Publications by authors named "Haohai Yu"

104 Publications

Tm:YAG single-crystal fiber laser.

Opt Lett 2021 Sep;46(18):4454-4457

In this Letter, to the best of our knowledge, we present the first thulium (Tm) single-crystal fiber (SCF) laser with free-space propagation of the laser beam only. The SCF is equipped with diffusion-bonded end caps of undoped YAG for better thermal management and enhancement of pump guiding. By utilizing mode matching and pump guiding in different SCF parts, an output power of 9.1 W is achieved at ∼2.02µ with a slope efficiency of 49.4%. This straightforward approach, which is also simple to realize and is based on combining the advantages of fiber-geometry structure and crystalline properties of Tm:YAG, is expected to be useful for 2 µm amplification stages in different time formats as well.
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http://dx.doi.org/10.1364/OL.434618DOI Listing
September 2021

Laser Synthesis and Microfabrication of Micro/Nanostructured Materials Toward Energy Conversion and Storage.

Nanomicro Lett 2021 Jan 4;13(1):49. Epub 2021 Jan 4.

Collaborative Innovation Center of Technology and Equipment for Biological Diagnosis and Therapy in Universities of Shandong, Institute for Advanced Interdisciplinary Research (iAIR), University of Jinan, Jinan, 250022, People's Republic of China.

Nanomaterials are known to exhibit a number of interesting physical and chemical properties for various applications, including energy conversion and storage, nanoscale electronics, sensors and actuators, photonics devices and even for biomedical purposes. In the past decade, laser as a synthetic technique and laser as a microfabrication technique facilitated nanomaterial preparation and nanostructure construction, including the laser processing-induced carbon and non-carbon nanomaterials, hierarchical structure construction, patterning, heteroatom doping, sputtering etching, and so on. The laser-induced nanomaterials and nanostructures have extended broad applications in electronic devices, such as light-thermal conversion, batteries, supercapacitors, sensor devices, actuators and electrocatalytic electrodes. Here, the recent developments in the laser synthesis of carbon-based and non-carbon-based nanomaterials are comprehensively summarized. An extensive overview on laser-enabled electronic devices for various applications is depicted. With the rapid progress made in the research on nanomaterial preparation through laser synthesis and laser microfabrication technologies, laser synthesis and microfabrication toward energy conversion and storage will undergo fast development.
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http://dx.doi.org/10.1007/s40820-020-00577-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8187667PMC
January 2021

Self-mode-locked alexandrite femtosecond lasers with multi-GHz repetition rates.

Opt Lett 2021 Apr;46(8):1979-1982

We report the laser-diode pumped multi-gigahertz (GHz) self-mode-locked alexandrite femtosecond (fs) lasers for the first time, to the best of our knowledge. Using a simple linear cavity, stable mode-locked laser was achieved with a repetition rate of 3.6 GHz and a pulse width of 237 fs. Additionally, the second-harmonic mode-locked pulse was realized with a repetition rate of 7.5 GHz and a pulse width of 201 fs based on the Fabry-Perot effect generated in the laser cavity. It was observed that this laser possesses advantages of high repetition rate and short pulse width that enable the development of promising applications in modern ultrafast photonics.
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http://dx.doi.org/10.1364/OL.423249DOI Listing
April 2021

Mid-infrared pulsed nanosecond difference frequency generation of oxide LGN crystal up to 5.7 µm.

Opt Lett 2021 Feb;46(4):785-788

We demonstrate the tunable difference frequency generation (DFG) of an oxide (LGN) crystal pumped by near-infrared lasers with nanosecond pulses for the first time to our knowledge. The type I and II phase-matching conditions of DFG were calculated in the mid-infrared region. With the processed LGN crystals, tunable lasers in the wavelength range from 4.4 to 5.7 µm and 4.56 to 5.6 µm were achieved under type II and I phase-matching conditions, respectively, with the maximum output energy of 13.1 µJ, which agreed well with the theoretical calculation. This work provides the kind of promising mid-infrared nonlinear crystals for the pumping of nanosecond pulsed lasers as well as a tunable mid-infrared laser source at a wavelength over 5 µm in further photonic applications.
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http://dx.doi.org/10.1364/OL.418215DOI Listing
February 2021

Na MQ (M=Zn, Cd; Q=S, Se): Promising New Ternary Infrared Nonlinear Optical Materials.

Chemistry 2021 Apr 8;27(21):6538-6544. Epub 2021 Mar 8.

CAS Key Laboratory of Functional Materials and Devices for Special, Environments, Xinjiang Technical Institute of Physics & Chemistry, CAS, Xinjiang Key Laboratory of Electronic Information, Materials and Devices, 40-1 South Beijing Road, Urumqi, 830011, P.R. China.

Four sodium-based ternary IR nonlinear optical (NLO) materials, Na MQ (M=Zn, Cd; Q=S, Se), were prepared through a high-temperature flux method. The crystal structure of the compounds is built up of isolated [MQ ] tetrahedra and a 3D framework formed by the NaQ (n=4, 5) units. The two selenides, Na MSe (M=Zn, Cd), as promising IR NLO materials, show moderate second-harmonic generation (SHG) responses (0.9 and 0.5×AgGaS ) with good phase-matching behavior, as well as high laser damage thresholds (2 and 1.9×AgGaS ). The two sulfides, Na MS (M=Zn, Cd), exhibit higher laser damage thresholds (13 and 4×AgGaS ), but smaller SHG responses (0.3 and 0.2×AgGaS ). Theoretical calculations and statistical analyses indicate that the SHG effect and band gap in the compounds originate mainly from the distorted NaQ NLO-active units with a short Na-S bond length, which provides a new insight into the design of novel IR NLO materials.
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http://dx.doi.org/10.1002/chem.202005404DOI Listing
April 2021

In situ and tunable structuring of semiconductor-in-glass transparent composite.

iScience 2021 Jan 27;24(1):101984. Epub 2020 Dec 27.

State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.

Semiconductor-in-glass composites are an exciting class of photonic materials for various fundamental applications. The significant challenge is the scalable elaboration of composite with the desirable combination of tunable structure, high semiconductor loading ratio, and excellent transparency. Here we report that the topological engineering strategy via hybridization of the glass network former enables to surmount the aforementioned challenge. It not only facilitates the precipitation of (GaAl)O domains with continuously tunable composition but also allows to simultaneously refine the grain size and enhance the crystallinity. In addition, the composites exhibit excellent transparency and can host various active dopants. We demonstrate the attractive broadband optical response of the composite and achieve the pulse laser operation in mid-infrared waveband. The findings are expected to provide a fundamental principle of modification in hybrid system for generation of high-performance semiconductor-in-glass composites.
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http://dx.doi.org/10.1016/j.isci.2020.101984DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7803658PMC
January 2021

Three-dimensional nonlinear photonic crystal in naturally grown potassium-tantalate-niobate perovskite ferroelectrics.

Light Sci Appl 2020 Nov 24;9(1):193. Epub 2020 Nov 24.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan, 250100, China.

Since quasi-phase-matching of nonlinear optics was proposed in 1962, nonlinear photonic crystals were rapidly developed by ferroelectric domain inversion induced by electric or light poling. The three-dimensional (3D) periodical rotation of ferroelectric domains may add feasible modulation to the nonlinear coefficients and break the rigid requirements for the incident light and polarization direction in traditional quasi-phase-matching media. However, 3D rotating ferroelectric domains are difficult to fabricate by the direct external poling technique. Here, we show a natural potassium-tantalate-niobate (KTN) perovskite nonlinear photonic crystal with spontaneous Rubik's cube-like domain structures near the Curie temperature of 40 °C. The KTN crystal contains 3D ferroelectric polarization distributions corresponding to the reconfigured second-order susceptibilities, which can provide rich reciprocal vectors to compensate for the phase mismatch along an arbitrary direction and polarization of incident light. Bragg diffraction and broadband second-harmonic generation are also presented. This natural nonlinear photonic crystal directly meets the 3D quasi-phase-matching condition without external poling and establishes a promising platform for all-optical nonlinear beam shaping and enables new optoelectronic applications for perovskite ferroelectrics.
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http://dx.doi.org/10.1038/s41377-020-00427-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7687908PMC
November 2020

Few-cycle pulses tunable from 3 to 7  µm via intrapulse difference-frequency generation in oxide LGN crystals.

Opt Lett 2020 Oct;45(20):5728-5731

An ultrashort mid-infrared (IR) source beyond 5 µm is crucial for a plethora of existing and emerging applications in spectroscopy, medical diagnostics, and high-field physics. Nonlinear generation of such sources from well-developed near-IR lasers, however, remains a challenge due to the limitation of mid-IR crystals. Based on oxide (LGN) crystals, here we report the generation of femtosecond pulses tunable from 3 to 7 µm by intrapulse difference-frequency generation of 7.5 fs, 800 nm pulses. The efficiency and bandwidth dependences on pump polarization and crystal length are studied for both Type-I and Type-II phase-matching configurations. Maximum pulse energy of ∼10 is generated at 5.2 µm with a conversion efficiency of ∼0.14. Because of the few-cycle pump pulse duration, the generated mid-IR pulses are as short as about three cycles. These results, to the best of our knowledge, represent the first experimental demonstration of LGN in generating mid-IR ultrashort pulses.
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http://dx.doi.org/10.1364/OL.406025DOI Listing
October 2020

High-efficiency Er-doped yttrium gallium garnet laser resonantly pumped by a laser diode at 1.47  µm.

Opt Lett 2020 Aug;45(15):4361-4364

The spectroscopic and laser properties of an -doped yttrium gallium garnet crystal, (YGG), are studied. The stimulated emission cross section is 1.4×10 at 1.65 µm. A continuous-wave laser resonantly pumped by a laser diode at 1.47 µm is demonstrated, delivering a maximum output power of 3.34 W. Benefiting from the low phonon energy of the YGG host, the corresponding slope efficiency is as high as ∼42. To the best of our knowledge, this is the highest slope efficiency from the laser-diode resonantly pumped Er lasers at room temperature in the 1.6 µm spectral range.
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http://dx.doi.org/10.1364/OL.401155DOI Listing
August 2020

27 W 2.1 µm OPCPA system for coherent soft X-ray generation operating at 10 kHz.

Opt Express 2020 Mar;28(6):8724-8733

We developed a high power optical parametric chirped-pulse amplification (OPCPA) system at 2.1 µm harnessing a 500 W Yb:YAG thin disk laser as the only pump and signal generation source. The OPCPA system operates at 10 kHz with a single pulse energy of up to 2.7 mJ and pulse duration of 30 fs. The maximum average output power of 27 W sets a new record for an OPCPA system in the 2 µm wavelength region. The soft X-ray continuum generated through high harmonic generation with this driver laser can extend to around 0.55 keV, thus covering the entire water window (284 eV - 543 eV). With a repetition rate still enabling pump-probe experiments on solid samples, the system can be used for many applications.
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http://dx.doi.org/10.1364/OE.386588DOI Listing
March 2020

Pushing periodic-disorder-induced phase matching into the deep-ultraviolet spectral region: theory and demonstration.

Light Sci Appl 2020 18;9:45. Epub 2020 Mar 18.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan, 250100 China.

Nonlinear frequency conversion is a ubiquitous technique that is used to obtain broad-range lasers and supercontinuum coherent sources. The phase-matching condition (momentum conservation relation) is the key criterion but a challenging bottleneck in highly efficient conversion. Birefringent phase matching (BPM) and quasi-phase matching (QPM) are two feasible routes but are strongly limited in natural anisotropic crystals or ferroelectric crystals. Therefore, it is in urgent demand for a general technique that can compensate for the phase mismatching in universal nonlinear materials and in broad wavelength ranges. Here, an additional periodic phase (APP) from order/disorder alignment is proposed to meet the phase-matching condition in arbitrary nonlinear crystals and demonstrated from the visible region to the deep-ultraviolet region (e.g., LiNbO and quartz). Remarkably, pioneering 177.3-nm coherent output is first obtained in commercial quartz crystal with an unprecedented conversion efficiency above 1‰. This study not only opens a new roadmap to resuscitate those long-neglected nonlinear optical crystals for wavelength extension, but also may revolutionize next-generation nonlinear photonics and their further applications.
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http://dx.doi.org/10.1038/s41377-020-0281-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7078200PMC
March 2020

Highly Efficient Super-Continuum Generation on an Epsilon-Near-Zero Surface.

ACS Omega 2020 Feb 30;5(5):2458-2464. Epub 2020 Jan 30.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan 250100, China.

The efficient super-continuum (SC) generation on a surface via a high-order photo-electron interaction is a great challenge for integrated optics because the surficial nonlinear optical efficiency is usually limited by finite light-matter interaction length and electric field intensity. Nowadays, epsilon-near-zero (ENZ) materials, showing infinite enhanced electronic field in theory, provide a kind of new platform to obtain a giant nonlinear response on the surface. Here, under the irradiation of a multiwavelength laser, an exotic and efficient SC generation from 406 to 1100 nm on the ENZ aluminum-doped zinc oxide surface was experimentally demonstrated by diversified nonlinear processes, including second harmonic generation, third harmonic generation, four wavelength mixing, and cascading stimulated Raman scattering. Particularly, an unprecedented nonlinear conversion efficiency of 3.94% W, 16 orders of magnitude higher than the common surface case (about 10% W), was presented.
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http://dx.doi.org/10.1021/acsomega.9b04026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7017490PMC
February 2020

Defect Engineering of MoS for Room-Temperature Terahertz Photodetection.

ACS Appl Mater Interfaces 2020 Feb 28;12(6):7351-7357. Epub 2020 Jan 28.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials , Shandong University , Jinan 250100 , China.

Two-dimensional (2D) materials have exotic intrinsic electronic band structures and are considered as revolutionary foundations for novel nanodevices. Band engineering of 2D materials may pave a new avenue to overcome numerous challenges in modern technologies, such as room temperature (RT) photodetection of light with photon energy below their band gaps. Here, we reported the pioneering RT MoS-based photodetection in the terahertz (THz) region via introducing Mo and S vacancies for rational band gap engineering. Both the generation and transport of extra carriers, driven by THz electromagnetic radiations, were regulated by the vacancy concentration as well as the resistivity of MoS samples. Utilizing the balance between the carrier concentration fluctuation and carrier-scattering probability, a high RT photoresponsivity of 10 mA/W at 2.52 THz was realized in an Mo-vacancy-rich MoS sample. This work overcomes the challenge in the excessive dark current of RT THz detection and offers a convenient way for further optoelectronic and photonic devices based on band gap-engineered 2D materials.
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http://dx.doi.org/10.1021/acsami.9b21671DOI Listing
February 2020

Liquid-phase growth and optoelectronic properties of two-dimensional hybrid perovskites CHNHPbX (X = Cl, Br, I).

Nanoscale 2020 Jan;12(2):1100-1108

Institute of Functional Crystals, and Tianjin Key Laboratory of Functional Crystal Materials, Tianjin University of Technology, Tianjin 300384, China.

The hybrid perovskite CH3NH3PbX3 (X = Cl, Br, I) is a promising material for developing novel optoelectronic devices. Due to its intrinsic non-layered crystal structure, it remains challenging to synthesize two-dimensional (2D) single-crystalline CH3NH3PbX3 with nanoscale thickness. Here, we report a bottom-up approach to fabricate large CH3NH3PbX3 2D crystals via liquid-phase growth on a mica substrate. The strong potassium-halogen interactions at the perovskite/mica interface decrease the interface energy, driving the striking in-plane growth of the perovskite. The grown 2D CH3NH3PbBr3 crystal was characterized as 8 nm in thickness and hundreds of micrometers in lateral size. Weak exciton binding energy was crucial for improving the photoelectric performance of 2D CH3NH3PbBr3. A visible-light photodetector with a metal/insulator/perovskite configuration was finally achieved with a photoresponsivity of 126 A W-1 and a bandwidth exceeding 80 kHz. Our work proves that the liquid-phase growth on mica is a controllable method to grow 2D hybrid CH3NH3PbX3 perovskites, which can facilitate both device applications and fundamental investigations.
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http://dx.doi.org/10.1039/c9nr07981eDOI Listing
January 2020

Surface Nonlinear Optics on Centrosymmetric Dirac Nodal-Line Semimetal ZrSiS.

Adv Mater 2020 Jan 21;32(2):e1904498. Epub 2019 Nov 21.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan, 250100, China.

Gapless surface states (SSs) are features of topological semimetals and are extensively observed. Nowadays, the emerging question is whether the SSs possess exotic and applicable properties. Here, associated with the symmetrical selection rule for nonlinear optical materials, the surface nonlinear optics on a centrosymmetric Dirac nodal-line semimetal ZrSiS crystal is studied and it is found that the SSs bring record nonlinear susceptibilities. The unprecedented conversion efficiencies for second and third harmonic generations are 0.11‰ and 0.43‰, respectively, more than ten orders of magnitude larger than the typical surface second harmonic generation. This work discovers a new route toward studying the SSs for applications in nonlinear photonics.
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http://dx.doi.org/10.1002/adma.201904498DOI Listing
January 2020

Power scaling of the self-frequency-doubled quasi-two-level Yb:YCOB laser with a 30% slope efficiency.

Opt Lett 2019 Nov;44(21):5157-5160

The lab-on-chip integration of photonic devices has been attracting increasing attention recently. Multifunctional materials provide natural platforms for the desirable performance by the coupling of different functionalities. The insufficient coupling efficiency of the laser and nonlinear processes in self-frequency-doubled (SFD) lasers is the limiting factor for the output power and further practical applications. Here we demonstrate a SFD Yb-doped calcium yttrium oxoborate (Yb:YCOB) crystal laser with an unprecedented slope efficiency of 30% and output power of 6.2 W at 513 nm. The successful realization of this laser operating in a quasi-two-level configuration is based on enhanced coupling of the laser and frequency-doubling processes using a monolithic configuration, benefiting from an ultimately small laser quantum defect, the anisotropic gain cross sections, and the high effective nonlinearity of the monoclinic YCOB outside the principal planes. Solid-state lasers in the spectral range around 510 nm are scarce, and the results not only present a significant advancement in the field of SFD lasers, but also pave the way for future applications of such green lasers, especially in areas such as medical treatment, daily life, and scientific investigations.
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http://dx.doi.org/10.1364/OL.44.005157DOI Listing
November 2019

Artificial Second-Order Nonlinear Optics in a Centrosymmetric Optical Material BiVO: Breaking the Prerequisite for Nonlinear Optical Materials.

ACS Omega 2019 Jan 14;4(1):1045-1052. Epub 2019 Jan 14.

State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, PR China.

Second-order nonlinear optics (NLO) is the foundation of frequency conversion for the generation of coherent light at frequencies where lasers have no emissions or operate poorly. The prerequisite for NLO materials is noncentrosymmetric symmetry that can generate an effectively non-counterbalanced spontaneous electronic polarization. Here, we propose that this material restriction can be broadened by controlling the electron distribution with a local internal electrostatic field (IEF), and we demonstrate artificially created and manipulated second harmonic generation (SHG) in a centrosymmetric optical material, a superimposed Co- and Mo-doped BiVO thin film with 2/ point group symmetry, where a homojunction producing tunable effective polarization is formed. The SHG was characterized and tuned by IEF. This work breaks the structural symmetry constraint on NLO materials. Besides, the phase-matching-like condition was realized for the further improvement of the efficient frequency conversion. Because polarization is also a prerequisite for many other functions besides SHG, we believe that this work should provide some inspiration for the further development of optoelectronic, photonic, and electronic materials.
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http://dx.doi.org/10.1021/acsomega.8b02453DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648906PMC
January 2019

Structural modulation induced by M metals in BaMQX (M = Al, Ga, In; Q = S, Se; X = Cl, Br): an experimental and computational analysis.

Dalton Trans 2019 Sep 7;48(33):12713-12719. Epub 2019 Aug 7.

CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang Technical Institute of Physics & Chemistry, CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, 40-1 South Beijing Road, Urumqi 830011, China.

Four new chalcohalides BaAlQX (Q = S, Se; X = Cl, Br) have been discovered by a conventional high-temperature method. All of them crystallize in the Pnma space group. The structure is composed of zigzag XBa layers and isolated AlQ tetrahedra. Detailed structural comparisons show that the cation size of the M metals and variable coordination modes of the Ba cations cooperatively influence the framework geometries of the title compounds. The first principles method was also used to investigate the electronic structures and optical properties. Their calculated birefringences range from 0.044 to 0.050 @1064 nm. Real space atom cutting analysis shows that the AlS, GaS, and InS tetrahedra make the main contribution to the birefringence.
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http://dx.doi.org/10.1039/c9dt01833fDOI Listing
September 2019

Kerr-lens mode-locked Pr:LuLiF laser.

Opt Lett 2019 Aug;44(15):3665-3668

We demonstrate the Kerr-lens mode-locked Pr:LuLiF (Pr:LLF) laser pumped by a blue laser diode (LD). By theoretical calculation of the group velocity dispersion in the laser gain, the compensation was employed for the realization of the continuous-wave mode-locked laser at the wavelength of 604 nm with the pulse width of 1.1 ps which, to the best of our knowledge, is the shortest pulse width in the Pr ion doped crystal lasers pumped with LDs. It can be believed that the present Pr:LLF laser should provide some inspiration for the development of the blue LD pumped visible lasers, especially in the mode-locking laser operation.
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http://dx.doi.org/10.1364/OL.44.003665DOI Listing
August 2019

Fs-laser-written thulium waveguide lasers Q-switched by graphene and MoS.

Opt Express 2019 Mar;27(6):8745-8755

We report the generation of mid-infrared (~2 µm) high repetition rate (MHz) sub-100 ns pulses in buried thulium-doped monoclinic double tungstate crystalline waveguide lasers using two-dimensional saturable absorber materials, graphene and MoS. The waveguide (propagation losses of ~1 dB/cm) was micro-fabricated by means of ultrafast femtosecond laser writing. In the continuous-wave regime, the waveguide laser generated 247 mW at 1849.6 nm with a slope efficiency of 48.7%. The laser operated at the fundamental transverse mode with a linearly polarized output. With graphene as a saturable absorber, the pulse characteristics were 88 ns / 18 nJ (duration / energy) at a repetition rate of 1.39 MHz. Even shorter pulses of 66 ns were achieved with MoS. Graphene and MoS are therefore promising for high repetition rate nanosecond Q-switched infrared waveguide lasers.
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http://dx.doi.org/10.1364/OE.27.008745DOI Listing
March 2019

8.8 GHz Q-switched mode-locked waveguide lasers modulated by PtSe saturable absorber.

Opt Express 2019 Mar;27(6):8727-8737

We demonstrate high-repetition-rate fundamentally Q-switched mode-locked Nd:YAG waveguide laser modulated by platinum diselenide (PtSe) saturable absorber. The laser operation platform is a femtosecond laser-written monolithic Nd:YAG waveguide, and the saturable absorber is large-area few-layer PtSe that possesses relatively lower saturation intensity and higher modulation depth in comparison with graphene. With the superb ultrafast nonlinear saturable absorption properties of as-synthesized PtSe, the waveguide laser could operate at ~8.8 GHz repetition rate and ~27 ps pulse duration, while maintaining a relatively high slope efficiency of 26% and high stability with signal-to-noise ratio (SNR) up to 54 dB. Our work indicates the promising applications of laser-written Nd:YAG waveguides and atomically thin PtSe for on-chip integration of GHz laser sources toward higher repetition rates and shorter pulse duration.
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http://dx.doi.org/10.1364/OE.27.008727DOI Listing
March 2019

Demonstration of a White Laser with V C MXene-Based Quantum Dots.

Adv Mater 2019 Jun 29;31(24):e1901117. Epub 2019 Apr 29.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan, 250100, China.

Multicolor photoluminescence over the full visible color spectrum is critical in many modern science and techniques, such as full-color lighting, displays, biological and chemical monitoring, multiband communication, etc., but the ultimate white lasing especially on the nanoscale is still a challenge due to its exacting requirements in the balance of the gain and optical feedback at different wavelengths. Recently, 2D transition metal carbides (MXenes) have emerged, with some superior chemical, physical, and environmental properties distinguishing them from traditional 2D materials. Here, a white laser with V C MXene quantum dots (MQDs) is originally demonstrated by constructing a broadband nonlinear random scattering system with enhanced gain. The excitation-dependent photoluminescence of V C MQDs is enhanced by passivation and characterized, and their localized nonlinear random scattering is realized by the generation of excitation-power-dependent solvent bubbles. With the optimized excitation, the blue, green, yellow, and red light is amplified and simultaneously lased. This work not only provides a kind of promising material for white lasers, but also a design strategy of novel photonics for further applications.
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http://dx.doi.org/10.1002/adma.201901117DOI Listing
June 2019

BaB O F : A Barium Fluorooxoborate with a Unique [B O F] Layer and Short Cutoff Edge.

Chemistry 2019 May 25;25(27):6693-6697. Epub 2019 Apr 25.

CAS Key Laboratory of Functional Materials and Devices for Special, Environments, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences; Xinjiang Key Laboratory, of Electronic Information Materials and Devices, 40-1 South Beijing Road, Urumqi, 830011, P. R. China.

Substitution of oxygen by fluorine in the borate group offers a materials platform from which intriguing structure and functionality may arise. Herein, we report a new fluorooxoborate, BaB O F , synthesized by introducing the F atoms into the BaO-B O system. BaB O F exhibits a unique oxyfluoride layer [B O F] and a deep-ultraviolet cutoff edge below 180 nm. The effect of the introduction of F atoms on the structure and optical property of the borate group has been investigated; this should be useful to further expand borate chemistry and materials.
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http://dx.doi.org/10.1002/chem.201806350DOI Listing
May 2019

Tailoring optical nonlinearities of LiNbO crystals by plasmonic silver nanoparticles for broadband saturable absorbers.

Opt Express 2018 Nov;26(24):31276-31289

We report on the synthesis of plasmonic Ag nanoparticles (NPs) embedded in a LiNbO crystal (AgNP:LN) by ion implantation and its application as an efficient broadband saturable absorber (SA) to realize Q-switched pulsed laser generation at both visible and near-infrared wavelength bands. The nonlinear optical response of AgNP:LN is considered as a synergistic effect between Ag NPs and LiNbO. We apply the AgNP:LN as visible-near-infrared broadband saturable absorbers (SAs) into Pr:LuLiF bulk and Nd:YVO waveguide laser cavity, achieving efficient passively Q-switched laser at 639 nm and 1064 nm, respectively. This work paves a new way to tailor the nonlinear optical response of LiNbO crystals by using plasmonic Ag NPs, manifesting the significant potential as broadband SAs in the aspect of pulsed lasing.
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http://dx.doi.org/10.1364/OE.26.031276DOI Listing
November 2018

High-efficiency 3  μm Er:YGG crystal lasers.

Opt Lett 2018 Dec;43(23):5873-5876

By balancing energy transfer and thermal effects, we demonstrate efficient erbium-doped yttrium gallium garnet (Er:YGG) crystal lasers at a wavelength of 2.82-2.92 μm for the first time, to the best of our knowledge. Associated with the influence of doping concentration on energy transfer and thermal effects, the Er doping concentration was optimized to be 10 at.%, and with the optimized crystal, the maximum continuous-wave output power was 1.38 W, corresponding to the slope efficiency of 35.4% approaching the theoretical quantum limits. The thermal effects during the laser process were discussed. We believe that this work should be helpful for optimizing the erbium-doped gain for the 3 μm laser and the development of 3 μm lasers.
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http://dx.doi.org/10.1364/OL.43.005873DOI Listing
December 2018

Oriented zinc oxide nanorods: A novel saturable absorber for lasers in the near-infrared.

Beilstein J Nanotechnol 2018 23;9:2730-2740. Epub 2018 Oct 23.

Functional Materials, Applied Physics Department, School of Engineering Sciences, KTH Royal Institute of Technology, Isafjordsgatan 22, SE-164 40 Kista Stockholm, Sweden.

Zinc oxide (ZnO) nanorods (NRs) oriented along the crystallographic [001] axis are grown by the hydrothermal method on glass substrates. The ZnO NRs exhibit a broadband (1-2 µm) near-IR absorption ascribed to the singly charged zinc vacancy V . The saturable absorption of the ZnO NRs is studied at ≈1 µm under picosecond excitation, revealing a low saturation intensity, ≈10 kW/cm, and high fraction of the saturable losses. The ZnO NRs are applied as saturable absorbers in diode-pumped Yb (≈1.03 µm) and Tm (≈1.94 µm) lasers generating nanosecond pulses. The ZnO NRs grown on various optical surfaces are promising broadband saturable absorbers for nanosecond near-IR lasers in bulk and waveguide geometries.
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http://dx.doi.org/10.3762/bjnano.9.255DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6204775PMC
October 2018

Room-Temperature Ultrabroadband Photodetection with MoS by Electronic-Structure Engineering Strategy.

Adv Mater 2018 Dec 11;30(50):e1804858. Epub 2018 Oct 11.

Institute of Functional Crystal Materials, Tianjin University of Technology, Tianjin, 300384, China.

Photodetection using semiconductors is critical for capture, identification, and processing of optical information. Nowadays, broadband photodetection is limited by the underdeveloped mid-IR photodetection at room temperature (RT), primarily as a result of the large dark currents unavoidably generated by the Fermi-Dirac distribution in narrow-bandgap semiconductors, which constrains the development of some modern technologies and systems. Here, an electronic-structure strategy is proposed for designing ultrabroadband covering mid- and even far-IR photodetection materials operating at RT and a layered MoS is manifested with an engineered bandgap of 0.13 eV and modulated electronic state density. The sample is designed by introducing defect energy levels into layered MoS and its RT photodetection is demonstrated for wavelengths from 445 nm to 9.5 µm with an electronic state density-dependent peak photoresponsivity of 21.8 mA W in the mid-IR region, the highest value among all known photodetectors. This material should be a promising candidate for modern optoelectronic devices and offers inspiration for the design of other optoelectronic materials.
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http://dx.doi.org/10.1002/adma.201804858DOI Listing
December 2018

A Wide-Range Photosensitive Weyl Semimetal Single Crystal-TaAs.

Adv Mater 2018 Oct 10;30(43):e1801372. Epub 2018 Sep 10.

State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University, Jinan, 250100, China.

Mid- and even long-infrared photodetection is highly desired for various modern optoelectronic devices, and photodetectors that operate at room temperature (RT) remain challenging and are being extensively sought. Recently, the Weyl semimetal has attracted much interest, and its Lorentz invariance can be broken to have tilted chiral Weyl cones around the Fermi level, which indicates that the photocurrent can be generated by the incident photons at arbitrarily long wavelengths. Furthermore, the atypical linear dispersion bands in Weyl cones result in high carrier mobility and quadratic energy dependence of the density of states, which can enhance the efficiency of the photocurrent and suppress thermal carriers, in addition to its favorable large absorption coefficient. In this study, a Weyl semimetal TaAs photodetecting prototype is reported, which operates at RT with an outstanding response that ranges from the visible to the long-infrared range. This study indicates that the Weyl semimetal TaAs should boost the development of modern optoelectronics and photonics.
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http://dx.doi.org/10.1002/adma.201801372DOI Listing
October 2018

78  fs SWCNT-SA mode-locked Tm:CLNGG disordered garnet crystal laser at 2017  nm.

Opt Lett 2018 Sep;43(17):4268-4271

A passively mode-locked Tm:CLNGG laser using single-walled carbon nanotubes (SWCNT) as a saturable absorber (SA) is demonstrated at 2017 nm. Pulses as short as 78 fs are generated at an 86 MHz repetition rate with an average output power of 54 mW. By increasing the output coupling from 0.5% to 1.5%, a higher power of 100 mW is achieved for slightly longer pulses with a duration of 105 fs at 1996 nm.
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http://dx.doi.org/10.1364/OL.43.004268DOI Listing
September 2018
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