查看更多>>摘要：The advantage of polarization makes it feasible to gain the contrast of an object and to extend the information of the scene as compared with conventional intensity images, since the information added by polarimetric images is complementary to the intensity ones. The use of polarization is of considerable value for nondestructive detection, biomedical diagnosis, etc. Here, a snapshot full-Stokes imaging polarimeter based on compressive sensing was presented. By combining a wave plate and a Wollaston prism, a full-Stokes polarization compressed measurement with a compression ratio of 50% was carried out, and the spatial resolution of the division-of-aperture polarimeter was improved effectively. Besides, the measurement matrix is optimized to improve the quality of image reconstruction. Computer simulation results are reported, followed by experimental demonstrations.
查看更多>>摘要：We report on the complete temporal characterization of femtosecond laser pulses from second-order in-terferometric autocorrelation and laser spectrum measurements. The method exploits a newly developed autocorrelator based on a two photon-absorption signal produced directly within a camera sensor so as to provide a single-shot interferometric autocorrelation of great reliability and robustness. Interferometric autocorrelation trace and laser spectrum are exploited for a spectral phase retrieval via an evolutionary algorithm. The quality of the reconstruction for highly modulated spectral phases imprinted by a pulse shaper confirms the reliability of the method. The autocorrelator is compact, robust and easy to use. Possible improvements are discussed.
查看更多>>摘要：We report on the first demonstration of a living biological probe that is utilized to measure microscale vibration information. The microsphere-based living biological probes were precisely manipulated through optical fiber tweezers technology, enabling to transmission and focus of the emitted light on the surface of the vibrating microstructure and then combining it with laser self-mixing interference to obtain the microscale vibration information. Experiments show that the living probes can successfully detect the microscale vibration information of microstructure, and the relationship between the interference fringe number of the self-mixing signal and the peak-to-peak amplitude of the vibration of the microstructure was analyzed. The presented living probes may expand the application of optical fiber probes for detecting microscale vibration information in the biological field.
查看更多>>摘要：On-chip stimulated Brillouin scattering (SBS) can be implemented with arsenic trisulfide (As2S3) waveguides and benefits various applications of microwave photonic, signal processing and sensing. While stiff top-claddings of silica on the waveguides can help to enhance the opto-acoustic interaction in SBS, the soft cladding can facilitate the realization of narrow linewidth Brillouin lasers. Herein, we systematically study the on-chip SBS characteristics of the ridge As2S3B waveguides with soft claddings of Benzocyclobutene (BCB). Specifically, an optical propagation loss lower than 0.2 dB/cm and a Brillouin gain coefficient of approximately 300 m(-1) W-1 at the Brillouin frequency of 7.70 GHz have been demonstrated. In particular, the linewidth of the Brillouin gain spectrum is broadened to be about 60 MHz. The influence of waveguide width on the SBS properties is systematically studied and the mostly-concerned linewidth broadening effect with respect to different waveguide dimensions has been found to be negligible. As an application of the fabricated BCBcladded As2S3 waveguide, we have demonstrated the microwave bandpass filter with a suppression ratio of up to 23 dB. The As2S3 waveguides with BCB-claddings may provide an effective and economic platform for on-chip SBS applications, such as integrated notch filter, Brillouin amplifiers, Brillouin lasers.
查看更多>>摘要：A dual-wavelength bandpass Faraday anomalous dispersion optical filter (DW-FADOF) operating at both the D1 and D2 lines of rubidium is experimentally demonstrated. The effects of certain system parameters, such as the incident laser power, magnetic field strength, and atomic density, on the performance of the filter are experimentally and theoretically investigated. Through elaborate simulation, an appropriate set of system parameters is selected, and the DW-FADOF achieves peak transmittance of 37.4% with a figure of merit (FOM) of 0.10 GHz(-1) in the D1 line and 77.9% with a FOM of 0.33 GHz(-1) in the D2 line, simultaneously. This FADOF provides transmission bands covering both two typical atomic transitions, and it can be used as a dual signal carrier. Due to the integration and minimization of loss, the results confirm the significant application potential of this filter in wavelength division multiplex communication and weak signal extraction.
查看更多>>摘要：In this paper, the orthogonal polarization clamping behavior of a random Brillouin fiber laser (RBFL) which employs polarization maintaining fiber (PMF) is observed and investigated theoretically and experimentally. Owing to the axial polarization attraction effect of stimulated Brillouin scattering (SBS) in PMFs, the state of polarization (SOP) of lasing light from the PMF-RBFL will be definitely clamped to one of the two principal axes of PMFs under certain pump power and polarization conditions. Furthermore, based on the polarization clamping manipulation, an orthogonal polarization interleaving multi-wavelength (OPIMW) RBFL is demonstrated.
查看更多>>摘要：A phase compensational elliptical Fresnel zone plate (PCEFZP) is proposed to control the light field in this paper. It compensates the optical path difference from PCEFZP to the major focal point to control the beam focus on the specified position. Besides, the PCEFZP and the spiral phase plate are combined to produce vortex beams. By changing different phase plates, three types of elliptical vortex beams (EVB) are generated. Simulation and experimental results show that there are obvious differences among the three beam fields: EVB of type B has the longest focal depth among them, in addition, when the topological charge increases, beam fields of type A and B can maintain a perfect elliptical shape, while the central null of the type C EVB field intensity splits into a different number of nulls and the number of nulls is equal to topological charge. These parameter-tunable vortex beams can find applications in different fields, such as particle manipulation and optical communication.
查看更多>>摘要：A signal processing method based on the kurtosis parameter (k-parameter) statistical analysis is demonstrated for vibration sensing in a phase-sensitive optical time domain reflectometry with conventional configuration. The technique allows for denoising and enhancing the position accuracy of the sensing system. The k parameters of the backscattering amplitude along the sensing fiber are calculated to recover the real vibration signal from Gaussian noises. The modeled results show that the k-parameter algorithm efficiently remove Gaussian noise from the vibration signal based on the probability density distribution. In experiments, vibration measurements in a similar to 12 km long sensing fiber are carried out, and the vibration point is placed at the far-end (11.9 km) of the sensing fiber. Finally, the location signal-to-noise ratio of 5.61 dB and the spatial resolution of 5.1 m with pulse width of 200 ns is obtained by the k-parameter statistical analysis.
查看更多>>摘要：In a strong nuclear radiation environment, the life of a traditional zoom lens is extremely short. To improve the life of the zoom lens, a novel method to design the zoom optical system is proposed, in which the front fixed group is all made of Silica lens with stronger irradiation performance. Firstly, the radiation-resistant performance of the glass lens is tested, and the transmittance of the optical system is analyzed. Then, a specific zoom optical system was proposed for the problem of difficult chromatic aberration correction in the front fixed group, and a calculation method of the initial structure parameters is analyzed theoretically. Finally, a 6x radiation-resistant zoom optical system is designed by using only two specific radiation-resistant glass materials. The imaging experiment demonstrates the better imaging performance of the radiation-resistant zoom system, which verifies the feasibility of the design method proposed in this paper.
查看更多>>摘要：The regenerative amplifier is an important component of the high-power laser facility. A high-energy broadband Nd: glass regenerative amplifier with an energy of 34.1 mJ and a bandwidth of 4.3 nm was demonstrated using an intra-cavity specially coated birefringent filter (CBRF). This letter proposes a design scheme for a CBRF that can control the flat-top area of gain spectrum of the regenerative amplifier, which has been studied theoretically and experimentally. The transmittance of the specially coated BRF was tested in this experiment. The amplifier output spectrum had a flexible control ability and long-term stability. It can be applied to support high-energy broadband amplification in inertial confinement fusion (ICF) facilities, and can also be extended to other broadband amplification system to support high-energy picosecond petawatt laser facilities.
NSTL
Elsevier