Visible Solid-state Lasers Research Articles

Composition dependence visible fluorescence from praseodymium ions doped Al2O3–CaO-M(M=B2O3, GeO2, Ga2O3) glasses

Pr3+ doped Al2O3–CaO based glasses were excellent candidate optical gain mediums for visible solid-state lasers due to its wide transmittance region and excellent mechanical properties. However, poor glass-forming ability limited its further application in visible fiber laser. In this work, B2O3, GeO2, Ga2O3 were employed for modifying the glass-forming ability and lowing the melting temperature of the Al2O3–CaO based glasses. By introducing 15 mol% GeO2 and Ga2O3, the thermal stability ΔT were enlarged to be 199 and 264 °C, respectively. The influence of glass composition on the fluorescence characteristic of Pr3+ were systematically investigated. For lower doping concentration, different multiphonon relaxation rare of 3P0 and 1D2 energy levels accounting for the different fluorescence spectra of Pr3+ doped Al–Ga, Al–Ge and Al–B glasses, while for the higher doping concentration, cross relaxation processes lead to the fluorescence was gradually dominated by the transition of 3P0 with increasing Pr3+ concentration.

Optical and spectroscopic studies of Dy3+ ions doped Alumino tungsten borate glasses for w-LEDs applications

Alumino tungsten borate (AlWB) glasses doped with dysprosium ions are prepared by melt-quenching method and characterized using spectroscopic techniques such as optical absorption, photoluminescence (PL), and decay spectral studies to comprehend the importance in photonic devices, visible solid state lasers, and other applications. The amorphous nature of the as-prepared glasses were confirmed by XRD studies. The oscillator strengths are measured by using absorption spectra are intern used to evaluate the Judd-Ofelt (Ω2, Ω4, and Ω6) parameters. The PL spectra of the as-prepared glasses manifested three significant emission bands at 483 nm (blue), 575 nm (yellow) and 664 nm (red), and their corresponding electronic transitions are identified from 4F9/2 to 6H15/2,6H13/2 and 6H11/2 respectively. Various radiative parameters such as branch ratio (βR), transition probability (AR), radiative lifetime (τR), effective bandwidth (Δλp), and stimulated emission cross-section (σse) have been calculated. The CIE Chromaticity coordinates evaluated from the emission spectra of Dy-doped AlWB glasses reveal white light emission. Quantum efficiency values are evaluated by correlating the radiative lifetime with the experimental lifetime values measured from the PL decay spectral features. The data acquired from the as-prepared glasses allows us to contemplate that, the titled glasses are suitable to fabricate photonic devices. such as white LED’s and lasers.

Mid-IR spectroscopy with NIR grating spectrometers.

Mid-infrared (mid-IR) spectroscopy is a crucial workhorse for a plethora of analytical applications and is suitable for diverse materials, including gases, polymers or biological tissue. However, this technologically significant wavelength regime between 2.5-10 µm suffers from technical limitations primarily related to the large noise in mid-IR detectors and the complexity and cost of bright, broadband mid-IR light sources. Here, using highly non-degenerate, broadband photon pairs from bright spontaneous parametric down-conversion (SPDC) in a nonlinear interferometer, we circumvent these limitations and realise spectroscopy in the mid-IR using only a visible (VIS) solid-state laser and an off-the-shelf, commercial near-infrared (NIR) grating spectrometer. With this proof-of-concept implementation, covering a broad range from 3.2 µm to 4.4 µm we demonstrate short integration times down to 1 s and signal-to-noise ratios above 200 at a spectral resolution from 12 cm-1 down to 1.5 cm-1 for longer integration times. Through the analysis of polymer samples and the ambient CO2 in our laboratory, we highlight the potential of this measurement technique for real-world applications.

Transition-metal-doped saturable absorbers for passive Q-switching of visible lasers

We experimentally investigate crystals doped with tetravalent chromium or divalent cobalt as saturable absorbers for passive Q-switching of visible solid-state lasers. The recovery time of the ground-state and excited-state absorption cross sections are determined by pump-probe and Z-scan measurements, respectively. We provide saturation intensities, useful wavelength ranges of the investigated materials, and advices to realize passive Q-switching of visible lasers using these crystals as saturable absorbers.

Gold nanostars as the saturable absorber for a Q-switched visible solid-state laser.

We demonstrated a passively Q-switched visible Pr:YLF laser using the gold nanostars (GNSs) as the saturable absorber (SA). The nonlinear saturable absorption properties at 639nm were measured, and the modulation and saturable fluence were calculated to be 3% and 0.3 GW/cm2, respectively. With the GNSs SA, the efficient passively Q-switched lasers were obtained at 639nm and 721nm, respectively. The maximum output powers and shortest pulse widths were (256mW, 168ns) at 639nm and (238mW, 198ns) for 721nm. To the best of our knowledge, this is the first time there has been a visible bulk pulse laser using the GNSs as the SA. Our work indicates the GNSs could be excellent and promising optoelectronic devices in the visible domain.

CsPbBr_3 perovskite quantum dots: saturable absorption properties and passively Q-switched visible lasers

This work presents the saturable absorption (SA) properties of CsPbBr3 perovskite quantum dots (QDs). The perovskite QDs show excellent SA performance with a nonlinear absorption coefficient of −35×10−2 cm/GW and a figure of merit of 3.7×10−14 esu cm. Further, their use as saturable absorbers in a passively Q-switched visible solid-state laser for the generation of soliton pulses is demonstrated. These results demonstrate the potential for the perovskite QDs to act as saturable absorbers.

Few-layer Bi[formula omitted]Se[formula omitted]-based passively Q-switched Pr:YLF visible lasers

We report on diode-pumped Q-switched Pr:YLF lasers at deep red ∼721 nm, red ∼640 nm and orange ∼(607+604) nm, using a few-layer Bi2Se3 saturable absorber. The narrowest pulse widths, maximum pulse energies and pulse peak powers have been achieved to be about (368 ns, 0.17 μJ, 0.46 W), (210 ns, 0.16 μJ, 0.73 W) and (263 ns, 0.19 μJ, 0.71 W), respectively for the three wavelengths. This work reveals that Bi2Se3 is a promising saturable absorber for visible solid-state lasers.

Spectroscopic analysis of Pr3+:CaYAlO4 crystal

The polarized absorption, emission spectra and decay time measurements of Pr3+-doped CaYAlO4 single crystal have been performed at room temperature. Based on the Judd–Ofelt theory, the spectroscopic parameters \(\Upomega_{t} (t = 2,4,6)\), radiative transition probabilities, radiative lifetimes and branching ratios were obtained. The stimulated emission cross-section, fluorescence lifetimes and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results show that Pr3+:CaYAlO4 is a promising candidate for visible solid-state laser emission.

Luminescent properties of Yb3+-doped hexagonal Ln3BWO9 (Ln = Gd, Y)

We report the synthesis and spectroscopic characterization of polycrystalline Yb3+-doped (1, 2, and 5 at %) Ln3BWO9 (Ln = Gd and Y) borotungstates as candidate gain media for diode-pumped near-IR and visible solid-state lasers. Unpolarized luminescence and absorption spectra for the Yb3+ 2 F 7/2→2 F 5/2 transition are measured at T = 77 and 300 K, the lifetime of the 2 F 5/2 excited state is determined, and the emission cross section of the stimulated Yb3+ 2 F 5/2→2 F 7/2 transition in these compounds is evaluated. Offering a combination of nonlinear optical and lasing properties, the Ln3BWO9 (Ln = Gd, Y) hexagonal borotung-states can be used as bifunctional media for diode-pumped lasers with nonlinear laser frequency self-conversion.

Highly Uniform Tm3+-Doped NaYbF4Microtubes: Controlled Synthesis and Intense Ultraviolet Photoluminescence

Here, we present a facile and controlled synthesis of high-quality and uniform hexagonal phase NaYbF4 microtubes by a rational hydrothermal method. In addition, highly uniform and monodisperse NaYbF4 nanospheres and nanocubes are synthesized by simply tuning the reaction parameters, including sodium fluoride content, reaction temperature and reaction time. Under excitation with a 980 nm laser diode, intense ultraviolet (UV) and blue upconversion emissions were achieved from a single dopant ion (Tm3+) in NaYbF4. The effect of the crystal phase on the upconversion emission properties is also investigated. The results demonstrate that upconversion emission intensities from hexagonal phase NaYbF4 microtubes are much more efficient than the nanocubes by 2 orders of magnitude. These microtubes with unique upconvertion emissions demonstrate that NaYbF4 is an excellent host material, as compared with some of its other fluoride and oxide counterparts, and that it may find applications in UV and visible solid-state lasers or the fiber lasers.

Spectroscopic properties of Pr 3+:Gd 3Ga 5O 12 crystal

The room-temperature absorption spectrum, fluorescence spectra, and fluorescence decay curves of Pr 3+-doped Gd 3Ga 5O 12 single crystal were studied systematically. The standard and modified Judd–Ofelt theories were used to determine the Judd–Ofelt intensity parameters Ω t ( t = 2, 4, 6), radiative transition probabilities, radiative lifetimes and branching ratios. The stimulated emission cross-sections and the fluorescence quantum efficiency of the promising laser levels were calculated and discussed. The multi-exponential behavior of the fluorescence decay curve of the 1D 2 → 3H 4 transition was explained by using the Inokuti–Hirayama theory. The obtained spectroscopic results show the potential application of the Pr 3+-doped Gd 3Ga 5O 12 crystal as visible solid-state lasers.

Tunable visible solid-state lasers based on intracavity frequency doubling of Cr:forsterite in KTP

Broadband tunability in the yellow-red region is obtained by use of intracavity type II second-harmonic generation of gain-switched Cr:forsterite lasers in KTiOPO(4) . An operating wavelength range of 67 nm, from 587 to 654 nm, is obtained. Second-harmonic energy of almost 1 mJ is achieved at a peak wavelength of 620 nm. A measured factor-of-34 enhancement in acceptance angle is obtained with broadband harmonic generation. Frequency doubling is optimized with respect to the Cr:forsterite pump and laser parameters.

Tunable high-repetition-rate visible solid-state lasers based on intracavity frequency doubling of Cr:forsterite

High-repetition-rate solid-state lasers broadly tunable in the red-orange and infrared spectral regions are reported. Wavelengths between 590 and 670 nm and between 1170 and 1360 nm have been generated by gain-switched Cr:forsterite lasers incorporating intracavity frequency doubling in KTP. Broadband, tuned, and narrow-band systems operating at repetition rates between 1 and 20 kHz have been developed. Maximum visible output power of 40 mW was achieved by frequency doubling of a narrow-band infrared laser, corresponding to a fundamental to second-harmonic conversion efficiency of more than 30%.

Tunable visible solid-state lasers based on second-harmonic generation of LiF:F_2^- in potassium titanyl phosphate

A new broadly tunable visible solid-state laser is reported. Wavelengths between 550 and 610 nm are generated by intracavity frequency doubling of tuned and free-running room-temperature pulsed LiF:F(2)(-) lasers in potassium titanyl phosphate. Second-harmonic energy of 1.3 mJ has been achieved, corresponding to a fundamental-to-second-harmonic conversion efficiency of 20%. Operation is optimized with respect to LiF:F(2)(-) laser parameters.