Solid-state Laser Research Articles

Effect of network modifiers on spectroscopic properties of Sm3+ ions doped gallium silicate glasses

In this work, the glass 42AO-7Nb2O5-21Ga2O3–29SiO2-1Sm2O3(A = Ca,Sr,Ba) are prepared by the conventional melt quenching technique. The effects of modifiers on the glass network structure and luminescence properties were investigated by XRD, Raman spectroscopy, spectrophotometry, and J-O theory, respectively. The J-O intensity parameters which were calculated though the absorption spectra were used to evaluate the laser parameters such as the radiative excursion probability of Sm3+ ions in different samples at each energy level, the emission cross section, the radiative lifetime, and the optical gain parameter. When BaO is used as a network modifier, the emission cross section is maximized at the 4G5/2 → 6H7/2 transition, with σem = 9.47 × 10−22 cm2. The experiments results reveal that altering the network modifier can effectively improves the laser emission performance of the samples, and the Sm3+ ions doped gallium silicate glasses has prospective applications in solid state orange lasers.

Ultra-highly sensitive dual gases detection based on photoacoustic spectroscopy by exploiting a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser.

Photoacoustic spectroscopy (PAS) as a highly sensitive and selective trace gas detection technique has extremely broad application in many fields. However, the laser sources currently used in PAS limit the sensing performance. Compared to diode laser and quantum cascade laser, the solid-state laser has the merits of high optical power, excellent beam quality, and wide tuning range. Here we present a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser used as light source in a PAS sensor for trace gas detection. The self-built solid-state laser had an emission wavelength of ~2 μm with Tm:YAP crystal as the gain material, with an excellent wavelength and optical power stability as well as a high beam quality. The wide wavelength tuning range of 9.44 nm covers the absorption spectra of water and ammonia, with a maximum optical power of ~130 mW, allowing dual gas detection with a single laser source. The solid-state laser was used as light source in three different photoacoustic detection techniques: standard PAS with microphone, and external- and intra-cavity quartz-enhanced photoacoustic spectroscopy (QEPAS), proving that solid-state laser is an attractive excitation source in photoacoustic spectroscopy.

Synthesis and upconversion luminescence properties of Ho3+-Yb3+ co-doped glass ceramics containing LiGd(WO4)2

Ho3+-Yb3+ co-doped glass ceramics containing LiGd(WO4)2 were prepared by melt crystallization method. By using the methods of differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmittance, and scanning electron microscopy (SEM), the optimal heat treatment condition for the samples was identified to be 580 °C/140 min. In these conditions, the transmittance of glass ceramic is about 75 % in the 380–780 nm range. In the upconversion emission spectra, strong green emission (543 nm) and red emission (650 nm) due to 5F4/5S2, 5F5→5I8 transitions are observed at 980 nm excitation. Additionally, the optimum doping concentrations of Ho3+ and Yb3+ were 0.12 % and 0.4 %. The crystal field changes around dopant ions were analyzed using J-O theory and Eu3+ probe to explain the up-conversion luminescence enhancement of glass ceramics containing LiGd(WO4)2. The chrominance coordinates of 0.12 % Ho3+-0.4 % Yb3+ co-doped glass ceramics are located in the green light region, and the color purity is 95.6 %. In summary, Ho3+-Yb3+ co-doped transparent glass ceramics containing LiGd(WO4)2 have potential applications in infrared detection and green solid-state lasers.

Enhancing interfacial bond strength between PEEK and inkjet-printed silver film through laser surface modification for additive manufacturing of electronics

Electronic 3D printing is a very promising technology, which is widely used in the manufacturing of conformal antennas, flexible electronics and sensors. Polyether ether ketone (PEEK) is one of the most popular substrate materials for electronic 3D printing due to its superior fatigue resistance, heat tolerance, chemical resistance, and mechanical properties. However, the deficient bond between the PEEK substrate and the conductive ink leads to the peeling and shedding of the conductive pattern. This paper investigated the enhancement of the bond strength between the PEEK substrate and the conductive layer through PEEK surface modification. A 355 nm ns solid-state laser was used to treat the PEEK surface with different values of laser scanning spacing (S) and spot overlap rate (R). The surface microstructure, surface roughness, wettability, and functional groups of the treated substrates have been measured. Then the nanoparticle silver ink was printed and cured on the treated substrate. After that, the bonding strength was measured using a pull-off adhesion tester. Results showed that regular grooves were generated and the content of active oxygen atoms was increased on the PEEK surface through laser modification. The mechanical interlocking between the grooves and silver particles and hydrogen bonds induced by the active oxygen atoms and the hydroxyl groups contribute to the enhancement of bond strength between PEEK and silver film. The bond strength for the laser treated PEEK reached the maximum of 1.9 MPa, which was 413.51% higher than that of the untreated PEEK. The laser modification can effectively enhance the interfacial bond strength for additive manufacturing of reliable electronics.

Spectroscopic studies of Eu doped CaF2 single crystal

The Eu-doped CaF2 crystal is investigated for potential use in visible-region solid-state lasers. The single-crystal Eu: CaF2 has an FCC crystal structure and belongs to the space group Fm-3 m, as confirmed by single-crystal X-ray diffraction. A Raman shift of 324 cm−1 has been observed in a single crystal of Eu: CaF2. The vibrational mode at low frequency is suitable for minimizing non-radiative emissions and increasing radiative emissions. Eu: CaF2 crystal has two absorption bands, at 399 nm and 415 nm, corresponding to the 7F0→5L6 and 7F0→5D3 transitions, respectively. The strongest absorption peak (399 nm) is associated with the 7F0→5L6 electronic transition. The orange-red emission was observed at 588 nm (5D0→7F1), 612 nm (5D0→7F2), 648 (5D0→7F3), and 685(5D0→7F4) when excited at 399 nm. Measurements of the luminescence intensity ratio (R) between the 5D0→7F2 (electric dipole) transition and the 5D0→7F1 (magnetic dipole) transition predict that Eu3+ ions are situated at the symmetric sites in CaF2. The radiative parameters for the Eu: CaF2 crystal are calculated using the JOES code using the Judd-Ofelt theory. The calculated total radiative transition probability (AR) is 64.54 s−1, and the radiative lifetime (τR) is 15.57 ms. Radiative transition probabilities are 43.41,7.02 and 14.10, and branching ratios are 67.26 %,10.88 % and 21.85 % for 5D0→7F1, 5D0→7F25D0→7F4 transitions respectively.

The frequency degeneracy range of transverse mode in an off-axis end-pumped solid-state lasers

The frequency degeneracy range of transverse mode in an off-axis end-pumped solid-state lasers

Shape-Dependent Optical Waveguides and Low-Threshold Lasers from Polymorphic Two-Dimensional Organic Single Crystals.

Organic single crystals (OSCs) with uniform morphologies and highly ordered molecular aggregations are promising for high-performance optoelectronic devices, such as organic solid-state lasers (OSSLs), organic light-emitting transistors (OLETs), and organic light-emitting diodes (OLEDs). However, manipulating OSC morphologies and aggregation is challenging. In this study, we synthesized two-dimensional (2D) OSCs of 4,4'-bis[(N-carbazole)styryl]biphenyl (BSBCz) in hexagonal and parallelogram microplate (H-MP and P-MP) forms. Both types exhibit H-aggregation in the 2D plate plane but with different molecular transition dipole moment (TDM) orientations. This leads to different photon coupling modes with H-MP and P-MP microcavities. H-MPs enable isotropic 2D-waveguiding, forming whispering gallery mode (WGM) resonators, while P-MPs create unidirectional waveguiding, forming Fabry-Pérot mode (FP) resonators. These resonators can generate low-threshold laser emissions at 467 and 473 nm, respectively, and exhibit superior lasing stability with a half-life exceeding 2 h. Our BSBCz microplate OSCs are attractive candidates to combine controlled organic microcavities with photon transporting for realizing future integrated optoelectronic devices.

Ultrasonic attenuation with relaxation at low temperatures of Nd3+ doped phosphate glasses for potential solid-state laser applications

The glass set, with varying compositions of (1-x) (0.659 P2O5, 0.095 ZnO, and 0.244 PbO), was used to investigate longitudinal ultrasonic attenuation at different frequencies (2 and 14 MHz) and different temperatures (120 and 300 K). The glass samples contained different mole percentages of Nd2O3, specifically x = 0.00, 0.0046, 0.0092, 0.0138, and 0.0271. Based on the glass construction and switching frequency in well-defined broad absorption curve reaches its highest points at different temperatures. These peaks shifted to higher temperatures, indicating a relaxing mechanism, as the overall frequency increased. A thermally driven relaxation process led to the development of an approach, that the activation mechanism's average energy was mainly influenced by the mole percent content of Nd2O3. The observed diminish of the acoustical energy of activation worth's, quantifiably expressed in terms of the diminished amount of oxygen atoms moving at a double-well potential, that was determined based on the number of loss centers. Such decrease in average activation energy was correlated with the increase in; Bulk elastic modulus, linear expansion coefficient, glass transition temperature and average bond dissociation energy with Nd2O3.

Kerr-lens mode-locking of an Yb:SALLO laser generating 25 fs pulses at 1090 nm

We report on the generation of sub-30 fs pulses from a Kerr-lens mode-locked ytterbium solid-state laser based on a disordered Yb:SrLaAlO4 (Yb:SALLO) crystal as a gain medium. The Yb:SALLO laser, pumped by a spatially single-mode Yb-fiber laser at 979 nm, produces soliton pulses as short as 25 fs at 1090 nm, with an average output power of 149 mW at a pulse repetition rate of ∼80.7 MHz. The power scaling potential of the Kerr-lens mode-locked laser is exploited by achieving watt-level (1.54 W) average output power at 1081 nm for a somewhat longer pulse duration of 34 fs. This result corresponds to an impressive laser efficiency of 49.7% and a peak power of 468 kW.

1 MW Peak‐Power Mamyshev Oscillator Started by a Passively Q‐Switched Microchip Laser

Ultrafast fiber lasers (UFLs) have become an attractive alternative to solid‐state lasers (SSL) due to their excellent beam quality, compactness, environmental stability, and easy thermal management. In the last decade, a significant research effort is spent to identify UFL architectures providing pulse energy, duration, and peak power comparable to those of complex and expensive, Ti:sapphire laser systems and semiconductor saturable absorber mirrors mode‐locked, Yb‐doped SSL. Lately, Mamyshev oscillators (MOs), relying on offset spectral filtering combined with nonlinear spectral broadening by self‐phase modulation, emerge as a promising solution and are rapidly becoming the state of the art for high energy/peak power UFLs based on large‐mode‐area (LMA) fibers. The focus of this work is the first demonstration of starting of the mode‐locking regime in an LMA MO with an affordable passively Q‐switched microchip laser. This solution was previously demonstrated only in low‐power MO based on single‐mode fibers, which are intrinsically easier to seed, if compared to high‐gain LMA UFLs, because of the lower amplified spontaneous emission noise floor. This starting technique in an easy‐to‐implement ring LMA MO at 1 μm is tested. The oscillator provides ≈50 nJ pulses at 12 MHz repetition rate with a minimum pulse duration of ≈50 fs after compression, resulting in MW peak power.

High peak power passively Q-switched Tm:YAP solid-state laser with Cr2+:ZnSe and Cr2+:ZnS saturable absorber

We experimentally demonstrate a passively Q-switched thulium-doped YAlO3 (Tm:YAP) laser based on the Cr2+:ZnSe (Chromium, Zinc Selenide) and Cr2+:ZnS (Zinc Sulfide) crystals. Wavelength tuning for 1.87 μm, 1.90 μm, and 1.94 μm operations was achieved by employing a birefringent plate. The impact of varying doping concentrations of Cr2+:ZnS crystals and a Cr2+:ZnSe crystal on the laser output was investigated. During the analysis, the passively Q-switched Tm:YAP laser achieved a pulse with the highest peak power of 107.5 kW and the narrowest pulse width of ∼6 ns, utilizing a Cr2+:ZnSe crystal as the saturable absorber (SA) with a modulation depth (ΔR) of 14 %.

Multi-mode stable, high peak power Nd:YAG laser device for laser cleaning

High average power and peak power solid-state lasers are of great interest in the field of laser cleaning. In this research, a high peak power laser with over 400 W average power using a multi-mode stable resonator in a diode-pumped Nd:YAG master oscillator power amplifier has been demonstrated. A maximum peak power over 1.08 MW was achieved at a repetition frequency of 5 kHz. Delivery fiber with a 400 µm core diameter was utilized for flexible laser transmission. A prototype of the laser cleaning system was developed and inspiring application effects for paint and mold cleaning were achieved.

In-band pumped Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser

We report on a Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser with in-band pumping of the Tm ions by a spatially single-mode 1678 nm Raman fiber laser. The structurally disordered CaGdAlO4 host crystal is also codoped also with the passive Lu ion for additional inhomogeneous line broadening. The Tm,Ho,Lu:CaGdAlO4 laser generates soliton pulses as short as 79 fs at a central wavelength of 2073.6 nm via soft-aperture Kerr-lens mode-locking. The corresponding average output power amounts to 91 mW at a pulse repetition rate of ∼86 MHz. The average output power can be scaled to 842 mW at the expense of slightly longer pulses of 155 fs at 2045.9 nm, which corresponds to a peak power of ∼58 kW. To the best of our knowledge, this represents the first demonstration of an in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser at ∼2 µm.

Conversion of an industrial LIBS system to double-pulse operation to improve sulphur detection in rubber-based parts

The detection of sulphur as an elementary component of the crosslinking system of rubber compounds is difficult in LIBS single-pulse operation due to the usually low concentration and the poor response behavior of the analyte. However, reliable proof of the distribution quality of sulphur in the compound is a decisive quality criterion for the homogeneity of the crosslinking density achievable during vulcanization, which is important for the uniform performance of an elastomeric article, especially under dynamic load.Therefore a commercially available industrial LIBS system, (1064 nm Nd:YAG solid state laser, 100 mJ, 20 Hz) is extended with a 266 nm laser (Nd:YAG solid state laser, 60 mJ, 20 Hz) to combine an UV-based initial excitation (for ablation efficiency) followed by an IR-pulse (to realize highest plasma heating) to improve sulphur detection in rubber based compounds and parts. Optimization of the system parameters are investigated to improve the ablation efficiency and to increase the measured signal intensity/signal-to-noise-ratio of the analyte. The VUV sulphur lines at 180.658, 181.956, and 182.561 nm and the NIR sulphur lines at 921.298, 922.823, and 923.751 nm are under investigation.

Spectral analysis and dynamic properties of polyurethanes dyed with rhodamine 6G and rhodamine B as matrices of a solid-state laser element

A comparison was carried out of the nature of intermolecular interactions, elastic properties and gas permeability of the crosslinked polyurethanes doped with xanthene dyes and original polyurethane using IR spectroscopy, dynamic mechanical analysis (DMA) and electron paramagnetic resonance (EPR). The introduced dye can be considered as useful microimpurity which, however, can affect the efficiency of the laser. In IR spectra of polyurethanes the complex band of stretching vibrations of C=O groups is sensitive to the nature of intermolecular interaction of urethane groups. From the analysis of that band it is shown that in the presence of dyes, self-association of urethane groups within the hard segment predominates and the interaction of urethane groups with the oligoether component decreases, which can contribute to increasing the mobility of the flexible component. A decrease in the dynamic storage modulus (E’) and a decrease in the glass transition temperature (Tc) of polyurethanes in the presence of dyes is shown by the DMA method. The results of both DMA and IR spectroscopy indicate a greater increase in the mobility of the elastic component with the introduction of the rhodamine B dye, covalently bound to the polyurethane chain. According to nitroxyl paramagnetic probe data the introduction of both rhodamine B and rhodamine 6G dyes into polyurethanes increases their permeability to vapors of low-molecular weight compounds, but rhodamine 6G has a more prominent effect on this characteristic. This is consistent with DMA data indicating a greater increase in the Mc value in the presence of rhodamine 6G in polyurethane. The obtained results make it possible to determine the optimal composition of the active laser medium and are important in assessing the radiation resistance of the polymer matrix. Its increase is facilitated by a decrease in the storage modulus and an increase in the gas permeability of the polymer, leading to a decrease in pressure in the area of local heating.

Thulium or holmium laser or both: where will the journey take us?

The Holmium:YAG laser has been the gold standard for laser lithotripsy over the past three decades and, since the late 1990s, also for prostate enucleation. Pulsed thulium fibre lasers (TFL) demonstrated their efficacy in in-vitro experiments and were introduced to the market a few years ago. Initial clinical results for TFL in lithotripsy and enucleation are very promising. In addition to TFL, a pulsed Thulium:YAG solid-state laser has been introduced, but clinical data for this laser are currently limited. This article aims to review the key technological differences between Ho:YAG lasers and pulsed thulium lasers and compare/discuss the initial clinical results for stone lithotripsy and laser enucleation.In-vitro studies have demonstrated the technical superiority of TFL compared with Ho:YAG lasers. However, as TFL is still a new technology, only limited studies are available to date, and optimal settings for lithotripsy have not been established. For enucleation, the differences of TFL compared with a high-power Ho:YAG laser seem to be clinically irrelevant. Initial studies on pulsed Tm:YAG lasers show good results, but there continues to be a lack of comparative studies.Based on the current literature, pulsed thulium lasers have the potential of being an alternative to Ho:YAG lasers. However, further studies are necessary to determine the optimal laser technology for enucleation and lithotripsy of urinary stones, considering all parameters, including efficacy, safety, and cost.

Terawatt-class femtosecond long-wave infrared laser

We utilized a nonlinear post-compression technique to generate 675-fs, 9.2-μm CO2 laser pulses with a peak power of 1.6 TW. This achievement represents the highest peak power ever attained in the femtosecond pulse format within the long-wave infrared (LWIR) spectral range. The successful implementation of this post-compression technique opens avenues for the development of few-cycle, multi-terawatt 9–10 μm lasers, crucial for applications currently relying on near-infrared solid-state lasers, and which stand to benefit from the scaling of laser wavelengths into the long-wave infrared region.

High-power, gigahertz repetition frequency self-mode-locked Ho:GdVO4 laser resonantly pumped by a Tm-doped fiber laser.

A self-mode-locked Ho:GdVO4 laser with the GHz pulse repetition frequency oscillation near 2.06 µm was demonstrated for the first time to our knowledge. The output performances of the self-mode-locked Ho:GdVO4 laser were investigated for a few output coupler transmittances at the pulse repetition frequency of 1.89 GHz. At the incident pump power of 8.12 W, the maximum average output power was as high as 2.28 W, corresponding to the slope efficiency and optical-to-optical efficiency of 36.3% and 28.1%, respectively. This is the maximum average output for the 2 µm self-mode-locked solid-state laser with a GHz pulse repetition frequency. This work provides a new way for generating an efficient and a high-power ultrafast pulse laser with a GHz repetition frequency in the 2 µm wave band.

Research status of rare-earth-ion-doped infrared laser

Infrared lasers have an extensive range of applications in sensing, detection, communication, medicine, and other fields. The principle of directly pumping solid-state lasers is simple, and it can easily achieve high-power and high-efficiency laser output, which is one of the important means to obtain infrared lasers. Incorporating rare earth ions into the substrate as the gain medium for directly pumping solid-state lasers can alter their optical performance and further enhance the performance of the laser. Lasers based on rare earth ion doping have a small volume, high conversion efficiency, good beam quality, wide tuning range, and multiple operating modes. Therefore, the proportion of rare earth ions doped as the gain medium for activating ions is currently very large. In this review, Ho3+, Tm3+, and Er3+ are selected as the representative rare earth ions, and their optical properties, such as luminous power and fluorescence lifetime, when doped in different substrates, such as crystals, ceramics, and fibers, are introduced, respectively, to illustrate their feasibility as infrared laser gain media. In addition, we show the different optical properties when doped with two ions, three ions, and four ions, demonstrating their great potential as infrared laser gain media.

High-power 2.3 µm Tm:YLF laser with intracavity upconversion pumping by a Nd:ASL laser at 1051 nm.

A Tm:LiYF4 laser operating on the 3H4 → 3H5 transition is embedded in a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 µm. This leads to a record-high output power at 2.3 µm for any bulk thulium laser pumped by an upconversion process. The continuous-wave Tm:LiYF4 laser delivers 1.81 W at 2.3 µm for 32 W of laser-diode pump power, making this kind of pumping competitive with direct diode pumping. The intracavity pumping process allows for counteracting the low absorption inherent to upconversion pumping and to dispatch the thermal loads on two separate laser crystals. The proposed laser architecture also features a relatively weak heating of the Tm:LiYF4 crystal and an increased tolerance to Tm3+ absorption. This laser design opens a new paradigm that holds great promise for high-power 2.3-µm solid-state lasers based on thulium ions.