Frequency-tunable optically pumped carbon monoxide laser

Single-line frequency-tunable lasing was observed in an optically pumped, repetitively pulsed, room-temperature CO laser for the first time. The R(0) and R(7) ro-vibrational transitions in the (2,0) overtone of CO at 2.3 μm were optically pumped with a high-energy optical parametric oscillator. Single-line lasing was observed on (2,1) P(2)-P(17) transitions and R(0)-R(11) transitions (covering wavelengths within the range 4.6-4.9 μm) when using a diffraction grating as the spectrally selective reflector of the laser resonator. The observed CO laser pulse lengths were ~10^-7 s with peak power up to 10⁴ W. The influence of CO pressure, the addition of buffer gas (He, Ar), Q-factor of the laser resonator, and the pump pulse energy on CO laser pulse temporal characteristics and output energy spectral distribution was studied experimentally     

New HF laser pumped molecular lasers in the middle infrared

Stimulated emission has been observed in five molecules optically pumped by a pulsed HF laser. Emission was observed in¹⁵N2O,¹⁴N¹⁵NO, and¹⁵N¹⁴NO at 4.6 μm, HCOOH at 5.7 μm, and in¹³CS2at 6.9 μm. Lasing pulse shapes and delays after the pump pulse were measured. Lasing due to rotational relaxation induced by collisions with He was observed in¹⁵N¹⁴NO.     

Observation of a large number of new laser lines from12CD3F gas optically pumped with a continuouslytunable high-pressure pulsed CO2 laser

An observation is reported of a large number of new laser lines from ¹²CD₃F gas optically pumped with a continuously tunable high-pressure pulsed CO₂ laser. Making use of the coincidence of the 10 μm P and R branches of CO₂ with the v₃ and v₆ vibrational-rotational absorption bands of ¹²CD₃F, 180 laser lines were found in the wavenumber range between 8 and 55 cm^-1, all of them yet unknown; these lines are studied for characteristic properties of laser action. All laser lines are assigned as pure rotational transitions in the vibrational excited or ground states     

A 170 J electron beam pumped XeF(C→A) laser

A pulse output energy of 170 J has been achieved from an XeF(C→A) laser system, pumped by a pair of counterpropagating, three-meter-long electron beams. This represents a record for all types of pumping, for this excimer system. Energy was extracted from a volume of ~100 L, using a free-running stable oscillator. No evidence of laser oscillations on the competing XeF(B→X) transition was observed. Within the extraction volume the laser gas was pumped at a rate of 140 kW/cm³ (time average value), for a period of 1.7 μs. The optical cavity was folded, giving a gain length of 6 m. The optical pulse duration was 0.8 μs (full width at half maximum), and the observed flux buildup time of ~1 μs was consistent with modeling and a measurement of the net gain. The specific output energy was 1.7 J/L which is comparable to that achieved in previous, small scale experiments at somewhat higher pump rate. The results confirm the volumetric scalability of the electron beam pumped XeF(C→A) laser system to high output energy per pulse, and the feasibility of operating this system at a low electron beam pump rate which relaxes constraints on the design of the electron gun and pulse power subsystems in a high output energy device. Means for extending the laser pulse duration and increasing the output energy of the specific test device are discussed. An output energy of ~1000 J is projected for an optimized gas cell width, for full size resonator mirrors, and with injection     

Dither-free absolute frequency locking of a 1.3 μm DFB laser on87Rb

A technique for frequency locking a semiconductor laser in the 1.3 μm region by observing the absorption in a ⁸⁷Rb vapor optically pumped by another frequency-modulated semiconductor laser is presented. This technique offers well-defined strong atomic resonances and does not require frequency dithering of the 1.3 μm laser to observe the discrimination pattern required for frequency locking. Dither-free absolute frequency locking of a DFB (distributed feedback) laser at 1324 nm was achieved using a pump laser diode operating at 795 nm (D₁-line). Applications include master oscillator of multiwavelength and coherent communication systems and reference source for an optical frequency synthesizer. Resonances in the 1.55 μm region are also available through this approach     

光泵CH3F和D2O远红外脉冲激光器

自1970年T.Y.Chang报道了光泵CH_3F远红外激光器以来,至今已发现有几十种工作物质,可在远红外波段产生1000多条激光线。远红外激光器有广泛的应用,在等离子体诊断中,通过Thompson散射,可确定Tokamak中离子密度和温度;在半导体中,可用来确定载流子浓度和杂质浓度;作为标准波长,可构成频率链的一环;在军事上,远红外激光可用于亚毫米通讯;用远红外激光照射石英晶体,可产生频率为几THz的声子,在     

New short-wavelength laser emissions from optically pumped 13CD3OD

We report the discovery of 15 new laser emissions from ¹³ CD₃OD when optically pumped with a CW CO₂ laser. The wavelengths of these lines, ranging from 57.5 to 135.2 μm, are reported along with their polarization relative to the CO₂ pump laser, operating pressure and relative intensity. A three-laser heterodyne system was then used to measure the frequencies of 12 optically pumped laser emissions from this methanol isotope. These emissions range from 65.7 to 151.8 μm and are reported with fractional uncertainties up to 2·10^-7     

光泵CF4 16微米激光器

本文介绍了由 TEA CO_2激光器的9R(12)跃迁线泵浦冷却的 CF_4分子,获得 16μm激光输出。泵浦光用限孔光阑得到TEMoo单横模,由低气压CO_2增益池压缩线宽,并与光泵腔良好的模式匹配下,以700mJ的泵浦源能量获得25mJ左右的16μm激光输出能量。光量子转换效率达7％左右。激光脉宽窄于150ns,该器件可在约0.5Hz重复率下,以20mJ的输出能量运转数千次。     

Praseodymium-doped fiber amplifiers: theory of 1.3 μm operation

A theoretical model of optical amplification in a praseodymium-doped fiber amplifier that is optically pumped at about 1 μm and amplifies signals at about 1.3 μm is presented. The variation of gain with respect to fiber length in both small-signal and saturated operation is reported, and the adverse influences of a lower-level bottleneck and a multiphonon cascade from the pump band are discussed     

1.5-μm InGaAs/InAlGaAs quantum-well microdisk lasers

Microdisk lasers with three InGaAs/InAlGaAs quantum wells were demonstrated for the first time. The selective etching method used to fabricate the laser structure is discussed. Lasers 20 μm in diameter lased with single mode at 1.5-μm wavelength when optically pumped by a pulsed argon-ion laser at 80 K     

Performance and Spectral Tuning of Optically Overtone Pumped Molecular Lasers

A laser model was developed to predict the performance of optically pumped higher overtone molecular lasers under pulsed and continuous wave (CW) excitations. This model takes into account up to 30 rotational levels in each of the eight vibrational states considered. Collision-induced relaxation among rotational levels, vibrational levels, energy transfer to translational degrees of freedom, and interactions with buffer gas, and the temperature dependence of these processes are included. Using parameters for a second overtone pulse pumped HBr laser, a complete lasing cascade can be expected at a certain pump pulse fluence resulting in maximum achievable efficiencies approaching 80%. Optimum operational pressure and temperature conditions are determined by the gas kinetic rates and line broadening effects. Frequency tuning and spectral narrowing of the laser output is possible with the insertion of intracavity filters without sacrificing laser output power owing to efficient energy redistribution between rotational levels mediated by appropriate buffer gases. CW lasing using waveguide (WG) like geometries is possible with efficiencies approaching 92% for first overtone pumped lasers. Heat conduction through the active gas enhanced by buffer gases and subsequent heat dissipation through the cooled WG walls are expected to handle the thermal load up to kW output power levels.     

Tunable te-CO2 laser-pumped formaldehyde far-infrared lasers: Offsets,assignment, and superfluorescence

Sixty and three absorption transitions in D₂CO and H₂CO, respectively, have produced a number of far infrared laser lines when they are pumped by an etalon-tuned TE-CO₂ laser. Almost all the absorption transitions pumped previously by a free runing TE-CO₂ laser have been efficiently pumped by the etalon tuned CO₂ laser and found to have offset within ±500 MHz from the line-center of the relevant CO₂ pump lines. 22 (1) absorption and 63 (4) emission lines of D₂CO (H₂CO) are assigned. Some of these lines have generated superfluorescence. In paticular, the D₂CO 319-μm line pumped by CO₂-9P(32) delivered an output energy of approximately one half that of the well-known D₂O 66-μm. It is shown that a large electric dipole moment and an appreciable amount of fractional population in the lower level of the pump transition of this line are responsible to the superfluorescence.     

Diode-pumped Nd:YAG laser producing 122-W CW power at 1.319 μm

A high-power diode-pumped Nd:YAG laser oscillating at a wavelength of 1.319 μm is reported. A 122-W CW laser beam with an M2 factor of 35 has been achieved with an optical efficiency of 19.6%. The lasing characteristics, including thermal lensing, at 1.319 μm are compared with those at 1.06 μm. Under lasing conditions, the focal length of thermal lensing at 1.319 μm decreases by 25% and increases by 15% at 1.06 μm with respect to the nonlasing conditions. Based on the experimental results, the heat dissipation in an Nd:YAG rod is discussed with reference to nonradiative transitions from the upper laser level     

Buffer gases to increase the efficiency of an optically pumped far infrared D2O laser

The effects of buffer gas additives on the performance of an optically pumped D2O laser operating at 385 μm have been investigated both experimentally and by numerical simulation. Three gases, sulphur hexafluoride, carbon tetrafluoride, andn-hexane, were found to produce an increase of up to 40 percent in the pumping efficiency, as well as significant lengthening of the far infrared pulse. Under optimum conditions, 2.6 J in a 1 μs long pulse have been obtained. The buffer gases are shown to eliminate the vibrational deexcitation bottleneck, which in pure D2O leads to an accumulation of population in the upper vibrational leve and, hence, a reduction in the efficiency of absorption of the pump beam. Comparison of the observed buffer gas effects with the predictions of a numerical simulation code based on a rate equation model gives information about the constants for vibrational and rotational relaxation rates due to D2O-D2O and D2O-buffer gas collisions.     

Compact high-energy Q-switched cladding-pumped fiber laser with atuning range over 40 nm

We describe a compact Q-switched diode pumped double-clad ytterbium-doped fiber laser. The fiber laser was bidirectionally pumped by two laser diodes (2 W of output power each) via two side-injecting pump-couplers. We used a large multimode core of 15 μm diameter to increase the laser gain volume and thus to achieve higher pulse energy. Experimentally this laser produced pulses with energy up to 170 μJ with a peak power of 2 kW (at a low repetition rate of 500 Hz) and was tunable from 1060 to 1100 nm     

Spectral characteristic study of Raman transition interaction in optically pumped FIR laser

The spectral characteristic of an optically pumped NH3 molecules FIR laser has been studied by a F-P interferometer and a Michelson interferometer. It was verified that when NH3 molecules were pumped by CO2-9R(16) line, a emission by Raman transitions of two photons was produced. When the gas pressure of NH3 increased, the interaction of the Raman transitions rose, then the emission was enhanced and the width of spectral lines were broadened. The experimental results are in good agreement with the theoretical calculations.     

Observation and characterization of new FIR laser lines from formicacid

We report the observation and characterization of seven new far-infrared (FIR) laser lines from H¹²COOH and H¹³COOH in the range 232.2 to 746.6 μm optically pumped by a wide-tunability waveguide CO₂ laser. Their absorption frequency is outside of the tuning range of a conventional CO₂ pump laser     

Theoretical modeling of relaxation oscillations in Er-dopedwaveguide lasers

An analysis of relaxation oscillations (λ_s~1.5 μm) in locally Er-doped optically pumped (λ_p~1.48 μm) waveguide lasers is reported. The theoretical model is based on time dependent rate equations for a quasi-two-level-system and on the equation of continuity for a gain medium. For the first time a numerically reliable simulation of the elementary properties of the laser oscillations was possible: the build-up time and decay of the relaxation oscillations, the time-dependent repetition period, the steady state signal output power and the evolution of the pump power versus time. Mathematically the problem can be characterized as a large boundary value problem, which can approximately be replaced by a stiff initial value problem of ordinary differential equations. In this report, pump- and signal evolution versus time are presented for planar Er-diffused Ti:LiNbO₃ waveguide lasers. The numerically obtained results show a good quantitatively agreement with experimental investigations     

Dynamics of a mode-locked low-pressure photolytic I* laser

A longitudinally pumped photolytic iodine laser has been reliably mode-locked over a broad range of iodide pressures (1-30 Torr). Average mode-locked pulse widths ranging from 1.4-2.5 ns were observed as a function of CF₃I iodide pressure and added buffer gas (Ar). Low-pressure data indicate an increased gain bandwidth as a result of an initial nonthermal I* atom distribution following rapid (<20 ns) photolysis of the parent molecule, CF₃I. Nearly 1.75 eV of excess pump energy is available and is deposited into the internal vibrational and rotational degrees of freedom of the large radical and into the translation of the nascent iodine atom, allowing for high iodine atom velocities in the frame of observation. A diode laser system tuned to the 3-4 transition of spin-orbit excited iodine atoms was used to observe the time-dependent behavior of line center gain along the optical axis. Preliminary data indicate an I* atom velocity relaxation on the order of 1 μs for an iodide pressure of 1 Torr, and approximately 300 ns for a pressure of 10 Torr. At 5 Torr of CF₃ I, the laser mode build up time is 200 ns, allowing access to the increased gain bandwidth and resulting in mode-locked pulse widths less than the predicted transform-limited pulse width for an inhomogeneous gas laser     

The 13CH3OH optically pumped far-infraredlaser: new lines and frequency measurements

We report 18 new laser lines from ¹³CH₃OH generated in an optically pumped far-infrared laser; the laser lines are in the range of 54.2-420 μm and are all characterized in wavelength, polarization relative to the pumping CO₂ radiation, and pump offset relative to the CO₂ center frequency. The frequencies of seven of these new lines along with 10 previously reported lines were measured by an accurate heterodyne technique, mixing them in a metal-insulator-metal (MIM) point contact diode, with another laser line of known frequency