Progressive acceleration in the genetic algorithm by intragenerational mutation.

The intragenerational mutation of the genetic algorithm (IMGA) is proposed to actively broaden the searching space during the optimization process. The searching space is aggressively increased by expanding the variation of mutation rates of all individuals within each generation, leading to the reduction of the required number of iterations, improving the convergence speed and the enhancement factor.

Low-cost wavefront shaping via the third-order correlation of light fields.

In this Letter, inspired by the ghost imaging technique, we propose a wavefront shaping technique based on the third-order correlation of light fields (TCLF). Theoretically, we prove that if the light field fluctuation can be modeled by a complex Gaussian random process with a non-zero mean, the conjugate complex amplitude of the object and a focusing phase factor can be obtained by TCLF when using a single-point detector, which can support wavefront shaping. Experiments demonstrate that TCLF can achieve high-resolution wavefront shaping for scattered fields and scattering-assisted holography without additional operations such as optimization and phase shifting.

Fully continuous spiral phase plate for ultraintense optical vortices.

Ultraintense optical vortices carrying orbital angular momentum have attracted much attention in strong-field laser physics due to their spiral phase and hollow intensity. This Letter introduces a fully continuous spiral phase plate (FC-SPP) that enables the generation of an ultraintense Laguerre-Gaussian beam. An optimization design method based on the spatial filter technique and chirp-z transform is proposed to match the polishing processing and the tightly focusing performance. To enable its use in high-power laser systems, a large-aperture (200 × 200 mm2) FC-SPP has been fabricated on a fused silica substrate through magnetorheological finishing without the use of mask techniques. The far-field phase pattern and intensity distribution based on vector diffraction calculation were compared with those of ideal spiral phase plate and fabricated FC-SPP, which confirmed the high quality of the output vortex beams and their feasibility for producing high-intensity vortices.

Simple method to modulate the scattered light field under strong disturbance.

In this Letter, we propose a simple and robust method that we have named an optimal accumulation algorithm (OAA) to modulate a scattered light field. Compared with the simulated annealing algorithm (SAA) and genetic algorithm (GA), the OAA is very robust, that is to say it has a strong anti-disturbance capability. In experiments, the scattered light field through ground glass and a polystyrene suspension was modulated, where the polystyrene suspension supported a dynamic random disturbance. It was found that, even if the suspension is too thick to see the ballistic light, the OAA can still modulate the scattered field effectively, while the SAA and GA completely failed. In addition, the OAA is so simple that only addition and comparison are needed, and it can achieve multi-target modulation.

Hybrid resonance metasurface for a lithium niobate electro-optical modulator.

Electrically tunable metasurfaces can realize two-dimensional pixelated spatial light modulation and have a wide range of applications in optical switching, free-space communication, high-speed imaging, and so on, arousing the interest of researchers. Here, a gold nanodisk metasurface on a lithium-niobate-on-insulator (LNOI) substrate is fabricated and experimentally demonstrated as an electrically tunable optical metasurface for transmissive free-space light modulation. Using the hybrid resonance formed by the localized surface plasmon resonance (LSPR) of gold nanodisks and the Fabry-Perot (FP) resonance, the incident light is trapped in the gold nanodisk edges and a thin lithium niobate layer to realize field enhancement. In this way, an extinction ratio of 40% is achieved at the resonance wavelength. In addition, the proportion of hybrid resonance components can be adjusted by the size of the gold nanodisks. By applying a driving voltage of ± 2.8 V, a dynamic modulation of 135 MHz is achieved at resonant wavelength. The highest signal-to-noise ratio (SNR) is up to 48 dB at 75 MHz. This work paves the way for the realization of spatial light modulators based on CMOS-compatible LiNbO3 planar optics, which can be used in lidar, tunable displays, and so on.

Dye-enhanced third upconversion Raman overtone in the ultraviolet region under intense excitation of a 532 nm laser.

We report, to our best knowledge, the first observation of enhanced third upconversion Raman overtone of water in the ultraviolet region 240-380 nm by Rhodamine 6G (R6G) under intense excitation of a 532 nm laser. Its spectral peak is mostly around 288 nm. This ultraviolet spectrum has also been obtained for purified water on the Raman spectrometer LRS-3 and fluorescence spectrometer RF-5301PC, which have photomultiplier tubes. The spectral profile is approximately a triangle in most cases. Moreover, an intense and broad background is also observed to appear in the spectrum. Additionally, the conventional visible luminescence spectrum of R6G is discovered to coexist with the ultraviolet one. In comparison, the visible spectrum is much more intense.

Binary wavefront optimization using a simulated annealing algorithm.

We propose an idea using a simulated annealing algorithm for amplitude modulation to focus light through disordered media. Using 4096 independently controlled segments of an incident wavefront, the intensity of the target signal is enhanced 73 times over the original intensity of the same output channel. The simulated annealing algorithm and existing amplitude control algorithms for focusing through scattering media are compared experimentally. It is found that the simulated annealing algorithm achieves the highest enhancement when the number of iterations required for optimization is the same.

The electro-optic spatial light modulator of lithium niobate metasurface based on plasmonic quasi-bound states in the continuum.

Metasurface has attracted massive interest owing to its ability to control light arbitrarily in a wide range of applications, such as high-speed imaging, optical interconnection, and spectroscopy. Here we propose a free space light modulator combined with a gold grating metasurface based on lithium niobate (LiNbO3). The quasi-bound states in the continuum (quasi-BIC) are achieved in the metasurface. In addition, the plasmonic quasi-BIC and the guided-mode resonance (GMR) can be modulated by controlling the polarization of the incident light without any geometric adjustment. Thus, the working wavelength range from 1480 nm to 1620 nm was achieved, and the maximum resonance depth reached about 51% at the resonant wavelength. In addition, the insertion loss of the device was -2.8 dB at a wavelength of 1510 nm. Furthermore, the dynamic modulation speed reached up to 190 MHz and the highest signal-to-noise ratio (SNR) could reach about 49 dB at a frequency of 65 MHz. The data showed potential for the material for applications such as near-infrared imaging, beam steering, and free-space optical communication links.

Technique to improve the accuracy of the retrieval of aerosol size-distribution.

A technique to improve the accuracy of the retrieval of aerosol size-distribution is introduced. This technique includes a wavelength-selecting method and a "function model." The wavelength-selecting method is used to select the suitable wavelengths for the retrieval of aerosol size-distribution, and the function model is used to express the aerosol size-distributions with a fewer parameters. By using this technique, the accuracy of the retrieval of aerosol size-distribution can be improved.

[Observation and analysis of solar ultraviolet irradiance spectrum in Chengdu area].

The solar ultraviolet irradiance spectrum in Chengdu area from March to July in 2006 was observed with an ultraviolet CCD optical multi-channel analyzer. According to the observation results, some analysis of the basic characteristics was made. The analysis of the solar ultraviolet irradiance spectrum showed that the solar ultraviolet irradiance is weak in the morning and in the evening but strong at noon, reaches the strongest point in June, and reversely correlates with the change in SZA (solar zenith angle); the ratio of irradiance flux of UVB to UVA is less than 0.04, and usually, the ratio in the afternoon is bigger than that in the morning in sunny days; Fogs can cause the ratio to increase, the reason is that fogs show stronger influence on attenuation of UVA than UVB; Clouds absorbed the solar ultraviolet irradiance greatly.

[Selected enhancement of different order stokes lines of SRS by using fluorescence of mixed dye solution].

A new method to enhance the intensity of the different orders of Stokes lines of SRS by using mixed dye fluorescence is reported. The Stokes lines from the second-order to the fifth-order of CCl4 were enhanced by the fluorescence of mixed R6G and RB solutions in different proportions of 20:2, 20:13 and 20:40 (R6g:Rb), respectively. It is considered that the Stokes lines from the second-order to the fifth-order are near the fluorescence peaks of the three mixed solutions, and far from the absorption peaks of R6g and Rb, so the enhancement effect dominates the absorption effect; as a result, these stokes lines are enhanced. On the contrary, the first-order stokes line is near the absorption peak of RB and far from the fluorescence peaks of the mixed solutions, which leads to the weakening of this stokes line. It is also reported that the first-order, the second-order and the third-order Stokes lines of benzene were enhanced by the fluorescence of mixed solutions of R6g and DCM with of different proportions. The potential application of this method is forecasted.

[Optical multi-channel detection and analysis on solar ultra-violet irradiance spectrum].

The present paper reports a new type of ultraviolet CCD optical multi-channel analyzer and its application to detecting solar ultraviolet irradiance spectrum. Spectral detecting range of 200-1 100 nm, spectral resolution of 0.1 nm and detecting sensitivity of 0.02 lx were reached in this instrument. The solar spectra of UVB and UVA were measured in real time in Chengdu area. The measurement results have good correlation with the detection using normal solar ultraviolet irradiance detector. Primary analysis on the detection results of solar spectra in UVB and UVA indicated that in the morning and in the afternoon the irradiance of solar ultraviolet is smaller than that at noon, and reverse correlation holds for the change of SZA (Solar Zenith Angle). In different wavelength interval of UVA and UVB, generally, the radiation flux of long wavelength is greater than that of short. Clouds and aerosols in the atmosphere have important influence on ultraviolet irradiance.

[Study on fluorescence property of DCM with SDS in water solution excited by 532 nm laser].

The fluorescence property of DCM in water solution with added different concentration of SDS is reported. With increasing the concentration of SDS in water, the solubility of DCM and the fluorescence intensity increase. When the concentration of SDS increases from 0.025 to 0.5 mol x L(-1), the maximum fluorescence relative intensity is enhanced by a factor of 95. A powerful dye laser at wavelength of 648 nm was generated in the solution of DCM in water with SDS exited by a 532 nm laser. It shifts 13 nm compared with the dye laser wavelength of the solution of DCM in ethanol. And enhancement of SRS of C6H6 was achieved both in the solution of DCM in water with SDS and in the solution of DCM in ethanol. The result is that the second, the third and the fourth order Stokes of C6H6 are all enhanced. But the former mainly enhances the fourth order Stokes (632 nm) and the enhancement gain coefficient is 8.5, while the latter mainly enhances the third order Stokes (595 nm) and the enhancement gain coefficient is 2.5. The mechanism of solubility, fluorescence enhancement and its possible application are discussed.

[Measurement of time-dependent spectra excited by pulse laser using multi-fiber delayer and optical multi-channel analyzer].

A new method and technology for measuring time-dependent spectra excited by pulse laser was reported in the present paper, in which a multi-fiber delayer combined with a two dimensional CCD array detector was employed for collecting and processing the spectra. The multi-fiber delayer consists of five fibers with a length difference of 1-2 m (relative delay time 5-10 ns), and the optical multi channel analyzer is PARC OMA-4. The time-dependent spectra, i. e. the spectra of R6G dye laser, the SRS spectra of acetone, and the plasma emission spectra of metal Mo excited by a double frequency YAG pulse laser with a time resolution of 5 ns were obtained.

[Measurement of NO2 concentration in atmosphere in Chengdu by solar spectra].

In the present paper, a new improved method for measuring NO2 concentration of atmosphere by using differential optical absorption spectroscopy of solar spectrum was reported. The sample solar spectra were collected in Chengdu city and Xiling Mountain respectively by a CCD optical multi-channel analyzer. With the upper atmosphere solar spectrum as the reference spectrum, by fitting the sample spectrum and the reference spectrum using least-square method in five spectrum ranges, the various NO2 concentrations (vertical column density) of 3.1 x 10(16) to 5.8 x 10(16) (molecule x cm(-2)) in Chengdu city and 0.7 x 10(16) to 1.0 x 10(16) (molecule x cm(-2)) in Xiling Mountain were obtained respectively. The NO2 concentrations of atmosphere showed an increasing tendency with the rising temperature.

[Study on sodium lauryl sulfate (SDS) induced fluorescence enhancement of rhodamine 6G in water solution excited by 532 nm laser].

It is reported that the Rhodamine 6G fluorescence in water solution changes with different concentration SDS excited by a 532 nm laser. A small amount of SDS in Rhodamine 6G water solution will reduce the intensity of fluorescence. More SDS enhances R6G fluorescence. The enhancement ratio can reach up to 3.1 when SDS concentration is 6 x 10(-2) mol L(-1) in 5 x 10(-5) mol L(-1) R6G water solution. Dye laser threshold decreases when SDS concentration is 2 x 10(-2) mol x L(-1) in 1 x 10(-4) mol x L(-1) R6G water solution. The physical mechanism of the phenomena is analyzed by the absorption spectra of different concentration R6G water solutions and the fluorescence spectra of R6G water solutions adulterated with different concentration SDS.

[Double light beam multi-channel analysis for laser induced fluorescence spectroscopy].

The incident pulse intensity wave will cause the induced fluorescence wave, which will lead to the obvious error of experiment results. A double-light-beam correlation method between the incident laser and the fluorescence was used to decrease such error efficiently in the experiments. A good correlation factor over 0.9 was obtained by the method in the experiment of R6G fluorescence enhanced by SDS. The method is better than sampling-averaging method when the incident laser intensity has more waves.

[Investigations of transient time-dependent spectral multi-channel measurement for shocked KCl crystal].

In this paper, the authors reported a new method for measuring transient time-dependent spectra using multi-fiber delay coupler and optical multi-channel analysis technique. The fiber delay coupler consists of five fibers with different lengths and its time-delay between two fibers is determined by the different fiber lengths. The light beams that came from the fiber coupler were coupled by a lens system into the slit of a spectrograph and formed a spectral pattern on the focus plane of the spectrometer. A two-dimensional CCD detector converted the optical pattern into an electrical pattern, and then the transient time-dependent spectra were obtained by a personal computer. The experimental setup was constructed, and the transient time-dependent spectra were measured for KCl crystal shocked by a high speed pill. The time resolution was 20 ns, and the spectral intensity resolution reached 1/18 bit.