic field for applications of laser-driven proton beams

&lt;sec&gt;With the development of high-power laser technology, laser plasma acceleration has developed rapidly due to its excellent acceleration structure. Nearly one-hundred-MeV proton beams and several GeV electron outputs are obtained. The laser-driven proton beams have excellent quality of μm-scale sizes and ps-scale pulse lengths. Owing to the existence of the accelerating laser field, direct application is difficult, so the proton beams need to be transmitted to the application terminal through the beamline. However, the wide energy spectrum and large divergence angle bring difficulties in transmitting the beam. The weak focusing in the constant gradient magnetic field is neglected in the transmission of laser-driven particle beams because of the relatively weak focusing force. But weak focusing has special advantages: simultaneous focusing in the horizontal direction and the vertical direction, energy analysis in the horizontal direction, focusing force in the horizontal and vertical direction distributed by the field index &lt;i&gt;n&lt;/i&gt;, and smaller influence of chromatic aberration effect.&lt;/sec&gt;&lt;sec&gt;In this paper, we propose the beam transmission with weak-focusing magnet. The requirements for the focusing of proton beams with the same energy and different divergence angles in the &lt;i&gt;X&lt;/i&gt; direction and &lt;i&gt;Y&lt;/i&gt; direction in the weak-focusing magnetic field are explored by studying the linear beam dynamics of the beams. Then the conditions of precise energy analysis for particle beams with large divergence angle can be determined. For beams with 2% energy spread, the lengths of the drift space before and after the weak-focusing magnet and deflection radius are scanned to find out the minimum beam size and the shortest pulse length after transmission. It is found that a certain combination of drift space and deflection radius can minimize the beam size or the pulse length. Focusing and energy selection can be achieved while compressing the pulse length and effectively reducing the size of the beamline, which has significant advantages. When the deflection radius is 0.65 m, the proton beam with 20 MeV energy, 2% energy spread, and an initial divergence angle of ±50 mrad has the root-mean-square size of 108 μm in both the &lt;i&gt;X&lt;/i&gt; direction and the &lt;i&gt;Y&lt;/i&gt; direction, and a pulse length of 154 ps at the application terminal.&lt;/sec&gt;&lt;sec&gt;Comparing with common beam transmission elements such as quadrupole lenses and deflection magnets, the laser-accelerated ion beam benefits from the integration of focusing and energy analysis of weak-focusing magnetic fields (focusing and energy analysis exist at the same time and continuously change with deflection angle), as well as the horizontal and vertical focusing forces can be distributed by the magnetic field index &lt;i&gt;n&lt;/i&gt; (the larger the &lt;i&gt;n&lt;/i&gt;, the stronger the focusing force in the vertical direction is and the weaker the focusing force in the horizontal direction). When the proton beam is transmitted in a weak-focusing magnetic field, the advantages of the focusing element and the energy selection element are combined, so the influence of the chromatic aberration effect can be reduced, the pulse length can be compressed, and the beamline size can be effectively reduced.&lt;/sec&gt;

Manipulating the Laser-Driven Proton Bunch with Plasma Wakefield

With the advantages of short duration and extreme brightness, laser proton accelerators (LPAs) show great potential in many fields for industrial, medical, and research applications. However, the quality of current laser-driven proton beams, such as the broad energy spread and large divergence angle, is still a challenge. We use numerical simulations to study the propagation of such proton bunches in the plasma. Results show the bunch will excite the wakefield and modulate itself. Although a small number of particles at the head of the bunch cannot be manipulated by the wakefield, the total energy spread is reduced. Moreover, while reducing the longitudinal energy spread, the wakefield will also pinch the beam in the transverse direction. The space charge effect of the bunch is completely offset by the wakefield, and the transverse momentum of the bunch decreases as the bunch transports in the plasma. For laser-driven ion beams, our study provides a novel idea about the optimization of these beams.

Demonstration of a 2 × 2 MIMO-UWOC system with large spot against air bubbles

In order to reduce turbulence-induced scintillation and deal with alignment problems, a 2×2 multiple-input multiple-output (MIMO) underwater wireless optical communication (UWOC) system is proposed and experimentally demonstrated. With help of the large divergence angle of light beams and large field of view (FOV) of the detectors, the effect of high-density air bubbles is greatly eliminated. Simulation and experimental results confirm that, in most intensity-modulation/direct-detection (IM/DD) MIMO-UWOC systems, the repetition coding (RC) scheme performs better than the space-time block coding (STBC) scheme. In a 50 m swimming pool, the maximum horizontal offset can reach 97.9 cm, which is 421% and 192% higher than that of STBC multiple-input single-output (MISO) and RC-MISO/STBC-MIMO schemes, respectively. With a data rate of 233 Mbps and a transmission distance of 50 m, the large detection range can meet a variety of underwater wireless communication requirements. The experiment indicates that, when the difference in the transmission distance between the two optical signals is higher than 1 m, the bit error rate (BER) of the RC scheme increases sharply, while the BER of the STBC scheme is stable. The MIMO coding scheme needs to be selected according to the actual application environment.

Ceramic Inlay Bonded Interfaces in Minimally Invasive Preparations: Damage and Contributing Mechanisms in Sliding Contact.

In the preparation of inlay cavities, a choice must be made between conventional standard and minimally invasive preparation designs; in the long run, this choice can affect the integrity of the bonded interface. To evaluate the effect of minimally invasive cavity preparation designs on the extent and contributing mechanisms of damage to ceramic inlay bonded interfaces. Tooth blocks with 90°, 120° and 75° marginal angles were prepared, representing tooth cavities with conventional standard and minimally invasive preparations with large divergence and convergence angles and bonded to monolithic ceramic (IPS e.max CAD). Vickers indentations were placed at various distances from the bonded interface. The indentation morphology and crack length were observed. Reciprocating wear tests were performed on the bonded interface with a 20-newton (N) vertical load. The wear depth and wear-scar morphology were characterized after increments of cyclic sliding contact. The 120° group exhibited longer indentation cracks in the ceramic, whereas the 75° group showed larger indentations in the enamel when compared to the 90° group (p<0.001). Consistent with the weaker edge crack resistance, the 120° group experienced the greatest wear (p=0.008), and the wear depth in the enamel of the 75° group exceeded that of the 90° group (p<0.001) in the early stage (5×102 cycles). However, no significant difference in the wear depth (p>0.147) and morphology were found at the later wear stage among the three groups. Within the limitations of this study, minimally invasive preparations with 120° and 75° marginal angles can result in early sever damage at the ceramic inlay bonded interface but show comparable wear behaviors to the conventional 90° group at the later stage.

Proton Beam Generated in PW Laser Interaction With Nano-Structure Array for Proton Therapy

In comparison with large and expensive conventional linear and circular accelerator, miniaturized laser-driven proton accelerator provides the potential to reduce the overall costs. This could allow a widespread use of the superior properties of protons and ions in radiation therapy. However, the key to success is to improve the particle energy which is not high enough to meet the requirement for the treatment. With the development of high-repetition-rate petawatt class laser technology matures gradually, different acceleration mechanisms have been able to raise the energy of protons to close to 100MeV.To confirm the feasibility of proton beam generated in petawatt-laser irradiating nano-array target, three-dimensional particle-in-cell (3D-PIC) simulations were performed with the QED-PIC code EPOCH. The simulation box has a size of 30 μm(x) × 20 μm (y) × 20 μm (z), which is sampled by cells of 1500 × 400 × 400 with 125 pseudo-electrons, eight pseudo-carbons, and four protons in each cell. The Gaussian laser pulse propagates along the x-direction with y-direction polarization, a wavelength λ0 of 1μm, a peak power of 50 PW, and a duration of 30 fs in full width at half maximum (FWHM). With an initial focal spot radius σ = 3μm. In order to reduce the computational requirements. The array wires have an initial density of ne = 300nc (where nc = 1.1 × 1021 cm-3 is the critical plasma density) and are attached to a 4-μm-thick CH foil. In these simulations, periodic boundary conditions were employed for the laser field in the transverse directions and absorbing boundary conditions for the particles.Three-dimensional particle-in-cell simulation show that the laser-driven proton beam keep quite different characteristics compared with other accelerators proton beam, such as ultra-short beam duration (ns), high strength (107 / cm2 / pulse), large divergence angle (2°) and poly real-energetic spectrum. Meanwhile, we show that under optimal interaction conditions protons can be accelerated up to relativistic energies of 300 MeV by a petawatt laser field. The proton acceleration is due to the dragging Coulomb force arising from charge separation induced by the ponderomotive pressure ∼light pressure! of high-intensity laser.We investigate the impact of nano-structure array on the proton spectrum for different laser-plasma conditions. Our simulated data show that the nanostructures lead to a significant enhancement of absorption over the entire range of laser plasma conditions investigated. At conditions that do not allow for efficient laser absorption by plane targets, nano-structure array is found to significantly enhance the proton cut-off energy and conversion efficiency.S. Wu: None. Z. Wang: None. X. Sun: None. W. Wang: None. F. Xiao: None. L. Zhao: None.

Compact integrator design for short-distance sharp and unconventional geometric irradiance tailoring.

A compact microlens array (MLA) integral homogenizer composed of a projection MLA, a condenser MLA, and a subimage array mask based on Kohler illumination is presented herein. By adopting the optimal design of an aspheric projection sublens, a short-distance integrator for unconventional geometric irradiance tailoring can be acquired. Compared with the traditional integrator, the integral lens is removed in the proposed integrator. An incident beam with a larger divergence angle is permitted while a sharp illumination performance is maintained. In addition, the illumination distribution with a predefined geometrical profile can be obtained by introducing a subimage array mask without replacing the MLA elements. Through the introduced mask, the illumination attenuation area is cut, the distortion is caused by the large NA, and the peak effect caused by the integral lens of the traditional integrator can be eliminated. The subimage array mask is generated by combining ray tracing and the radial basis function image warping method. By introducing the array mask into the system, an 80% edge relative illumination and an 85% overall illumination uniformity are realized for a compact large-NA integrator with ${\rm NA} = {0.3}$ and thickness of 4.5 mm. An 88% edge relative illumination and a 92% overall illumination uniformity are realized for a small-NA integrator with ${\rm NA} = {0.15}$.

UCA-Based OAM Non-Orthogonal Multi-Mode Multiplexing

Electromagnetic waves carrying orbital angular momentum (OAM) can improve the spectral efficiency of communication systems by multiplexing a number of OAM modes. However, since being not able to perform water-filling power allocation and adaptive modulation for each sub-channel like closed-loop multiple-input multiple-output (MIMO) systems, the traditional orthogonal multi-mode OAM multiplexing system usually has poor bit error rate (BER) performance due to the inherent large divergence angle of high-order orthogonal OAM beams. Therefore, in this article we propose a non-orthogonal OAM (NO-OAM) multi-mode multiplexing scheme based on uniform circular array (UCA), which regulates the divergence angles of all non-orthogonal OAM beams to be the same, circumventing the problem that large beam divergence of high-order orthogonal OAM modes results in low received signal-to-noise ratio (SNR) at the receive UCA with a fixed aperture. Mathematical analysis and numerical simulations show that in contrast to the existing uniform concentric circular array (UCCA) beam adjustment scheme, the proposed NO-OAM scheme has slightly better beam adjustment effect but with only one UCA. Moreover, in contrast to the traditional orthogonal OAM multi-mode transmission, the proposed NO-OAM multi-mode multiplexing scheme has asymptotically equivalent channel capacity and much lower BER.

Demonstration of tailored energy deposition in a laser proton accelerator

In order to implement radiotherapy based on a laser accelerator, it is necessary to precisely control the spatial distribution and energy spectrum of the proton beams to meet the requirements of the radiation dose distribution in the three-dimensional biological target. A compact laser plasma accelerator has been built at Peking University, which can reliably generate and transport MeV-energy protons with a specified energy onto the irradiation platform. In this paper, we discuss several technologies for the accurate control of a laser-accelerated proton beam with large divergence angle and broad energy spread, including the determination of the beam source position with micron accuracy, a tuning algorithm for the transport line which we refer to as ``matching-image-point two-dimensional energy analysis'' to realize accurate energy selection, and the control of beam distribution uniformity. In the prototype experiment with low energy protons and 0.5-Hz irradiation rate, a tailored energy deposition is demonstrated, which shows the potential feasibility of future irradiation based on laser-accelerated proton beams.

Intrinsically reducing divergence angle of Cherenkov radiation from dielectric capillary.

Narrow-band terahertz (THz) Cherenkov radiation can be excited as a relativistic electron bunch passes through the dielectric capillary with sub-millimeter radius. However, due to the diffraction effect, the radiation will enter free space with a large divergence angle, which makes it difficult to collect the radiation energy efficiently. In this Letter, to deal with this challenge, we propose to add a new dielectric layer, which satisfies a special relationship with the electron velocity, between the metal coating and original dielectric layer in the capillary. According to numerical simulation and theoretical analysis results, the divergence angle of radiation is significantly suppressed, and the peak power density is also enhanced by over two orders. As a result, the transmission efficiency from the radiation source to the optical system can be increased to over 90%. We expect that this method will provide a new way to generate THz Cherenkov radiation.

Performance analysis and parametric studies on the primary nozzle of ejectors in proton exchange membrane fuel cell systems

ABSTRACT Ejectors are used for anode hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) systems, and the geometric parameters of the primary nozzle of ejectors have essential effects on the ejector performance. A 3D numerical model was established to investigate ejectors, and the reliability of the numerical model was verified by experiments. The operating characteristics of ejectors in the PEMFC system were analyzed by numerical simulation. Moreover, the effects of four geometry parameters (throat diameter, convergent angle, divergent angle, and length) on entrainment performance were studied. The results showed that the angle and length of the divergent zone have a significant influence on entrainment performance. A larger divergent angle may cause over-expanded under low power conditions, resulting in lower entrainment performance. For PEMFC systems with stable operating conditions or high entrainment requirements, a supersonic ejector with an appropriate divergent angle and length is recommended. Conversely, a convergent primary nozzle is suggested to be employed for the PEMFC systems with the wide operating power range. This study may provide a helpful reference for the design of ejectors used in fuel cell systems.

Experimental investigation of the dynamic cavitation behavior and wall static pressure characteristics through convergence-divergence venturis with various divergence angles

As a highly efficient and energy-saving cavitation method, Venturi cavitation is widely used in many industrial fields. This study synchronously investigated the cavity behavior and its corresponding wall static pressure characteristics in Venturi channels with various divergence angles to research the role of the divergence angle in cavity shape and the wall static pressure oscillation. Five rectangular Venturi channels with different divergence angles (4°, 6°, 8°, 10°, and 12°) were tested at the cavitation number (0.3–1.0). Based on the dynamic behaviour of gas–liquid interface, three cavity shedding types were identified: front shedding (I), central shedding (II) and tail shedding (III). A modified correlation for predicting average cavity length was proposed with the consideration of the effect of the divergence angle. Combined with the wall static pressure characteristics, as the divergence angle increased, the wall static pressure fluctuation in the Venturi became more intense. According to the wall static pressure oscillation characteristics, for the larger divergence angles (θ = 6°, 8°, 10° and 12°), the wall static pressure oscillation frequency was the same as the cavity shedding frequency and increased with the increase of the divergence angle. For smaller divergence angle (θ = 4°), no definite periodicity in pressure oscillation frequency could be observed.

Analysis of the tonal sound generation during phonation with and without glottis closure.

The human phonation is characterized by periodical oscillations of the vocal folds with a complete glottis closure. In contrast, a glottal insufficiency (GI) represents an oscillation without glottis closure resulting in a breathy and weak voice. In this study, flow-induced oscillations of silicone vocal folds were modeled with and without glottis closure. The measurements comprised the flow pressure in the model, the generated sound, and the high-speed footage of the vocal fold motion. The analysis revealed that the sound signal for vocal fold oscillations without closure exhibits a lower number of harmonic tones with smaller amplitudes compared to the case with complete closure. The time series of the pressure signals showed small and periodical oscillations occurring less frequently and with smaller amplitude for the GI case. Accordingly, the pressure spectra include fewer harmonics similar to the sound. The analysis of the high-speed videos indicates that the strength of the pressure oscillations correlates with the divergence angle of the glottal duct during the closing motion. Physiologically, large divergence angles typically occur for a pronounced mucosal wave motion with glottis closure. Thus, the results indicate a correlation between the intensity of the mucosal wave and the development of harmonic tones.

Enhanced relativistic electron beams intensity with self-generated resistive magnetic field

Active control of laser-produced relativistic electron beams (REB) transport is crucial for the success of the fast isochoric heating, which requires efficient energy transfer from REB to a small pre-compressed plasma core. In general, the laser-produced REB has a large divergence angle, thus only a small portion of REB interacts with the small core. We observed experimentally that the REB can be guided to a small area by using a resistive plastic cylinder buried in a conductive aluminum base. A two-dimensional hybrid numerical simulation shows that REB is confined in the plastic cylinder by a magnetic field generated spontaneously at the boundary between the resistive plastic and conductive aluminum.

Method to control near-field bowing of laser diode arrays by balancing the thermal-induced stress

Due to the thermal-induced stress during the bonding process, the emitters in a laser diode array (LDA) are vertically displaced, which causes the near-field bowing of a laser diode bar (i.e., the SMILE effect). Near-field bowing degrades the laser beam brightness, adversely affecting optical coupling and beam shaping, resulting in a larger divergence angle and a wider line after focusing and collimation. The mechanism of near-field bowing has been theoretically studied, in which the ratio of tensile strength between submount and heat sink has a great effect on the deformation of LDAs. Arm-wrestling between CuW submount and heat sink vividly describes that the deformation of LDAs changes as a function of the ratio of two materials’ tensile strength. We design a symmetrical structure that bonds another submount on the bottom of the heat sink to control the SMILE effect by balancing the acting force from the top of the heat sink. The deformation of the heat sink and LDAs are approximately zero when the thermal-induced stresses forced on the top and bottom of the heat sink are equal.

True-color restoration of reconstructed image in naked-eye 3D LED display based on eliminating optical dispersion

Naked-eye 3D LED displays are getting more advanced with the increase of LED screen density. And true-color restoration of reconstructed images in integral imaging LED displays is a new direction of research. Herein, when using a microlens array to produce white light, a 3D integral imaging LED display has serious optical dispersion. We propose a kind of optical array model in order to eliminate optical dispersion and restore the true colors of the reconstructed image. This model can effectively reduce chromatic aberration and crosstalk among the light rays by decreasing the large divergence angle of a LED’s single pixel point. The resolution of the reconstructed image can be improved simultaneously. Experimental results validate that compared with previous models, the current model can provide effective reduction of dispersion in LED integral imaging, and further analysis verifies the feasibility of the proposed method.