Use Of Such Lasers Research Articles

High-sensitivity and high-speed measurements of ultrashort pulses as short as 74 fs at 1.9 µm using a GRENOUILLE device.

Ultrashort laser pulse sources in the wavelength range of 1.8 to 2 µm have many potential applications including medicine, materials processing, and sensing. In the use of such lasers, a crucial task is to measure their pulse's temporal intensity and phase. Such measurement devices are most useful when they are simple to build and operate and also have high speed and high sensitivity. The GRENOUILLE measurement device with few components, no moving parts, sensitivity of hundreds of picojoules, and measurement speed of hundreds of milliseconds, is commonly used to solve this problem at other wavelengths. In this paper, the measurement of ultrashort pulses by a GRENOUILLE device, developed using a silicon matrix sensor, for pulses in the wavelength range of 1.8 to 2 µm has been demonstrated. It is shown that ultrashort pulses with durations of 74 to 900 fs and a maximum spectral FWHM of 85 nm can be measured with this device. The recently developed ultra-reliable RANA approach was used for pulse retrieval from the measured traces. The device's performance was validated by comparing its measurements with those obtained by the robust FROG technique.

Thermo-optical properties of EuF2-based crystals

High-power solid state lasers of the mid-IR spectral range are extremely interesting for both basic research and technological applications and they are actively developing at present. However, the implementation of projects with the use of such lasers is hampered by the absence of Faraday isolators (FIs) for the radiation with the corresponding characteristics. The need for such devices is growing with laser power enhancement. They reduce the risk of self-excitation of the damage of amplifiers and optical elements and are a handy tool for organizing multipass schemes. Magneto-active crystals based on Eu2+ ions are promising media for the development of FIs for high-power lasers of the mid-IR spectral range because of the unique combination of their spectral and magneto-optical properties. Thermo-optical characteristics are also of principal importance when operating with high-power laser radiation. This letter presents the results of investigation of thermo-optical constants Q and P of the EuF2.11 solid solution crystal which determines the values of polarization and phase distortions of passing laser radiation. The measured values can be considered as the corresponding values for the EuF2 crystal, which is of greatest interest for the development of FIs for high-power mid-IR lasers. The obtained results can be used to determine the characteristics of FIs based on EuF2 crystals in various implementations of their optical schemes for various parameters of laser radiation. According to the estimates, for the radiation wavelength of 2 μm, the maximum permissible laser power of the Faraday isolator based on one magneto-optical element with [001] orientation will be more than 200 W.

Analysis of the Damage Mechanism Related to CO2 Laser Cochleostomy on Guinea Pig Cochlea.

Different types of lasers have been used in inner ear surgery. Therefore, it is of the utmost importance to avoid damage to the inner ear (e.g., hyperthermia and acoustic effects) caused by the use of such lasers. The aim of this study was to use a high powered fibre-enabled CO2 laser (10 W, 606 J/cm2) to perform cochleostomies on guinea pig cochlea and to investigate the possible laser-induced damage mechanisms. The temperature changes in the round window membrane, auditory evoked brainstem response, and morphological of the hair cells were measured and recorded before and after laser application. All of the outcomes differed in comparison with the control group. A rise in temperature and subsequent increased hearing loss were observed in animals that underwent surgery with a 10 W CO2 laser. These findings correlated with increased injury to the cochlear ultrastructure and a higher positive expression of E-cadherin and β-catenin in the damaged organ of Corti. We assume that enhanced cell-cell adhesion and the activated β-catenin-related canonical Wnt-signalling pathway may play a role in the protection of the cochlea to prevent further damage.

Low-cost scheme for high-precision dual-wavelength laser metrology

A method capable of delivering relative optical path length metrology with nanometer precision is demonstrated. Unlike conventional dual-wavelength metrology, which employs heterodyne detection, the method developed in this work utilizes direct detection of interference fringes of two He-Ne lasers as well as a less precise stepper motor open-loop position control system to perform its measurement. Although the method may be applicable to a variety of circumstances, the specific application in which this metrology is essential is in an astrometric optical long baseline stellar interferometer dedicated to precise measurement of stellar positions. In our example application of this metrology to a narrow-angle astrometric interferometer, measurement of nanometer precision could be achieved without frequency-stabilized lasers, although the use of such lasers would extend the range of optical path length the metrology can accurately measure. Implementation of the method requires very little additional optics or electronics, thus minimizing the cost and effort of implementation. Furthermore, the optical path traversed by the metrology lasers is identical to that of the starlight or science beams, even down to using the same photodetectors, thereby minimizing the noncommon path between metrology and science channels.

Explosive Sensing Using Polymer Lasers

Conjugated polymers are attractive materials that have been used to make a wide range of optoelectronic devices. Recently they have been used as explosive sensors as there is currently an urgent need for high sensitivity explosive detection due to the increased security issues across the world. This review outlines the attractive properties of organic polymers as gain media in lasers, and then focuses on the use of such lasers for explosive sensing applications. The combined advantages of fluorescent polymers and lasing promise explosive sensors with strongly enhanced sensitivity.

The Safe Use of Ultraviolet Lasers in Industry and Research

UV lasers are being applied to a number of industries, including metrology and manufacture. The safety issues from the use of such lasers are discussed. A risk assessment methodology is described which takes account of the different stages of the life cycle of the laser application, the different people at risk and the individual components of the laser application. In this way, the specific hazards can be identified and addresses to ensure that the risks are adequately managed.

LASER PHYSICS ELEMENTS TO CONSIDER FOR LOW LEVEL LASER THERAPY

A brief review is made about the properties of the laser radiation, with particular emphasis on their importance in low level laser therapy. An important part of this section is dedicated to the properties of the laser beams emitted by the semiconductor lasers (laser diodes or diode lasers) given the broad use of such lasers in low level laser therapy. The basic elements about the laser beam interaction with the tissues are introduced in close connection with the penetration depths of the laser beams into the target tissues. A general scheme of a medical laser equipment is introduced, according to the author’s experience, insisting on the requirements which result from the need to deliver to the medical doctors friendly, easy to use laser medical equipment. The simple formula used to compute the doses for tissue exposure at laser radiation with specific comments dedicated to the low level laser therapy applications are introduced. Lasers and laser medical products classes are introduced in connection with the laser safety rules to be considered while using the products for therapy applications. The practical rules recommended for the safe use of medical laser equipment are specified based on the author’s experience and recommendations for room arrangement and instrument selection in medical praxis related to the laser medical applications are given. The laser safety practical rules for the patients and the medical personnel are specified in direct connection with the current laser medical applications.

Pulse-periodic and cw CO2lasers pumped with a self-sustained pulsed discharge for use in heat processing

A description is given of the construction and radiation characteristics of fast-flow pulse-periodic (with an output power of up to 3.5 kW) and cw (up to 1.8 kW) CO2 lasers excited by a self-sustained pulsed discharge. For the first time, a laser pulse duration of up to 5 msec was obtained and a cw modulated output regime was realized when the active medium was excited with short (1–3μsec) discharge pulses. Examples are given of the use of such lasers for heat processing.

Advances in gastrointestinal endoscopy and laser therapy; the way ahead.

Modern flexible fibreoptics enable gastroenterologists to visualise and treat many lesions and conditions in the upper gastrointestinal tract and colon. Therapeutic endoscopy is forming a larger proportion of many unit's workload and the newer techniques to stop or prevent rebleeding are the subject of much research and development. Developments in the fields of operative endoscopy, small intestinal endoscopy, and endoscopic ultrasound are also progressing rapidly. The place of video-endoscopy is still to be established but potentially has several advantages over fibreoptic endoscopy. Laser therapy has been well established as a means of treating gastrointestinal haemorrhage from peptic ulcers, and has potential use in the treatment of angiomatous lesions. It is increasingly being used both for palliation and 'cure' of malignancy and neoplasia in the gastrointestinal tract. The use of such lasers depends upon thermal damage, but newer types of non-thermal laser therapy, using pulsed lasers, or dye lasers with prior tumour sensitisation are rapidly going to be applied to the treatment of gastrointestinal disease.

Mutual quenching of axial modes in two-mode lasers

An analysis is made of stimulated emission from active two-level particles with a homogeneously broadened transition line in a two-mode axial optical resonator. It is assumed that the particles fill the volume where the spatial structures of the mode fields are similar and that the intermodal beat period exceeds the relaxation time of the populations of the particle energy levels. The range of existence of two different (mutually exclusive) stable single-frequency emission regimes is determined and the hysteresis in the system is discussed. The use of such lasers as optical memory elements and logic devices is proposed.