Showing papers in "Chinese Optics Letters in 2013"
TL;DR: In this paper, the phase mask technique was used for on-line writing identical fiber Bragg grating (FBG) arrays using the phase masks technique and the results showed that the FBG arrays obtained in the optimal process (drawing speed of 12 ± 0.15 m/min and average tension of 38.2 g) have a central wavelength bandwidth of less than 0.1 nm and an average reflectivity of 0.26%.
Abstract: We investigate the on-line writing identical fiber Bragg grating (FBG) arrays using the phase mask technique. Given the limitation of laser power, the energy density uniformity and the horizontal width of the writing spot cannot be further optimized. The results show that the FBG arrays obtained in the optimal process (drawing speed of 12 ± 0.15 m/min and average tension of 38.2 g) have a central wavelength bandwidth of less than 0.1 nm and an average reflectivity of 0.26%. Thus, the phase mask method is a promising alternative for on-line writing identical FBG arrays.
95 citations
TL;DR: In this paper, the authors showed that Er3+/Pr3+-codoped germanate glasses can achieve 2.7 mm emission enhancement at 2.5 mm when pumped by a 980-nm laser diode.
Abstract: Emission enhancement at 2.7 mm is observed in Er3+/Pr3+-codoped germanate glasses when pumped by a 980-nm laser diode. Significant reductions in 1.5-mm emission and upconversion intensity indicate efficient energy transfer between Er3+ and Pr3+; the energy transfer efficiency is as high as 77.4%. The mechanisms of energy transfer are discussed in detail. The calculated emission cross-section of Er3+/Pr3+-codoped germanate glass is 8.44×10-21 cm2, which suggests that Er3+/Pr3+-codoped germanate glass can be used to achieve efficient 2.7-mm emission.
58 citations
TL;DR: The simulation results show that the original codes can be recovered with a high security of signal transmission using the Manchester method.
Abstract: We investigate the nonlinear behaviors of light recognized as chaos during the propagation of Gaussian laser beam inside a nonlinear polarization maintaining and absorption reducing (PANDA) ring resonator system. It aims to generate the nonlinear behavior of light to obtain data in binary logic codes for transmission in fiber optics communication. Effective parameters, such as refractive indices of a silicon waveguide, coupling coefficients (κ), and ring radius ring (R), can be properly selected to operate the nonlinear behavior. Therefore, the binary coded data generated by the PANDA ring resonator system can be decoded and converted to Manchester codes, where the decoding process of the transmitted codes occurs at the end of the transmission link. The simulation results show that the original codes can be recovered with a high security of signal transmission using the Manchester method.
45 citations
TL;DR: In this article, the authors used melt-quenching technique to prepare co-doped tellurite glasses with eight bands in the wavelength range of 350-2 000 nm, which correspond to the transitions from ground level 6 H 5/2 to various excited states of the Sm 3+ ion.
Abstract: Sm 3+ /Yb 3+ co-doped tellurite glasses are prepared by melt-quenching technique.
The density of the glasses varies between 4.65 and 4.84 g/cm 3 . The optical absorption spectra
consist of eight bands in the wavelength range of 350-2 000 nm, which correspond to the transitions
from ground level 6 H 5/2 to the various excited states of the Sm 3+ ion. Energy band gaps vary in the
range of 2.73-2.91 eV, and the Urbach energy ranges from 0.21 to 0.27. Emission spectra exhibit four
peaks originating from the 4 G 5/2 energy level centered at 576, 613, 657, and 718 nm. Quenches in
emission bands may be due to the energy transfer from the Sm 3+ to Yb 3+ ions.
43 citations
TL;DR: A lightweight and wearable spatial-multiplexed dual focal-plane head-mounted display that can adjust the accommodation cue in accordance with the convergence cue as well as generate the retinal blur cue is designed.
Abstract: Accommodation and convergence play critical roles in the natural viewing of three-dimensional (3D) scenes, and these must be accurately matched to avoid visual fatigue. However, conventional stereoscopic head-mounted displays lack the ability to adjust accommodation cues. This is because they only have a single, fixed image plane, but the 3D virtual objects generated by a pair of stereoscopic images are displayed at different depths, either in front or behind the focal plane. Therefore, in order to view objects clearly, the eyes are forced to converge on those objects while maintaining accommodation fixed on the image plane. By employing freeform optical surfaces, we design a lightweight and wearable spatial-multiplexed dual focal-plane head-mounted display. This display can adjust the accommodation cue in accordance with the convergence cue as well as generate the retinal blur cue. The system has great potential applications in both scientific research and commercial market.
33 citations
TL;DR: A room division multiplexing (RDM)-based hybrid visible light communication (VLC) network for realizing indoor broadband communication within a multi-room house is presented and the experimental platform demonstrates the effectiveness of the proposed hybrid architecture.
Abstract: A room division multiplexing (RDM)-based hybrid visible light communication (VLC) network for realizing indoor broadband communication within a multi-room house is presented. The downlink information is transmitted by light-emitting diode lamps, whereas the uplink information is transmitted through WiFi. RDM is introduced to improve the VLC network throughput; in addition, the associated signaling localization and active handoff mechanisms are designed for implementation. The experimental platform demonstrates the effectiveness of the proposed hybrid architecture, along with the RDM and active handoff mechanisms.
32 citations
TL;DR: In this article, the authors proposed a new mechanism/scheme to explain the ultrafast population inversion of molecular ions which takes place in a time scale comparable to the femtosecond laser pulse.
Abstract: We propose a new mechanism/scheme to explain the ultrafast population inversion of molecular ions which takes place in a time scale comparable to the femtosecond laser pulse. The nonlinear pumping process including the pump photons and the self-generated harmonic photons of the pump laser would be responsible for building up population inversion to realize remote molecule lasers in femtosecond laser filaments in gases. It is shown that the remote laser emissions in molecular ions of gases may be a universal process in the femtosecond laser filament.
31 citations
TL;DR: In this article, a diffuse light source is designed based on the physics analysis of light reflection, and the distribution of intensity is simulated according to a known model to verify the illumination uniformity.
Abstract: Specular and strong reflections are the main problems encountered during part image defect inspection of shiny or highly reflective surfaces. In this letter, we propose an improved illumination method for defect inspection. A diffuse light source is designed based on the physics analysis of light reflection. The distribution of intensity is simulated according to a known model to verify the illumination uniformity of the source. Experiments show that defect expressivity when using the proposed illumination method has a better performance. The optical model is not only suitable for the defect detection of metal balls but also for the defect detection of planes and cylinders.
30 citations
TL;DR: In this paper, the authors demonstrate the generation of an array of optical bottle beams by employing multiple self-accelerating Airy beams, all with inward acceleration directed towards the center.
Abstract: We experimentally demonstrate the generation of an array of optical bottle beams by employing multiple self-accelerating Airy beams. This kind of optical bottle array is created by superimposing eight Airy beams along a circle, all with inward acceleration directed towards the center. In addition, we demonstrate stable trapping of multiple absorbing glassy carbon particles using the proposedoptical bottle array.
30 citations
TL;DR: In this paper, a fiber Bragg grating-based accelerometer with a fully metalized package is presented, which has a flat frequency response over a 1-kHz bandwidth, with a resonance frequency of 3.6 kHz, wide linear measurement range of up to 8 g, and sensitivity of 1.7 pm/g.
Abstract: A fiber Bragg grating-based accelerometer with a fully metalized package is presented. Magnetron sputtering and electroplating techneques are successively adopted to metalize bare SiO2 fiber with a single Bragg grating. Laser welding techneque is adopted to fix the metal-coated fiber on the sensor component to obtain a fully metallized package without adhesives. Vibration test results demonstrate that the accelerometer has a flat frequency response over a 1-kHz bandwidth, with a resonance frequency of 3.6 kHz, wide linear measurement range of up to 8 g, and sensitivity of 1.7 pm/g.
29 citations
TL;DR: In this article, a high repetition rate mid-IR laser source suitable for the next generation of high-field physics experiments is reported, which can deliver carrier-envelope phase (CEP)-stable 67-fs duration optical pulses with up to 18- \mu J output energy at 160-kHz repetition rate.
Abstract: Progresses on the development of a high repetition rate mid-IR laser source suitable for the next generation of high-field physics experiments are reported. The presented optical parametric chirped pulse amplification (OPCPA) source currently delivers carrier-envelope phase (CEP)-stable 67-fs duration optical pulses with up to 18- \mu J output energy at 160-kHz repetition rate. The focusability of the output beam (M2~2) enables peak intensities exceeding 1014 W/cm2 and the record output energy stability-below 1% power fluctuation over 4.5 h makes this source a key enabler for the strong field physics community.
TL;DR: The recent advances of two-photon microscopy technology including novel laser sources, new image acquisition paradigms, and microendoscopic imaging systems are reviewed and the capabilities of TPM imaging of biological relevant molecules such as nicotinamide adenine dinucleotide (NADH), flavin adenines din nucleotide (FAD), and reactive oxygen species (ROS).
Abstract: In the past two decades, two-photon microscopy (TPM) transforms biomedical research, allowing nondestructive high-resolution fluorescent molecular imaging and label-free imaging in vivo and in real time. Here we review the recent advances of TPM technology including novel laser sources, new image acquisition paradigms, and microendoscopic imaging systems. Then, we survey the capabilities of TPM imaging of biological relevant molecules such as nicotinamide adenine dinucleotide (NADH), flavin adenine dinucleotide (FAD), and reactive oxygen species (ROS). Biomedical applications of TPM in neuroscience and cancer detection are demonstrated.
TL;DR: In this article, an efficient high-power high-brightness 2-mu m continuous-wave (CW) laser with double-end, diffusion-bonded Tm, Ho:YVO4 crystal cooled with liquid N2 was demonstrated.
Abstract: This letter demonstrates an efficient high-power high-brightness 2-\mu m continuous-wave (CW) laser with double-end, diffusion-bonded Tm, Ho:YVO4 crystal cooled with liquid N2. The reduction in thermal stress in the composite Tm, Ho:YVO4 rod enabled the laser to achieve a laser output power of 23.4 W at 2.05 \mu m, which is 1.37 times higher than that of the non-composite Tm, Ho:YVO4 rod. The corresponding slope efficiency is 37.3% and the optical-optical conversion efficiency is 35.4%. The beam quality M2 factor is about 1.85 at 20 W output level with circularly symmetric beam spot.
TL;DR: In this article, the nonlinear optical properties of polyvinylcarbozole (NLO) guest-host poly(N-vinyl carbozoles)/disperse orange 3 (PVK/DO3), PVK/disperseorange 13 (PVP/DO13), and PVK-disperse-orange 25 (PVL/DO25) as a solution at different concentrations and as a thin-film sample are studied using continuous wave z-scan system at 532 nm.
Abstract: The nonlinear optical (NLO) and optical limiting (OL) properties of three new structures of organic NLO guest-host Poly(N-vinylcarbozole)/disperse orange 3 (PVK/DO3), PVK/disperse orange 13 (PVK/DO13), and PVK/disperse orange 25 (PVK/DO25) as a solution at different concentrations and as a thin-film sample are studied using continuous wave z-scan system at 532 nm. The open-aperture z-scan data of the NLO materials in the solution and thin-film samples displayed two-photon and saturable absorptions, respectively. The PVK/DO13 exhibites the largest and best values of the nonlinearities, such as n2, β, χ(3), compared with those of PVK/DO3 and PVK/DO25. This nonlinearity increases as the concentration increases. The results indicate that these NLO materials are good candidates for optical switching and OL devices.
TL;DR: In this paper, three possible design options of laser plasma acceleration (LPA) for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-kJ, 500-fs PETawatt Aquitane Laser (PETAL) at French Alternative Energies and Atomic Energy Commission (CEA).
Abstract: We present three possible design options of laser plasma acceleration (LPA) for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-kJ, 500-fs PETawatt Aquitane Laser (PETAL) at French Alternative Energies and Atomic Energy Commission (CEA). Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 =1 .4(1.6), acceleration to 100 (130) GeV requires a 30-m-long plasma waveguide operated at the plasma density ne ≈ 7 × 10 15 cm −3 with a channel depth Δn/ne = 20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0 2 can reach 100 GeV approximately in a 36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a 1π-mm-mradlevel transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0 = 4, radiative energy loss becomes 10% at the maximum energy of 90 GeV. OCIS codes: 350.4990, 350.5400. doi: 10.3788/COL201311.013501.
TL;DR: The principle and some recent applications of Doppler optical coherence tomography (OCT) are reviewed and the advances of the phase-resolved Dopplers OCT method are described.
Abstract: We review the principle and some recent applications of Doppler optical coherence tomography (OCT). The advances of the phase-resolved Doppler OCT method are described. Functional OCT algorithms which are based on an extension of the phase-resolved scheme are also introduced. Recent applications of Doppler OCT for quantification of flow, imaging of microvasculature and vocal fold vibration, and optical coherence elastography are briefly discussed.
TL;DR: In this paper, the ant colony optimization (ACO) algorithm based on the probability density function is applied for the retrieval of spherical particle size distribution (PSD), and the spectral extinction data based on Mietheory and the Lambert-Beer Law served as input for estimating five commonly use monomodal PSDs.
Abstract: The ant colony optimization (ACO) algorithm based on the probability density function is applied
for the retrieval of spherical particle size distribution (PSD). The spectral extinction data based on the Mie
theory and the Lambert-Beer Law served as input for estimating five commonly use monomodal PSDs, i.e.,
Rosin-Rammer distribution, normal distribution, logarithmic normal distribution, modified beta distribution,
and Johnson's SB distribution. The retrieval results show that the ACO algorithm has high feasibility and
reliability, thus providing a new method for the retrieval of PSD.
TL;DR: In this article, a multi-view 3D display with high brightness based on a parallax barrier is proposed, which has a gradient transmittance with enhanced frequency characteristic, which indicates that the aperture ratio can be increased, thereby improving brightness.
Abstract: A multi-view three-dimensional (3D) display provides a more realistic experience than a two-view 3D display. Therefore, a multi-view 3D display with high brightness based on a parallax barrier is proposed. The parallax barrier in the 3D display has a gradient transmittance with enhanced frequency characteristic, which indicates that the aperture ratio of the parallax barrier can be increased, thereby improving brightness. Gradient transmittance is also helpful in reducing crosstalk. A prototype of the 3D display is developed. Experimental result shows that the 3D display has higher brightness than a conventional display. In addition, crosstalk is limited at a low level.
TL;DR: In this article, a Yb-doped silica glass fiber laser with a core made by sol-gel method is reported, achieving a maximum power of 1.14 W with a pump power of 5.46 W at a wavelength of 976 nm.
Abstract: A Yb-doped silica glass fiber laser with a core made by sol-gel method is reported. The maximum power of 1.14 W is obtained with a pump power of 5.46 W at a wavelength of 976 nm. The slope efficiency is 34%. The refractive index fluctuation across the core is below 5×10-4 at a doping level of Yb 0.15 mol%, A2O3 4.0 mol%, and P2O5 2.0 mol%. High background attenuation of 6 dB/m at 1 053 nm limites the slope efficiency and maximum output power.
TL;DR: In this paper, a digital holographic microscope is presented, wherein the sample is illuminated by structured light to enable the capture of additional object spatial frequencies, and reconstructed images with increased spatial resolution are obtained by separating and synthesizing bandwidths of different frequency regions in the Fourier domain.
Abstract: We present a digital holographic microscope wherein the sample is illuminated by structured light to enable the capture of additional object spatial frequencies. Reconstructed images with increased spatial resolution are obtained by separating and synthesizing bandwidths of different frequency regions in the Fourier domain. The theoretical analysis and experimental results are presented.
TL;DR: In this paper, laser-induced breakdown spectroscopy (LIBS) was used to determine the total nitrogen (TN) and total phosphorus (TP) in soil using the line intensity of the analyte element and element concentration.
Abstract: Laser-induced breakdown spectroscopy (LIBS) is used to determine the total nitrogen (TN) and total phosphorus (TP) in soil. Quantitative determinations are conducted using the line intensity of the analyte element and element concentration. Calibration models are obtained using ten samples for TN and seven samples for TP. The rest samples are used to validate the results. Strong linear correlations are obtained from the determined TN and TP concentrations. LIBS is a powerful tool for analyzing soil samples to determine nutrient elements by selecting calibration and validation samples with similar matrix composition.
TL;DR: A novel ray tracing planning method combined with successively optimizing even and odd power coefficients of phase polynomials in turn is proposed, which can successfully design a non-rotational asymmetry CGH for the tests of FOSs with an F-θ lens.
Abstract: Freeform optical surfaces (FOSs) will be the best elements in the design of compact
optical systems in the future. However, it is extremely difficult to measure freeform surface with
sufficient accuracy, which impedes the development of the freeform surface. The design and
fabrication of computer-generated hologram (CGH), which has been successfully applied to the tests
for aspheric surfaces, cannot be directly adopted to test FOSs due to their non-rotational
asymmetry. A novel ray tracing planning method combined with successively optimizing even and odd
power coefficients of phase polynomials in turn is proposed, which can successfully design a
non-rotational asymmetry CGH for the tests of FOSs with an F-θ lens. A new eight-step
fabrication process is also presented aiming to solve the problem that the linewidth on the same
circle of the CGH for testing freeform surface is not uniform. This problem cannot be solved in the
original procedure of CGH fabrication. The test results of the step profiler show that the CGH
fabricated in the new procedure meets the requirements.
TL;DR: In this paper, a switchable Q-switched and mode-locked erbium-doped fiber laser (EDFL) operating in the L-band region using the nonlinear polarization rotation effect was demonstrated.
Abstract: We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser (EDFL) operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 μs, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least 10 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.
TL;DR: Wang et al. as discussed by the authors proposed that China may need to invest more to develop top down nanoscale integration capability (more on processing technology) to sustain the development in silicon photonics and to elevate its own industry structure.
Abstract: Silicon photonics has become one of the major technologies in this very information age. It has been intensively pursued by researchers and entrepreneurs all over the world in recent years. Achieving the large scale silicon photonic integration, particularly monolithic integration, is the final goal so that high density data communication will become much cheaper, more reliable, and less energy consuming. Comparing with the developed countries, China may need to invest more to develop top down nanoscale integration capability (more on processing technology) to sustain the development in silicon photonics and to elevate its own industry structure.
TL;DR: A number of works, that have been developed based on the framework of the WRP and the VDP, are reviewed, that enable a hologram to be processed with classical image processing techniques normally unsuitable for handling holographic information.
Abstract: The wavefront recording plane (WRP), subsequently generalized to be known as the virtual diffraction plane (VDP), is a recent concept that has been successfully deployed in fast generation and processing of digital holograms. In brief, the WRP and its extension, the VDP, is a hypothetical plane that is located between the hologram and the object scene, and which is at close proximity to the latter. As such, the fringe patterns on the hypothetical plane are carrying the holistic information of the hologram, as well as the local optical properties of the object scene. This important property enables a hologram to be processed with classical image processing techniques that are normally unsuitable for handling holographic information. In this paper we shall review a number of works, that have been developed based on the framework of the WRP and the VDP.
TL;DR: In this paper, the direct relationship between femtosecond Ti-sapphire laser induced remote filaments and terahertz (THz) pulses was investigated in a two color filament.
Abstract: Broadband and energetic terahertz (THz) pulses can be remotely generated in air through filamentation. We review such THz generation and detection in femtosecond Ti-sapphire laser induced remote filaments. New results are presented on the direct relationship between THz generation in a two color filament and induced N2 fluorescence through population trapping during molecular alignment and revival in air. This further supports the new technique of remote THz detection in air through the sensitive measurement of N2 fluorescence.
TL;DR: In this paper, a pulsed current was introduced into the traditional coaxial laser cladding process to decrease the porosity of the cladding layer and increase the microhardness of an equiaxed zone in the cross section of a claddings.
Abstract: A pulsed current is introduced into the traditional coaxial laser cladding process to decrease the porosity of the cladding layer. The magneto contraction force caused by pulsed current exerted on the molten pool squeezes the gas out and compensates the shrinkage during molten pool solidification. As a result the porosity of the cladding layer is decreased to an extremely low degree. Simultaneously, the grain of the cladding layer is finer with the added supercooling degree with pulsed current. The microhardness of an equiaxed zone in the cross section of a cladding layer also increases.
TL;DR: In this article, three-dimensional-ordered Yb/Er co-doped Bi2Ti2O7 inverse opal, powder, and disordered reference samples are prepared and their upconversion (UC) emission properties and mechanisms are investigated.
Abstract: Three-dimensional-ordered Yb/Er co-doped Bi2Ti2O7 inverse opal, powder, and disordered reference samples are prepared and their upconversion (UC) emission properties and mechanisms are investigated. Significant suppression of UC emission is detected when the photonic band-gaps overlap with Er3+ UC green emission bands. Interestingly, green and red UC emissions follow a two-photon process in the powder sample but a three-photon one in the inverse opal.
TL;DR: A piece-wise transition detection algorithm that performs displacement measurements for self-mixing sensors is developed that can correctly detect self- Mixing fringes at a low signal-to-noise ratio in the presence of disturbances without filtering.
Abstract: A piece-wise transition detection algorithm that performs displacement measurements for self-mixing sensors is developed. The algorithm can correctly detect self-mixing fringes at a low signal-to-noise ratio in the presence of disturbances without filtering. Displacement reconstructions by the phase unwrapping method based on this algorithm are experimentally validated, with laser subject to the moderate feedback regime.
TL;DR: In this paper, a method for the noninvasive measurement of blood glucose levels, which are determined by the ultrasound-modulated optical technique, is presented. The method is based on the optical scattering coefficient.
Abstract: We present a method for the noninvasive measurement of blood glucose levels, which are determined by the ultrasound-modulated optical technique. The method is based on the optical scattering coefficient. A sensitivity analysis of the ultrasound-modulated light signals in a scattering medium is conducted. Glucose concentrations in intralipid and hemoglobin solutions are measured using the modulation depth of ultrasound-modulated scattered light. The effects of incident light intensity and sample temperature on the ultrasound-modulated signals are also estimated. Preliminary experimental results suggest that the proposed method is a promising technique for noninvasive blood glucose measurement.