Solid-state Laser Research Articles

Quantitatively Deciphering the Local Structure and Luminescence Spectroscopy of Pr3+-Doped Yttrium Lithium Fluoride.

Praseodymium (Pr3+)-doped LiYF4 nanophosphors have garnered significant interest for their potential applications in lasers, phosphors, and quantum memories. However, there remains a lack of comprehensive research on the local coordination environment and luminescence spectroscopy of Pr3+:LiYF4 nanocrystals. This study presents the first investigation of the ground-state structure of Pr3+:LiYF4 crystals by employing the crystal structure prediction method, and a [PrF8]5- ligand complex with S4 local symmetry is determined. The complete energy levels of the Pr3+ ions in LiYF4 nanocrystals are unveiled by using our newly developed well-established parametrization matrix diagonalization method. A novel set of free-ion and crystal-field parameters is derived through a good simulation with 45 experimental energy levels. Many of the emissions of Pr3+-doped LiYF4 are successfully reproduced based on Judd-Ofelt theory, and these transitions are comparable to the experimental ones. Moreover, two new prominent emission bands with their peaks at 675 and 849 nm originating from 1I6 → 3F4 and 1I6 → 1G4 transitions, respectively, are predicted by us for the first time. This study could provide a feasible method to search for practical laser transition channels of solid-state lasers based on Pr3+: LiYF4 nanophosphors.

Advances in and Future Perspectives on High-Power Ceramic Lasers

Advancements in laser glass compositions and manufacturing techniques has allowed the development of a new category of high-energy and high-power laser systems which are being used in various applications, such as for fundamental research, material processing and inertial confinement fusion (ICF) technologies research. A ceramic laser is a remarkable revolution in solid state lasers. It exhibits crystalline properties, high yields, better thermal conductivity, a uniformly broadened emission cross-section, and a higher mechanical constant. Polycrystalline ceramic lasers combine the properties of glasses and crystals, which offer the unique advantages of high thermal stability, excellent optical transparency, and the ability to incorporate active laser ions homogeneously. They are less expensive and have a similar fabrication process to glass lasers. Recent developments in these classes of lasers have led to improvements in their efficiency, beam quality, and wavelength versatility, making them suitable for a broad range of applications, such as scientific research requiring ultra-fast laser pulses, medical procedures like laser surgery and high-precision cutting and welding in industrial manufacturing. The future of ceramic lasers looks promising, with ongoing research focused on enhancing their performance, developing new doping materials and expanding their functional wavelengths. The ongoing progress in high-power ceramic lasers is continuously expanding the limits of laser technology, therefore allowing the development of more powerful and efficient systems for a wide range of advanced and complex applications. In this paper, we review the advances, limitations and future perspectives of ceramic lasers.

Growth and spectroscopic properties of Dy3+:GdCa4O(BO3)3 crystals

8 at.%, 10 at.%, and 12 at.% Dy3+ ions doped GdCa4O(BO3)3 crystals were successfully grown by the Czochralski method. The Raman spectrum showed that the maximum phonon energy was 937 cm−1. Detailed investigation of polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curve of the Dy3+:GCOB crystals showed that all the three crystals had good spectral properties. The strong and wide absorption peaks at 454 nm indicated that the crystals were fit for commercially available blue InGaN LD pumping. The intense and broad emission bands at around 585 nm, and long fluorescence lifetimes, revealed that the Dy3+:GCOB crystals were potential solid-state laser materials for yellow laser.

High-power and ultra-wide-tunable fiber-type external-cavity diode lasers

High-power and wide-tunable fiber-type external-cavity diode lasers (FTECDLs) are of pivotal importance across various scientific and practical applications, such as polarization lidar, communication, sensing, and spectroscopy. As the output power and tuning characteristics are currently much lower than the saturation power and bandwidth of semiconductor gain media, further improvements conventionally require additional gain media in parallel and external amplifiers, resulting in lower energy efficiency and complex configurations. This study implemented energy manipulation in FTECDLs with a single gain medium, overcoming the mutual restriction between low damage threshold and laser output power. This approach makes it possible to completely exploit the intrinsic performance of the semiconductor gain medium. We demonstrated various FTECDL designs, achieving a maximum tuning range of 226.8 nm, maximum output power of 160 mW, and maximum optical signal-to-noise ratio of 86.3 dB with different configurations. These results are the highest levels ever achieved for E, S, C, L, and U bands. Additionally, the achieved polarization extinction ratio of nearly 38 dB has not been previously reported. Our work provides significant guidance for the design of traveling wave ring cavity (TWRC) lasers, including free-space light semiconductor and solid-state lasers with a TWRC.

First fluoride ceramics lasing at 605 nm at ambient temperature fabricated from chemically synthesized powders

Laser ceramics have emerged as promising candidates of solid-state laser gain media. However, most laser ceramics are currently focused on lasing in the infrared wavelength range. The very limited options of host materials and the increased optical scattering losses at shorter wavelengths within ceramics have greatly limited the development of visible laser ceramics. Here we report visible laser ceramics with a composition of 0.5%Pr3+,5%Y3+:SrF2, in which a visible (orange) laser oscillation at 605 nm has been successfully achieved at room temperature pumped by InGaN blue laser diodes with a maximum slope efficiency of 8.1%. The ceramics were fabricated by vacuum hot pressing (VHP) of wet-chemistry synthesized 0.5%Pr3+,5%Y3+:SrF2 powders, followed by hot isostatic pressing (HIP). It was found that the visible laser ceramics exhibited a lower optical scattering loss along the processing pressure direction of the VHP process, indicating a uniaxial anisotropy in optical transmission within the ceramics. To our best knowledge, the current work is the first report on visible laser ceramics lasing in the orange region at ambient temperature, fabricated from chemically synthesized powders, which could pave the way for future scientific research on and industrial applications of more sophisticated and cost-effective visible laser ceramics.

Development and characterization of novel Fe2+:ZnSexS1-x solid solution laser ceramics for mid-infrared laser application

In this study, Fe2+:ZnSexS1-x (0.6 ≤ x ≤ 1) solid solution laser ceramics with cubic crystal structures were prepared for the first time via hot pressing sintering, using FeSe, ZnSe, and ZnS powders. The resulting ceramics exhibit a unique combination of the optical and physical properties of Fe2+:ZnSe and Fe2+:ZnS. An increase in the ZnS content led to a blueshift in the maximum absorption spectra of Fe2+ ions and an enhancement in Vickers hardness. These findings suggest that Fe2+:ZnSexS1-x solid solution ceramics could serve as promising gain media for mid-infrared solid-state lasers, offering a novel approach for the development of directly pumped mid-infrared laser systems.

Optimized-selenization preparation and laser Q-switching characteristics of layered PtSe2

Abstract PtSe2 has high carrier mobility, excellent electrical and optical properties, and high potential in the field of optoelectronic devices. In this paper, the conventional selenization method is optimized and a single-temperature zone preparation is used to prepare large-area and homogeneous PtSe2 thin-film materials on sapphire substrates in a shorter time and at a lower temperature. The prepared sample is characterized by optical microscopy, atomic force microscopy, Raman spectroscopy and Z-scan method. The saturable absorption properties of layered PtSe2 as a passive Q-switched are investigated in a solid-state laser. The results show that the PtSe2 thin film material is synthesized at 400 °C for 1 h to cover the entire one-inch sapphire wafer with a thickness of about 25 nm and the surface roughness is 13.1 nm. The modulation at 1064 nm yielded an output pulse with a maximum repetition frequency of 688.47 kHz, corresponding to a pulse width of 202.5 ns, a peak power of 7.35 W, a single-pulse energy of 1.51 μJ, and a stable pulse train.

Engineering the meta-phosphate BaO–Al2O3–P2O5 glass network for high average power (HAP) laser applications: Systematic composition modifications and SiO2 integration

The metaphosphate glasses are the preferred gain media for high-power solid-state laser applications. In the context of solid-state glass lasers, the main challenge to attain high average power (HAP) is to govern excessive thermal loading during operation. This work focuses on addressing thermal loading issues through improving thermal and mechanical properties of the meta-phosphate BaO–Al2O3–P2O5 laser glass system by engineering its molecular structure through systematic composition modifications with SiO2 incorporation. FTIR, Raman and 27Al MAS-NMR spectroscopy indicate stronger P–O–P bridges with decreasing glass basicity and increasing [AlO4] formations beyond 12.5 mol% Al2O3. The O/P ratio increases from 3.05 to 3.43 with up to 20 mol% SiO2 in Series-A and from 3.13 to 3.49 with up to 15 mol% SiO2 in Series-B, altering the Al coordination number from 6 to 4 to maintain the glass network charge balance. Increased [AlO4] formation raises Young's modulus from 61 GPa to 73 GPa and decreases Poisson's ratio from 0.30 to 0.24. These changes enhance fracture toughness and reduce CTE. Further, SiO2 inclusion enhances thermal conductivity by increasing glass network compactness and rigidity. These modifications highlight the improved thermo-mechanical properties of the SiO2-modified Series-B glasses. Yb3+ emission cross-section rises from 0.495 × 10−20 cm2 in ABSP-A1 glass to 0.502 × 10−20 cm2 in ABSP-B1 with increased [AlO4] formation. More AlPO4-like units in ABSP-B1 increase average glass phonon energy, reducing Yb3+ fluorescence lifetime from 1062 μs to 945 μs, whereas SiO2 addition boosts Yb3+ fluorescence lifetime again. Lower OH− content further extends Yb3+ fluorescence lifetime in Series-B glasses with higher SiO2 content. This study underscores the intricate relationship between glass molecular structure and thermal, mechanical, and spectroscopic properties, advancing high-power silico-phosphate laser glass development.

Growth, first-principles calculations and optical properties of a novel near-infrared Ho: NLGW laser crystal

A rigid structure was constructed using an isotopic doping strategy, and a novel near-infrared 1 at% Ho3+: NaLa0.93Gd0.06(WO4)2 (Ho: NLGW) laser crystal with a size of Φ 18 mm × 30 mm was successfully grown by the Czochralski method. X-ray rocking curves and Rietveld refinement indicate that the grown crystal possesses high crystalline quality and crystallizes in the I41/a space group with lattice parameters: a = b = 5.3518 Å, c = 11.6438 Å and V = 333.5051 Å3. The Ho: NLGW crystal exhibits a low coefficient of thermal expansion (8.472 × 10−6 K−1), and the c-axis thermal conductivity increases from 1.235 W/(m × K) to 1.404 W/(m × K). The thermal properties of the Ho: NLGW crystal surpass those of other Ho3+-doped tungstate series and mainstream near-infrared laser crystals, suggesting that it is easier to obtain excellent laser gain. For revealing the excellent thermal properties, the elastic moduli of the NLW and NLGW crystals have been calculated by first principles. With the introduction of Gd3+, the structural stiffness of the NLW as a whole has been increased to optimize the mechanical properties in each axial direction and to obtain the reason for the larger Debye temperature. Finally, the transmission, absorption and near-infrared emission spectra of the Ho: NLGW crystal were investigated. The crystal exhibits a high transmittance of 88.5 % and an emission cross-section of 0.84 × 10−20 cm2 calculated according to the J-O theory. Experimental results indicate that the grown Ho: NLGW crystal can achieve large laser output more easily and are expected to be an excellent medium for 2 μm solid-state lasers.

X-ray diffraction, luminescence, and electron paramagnetic resonance study of LaLuO3:Yb3+ nanopowders

The primary objective of materials science is the study of the properties of the existing materials and the development of new ones. In the present day, the use of solid-state lasers abroad has prompted material scientists globally to develop novel or enhance the properties of the existing active gain media. Materials comprising rare earth elements have historically proven effective in scintillation applications. The synthesis of LaLu1-xYbxO3 monodisperse nanopowders with a particle size of 50–62 nm via the Pechini complexing citrate method has been the subject of investigation using electron paramagnetic resonance (EPR) spectroscopy and photoluminescence (PL) measurements. The EPR data indicate that the Yb³⁺ ions predominantly create a single type of center, whereby the Yb³⁺ ion substitutes for the Lu³⁺ ion. The calculated EPR g-factors are estimated to be g1 = 3.85, g2 = 2.15, g3 = 1.55 and the 171Yb isotope hyperfine interaction constants are A1 = 600 × 10−4 cm−1, A2 = 700 × 10−4 cm−1, A3 ≈ 1800 × 10−4 cm−1. The principal values of the g factors and the hyperfine tensors indicate that the Yb site in LaLu1-xYbxO3 nanopowders exhibits orthorhombic symmetry. The PL measurements in the wavelength range of 350–1800 nm, with excitation provided by either a xenon lamp or a diode laser, indicate the presence of a broad emission band, centered at 404 nm, in addition to the well-known emission spectrum in the IR region (920–1100 nm) arising from Yb3+ ions.

Luminescence performance, temperature sensing characteristics and Judd-Ofelt theory analysis of Y2MoO6:Er3+/Yb3+/Li+ upconversion phosphors

A series of Y2MoO6:0.01Er3+/0.09Yb3+ upconversion phosphors doped with different concentrations of Li+ ions (0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 mol) were prepared by the high temperature solid phase reaction method, and their physical phase structures and upconversion luminescence were analyzed. At the excitation wavelength of 980 nm, the addition of Li+ sharply increased the upconversion luminescence intensity. With the increase of Li+ ion content, the luminescence intensity first increases and then decreases. When the doping amount reaches 0.25 mol, the luminescence intensity reaches the maximum, and the sample emits green light in the two-photon process. Y2MoO6:0.01Er3+/0.09Yb3+/0.25Li+ exhibits excellent temperature sensing properties. Its absolute sensitivity Sa reaches up to 0.012 K-1, the relative sensitivity Sr is 0.017 K-1 and the measurement error δT is less than 0.3 K at room temperature. Its temperature sensing performance is far superior to similar materials. In addition, Judd-Ofelt theory calculations revealed that in comparison with Y2MoO6:0.01Er3+/0.09Yb3+, its Ω2 increased from 0.56×10-20 cm2 to 3.68×10-20 cm2 , and the spectroscopic quality factor Ω4/Ω6 ratio reached 4.09, which is much higher than that of the other fluorescent materials. The main reason is that Li+ replaces the Y3+ ion lattice site, causing lattice distortion and reducing the lattice symmetry around the active ion. The increase in asymmetry increases the possibility of spontaneous radiative transitions. It is shown that the prepared upconversion luminescent materials have potential applications in the field of solid-state lasers and optical sensing.

Optical Limiting Methods by Z-Scan Technique for Non-Linear Optical Absorption of PVC/TiO2 Nanocomposite

To further our grasp of photonics technology, our work focuses on thin-film PVC/TiO2 nanocomposites. Nanocomposites composites were created by combining TiO2 nanoparticles with Polyvinyl Chloride (PVC) as the polymer matrix. The thin film was fabricated using the casting method. Spectral analysis was used to determine the absorbance parameters and compute the linear absorption coefficient. The nonlinear refractive index and nonlinear absorption coefficient were measured using a single beam Z-scan approach with a CW diode pumped solid state (DPSS) laser (Coherent Verdi-V5, 532 nm) acting as the excitation laser at 50mW. Peak absorption was measured at 280 nm, and as the percentage of TiO2 nanoparticles grew, more absorption was seen. The nonlinear absorption coefficient was determined to be 1x10−5 cm/W at (0.5342, 1.3585, 1.5999, and 0.0253). The poor structure arising from all of the sample morphologies affects the materials' NLO absorption. Nonetheless, they seem like good options for optical limiting applications given the positive value of NLO absorption.

Effect of 532nm and 589nm Diode-Pumped Solid-State (DPSS) Lasers with Different Doses on Concentration of Total Protein and Albumin in Vitro.

To test the effects of Low-level laser irradiation at 532nm and 589nm with different doses and exposure times on total protein and albumin in blood plasma. This experimental study was conducted from November 2021 to April 2022 at Mustansiriyah University, Baghdad, Iraq, and comprised blood samples from healthy adults. The samples were stored in tubes containing anticoagulant ethylenediaminetetraacetic acid. Photoradiation was managed using green laser 532nm and yellow laser 589nm diode-pumped solid-state lasers with different doses. For total protein test and albumin test, each sample was divided into 3 equal aliquots. The first was control without radiation, the second was irradiated by a laser at 532nm, and the third was irradiated at 589nm with 30J/cm², 50J/cm², 70J/cm² and 90 J/cm² doses of irradiation. All samples were examined by using a spectrophotometer device. Data was analysed using SPSS 25. There were 24 samples from healthy adults in all.The most significant difference in total protein concentration occurred at dose 70J/cm² for both wavelengths compared to the controls (p<0.05). When this optimal dose was applied to the albumin test, a clear decrease in the albumin concentration was found for both 532nm and 589nm lasers (p<0.05). At wavelengths of 532nm and 589nm, the laser light induced processes that caused a reduction in total protein and albumin.

In vitro comparison of low-power diode pumping solid-state laser radiation at 589 and 650 nm on red blood cells suspension viscosity, stability, and deformability.

To investigate the effect of diode-pumped solid-state laser irradiation with yellow 589nm and red 650nm wavelengths on rheological parameters in vitro. The comparative study was conducted between November 2021 and April 2022 at the at the Postgraduate Medical Physics Laboratory, Mustansiriyah University, Baghdad, Iraq, and comprised blood samples from healthy adult volunteers. The samples were divided into 4 aliquots. The first was preserved as a control sample, while the other 3 were exposed to a diode-pumped solid-state laser, delivering the beam for 589nm and 650nm wavelengths at radiation dose 15, 22.5, 33.5J/cm2 for 20, 30 and 45 minutes, and with each laser having a 50mW output power and a 4 mm2 spot diameter. Data was analysed using SPSS (version 24). There were 6 subjects aged 18-60 years. There was no significant difference in the viscosity values between laser wavelengths (p>0.05). Compared to the laser wavelength of 650nm, irradiation with a 589nm wavelength at the same dose resulted in a significant reduction (p<0.009) in deformability. The rigidity index of red blood cell suspension was reduced the most at a radiation dose of 22.5J/cm2 for both lasers compared to the control samples. No significant variations were found in suspended erythrocyte viscosity (p>0.05). The wavelength with 589nm lasers showed more effective influence than its 650nm counterpart in improving the rheological parameters of blood viscosity and erythrocytes deformability.

A comparison study of 589 and 650 nm on improving stored whole blood stability by irradiation with a low-power diode pumping solid-state laser.

To assess the effects of diode-pumped solid-state laser irradiation with 589nm and 650nm wavelengths on the stability of stored red blood cells in vitro. This is an intervention study that was conducted from April to July 2021 at the Physiology and Medical Physics Laboratory, College of Medicine, Mustansiriyah University, Baghdad, Iraq, and comprised samples of healthy, adult human blood that were put in tubes with citrate-phosphate dextrose-adenine as an anticoagulant. The blood sample was divided into eight equal aliquots and stored for 21 days at 4ºC. The stability test was done on days 0, 7, 14 and 21 of storage time for non-irradiated and radiated aliquots. For 15 minutes, the irradiated aliquots were subjected to a diode-pumped solid-state laser with a wavelength of 589nm or a laser with a wavelength of 650nm at frequencies of 30, 50 and 70 J/cm². Data was analysed using SPSS 24. Exposure of the whole blood to 589nm and a radiation dose of 70J/cm², 50J/cm² and 30J/cm² was associated with a significant reduction in the percentage of haemolysis that ranged 23-42% throughout the whole storage time. Exposure of the whole blood to 650nm wavelength low-level laser therapy and a radiation dose of 70J/cm², 50J/cm² and 30J/cm² was associated with much less reduction in the percentage of haemolysis that ranged 5-9% throughout the whole storage time. Both 589nm and to some extent 650nm low-level laser irradiation generally reduced haemolysis. The wavelength of 589nm lasers had a more effective influence than the 650nm counterpart in improving the stored red blood cells.

Effect of diode pumping solid state laser with wavelength 589 nm on gene expression of interlukine-2 and interferon-γ in human T-lymphocytes.

To evaluate the impact of laser irradiation of human T-cell lymphocyte in culture to determine the photobiomodulatory effects of such irradiation on gene expression, and the release of growth factors and cytokines. The experimental study was conducted from November 2021 to April 2022 at the Postgraduate Anatomy Laboratory, Mustansiriyah University, Baghdad, Iraq, and comprised human blood samples T-cell lymphocytes were extracted and irradiated, followed by the extraction of ribonucleic acid to assess the effect of laser on gene expression of cytokines, interlukine-2 and interferon-gamma. A 589nm yellow light low-level laser beam from a diode pumping solid state laser was used at doses 30J/cm2, 50J/cm2 and 70J/cm2 for an exposure time of 15 minutes. Reverse transcriptase-polymerase chain reaction was used to measure gene expression. Data was analysed using GraphPad Prism 9. Cellular gene expression of the mediators changed significantly in response to laser irradiation at a variety of dosage parameters, and these effects depended on the wavelength and radiation exposure (p<0.05). The laser light may photobiomodulate the production of cytokines by human cells in vitro.

The effect of a diode-pumped solid-state laser with a wavelength of 589 nm on T-lymphocyte proliferation.

To assess how low-level laser irradiation affects T cells. The case-control interventional study was conducted from November 2021 to April 2022 after approval by the ethics review committee of the College of Medicine, Mustansiriyah University, Baghdad, Iraq, and comprised healthy individuals. Phlebotomy was used to collect 4ml of blood. A portion of each sample was exposed to 589nm laser radiation, while the other portion was used as a control. The irradiated sample was divided into whole blood and in-plate subgroups. Phytohemagglutinin was used for mitotic stimulation of T-lymphocytes, and cell proliferation assay was used to stimulate T lymphocytes measured using MTS assay (3-(4,5-dimethylthiazol-2-yl)-5- (3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium). Optical density was measured using enzyme-linked immunosorbent assay. Data was analysed using GraphPad prism software. There were 35 subjects, 17(49%) males and 18 (51%) females, with an age range between 19-25 years, all without any disease or medication. Laser irradiation stimulated T-lymphocyte proliferation to levels that depended on the dose of laser used. At energy 30J/cm2 there was a significant increase in the in-plate subgroup of irradiated samples compared to controls and between the two irradiated subgroups (p<0.05). At 50J/cm2 dose, there was a significant increase in the whole blood subgroup compared to the controls (p<0.05). At 70J/cm2 dose, there was a significant difference in the whole blood subgroup compared to the controls, and between the two irradiated subgroups (p<0.05). The stimulation of T lymphocyte proliferation by the application of a 589nm laser could have medical applications in the field of immune system enhancement.

Synthesis of MnO@Fe2O3 core-shell doped PVA/PVP polymeric nanocomposites for electronic and optoelectronic devices: Mechanical, electrical, and optical properties

Abstract The aqueous solution cast method was utilized to create biodegradable nanocomposite of polymers (PNC) films from a poly (vinyl alcohol) / poly (vinyl pyrrolidone) blend (70/30 wt%) and MnO@Fe2O3 nFs. The dislocation density, particle size, and interplanar distance were all calculated. The PNC films' surface shape changes from smooth to porous and somewhat rough because of the nanosized MnO@Fe2O3 particles' dispersion in the blend matrix, which diminishes the blended crystallites' size. The composite film's tensile strength increased from 9.45 MPa for the pure (PVA-PVP) film to 22.35 MPa due to the addition of 6 wt% MnO@ Fe2O3. The optical band gap decreases from 5.26 and 4.84 eV for pure (PVA/PVP) blend direct and indirect energy band gap to 5.18 and 4.71 eV for comparable values of 6wt% MnO@Fe2O3 nFs. Up to 6 wt% MnO@Fe2O3 concentration, PNC films' dielectric permittivity first declines, but it is substantially identical to the pure polymer blend matrix. The PNC sheet's dielectric permittivity increases nonlinearly with temperature, although its DC conductivity follows the Arrhenius law. Laser power was attenuated by (PVA- PVP)/MnO@Fe2O3 for both He-Ne and solid-state green laser beams. When the MnO@Fe2O3 concentration in the blend matrix rises to 6 wt%, the output power for lasers with 532 nm and 650 nm wavelengths drops from 5.49 to 2.4 mW and 19.8 to 9.4 mW, respectively. The findings suggest that nanocomposites exist and are widely recommended for optoelectronics, microelectronics, radiation detection, and several other uses.&amp;#xD;

Boosting Stimulated Emission via a Hydrogen-Bonded Co-Crystallization Approach in Molecular Crystals.

Stimulated emission of organic π-conjugated molecule in solid state remains a significant challenge, mainly involving the mode of molecular stacking that invariably alters the photo-physical processes. Herein, we successfully realized the stimulated emission in molecular crystals using a hydrogen-bonded co-crystallization strategy. Two hydrogen-bonded co-crystals, obtained from 1,4-bis-p-cyanostyrylbenzene (CNDSB) and two types of co-formers, can boost stimulated emission and show decent amplified spontaneous emission (ASE), whereas the parent CNDSB crystal is not SE-active. Crystal structural analysis demonstrated that the co-crystallization eliminated excimerformation. The resulting higher kr and shorter excited-lifetime led to a larger stimulated-emission cross section, which benefited to the occurrence of ASE. Simultaneously, the uniaxial arrangements along long axis of co-crystal together contributed to highly polarized emission. This system presentsvery rare evidence of boosting stimulated emission by binary co-crystallization, whichenriches our insights into organic solid-state lasers.

Pushing the tuning limits of femtosecond Yb-based solid-state lasers to 1 µm: a Yb:YVO4 laser tunable down to 1004 nm.

We have obtained what we believe to be the shortest fs tuning wavelength (1004 nm) from a Yb-based solid-state laser system. As the working horse, we have chosen Yb:YVO4 due to its blueshifted gain spectrum. While using a single 10 W 952 nm diode for pumping and a semiconductor saturable absorber mirror (SESAM) for mode-locking, we have achieved 266 fs long pulses with up to 1.24 W of output power around 1021 nm. Using an intracavity birefringent filter, the central wavelength of the fs pulses could be tuned smoothly between 1004-1038 nm and 1009-1061 nm while employing the E//a and E//c axis of the material, respectively. By using an additional hard aperture to increase the modulation depth, we have also attained 100 fs level pulses in the 1012.5-1019 nm range, which shows the suitability of the system in seeding cryogenic Yb:YLF-based amplifiers.