Neodymium-doped Yttrium Vanadate Research Articles

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.

Self-Raman 1176 nm Laser Generation from Nd:YVO4 Crystal by Resonator Cavity Coating

Crystal coating is an important process in laser crystal applications. According to the crystal characteristics of neodymium-doped yttrium vanadate (Nd:YVO4), its intrinsic parameters, and optical film design theory, Ta2O5 and SiO2 were selected separately as high and low refractive index materials. The optical properties and surface roughness of the films were characterized by OptiLayer and Zygo interferometers, and the effects of ion source bias on refractive index and surface roughness were investigated so that the optimal ion source parameters were determined. Optical monitoring and quartz crystal control were combined to accurately control the thickness of each film layer and to reduce the monitoring error of film thickness. The prepared crystal device was successfully applied to the 1176 nm laser output system.

Self-Mixing Displacement Measured by a Two-Color Laser in 66-nm Steps

We demonstrate a new self-mixing interferometer (SMI) simultaneously working on two wavelengths, the fundamental at 1064 nm and the second harmonic at 532 nm delivered in the same beam. The beam is sent to the remote target in the usual way, and in the return path, two photodiodes detect the two self-mixing signals without crosstalk. As the source, we were able to use a diode-pumped neodymium-doped yttrium vanadate (Nd:YVO4 laser crystal) with potassium titanyl phosphate (KTP nonlinear crystal) two-color laser of a commercial pointer. With simple processing of the two self-mixing signals, we are able to obtain the interferometric signals <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cos (2ks)$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sin (2ks)$ </tex-math></inline-formula> at 532 nm, from which the unambiguous measurement of arbitrary target displacement follows with counts in units of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda /8$ </tex-math></inline-formula> of the second-harmonic wavelength or 66 nm.

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.

High-average and high-peak output-power terahertz-wave generation by optical parametric down-conversion in MgO:LiNbO3

A widely tunable terahertz (THz)-wave generation that has a high repetition rate and a narrow line width is demonstrated in this paper by injection-seeded THz-wave parametric generation (is-TPG) in a MgO:LiNbO3 crystal. By pumping the crystal using a passively Q-switched neodymium-doped yttrium vanadate microchip laser with a time duration of 140 ps and an average power of up to 5 W, a THz-wave output with an average output power of 30 μW, a peak power of 4 W, a pulse duration of 73 ps, and a pulse-repetition frequency of 100 kHz is obtained. To prevent laser damage and photorefractive damage to the crystal, the constraints on the pumping condition of the MgO:LiNbO3 crystal are experimentally studied by changing the pumping parameters. As a result, we achieved the stable generation of the THz-wave signal in the 100 kHz regime. Moreover, we performed THz-wave imaging by using the developed is-TPG source. The obtained THz image indicated that the developed system has a good stability over long periods of time.

Temporally Programmable Hybrid MOPA Laser with Arbitrary Pulse Shape and Frequency Doubling

An arbitrary pulse shape by compensating gain saturation in a solid-state Master oscillator power amplifier (MOPA) system made up of three Neodymium doped yttrium vanadate (Nd:YVO4) amplifiers is demonstrated. By investigating the amplifier dynamics in detail, car-shaped pulse shapes were obtained with compensated pulse distortion. Desired pulse shapes, such as multiple-step, square, parabolic, and Gaussian pulses, were achieved, with a high peak power level of 41.6 kW and a narrow linewidth less than 0.06 nm. In addition, through second harmonic generation (SHG), a green laser with different pulse shapes was obtained, with a maximum conversion efficiency of 42.6%.

Estimation of damage ratio of IINDYV nanowaveguide using modified equation

Estimation of damage ratio of ion-implanted neodymium-doped yttrium vanadate (IINDYV) waveguide is thoroughly explored in this paper. In this research, waveguide is realised by the combination of two IINDYV layers separated by air. Different type of losses such as absorption, reflection, diffraction and polarisation are cogitated during the investigation of intensity transmitted through said waveguide. Reflectance from IINDYV waveguide is obtained by using plane wave expansion technique where absorption loss is found by solving Maxwell's equation. Aside this, we also deal with both diffraction and polarisation loss along with reflection and absorption. Finally, transmitted intensity through IINDYV waveguide is computed. The computation result reveals an interesting out comes to obtain damage ratio in above nanowaveguide. For example, reflectance's, diffraction and polarisation efficiencies vary linearly with respect to damage ratio. Aside this, it is found that absorption loss is zero for both ordinary and extraordinary ray. Finally, it is divulged that intensity transmitted through IINDYV waveguide vary linearly and the variation is nicely fitted with trend line (R2=0.994 for both O-rays and E-rays), which leads to an exact estimation of damage ratio in IINDYV waveguide.

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.

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.

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.

Ablation of graphene film by direct Nd:YVO4 laser under various beaming conditions.

Recently, graphene is gaining increasing popularity as one of the most functional materials for advanced electronic and optical devices owing to its high carrier mobility and optical transparency. Patterning the graphene calls for particular cares in line definition without carbon (C)-based residues that might be working as a leakage path. Thus, realization and processing of the graphene monolayer are very complicated and need to be stringently controlled. For this reason, in accordance, processing technology should be evolved with higher reliability and accuracy, and compatibility with the conventional unit processes including electron beam (e-beam) lithography, plasma etching, and nano-dimensional optical lithography. In this work, a reliable, simple, and cost-effective technique for patterning the graphene is proposed. Graphene film transferred on glass substrate is directly patterned by a quality factor (Q)-switched neodymium-doped yttrium vanadate (Nd:YVO4, λ = 1064 nm) pumped laser diode (LD). In order to optimize the process condition, various beaming conditions of repetition rate and scanning speed are experimented. From the optical microscope images, it has been shown that graphene film was more easily etched by direct laser patterning technique at higher repetition and faster scanning speed. It was confirmed by Raman spectrum where 2-dimensional (2-D) and graphite (G) peaks were closely investigated that graphene residue was also completely removed after the proposed processing technique.

All-fiber frequency-doubled visible laser.

All-fiber ns-pulsed visible laser at λ=521 nm is realized by frequency doubling an Yb-doped fiber laser with a periodically poled silica fiber. A 50-mW second-harmonic (SH) output power is produced that is over 6-orders of magnitude greater than previous results obtained with poled fibers in the visible spectral range. The normalized conversion efficiency of 0.3%/W is to date the largest demonstrated with poled fiber technology. Furthermore, 21% conversion efficiency is achieved for the doubling of 8-ps pulses from a neodymium-doped yttrium vanadate solid-state laser. The advances are made possible by the precision and flexibility offered by using the continuous periodic UV erasure, as opposite to photolithographic methods, for the fabrication of over 20-cm-long χ(2)-gratings for quasi-phase matched SH generation.

Laser Direct Patterning of Indium Tin Oxide for Defining a Channel of Thin Film Transistor

In this work, using a Q-switched diode-pumped neodymium-doped yttrium vanadate (Nd:YVO4, lambda = 1064 nm) laser, a direct patterning of indium tin oxide (ITO) channel was realized on glass substrates and the results were compared and analyzed in terms of the effect of repetition rate, scanning speed on etching characteristics. The results showed that the laser conditions of 40 kHz repetition rate with a scanning speed of 500 mm/s were appropriate for the channeling of ITO electrodes. The length of laser-patterned channel was maintained at about 55 microm. However, residual spikes (about 50 nm in height) of ITO were found to be formed at the edges of the laser ablated area and a few ITO residues remained on the glass substrate after laser scanning. By dipping the laser-ablated ITO film in ITO diluted etchant (ITO etchant/DI water: 1/10) at 50 degrees C for 3 min, the spikes and residual ITO were effectively removed. At last, using the laser direct patterning, a bottom-source-drain indium gallium zinc oxide thin film transistor (IGZO-TFT) was fabricated. It is successfully demonstrated that the laser direct patterning can be utilized instead of photolithography to simplify the fabrication process of TFT channel, resulting in the increase of productivity and reduction of cost.

Refractive index profile in ion-implanted neodymium-doped yttrium vanadate waveguide: the relation between index change and lattice damage

A model is presented to explain the refractive index changes in the ion-implanted neodymium-doped yttrium vanadate waveguide region, which is helpful for characterizing index profile dependence on implanta- tion parameters. It indicates that the lattice damage is the main factor for the refractive index changes. Waveguide structure is formed mainly due to an increase of ordinary refractive index in the ion-implanted region. The theoretical results based on this model are in good agreement with the experimental data from 500 keV Si þ ion implantations and keV He þ ion implantations. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI:

Laser ablation of amorphous indium gallium zinc oxide films deposited by different RF powers

For the realization of transparent oxide semiconductor device, it is indispensable to suggest a new simple patterning process instead of photolithography. As a new method of patterning, neodymium doped yttrium vanadate (Nd:YVO4) laser ablation was applied to pattern amorphous-indium gallium zinc oxide (a-IGZO) films which were deposited by different radio frequency (RF) sputtering power. For the a-IGZO film deposited at 50W, a continuous etched line was obtained only for the laser beam with a scanning speed of 50mm/s. However, in case of a higher power such as 800W, the film was easily etched for all the laser processing conditions. The width of these laser ablated grooves was also reported in terms of the dependency on RF sputtering power, repetition rate, and scanning speed. The different phenomena of laser etching in a-IGZO films deposited by different RF sputtering power are attributed to the increase of absorption coefficient and the increase of atomic percentage of In as the RF sputtering power increased.

Transverse diode-pumped neodymium-doped yttrium vanadate laser of simple design

Abstract. The design and performance of an all-solid-state Nd:YVO 4 laser, transversely pumped by a single 20-W at 808 nm diode with nocoupling optics, are presented. The prototype, which is devised to be thesource of a micro-LIDAR station, is very simple, easy to align, compact,and stable. The key element is a roof prism as the end mirror of the lasercavity, which is used to symmetrize the effects of the thermal distortionand the inhomogeneity of the population inversion distribution. Typicalnumbers are 4.2-W cw with a slightly astigmatic 3:2 homogeneous spotand a divergence of 0.5 mrad. The protoype is also tested in the activeQ-switching mode, providing pulses 50-ns full width at half maximum FWHM at 14 KHz, 3.5 W average. Frequency doubling external to thecavity in a nonoptimized configuration provides 700 mW at 532 nm. © 2010 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.3361670 Subject terms: diode-pumped solid-state lasers; thermal effects; high-powertransversal pumping; LIDAR

Infrared luminescence spectrum and crystal-field analysis of neodymium-doped yttrium vanadate

The 4F 3 2 → 4I 9 2 4I 11 2 , 4I 13 2 , 4I 15 2 luminescence spectra of Nd 0.001 Y 0.999VO 4 have been recorded at temperatures down to that of liquid helium and are analyzed in detail. Luminescence is reported for the first time from the 4F 5 2 level, which is thermally populated from 4F 3 2 . New assignments are given for energy levels from the 20 K visible absorption spectrum of the same material. From these results, forty-eight levels are fitted by varying twelve parameters with arms energy deviation of 10.3 cm −1. Vibronic sidebands are reported from the luminescence of HoVO 4 and YVO 4: Ho 3+, corresponding to the excitation of single quanta of internal vanadate and lattice modes.