Vanadate Laser Research Articles

Solid State Vanadate Laser and 213 nm Rayleigh Rejection Filter Enable Miniaturized Deep Ultraviolet Raman Spectrometers.

A combination of a highly efficient 213 nm Rayleigh rejection filter (RRF) and a miniaturized 213 nm neodymium-doped vanadate laser enables portable deep ultraviolet (UV) Raman spectrometers. We demonstrate the high efficiency of 213 nm RRF manufactured by Green Optics Co., Ltd by utilizing our compact 213 nm vanadate laser to measure high signal-to-noise ratio UV Raman spectra of Teflon and UV resonance Raman (UVRR) spectra of solid ammonium nitrate. We also demonstrate UVRR detection of trace amounts of ammonia formed during ammonium nitrate UV photolysis. We roughly estimate the ammonia UVRR detection limit of ∼10 ng under our experimental conditions.

Continuous-Wave Self-Raman Vanadate Lasers Generating Versatile Visible Wavelengths

In this review, the developments of efficient high-power CW orange-lime-green lasers by using intracavity stimulated Raman Scattering (SRS) in Nd-doped vanadate lasers are systematically discussed. The overall properties of the spontaneous Raman spectra in Nd:YVO4 and Nd:GdVO4 crystals are overviewed. The critical phase matchings of using the lithium triborate (LBO) crystals for sum frequency generation (SFG) and second harmonic generation (SHG) are thoroughly reviewed. We make a detailed review for achieving the individual green-lime-orange emissions from the self-Raman Nd:YVO4 and Nd:GdVO4 lasers with LBO crystals. The following is to review the dual-wavelength operations of the lime-green and orange-green lasers. Finally, the procedure for generating the triple-wavelength operation of orange-lime-green simultaneous emissions is completely described. The present review is expected to be useful for developing compact, efficient, high-power CW visible lasers for applications including medical treatment, biology, spectroscopy, and remote sensing.

Study on all solid-state 213 nm laser Raman spectrometer

Due to the adverse effects formed by fluorescence interference difficult to remove, intense interest has been directed towards the development of techniques and instrumentation to inhibit fluorescence. When the wavelength of Raman excitation light is less than 250 nm, we can completely separate the fluorescence noise from the Raman features in the UV spectrum. Based on this, we describe a new deep UV Raman spectroscopy system composed of a compact acousto-optically Q-switched diode-pumped solid-state (DPSS) neodymium-doped yttrium vanadate laser and a UV Raman spectrometer. The laser is capable of producing ∼140 mW of 213 nm power quasi-continuous wave as 9.6 ns pulses at a 20 kHz repetition rate. The UV Raman spectrometer with the incident slit of 50 μm width is based on Littrow structure, of which the spectral resolution is better than 0.05 nm in the band of 211.5 nm ∼ 235.5 nm meeting the requirements of 10 cm−1 Raman spectral resolution. We effectively reduce the volume of the test system and improve the robustness of the test system. We measure the deep UV Raman spectra of solution methanol, which verified the feasibility and rationality of the system.

Two-photon absorption in La0.05Gd0.95VO4 crystal at 523 nm under irradiation with picosecond pulses

Two-photon absorption (TPA) in La0.05Gd0.95VO4 crystal under irradiation with picosecond laser pulses with the duration of 25 ps at the wavelength of 523.5 nm has been investigated. The TPA coefficient was measured to be 0.074 cm/GW. We found that the two-photon inter-band excitation led to the creation of optical centers, which were characterized by a wide absorption band in the visible spectral region. The decay of the induced absorption is characterized by two temporal stages. The first rapid stage has the decay time of about 70 μs. However, the slow stage is characterized by a decay time ranging from 270 to 520 ms depending on the initial concentration of the induced optical centers. Induced absorption should be taken into account when developing vanadate lasers with intra-cavity second harmonic converters.

Machine learning algorithms predict experimental output of chaotic lasers.

We apply an artificial neural network (ANN) of 20 hidden layers and backpropagation regression to the forecast of experimental time series from a Kerr lens mode locking (KLM) Ti:sapphire laser and a Nd:vanadate with modulation losses. In both cases the neural network is able to predict up to 10 steps ahead. In the Ti:sapphire laser the prediction in pulse amplitude is accurate even when the pulse is an extreme event. In the Nd:vanadate laser we forecast both pulse amplitude and pulse-to-pulse time separation. In both cases the prediction goes beyond the Lyapunov prediction horizon.

Electro-optically Q-switching of dual-diode-pumped Ho-doped lutetium vanadate laser

In this paper we report on a continuous-wave and electro-optically (EO) Q-switched Ho-doped lutetium vanadate (Ho:LuVO4) laser dual end-pumped by two laser diodes at 1.94 µm. Under continuous-wave regime, a maximum output power of 18.8 W at 2058.1 nm was achieved with absorbed pump power of 44.7 W, corresponding to a slope efficiency of 54.1 % with respect to the absorbed pump power. By using a langasite (La3Ga5SiO14, LGS) crystal as the EO Q-switch, at a pulse repetition frequency of 3 kHz, the EO Q-switched Ho:LuVO4 laser produced a maximum pulse energy of 3.2 mJ and a minimum pulse width of 8.9 ns, resulting in a peak power of 358.8 kW.

Structured transverse modes governed by maximum entropy principle.

Based on the birefringent effect of the gain medium, a diode-pumped Nd-doped vanadate laser with nearly hemispherical cavity is exploited to emulate the quantum Green functions of two-dimensional commensurate harmonic oscillators. By matching the theoretical calculations to the far-field patterns of lasing modes, the resonant transverse frequencies can be accurately determined up to extremely high orders. The Shannon entropy is further employed to calculate the spatial entanglement of the quantum Green function as a function the transverse frequency. From the resonant transverse frequencies, all lasing modes are confirmed to be in excellent agreement with the maximum entropy states. This discovery implies that the formation of lasing modes is relevant to the coupling interaction between the pump source and the laser cavity.

Effects of Insertion of Ag Mid-Layers on Laser Direct Ablation of Transparent Conductive ITO/Ag/ITO Multilayers: Role of Effective Absorption and Focusing of Photothermal Energy.

From the viewpoint of the device performance, the fabrication and patterning of oxide–metal–oxide (OMO) multilayers (MLs) as transparent conductive oxide electrodes with a high figure of merit have been extensively investigated for diverse optoelectronic and energy device applications, although the issues of their general concerns about possible shortcomings, such as a more complicated fabrication process with increasing cost, still remain. However, the underlying mechanism by which a thin metal mid-layer affects the overall performance of prepatterned OMO ML electrodes has not been fully elucidated. In this study, indium tin oxide (ITO)/silver (Ag)/ITO MLs are fabricated using an in-line sputtering method for different Ag thicknesses on glass substrates. Subsequently, a Q-switched diode-pumped neodymium-doped yttrium vanadate (Nd:YVO4, λ = 1064 nm) laser is employed for the direct ablation of the ITO/Ag/ITO ML films to pattern ITO/Ag/ITO ML electrodes. Analysis of the laser-patterned results indicate that the ITO/Ag/ITO ML films exhibit wider ablation widths and lower ablation thresholds than ITO single layer (SL) films. However, the dependence of Ag thickness on the laser patterning results of the ITO/Ag/ITO MLs is not observed, despite the difference in their absorption coefficients. The results show that the laser direct patterning of ITO/Ag/ITO MLs is primarily affected by rapid thermal heating, melting, and vaporization of the inserted Ag mid-layer, which has considerably higher thermal conductivity and absorption coefficients than the ITO layers. Simulation reveals the importance of the Ag mid-layer in the effective absorption and focusing of photothermal energy, thereby supporting the experimental observations. The laser-patterned ITO/Ag/ITO ML electrodes indicate a comparable optical transmittance, a higher electrical current density, and a lower resistance compared with the ITO SL electrode.

228‐nm quadrupled quasi‐three‐level Nd:GdVO4 laser for ultraviolet resonance Raman spectroscopy of explosives and biological molecules

AbstractWe describe a new compact diode‐pumped solid‐state frequency quadrupled quasi‐three‐level neodymium‐doped gadolinium vanadate (Nd:GdVO4) laser that generates ~50 mW of 228‐nm quasi‐continuous wave light as ns pulses at a tunable kilohertz repetition rate. We developed two generations of this laser. The first generation has a high duty cycle and a tunable repetition rate. The second generation is optimized for maximum output power. We utilize these new lasers to measure ultraviolet resonance Raman (UVRR) spectra of many important chromophores that absorb in deep ultraviolet (UV). We demonstrate the utility of this excitation by measuring the 228‐nm absolute differential Raman cross sections of explosives, peptides, aromatic amino acids, and DNA/RNA nucleotides. Deep UV excitation at 228 nm occurs within the π → π* electronic transitions of these molecules. The 228‐nm resonance excitation enhances the Raman intensities of vibrations of NOx groups, peptide bonds, aromatic amino acid side chains, and DNA/RNA nucleotides. The measured 228‐nm UVRR cross sections of these molecules are 103–104 fold greater than those excited in the visible spectral region. These new lasers should be of great interest for UVRR spectroscopy and for other applications that benefit from compact, high average power deep UV laser light sources with low peak powers.

High-power diode-pumped Nd:GdVO4/KGW Raman laser at 578 nm.

A diode-pumped neodymium-doped gadolinium vanadate (Nd:GdVO4) laser is developed as a compact efficient yellow light at 578 nm by means of intracavity stimulated Raman scattering (SRS) in a potassium gadolinium tungstate (KGW) crystal and the second-harmonic generation in a lithium triborate crystal. The SRS process with a shift of 768cm-1 is achieved by setting the polarization of the fundamental wave along the Ng axis of the KGW crystal. The self-Raman effect arising from the Nd:GdVO4 crystal is systematically explored by employing two kinds of coating specification for the output coupler. With a specific coating on the output coupler to suppress the self-Raman effect, the maximum output power at 578 nm can reach 3.1 W at a pump power of 32 W. Moreover, two different lengths for the Nd:GdVO4 crystal are individually used to verify the influence of the self-Raman effect on the lasing efficiency.

Self-Raman Nd-doped vanadate laser: a pump source of organic crystal based difference frequency generation

We analyse a method of high repetition rate, efficient terahertz wave difference frequency generation (DFG) by using a self-Raman Nd-doped vanadate laser to pump 4’-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). A semi-analytical model is introduced that combines the rate equations (for the self-Raman dual-wavelength laser) and the coupled-wave equations (for the DAST-based DFG). Calculations were performed on a diffusion-bonded Nd:YVO4-YVO4 laser with an acousto-optic Q-switch. Parameters (including transmittances at output mirror and crystal lengths) were optimized to obtain high output. Sub-milliwatt average power is predicted under current pump condition.

Tribological behaviour of laser textured Ti6Al4V alloy coated with MoS2 and graphene

Ti-6Al-4V alloy was laser textured with cross groove patterns and then coated with graphene or MoS2, evaluating its tribological behaviour. The samples were textured by a solid state Nd:Vanadate (Nd:YVO4) laser, making crossed grooves with two different crossing angles, 45°and 60°, shaping a rhombus-like pattern. The percentage of surface area textured was 18, 40 and 64%. Solid lubricants were deposited by the cloth burnishing technique. Bidirectional sliding wear tests were performed to evaluate the tribological behaviour of the alloy. Lubricant working lifetimes were longer on textured and coated surfaces than on polished surfaces. Graphene presented longer lifetime than the MoS2 for 18 and 40% of textured density but rather similar for the 64%.

Cost Effective Profiling of Neodymium-Doped Vanadate Laser Pulses

As environmental conditions and component degradation and failure are known to affect the performance of ultrafast lasers, it is important to monitor their state in any nonlinear optical study. This may be achieved by measuring the temporal width of the laser pulses using an autocorrelator. In this work, an autocorrelator for measuring the pulsewidth of mode-locked lasers was custom-built using pieces of equipment usually found in a typical ultrafast optics laboratory. The assembled equipment was tested using SESAM (Saturable Semiconductor Absorber Mirror) mode-locked neodymium-doped vanadate (Nd:YVO4) laser having manufacturer specified average output power of 1.6 W and 10 ps pulsewidth. Using the background-free autocorrelation technique, the pulse width of the laser was measured to be 10.4 ps. This type of autocorrelator is cost effective and may be handy in situations where research funds are limited; a scenario commonly experienced in research laboratories of developing countries. Additionally, the processes involved in assembling the autocorrelator provide a useful learning experience for new researchers. The study also outlined the processes involved in modifying an existing autocorrelation setup in order to measure laser beam spot size; a useful parameter in nonlinear optical studies.

Influence of laser parameters in surface texturing of Ti6Al4V and AA2024-T3 alloys

Laser texturing can be used for surface modification of metallic alloys in order to improve their properties under service conditions. The generation of textures is determined by the relationship between the laser processing parameters and the physicochemical properties of the alloy to be modified. In the present work the basic mechanism of dimple generation is studied in two alloys of technological interest, titanium alloy Ti6Al4V and aluminium alloy AA2024-T3.Laser treatment was performed using a pulsed solid state Nd: Vanadate (Nd: YVO4) laser with a pulse duration of 10 ps, operating at a wavelength of 1064 nm and 5 kHz repetition rate. Dimpled surface geometries were generated through ultrafast laser ablation while varying pulse energy between 1 µJ and 20 µJ/pulse and with pulse numbers from 10 to 200 pulses per spot. In addition, the generation of Laser Induced Periodic Surface Structures (LIPSS) nanostructures in both alloys, as well as the formation of random nanostructures in the impact zones are discussed.

Acousto-optically Q-switched 0.91 μm Nd3+-doped vanadate lasers and 0.45 μm blue-light emissions by intracavity frequency-doubling

Diode-laser pumped Q-switched Nd3+-doped vanadate lasers at 0.91μm and intracavity frequency-doubling of 0.45μm blue light emissions are studied. Using a compact V-type laser cavity and a miniature acousto-optically (AO) Q-switch, the highest average output powers of 2.2W 0.912μm Nd:GdVO4 laser and 1.59W 0.914μm Nd:YVO4 laser are obtained at repetition rate of 10kHz, with the optical conversion efficiency of 7.4% and 5.3%, and the slope efficiency of 14.8% and 9.5%. Employing a BiBO crystal as frequency-doubler, 1.3W, 37ns 0.456μm and 0.84W, 37.4ns 0.457μm pulsed blue light are emitted at 10kHz, corresponding to the peak power of 3.51kW and 2.25kW, respectively. In addition, stable operation is up to 100kHz.

플렉서블 기판 전/후면에서의 레이저를 이용한 ITO/Ag/ITO 전극층의 식각 특성

ITO/Ag/ITO conductive films on PET (polyethylene terephthalate) was etched by a Q-switched diode-pumped neodymiun-doped yttrium vanadate (Nd:YVO4, <TEX>${\lambda}=1064nm$</TEX>) laser. During the laser direct etching, the laser beam was incident on the two different directions of PET and the etching patterns were investigated and analyzed. At a lower repetition rate of laser pulse, the larger laser etched patterns were obtained by laser beam incident on reverse side of PET substrate. On the contrary, at a higher repetition rate, it was possible to find the larger etched patterns in case of the laser beam incidence on forward side of PET substrate. For the laser beam incidence on reverse side, the laser beam is expected to be transferred and scattered through the PET substrate and the laser beam energy is thought to be dependent on the etch laser pulse beam energy.

Compact Solid-State 213 nm Laser Enables Standoff Deep Ultraviolet Raman Spectrometer: Measurements of Nitrate Photochemistry.

We describe a new compact acousto-optically Q-switched diode-pumped solid-state (DPSS) intracavity frequency-tripled neodymium-doped yttrium vanadate laser capable of producing ~100 mW of 213 nm power quasi-continuous wave as 15 ns pulses at a 30 kHz repetition rate. We use this new laser in a prototype of a deep ultraviolet (UV) Raman standoff spectrometer. We use a novel high-throughput, high-resolution Echelle Raman spectrograph. We measure the deep UV resonance Raman (UVRR) spectra of solid and solution sodium nitrate (NaNO3) and ammonium nitrate (NH4NO3) at a standoff distance of ~2.2 m. For this 2.2 m standoff distance and a 1 min spectral accumulation time, where we only monitor the symmetric stretching band, we find a solid state NaNO3 detection limit of ~100 μg/cm(2). We easily detect ~20 μM nitrate water solutions in 1 cm path length cells. As expected, the aqueous solutions UVRR spectra of NaNO3 and NH4NO3 are similar, showing selective resonance enhancement of the nitrate (NO3(-)) vibrations. The aqueous solution photochemistry is also similar, showing facile conversion of NO3(-) to nitrite (NO2(-)). In contrast, the observed UVRR spectra of NaNO3 and NH4NO3 powders significantly differ, because their solid-state photochemistries differ. Whereas solid NaNO3 photoconverts with a very low quantum yield to NaNO2, the NH4NO3 degrades with an apparent quantum yield of ~0.2 to gaseous species.

Direct Ablation by Laser of Single Graphene Monolayer and Graphene/Photopolymer Double Layer.

A diode-pumped Q-switched neodymium-doped yttrium vanadate (Nd:YVO4, λ = 1064 nm) laser was applied to obtain graphene patterns on a photopolymer layer by direct ablation. In the transfer process of the graphene layer, the photopolymer was employed as a graphene supporting layer and it was not removed for the simplification of the process. The laser ablation was carried out on graphene/photopolymer double layers for various beam conditions. The results showed that the laser-ablated widths on the graphene/photopolymer double layer were much greater than those on the graphene monolayer, especially at lower scanning speeds and at higher repetition rates. The photopolymer layer was not removed by the laser ablation, and the thermal energy was considered to have been dissipated in the lateral direction of graphene instead of being conducted vertically to the glass substrate. The Raman spectrum results showed that the graphene layer was clearly removed on the laser-ablated region of interest.

Laser Direct Ablation of Indium Tin Oxide Films on Both Sides of Various Substrates.

We demonstrate ablation of indium tin oxide (ITO) films onto both glass and polyethylene terephthalate (PET) substrates, using a Q-switched diode-pumped neodymium-doped yttrium vanadate laser (Nd:YVO4, λ = 1064 nm) incident on both the front and back sides of the substrate. From scanning electron microscope (SEM) images and depth profile data, ITO patterns that were laser-ablated onto glass from the back side showed a larger abrupt change in the ablated line width than those ablated from the front. However, there were only slight differences in ablated line widths due to the direction of the incident laser beam. We provide a possible explanation in terms of several factors: dispersion of laser beam energy through the substrate, overlapping of each laser beam spot due to scanning speed, and the thickness of glass and PET substrates.

Back Cover: Advances in vanadate laser crystals at a lasing wavelength of 1 micrometer (Laser Photonics Rev. 8(6)/2014)

Laser & Photonics ReviewsVolume 8, Issue 6 Back CoverFree Access Back Cover: Advances in vanadate laser crystals at a lasing wavelength of 1 micrometer (Laser Photonics Rev. 8(6)/2014) First published: 04 November 2014 https://doi.org/10.1002/lpor.201470062AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Vanadate crystals are prominent optical materials, and play important roles in optics, especially in lasers and nonlinear optics. Vanadate crystals are being developed with the goal of fulfilling the need for differential applications and improvement of certain operational aspects. The vanadate laser crystals are reviewed by highlighting the most recent research progress and possible future applications are proposed. (Picture: Haohai Yu et al.10.1002/lpor.201400022, pp. 847–864, in this issue) Volume8, Issue6November 2014 RelatedInformation