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• CO laser operation with CO 2 gas mixture under varying operating conditions. • N 2 free operation over very narrow discharge and operating pressure conditions. • N 2 found to improve power, emission spectrum richness, discharge stability. • More than 20 transitions, >100mW on several lines in dispersive configuration. • Lower temperatures shift trapping levels to lower vibrational quantum numbers. This study explores the emission spectra and performance characteristics of a cryo-cooled CO laser system operating with CO 2 laser gas mixture under various operating conditions, viz., N 2 free gas mixture, different coolant temperatures and in grating tuned configuration. The narrow operational window in case of N 2 free gas mixture, increased output power and richer emission spectrum obtained with the addition of N 2 gas indicates enhanced discharge stability and efficient excitation in presence of Nitrogen. The emission spectrum revealed shifting of the trapping levels towards lower vibrational quantum number with reducing coolant temperature and the same was also corroborated by theoretical calculations. No lasing was observed for vibrational levels V>15 which is attributed to the higher partial pressure of oxygen inherently present in the gain medium formed due to dissociation of CO 2. The system lased on more than 20 transitions in grating tuned configuration with power exceeding 100mW on several lines. The presence of higher concentration of O 2 in the discharge prevents carbon deposition − a common issue in CO lasers. This study underscores the significance of this unconventional CO laser system offering reliable operation in the 5 µm wavelength region without the usage of extraneous CO gas. [ABSTRACT FROM AUTHOR]

In order to realize real-time capnographic monitoring, a compact carbon dioxide sensor based on tunable diode laser spectroscopy technology was developed by means of a 2004 nm distributed feedback laser and a circular gas cell. The toroidal cell can achieve an optical path length of 3.49 m in a volume of 38 ml, which enables the tunable diode laser spectroscopy carbon dioxide sensor to achieve a detection limit of 175 ppm at a measurement rate of 12.5 Hz. The actual exhaled carbon dioxide gas detection experiments were implemented, including the breath analysis of a normal subject under different conditions and another subject with pneumothorax. It indicates that the sensor has good effectiveness and practicability for carbon dioxide metabolic monitoring and related disease diagnosis. [ABSTRACT FROM AUTHOR]

Wavelength-matched vibrational excitations of ethylene (C2H4) molecules using a tunable carbon dioxide (CO2) laser were employed to significantly enhance the chemical vapor deposition (CVD) of diamond in open air using a precursor gas mixture of C2H4, acetylene (C2H2), and oxygen (O2). The CH2-wag vibration mode (ν7) of the C2H4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 μm were applied to the CVD processes to compare the C2H4 excitations and diamond depositions. Compared with 10.591 μm produced by common CO2 lasers, the laser wavelength of 10.532 μm is much more effective to excite the C2H4 molecules through the CH2-wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 μm, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced. [ABSTRACT FROM AUTHOR]

Presents a study which examined the properties of shell confinement long-life plasmas produced by a carbon dioxide laser. Use of x-ray spectroscopic methods; Experimental results; Discussion and conclusions.

Presents a study which examined the output energy characteristics of the pulsed, optically pumped 4.3-µmeter carbon dioxide laser. Description of a rate-equation model; Experimental apparatus; Optimization of output energy.

Discusses a study which examined the gain and saturation intensity of a multichannel extended-area discharge carbon dioxide laser. Theoretical background; Description of the experimental setup; Findings.

Background: Acne is the most common skin disease affecting adolescents and young adults, with associated scarring and its sequelae. Treatment options are either lifting procedures raising scar base closer to normal skin surface, or resurfacing ones injuring epidermis and superficial dermis with neocollagenesis and epidermal repair. Punch elevation (PE) method is better for improving deep atrophic acne scars, that can be combined with depth resurfacing. CO2 laser stimulates new collagen formation, tightens skin and raises scar to surface. Aim of the Work: to assess efficacy and safety of combination of PE technique and fractional co2 laser (Fr co2 L) compared to fr co2 L alone. Subjects and Methods: 20 atrophic post acne scars patients were subjected to history taking, general and dermatological examinations, identifying scars types and grades. Treatment response at start, before each fr. co2 L session and 4 weeks after last laser session was clinically evaluated by Goodman and Baron scale, and recording patients' photographs, satisfaction, and complications. Histopathological examination of scar skin biopsies before and 4 weeks after the last fr. co2 L session was done using H&E, Mallory trichome, sliver stain and immunohistochemical VEGF. Results: combined treatment with fr co2 L and PE was more effective in improving post acne scars than fr. co2 L resurfacing alone. Histopathological examination before combined fr. co2 L and PE treatment and 1 month after the last fr. co2 L session showed high significant increase in epidermal thickness (H&E), increase in collagen fiber type III (Mallory trichrome stain), decrease in collagen fiber type I (sliver stain) and increase in fibroblasts' activity (VEGF). Conclusion: both PE technique and fr. co2 L resurfacing show promising efficacy and safety in treating atrophic post acne scars, complementing each other to improve skin texture and appearance, with excellent cosmetic outcomes. [ABSTRACT FROM AUTHOR]

The accuracy of the existing glazing depth measurement models of concrete surface processed by CO2 laser are affected by numerous factors, such as sideways conduction and the inhomogeneous substrate of the concrete; in addition to the environment and measurement approach used and thus error factor is emerged. The empirical glazing surface of concrete samples using (25–100) watt power CO 2 laser workstation shows inaccuracy of results matching within the existing calculated model results that cannot be ignored even in low laser power supplied. Thus, in this paper, a new empirical glazing model (IDGM) for glazing depth measurement is derived and verified. The validation process of the proposed model for transvers speed (1, 2, and 3 mm/sec) shows that the real time measured values agree with those from the proposed models to within approximately 96%. In addition, it offers the capability to estimate the glazing depth for a wide range of predefined laser power intensity. In addition this model barring costly experimental validation studies, low cost solution and less power consumption. [ABSTRACT FROM AUTHOR]

We report on the mid-infrared (MIR) and terahertz (THz) wave spectra of DO gas pumped using a fundamental transverse mode transversely excited atmospheric CO laser with an emission wavelength of 9.26 μm. We obtain MIR emission lines at center wavelengths of 9.262, 9.491, and 9.752 μm, which correspond to the vibrational-energy-level-transition lines of DO. We observe an intense THz stimulated Raman emission line of 385 μm and a weak cascade-transition line of 359 μm for transitions from rotational levels 4 to 4 and 4 to 4 in the first-excited vibration state of the DO molecule gas. We establish a four-energy-level system for modeling the laser kinetics of the dual-wavelength (385 and 359 μm) superradiation THz laser. For the optically pumped DO gas 385 μm THz laser, in considering the cavity effect and insertion loss of a THz cavity oscillator, an approximation treatment of the THz laser kinetics can be made based on a three-energy-level system. [ABSTRACT FROM AUTHOR]

A novel method for polishing conical shaped optical fiber deflectors by modulated CO laser exposure is reported. The conical shaped fiber deflector geometry was first formed with rough mechanical polishing, then it was exposed to modulated CO laser operating with wavelength at 10.6 µm to achieve fine polish surfaces. The motivation of this work is to demonstrate that the modulated CO laser exposure approach allows a fiber surface roughness at a nanometer scale without modifying the conical shape of the fiber deflector. The average surface roughness of mechanically polished fiber deflectors with 30 and 9 µm lapping films was smoothed down to 20.4 and 4.07 nm, respectively, after CO laser polishing process. By combining mechanical and laser polishing techniques, fabrication of conical shaped optical fiber deflectors takes less time and it becomes laborer independent and easy to apply. [ABSTRACT FROM AUTHOR]

Focuses on study which conducted spatially resolved transverse-gain profile measurements in radio frequency- and direct current-excited waveguidelike cavities for carbon dioxide laser gas mixtures. Requirements for spatially resolving the gain profile; Impact of the current density and gas temperature on the gain profile; Recommendations.

Presents a sealed-off transversely excited atmosphere (TEA) CO[sub2] laser with a gas internal coaxial circulation scheme. Advantages of the design over the conventional transverse gas flow TEA CO[sub2]; Output when the laser was operated at 33 hertz with pauses.

Vulval lichen sclerosus is an uncommon skin condition that can usually be managed with topical corticosteroids to maintain remission. However, there is a subset of patients in whom it remains recalcitrant despite treatment with super-potent topical corticosteroids. We report a case series of four patients undergoing fractional carbon dioxide laser resurfacing and one with ablative carbon dioxide laser for severe, hyperkeratotic vulval lichen sclerosus not responding to super-potent topical corticosteroids. In these patients, carbon dioxide laser was successful in achieving remission. Their vulval lichen sclerosus was subsequently able to be maintained with topical corticosteroid treatment. [ABSTRACT FROM AUTHOR]

The line deviations and angle deviations of the injected beam at the resonator mirrors in the large area discharge CO 2 laser (LADCL) are changed when the output mirror and the phase-locking mirror (PLM) are misaligned. The equiphase surfaces excited by the injected beam are different in the laser resonator and the effect of phase-locking will be influenced. It is shown that the misalignment of PLM is the main cause of phase-locking range reduction. The misalignment of the output mirror will mainly result in the deviation of the output beam, and the misalignment of the PLM will mainly cause decrease of the light intensity. And the maximum misaligned angle should not exceed 20 s in order to obtain the ideal effect of phase-locking. The calculated results can provide references for studying deeply the misalignment of LADCL. [ABSTRACT FROM AUTHOR]