YAG Cavity Research Articles

Compact coupling scheme to achieve the synchronously dual self-mode-locked operation with a 35.2 THz optical beating.

A synchronously dual self-mode-locked (SML) operation at 946 and 1064nm is experimentally accomplished by using a compact coupling scheme to obtain the optical beating frequency up to 35.2THz. The SML emissions at 946 and 1064nm are established by a monolithic Nd:YAG cavity and a Nd:YVO₄ crystal in a flat-flat cavity, respectively. Two gain media are butt adjoined to be longitudinally pumped by a single laser diode. The monolithic Nd:YAG crystal is used not only as the 946nm laser cavity, but also as the output coupler of the Nd:YVO₄ 1064nm laser. More importantly, the output surface of the monolithic Nd:YAG laser is coated to generate the optical feedback for the synchronization of the dual SML operation. At a pump power of 10.7W, the output powers at 1064 and 946nm can simultaneously reach 1.5W by controlling the focal position of the pump waist.

Designing a Broadband Pump for High-Quality Micro-Lasers via Modified Net Radiation Method.

High-quality micro-lasers are key ingredients in non-linear optics, communication, sensing and low-threshold solar-pumped lasers. However, such micro-lasers exhibit negligible absorption of free-space broadband pump light. Recently, this limitation was lifted by cascade energy transfer, in which the absorption and quality factor are modulated with wavelength, enabling non-resonant pumping of high-quality micro-lasers and solar-pumped laser to operate at record low solar concentration. Here, we present a generic theoretical framework for modeling the absorption, emission and energy transfer of incoherent radiation between cascade sensitizer and laser gain media. Our model is based on linear equations of the modified net radiation method and is therefore robust, fast converging and has low complexity. We apply this formalism to compute the optimal parameters of low-threshold solar-pumped lasers. It is revealed that the interplay between the absorption and self-absorption of such lasers defines the optimal pump absorption below the maximal value, which is in contrast to conventional lasers for which full pump absorption is desired. Numerical results are compared to experimental data on a sensitized Nd3+:YAG cavity, and quantitative agreement with theoretical models is found. Our work modularizes the gain and sensitizing components and paves the way for the optimal design of broadband-pumped high-quality micro-lasers and efficient solar-pumped lasers.

Study The effect of central ion to the dithene complexes on spectral shifting of saturable absorber band

In this work dithine complexes prepared from dithiol benzil ligand and central ion to the Ni,Pd,Pt, element the ligand and complexes have been investigated using FTIR spectrophotometer and uv-vis-NIR spectral reigns show higher intensity represents the ?-?* transition in the chromopher cycle .These absorption which appear in visible and near IR spectral regions ,According to the complexes of one group ,the spectral shifting due to the change of central ion has been found to be related to atomic number of central ion .This shifting is increased while decreasing the central ion atom number These complexes have been implemented in Nd+2:YAG cavity because each posses resonant absorption band near Nd+2:YAG, Nd+2:Glass emitting at (1060nm). pulse duration measured to complexes dissolved in dioxin(2*10-3M) is very short compared with free running pulse duration ,therefore the complexes work as Q-switch to the NIR lasers.

Study The effect of central ion to the dithene complexes on spectral shifting of saturable absorber band

In this work dithine complexes prepared from dithiol benzil ligand and central ion to the Ni,Pd,Pt, element the ligand and complexes have been investigated using FTIR spectrophotometer and uv-vis-NIR spectral reigns show higher intensity represents the ?-?* transition in the chromopher cycle .These absorption which appear in visible and near IR spectral regions ,According to the complexes of one group ,the spectral shifting due to the change of central ion has been found to be related to atomic number of central ion .This shifting is increased while decreasing the central ion atom number These complexes have been implemented in Nd+2:YAG cavity because each posses resonant absorption band near Nd+2:YAG, Nd+2:Glass emitting at (1060nm). pulse duration measured to complexes dissolved in dioxin(2*10-3M) is very short compared with free running pulse duration ,therefore the complexes work as Q-switch to the NIR lasers.

Temperature rise during Er:YAG cavity preparation of primary enamel

This study aimed to assess in vitro thermal alterations taking place during the Er:YAG laser cavity preparation of primary tooth enamel at different energies and pulse repetition rates. Forty healthy human primary molars were bisected in a mesio-distal direction, thus providing 80 fragments. Two small orifices were made on the dentin surface to which type K thermocouples were attached. The fragments were individually fixed with wax in a cylindrical Plexiglass® abutment and randomly assigned to eight groups, according to the laser parameters (n = 10): G1 - 250 mJ/ 3 Hz, G2 - 250 mJ/ 4 Hz, G3 - 250 mJ/ 6 Hz, G4 - 250 mJ/10 Hz, G5 - 250 mJ/ 15 Hz, G6 - 300 mJ/ 3 Hz, G7 - 300 mJ/ 4 Hz and G8 - 300 mJ/ 6 Hz. An area of 4 mm(2) was delimited. Cavities were done (2 mm long × 2 mm wide × 1 mm thick) using non-contact (12 mm) and focused mode. Temperature values were registered from the start of laser irradiation until the end of cavity preparation. Data were analyzed by one-way ANOVA and Tukey test (p ≤ 0.05). Groups G1, G2, G6, and G7 were statistically similar and furnished the lowest mean values of temperature rise. The set 250 mJ/10 and 15 Hz yielded the highest temperature values. The sets 250 and 300 mJ and 6 Hz provided temperatures with mean values below the acceptable critical value, suggesting that these parameters ablate the primary tooth enamel. Moreover, the temperature elevation was directly related to the increase in the employed pulse repetition rates. In addition, there was no direct correlation between temperature rise and energy density. Therefore, it is important to use a lower pulse frequency, such as 300 mJ and 6 Hz, during cavity preparation in pediatric patients.

Laser Er:YAG et odontologie restauratrice

The capacity of Er:YAG laser (λ = 2,940 nm) both to eliminate carious tissues and to prepare cavities for adhesive restorations has been widely demonstrated. The marketed apparatus allow cavities preparation with a suitable clinical working time. All of them are equipped with an internal cooling system for air and water pulverisation at the impact point of the laser beam. This system limits intrapulpal temperature rise to less than the biologically acceptable threshold of 5°C. Histological studies showed that the pulpal response to the Er:YAG laser irradiation of dental hard tissues is minor, localised and reversible, equivalent to those consecutive to the use of high speed rotative instruments in the same refreshment conditions. When Er:YAG laser has been used on dentin, the microscopic examinations revealed the absence of smear layer and open dentinal tubules. The intertubular dentin is partially removed due to the larger water content in its composition. Conversely, Er:YAG laser is less effective on peritubular dentin; it does not enlarge the tubule orifices, providing a microcrater-like appearance of laser irradiated surfaces. Direct composite resin bonding to the Er:YAG laser irradiated dentin, without acid pre-treatment, has been suggested. In a recent publication, the authors demonstrate that acid pre-treatment of the irradiated dentin surface results in similar microscopic observations at dentin-composite resin interfaces when compared with dentin bur preparation. The adhesion values of the composite resin to the irradiated dentin with or without acid etching are comparable to those measured with conventional bonding (bur + acid). Conversely, composite restorations of laser Er:YAG cavity preparations show significantly less microleakage when orthophosphoric acid is applied before bonding. First clinical applications concerning the preparation of Er:YAG laser cavities did not show any side effects. The absence of pain, noise and vibrations are of value in comparison with conventional mechanical preparations.

Passively Q-switched self-frequency doubling Nd xY 1− xAl 3(BO 3) 4 laser with Cr 4+:YAG saturable absorber

Using a new saturable absorber Cr 4+:YAG as passive Q-switch, we have realized the Q-switched laser running at 0.531 μm with an NYAB self-frequency doubling crystal and measured the single pulse energy and the pulse width under different small-signal transmissions of Cr 4+:YAG and different cavity lengths. Meanwhile, the coupling wave rate equations for Cr 4+:YAG as a passive Q-switch are given and the experimental results agree with the numerical solution of equations.

Simple, high-performance type II β-BaB_2O_4 optical parametric oscillator

A visible /near-IR optical parametric oscillator (OPO) based on type II phase matching in ?-BaB2 O4 (BBO) is described. Pumped at 355 nm, this OPO covers 410 -2500 nm completely with a single set of standard Nd:YAG cavity optics. The output efficiency is >25 %, the linewidth of the OPO is narrower than 1 -2 cm-1 without the use of gratings or etalons, and the signal-beam divergence is <400 ?rad. Three type I BBO doubling crystals are used to extend the tuning range from 208 to 415 nm. Doubling efficiencies as high as 40 % are easily obtained. The reasons for the high doubling and overall system efficiency are discussed.

Single-frequency Q-switched Cr,Nd:YAG laser operating at 946-nm wavelength

Single-frequency Q-switched operation in 946-nm wavelength has been demonstrated by application of a monolithic Cr,Nd:YAG cavity. In this device, the Cr,Nd:YAG laser material performs the functions of light modulation, frequency stabilization, and polarization selection. The conditions for the single-frequency operation and maximum degree of polarization are discussed.

On correlated phase fluctuations in a frequency doubled Nd:YAG laser

We report here observations of correlated frequency fluctuations between the fundamental and the second harmonic of a flash lamp pumped Nd:YAG laser. Also we show that the frequency of the second harmonic can be stabilised using an error signal derived from frequency fluctuations in the second harmonic to control the length of the Nd:YAG cavity, and hence the frequency of the fundamental.

A high power, tunable, arc-lamp pumped Nd-doped lanthanum-hexaluminate laser

An LNA (Nd-doped lanthanum-hexaluminate) crystal has been pumped with a cw, krypton arc lamp in a commercial Nd:YAG cavity. The cw output power greater than 6 W is obtained in a 28-cm long, plane mirror cavity. The free-running wavelength is near 1083 nm and has a width of about 0.8 nm. Inserting a 0.25 mm thick, uncoated solid etalon in the cavity permits the laser output to be continuously tuned from 1082 to 1084 nm by tilting the etalon. The laser bandwidth is reduced to below 0.016 nm. Over 3 W are obtained at the helium resonance transition. The maximum power output is limited by severe thermal lensing effects in the LNA crystal. The single, arc-lamp pump is operated at less than 70% of its maximum rated current; thus, substantial increases in the power output can be expected if crystal quality can be improved.