KrCl Laser Research Articles

Laser-induced nitrogen oxide fluorescence from nitro compounds by 222 nm laser

This paper presents the study results of the single-frequency interaction of KrCl laser broadband radiation with nitro compound vapors in the atmosphere. The optical method of a substance spectroscopic analysis including photofragmentation of a complex R–NO2 molecule followed by laser-induced fluorescence of vibrationally excited fragments of NO X2Π, v''>0 (PF-LIF) was studied in the experiments. It has been shown that R–NO2 molecules exposed to λ = 222 nm FWHM 0.3 nm KrCl laser broadband radiation undergo photofragmentation followed by resonant excitation of several electronic-vibrational levels of NO X2Π, v'' (2,4). At the same time, the concentration of fragmented NO X2Π, v'' (2,4) increases due to the secondary PF-LIF NO2 process during the nanosecond laser pulse.

Performance of a KrCl Laser Depending on the Temperature of the Active Medium with HCl and BCl3 As a Halogen Donor

Performance of a KrCl Laser Depending on the Temperature of the Active Medium with HCl and BCl3 As a Halogen Donor

Resonance-Enhanced Multiphoton Ionization of Molecular Oxygen at the 222 nm KrCl Laser Wavelength

We study the photo-ionization mechanism of molecular oxygen at the 222 nm KrCl laser wavelength within a laser pulse intensity range of 108 – 1010 W/cm2, using 14 ns laser pulses. We experimentally observe (2+1) resonance-enhanced multiphoton ionization (REMPI) of molecular oxygen with the effective ionization cross-section {sigma}_{{mathrm{O}}_2}^{(2)} = (3.2 ± 1.3) · 10−18 cm4 · s−1 · W−2 at an intensity range of 109 – 1010 W/cm2 and linear ionization due to gas impurities at an intensity range of 108 – 109 W/cm2.

Photoluminescence of polymethyl methacrylate excited by a KrCl excilamp and a KrCl laser

Photoluminescence of polymethyl methacrylate excited by a KrCl excilamp and a KrCl laser

Pulsed UV laser technologies for ophthalmic surgery

The paper provides an overview of the results of multiyear joint researches of team of collaborators of Institute of Laser Physics SB RAS together with NF IRTC “Eye Microsurgery” for the period from 1988 to the present, in which were first proposed and experimentally realized laser medical technologies for correction of refractive errors of known today as LASIK, the treatment of ophthalmic herpes and open-angle glaucoma. It is proposed to carry out operations for the correction of refractive errors the use of UV excimer KrCl laser with a wavelength of 222 nm. The same laser emission is the most suitable for the treatment of ophthalmic herpes, because it has a high clinical effect, combined with many years of absence of recrudescence. A minimally invasive technique of glaucoma operations using excimer XeCl laser (λ=308 nm) is developed. Its wavelength allows perform all stages of glaucoma operations, while the laser head itself has high stability and lifetime, will significantly reduce operating costs, compared with other types of lasers.

High-power gas-discharge excimer ArF, KrCl, KrF, and XeCl lasers on buffer-gas free gas mixtures

Results of experimental studies of the gas mixture (laser active medium) effect on the lasing energy and overall efficiency of excimer discharge ArF (193 nm), KrCl (222 nm) KrF (248 nm), and XeCl (308 nm) lasers operating in buffer-free gas mixtures are presented. The optimal (in terms of maximum radiation energy) ratios of the gas components of the excimer laser active media are found, at which efficient operation is achieved with a sufficiently high power of the laser radiation. It is confirmed experimentally that for the rare gas halide discharge pumped excimer lasers the presence of a buffer gas in the active medium is not required for efficient laser operation. For example, in two-component excimer laser gas mixtures, containing working rare and halogen-containing gases, laser pulse energy of up to 170 mJ and high pulsed power of laser radiation of up to 24 MW have been attained for the first time for pulsed gas-discharge excimer lasers operating on electronic transitions at excimer ArF*, KrCl*, KrF*, and XeCl* molecules pumped by a transverse electric volume discharge of a low-pressure buffer-free gas mixture. A overall efficiency maximum of up to 0.8% was experimentally attained for binary gas mixture of KrF and XeCl lasers.

Precise measurements of the wavelength in KrCl laser spectral region (222 nm)

Precise measurements of the wavelength in KrCl laser spectral region (222 nm)

High-power gas-discharge excimer ArF, KrCl, KrF and XeCl lasers utilising two-component gas mixtures without a buffer gas∗∗Reported at the Fifth Russian-Chinese Workshop and School for Young Scientists on Laser Physics and Photonics (RCWLP&P, Novosibirsk, August 26 – 30, 2015).

Results of an experimental study of the influence of a gas mixture (laser active medium) composition on an output energy and total efficiency of gas-discharge excimer lasers on and molecules operating without a buffer gas are presented. The optimal ratios of gas components (from the viewpoint of a maximum output energy) of an active medium are found, which provide an efficient operation of laser sources. It is experimentally confirmed that for gas-discharge excimer lasers on halogenides of inert gases the presence of a buffer gas in an active medium is not a necessary condition for efficient operation. For the first time, in two-component gas mixtures of repetitively pulsed gas-discharge excimer lasers on electron transitions of excimer molecules and , the pulsed energy of laser radiation obtained under pumping by a transverse volume electric discharge in a low-pressure gas mixture without a buffer gas reached up to and a high pulsed output power (of up to ) was obtained at a FWHM duration of the KrF-laser pulse of . The maximal total efficiency obtained in the experiment with two-component gas mixtures of KrF and XeCl lasers was 0.8 %.

Мощные газоразрядные эксимерные ArF-, KrCl-, KrF- и XeCl-лазеры на газовых смесях без буферного газа

Мощные газоразрядные эксимерные ArF-, KrCl-, KrF- и XeCl-лазеры на газовых смесях без буферного газа

Optical spectra and electron–Hole liquid in diamond

Optical absorption spectra in the spectral range from 200 nm to 15 μm, Raman spectra in the wavenumber range of 100–3700 cm–1, and photoluminescence spectra in the spectral range of 200–850 nm have been studied for five nominally “pure” diamond samples synthesized in different ways. The measurements have been carried out in the temperature range of 80–300 K. Photoluminescence was excited by the KrCl laser radiation at a wavelength of 222 nm with a pulse FWHM of 8 ns and a peak intensity on the sample surface of up to 13 MW/cm2. It is found that, at absorption coefficients of diamond samples below 10 cm–1 in the spectral range of 225–226 nm, their photoluminescence spectra exhibit a radiative recombination band of electron–hole liquid peaked at 240 nm.

Design and performance characteristics of a krypton chloride (λ = 222 nm) excimer laser

Development of a discharge-pumped krypton chloride (KrCl) laser operating at 222 nm wavelength is demonstrated. In this paper the design, successful realization and operating characteristics of KrCl excimer laser are reported. The laser is driven by a simple and efficient excitation technique using automatic UV pre-ionization with discharge-pumped self-sustained capacitor–capacitor (C–C) energy transfer circuit. The experimental investigations including output laser energy, temporal pulse parameters, emission spectra and beam profile of the KrCl laser were recorded. For high repetition rate operation, in-built, compact gas circulation system using tangential blower was incorporated. The laser was operated at 25 kV discharge voltage, gas mixture of 5 mbar HCl, 160 mbar kypton and neon as balance with a total gas pressure of ∼2.5 bar. These experiments produced an efficient and reliable output energy of 25 mJ from an active volume of 60 cm3.

Titanium alloy surface modification by excimer laser irradiation

Abstract The main effects of the interaction of UV emitting KrCl (at 222 nm) and XeCl (at 308 nm) excimer lasers with titanium alloy Ti6Al4V are presented. Single-pulse and multi-pulse irradiations were used, with varying laser beam fluences. The resulting interactions with the surface show thermal character, and produce: (i) damages in the form of craters at higher pulse counts and fluences of 7 J cm−2 and 7.2 J cm−2, which are far above the damage threshold; (ii) melt pools with visible wave-like structures at periphery; (iii) resolidified droplets and cracks at periphery (at higher pulse count), (iv) increasing content of oxygen, with a domination of TiO2.

Influence of the specific pump power on the output energy and efficiency of a 223-nm gas-discharge-pumped excimer KrCl laser

The influence of the specific pump power on the output energy and efficiency of a 223-nm gas-discharge-pumped KrCl excimer laser operating on the Ne—Kr—HCl and He—Kr—HCl mixtures is studied. The optimal specific pump powers are found at which the maximum values of the total efficiency and output energy of the KrCl laser are achieved. The optimal specific pump power for the Ne—Kr—HCl and He—Kr—HCl mixtures lies in the ranges from 5.0 to 5.5 MW cm-3 and from 5.8 to 6.5 MW cm-3, respectively. The output energy of 700 mJ at the efficiency 1.0% for the KrCl laser on the Ne—Kr—HCl mixture is obtained for the first time.

Photoprocesses induced by short-wavelength excimer laser radiation in adsorbed halomethane molecules

Photolysis and desorption induced by ArF and KrCl laser irradiation of CH2I2, CH3I, CCl4, CHCl3, CH2Cl2, CF2Cl2, and CHF2Cl molecules adsorbed on fused silica were studied. One-photon fragmentation, as well as nonlinear dissociation and desorption processes, were observed. It was found that three-step fragmentation is a widespread phenomenon for molecules that experience resonant absorption of laser radiation. To explain the phenomenon, a mechanism based on stimulated emission was proposed. The nonlinear character of desorption is associated with redistribution of absorbed energy in adsorbed molecules and its transfer to the substrate.

Gain of a long-pulse KrCl excimer laser

The net gain is measured for various pump power densities in a discharge-pumped long-pulse KrCl laser (222 nm). For this, a three-electrode laser system is employed, which is operated at high gas pressures of around 3.5 bar with pump power densities of 300−650 kW cm−3. The net gain reaches a maximum of 1.6% cm−1. Using the experimental results, values are calculated for the small-signal gain, the losses, and the saturation intensity. The losses and the saturation intensity are found to increase much stronger with the excitation rate than the small-signal gain. Fluorescence measurements at 222 nm show that the upper laser level depopulates faster when the power density increases. The influence of collisional quenching and the halogen consumption on the laser performance are discussed.

Long-pulse KrCl laser with a high discharge quality

The discharge quality and optimum pump parameters of a long-pulse high-pressure gas discharge excited KrCl laser are investigated. A three-electrode prepulse–mainpulse excitation circuit is employed as pump source. The discharge volume contains a gas mixture of HCl/Kr/Ne operated at a total pressure of up to 5 bar. For a plane–plane resonator, the divergence of both output laser beams is measured. A low beam divergence of less than 1 mrad is measured as a result of the very high discharge homogeneity. A maximum laser pulse duration of 150 ns (FWHM) is achieved for a pump duration of 270 ns (FWHM) and a power density of 340 kW cm-3. Pumping the discharge under optimum conditions employing a stable resonator results in a maximum specific energy of 0.45 J/l with a laser pulse duration of 117 ns and an efficiency of 0.63% based on the deposited energy.

Comparison of luminescence spectra of natural spodumene under KrCl laser and e-beam excitation

Spectral characteristics of pulsed photoluminescence (PL) and pulsed cathodoluminescence (PCL) of a natural spodumene were investigated. PL was excited by laser radiation at 222 nm with pulse duration of 10 ns at FWHM. PCL was excited by electron beams with pulse duration from 0.1 up to 4 ns and with current densities of 40–200 A/cm 2. There was a dominant broad band at 600 nm due to the manganese impurity in PCL spectra. But in PL spectra, the orange band had the intensity comparable with intensities of intrinsic defect bands. At sample cooling by liquid nitrogen, the intensity of orange band in the PCL spectrum increased by two times and the short-wave shoulder of the band reduced.

Luminescence of crystals excited by a KrCl laser and a subnanosecond electron beam

Luminescence of crystals of natural spodumene and natural diamond of the type IIa is studied upon excitation by a laser at a wavelength of 222 nm and by a subnanosecond avalanche electron beam (SAEB) formed in air at the atmospheric pressure. The photoluminescence spectra of spodumene and diamond are shown to exhibit additional bands, which are absent upon SAEB excitation. It is demonstrated that SAEB excitation allows one to analyse various crystals under normal conditions without using any vacuum equipment.

A 223-nm KrCl excimer laser on a He—Kr—HCl mixture

The results of experimental studies of the parameters of a 223-nm electric-discharge KrCl excimer laser on a He—Kr—HCl mixture depending on the excitation conditions and the composition of the active gaseous medium are presented. To achieve the maximum values of the output energy and the efficiency of the KrCl laser on mixtures with buffer gaseous helium, an excitation system was used that included a circuit with an LC inverter with a high-voltage switch based on an RU-65 spark gap. An output energy of 320 mJ with an efficiency of 0.5% relative to the energy stored in the capacitors is obtained in a KrCl laser with an active medium based on the buffer He gas at a charging voltage of 30 kV. Radiation pulses with a duration of 22±1 ns and a pulse power of 15 MW are obtained.

Surface modifications of TiN coating by the pulsed TEA CO 2 and KrCl laser

Interaction of a transversely excited atmospheric (TEA) CO 2 and excimer-KrCl laser, pulse duration ∼2 μs (FWHM of initial spike ∼100 ns) and ∼12 ns (FWHM), respectively, with polycrystalline titanium nitride (TiN) coating deposited on high quality steels, was studied. The results have shown that the titanium nitride was surface modified by the laser beam, with an energy density (ED) of 43.0 J/cm 2 (TEA CO 2 laser system) and 3.3 J/cm 2 (KrCl system), respectively. The energy absorbed from the CO 2 laser beam is partially converted to thermal energy, which generates a series of effects such as melting, vaporization of the molten material, shock waves, etc. The energy from the excimer-KrCl laser primarily leads to a fast and intense target evaporation. Calculated maximal temperatures, on the target surface, were 3940 and 8000 K for the TEA CO 2 and the KrCl lasers, respectively. It is assumed that TEA CO 2 laser affects the target deeper, during a longer time than the KrCl laser. The effects of the KrCl laser are confined to a localized area, near target surface, in the course of short time. The following morphological changes of titanium nitride surface were observed: (i) both types of laser caused ablation of the TiN coating in the central zone of the irradiated area, (ii) appearance of a hydrodynamic feature like resolidified droplets of material in the surrounding outer zone (cracking) in the case of the TEA CO 2 laser, and (iii) appearance of wave-like microstructures (consisting of periodic parallel fringes with a period of about 20 microns) in the case of KrCl laser. Formation of the wave-like microstructures is discussed in the context of laser-induced periodic surface structure (LIPSS) effects and diffraction phenomena. The process of the CO 2 and KrCl laser interaction with titanium nitride were typically accompanied by plasma formation. Plasma appeared above the target after about 40 and 1 laser pulse, respectively.