Intensity Distribution Of Light Field Research Articles

Beam quality measurement and image analysis of RF optical emission system

With the development of radio-over-fiber (ROF), beam quality is also an important parameter in evaluating ROF systems. Therefore, this paper selects the low-frequency to very high frequency (VHF) direct modulated optical emission system to verify its feasibility and excellent performance. It then analyzes the beam quality and image processing. In this paper, MATLAB is selected for the theoretical simulation, then CMOS is used to collect light spots, RayCiV2.5 is used to Gaussian fit the light field intensity distribution, and finally the ideal and actual light spot parameters are compared. Due to the influence of noise, this paper also preprocessed the image by brightness adjustment, filtering, edge fitting, etc. It proposed a fast two-sided filtering algorithm, which obtained a high peak signal-to-noise ratio (PSNR) and strong applicability. The results show that the edge-mode rejection ratio is as high as 33.6 dB, the beam quality is good, and it can be well applied in ROF. The M2 factor is 2.75, the optical field intensity Gaussian fit is 99.8 %, and the signal-to-noise ratio (SNR) is as high as 54.7 dB. Moreover, the image is robust after fast bilateral filtering.

Formation controllable two-dimensional surface optical lattices

The evanescent light field created by total internal reflection at a dielectric-vacuum interface has tight spatial confinement and high local intensity. These properties become more robust when a dual layer of dielectric thin films with different thicknesses is deposited on a planar dielectric surface. Optical construction is promising in nanoscale trapping of absorbed atoms congregating at extreme light field intensity distribution regions on the dielectric surface. Here, we theoretically demonstrate the controllable two-dimensional surface optical lattices based on the evanescent electric field generated by the Hermite-Gaussian light beam. By considering the coupling of lattice to quadrupole-active atomic transitions, we show that the topologies cannot just have high stability, but also the optical potential deep, and thus the dynamic trapping can be governed by changing the design parameters of the optical construction. We expect that this study may contribute to providing another unique method for fabricating spatially complicated two-dimensional nanostructures.

Gain Modeling and Numerical Simulation of Fiber Amplifier

As optical communication technology has been developing fast these years, its application in S-band has been valued by people, especially in the field of WDM/DWDM. The energy structure-e in Tm3+exist the transition which can meet the S-band and S+-band. Although the energy structure of ions are very complex, the fiber amplifier is an important device for the S+-band optical amplification. And its research will be very significant for further broadening the optical communication bandwidth. Fiber amplifiers have become a new hot spot for optical fiber communication devices. This paper mainly do analysis, simulation and comparison about the semiconductor laser mufti-core pigtail outputting light field intensity, as well as the outputting light field intensity distribution of LD mufti-core pigtail single-lens and dual-lens coupled. This paper analyzes fiber amplifier performance based on the rate equation, transfer equation and simulations.

Fabrication of nanostructure on Au nano-film by nanosecond laser coupled with cantilevered scanning near-field optical microscopy probe

Diffraction limit has been the constraint of the nanostructure fabrication. Because the scanning near-field optical microscopy (SNOM) can work in the evanescent near-field region, its application in nano-processing has received extensive attention from researchers globally. In this paper, we combined nanosecond laser with cantilevered SNOM probe. Utilizing the high precision of the confinement and enhancement effect of probe tip and the high instantaneous energy of the laser, we realized nanostructure fabrication and in situ detection on Au nano-film. Feature sizes down to 47 nm full width at half maximum were fabricated. We investigated the laser propagation through the SNOM tip aperture and the light field intensity distribution on the surface of substrate theoretically. The calculation results demonstrate that the laser is highly restricted within the SNOM aperture and enhanced on the exit plane at the rim of aperture. After the transmission, the light field intensity distribution on the surface of the Au nano-film was enhanced due to the localized surface plasmon resonance. The thermal distribution on the surface of Au nano-film indicates that the peak of the temperature distribution appeared at the surface right underneath the center of the aperture. It is proved that the simulation results are consistent with the experimental results.

Research on sensing characteristics of diamond multilayer waveguide structure racetrack micro-ring resonator

A racetrack micro-ring resonant cavity sensor based on the diamond's material is proposed in this paper. In the model, the vertical-section of the waveguide adopts a five-layer ridge-type waveguide structure based on CH3NH3PbI3, SiO2 and diamond, i.e. CH3NH3PbI3-SiO2-Diamond-SiO2-CH3NH3PbI3. First, on the basis of the resonant principle and coupled mode theory, this study investigated the light field intensity distribution characteristics of the integral resonant cavity, the longitudinal section of a single straight waveguide, the racetrack micro-ring, and the longitudinal section of the straight waveguide by using the finite element method in COMSOL. The analysis shows that the introduction of CH3NH3PbI3 as an isolation layer can avoid the light scattering loss and leakage loss, and significantly enhance the filtering performance. In addition the sensing characteristics of the Add-drop racetrack resonator were further studied. Results showed that the structure could achieve a quality factor of 105, and the sensitivity could reach 14833.33 dB/RIU. In the detection system with a signal-to-noise ratio of 30 dB, the detection limit was 2.02 × 10−7 RIU. Compared with the traditional All-pass single micro-ring resonator, the proposed structure shows advantages of high tenability, high sensitivity and low detection limit.

Broadband and wide-angle antireflective subwavelength microstructures on zinc sulfide fabricated by femtosecond laser parallel multi-beam.

The subwavelength microstructures (SWMS) on the surface of ZnS for antireflection in an infrared band have been theoretically designed and experimentally fabricated. The finite difference time domain (FDTD) simulation has been utilized to optimize geometry for obtaining high transmittance of SWMS. Then, during simulation for light field intensity distribution, the inner of SWMS emerges location and wavelength dependent light resonant region, which can be explained by Wood-Rayleigh (WR) law. Furthermore, according to refractive index gradient formation and light field coupling effect, the grating period and height are capable of regulating the band selection of antireflection and value of the transmittance, respectively. In addition, a rapid facile approach based on femtosecond laser parallel multi-beam has been proposed to experimentally realize the designed and optimal structures. The depth, period, and embedded nano-gratings of fabricated SWMS are tunable by controlling laser-processing parameters for antireflection in the wavelength of 8 μm-12 μm. Finally, the broadband and wide-angle antireflective SWMS on ZnS as well as robust mechanical strength and hydrophobicity have been achieved, expecting to be of great potential in an optoelectronic device application.

Spin-orbit transformation of Bessel light beams by electrically controlled liquid-crystal elements

The features of the transformation of linearly polarized Bessel light beams during their propagation through an electrically controlled liquid-crystal cell are studied theoretically and experimentally. Conditions were determined for realizing the spin–orbit transformation of Bessel light beams, which manifests itself through changes in polarization, phase, and spatial structure of the Bessel beam with the possibility of obtaining an azimuthally modulated light field intensity distribution.

General design basis for a final optics assembly to decrease filamentary damage**Project supported by the National Natural Science Foundation of China (Grant No. 60707019).

The high-power laser beam in the final optics assembly of high-power laser facilities is often modulated by contamination particles, which may cause local high light intensity, thereby increasing the filamentary damage probability for optical components. To study the general design basis for a final optics assembly to decrease the risk of filamentary damage, different-sized contamination particles deposited on a component surface are simulated to modulate a 351-nm laser beam based on the optical transmission theory, and the corresponding simulation results are analyzed statistically in terms of the propagation characteristic and the light field intensity distribution of the modulated laser beam. The statistical results show that component thickness and distance between components can to some extent be optimized to reduce the appearance of local high light intensity, and the general design basis of component thickness and arrangement are given for different control levels of particle sizes. Moreover, the statistical results can also predict the laser beam quality approximately under the existing optics design and environmental cleanliness. The optimized design for final optics assembly based on environmental cleanliness level is useful to prolong the lifetime of optics and enhance the output power of high-power laser facilities.

非相干LED光源产生高阶Bessel光束

The ideal high order Bessel beams was generated by monochromatic green LED light source for the first time. A novel method using cross-spectral density function and superposition of multi-wavelength was proposed to calculate the intensity distribution of light field emitted from the green LED then through the spiral phase plate and the axicon. And the cross-section intensity distribution along the optical axis based on this method was simulated. An experimental facility was designed to demonstrate the theory. The result showed that the high order Bessel beams could be obtained from the green LED light source by using the aperture to improve the spatial coherence of the light field emitted from the green LED. The cross-section intensity distribution of the experimental result, the size of the center dark spot and the non-diffraction distance were accorded well with the theoretical simulation and calculation. The research result offered the theoretical and experimental basis for the micromanipulation of particles by using incoherent light.

由单轴散射体构成的一维无序介质中的局域模

Localized modes in one-dimensional (1D) media with uniaxial scatterers that are assumed to be order in spatial location but disorder in spatial orientation of their optical axis are investigated. Based on the holistic effect model in random laser, i.e., the random laser is due to the interaction of the complex localized modes in active random media with local aperiodic quasi-structure with appropriate pump light, a physical model on this type of random media is found. Its disorder degree is defined by D=no/ne. Then, the typical transmission spectrum through the random media and the light field intensity distribution corresponding to the defect modes in photonic band-gap are calculated numerically by means of the transfer matrix method, and the condition that the localized mode appears is discussed. Results show that the medium disorder plays an important role in determining the lightwave state. The localized state appears when the medium disorder is strong enough, and a new mechanism creating random laser phenomenon is brought forward.

Photoelectric device for stroke induction in the control of dials and coded disks

Currently photoelectric devices for stroke induction are widely used in systems for controlling dials (coded disks). As a rule the induction is effected with the aid of a photoelectric microscope (PEM) with a movable slit, located in the plane of analysis, i.e., in the plane of the sensitive area of the phototransducer. To eliminate error associated with variation in the width of the stroke, the induction is performed on its center [1]. Stroke induction using a PEM requires special conditions and accessories. First, they place strict requirements on the initial exposure of the optical axis of the PEM relative to the axis of rotation of the attachment and on the focusing of the microscope on the surface of the piece being tested. Second, when the axis of rotation of the attachment is not parallel to the optical axis of the PEM (the inclination of the reading microscope) an additional error appears due to wobble in the axes of the rotating attachment and sphericity in the dial, since these factors cause variation in the distance of the diaI from the microscope [2]. Third, the PEM have significant structural parameters (mass, dimensions) and should be equipped with complex electronic units [3]. These factors to a significant degree limit application of PEM in systems for the dynamic control of dials and coded disks constructed, for example, on the basis of a laser goniometer [4] the speed of rotation of the rotating base of which is equal to 90~ Fiber optics has permitted development of light field intensity distribution gauges for relative motion of the gauge and the field. Figure 1 shows a measurement diagram of such a device. Fiber light conductor 2 is mounted on carrier 3. The input end of the light conductor is optically treated and transparent to the wavelength of the field being tested. The output end of the light conductor is connected optically to the sensitive area of phototransducer 1 and mechanically to its chassis. The design incorporates special measures to exclude the incidence of background radiation onto the sensitive area of the phototransducer. Moreover, the gauge is equipped with a device 5 for rotation around two mutually orthogonal axes and a device 4 for translation along a third axis which is perpendicular to the first two axes and which coincides with the axis of the fiber light conductor. This light field intensity gauge permits practical application of classical diffraction theory to problems of dial stroke (coding path window) induction. The dial is a plane-parallel plate with strokes the dimensions of which may vary within broad limits for different dials. Independently of the method of applying the stroke to the surface of the dial the stroke may be regarded as an opaque screen with finite dimensions and, without loss of generality, the rectilinearity of the edge of any stroke may be assumed. The portion of the dial with the strokes is shown in Fig. 1. Here 2h is the width of the stroke, 2H is its height, M is the distance between neighboring strokes along the diameter of the graduated circumference. Let us introduce a rectangular coordinate system X, Y, Z, the center of which is the point O which coincides with the center of symmetry of the stroke, while the axes OX and OY are directed along the short 2h and the long 2H sides of the stroke, respectively. The OZ axis is perpendicular to the surface of the stroke (screen). Let us connect a linear laser equipped with a collimating system and generating in space a light field of intensity E to the gauge in such a way that the optical axes of the laser and the gauge coincide and coincide with the O'Z" of the fixed rectilinear coordinate system X'Y'Z" associated with the gauge. The input end of the fiber light conductor lies in the X'O'Y" plane. The gauge registers the field intensity I r determined by the square of the modulus I El 2 as a constant quantity. Into the gap between the laser mirror and the input end of the fiber light conductor we introduce the dial in such a way that the axes of the XYZ and X'Y'Z" coordinate systems are collinear and the distance OO" is equal to L. Then, taking into account that for dials and coding disks 2H >> 2h in accordance with [5] we write the field intensity beyond the stroke in the near diffraction zone (taking into account that Ir(Y') = const) as