Efficient single-frequency Tm:YAG crystal-derived silica fiber laser at 1.7 µm.

A single-frequency distributed Bragg reflector (DBR) fiber laser operating at 1720 nm has been demonstrated for the first time using a Tm:YAG crystal-derived silica fiber (TCDSF), to the best of our knowledge. A single-frequency laser with an over 220 mW output power was achieved from a 1.5-cm-long TCDSF when being in-band pumped by a homemade 1610 nm fiber laser.

High-efficiency single-frequency DBR fiber laser at 1091 nm utilizing a Yb:YAG crystal-derived silica fiber.

A single-frequency distributed Bragg Reflector (DBR) fiber laser operating at 1091 nm was demonstrated by using a Yb:YAG crystal-derived silica fiber (YDSF). The YDSF was prepared via the molten core (MC) method, with a YbO doping concentration of 5.60 wt.

Widely tunable NCPM-KTA OPO based on non-collinear phase-matching in a four-mirror ring cavity.

Based on non-collinear phase-matching (PM), a new method for widely tunable wavelength was proposed and demonstrated in a four-mirror ring cavity of non-critical phase-matching (NCPM) KTiOAsO (KTA) optical parametric oscillator (OPO). Wavelength tuning range of 141 nm from 1535.56 nm to 1676.

Single-frequency fiber laser of 315 mW at 1940 nm based on a Tm : YAG/Ho : YAG-co-derived silica fiber.

A 1940 nm single-frequency distributed Bragg reflector (DBR) fiber laser was demonstrated based on a Tm : YAG/Ho : YAG-co-derived silica fiber (THCDSF). The THCDSF, which had a core dopant concentration of 8.02 wt.

Bio-Inspired Conductive Hydrogels with High Toughness and Ultra-Stability as Wearable Human-Machine Interfaces for all Climates.

Drawing inspiration from Salicornia, a plant with the remarkable ability to thrive in harsh environments, a conductive hydrogel with high toughness and ultra-stability is reported. Specifically, the strategy of pre-cross-linking followed by secondary soaking in saturated salt solutions is introduced to prepare the PAAM-alginate conductive hydrogel with dual cross-linked dual network structure. It allows the alginate network to achieve complete cross-linking, fully leveraging the structural advantages of the PAAM-alginate conductive hydrogel.

Consecutive 1015-1105-nm wavelength tunable "figure-of-9" mode-locked Yb:fiber oscillator.

A widely wavelength tunable mode-locked Yb-doped fiber oscillator based on nonlinear amplifier loop mirror (NALM) is reported, in which only a piece of short (∼0.5 m) single-mode polarization-maintaining (PM) Yb-doped fiber is employed, instead of the frequently used long (a few meters) double cladding (DC) fiber in previous papers. Experimentally, the center wavelength can be consecutively tuned from 1015 to 1105 nm by tilting the silver mirror, corresponding to a tuning range of 90 nm.

Modeling for extracavity-pumped terahertz parametric oscillators.

This paper presents a modeling method for extracavity-pumped terahertz parametric oscillators (TPO) based on stimulated polariton scattering, in which the pumping beam is from a different laser, and the Stokes beam oscillates in its cavity. After suitable approximations and assumptions, the average THz wave amplitude in the nonlinear crystal is expressed as a function of the fundamental and Stokes wave amplitudes. Then the rate equation for the Stokes wave is obtained based on the Stokes wave increment within a cavity roundtrip timescale.

Comparison of a high-power 3.75 µm BaGaSe OPO based on a plane-parallel resonator and an unstable resonator with a Gaussian reflectivity mirror.

Using a homemade Nd:YAG laser with a pulse repetition frequency of 300 Hz as a pump source, we demonstrated a tunable (BGSe) optical parametric oscillator (OPO). Wavelength-tuning ranges of 1.42-1.

High-efficiency 940- and 969-nm brightness-maintaining wavelength-multiplexed LD-pumped 240-W thin-rod Yb:YAG amplifier.

A high-efficiency ultrafast laser amplifier based on thin-rod Yb:YAG was demonstrated, featuring a 940- and 969-nm brightness-maintaining wavelength-multiplexed laser diode (LD)-pumping method. Two high-brightness LDs (940 nm and 969 nm) were spectrally combined into one beam spatially with a dichroic mirror, thus enabling twice pump power while maintaining high brightness. A maximum signal power of 240 W was obtained at a repetition rate of 1 MHz, with a power extraction efficiency (PEE) of ∼51%.

Wearable Sensors Adapted to Extreme Environments Based on the Robust Ionogel Electrolytes with Dual Hydrogen Networks.

Nonvolatile ionogels are promising soft electrolyte materials for flexible electronics, but it is challenging to fabricate stable electrolytes with mechanical robustness. Here, through rationally optimizing the chemical structure of polymer matrix and ionic liquids, the high-performance ionogel electrolytes with mechanical robustness and stability were fabricated. There are double hydrogen bonding networks in the as-prepared ionogel electrolytes, one of which exists between the polymer chains while the other one existing between the polymer chains and ionic liquid molecules.

High-repetition-rate, 50-µJ-level, 1064-nm, CPA laser system based on a single-stage double-pass Yb-doped rod-type fiber amplifier.

A 1064-nm femtosecond fiber chirped pulse amplification (FCPA) laser system based on a single-stage double-pass Yb-doped rod-type photonic crystal fiber (PCF) amplifier was demonstrated with a pulse repetition rate of 500 kHz, which was specially designed for expected conversion efficiency enhancement of a 10.8 eV source. With a series of Yb:fiber power amplifiers, the average output power was boosted to approximately 35 W.

Zwitterionic Hydrogel Electrolyte with Tunable Mechanical and Electrochemical Properties for a Wearable Motion and Thermal Sensor.

A high-performance zwitterionic hydrogel electrolyte was successfully fabricated, in which the polymer chains were cross-linked by multiple reversible non-covalent bonds. The mechanical and electrochemical properties of the synthesized zwitterionic hydrogel electrolyte can be facilely modulated by immersing the as-prepared zwitterionic hydrogel in saline solutions with different concentrations. The processed zwitterionic hydrogel electrolyte exhibits tunable mechanical and electrochemical properties (favorable elasticity of 3.

Stable 5-GHz fundamental repetition rate passively SESAM mode-locked Er-doped silica fiber lasers.

A stable passively mode-locked Er-doped silica fiber laser with a fundamental repetition rate of up to 5 GHz is demonstrated, which, to the best of our knowledge, is the highest repetition rate for 1.5 μm semiconductor saturable absorber mirror (SESAM) mode-locked Er-doped silica fiber (EDF) lasers. A segment of commercially available EDF with a net gain coefficient of 1 dB/cm is employed as gain medium.

Linearly polarized single-frequency fiber laser based on the Yb:YAG-crystal derived silica fiber.

A linearly polarized low-noise single-frequency fiber laser was demonstrated by using a homemade 1.2-cm-long Yb:YAG crystal derived silica fiber. A maximum output power of greater than 60 mW was obtained with a signal-to-noise ratio of ∼80 and a polarization extinction ratio of 27.

Distributed sparse signal sensing based on compressive sensing OFDR.

The maximum detectable vibration frequency of an optical frequency domain reflectometry (OFDR) system is limited by the tunable rate of the laser source. Unlike uniform sampling with the time-resolved method, the sampling frequency is randomly modulated so that the vibration signal applied on the interrogation fiber is sampled by a multi-frequency sub-Nyquist sampling method and reconstructed by the compressive sensing technique. First, we give a full treatment to prove that the proposed method has the same performance as the conventional method.

Broadening frequency response of a distributed sparse-wideband vibration sensing via a time-division multi-frequency sub-Nyquist sampling.

The maximum detectable vibration frequency response range is inversely related with the sensing fiber length in direct-detection intensity-measuring coherent optical time domain reflectometry (DI-COTDR). Unlike the conventional uniform sampling, the pulse repetition rate is modulated in a time-division manner so that a multi-frequency sub-Nyquist sampling is realized along every point of the sensing fiber. A 24-kHz vibration signal can be detected and recovered by a compressive sensing technique using sampling pulses with repetition rate lower than 5-kHz, which is ten-fold lower compared to that required in the conventional uniform sampling method.

Modeling of intracavity-pumped Q-switched terahertz parametric oscillators based on stimulated polariton scattering.

In this paper, the rate equations describing the operation of intracavity-pumped Q-switched terahertz parametric oscillators based on stimulated polariton scattering are given for the first time. The rate equations are obtained under the plane-wave approximation, the oscillating fundamental and Stokes waves are supposed to be round uniform beam spots. Considering the fact that the terahertz wave nearly traverses the pump and Stokes beams and using the coupled wave equations, the terahertz wave intensity is expressed as the function of the fundamental and Stokes intensities.

Tunable Stokes laser based on the cascaded stimulated polariton scattering and stimulated Raman scattering in RbTiOPO crystal.

Stimulated polariton scattering (SPS) and stimulated Raman scattering (SRS) in ${{\rm RbTiOPO}_4}$RbTiOPO (RTP) crystal are combined in an intracavity-pumped Stokes parametric oscillator (SPO) to extend the tunable Stokes laser spectral range. The pumping laser wavelength is 1064 nm from a diode-end-pumped acousto-optically Q-switched Nd:YAG laser. By the SPS process in the SPO, the SPS-Stokes wave can be discontinuously tuned in the range of 1075.

110 mW single-frequency Yb:YAG crystal-derived silica fiber laser at 1064 nm.

A single-frequency laser based on Yb:YAG crystal-derived silica fiber (YDSF) was demonstrated. The YDSF was fabricated by a molten-core method with a doping concentration of 4.8 wt.

All-fiber-integrated Yb:YAG-derived silica fiber laser generating 6 W output power.

A Yb:YAG-derived silica fiber was fabricated by a molten-core fabrication method, in which a Yb:YAG crystal was used as the core material and a silica tube was used as the cladding material. The fiber's transmission loss was measured to be 0.49 dB/m at 1.

Dual Path Lock-In System for Elimination of Residual Amplitude Modulation and SNR Enhancement in Photoacoustic Spectroscopy.

A technique for elimination of residual amplitude modulation (ERAM) in photoacoustic spectroscopy based on dual path lock-in was proposed and experimentally demonstrated. There are two lock-in amplifiers, one is for gas concentration demodulation and another for residual amplitude modulation (RAM) measurement by tuning the reference signal in different phases, and then a dual path lock-in technique based on subtraction is applied to RAM removal, improving the second harmonic profile significantly. In this system, the signal to noise ratio (SNR) increases about two times based on our dual path lock-in technique compared to one distributed feedback laser diode (DFB-LD).

Lamellar Liquid-Crystalline System with Tunable Iridescent Color by Ionic Surfactants.

Liquid crystals formed by the self-assembly of small molecules are very promising smart materials because of their unique properties, such as self-assembled multivalency, biocompatibility, and fast response to external stimuli. Here we report an iridescent liquid-crystal system composed of water layers, which is sandwiched by two bilayer membranes. Such membranes are composed of a self-assembled nonionic surfactant, which is called hexadecylglyceryl maleate (HGM), and only a small amount of ionic surfactants.

Single frequency MOPA based on Nd:YAG single crystal fiber and rods.

We demonstrate a single frequency 1064 nm master oscillator power amplifier (MOPA) system operating in macro-micro pulse scheme. The repetition rate for the macro pulses was 300 Hz with pulse duration of 300 μs. Micro pulses operated at 25 kHz.

Tunable KTA Stokes laser based on stimulated polariton scattering and its intracavity frequency doubling.

This paper presents the tunable Stokes laser characteristics of KTiOAsO (KTA) crystal based on stimulated polariton scattering (SPS). When the pumping laser wavelength is 1064.2 nm, the KTA Stokes wave can be discontinuously tuned from 1077.

High power broadband LiF:F(2)(-) color center laser.

A high power LiF:F(2)(-) color center laser is demonstrated with broadband emission. The excitation source is a quasi-continuous wave diode side-pumped acousto-optically Q-switched Nd:YAG laser. Under an incident 1064-nm laser power of 25.