Laser Technology

In this paper, a review of fiber laser technology as relevant for applications in ultrafast optics is given. We discuss core enabling fiber technologies, such as fiber amplifiers, all-fiber dispersion control, and highly nonlinear and large-core fibers. We concentrate on systems built around passively mode-locked fiber lasers and fiber frequency combs, which are further amplified in large-core fiber amplifiers. Our review further encompasses coherent supercontinuum generation and techniques for absolute phase control of fiber lasers and amplifiers. Applications concerned with spectral generation in the range from the vacuum UV to the terahertz range are also described.

PURPOSE To study the distribution and predominant orientations of fibrillar collagen at different depths throughout the entire thickness of the human cornea. This information will form the basis of a full three-dimensional reconstruction of the preferred orientations of corneal lamellae. METHODS Femtosecond laser technology was used to delaminate the central zones of five human corneas into three separate layers (anterior, mid, and posterior stroma), each with predetermined thicknesses. Wide-angle x-ray diffraction was used to study the gross collagen fibril orientation and distribution within each layer. RESULTS The middle and posterior parts of the human cornea demonstrated a preferential orthogonal arrangement of collagen fibrils, directed along the superior-inferior and nasal-temporal meridians, with an increase in the number of lamellae toward the periphery. However, the anterior cornea (33% of total corneal thickness) showed no systematic preferred lamellar orientation. CONCLUSIONS In the posterior two thirds of the human cornea, collagen lies predominantly in the vertical and horizontal meridians (directed toward the four major rectus muscles), whereas collagen in the anterior third of the cornea is more isotropic. The predominantly orthogonal arrangement of collagen in the mid and posterior stroma may help to distribute strain in the cornea by allowing it to withstand the pull of the extraocular muscles, whereas the more isotropic arrangement in the anterior cornea may play an important role in the biomechanics of the cornea by resisting intraocular pressure while at the same time maintaining corneal curvature.

BACKGROUND A new method for treating facial rhytides and acne scars with nonablative laser and light source techniques has recently been introduced. Given the inherent limitations of photographic and clinical evaluation to assess subtle changes in rhytides and surface topography, a new noninvasive objective assessment is required to accurately assess the outcomes of these procedures. OBJECTIVE The purpose of this study was to measure and objectively quantify facial skin using a novel, noninvasive, In-vivo method for assessing three-dimensional topography. This device was used to quantify the efficacy of five treatment sessions with the 1064 nm QS Nd:YAG laser for rhytides and acne scarring, for up to six months following laser treatment. METHODS Two subjects undergoing facial rejuvenation procedures were analyzed before and after therapy using a 30-mm, three-dimensional microtopography imaging system (PRIMOS, GFM, Teltow, Germany). The imaging system projects light on to a specific surface of the skin using a Digital Micromirror Device (DMD™ Texas Instruments, Irving, TX) and records the image with a CCD camera. Skin Surface microtopography is reconstructed using temporal phase shift algorithms to generate three-dimensional images. Measurements were taken at baseline, at various times during the treatment protocol, and then at three and six-month follow-up visits. Silicone skin replicas (FLEXICO, Herts, England) were also made before and after the laser treatment protocol for comparison to In-vivo acquisition. RESULTS Skin roughness decreased by 11% from baseline after three treatment sessions in the wrinkles subject, while a 26% improvement of skin roughness was recorded by 3D In-vivo assessment six months following the fifth treatment session. The subject with acne scarring demonstrated a 33% decrease in roughness analysis after three treatment sessions by 3D In-vivo assessment. A 61% improvement in surface topography was recorded 3-months following the fifth treatment session, which was maintained at the 6-month follow-up. CONCLUSION Three-dimensional In-vivo optical skin imaging provided a rapid and quantitative assessment of surface topography and facial fine lines following multiple treatment sessions with a 1064-nm QS Nd:YAG laser, correlating with clinical and subjective responses. This imaging technique provided objective verification and technical understanding of nonablative laser technology. Wrinkle depth and skin roughness decreased at the three and six-month follow-up evaluations by 3D In-vivo assessment, indicating ongoing dermal collagen remodeling after the laser treatment protocol. Future applications may include comparison of nonablative laser technology, optimization of treatment regimens, and objective evaluation of other aesthetic procedures performed by dermatologists.

Although there are a considerable number of published papers on the role of laser treatment in dentistry, a critical review shows that laser technology is used only by specialists in a small therapeutic field. Most lasers are heat-producing devices converting electromagnetic energy into thermal energy. These lasers find uses in oral surgery for cutting or coagulating soft tissues or in the welding of dental prostheses. More recently, new types of lasers have offered non-thermal modes of tissue interaction, called photoablation, photodisruption and photochemical effects. Basic and clinical research is being carried out into the application of these devices in dentistry. However, much development will be required before lasers can replace conventional surgical methods for treating oral cancer or indeed replace the conventional bur for excavating carious lesions.

PURPOSE To evaluate the accuracy of a digital impression system based on parallel confocal red laser technology, taking into consideration clinical parameters such as operator experience and angulation and depth of implants. MATERIALS AND METHODS A maxillary master model with six implants (located bilaterally in the second molar, second premolar, and lateral incisor positions) was fitted with six polyether ether ketone scan bodies. One second premolar implant was placed with 30 degrees of mesial angulation; the opposite implant was positioned with 30 degrees of distal angulation. The lateral incisor implants were placed 2 or 4 mm subgingivally. Two experienced and two inexperienced operators performed intraoral scanning. Five different interimplant distances were then measured. The files obtained from the scans were imported with reverse-engineering software. Measurements were then made with a coordinate measurement machine, with values from the master model used as reference values. The deviations from the actual values were then calculated. The differences between experienced and inexperienced operators and the effects of different implant angulations and depths were compared statistically. RESULTS Overall, operator 3 obtained significantly less accurate results. The angulated implants did not significantly influence accuracy compared to the parallel implants. Differences were found in the amount of error in the different quadrants. The second scanned quadrant had significantly worse results than the first scanned quadrant. Impressions of the implants placed at the tissue level were less accurate than implants placed 2 and 4 mm subgingivally. CONCLUSIONS The operator affected the accuracy of measurements, but the performance of the operator was not necessarily dependent on experience. Angulated implants did not decrease the accuracy of the digital impression system tested. The scanned distance affected the predictability of the accuracy of the scanner, and the error increased with the increased length of the scanned section.

OBJECTIVE Determination of the efficacy of pulsed Alexandrite Laser technology for rapid noninvasive hair removal. SUMMARY BACKGROUND DATA Although previous studies have already shown that Ruby lasers are capable of noninvasive hair removal, a technology for the substantial increase of treatment speed is of great interest. METHODS We have used a 2 msec free running pulsed Alexandrite (lambda = 755 nm) laser operated at a repetition rate of up to 5 pps at energy fluences of 25-40 J/cm2 to treat a wide range of body sites on 126 patients in conjunction with a fiber delivery system and a transparent target ruler. A transparent gel was used as epidermal heat sink. The study lasted 15 months. Pretreatment as well as follow-up hair count per cm2 was performed to determine the level of success. Treatments were repeated when 1-2 mm growth was observed. RESULTS The average hair count before the second treatment was found to be close to 65% of the pretreatment count. The average hair count 3 months after the last treatment, was found to be lower than 12%. The interval between treatments ranged from 4 weeks to 3 1/2 months. CONCLUSIONS The 2 msec pulsed Alexandrite laser technology is effective for the removal of unwanted hairs, ranging from fair to dark, except when hairs are absent in the shaft depending on the stage of their growth cycle. This results in the necessity of a few treatments or touchups. Adverse effects are minimal and transient.

PURPOSE To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures. METHODS Literature review. RESULTS From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use. CONCLUSIONS Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

AbstractAfter decades of research and development, a fully automated system for pavement crack detection with an intensity-based two-dimensional (2D) imaging data acquisition system under different lighting and low intensity contrast conditions still remains a challenge. With the advances of sensor technology, a three-dimensional (3D) laser technology that can collect high-resolution 3D continuous transverse pavement profiles for detecting cracks on the basis of their 3D elevation rather than 2D intensity has become available. This study, sponsored by the U.S. Department of Transportation (US DOT) Research Innovative Technology Administration (RITA) program, evaluates the feasibility of using emerging 3D laser technology to detect cracks under different lighting and poor intensity contrast conditions. For this purpose, 3D surface data from laboratory tests on cracks ranging from 1 to 5mm wide and tests on the actual pavement cracks of different widths and depths and under different lighting conditions wer...

Preface. Acknowledgments. An Overview of Laser Technology. The Nature of Light. Refractive Index, Polarization, and Brightness. Interference. Atoms, Molecules, and Energy Levels. Energy Distributions and Laser Action. Laser Resonators. Resonator Modes. Reducing Laser Bandwidth. Q--Switching. Cavity Dumping and Modelocking. Nonlinear Optics. Semiconductor Lasers. Solid--State Lasers. Helium Neon, Helium Cadmium, and Ion Lasers. Carbon Dioxide and Other Vibrational Lasers. Excimer Lasers. Tunable and Ultrafast Lasers. Glossary. Index. About the Authors.

We describe a novel, minimally invasive laser technology for skin rejuvenation by creating isolated microscopic lesions within tissue below the epidermis using laser induced optical breakdown. Using an in‐house built prototype device, tightly focused near‐infrared laser pulses are used to create optical breakdown in the dermis while leaving the epidermis intact, resulting in lesions due to cavitation and plasma explosion. This stimulates a healing response and consequently skin remodelling, resulting in skin rejuvenation effects. Analysis of ex‐vivo and in‐vivo treated human skin samples successfully demonstrated the safety and effectiveness of the microscopic lesion creation inside the dermis. Treatments led to mild side effects that can be controlled by small optimizations of the optical skin contact and treatment depth within the skin. The histological results from a limited panel test performed on five test volunteers show evidence of microscopic lesion creation and new collagen formation at the sites of the optical breakdown. This potentially introduces a safe, breakthrough treatment procedure for skin rejuvenation without damaging the epidermis with no or little social down‐time and with efficacy comparable to conventional fractional ablative techniques. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)