High Power Copper Vapor Laser Research Articles

Nanosecond pulsed laser ablation of synthetic graphite in liquids for the synthesis of spherical graphene

Pulsed laser ablation in liquids has become a simple, fast, and environmentally friendly method for the synthesis of carbon nanostructures since it does not require the use of toxic chemicals. The great advantage of this method is its ability to control the size, shape, and structure of the products by combining parameters of the laser, target material, and liquid. By ablation of two types of synthetic graphite with a high-power copper vapor laser in ethanol and distilled water, spherical graphene was obtained. The composition of the gas phase and the condensation temperature of carbon in the temperature range of 1000–5000 K were determined by means of thermodynamic modeling. The precursors for the formation of spherical graphene during laser ablation in alcohol and water are discussed.

Axicon based conical resonators with high power copper vapor laser

We report for the first time the performance of axicon based conical resonators (ABCRs) in a copper vapor laser, with novel results. The unstable conical resonator comprising of conical mirror (reflecting axicon) with axicon angle approximately pi/18, cone angle approximately 160 degrees, and a convex mirror of 60 cm radius of curvature was effective in reducing the average beam divergence to approximately 0.15 mrad (approximately 25 fold reduction compared to standard multimode plane-plane cavity) with output power of approximately 31 W. Extraction efficiency of approximately 50%-60% and beam divergence of <1 mrad was achieved in other stable ABCR configurations using flat and concave mirrors with the axicon. This is a significant improvement compared to 4-5 mrad normally observed in conventional stable resonators in copper vapor lasers. The conical resonators with copper vapor laser provide high misalignment tolerance beta approximately 4-5 mrad where beta is the tilt angle of the conical mirror from optimum position responsible for approximately 20% decline in laser power. The depth of focus d was approximately three times larger in case of conical resonator as compared to that of standard spherical unstable resonator under similar beam divergence and focusing conditions.

Characterizing flat-top laser beams using standard beam parameters

We examine the correspondence between various models describing flat-top laser beam profiles using two standard parameters; namely, the M2 factor and the kurtosis parameter. Numerical expressions for M2, based on the second moment of the beam irradiance distribution in the near and far fields and for the kurtosis parameter, k, based on the fourth moment at the near field, are obtained. Plots of k in the near field versus M2 demonstrate the similarities between the different analytical models used to describe flat-top profiles. Using the Padé approximation, a relationship between k and M2, a new reference formula, is derived that predicts the values of M2 to within less than a percent for these flattened beams. This method is then extended to define numerical expressions relating the beam parameters (i.e., M2 and k) and the parameters describing the beam characteristic in each analytical model (model parameters). The results obtained using the Padé method are used to describe the output beam profiles for a high power copper vapour laser fitted with an unstable resonator.PACS Nos.: 42.55.–f, 42.55.Lt, 42.60.–v

Characteristics of a 100-mm-Bore Copper Vapor Laser and Their Prediction by a Gas Cooling Model

A high-power copper vapor laser (CVL) scaled up to a 100 mm bore has been developed. In a large-bore CVL, there is a problem that the radial beam profile becomes nonuniform, which is caused by the high temperature of the buffer gas. Two methods have been applied to gas cooling: hydrogen addition to the buffer gas and insertion of gas cooling plates. Modeling of the increased thermal conductivity by hydrogen addition and of the radiation effect by plate insertion predicted that the buffer gas temperature would drop from 4160 K to 2650 K under typical operating conditions. Experimental results showed that the beam profile was improved especially at high repetition frequencies and high input powers. The CVL with a plasma tube length of 2.3 m was able to generate an output power of 329 W as an oscillator.

The study and new progress in the high power copper vapor laser

The design parameters of A 100-W copper vapor laser were demonstrated by analyzing and calculating its major parameters such as the size of the discharge tube, the input electrical power and the width of the thermal insulator. The maximum output power 112-W and 1 % efficiency were achieved recently. The performances of the 100-W copper vapor laser needed to improve are discussed.

Improvement of high-current large-volume discharge with profiled hollow-cathode electrodes

Filamentary discharge at the electrode of high-power copper vapor lasers prevents stable operation when the buffer gas (Ne) pressures exceeds 30 torr. Experimental evidence indicates that the discharge constriction starts in the cathode fall region. The volumetric power deposition at the cathode fall is estimated to be /spl sim/130 MW/cm/sup 3/ at 40 torr during a peak discharge current of 2.5 KA. This highly pressure-dependent (/spl alpha/ P/sup 7/3/) large thermal loading at cathode fall is likely to initiate thermal instability as pressure increases. This discharge instability can be mitigated by taking advantage of the hollow-cathode effect even for pressures exceeding 100 torr. We have designed a large-area electrode with many hollow-cathode grooves spreading over the uniform-field-profile area of the electrode for enhanced electron emission. This unique design lowers the cathode-fall voltage, and as a consequence, reduces the thermal loading at the cathode fall. With this profiled, hollow-cathode electrode, we have successfully extended stable discharge from /spl sim/30 to /spl sim/100 torr. We believe this profiled electrode design with multiple hollow-cathode grooves will expand hollow-cathode electrodes to many applications that require high-current large-volume discharge at elevated pressures.

Amplified stimulated emission in the NaK(D?X) band by high power copper vapor laser pumping

Using a 10 W copper vapor laser we have studied a stimulated emission at 520–570 nm in the D→X electronic transition of the NaK heteronuclear molecule. The influence of the cavity configuration on the bound-bound stimulated lines is considered.

Stabilization of high-power copper vapour laser

Design considerations for stable trouble-free operation of a 100 W copper vapour laser are described. Implementation of laser head and modulator design principles result in a laser that meets these goals. The laser is switched by a single small thyratron that operates below all its maximum ratings.

Histology of port wine stains after copper vapour laser treatment.

We report histological changes in four patients with port wine stains treated with 578 nm yellow light from a high power copper vapour laser. Histology showed that selective damage occurred to the ectatic blood-vessels in the dermis, without haemorrhage and damage to non-vascular structures, and without scarring. The initial damage to the overlying epidermis was not permanent, and the damaged ectatic vessels returned to normal size or were completely necrosed and replaced by collagen.

Annular discharge copper vapor laser

A large-volume high-power copper vapor laser excited by a longitudinal discharge in an annular volume has been demonstrated. The annular geometry provides a device configuration in which the laser prf, governed by a geometric diffusion length, can be made independent of the device volume. Laser powers of 35 W at a prf of 6 kHz has been obtained with an overall device efficiency of 0.44%.