First-overtone CO Laser Research Articles

Repetitively pulsed cryogenically cooled quasi-sealed-off slab RF discharge first-overtone CO laser

A slab first-overtone CO laser of improved design excited by repetitively pulsed RF discharge was researched and developed. Its quasi-sealed-off operation appeared to be possible only by using active gas mixture composition with extremely high content of oxygen — up to 50 % with respect to CO concentration. Average output power of the first-overtone CO laser came up to ~2 W with the efficiency of ~2 %. The laser spectrum obtained by using three sets of output couplers consisted of more than 100 vibrational–rotational spectral lines in 28 vibrational first-overtone bands of CO molecule within 2.55÷3.90 μm wavelength range. The number of laser radiation pulses which could be produced by the laser in sealed-off mode of operation (without gas mixture renovation) reached ~5×105 at the averaged output power near its maximum, and ~106 at lower (near its half-maximum) averaged output power. Special features of laser radiation temporal behavior were discussed. Under repetitively pulse pump with repetition rate from 300 up to 7500 Hz, a temporal profile of the CO laser radiation changed from the train of time-separated laser pulses with high peak power to quasi-CW mode of operation.

Измерение поглощения в закиси азота и метане на длинах волн излучения обертонного CO-лазера с использованием топографической мишени и приемного телескопа

Измерение поглощения в закиси азота и метане на длинах волн излучения обертонного CO-лазера с использованием топографической мишени и приемного телескопа

RF discharge slab CO laser operating in both fundamental and first-overtone bands

A compact sealed-off cryogenically cooled radio frequency (RF) discharge slab CO laser, operating in both first-overtone (FO) and fundamental band (FB), was launched. Repetitively pulsed and CW modes of RF discharge excitation were studied. Average FB output power was up to 12W, with laser efficiency 14%. The multiline FB laser spectrum was observed within the wavelength range ∼5.1–5.4μm. An optical scheme “frequency selective master oscillator – laser amplifier” was applied for getting FB tuning. Single line FB lasing with average power up to several tens of mW was observed on ∼100 FB vibrational-rotational transitions of CO molecule within the spectral range ∼5.0–6.5 μm. Multiline FO lasing was observed on ∼80 spectral lines within the spectral range ∼2.5–4.0 μm, with maximum single line average output power 12mW. Total output power of the slab FO CO laser came up to 0.3W, with maximum laser efficiency 0.5%. Results of parametric studies of the FB and FO slab CO laser including complicated time behavior for laser pulses on different FO vibrational–rotational transitions are discussed.

Resonant absorption of first-overtone CO laser radiation by atmospheric water vapor and pollutants

Resonant absorption of first-overtone (FO) CO laser radiation by atmospheric water vapor and various organic and nonorganic pollutants is discussed. Suitable ro-vibrational lines are selected for their potential use in traditional spectroscopic schemes of atmospheric pollution diagnostics. Nonlinear atmospheric absorption of intense multiline FO CO laser radiation is simulated and laser-induced changes in absorption spectra are demonstrated. Absorption coefficients of a few substances on several FO CO ro-vibrational lines are experimentally measured. A comparative analysis of spectral characteristics of an FO CO laser and an HF (DF) laser demonstrates that the potential of FO CO laser applications for spectroscopic detection of various molecular trace gases is greater than that of HF and DF lasers.

Efficient pulsed first-overtone CO laser operating within the spectral range of 2.5-4.2 /spl mu/m

Output characteristics of a single-pulse e-beam controlled discharge laser operating on the first-overtone (FO) transitions (/spl Delta//spl nu/=2) of CO molecules have been studied both experimentally and theoretically. Various sets of dielectric mirrors with high reflectivity in the range of the overtone spectrum have been used for the laser resonator. Multiwavelength lasing has been obtained in the wide spectral range of 2.5-4.1 /spl mu/m on vibrational transitions from 6/spl rarr/4 up to 37/spl rarr/35. A maximum output efficiency of 11%, the highest ever published for a FO CO laser, has been experimentally obtained for the broad-band multiline FO CO laser. Maximum specific output energy is 50 J/1 Amagat. FO CO lasing was observed within a predischarge gas temperature range of 100-220 K. Spectral characteristics of the overtone laser operating on a selected set of vibrational bands have been analyzed theoretically. Theoretical calculations based on the experimental data predict that multiline FO CO laser efficiency can be increased up to 20%. Experiments with a single-pulse FO CO laser using a diffraction grating as a frequency-selective element demonstrated the feasibility of developing a frequency-tunable single-line FO CO laser. Tunable FO CO lasing on wavelengths from 2.7 up to 4.2 /spl mu/m corresponding to vibrational transitions from 13/spl rarr/11 up to 38/spl rarr/ 36 was obtained. The maximum specific output energy came up to 2.8 J/1 Amagat, with single-line output efficiency being up to 0.6%.

Frequency tunable single-line pulsed first-overtone carbon monoxide laser

Tunable single-line first-overtone (FO) CO lasing on wavelengths from 2.7 up to 4.2 μm corresponding to overtone vibrational transitions from 13→11 up to 38→36 on 413 ro-vibrational lines was experimentally obtained. A parametric study of energetic and spectral characteristics of the single-line FO CO laser was carried out. Energy distribution over ro-vibrational lines was measured. The maximum specific output energy (SOE) came up to ∼3 J/l Amagat, with single-line output efficiency being up to 0.6%. For the first time, a multi-quantum theoretical model was used to describe the tunable single-line FO CO laser. This multi-quantum approach demonstrated better agreement between theoretical calculations and observed experimental data for laser output as a function of vibrational quantum numbers.

Alternation of vibrational band intensities in multiline pulsed first-overtone CO laser spectrum

The effect of `spectrum alternation', i.e. the alternation of strong and weak vibrational bands, in a pulsed first-overtone CO laser spectrum is experimentally observed for the first time. Theoretically calculated spectral distribution also indicates the intensity alternation, which is determined by two sets of cascade transitions operating independently. An influence of laser mixture composition and gas density on the `spectrum alternation' is discussed.

Pulsed first-overtone CO laser with output efficiency higher than 10%

Output efficiency as high as 11% and specific output energy up to ∼50 J/l Amagat were experimentally obtained for a cryogenically cooled multiline pulsed first-overtone (FO) CO laser for the first time. The longest generated wavelength was 4.1 μm, corresponding to the 37→35 vibrational transition. FO CO lasing was observed within an initial gas temperature interval of 100–220 K. Theoretical calculations based on the experimental data predict that the FO CO laser efficiency can be increased up to 20%. High efficiency and high specific output energy obtained in the experiment places the FO CO laser amongst other high-power lasers.

Pulsed first-overtone CO laser: effective source of IR radiation in spectral range of 2.5–4.0 μm

Spectral properties of radiation of a pulsed electron-beam controlled discharge laser operating on the first-overtone transitions (Δ v=2) of CO molecules have been studied both experimentally and theoretically. Various sets of dielectric mirrors with high reflectivity in the wide range of overtone spectrum have been used for the laser resonator. Multiwavelength lasing has been obtained in the wide spectral range of 2.5–4.0 μm. Efficiency of the laser operating on few vibrational transitions within a relatively narrow spectral range comes up to 5% at entirely suppressed fundamental band (Δ v=1) lasing. Spectral characteristics of the overtone laser operating on a selected set of vibrational transitions have been analyzed theoretically. A comparison of the experimental and theoretical data has been made.

Parametric study of first-overtone CO laser with suppressed fundamental band lasing: experiment and theory

Parametric study of a first-overtone (FO) CO laser was carried out both experimentally and theoretically. A special optical filter was used for suppression of fundamental band lasing. The theoretical model is in satisfactory agreement with the experiment for a laser operating on a He-containing gas mixture. The maximum FO CO laser efficiency of 5.5% and specific output energy (SOE) of ∼20 J/l Amagat were obtained for a laser resonator with rather high useless optical losses, FO CO lasing taking place from 13→11 up to 30→28 vibrational transitions ( λ=2.7–3.6 μm). Important influence of intracavity water vapor on the output characteristics of FO CO laser and its spectrum, in particular, is discussed. Both theoretical and experimental results indicate that the FO CO laser efficiency up to 15–20% and SOE up to 50–80 J/l Amagat can be obtained.