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1.
With the development of suitable instrumentation, human-engineered to fulfil the requirements of the clinical surgeon and designed to fit in with the physical conditions prevailing in the operating theatre, laser surgery has advanced rapidly in the past few years. It shows signs of even more rapid progress and general acceptance as its application and advantages in more and more fields of surgery are demonstrated. 相似文献
2.
Factors affecting the design of compact heterodyne- and direct-detection systems are contrasted. Recent UK achievements are placed in context: a TEA laser direct-detection rangefinder and a chirp-pulse-comparison rangefinder-velocimeter are described. 相似文献
3.
The aim of this work is to report the achievement of a light weight, compact, high power CO 2 laser which can be used in industry. The construction and operation of a CO 2 gas transport laser with cylindrical geometry and two parallel electrical discharges are presented. Using a 600 mm diameter, 1400 mm length, 250 kg laser head, we have obtained more than 1.6 kW laser power with 2% stability and 2 mrad full angle divergence. For comparison the results are presented for one electrical discharge laser. 相似文献
4.
For the first time it has been possible to laser weld copper sheets up to 3 mm thick with a 2 kW cw CO 2 laser. The main questions arising from the process are indicated. 相似文献
5.
Apparatus for the measurement of spot sizes and pulse lengths of a high-power laser beam is described. Knowledge of these parameters is important in, for example, materials-processing applications. 相似文献
6.
We present the measurements made on a medium power, 35 cm long, radio-frequency discharge CO 2 slab laser operated in a pulsed regime obtained by switching the RF discharge. In this way, pulses with peak power up to 480 W at pulse repetition frequencies in the range 1 to 10 kHz have been obtained. Pulse energy and average extracted power have been experimentally characterized with respect to the pulse repetition frequency and to the pulse duration, and the pulse shape and characteristic times have been measured. We also investigated the propagation properties of the beam emerging from our laser. 相似文献
7.
Five and six-temperature models for the CO 2–N 2–He system are used to describe the process of the dynamic emission in the TEA CO 2 laser. All physical constants and relaxation rates related to these models are examined to estimate the output pulse parameters as a function of the input parameters. The two pumping processes implemented; empirical function and differential equation show a good agreement with the experimental data. 相似文献
8.
A reliable procedure for remote high-accuracy laser detection of N 2O as one of the principal destroyers of the protective ozone layer of the Earth has been developed. The procedure is based on using a CO 2-laser system emitting efficiently in the 4.5 μm range. In this case lasing from isotopic modification 12C 18O 2 of carbon dioxide with its subsequent frequency doubling by a nonlinear crystal is used. With the object of reducing the price the composition of the active medium (both for TEA laser and low-pressure longitudinal-discharge-excitation laser) has been optimized. New high-efficiency intracavity frequency doubling schemes based on nonlinear AgGaSe 2 crystals have been developed for CO 2-lasers of both types. Low concentrations of N 2O and concentrations of the principal background gases CO and H 2O have been measured under real atmosphere conditions with the aid of the lidar complex built around these lasers. 相似文献
10.
A continuously variable attenuator for the CO 2 laser, causing minimal degradation of beam quality, is implemented using rotating ZnSe wedges, and is capable of transmissivities between 0.3% and 18%, and between 27% and 89%. The transmissivity at any particular setting was measured to be essentially constant for wavelengths from 9.27 μm (9R20) to 10.77 μm (10P36). 相似文献
11.
A CO 2 laser wavelength tuning system with microcomputer-controlled diffraction grating positioning is reported. The system employs a dc micromotor operating in a closed loop positioning servo and is characterized by simplicity of hardware. Fast wavelength tuning over a broad spectral range is achieved with the variable positioning speed technique. System performance is evaluated in conjunction with a TEA CO 2 laser. 相似文献
12.
A CO 2 laser rangefinder has been built that uses an acousto-optic modulator to obtain an amplitude modulated optical beam from a cw laser. An on-off deflected beam was obtained by driving the modulator with a carrier modulated by a periodic binary code. The received infra-red radiation was heterodyne detected. After envelope detection of the heterodyne signal, the signal-to-noise ratio was improved by applying a digital integrator. Ranging was carried out by calculating the delay of the received code by means of a cross-correlation technique. For this purpose a minicomputer was implemented in the system. Using 1 W average beam power and measuring times less than 1 s, ranges of several kilometers have been determined from stationary targets. 相似文献
13.
We report fifty seven CW FIR emissions observed in NH 3, by resonant pumping with a CO 2 laser. Exact coincidences between IR absorption lines of the gas and emission lines of the CO 2 laser have been carried out by Stark tuning. IR frequency shifts, up to 30 GHz, have allowed the pumping of forty three NH 3 transitions.These FIR emissions correspond to thirty one different wavelengths in the 50–400 m range; eighteen ones of them are new emitted wavelengths by pumping with the CO 2 laser. 相似文献
14.
The detailed mathematical models for the evolution of light pulses in RF-excited CO2 waveguide lasers are derived. Explicit expressions for the pulse characteristics in RF-excited CO2 waveguide lasers are obtained. The effects of losses and unsaturated gain on output power are calculated. 相似文献
15.
We describe an open resonator, quasi sealed-off; 70cm cavity length CO 2 laser with very high stability of power and frequency, which lases on 96 lines from 9R42 (2W) to 10P52 (5W) with a power
of >11W on 9R20, 9P20, 10R20 and 10P20, plus on 18 hotband lines with ≈2W. This laser was used successfully to pump an FIR
ring laser [1] enabling an FIR power stability of ΔP/P ≈ 10 −4 by use of a simple PI control loop, thus demonstrating its superb frequency stability. 相似文献
16.
An in situ mass-spectrometric sampling technique has been developed for lifetime studies of TEA CO 2 lasers. Using the new technique, an analysis of the gas components of a TEA CO 2 laser during its lifetime has been performed. The results show that the laser output pulse energy was strongly influenced by the oxygen concentration inside the device. 相似文献
17.
Temperature distributions along various hollow waveguides are fully analysed experimentally when the waveguides are excited by CO 2 laser light. It is shown that the temperature decreases in an oscillatory manner along the waveguides due to the interference effect of guided modes. The distributors are well explained by a theory developed previously. 相似文献
18.
Of all the types of lasers now available, the CO 2 laser is particularly suitable for materials working. It has a very high efficiency (15–20%) and a high out-put power (up to several kW). When the laser light is focused by means of a lens or a mirror, a c.w. power density of more than 10 9 W cm -2 can be attained. The laser need not be used in vacuum. The CO2 laser is a suitable cutting tool for numerous materials. These include metals such as titanium or steel; combustible materials such as paper, textiles and wood; and plastics. The CO2 laser can also cut hard and brittle materials such as aluminum oxide and silicon carbide. If metals are cut in an oxidizing atmosphere, the cutting speed may be increased. The cutting width, however, is determined by the size of the laser spot. Another important field of application is the growth of single crystals. Experiments are reported in which the CO2 laser was used for welding steel, titanium, plastics, quartz, and glass. The advantages of the laser for this application are discussed. A comparative study of laser and electron beam techniques is included. 相似文献
19.
Details of an experimental investigation of the output characteristics of the 1.2 kW cw transverse-flow, electrically excited CO 2 laser are presented. They were used for estimation of the saturation intensity and the laser cavity loss values, as they follow from the Rigrod-type model of laser operation. The saturation intensity parameter was calculated from measurements of the output power and small signal gain performed with the same experimental conditions. Measurements of the small signal gain were conducted at different points along the gas flow direction for several laser operational parameters described by gas pressure and input electrical power. 相似文献
20.
The use of a continuously tunable CO 2 laser to optically pump the NH 3 laser via previously inaccessible absorption lines is described. Efficient laser action has thus been achieved in the 11–13 μm region on transitions formerly only obtained in buffered mixtures. 相似文献
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