Short single-mode CO2 laser pulse generation by pulsed Q-switching

A simple method for the generation of short, single-mode CO₂ laser pulses produced by applying two voltage gates (of amplitude 3U_λ/4 and U_λ/4) to an electro-optic Q-switch placed in a three-mirror cavity is proposed. Single, single-mode, well-synchronizable pulses of 3 ns duration and of 3 mJ energy have been experimentally achieved from a TEA CO₂ laser with an intracavity Pockels cell with 3 ns switching time. Using a numerical simulation it is shown that with shorter switching time (≈1 ns) the method enables one to obtain, from such a laser, a single, megawatt pulse of 1 ns duration.     

An actively mode-locked TEA CO2 laser with multiline output

An actively mode-locked TEA CO₂ laser producing pulses consisting of more than 3 lines of the 10.4 μm band by inserting a KCl plate is described.     

Photodissociation of N2F4 by a nanosecond CO2 laser pulse

Photodissociation of N₂F₄ by a strong nanosecond CO₂ laser pulse was studied by probing the interaction volume with both UV and IR beams. Up to 20% of the molecules were found to be dissociated into NF₂ during the first few nanoseconds following the passage of the pulse.     

An injection-locked single-mode tea CO2 laser for SMM laser pumping

A D₂O laser has been developed for collective Thomson scattering measurements of ion temperature in high temperature plasmas. A pulse duration and a spectral width of a high power D₂O laser has been successfully controlled for this purpose, by using a TEA CO₂ laser injection-locked by an etalon-tuned TEA CO₂ laser as a pump source.     

Selection of single,mode-locked CO2 laser pulses by semiconductor reflection switching

Reflection switching of high power, 10 μm radiation by optically induced carriers in a semiconductor has been achieved by irradiating germanium with 3 ns pulses of 1.06 μm radiation. This has permitted the selection of single mode-locked pulses of 10 μm radiation with energies in the 1–2 joule range.     

Generation of far-infrared pulses by use of a passively mode-locked high-pressure CO2 laser

Summary Our present study demonstrates for the first time generation of frequency-tunable intense infrared radiation pulses in the nanosecond time regime by mode-locking a high pressure CO₂ laser using p-doped germanium as a saturable absorber. These pulses were transferred into the FIR region via stimulated Raman scattering of the CO₂ laser radiation in CH₃F resulting in subnanosecond FIR laser pulses.     

Absolute frequencies of CO2 laser transitions by multiplication of CO2 laser difference frequencies

Frequencies of CO₂ laser transitions have been compared to the Cs standard by a four-step frequency chain using difference-frequencies from five CO₂ isotope lasers. A tungsten-nickel diode generates the differences and their harmonics. Measurement of the 10.71 μm R(6) transition of ¹³C¹⁸O₂ is described. The absolute frequency was found to be 27 979 469.512(65) MHz. Simultaneously, the four other CO₂ frequencies in the chain were also determined.     

XPS investigation on Upilex-S polyimide ablated by pulse TEA CO2 laser

Laser ablation of Upilex-S polyimide films 80 μm thick was performed in air using a pulse TEA CO₂ laser with wavelength 9.3 μm. A halo surrounding the hole was observed, which is covered with sub-micro particles. Pieces of ablation products protrude from the ablated surface, leading to considerable roughness of the ablated area. Chemical and structural changes of Upilex-S polyimide film surface irradiated by the pulse TEA CO₂ laser in air were analyzed by X-ray photoelectron spectroscopy (XPS). Relative C content in the ablated area was found to be higher, whilst both O and N contents were lower than in the untreated area. This means that TEA CO₂ laser ablation released both the O and N atoms. Also, the peak areas corresponding with carbonyl group (C=O) in the imide system were reduced much more and a new component at 287.0 eV assigned to the amide structure (N---C=O) was detected after laser ablation. These suggest that the pyrolysis of the Upilex-S polyimide was the decomposition of the imide ring between the nitrogen/aromatic carbon atom and carbonyl carbon atom. In addition, another new component arising from >C=O groups was also detected for higher fluence (7.83 J/cm²), and its peak areas is very small. This result indicates that the slight oxidation may take place with higher fluence during laser ablation in air. Based on above-mentioned experimental results, a possible thermally-induced decomposition path of Upilex-S polyimide ablated by TEA CO₂ laser is presented.     

损耗调制CO2激光脉冲的噪声特性

由于自发辐射噪声的涨落,CO2激光器的脉冲峰值强度与时间延迟密切相关。理论和实验研究发现,对于典型的B类CO2激光器．在损耗调制情况下,当脉冲峰值出现在最低腔损耗to之前时,初始自发辐射噪声越大,相对于阈值点的第一个渡跃时间tFP越小,对应的峰值强度越小;当脉冲峰值出现在最低腔损耗to之后时,初始自发辐射噪声越大,相对于阈值点的第一个渡跃时间tFP越小,对应的峰值强度则越大。     

An investigation of the spectral content of a mode-locked pulsed CO2 laser

The frequency width of a pulse train in a pulsed mode-locked CO₂ laser has been accurately measured by means of a Fabry-Perot interferometer. We succeeded in resolving the longitudinal mode structure. The results are in excellent agreement with the results of previous measurements of the line width under lasing conditions.     

Current CO2 laser surgery

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.     

Hole drilling studies with a variable pulse length CO2 laser

A transversely excited CO₂ laser has been used to investigate the interaction between laser pulses of duration ≈ 40 μs, and metallic targets. The dependence of machining efficiency on power density has been studied, and high speed photography has been used to compare interactions with different pulse durations. Metallurgical analysis has revealed important structural effects in both mild steel and aluminum samples.     

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采用独特的电极结构和预电离脉冲群开关放电技术, 实现了5kW 量级平均功率横流CO₂激光器脉冲激光输出. 关键词： 2脉冲激光')" href="#">CO₂脉冲激光 预电离 脉冲群开关     

Advanced CO2 laser rangefinders

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.     

Tunable UV and IR picosecond pulse generation by nonlinear mixing using a synchronous mode-locked dye laser

The short-pulse output from a synchronous mode-locked tunable dye laser was sum and difference mixed in nonlinear crystals of KDP, ADP and LiIO₃ with the 1.064-μm and 532-nm pulse trains from its mode-locked Nd: YAG pump. This method allowed efficient generation of narrow-bandwidth tunable short pulses in the uv from 270 to 432 nm and in the IR from 1.13 to 5.6 μm.     

A novel pumping arrangement for tunable single picosecond pulse generation with a N2 laser pumped distributed feedback dye laser

A novel excitation scheme for a N₂ laser pumped distributed feedback dye laser is described. The dye laser generates 80–100 ps pulses with a time-bandwidth product better than 0.6. Several tuning methods are proposed, and a number are investigated experimentally. Continuous tuning over a 50 Å range without mode-hopping is demonstrated.     

New CH2F2 FIR laser lines pumped by a tunable WG CO2 laser

8 new large offset FIR laser lines of CH₂F₂ have been discovered by pumping with a high tunability waveguide CW CO₂ laser. Optoacoustic measurements of CH₂F₂ have also been performed and the pump offsets of the new and of previously known lines have been measured and checked. Some assignments are proposed and a few assignments found in literature are checked     

Investigation of cutting of engineering ceramics with Q-switched pulse CO2 laser

In this paper, the cutting of Si₃N₄ engineering ceramics with Q-switched pulse CO₂ laser is studied. Considering the influence of the cut front shape on the absorption of the laser beam, a simplified 2D mathematic model is developed based on a pulsed laser vaporization cut process. This model is based on the conservation of energy. The experimental results show that it would realize crack-free cutting by using high-speed and multi-pass feed cutting process.