Laser Tube Research Articles

Effects of additive hydrogen on kinetics mechanisms of CuBr lasers

Kinetics mechanisms of additive hydrogen in CuBr lasers are studied systematically. There are two important factors to increase laser power after adding hydrogen. (i) The gas temperature and CuBr density at the center of the laser tube are reduced; this decreases the collision energy depletion of the electron and leads to an increasing electron temperature. (ii) The electron density increases during pulse, the skin effect of the electron and the “black center” of the laser are improved.

He-Kr laser with a modified helical hollow cathode

A pulsed He-Kr laser with a helical hollow cathode is investigated. A modified cathode is proposed. The modification involves making the cathode coil from a ribbon-shaped material. The design of the cathode chosen allows one to obtain appreciable lifetime of the laser tube and to reach repetition rates up to 1 kHz. Lasing on the KrII 469.4 nm and KrII 431.8 nm lines is obtained from 265 mm active length and gain coefficients of 25% m-1 and 14% m-1, respectively are measured at 8 A peak current. It is demonstrated that the ambipolar diffusion of Kr ions, as well as the specific helical shape of the cathode, are causes for the pulsed mode of laser operation.

Micron-image transfer system with brightness amplifier in gold-vapor laser

A gas-discharge gold-vapor laser on self-terminating transitions with operating wavelength λ=312.2 nm has been used to develop a highly efficient system for image transfer. An optical scheme and all its parameters have been chosen optimal for image quality. It has been found both theoretically and experimentally that the best results on micron-structure image transfer are obtained with 2–5-times image reduction. Various types of masks have been used. A 1-µm structure has been resolved due to the choice of optimal exposure time of 10 ms under a period of pulse repetition (0.6 – 0.8) ms; in this case, the minimal fringe dimension was ≈2 µm with an image dimension of 2 mm for a laser tube 1.8 cm in diameter.

Dependence of gain and laser power for Cu-II 780.8-nm transition on the diameter of a segmented hollow cathode discharge

The dependence of laser performance and discharge characteristics on the diameter of a segmented hollow cathode discharge for the Cu-II 780.8 nm transition is presented. This transition has a special importance since its upper level is common to potential CW VUV laser transitions (150-170 nm). Laser tubes with internal diameters of 2, 3, 4, and 5 mm were investigated. Decreasing the diameter resulted in an increased gain for a given current (up to 100 %/m in the 2-mm diameter, 5-cm-long tube at 1-A current). The highest output power was obtained from the large-diameter tubes (20 mW from a 5-cm-long, 5-mm-diameter tube at 2-A current, without optimizing the output coupler). This work is a part of a series of investigations aimed at the optimization of the segmented hollow cathode discharge which has already been found to be the most efficient type of discharge for cathode sputtered metal ion lasers. >

CW radio-frequency excited white-light He-Cd/sup +/ laser

We report on the design and performance of a continuous-wave transverse capacitively coupled radio-frequency excited He-Cd/sup +/ laser, which is capable of simultaneously delivering stable, tens-milliwatt power output at the three primary spectral lines blue: (/spl lambda/=441.6 nm), green (/spl lambda/=533.7 nm and /spl lambda/=537.8 nm), and red (/spl lambda/=635.5 nm and /spl lambda/=636.0 nm). Mixing these lines can result in the laser beam featured by a wide band of colors, including white color. The radio-frequency discharge, that excited the He-Cd mixture inside an alumina ceramic tube (400 mm length and 4 mm inner diameter) inserted into the fused silica tubing, operated between 400 mm long and 4 mm wide outer electrodes. Transformation of the radio-frequency discharge impedance to the 50-/spl Omega/ output resistance of the radiofrequency generator and symmetrization of the radio-frequency voltage were performed by a special matching circuit. Under single-line operation the He-Cd/sup +/ laser output powers of 60 mW, 38 mW and 14 mW were obtained for the blue, green and red lines, respectively, at an input radio-frequency power of 400 W. Owing to the power interaction between the laser oscillations at red and green higher laser output powers in red and green are possible under multi-line operation. At optimum conditions the white-light laser output power of about 60 mW is obtainable from the laser tube of 40 cm active length. The rms noise-to-signal ratio (lower than 0.4%) of the laser output power of the radio-frequency excited He-Cd/sup +/ laser was comparable to that of hollow cathode He-Cd/sup +/ lasers and much lower than that of conventional positive column He-Cd/sup +/ lasers. The presented laser has exhibited stable operation for more than 400 hours, showing ability to become a long life laser.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Long Life Operation of a Copper Vapor Laser.

The operating life of a copper vapor laser (CVL) with a 6 cm diameter / 200 cm discharge length laser tube has been successfully extended and continuous operation for 320 hours at an output power of 75 ~ 10 W has been demonstrated. With a view to improving the long-term performance and reliability of CVL operation, this paper reports the experimental results of investigating the relationship between copper loss rate and buffer gas condition (flow rate and pressure) . Also discussed are the optimum laser operating conditions for minimizing copper 10ss. Average thyratron life has also been extended to 1,000 hours or more by using the magnetic assist technique for the CVL pulsed power supply.

Use of the beat frequency between two modes for frequency stabilization of internal-mirror lasers

We present a simple method of frequency stabilization of a laser with two orthogonal modes that uses the effects of anomalous dispersion at the active line. The result of this effect is that the frequency difference between oscillation modes varies during the frequency tuning along the Doppler line of the transition and has its minimum or maximum when the modes are symmetrically placed around the central part of the gain curve. We applied the semiclassical approach to describe the laser, and we established the rules for laser parameters to obtain the most convenient conditions for stabilization. We stabilized the thermally compensated experimental laser tube and reached frequency stabilities of 3 × 10(-9) and 3 × 10(-10) for integrating times of 1 and 134 s, respectively.

Frequency Locking of 543 nm He–Ne Laser on Iodine Spectrum

Frequency tuning of internal-mirror 543 nm He–Ne lasers was realized using a piezo-electric transducer (PZT) through an elastic deformation of the laser tube. Two 543 nm He–Ne lasers were locked on the saturated absorption lines of iodine with the third-derivative signal of a signal-to-noise ratio of about 50. From the beat signal between them the frequency stability was measured to be σ(τ, 2)=1.2×10-11τ-1/2(10-4 s<τ<10 s).

Development of 200W High-Performance Copper Vapor Laser with 6cm Diameter, 300 cm Length.

A copper vapor laser (CVL) with 6 cm diameter and 300 cm discharge length has been developed for atomic vapor laser isotope separations. Recently, output power of over 200 W (211 W maximum) has been steadily obtained. The authors developed a thermal calculation code to maintain an optimum copper vapor density throughout a large volume and a discharge analyzing code to supply discharge energy efficiently into the laser tube. Connecting these codes to Kushner's CVL simulation method yields results which agree well with experimental results. And high-performance CVL could be designed by these codes which simulated the thermal and electrical characteristics of a CVL. In addition, a new thermal insulation structure design method has been proposed to combine two different heat insulators to make longitudinal temperature distribution of the laser tube as flat as possible. A CVL discharge circuit has been improved by applying an excellent magnetic assist which has been able to operate at high repetition rate (5 k...

Cooling effects induced by stimulated emission in the discharge of CO 2 lasers

The gas temperature distribution in a CO 2 laser tube with longitudinal dc excitation is investigated by means of an infrared camera. The heat-conduction equation including a loss term with gaussian profile can model the experimentally observed cooling effect induced by stimulated emission.

Development of 200 W High-Performance Copper Vapor Laser with 6 cm Diameter, 300 cm Length

A copper vapor laser (CVL) with 6 cm diameter and 300 cm discharge length has been developed for atomic vapor laser isotope separations. Recently, output power of over 200 W (211 W maximum) has been steadily obtained. The authors developed a thermal calculation code to maintain an optimum copper vapor density throughout a large volume and a discharge analyzing code to supply discharge energy efficiently into the laser tube. Connecting these codes to Kushner's CVL simulation method yields results which agree well with experimental results. And high-performance CVL could be designed by these codes which simulated the thermal and electrical characteristics of a CVL. In addition, a new thermal insulation structure design method has been proposed to combine two different heat insulators to make longitudinal temperature distribution of the laser tube as flat as possible. A CVL discharge circuit has been improved by applying an excellent magnetic assist which has been able to operate at high repetition rate (5 kHz) oscillating condition. This paper reports such CVL design methods together with the performance of the designed high-power CVL.

CuBr-CsBr-Ne laser with high-repetition-frequency; relaxation control by energy acceptor

A trial experiment for promoting the relaxation of the lower laser level in the metastable state of a CuBr-Ne lasing system has been carried out by mixing CsBr as an energy acceptor from the metastable state. A tiny homemade laser tube whose average output power was around 1.5 W was employed. The lasing efficiency, was improved by a rate of about 30 percent and the repetition frequency of pulsed operation reached 55 kHz. The effectiveness of Cs as the energy acceptor was explored, taking into account the numerical checking on the electronic and atomic impact phenomena in the discharge plasma, as well as the measurement of the radiative decay time of the atomic line spectrum of the Cs(I) at 894.4 nm. >

Quenching A-coefficients by photons in a short discharge tube

New experimental results on quenching of A-coefficients by photons in a short discharge tube are presented. Experiments with the short discharge tube have eliminated questions related to the effects of absorption in a long laser tube, and have provided good confirmation of earlier results.

Stabilization of a multimode He–Ne laser: A vivid demonstration of thermal feedback

A thermal stabilization technique for multimode He–Ne laser tubes is demonstrated. Intensity stability of ∼1% is achieved, where the intensity of the unstabilized laser varied by more than a factor of 5. The system provides both a dramatic demonstration of the principle of negative feedback and a stimulating introduction to basic electronics, laser physics, and solid state physics. It is simple enough to be constructed as an undergraduate laboratory project.

Chemistry of iodine photodissociation lasers at the pyrolytic regime

The temperature regime, in which iodine photodissociation lases operate, depends on the UV pumping intensity and on the heat capacity of laser mixture. Even though low temperatures are preferred, pyrolysis conditions are reported, too. To distinguish between the nonpyrolytic and pyrolytic regimes, a simple experimental method of finding the pyrolysis limit was suggested. The chain of processes, which may supplement the pyrolytic decomposition of C 3F 7I as a laser gas, is reported. Special attention was paid to the production and reactions of different kinds of radicals. Moreover, possible reactions of exposed gas mixture with laser tube construction materials and with gaseous impurities are also discussed.

A portable iodine stabilized He-Ne laser and its use in an absolute gravimeter

A portable, robust, and easy to use iodine-stabilized laser operating at a wavelength of 633 nm was realized at the BIPM. The size of the laser and its electronic servo are such that they can be installed in a suitcase having dimensions acceptable in an aircraft cabin as hand baggage. The performance of this laser is comparable to that of stationary lasers. A frequency repeatability of a few parts in 10/sup 11/ and a frequency stability that can reach 2 parts in 10/sup 13/ on a 300-s sample time are achieved. The radiation emitted by the laser can be used as a reference for optical interferometry for several years without the need for periodic calibration and its life is limited by that of the laser tube. A prototype was installed in an absolute gravimeter and continuous sets of g measurements extending over more than 30-h periods were achieved with standard deviations on the average value of g of about 2.5 parts in 10/sup 8/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A pulsed iodine photodissociation laser with slow pumping

A construction and exploitation of a comparatively large I photodissociation laser system (Perun) is reported. This system was constructed in cooperation between the Institute of Physics of Czechoslovak Academy of Science in Prague and the Lebedev Institute of Physics of Soviet Academy of Science in Moscow. The laser produces subnanosecond pulses of maximum 50 J and 0·5 ns in duration. Although the pumping time by Xe flashlamps is long enough for an acoustic disturbance released in the active medium to introduce an optical inhomogeneity across the whole cross section of the laser tube, the radiation can be focused in a focal spot of a power density exceeding 1014 W/cm2, enough for meaningful laser target experiments both for a laser plasma production or a modification of solid surfaces. The repetition time of the shots is about 10 min.

Phase control of a Zeeman-split He–Ne gas laser by variation of the gaseous discharge voltage

Zeeman-split lasers are useful for precise positioning or motion control. In applications that employ such a laser to control closely the position of a moving system, phase noise in the Zeeman frequency is a serious problem. Control of low-frequency phase noise can be obtained through variation of the external magnetic field by way of a solenoid wound around the laser tube. It is the finding in this work that control of the residual higher-frequency noise of a He-Ne laser can be obtained through small variations of the high voltage that is used to effect the gaseous discharge in the laser tube. The application of the present system is to the control of the path difference in a Fourier-transform interferometric spectrometer.

An argon ion ring laser as a gyroscope

As a prototype gyroscope for a precision measurement of the Earth's rotation ΩE, we set up an argon ion ring laser with an area of 1.4 m2. Different cavity geometries were tested in order to achieve a cancellation of the effect of the plasma flow. In a set-up with two laser tubes of the same type facing towards opposite directions, a stability of the beat frequency of 2–3 ΩE was measured. In a configuration with a double transition of the laser beam through the tube, the lock-in threshold was too high for the Earth's rotation to be measured, however, no effect of the plasma flow was observed.

The pattern of mode competition between two frequencies produced by mode split technology by tuning of the cavity length

A new method is used for studying the mode competition of HeNe lasers. The method used is: (i) to make a small frequency split by using laser longitudinal mode split technology, (ii) to tune the cavity length in order to move the two mode split frequencies along the frequency axis and (iii) to use different ration between 20Ne and 22Ne in the laser tubes. In some ranges of lasing bandwidth, one mode split frequency will extinguish due to mode competition. And in other ranges, two mode split frequencies will work altogether. At the boundary between these two ranges, the process of intensity variation, from zero to maximum or in the opposite direction, of the split frequencies can be seen clearly. The pattern is dependent on the ration between 20Ne and 22Ne.