查看更多>>摘要：We present a high power, long pulse width, high pulse repetition rate (PRR), single-frequency 1064 nm master oscillator power amplifier (MOPA). The MOPA system consists of a single-frequency 1064 nm seed laser, ytterbium-doped fiber preamplifier, and two stages of rod Nd: YVO4 amplifier. The MOPA delivers a maximum average output power up to 122.3 W with a spectral linewidth of 24.15 fm, operating at a PRR of 50 kHz with a pulse width of 10 mu s. The average beam quality factor is measured to be M-2 = 1.375, exhibiting a Gaussian TEM00 mode. The output power fluctuation of the MOPA system is less than 0.96% over one hour. Such a high power, single-frequency laser source with long pulse width and high PRR is expected to be utilized for long-distance, high-precision laser imaging.
查看更多>>摘要：A perfect bidirectional dynamic tunable absorber working in the near-infrared based on an asymmetric FabryPerot resonance in a thin film dielectric-metal multilayer structure is proposed. Perfect narrowband absorption occurs at the wavelength of 1023 nm (full width at half-maximum, 13 nm) when light is normally incident on the surface covered with a silver film with a saturation voltage applied to polymer-dispersed liquid crystal (PDLC). Illumination from the opposite direction results in ultra-broadband absorption (98.91% absorption averaged over 764-2476 nm). The narrowband absorption can be dynamically tuned in the 1023-1056 nm range via PDLC modulation. Furthermore, the excellent angular sensitivity of the narrowband absorption, as well as the good angular and polarization tolerances of the broadband absorption are demonstrated.
查看更多>>摘要：A novel band-stop metal-insulator-metal plasmonic waveguide filter with high efficient filtering and high sensitivity is proposed and investigated theoretically. The relationship among the wavelength of the incident wave, the refractive index of the measured material and the transmittance of the incident wave is simulated by finite-difference time-domain (FDTD) and coupled mode theory (CMT) method. The filters which consist of a straight waveguide and two square resonators embedded with silver nanorods have minimum transmittance of 0.04%, 2.2%, 14.9% and 9.0% at the dips. The maximum sensitivity could reach 2860 nm/RIU. The sensitivity of the filter to detect plasma, hemoglobin, glucose and Sylgard184 reaches 2854 nm/RIU, 2852 nm/RIU, 2850 nm/RIU, 2851 nm/RIU, respectively. This waveguide filter may provide a new reference for highly integrated optical circuits and refractive index sensor.
查看更多>>摘要：A novel digital-to-analog conversion (DAC) scheme based on the photonic time-stretch (PTS) technology is proposed and experimentally demonstrated. In this approach, the broadband chirped optical pulses are properly adjusted by the spectrum-shaper to produce the intensity weighted wavelength bands, which are employed to carry the serial input digital signals by the intensity modulation. The modulated signals are further stretched by the same time factor and partly overlapped with each other to realize the incoherent weighted intensity summation. Compared with the existing photonic DAC schemes, the generation of optical carriers and the weighted intensity summation in proposed approach are achieved by using only a single fiber, accordingly the system configuration is significantly simplified and much easier to be integrated. The proof-of-concept experiment for a 3-bit DAC system based on PTS is successfully carried out. In addition, the system performance in terms of INL (integral nonlinearity) and DNL (differential nonlinearity) is also discussed.
查看更多>>摘要：In this paper, a temperature-control optical switch is designed based on a conjoined-tubular anti-resonance optical fiber (CTF). The CTF adopts eight pairs of conjoined tubes and four vertical-layout holes were coated with Au to increase the fiber confinement loss (Loss). Toluene was used as transmission medium to injected into the CTF core. The proposed switch produces a Loss difference over 100 dB and ER more than 30 dB. Influence of switch material refractive index and structural parameters on optical switch performance was further discussed. The proposed optical fiber switch has the features of simple structure, small size, broad working wavebands and adjustable operation temperature, which promises broad application prospects in industry, chemistry, biology and other fields.
查看更多>>摘要：Dual-wavelength digital holographic microscopy extends the unambiguous measurement range in quantitative phase imaging. However, it suffers from increased noise, which reduces phase sensitivity, especially when a larger beat wavelength is synthesized. We present a simple, robust, and fast dual-wavelength phase unwrapping method, without increased phase noise, by segmenting a single wavelength phase map into multiple regions along its phase discontinuities and calculating the fringe order of each region. The method works properly with a large beat wavelength, while reducing phase noise to the level of a single wavelength. Simulations were performed for imaging a smooth profile sample and a multi-heights step. We also demonstrated its practical implementation in quantitative imaging of microstructures where a beat wavelength was up to 20.475 mu m.
查看更多>>摘要：We report on the power-scaling continuous-wave (cw) Dy3+, Tb3+:LuLiF4 yellow laser, which comprises a single-emitter blue laser diode (LD) that functions as a pump source. The maximum output power of the laser is evaluated to be 220 mW at 574 nm. The passively Q-switched yellow laser is generated by using Cr4+:Y3Al5O12 (Cr:YAG) as the saturable absorber. The shortest pulse width (full width at half maximum) is less than 582 ns with a repetition rate of 5.8 kHz. Meanwhile, the pulse energy and peak power are similar to 4.5 mu.J and similar to 7.7 W, respectively. This work reveals that Dy3+, Tb3+:LuLiF4 crystal is a potential laser gain material that can be used to develop compact and efficient yellow lasers, which can not only be employed in cw lasers but also in passively Q-switched pulse lasers.
查看更多>>摘要：This study proposes an all-fiber-optic design with an optimal fringe in non-polarization-maintaining (non-PM) depolarized Sagnac-based interferometers (SIs) for laser ultrasound detection. We theoretically demonstrate that the rotation-time (RT) symmetry property of the depolarized SIs is a fundamental principle of the stable phase bias, and experimentally verify that our design simultaneously provides a stable quadrature phase bias and the highest visibility. As the system stabilizes at the "zero amplitude"point, the phase error and signal fading challenges caused by the polarization nonreciprocal effect in the conventional non-PM setup are not serious anymore. In the experiment, a visibility of 48.4% (50% is the highest in theory) with the stable quadrature phase bias is obtained. This method extends SIs to non-PM applications with a more straightforward adjustment process compared to the method used in previous work using polarized light and is necessary to meet the demand of large-scale applications. The SI system developed here provides a cost-effective, high-sensitive, and easy-to-use scheme for non-contact laser ultrasound detection.
查看更多>>摘要：We investigate the tailoring effect of the point vortices on the foci of the circular Airy vortex beam (CAVB). Two optical vortices (OVs) with same or opposite topological charges (TCs) are symmetrically loaded on the beam. It is found that the loading distance between these two OVs (denoted as d(v)) can significantly tailor the auto-focusing behaviour of the beam. For two OVs with same TCs, as d(v )increases from 0 to infinite, the intensity pattern at the focal plane changes from a ring to a bright spot. For opposite OVs, when d(v) is near 0 or very large, there is a bright foci. But within a certain range, two foci are generated at the focal plane. Good agreements have been achieved between simulations and experiments. We qualitatively explain the tailoring phenomena from the perspective of the inward energy flow of the main ring of CAVB and the interaction between two OVs. The tailoring effect of d(v) of the two OVs on the focal pattern may have potential applications in micromanipulation, communication and other fields.
查看更多>>摘要：This paper introduces an optical information encryption method based on partially-update iteration system with azimuth multiplexing. Multiple high-definition pictures are stored in multiple QR codes as amplitude constraints, and then encrypted in Fresnel domain by azimuth multiplexing. Due to the proposal of the enhancement system with partial update of the phase mask, the number of pictures can be encrypted increases. The security of the system is guaranteed by azimuth multiplexing, and the multiplexing capacity is jointly guaranteed by phase partial update system and QR code. The decoded QR code can extract the encrypted information without much quality loss. Simulation results show that the scheme has a large-capacity information storage, high security, robustness and practicability.
NSTL
Elsevier