Mode-locked CO2 Laser Research Articles

On the possibility of mode-locked CO laser continuous-wave/pulse radiation and 4.8 mcm single-line 70 % efficiency

On the possibility of mode-locked CO laser continuous-wave/pulse radiation and 4.8 mcm single-line 70 % efficiency

Slab RF-discharge carbon dioxide laser with active mode-locking

Mode-locking with an acousto-optic modulator was for the first time demonstrated for a repetitively pulsed (150 Hz) slab RF discharge CO2 laser. The mode-locked CO2 laser emitted trains of 5.5 ns pulses following with 27.25 MHz repetition rate. Mode-locking also affected the laser pulses envelope in respect to free-runing mode. The numerical estimation of the laser system scalability indicated an opportunity to develop a very compact CO2 laser emitting sub-nanosecond pulses.

Selection of CO laser single nanosecond pulse by electro-optic CdTe shutter

To select a single laser pulse from a train of nanosecond pulses emitted by a mode-locked CO laser with wavelengths from ∼5 to 6μm, an electro-optic shutter based on CdTe Pockels cell was developed. A contrast between the selected pulse and unselected laser emission was equal to 20 and twice as much decreased in a CO laser power amplifier. To increase the contrast, a feasibility of applying a narrow-gap semiconductor as a saturable absorber is discussed.

CO激光在非线性晶体ZnGeP2和GaSe中的混频效应

The CO laser frequency mixing in high-quality ZnGeP2 and GaSe crystals is studied to obtain the 2.15-1 500 μm coherent sources.Secondary Harmonic Generation(SHG),sum-and difference frequency generations are considered as a method for the CO laser frequency mixing and the mode-locking as an efficient way to improve the mixing efficiency.Results show that the internal SHG efficiency of Q-switched multiline CO laser radiation has exceeded by 0.3% for GaSe crystal and has reached by 1.1 % for ZnGeP2 crystal.When the SHG is in ZnGeP2,the internal efficiency of electron beam sustained discharge frequency-tunable mode-locking CO laser is up to 12.5 %.Simultaneous SHG and sum frequency generation show the same output spectrum.It is shown by modeling that the sum and difference frequency generations of neighboring lines of both fundamental and first overtone bands can allow one to get the oscillation,respectively,at 4.0-5.0 μm and 100-≥1 200 μm(THz).In conclusions,the frequency mixing of mode-locked CO laser emission lines in ZnGeP2 crystals allows some one to design 2.15-≥1 500 μm coherent sources with the power frequency conversion efficiency up to or over 12.5%.

Mode-Locked CO Laser for Isotope Separation of Uranium Employing Condensation Repression

In the present work, we have suggested a technical solution of a CO laser facility for industrial separation of uranium used in the production of fuel for nuclear power plants. There has been used a method of laser isotope separation of uranium, employing condensation repression in a free jet. The laser operation with nanosecond pulse irradiation can provide acceptable efficiency in the separating unit and the high effective coefficient of the laser with the wavelength of 5.3 μm. Receiving a uniform RF discharge under medium pressure and high Mach numbers in the gas stream solves the problem of an electron beam and cryogenic cooler of CO lasers. The laser active medium is being cooled while it is expanding in the nozzle; a low-current RF discharge is similar to a non-self-sustained discharge. In the present work, we have developed a calculation model of optimization and have defined the parameters of a mode-locked CO laser with an RF discharge in the supersonic stream. The CO laser average power of 3 kW is sufficient for efficient industrial isotope separation of uranium at one facility.

Nonlinear intensity dependence in the infrared multiphoton excitation and dissociation of methanol pre-excited to different energies

We report quantitative dissociation yields for the reaction CH3OH (vOH)→ lim nhνCH3+OH induced by infrared multiphoton excitation of methanol pre-excited to various levels of the OH stretching vibration (vOH=0, 1, 3, 5). The yields are measured by detecting OH using laser induced fluorescence. It is demonstrated that for low levels of pre-excitation (vOH=0, 1, 3) there is a substantial nonlinear intensity dependence, as a higher yield is found for self mode-locked CO2 laser pulses (with higher peak intensity) as compared to single mode pulses of the same laser fluence, but lower peak intensity. In contrast, at high levels of preexcitation (vOH=5) this nonlinear intensity dependence is absent. Quantitative model calculations are carried out using a case B/case C master equation approach that takes nonlinear intensity dependence into account. The calculations are consistent with the experimental results and confirm the prediction that an important part of the selectivity of the CO2 laser excitation step in infrared laser assisted photofragment spectroscopy of CH3OH is due to this nonlinear intensity dependence. We discuss further consequences of these experimental observations and theoretical predictions, which are also extended to infrared multiphoton excitation of C2H5OH. Infrared (C–O) chromophore band strengths are reported for CH3OH and C2H5OH.

Experiment on the optical tunneling process of electrons from a gold surface induced by mode-locked CO2 laser pulse trains

Using intense mode-locked CO2 laser pulse trains we verified the occurrence of the laser-induced, new-type dynamic optical tunneling of electrons from a gold surface. The results are in accordance with the theoretical predictions and our previous experiments carried out for both atoms and gold surface using single longer (ns) CO2 laser pulses. Unknown properties of the development of the CO2 laser train are revealed based on our higher-order coherence detection of electron emission.

Picosecond resolution, real-time linear detection system for 10-μm radiation

A 10-μm detection system based on up-conversion in proustite has been developed for the measurement of subnanosecond pulses of CO2 laser radiation. This has involved the development of a ’’stretched-pulse’’ Q-switched Nd:YAG oscillator which can be synchronized with the output of a transverse discharge CO2 laser. The 1.06-μm radiation generated by this oscillator and the incoming 10-μm radiation pass collinearly through a 0.6-cm-long proustite crystal which is oriented for type II phase matching. An investigation of the bandwidth of the up-conversion process has shown that it should be possible to resolve 10-μm pulses with durations of ∼5 psec. Using an image converter streak camera to record the 0.96-μm sum frequency, the overall performance of the system has been investigated with the aid of a mode-locked CO2 laser operating at a pressure of 12 atm. The results have demonstrated that mode-locked CO2 pulses as short as ∼75 psec can be generated and that the temporal resolution of the complete detection system corresponds to that of the streak camera.

Multiline mode-locked uv-preionized CO2 laser

A uv-photopreionized TEA CO2–N2 discharge is incorporated in an actively mode-locked CO2 laser system capable of producing individual pulses of peak power of > 200 MW with durations ∼ 1 nsec. Spectral examination of the laser output indicates that oscillation occurs simultaneously on several rotational lines of the 10.4-μ band.

An optical bridge for the assessment of mode-locked CO2 lasers

An optical bridge which relies on the directional property of photon drag detectors is described. Used in conjunction with a mode-locked CO2 laser the bridge has proved to be a sensitive instrument for the study of nonlinear absorption. With nonlinear absorbers in both arms of the bridge the duration of mode-locked CO2 laser pulses can be measured. This bridge method has a higher discrimination than the techniques used with near-visible lasers which, in any case, are not easily adaptable for use at 10 μm.

Actively mode-locked transversely excited atmospheric (T.E.A.) CO2 laser

A mode-locked CO2 laser with transverse pulse pumping has been developed which employs a Ge ultrasonic diffraction cell as an active loss modulator. This paper describes the initial stage of an effort to exploit the broad bandwidth (̃ 5 Ghz) of the CO2 laser transition and the high concentration of active gas at atmospheric pressure for generating ultra-short infra-red pulses at 10.6 μm wavelength. With the laser system presently described, output pulses with typical durations of about 1 ns and peak powers in the multi-megawatt range have been obtained for the first time.