Simple Yb Research Articles

Large dispersion-managed broadband high-energy fiber femtosecond laser system with sub 300 fs pulses and high beam quality output

We experimentally demonstrate a high-energy sub 300 fs polarization maintaining fiber chirped pulse amplification (CPA) system. The preamplifier is a monolithic fiberized system that uses two cascaded temperature-assisted dispersion-tuning broadband chirped fiber Bragg gratings (CFBGs) with a reflected bandwidth of 20 nm as stretchers. To make full use of the stretcher to lower the system’s nonlinearity accumulation, a homemade mode locked fiber laser with a spectral width of 14.8 nm (full width at half maximum) is selected as the seeder to offer a stretched pulse width of 1.69 ns. The main amplifier is based on a one-stage simple Yb:YAG single crystal fiber amplifier with an amplified output power of 40.6 W at a repetition rate of 200 kHz, and the beam quality is conserved in a single mode beam profile with beam quality of 1.246 and 1.142 in the horizontal direction and vertical direction, respectively. During amplification, the spectral gain narrowing effect is observed. To achieve the high-speed switch of the laser, an acoustical optical modulator (AOM) is inserted before the compressor to achieve high-speed turn-on/off control. The compressor is based on a diffraction grating pair with a groove density of 1600 line/mm to offer a dispersion match with the stretcher of the CFBGs. With the CFBG’s fine-tuned capacity of second-order dispersion and higher-order dispersion, the compressed average power of 29.6 W and pulse duration of 278 fs, corresponding to a pulse energy of 148 µJ and a peak power of 532 MW with ignoring the wings of the pulse, is obtained. The beam quality is well conserved after compression, and the beam quality is 1.250 and 1.196 in the horizontal direction and vertical direction, respectively. A power fluctuation of 0.1% (root mean square) and a beam pointing drift of 8.47 µrad/°C over 8 h are realized. This high peak power and high beam quality femtosecond laser is promising in science and industrial applications.

23.9 W, 985 fs Chirped Pulse Amplification System Based on Yb:YAG Rod Amplifier

A stable and simple Yb:YAG rod amplifier based on chirped pulse amplification in a water cooling system has been demonstrated. The output power of 38 W at a 250 kHz repetition rate with a spectrum width of 4 nm centered at 1030 nm, which support Fourier-transform limited pulse duration of 389 fs has been generated. The compressed power of 23.9 W with pulse duration of 985 fs has been obtained with a chirped volume Bragg grating compressor. The power stability is measured to be 1.414% when the output power is 35 W. The system is worthwhile to popularize for its good performance and inexpensive cost.

Yb fiber based laser source for tunable, narrow bandwidth picosecond pulses in the visible.

We present a simple Yb fiber pumped source for narrow bandwidth picosecond pulses which are tunable in the visible spectral region. This emission is obtained by frequency doubling of a soliton generated in a photonic crystal fiber. The system is attractive for different types of nonlinear optical microscopy and can easily be adapted to meet different experimental prerequisites. As an example, we demonstrate coherent anti-Stokes Raman scattering microscopy using the laser source described.

Achieving low-VT Ni-FUSI CMOS via lanthanide incorporation in the gate stack

This work reports that introducing lanthanide in the gate dielectric or in the gate electrode results, in both cases, in large effective work function (eWF) modulation towards n-type band-edge for Ni-FUSI devices. This is done by: (a) deposition of a Dy2O3 capping layer on the host dielectric (SiON or HfSiON), or (b) simple Yb implantation of nMOS poly gates prior to FUSI. We show that: (1) both cases result in dielectric modification with gate leakage (JG) reduction; (2) adding a cap has no significant impact on Tinv(<1Å), while up to ∼5 and 2Å reduction occurs for SiON and HfSiON Yb-implanted devices, respectively, (3) the largest JG reduction (150×) is obtained for capped SiON devices due to dielectric intermixing and formation of a new high-k dielectric (DySiON), comparable to HfSiON in JG and mobility but with 500mV smaller VT; (4) on the other hand, being less invasive to the host dielectric, the optimized Yb I/I option gives 18% improved mobility compared to capped SiON devices; (5) excellent process control and reliability behavior (VT instability by a.c. pulsed IV, PBTI and TDDB) is reported for both eWF tuning methods. They allow ΔeWF(n−p) values up to ∼800meV when combined with Ni–silicide FUSI phase engineering, promising for low-VT CMOS.

Mode-locked Yb:KGW laser longitudinally pumped by polarization-coupled diode bars

Mode-locked operation of a simple Yb:KGW (potassium gadolinium tungstate) oscillator is described, providing 10 W at 1039 nm with a 290 fs pulse width. A polarization-coupled scheme is used for efficient longitudinal pumping by a pair of reshaped laser diode bars. With changes in cavity dispersion, the pulse width is adjustable from 134 to 433 fs, in a high-quality circular mode. A saturable absorber mirror provides self-starting operation, and the cavity is stabilized by the Kerr-lens effect.

The aqueous geochemistry of REE.: Part 8: Solubility of ytterbium oxalate and the stability of Yb(III)–oxalate complexes in water at 25°C to 80°C

The solubility of ytterbium oxalate (Yb 2Ox 3· xH 2O) in aqueous solution was measured as a function of temperature (40°C, 60°C and 80°C), ionic strength (0.05, 0.1 and 0.2 m NaCl), and free oxalate concentration (10 −7 to 10 −2 molal). At high oxalate and/or NaCl concentration, the simple Yb–oxalate salt transforms into a double salt with the stoichiometry NaYb(Ox) 2· yH 2O. Our solubility data were used to obtain smoothed equilibrium constants ( I=0, P=SVP) for the solubility products of both solid phases, and for the stepwise and cumulative association complexes of the aqueous Yb(III)–oxalate complexes, between 25°C and 100°C. Whereas the solubility of the simple Yb–oxalate salt changes little in this temperature range, the Na–Yb oxalate salt becomes less stable and significantly more soluble with an increase in temperature. The ytterbium oxalate complexes are strong, and may predominate over inorganic Yb(III) complexes (e.g., carbonate, chloride, sulfate, and phosphate) at geologically realistic ligand concentrations. Our results are relevant to researchers interested in the transport of ytterbium and other rare earth elements (REE) in near-surface waters and sedimentary basin fluids, and may also have engineering applications with regards to the precipitation of oxalate salts as a means of removing actinides and radioactive REE from aqueous nuclear wastes.