Single-frequency operation of a TEA CO2laser with a near orthogonally polarized injection signal

Injection mode selection of a TEA CO2laser was studied for injection signals polarized nearly orthogonal to the TEA laser output polarization. Single-mode operation was evaluated in an attempt to observe an anomalous effect attributable to the injection signal's polarization. The probabilities for single-mode operation were observed to be governed by the injection field component having minimum resonator loss.     

Sealed, miniaturized, corona-preionized, high-repetition-rate TEA CO2laser using hydrogen buffered gas mixtures

Sealed-off operation of a compact, corona-preionized, TEA CO2laser capable of efficient laser action at pulse repetition frequencies of up to 1 kHz is reported. By adding hydrogen to the basic gas mixture we have been able to maintain discharge stability and constant average output power for more than 20 million laser shots at a 400 Hz repetition frequency with peak powers in excess of 350 kW.     

Scaling laws for the intrapulse frequency stability of an injection mode selected TEA CO2laser

Heterodyne measurements of the intrapulse frequency behavior of an injection mode selected TEA CO2laser are presented. The frequency rose as the square of time at a rate varying linearly with energy and strongly dependent on spot size. These results are in accordance with a laser induced medium perturbative (LIMP) model, which allows the chirp in any TEA laser system to be predicted.     

Role of helium in TEA CO2lasers

The role of helium in TEA CO2lasers differs from that in low-pressure CO2lasers. TE CO2laser output is nearly proportional to the gain-bandwidth product, and, at a total pressure of 250 torr, it is independent of whether helium is present or not. Above 250 torr, the laser could not be operated without helium.     

A study of selective absorbers for single-mode operation of CO2TEA lasers

An investigation of the generality of intracavity selective absorbers for single-longitudinal mode operation of a high power CO2TEA laser has been conducted. SLM operation on 36 different CO2lines was obtained with 14 different selective absorbers. Typical off line-center tuning ranges are also reported. Maximum off line-center offset, limited by the detection equipment, was 300 MHz. These results demonstrate the method to be a general as well as a simple technique for applications requiring a SLM laser, and suggest that the method will have important device applications.     

Mode selection and frequency tuning by injection in pulsed TEA-CO2lasers

An analytical model is presented which describes certain characteristics of the injection locking of a pulsed TEA-CO2laser by means of tunable CW laser radiation. The requirements for SLM generation as the injection frequency is tuned away from line center are discussed. Results indicate the practical importance of the locking time, a parameter which depends on both the injected power and the detuning from the molecular line center frequency.     

Gain measurement in the CO2laser discharge

In order to examine the CO2laser oscillation mechanism, a measurement was made of the unsaturated gain of CO2laser radiation in an active medium of gas discharge containing CO2, N2, and He. A two-beam optical balance method was used to measure the gain in an amplifier; the accuracy of the measurement was approximately 10 percent. The output of a CO2-N2-He laser was used as the radiation source. The absolute power of the probing beam, which has a diameter of approximately 5 mm, was maintained at approximately 15 mW. Saturation was not observed at probing signal levels up to 80 mW. Amplifier tubes with diameters of 55, 34, 12, and 5 mm were used. The dependence of the amplifier gain on the current density, pressure, composition of the gas mixture, and tube diameter was measured. Comparison was also made of the calculated and measured values for the laser population inversion.     

Efficient multikilowatt mid infrared difference frequency generation in CdGeAs2

Multikilowatt mid infrared emission with high pump photon conversion efficiency (∼ 15 percent) has been obtained by difference frequency generation in CdGeAs2utilizing the double wavelength output from a grating tuned twin-cavity TEA CO2system, one signal of which is frequency doubled to provide efficient synchronized sources for both pump and idler. Tuning over a spectral range8-14 mum can be achieved and further extended to 17 μm using 12.8 μm emission from an efficient TEA CO2pumped NH3laser.     

Theoretical and experimental studies of a multiline TEA CO2laser with hot CO2as an intracavity absorber

The multiline behavior of a ballast resistance helical TEA CO2laser incorporating hot CO2as an intracavity absorber has been studied. Simultaneous laser oscillation onP(16), P(18), andP(20)lines of 10.6 μm has been obtained reliably. A rate equation model has been developed for the hot CO2absorber and is incorporated with the model for the multiline TEA CO2laser for calculating laser intensities onP(16), P(18), P(20), andP(22)lines of the 10.6 μm band in the presence of the absorber. The theoretical calculations agree quite well with the experimental observations. These studies show that a hot CO2column of Proper length and temperature inside a TEA CO2laser cavity can produce simultaneous laser oscillation on at least three rotational linesP(16), P(18), andP(20)of the 10.6 μm band with almost equal intensity.     

Single longitudinal mode operation of a CO2TEA laser by injection locking with a tunable CO2waveguide laser

A CO2TEA laser was frequency tuned by means of injection locking with a tunable waveguide laser as master oscillator, using a special injection method. Injection-locking experiments were performed at different operating conditions and varying parameters such as laser lines, master oscillator power, and frequency offset from the line center.     

Continuously tunable optically pumped high-pressure DF → CO2transfer laser

The operational characteristics of a continuously tunable DF → CO2transfer laser optically pumped with radiation from a pulsed DF laser are experimentally and theoretically studied. The pump radiation is absorbed by DF in a high-pressure DF/CO2/He gas mixture, and subsequent V-V energy transfer to the CO2ν3mode provides the CO2laser population inversion. Continuous tuning of the CO2laser frequency between five CO2line centers from 29.14 to 29.30 THz has been demonstrated, using a 12 atm gas mixture. The maximum pulse energy was about 0.8 mJ. In experiments with a two-mirror CO2laser resonator, pulse energies up to 6 mJ and 35 percent slope quantum efficiency have been obtained at 10 atm gas pressure. The gas mixture typically contained 0.5 percent DF, 5 percent CO2, and 94.5 percent He, but this was not critical. Computer simulations based on a rate equation model of the laser have given results which are in reasonable agreement with those obtained experimentally.     

Hybrid injection locking of higher power CO2lasers

Frequency stabilization of a higher power CO2ring laser by locking with a stable low-power reference laser is described. Successful locking is achieved by employing a novel hybrid injection-locking technique. In the hybrid mode, the higher power laser is tuned to operate on a self-oscillation line different from that of the reference laser. Within the frequency-locking range, the self-oscillation of the locked laser is completely quenched, and only the amplified drive power of the locking laser appears. Operation of this hybrid technique relies on the line competition in the homogeneously broadened CO2medium. The hybrid technique, which is easily implemented with a simple hill-climbing servo, permits stabilized operation over a variety of laser lines. An analysis of injection locking that explicity includes the saturation of the homogeneous medium is presented. Expressions are obtained for the gain and the phase relationships within and outside the locking region. To demonstrate the potential of the hybrid injection-locking technique, a 60-W CO2laser was locked in frequency to a 0.5-W stable oscillator. The experimental data are in close agreement with theory.     

High repetition rate TEA CO2laser

This correspondence reports on the successful operation of a TEA CO2laser at rates up to 1000 pps with an average output power up to 65 W over long periods of time. An essential feature of the present system is a rapid gas circulation transverse to the laser axis combined with a large volume of ambient gas. It is found that decomposition of the gas is one of the major problems at high repetition rates.     

4B2--Pulsed and steady-state infrared emission studies of CO2laser systems

Transient and steady-state infrared emission at 2.5 to 15 μ from low-lying vibrational-rotational levels of CO2has been studied using a dc discharge. The time-dependent behaviors of several levels important for laser excitation and relaxation were examined following a pulsed discharge. The decays were, in general, different and were not simple exponentials. Relaxation of vibrational energy of CO2appears to occur by collisions involving vibration-vibration exchange between different vibrational modes and vibration-translation relaxation of the bending mode. The rate of transfer of vibrational excitation from N2to various vibrational modes of CO2was investigated as a function of CO2pressure. The addition of He reduced the emission from the lower laser levels with respect to that from the upper laser level and increased the nonradiative decay rate of the lower vibrational levels by CO2-He collisions. Under pulsed excitation, in addition to CO2laser action nearly coincident with the pulse, a weaker, delayed output was observed.     

Collision effect on the saturation character of vibration-rotation transitions for 00°1-10°0 band of CO2

Experimental studies of collision effects on the saturation characteristics of vibration-rotation transitions for00deg1-10deg0 band of CO2is described. Saturation was studied in a passive absorption cell inside the laser resonator. The saturation value could be altered by varying the cell temperature and the pressure of CO2. Vibration-rotation transitions, at pressures greater than or equal to 1 mmHg, were found to be saturated homogeneously, in spite of the fact that the Lorenz width was much less than the Doppler width. This is explained by the high number of collisions during the lifetime in a vibrational state. In this case the spectrum of a single molecule corresponds to that of a Doppler profile. Cross sections for the destruction of levels of00deg1-10deg0by added gases have been obtained, which att = 800degK appeared to be σCO2-He =6 times 10^{-19};sigmaCO2-Ne =2.8 times 10^{-18}; sigmaCO2-CO2=6.6 times 10^{-18}; sigmaCO2-N2=1.2 times 10^{-17}cm²The introduction of sufficiently large absorption caused self-sustained radiation pulsation. When the field influenced the saturating system for only a short period of time, with the interaction time being commensurate with the period of time between collisions, the line was saturated nonhomogeneously. This was expressed by the fact that with the scanning of the laser frequency, a peak power output was observed, corresponding to Lamb's hole, in the center of a saturation line.     

Long-term operation of a sealed CO2laser

The life expectancy of a sealed CO2laser tube depends, to a great extent, on the interaction of the molecules existing in the discharge at the cathode. The data reported here indicates that after operation of a sealed laser, only CO and O2are formed in concentrations comparable to the initial fill gases of CO2, N2, and He. The CO, CO2, and O2, in particular, were found to be completely adsorbed at the Ni cathode within several hundred hours of tube operation. A loss of 10.6 μm power output accompanied this adsorption. As expected, the process was reversible to a degree since the laser resumed operation at the initial power level after the cathode region had been heated to 300°C. This process of adsorption-desorption was repeated several times up to an accumulated operating time of 705 hours. During this time, the power output remained at a substantially constant value. However, the loss of CO2by carbon deposits ultimately means an end to tube life.     

Optogalvanic stabilization and offset tuning of a carbon dioxide waveguide laser

A feedback loop employing the change in discharge impedance with output power is used to stabilize the frequency of a CO2waveguide laser. The relatively high operating pressure of the laser combined with a zero offset feature in the feedback loop allows continuous tuning of the stabilized frequency over a 300-400 MHz range.     

A radiatively pumped CW CO2laser

A proof of principle experiment to demonstrate the physics of a radiatively pumped laser has been carried out. For the first time, a blackbody cavity has optically pumped a CW CO2laser. Results are presented from a series of experiments using mixtures of CO2, He, and Ar in which maximum output power was obtained with a 20 percent CO2- 15 percent He-65 percent AR mixture. The dependence of the output power on the blackbody temperature and the cooling gas flow rate is also discussed. By appropriately varying these parameters, continuous output powers of 8-10 mW have been achieved.     

Ultraviolet preionized CO2TEA laser with high output power density utilizing nonconventional electrode profile

The performance of a very compact TEA CO2laser is described. The system utilizes simple circularly profiled electrodes and a single spark gap circuit for energizing both preioninizing and main discharges. An output power density in excess of 500 MW . 1^-1has been measured.     

Lasing in N2O and CO2isotope mixtures pumped by blackbody radiation

The use of N2O and CO2isotopes as active species for a blackbody radiation pumped laser has been experimentally demonstrated and theoretically analyzed. The results obtained for mixtures containing N2O,¹³C¹⁶O2, and¹²C¹⁸O2are presented. For the first time, continuous lasing action with blackbody radiation pumping has been obtained for this species. Two active species mixtures were tested, obtaining up to a 100 percent increase in output power due toupsilon-upsilontransfer. A simple model was developed and gain calculations are presented.