Showing papers on "Ruby laser published in 2012"

Principles of Lasers

Abstract: 1 Introductory Concepts.- 1.1 Spontaneous and Stimulated Emission, Absorption.- 1.1.1 Spontaneous Emission.- 1.1.2 Stimulated Emission.- 1.1.3 Absorption.- 1.2 The Laser Idea.- 1.3 Pumping Schemes.- 1.4 Properties of Laser Beams.- 1.4.1 Monochromaticity.- 1.4.2 Coherence.- 1.4.3 Directionality.- 1.4.4 Brightness.- Problems.- 2 Interaction of Radiation with Matter.- 2.1 Summary of Blackbody Radiation Theory.- 2.2 Absorption and Stimulated Emission.- 2.2.1 Rates of Absorption and Stimulated Emission.- 2.2.2 Allowed and Forbidden Transitions.- 2.2.3 Transition Cross Section, Absorption and Gain Coefficient.- 2.3 Spontaneous Emission.- 2.3.1 Semiclassical Approach.- 2.3.2 Quantum Electrodynamic Approach.- 2.3.3 Einstein Thermodynamic Treatment.- 2.3.4 Radiation Trapping, Superradiance, Superfluorescence, and Amplified Spontaneous Emission.- 2.4 Nonradiative Decay.- 2.5 Line Broadening Mechanisms.- 2.5.1 Homogeneous Broadening.- 2.5.2 Inhomogeneous Broadening.- 2.5.3 Combined Effect of Line Broadening Mechanisms.- 2.6 Saturation.- 2.6.1 Saturation of Absorption: Homogeneous Line.- 2.6.2 Gain Saturation: Homogeneous Line.- 2.6.3 Inhomogeneously Broadened Line.- 2.7 Degenerate Levels.- 2.8 Relation between Cross Section and Spontaneous Radiative Lifetime.- 2.9 Molecular Systems.- 2.9.1 Energy Levels of a Molecule.- 2.9.2 Level Occupation at Thermal Equilibrium.- 2.9.3 Radiative and Nonradiative Transitions.- Problems.- References.- 3 Pumping Processes.- 3.1 Introduction.- 3.2 Optical Pumping.- 3.2.1 Pumping Efficiency.- 3.2.2 Pump Light Distribution.- 3.2.3 Pumping Rate.- 3.3 Electrical Pumping.- 3.3.1 Electron Impact Excitation.- 3.3.2 Spatial Distribution of the Pump Rate.- 3.3.3 Pumping Efficiency.- 3.3.4 Excitation by (Near) Resonant Energy Transfer.- Problems.- References.- 4 Passive Optical Resonators.- 4.1 Introduction.- 4.2 Plane-Parallel Resonator.- 4.2.1 Approximate Treatment of Schawlow and Townes.- 4.2.2 Fox and Li Treatment.- 4.3 Confocal Resonator.- 4.4 Generalized Spherical Resonator.- 4.4.1 Mode Amplitudes, Diffraction Losses, and Resonance Frequencies.- 4.4.2 Stability Condition.- 4.5 Unstable Resonators.- Problems.- References.- 5 Continuous Wave and Transient Laser Behavior.- 5.1 Introduction.- 5.2 Rate Equations.- 5.2.1 Four-Level Laser.- 5.2.2 Three-Level Laser.- 5.3 CW Laser Behavior.- 5.3.1 Four-Level Laser.- 5.3.2 Three-Level Laser.- 5.3.3 Optimum Output Coupling.- 5.3.4 Reasons for Multimode Oscillation.- 5.3.5 Single-Line and Single-Mode Oscillation.- 5.3.6 Two Numerical Examples.- 5.3.7 Frequency Pulling and Limit to Monochromaticity.- 5.3.8 Lamb Dip and Active Stabilization of Laser Frequency.- 5.4 Transient Laser Behavior.- 5.4.1 Spiking Behavior of Single-Mode and Multimode Lasers.- 5.4.2 Q-Switching.- 5.4.2.1 Methods of Q-Switching.- 5.4.2.2 Operating Regimes.- 5.4.2.3 Theory of Q-Switching.- 5.4.2.4 A Numerical Example.- 5.4.3 Mode Locking.- 5.4.3.1 Methods of Mode Locking.- 5.4.3.2 Operating Regimes.- 5 5 Limits to the Rate Equations.- Problems.- References.- 6 Types of Lasers.- 6.1 Introduction.- 6.2 Solid-State Lasers.- 6.2.1 The Ruby Laser.- 6.2.2 Neodymium Lasers.- 6.3 Gas Lasers.- 6.3.1 Neutral Atom Lasers.- 6.3.2 Ion Lasers.- 6.3.2.1 Ion Gas Lasers.- 6.3.2.2 Metal Vapor Lasers.- 6.3.3 Molecular Gas Lasers.- 6.3.3.1 Vibrational-Rotational Lasers.- 6.3.3.2 Vibronic Lasers.- 6.3.3.3 Excimer Lasers.- 6.4 Liquid Lasers (Dye Lasers).- 6.4.1 Photophysical Properties of Organic Dyes.- 6.4.2 Characteristics of Dye Lasers.- 6.5 Chemical Lasers.- 6.6 Semiconductor Lasers.- 6.6.1 Photophysical Properties of Semiconductor Lasers.- 6.6.2 Characteristics of Semiconductor Lasers.- 6.7 Color-Center Lasers.- 6.8 The Free-Electron Laser.- 6.9 Summary of Performance Data.- Problems.- References.- 7 Properties of Laser Beams.- 7.1 Introduction.- 7.2 Monochromaticity.- 7.3 First-Order Coherence.- 7.3.1 Complex Representation of Polychromatic Fields.- 7.3.2 Degree of Spatial and Temporal Coherence.- 7.3.3 Measurement of Spatial and Temporal Coherence.- 7.3.4 Relation between Temporal Coherence and Monochromaticity.- 7.3.5 Some Numerical Examples.- 7.4 Directionality.- 7.5 Laser Speckle.- 7.6 Brightness.- 7.7 Higher-Order Coherence.- Problems.- References.- 8 Laser Beam Transformation.- 8.1 Introduction.- 8.2 Transformation in Space. Gaussian Beam Propagation.- 8.3 Transformation in Amplitude: Laser Amplification.- 8.4 Transformation in Frequency: Second-Harmonic Generation and Parametric Oscillation.- 8.4.1 Physical Picture.- 8.4.1.1 Second-Harmonic Generation.- 8.4.1.2 Parametric Oscillation.- 8.4.2 Analytical Treatment.- 8.4.2.1 Parametric Oscillation.- 8.4.2.2 Second-Harmonic Generation.- Problems.- References.- 9 Applications of Lasers.- 9.1 Introduction.- 9.2 Applications in Physics and Chemistry.- 9.3 Applications in Biology and Medicine.- 9.4 Material Working.- 9.5 Optical Communications.- 9.6 Measurement and Inspection.- 9.7 Thermonuclear Fusion.- 9.8 Information Processing and Recording.- 9.9 Military Applications.- 9.10 Holography.- 9.11 Concluding Remarks.- References.- Appendixes.- A Space-Dependent Rate Equations.- B Physical Constants.- Answers to Selected Problems.

Optimal wavelengths for vein-selective photothermolysis.

Abstract: Background and Objective Oxyhemoglobin (HbO2) has been regarded as the primary target chromophore for selective photothermolysis of vascular malformations. In theory, venous lesions might be better treated with wavelengths preferentially absorbed by deoxyhemoglobin (Hb). Study Design/Materials and Methods Wavelength-dependent fluence thresholds for photocoagulation of whole human blood were determined in glass capillary samples with measured oxygen saturation levels. Pulsed dye lasers at 585, 590, 595, 600, 633 nm, a 694 nm ruby laser, a 755 nm alexandrite laser, and a 1,064 nm Nd:Yag laser were used, all with 1.5–3 milliseconds pulse width and similar exposure spot size. Results Selectivity (a lower fluence threshold) for venous blood was maximal at 694 nm, and significant at 595, 600, 633, and 755 nm. At 633 nm, a wavelength with strong relative absorption by metHb, selectivity for venous blood was much less than expected. The Nd:YAG laser at 1,064 nm showed significant selectivity for arterial blood. Conclusion Preferential photocoagulation of venous blood is possible at wavelengths with a high Hb/HbO2 absorption coefficient ratio. Laser-induced metHb may also affect wavelength-dependent selective photothermolysis. Venular malformations such as port wine stains could potentially be treated more selectively with ∼630–780 nm sources. Nd:YAG laser pulses at 1,064 nm tend to affect arterial more than venous blood. Lasers Surg. Med. 44:152–157, 2012. © 2012 Wiley Periodicals, Inc.

Low Fluence Q-Switched Nd: YAG Laser Toning and Q-Switched Ruby Laser in the Treatment of Melasma:A Comparative Split-Face Ultrastructural Study.

Abstract: Background: Melasma still presents as a difficult entity to treat, especially in the Asian skin phe-notype. Recently laser toning with the Q-switched Nd:YAG has attracted attention. The present study investigated the efficacy of Q-switched Nd:YAG laser toning for melasma, with a histopathological comparison with the Q-switched ruby laser. Subjects and Methods: Eight Japanese females (41–57 yr, mean 52.5 yr) with Fitzpatrick skin type III and bilateral melasma participated in the study. One half of each subject's face (randomly chosen) was treated with Q-switched 1064 nm Nd:YAG laser toning (pulse width 5–20 ns; spot size, 6 mm diameter; fluence, 3.0 J/cm2, 5–7 passes, once/week, 4 weeks: QS:YAG group), and the contralateral half with a single treatment using a Q-switched ruby laser (694.5 nm, pulse width 20 ns, spot size 4 mm diameter; fluence 4.0 J/cm2, 1 pass with approximately 20% overlap: QS:Ruby group). Skin biopsies were taken immediately after the 4th Nd:YAG session and the single ruby session, and histopathological comparison was performed with light- and transmission electron microscopy (TEM). Results: Improvement in melasma pigmentation was seen in both the QS:YAG- and QS:Ruby-treat-ed sides, and this was well-maintained in the QS:YAG group. Ultrastructurally, melanin granules were destroyed in both groups, but there was considerably more morphological epidermal and dermal damage in the QS:Ruby specimens compared with minimal epidermal disruption and cellular damage in the QS:YAG specimens. Conclusions: Q-switched 1064 nm Nd:YAG laser toning offered superior results in the treatment of melasma in the Japanese skin type compared with the Q-switched ruby laser, both ultrastructurally with less immediately post-treatment cellular damage and macroscopically, and a longer recurrence-free interval.

Effects of laser irradiation on Trichophyton rubrum growth and ultrastructure.

Abstract: Background Trichophyton rubrum (T.rubrum) is the most common causative agent of dermatophytosis worldwide.In this study,we examined the effect of laser irradiation on the growth and morphology of T.rubrum.Methods Colonies of T.rubrum were isolated (one colony per plate),and randomly assigned to 5 treatment groups:Q-switched 694 nm ruby laser treatment,long-pulsed Nd:YAG 1064 nm laser treatment,intense pulsed light (IPL)treatment,308 nm excimer laser treatment and the blank control group without treatment.Standardized photographs were obtained from grown-up fungal plates prior to treatment.Colonies were then exposed to various wavelengths and fluences of laser light.To compare the growth of colonies,they were re-photographed under identical conditions three and six days post-treatment.To investigate the morphology of T.rubrum,scanning electron microscope (SEM) and transmission electron microscope (TEM) images were obtained from specimens exposed to 24 hours of laser treatment.Results Growth of T.rubrum colonies was significantly inhibited following irradiation by 694 nm Q-switched and 1064nm long-pulsed Nd:YAG lasers.Other treatments exerted little or no effect.Q-switched laser irradiation exerted a stronger growth inhibitory effect than long-pulsed Nd:YAG laser irradiation.Following treatment by the Q-switched ruby laser system,T.rubrum hyphae became shrunken and deflated,and SEM images revealed rough,fractured hyphal surfaces,punctured with small destructive holes.TEM images showed that the hyphae were degenerating,as evidenced by the irregular shape of hyphae,rough and loose cell wall,and obscure cytoplasmic texture.Initially high elect(io)n density structure was visible in the cell; later,low-density structure appeared as a result of cytoplasmic dissolution.In contrast,the blank control group showed no obvious changes in morphology.Conclusion The Q-switched 694 nm ruby laser treatment significantly inhibits the growth and changes the morphology of T.rubrum.

Optical-pyrometric diagnostics of the state of silicon during nanopulsed laser irradiation

Abstract: The dynamics of the reflectivity at λ = 0.53 μm and the IR radiation of silicon in the wavelength range 0.9–1.2 μm is studied under the action of nanosecond ruby laser radiation pulses. When radiation energy density W is lower than the threshold of laser-induced melting of the surface of a semiconductor crystal, the major contribution to the IR radiation emitted by this crystal is made by edge photoluminescence. As the melting threshold is exceeded, the nanosecond dynamics of the detected IR radiation changes from photoluminescence to the thermal radiation of the forming Si phase melt with a high reflectivity. The results of pyrometric measurements of the peak melt surface temperature as a function of W obtained at an effective wavelength λe = 1.04 μm of the detected IR radiation agree with the data of analogous measurements performed at λe = 0.53 and 0.86 μm.

A study of Roman glass from Mala Barutana/Belgrade Fortress irradiated with pulsed CO2, Nd:YAG and ruby laser — Comparison

Abstract: Application of non-contact and rapid laser technique, which is minimally invasive, non-contaminant and efficient method, for ancient glass investigation and cleaning is highly desirable for restoration purposes. Irradiation of Roman glass dated from 1st to 4th/5th century AD with TEA CO 2 (wavelength 10.6 μm; pulse duration t p = 100 ns), Nd:YAG (wavelength 1064 nm and 532 nm; t p = 150 ps) and ruby laser (wavelength 694 nm; t p = 30 ns) in air ambience was studied. For all three lasers, moderate energy densities (15–30 J/cm 2 ) induced significant changes of morphology — from superficial exfoliation and occurrence of mosaic structure after few pulses to deep damages and hydrodynamic features after higher number of accumulated shots. Irradiation with moderate energy density, accompanied with plasma appearance in front of the samples, is convenient for numerous potential applications, particularly surface elemental analysis such as laser induced breakdown spectroscopy. On the other hand, lower densities are more suitable for Roman glass cleaning. Calculations of Roman glass surface temperature have shown that pulsed CO 2 laser is favorable for surface cleaning and optimal fluence is ~ 2 J/cm 2 . This was confirmed by additional experiments for fluences 1.5 and 3 J/cm 2 . Morphological changes on the Roman glass surface induced by lasers were studied by optical microscopy (OM) and scanning electron microscopy (SEM). The composition of Roman glass was determined by energy dispersive X-ray analysis (EDX) and inductively coupled plasma (ICP) method. Chemical analysis confirmed that the investigated glass dates from the Roman period.

The evolution of quality-switched lasers.

Abstract: Quality-switched (QS) lasers and their applications have evolved greatly since the ruby laser's effect on tattoo ink was first reported in the 1960s. The 1983 description of selective photothermolysis explained the efficacy of QS lasers for the treatment of cutaneous pigmented lesions and tattoos and cemented their status as the gold standard for these targets. Within the past decade, the uses for QS lasers have expanded dramatically, including nonablative rejuvenation and the treatment of onychomycosis. Additional applications and refined techniques and technologies promise to maintain the stature of QS lasers as an integral part of the laser surgeon's arsenal.

Nonlinear Optical Frequency Mixing Theory

Abstract: The nonlinear optics mixing theory and technology have been well developed. As early as 1961, the theory of second harmonic wave was presented. Frequency doubling with ruby laser (694.3 nm) and ultraviolet radiation with 347.15 nm wavelength were achieved at the level of the conversion efficiency of only 10− 8. Later, the phenomenon of mixing between the two lasers with different frequencies (such as sum frequency, difference frequency, and optical rectification) was found, and the technology of phase matching was developed. After that, the higher conversion efficiencies of optical frequency doubling and optical mixing were achieved. Development of nonlinear mixing technology is closely connected with laser apparatus and technology. Emergence of lasers with newly discovered wavelengths present new requirement for nonlinear crystals and mixing technology. Also, the appearance ofQ-switch and ultra-short pulse technology made the peak power improved greatly, and the efficiency of frequency doubling reached 70–80%. On the other hand, the high peak power aroused the problems of laser damage threshold and the new task of expanding wavelength from infrared radiation to ultraviolet radiation. Optical frequency doubling, optical mixing, and optical parameter oscillation are important to realize frequency conversion in the laser technologies at present. If a tunable laser and a laser with fixed wavelength (or two tunable lasers) are mixed in the nonlinear crystal, new tunable wavelengths can be achieved. If the obtained new laser is used as pump source for tunable laser, optical parameter oscillator laser, or stimulated Raman scattering laser, further other new tunable wavelengths can be obtained. Optical mixing can expand the laser wavelength to the directions of ultraviolet radiation and infrared radiation.

Use of a Fractional Q-Switched Ruby Laser for Treatment of Facial Lentigines:

Abstract: Introduction:Fractional laser technology is associated with decreased posttreatment morbidity but has not been applied to Q-switched ruby lasers (694 nm). Standard Q-switched ruby lasers have been used effectively for the treatment of pigmented lesions but require postoperative wound care and significant recovery time. The objective is to report on the suitability of a new fractional handpiece for a Q-switched ruby laser for the treatment of facial lentigines.Materials and Methods:Five patients with facial lentigines were treated with or without topical anesthetic with a fractional Q-switched ruby laser at a fluence that caused tissue whitening.Results:Patients were treated 1 to 2 times. All patients experienced clinical improvement in hyperpigmentation with minimal posttreatment erythema and crusting.Conclusions:The fractional Q-switched ruby laser is an ideal treatment for facial lentigines, causing clinical improvement with minimal posttreatment morbidity.

Method of generating pulsed x-ray radiation

Abstract: FIELD: physics.SUBSTANCE: method of generating pulsed X-ray radiation involves focusing laser radiation of the ruby laser of an optical system and directing the radiation onto an opal matrix - an ordered structure made from silica with diameter of 0.2-0.4 mcm and cooled to 200 K. The inter-spherical nanocavities of the opal matrix are filled with a substance with permittivity of not less than 2.5 with filling factor in the range of 30-85%, and the laser radiation has power of 0.25-10 GW/cm.EFFECT: reduced angular divergence of the pulsed X-ray radiation.3 cl, 2 dwg, 2 tbl