Transmission-reflection decoupling of non-Hermitian photonic doping epsilon-near-zero media

We present a novel method to achieve the decoupling between the transmission and reflection waves of non-Hermitian doped epsilon-near-zero(ENZ)media by inserting a dielectric slit into the structure.Our method also allows for independent control over the amplitude and the phase of both the transmission and reflection waves through few dopants,enabling us to achieve various optical effects,such as perfect absorption,high-gain reflection without transmission,reflectionless high-gain transmission and reflectionless total transmission with different phases.By manipulating the permittivity of dopants with extremely low loss or gain,we can realize these effects in the same configuration.We also extend this principle to multi-port doped ENZ structures and design a highly reconfigurable and reflectionless signal distributor and generator that can split,amplify,decay and phase-shift the input signal in any desired way.Our method overcomes limitations of optical manipulation in doped ENZ caused by the interdependent nature of the transmission and reflection,and has potential applications in novel photonic devices.

Scaling of Yb-doped photonic crystal fiber to 200 μm core diameter for high beam quality laser output

The rare earth-doped active fibers not only have ten thousands of square-micron core-area but also deliver a laser with near-diffraction-limited beam quality. However, they have been studied little. In this paper, we design a 200-μm-corediameter Yb^3＋-doped photonic crystal fiber with a large pitch in the air-hole cladding region. Simulations demonstrate that only fundamental mode（FM） with a mode field area（MFA） of ～ 28000 μm^2 can be amplified and propagated at the gain saturation, and the beam quality M^2 is about 1.5. It is predicted that almost 105 m J single-pulse energy is available from such a 1.5-meter-length fiber.

Seven-core photonic liquid crystal fibers for simultaneous mode shaping and temperature sensing

Through doping liquid crystals into the core region, we propose a kind of seven-core photonic crystal fiber（PCF）which can achieve mode shaping and temperature sensing simultaneously in the communication window of1.1–1.7 μm. To the best of our knowledge, this is the first time that the function of seven-core PCFs as temperature sensors is investigated. By using the full vectorial finite element method, the characteristics of the fiber with the temperature, such as the effective mode area, the waveguide dispersion, and the confinement loss, are analyzed. This kind of PCF can be competitive in providing temperature sensing in multi-core PCF lasers.

255 W picosecond MOPA laser based on self-made Yb-doped very-large-mode-area photonic crystal fiber

We report on the amplification of high-average-power and high-efficiency picosecond pulses in a self-made verylarge-mode-area Yb-doped photonic crystal fiber（PCF）. The PCF with a core diameter of 105 μm and a core numerical aperture of 0.05 is prepared by the sol-gel method combined with the powder sintering technique. The fiber amplification system produces the highest average power of 255 W at a 10 MHz repetition rate with a 21 ps pulse duration corresponding to a peak power of 1.2 MW. This result exemplifies the high-average-power and high-peak-power potential of this specifically designed fiber.

Spectral evolution of NIR luminescence in a Yb^(3+)-doped photonic crystal fiber prepared by non-chemical vapor deposition

Silica-based yb3＋-doped glass is prepared by non-chemical vapor deposition. The drawn photonic crystal fiber （PCF） has a strong absorption at 976 nm and emission wavelength of approximately 1 037 nm. The intensity and spectral lineshape of the near infrared （NIR） luminescence of the Yb3＋-doped PCF are recorded and discussed in terms of excitation power, excitation wavelength, fiber length, and Yba＋ ion concentration. The emission intensifies as the excitation power and Yb3＋ ion concentration increase. The intensity of the shorter wavelength side of the luminescence spectrum decreases as the length of the PCF increases.

Low-loss high-extinction-ratio single-drive push-pull silicon Michelson interferometric modulator

We demonstrate a high-speed silicon carrier-depletion Michelson interferometric（MI）modulator with a low onchip insertion loss of 3 dB.The modulator features a compact size of 〈1 mm2 and a static high extinction ratio of 〉30 dB.The Vπ·Lπ of the MI modulator is 0.95–1.26 V·cm under a reverse bias of -1 to-8 V,indicating a high modulation efficiency.Experimental results show that a 4-level pulse amplitude modulation up to 20 Gbaud is achieved with a bit error rate of 6×10-3,and a 30 Gb/s binary phase-shift-keying modulation is realized with an error vector magnitude of 25.8%.

Switchable optical nonlinear properties of W_(18)O_(49) nanowires by Ag nanoparticles supported

During the past decades,nonlinear optical（NLO）materials have attracted special interest because of their potential applications in photonic devices,such as optical switching,frequency conversion and electro-optic modulators.Among the finding ways to obtain excellent NLO materials with both large NLO response and short response time,