Single-Frequency Narrow Linewidth 2 Micron Fiber Laser

A compact single frequency, single-mode 2 .mu.m fiber laser with narrow linewidth, <100 kHz and preferably <100 kHz, is formed with a low phonon energy glass doped with triply ionized rare-earth thulium and/or holmium oxide and fiber gratings formed in sections of passive silica fiber and fused thereto. Formation of the gratings in passive silica fiber both facilitates splicing to other optical components and reduces noise thus improving linewidth. An increased doping concentration of 0.5 to 15 wt. % for thulium, holmium or mixtures thereof produces adequate gain, hence output power levels for fiber lengths less than 5 cm and preferably less than 3 cm to enable single-frequency operation

2-.mu.m fiber amplified spontaneous emission (ASE) source

A 2-.mu.m fiber Amplified Spontaneous Emission (ASE) source provides a wide emission bandwidth and improved spectral stability/purity for a given output power. The fiber ASE source is formed from a heavy metal oxide multicomponent glass selected from germanate, tellurite and bismuth oxides and doped with high concentrations, 0.5-15 wt. %, thulium oxides (Tm.sub.2O.sub.3) or 0.1-5 wt% holmium oxides (Ho.sub.2O.sub.3) or mixtures thereof. The high concentration of thulium dopants provide highly efficient pump absorption and high quantum efficiency. Co-doping of Tm and Ho can broaden the ASE spectrum

Novel, rosin‐based, hydrophobically modified cationic polyacrylamide for kaolin suspension flocculation

A novel, hydrophobically modified cationic polyacrylamide (HMPAM) was synthesized via the copolymerization of acrylamide, diallyl dimethyl ammonium chloride (DMDAAC), and diallylmethyl dehydroabietic acid propyl ester ammonium bromide. Optimum conditions for preparing HMPAM were such that the amount of initiator was 0.075 wt % of the total monomer mass, the monomer concentration was 20 wt %, and the amount of DMDAAC was 18 mol % of the total monomer molar mass. HMPAM was characterized with an UV–visible spectrometer, 1H‐NMR, Ubbelohde viscometer, rotational viscometer, and rotational rheometer. HMPAM solutions exhibited strong hydrophobic associations, and the critical association concentration of the HMPAM aqueous solution was about 0.7 wt %; the HMPAM solutions also showed salt thickening and shear resistance. The surface morphologies of the freeze‐dried HMPAM samples (1 wt %) were also observed via scanning electron microscopy. Compared with unmodified cationic polyacrylamide, Synthesis of HMPAM‐0.5 exhibited a stronger flocculation capacity, and the optimal transmittance of the supernatants was above 95%. HMPAM‐0.5 showed significant flocculation performances for 3–4 and 3–5 wt % kaolin suspensions at 40 and 50 mg/L, respectively. Moreover, the flocculation performance was enhanced with the addition of NaCl and CaCl2. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46637.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144283/1/app46637.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144283/2/app46637_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144283/3/app46637-sup-0001-suppinfo1.pd

Origins of 1/f noise in nanostructure inclusion polymorphous silicon films

In this article, we report that the origins of 1/f noise in pm-Si:H film resistors are inhomogeneity and defective structure. The results obtained are consistent with Hooge's formula, where the noise parameter, αH, is independent of doping ratio. The 1/f noise power spectral density and noise parameter αH are proportional to the squared value of temperature coefficient of resistance (TCR). The resistivity and TCR of pm-Si:H film resistor were obtained through linear current-voltage measurement. The 1/f noise, measured by a custom-built noise spectroscopy system, shows that the power spectral density is a function of both doping ratio and temperature

Optical Properties of Tm(3+) Ions in Alkali Germanate Glass

Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69

Martian column CO2 and pressure measurement with spaceborne differential absorption lidar at 1.96&thinsp;µm

By utilizing progress in millijoule-level pulsed fiber lasers operating in the 1.96 µm spectral range, we introduce a concept utilizing a spaceborne differential absorption barometric lidar designed to operate within the 1.96 µm CO2 absorption band for remote sensing of Martian atmospheric properties. Our focus is on the online wavelength situated in the trough region of two absorption lines, selected due to its insensitivity to laser frequency variations, thus mitigating the necessity for stringent laser frequency stability. Our investigation revolves around a compact lidar configuration, featuring reduced telescope dimensions and lower laser pulse energies. These adjustments are geared towards minimizing costs for potential forthcoming Mars missions. The core measurement objectives encompass the determination of column CO2 absorption optical depth, columnar CO2 abundance, surface atmospheric pressure, and vertical distributions of dust and cloud layers. Through the amalgamation of surface pressure data with atmospheric temperature insights garnered from sounders and utilizing the barometric formula, the prospect of deducing atmospheric pressure profiles becomes feasible. Simulation studies validate the viability of our approach. Notably, the precision of Martian surface pressure measurements is projected to surpass 1 Pa when the aerial dust optical depth is projected to be under 0.7, a typical airborne dust scenario on Mars, considering a horizontal averaging span of 10 km.</p

Near-Infrared Optical Absorption Enhanced in Black Silicon via Ag Nanoparticle-Induced Localized Surface Plasmon

Due to the localized surface plasmon (LSP) effect induced by Ag nanoparticles inside black silicon, the optical absorption of black silicon is enhanced dramatically in near-infrared range (1,100 to 2,500 nm). The black silicon with Ag nanoparticles shows much higher absorption than black silicon fabricated by chemical etching or reactive ion etching over ultraviolet to near-infrared (UV-VIS-NIR, 250 to 2,500 nm). The maximum absorption even increased up to 93.6% in the NIR range (820 to 2,500 nm). The high absorption in NIR range makes LSP-enhanced black silicon a potential material used for NIR-sensitive optoelectronic device. PACS 78.67.Bf; 78.30.Fs; 78.40.-q; 42.70.G

Nanoscale Footprints of Self-Running Gallium Droplets on GaAs Surface

In this work, the nanoscale footprints of self-driven liquid gallium droplet movement on a GaAs (001) surface will be presented and analyzed. The nanoscale footprints of a primary droplet trail and ordered secondary droplets along primary droplet trails are observed on the GaAs surface. A well ordered nanoterrace from the trail is left behind by a running droplet. In addition, collision events between two running droplets are investigated. The exposed fresh surface after a collision demonstrates a superior evaporation property. Based on the observation of droplet evolution at different stages as well as nanoscale footprints, a schematic diagram of droplet evolution is outlined in an attempt to understand the phenomenon of stick-slip droplet motion on the GaAs surface. The present study adds another piece of work to obtain the physical picture of a stick-slip self-driven mechanism in nanoscale, bridging nano and micro systems