We have investigated the multi-spectral line output characteristics of a CO2 pulsed laser at multi-atmospheric pressure. The pulse waveforms, wavelengths, and energies of the output spectral lines and the small-signal gains of the full spectrum were measured at 3, 4, and 6 atm. To explain the experimental results and predict the output at higher pressure, a modified six-temperature multi-frequency dynamic model of the regular and sequence band lines was developed. The output spectrum varying from the 10P to 9R band with the increase of pressure was studied theoretically and experimentally. In addition, the gains of the 9R(16), 9P(16), 10R(16), and 10P(16) lines at 3 to 14 atm were simulated and measured, providing insights into variation regulation of the four band gains as pressure increases.
We demonstrated a periodically poled magnesium-oxide-doped lithium niobate (MgO:PPLN) optical parametric oscillator (OPO) pumped by a Nd-doped MOPA laser (1.064 μm) with a high peak power, tunable repetition rate, short pulse width. The OPO was designed as an extral cavity singly resonant OPO. By adopting optical pulse selection technology, the repetition rate could be adjusted in the range of 30-50 kHz without affecting the beam quality of the laser. The wavelength of output signal light was 1.57 μm when the polarization period and operating temperature of the MgO:PPLN were 30.5 μm, and 95 °C, respectively. In the range of 30-50 kHz, the pulse width of the laser was less than 4.9 ns and the average power was greater than 8.43 W. A maximum peak power of 63.9 kW was obtained at a repetition rate of 30 kHz, with a corresponding pulse width of 4.4 ns.
We present a cavity compensation technique based on a tunable long-wave infrared zinc germanium phosphide ZnGeP2 (ZGP) optical parametric oscillator (OPO). The slope efficiency increased from 3.6% to 7.0% at 9.15 μm after using the cavity compensation technique in the tuning range of 8.02 to 9.15 μm. We used a Q-switched 2.1 μm Ho:YAG laser pump source with a pulse repetition frequency of 10 kHz. Under the incident pump power of 23.03 W, the maximum average idler output power of 2.16 W at 8.02 μm was achieved with a pulse width of 21.5 ns and spectral bandwidth of 29.5 nm; the slope efficiency was 16.5%. To the best of our knowledge, this is the first application of the cavity compensation technique in tunable long-wave infrared ZGP OPO.
Diode pumped alkali laser (DPAL) with hydrocarbon buffer gases has the features of low threshold and high efficiency. The chemical reaction between alkali and hydrocarbon gases affects the life time of DPAL. In this paper, a method based on Fourier transform infrared spectroscopy and Lambert-Beer law is adopted to find a safe temperature at which DPAL runs for a long term. A theoretical model is established to figure out ways to reduce the peak temperature in the cell window. The results indicates that 170 °C is a safe temperature. Although the absorbance of the cell window to the pump light and alkali laser is lower, there is temperature increase. Small light-transmitting area and air blowing on the windows can reduce the peak temperature effectively. Cooling the cell window is essential and critical in a long-term running DPAL.
A continuous wave diode pump rubidium vapor laser (Rb-DPAL) is developed in this paper. It has long operating time at output power of 1 W. The Rb-DPAL, with optical efficiency of 18.9% and slope efficiency of 24.0%, has the characteristics of high stability and good beam quality. It is expected to be a kind of good pump source of SERF rubidium magnetometer.
A self-heated diode-pumped alkali laser (SDPAL) with a microfabricated alkali cell is proposed. Based on Beach’s model and finite-element analysis theory, the output characteristics of a cesium self-heated laser are studied. The results indicate that an SDPAL with a cell length of 2 mm is feasible. The output power of a typical SDPAL is ∼Watt level. Rapid heat convection around the mini cell can increase the output power. At the same time, the utilization ratio of the pumping light will decrease. A heating experiment is also conducted to validate the theoretical model. When pumping power of 0.69 W is illuminated on the light absorber, the cell temperature can reach 76.4°C with a single-side heated structure. The results show that with a mini vapor cell, SDPAL can be portable and competitive when ∼Watt-level laser with wavelength of alkali D1 line is required.
A theoretical model based on common pump structure is proposed to analyze the output characteristics of a diode-pumped alkali vapor laser (DPAL) and XPAL (exciplex-pumped alkali laser). Cs-DPAL and Cs-Ar XPAL systems are used as examples. The model predicts that an optical-to-optical efficiency approaching 80% can be achieved for continuous-wave four- and five-level XPAL systems with broadband pumping, which is several times the pumped linewidth for DPAL. Operation parameters including pumped intensity, temperature, cell’s length, mixed gas concentration, pumped linewidth, and output coupler are analyzed for DPAL and XPAL systems based on the kinetic model. In addition, the predictions of selection principal of temperature and cell’s length are also presented. The concept of the equivalent “alkali areal density” is proposed. The result shows that the output characteristics with the same alkali areal density but different temperatures turn out to be equal for either the DPAL or the XPAL system. It is the areal density that reflects the potential of DPAL or XPAL systems directly. A more detailed analysis of similar influences of cavity parameters with the same areal density is also presented.
A theoretical model based on common pump structure is proposed to analyze the laser output characteristics of DPAL (Diode pumped alkali vapor laser) and XPAL (Exciplex pumped alkali laser) in this paper. The model predicts that an optical-to-optical efficiency approaching 80% can be achieved for continuous-wave four- and five-XPAL systems with broadband pumping which is several times of pumped linewidth for DPAL. Operation parameters including pumped intensity, temperature, cell’ s length, mixed gas concentration, pumped linewidth and output mirror reflectivity are analyzed for DPAL and XPAL systems basing on the kinetic model. The result shows a better performance in Cs-Ar XPAL laser with requirements of relatively high Ar concentration, high pumped intensity and high temperature. Comparatively, for Cs-DPAL laser, lower temperature and lower pumped intensity should be acquired. In addition, the predictions of selection principal of temperature and cell’s length are also presented. The conception of the equivalent “alkali areal density” is proposed in this paper. It is defined as the product of the alkali density and cell’s length. The result shows that the output characteristics of DPAL (or XPAL) system with the same alkali areal density but different temperatures turn out to be equal. It is the areal density that reflects the potential of DPAL or XPAL systems directly. A more detailed analysis of similar influences of cavity parameters with the same areal density is also presented. The detailed results of continuous-wave DPAL and XPAL performances as a function of pumped laser linewidth and mixed gas pressure are presented along with an analysis of influences of output coupler.
Thermal control of the volume Bragg grating (VBG) in the LD with the external cavity is critical for the tuning of the wavelength and the narrowing of the bandwidth. Based on finite element theories, thermal properties of the VBG were researched under different conditions of LD illumining area, laser power, gratings’ working temperature and heat convection. Both the VBGs in the external cavity of LD bar and LD stack were considered in the experiments. The results show that higher working temperature of the VBG and adopting better heating convection cooling methods is beneficial to realize the uniformity of the VBG temperature distribution.
Thermal control of the volume Bragg grating (VBG) in the laser diode (LD) with the external cavity is critical for the tuning of the wavelength and the narrowing of the bandwidth. Based on finite element theories, thermal properties of the VBG were researched under different conditions of the LD illuminated area, laser power, gratings’ working temperature, and heat convection. Both the VBGs in the external cavity of the LD bar and stack were considered in the experiments. The results show that higher working temperature of the VBG and adopting better heat convection cooling methods are beneficial to realize the uniformity of the VBG temperature distribution.
In this paper, on the basis of the theory of quasi phase matched, CO2 laser spectrum corresponding to GaAs chip within the scope of the matching length was calculated. Through the numerical solution of the wave equation, the relationship between power density of pump laser and frequency doubling conversion efficiency was given under the different crystal length conditions. By adjusting the CO2 laser gas mixture components, we optimized the pump laser pulse wave to meet the requirements in the temporal distribution of the pump light. On the other hand, we optimize the output beam mode to meet the pump light distribution in space requirements. We use the tunable TEA CO2 laser as the light source to pump quasi phase matching GaAs crystal, When the pump wavelength is changed from 9.23μm to 10.75μm range, the conversion efficiency of frequency doubling output is greater than 4%, when the pump wavelength is 10.68um, the frequency doubling efficiency reached 6.58%.
We report a quasi-CW linearly-polarized rubidium vapor laser. The pumping source consists of 5 laser diode bars and its linewidth is reduced from the raw 1.8 nm to 0.2 nm by a bulk Volume Bragg Grating (VBG). Instead of adopting the “quasi-waveguide structure” gain cell, the pumping light of the rubidium vapor laser propagates freely in the vapor cell. The pumping light with polarization perpendicular to one of the rubidium laser is coupled into the resonator cavity by the PBS. Output power of 10 W with good beam quality is realized. This laser configuration is suitable for a convection-cooling DPAL.
We report a quasicontinuous wave (CW) linearly polarized rubidium vapor laser. The pumping source consists of five laser diode bars and its linewidth is reduced from the raw 1.8 to 0.2 nm by a bulk volume Bragg grating. Instead of adopting the “quasi-waveguide structure” gain cell, the pumping light of the rubidium vapor laser propagates freely in the vapor cell. The pumping light with polarization perpendicular to one of the rubidium laser is coupled into the resonator cavity by the polarized beam splitter. This laser configuration is suitable for a convection-cooling diode-pumped alkali vapor laser.
A compact transversely excited atmospheric (TEA) CO2 laser with high repetition-rate was reported. The size of the laser is 380 mm×300 mm×200 mm, and the discharge volume is 12×103 mm3. The laser cavity has a length of 320mm and consists of a totally reflective concave mirror with a radius of curvature of 4 m (Cu metal substrate coated with Au) and a partially reflecting mirror. The ultraviolet preionization makes the discharge even and stable,the output energy can be as high as 28 mJ under the circumstance of free oscillation, and the width of the light pulse is 60ns.To acquire the high wind velocity, a turbocharger is used in the system of the fast-gas flow cycle. When the wind speed is 100m/s, the repetition rate of the transversely excited atmospheric CO2 laser is up to 2 kHz. On this basis, a dual modular structure with two sets of the gas discharge unit is adopted to obtain a higher pulse repetition frequency output. The dual discharge unit composed two sets of electrodes and two sets of turbo fan. Alternate trigger technology is used to make the two sets of discharge module work in turn with repetition frequency of 2 kHz, the discharge interval of two sets of the gas discharge unit can be adjusted continuously from 20 microseconds to 250 microseconds. Under the conditions of maintaining the other parameters constant, the repetition frequency of the laser pulse is up to 4 kHz. The total size of laser with dual modular structure is 380mm×520mm×200mm, and the discharge volume is 24×103 mm3 with the cavity length of 520mm.
A novel external cavity with double volume Bragg gratings is approved in this paper. The linewidth of the LDA with the
external cavity can be tunable through controlling the temperature differences of the two VBGs, while the output power
changed no more than 4%.
Momentum coupling coefficients of TEA CO2 laser pulses for a parabolic aluminum shell were investigated. Momentum
coupling coefficients were measured with a pendulum in a chamber, the energy of the incident laser pulse was varied
from 8.3J to 50.9J, and the gas pressure in the chamber was changed from 100 kPa to 20 kPa in our experiments.
Experimental data were analyzed thoroughly. It was found that the coupling coefficients under the air pressure of 100kPa
decreased very slowly from 242 N/MW to 170 N/MW for the incident energy from 50.9J to 15.1J but decreased sharply
for the energy between 15.1 J to 13.8 J. And it was different for the air pressure below 100 kPa. Indoor free flight of our
parabolic shell was also analyzed, coupling coefficients and some other parameters were deduced from the experimental
data.
KEYWORDS: Electrodes, Carbon dioxide lasers, Gas lasers, Switches, Power supplies, Capacitors, Pulsed laser operation, High power lasers, Fluctuations and noise, Mirrors
A high average power TEA CO2 laser employing rotating spark gap switch is described. Average power up to 12kW has
been achieved at the repetition rate of 400Hz.
A new type of high repetition rate TEA CO2 laser with rotating spark gap as a discharge switch has been developed. The laser has potential ability of scaling up to very high energy and average power. In this paper, we report the recent progress in basic research.
High power high repetition rate TEA CO2 laser has potential importance in material processing such as shock hardening, glazing, drilling, welding, and cutting for high damage threshold materials, as well as in chemical reaction and isotope separation. This paper describes a transverse-flow closed-cycle UV-preionized TEA CO2 laser with peak pulse power of 20 MW, maximum average power of 1.5 KW at repetition rate of 300 HZ. The laser has compact constructure of gas flow circulation system using tangential fans. With addition of small amounts of H2 and CO to the normal CO2-N2-He gas mixture, one filling sealed operating lifetime is up to millions of pulses. A novel spark gap switch has been developed for very high repetition rate laser discharge in the condition of high pulse power.
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