Publications by authors named "Dazhi Lu"

11 Publications

  • Page 1 of 1

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

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

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

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

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

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

Validation of the angular quasi-phase-matching theory for the biaxial optical class using PPRKTP.

Opt Lett 2018 Sep;43(17):4276-4279

We report the first experimental validation of angular quasi-phase-matching (AQPM) theory in a biaxial crystal by performing second-harmonic generation (SHG) in the periodically-poled Rb-doped KTiOPO (PPRKTP) crystal cut as a sphere. Both AQPM and birefringence phase-matching (BPM) angles were measured thanks to a Kappa circle.
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http://dx.doi.org/10.1364/OL.43.004276DOI Listing
September 2018

High repetition rates optically active langasite electro-optically Q-switched laser at 1.34 μm.

Opt Express 2017 Oct;25(20):24007-24014

An electro-optically Q-switched pulsed laser at 1.34 μm with a repetition rate of 100 kHz applying optically active langasite (LaGaSiO) crystal has been reported. With Nd:YVO as laser crystal, the electro-optically Q-switched pulsed lasers were obtained with the maximum repetition rate of 100 kHz, maximum average output power of 2.42 W, and a minimum pulse width of 2.4 ns. Based on the theory of rate equations, the optimal pulse energy of the electro-optical Q-switching could be calculated. The experimental results have been found to be matched well with the theoretical calculations. To the best of our knowledge, this work presents the highest repetition rate and shortest pulse width which are achieved by an electric-optic LGS Q-switching at the wavelength of 1.34 μm, and it enriches the material categories for generating the high repetition rate pulsed laser.
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http://dx.doi.org/10.1364/OE.25.024007DOI Listing
October 2017

Acentric langanite La3Ga5.5Nb0.5O14 crystal: a new nonlinear crystal for the generation of mid-infrared parametric light.

Opt Express 2016 Aug;24(16):17603-15

The mid-infrared spectral range extending from 2 to 6 μm is significant for scientific and technological applications. A promising nonlinear oxide crystal La3Ga5.5Nb0.5O14 (LGN) is proposed and fully characterized for the first time to our knowledge. The transparency range extends between 0.28 and 7.4 μm. The two principal refractive indices were measured and we found that the nonlinear coefficient d11 = 3.0 ± 0.1 pm/V at 0.532 μm. The simultaneous fit of data allowed us to refine the Sellmeier equations of LGN and to calculate the tuning curves for optical parametric generation (OPG) pumped at 1.064 μm. Calculations are consistent with recorded data and also show the generation of a supercontinuum between 1.5 and 3.5 μm when pumped at 0.98 μm by a Ti:Sapphire laser.
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http://dx.doi.org/10.1364/OE.24.017603DOI Listing
August 2016

Self-frequency-doubled vibronic yellow Yb:YCOB laser at the wavelength of 570  nm.

Opt Lett 2016 Mar;41(5):1002-5

A watt-level self-frequency-doubled yellow laser at the 570 nm wavelength was realized by taking advantage of the vibronic emission of a Yb3+ doped calcium yttrium oxoborate (Yb:YCOB) crystal cut along the optimized direction out of the principal planes with the maximum effective nonlinear coefficient. Fluorescence spectroscopic properties of Yb:YCOB were studied, which showed that it had broad and anisotropic vibronic emission with a small peak at ∼1130  nm. By suppressing the electronic emission, the polarized vibronic Yb:YCOB radiation was realized with the fundamental wavelength shifting from 1130 nm to 1140 nm. By employing the self-frequency-doubling behavior of Yb:YCOB, the self-frequency-doubled yellow laser was achieved with a maximum output power of 1.08 W at 570 nm. This work provides an unprecedented and efficient way to generate yellow lasers with a compact microchip structure that may have promising applications in some regimes including medicine, entertainment, and scientific research.
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http://dx.doi.org/10.1364/OL.41.001002DOI Listing
March 2016
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