Generally, the beam distribution in the tissue in interaction with a pulsed laser is defined by the optical properties
(effective scattering and absorption coefficient). A special Er:YAG device used for blood sampling without any pain is
presented. Our device emitting on 2940 nm has a special function. It can give four energy levels for four types of skin.
At 3000 nm there is an absorption peak in water, and the absorption in tissue is intense and the vaporization is immediate
and superficial without surrounding damages. Additionally, the very short duration of the pulse (a few hundred
microseconds) avoids the phenomenon of thermal diffusion.
Artificial lighting for plants cultivation is an important factor that can determine the nutritional quality of vegetables. The
improvement of quality is determined by the emission spectrum of LED, suitable for vegetables. This spectrum values
must be inside the solar ones. So, by using red high-power LEDs we can supplement the conventional lighting (ex. HPS)
and we can enrich the red light from the emission light. We have used a special device that has 200 high-power red
LEDs, having emission wavelength in 640-670 nm range, which is presented below. Using red LEDs on tomato seeds,
we can observe that the germination rate significantly increased.
Laser diodes are lighting devices in which the light is generated by stimulated emission rather than spontaneous
emission, with high generation efficiency. A device using 20 red laser diodes is presented. Emission wavelengths are in
the 650-670 nm range. Emission power for each laser diode is about 4 mW. This device is used to irradiate the tomato
seeds with three different irradiating doses. There were three Petri vessels for each dose having 25 seeds each of them.
Results show that the germination rate increases for irradiated seeds. The red light has a positive effect for vegetable
cultivated in protected area.
To solve some microsurgical procedures in the anterior and posterior chambers using the photo disruptive effect, a
special Nd:YAG nanosecond laser device is presented. The Nd:YAG laser is q-switched (Cr4+:YAG). The laser beam is
expanded. After expansion, the laser beam is passed through a circular variable filter which is rotated by a processor,
allowing energy to be set at any value in the range of 0.5-10 mJ. Two infrared LED-phototransistor pairs are used to
position the filter. The laser beam is focused by the objective at 150 microns behind the object plane to avoid the damage
of the Intraocular Lens.
The study of dynamics of spatial solitons in nonlinear and unidimesional fotonic crystals, with a periodical and nonlinear
fotonic network which is generated by Dirac function is presented. Are analysed comparisons and differences which
appear in development of periodical models describes by nonlinear Schrödinger equation. Also, is developed theory of
couple models for periodical modulation of refractive index.
Fudamental theory of spatial solitons are based to obtain discrete nonlinear Schrödinger equation with analyze of
stationary solutions on discrete models.
Generally, the beam distribution in the tissue in interaction with a pulsed laser is defined by optical properties (effective
scattering and absorption coefficient). In 2900 nm range, the effective scattering coefficient is much smaller than the
absorption coefficient. An Er:YAG skin puncher is presented. Thermal action of a laser beam can be described as one of
three types: hyperthermia, coagulation and volatilization, depending on the degree and the duration of tissue heating. We
are interested in the volatilization process that means a loss of material. The various constituents of the tissue disappear
in smoke at above 1000C in a relatively short time of around one tenth of a second. At the edges of the volatilization zone
there is a region of coagulation necrosis. In presented case of an Er:YAG laser operating in a free generation mode, the
mechanical effects can result from explosive vaporization. When the exposure time of the laser is lower than the
characteristic time of the thermal diffusion in the tissue, it produces a thermal containment with an accumulation of heat
without diffusion and an explosive vaporization of the target. The Er:YAG laser device has the pulse length of about 160
microseconds and four emitted energy levels. This device is used to punch the skin for blood sampling for different kinds
of analysis. The front panel of the device has four keys to select the desired energy according to the skin type.
The Nd:YAG solid state laser can be used in ophthalmologic microsurgery because of its specific wavelength of 1064 nm, which has the property to penetrate the transparent medium of the eye. We design a specific ophthalmic system, containing a Q-switch Nd:YAG laser, an optical stereomicroscope and an aiming system. This laser-stereomicroscope system is used for eye examination and for microsurgical proceedings like posterior capsulotomy and pupilar membranectomy. We had to design an optical scheme of the laser to settle the radiation route. In order to cover the medical domain of the energies, we calibrate eleven attenuation filters using ratiometric method. For a correct position of the place where the laser pulse strikes, we used an original system consisting of two red laser diodes mounted on each side of the binocular One of the advantages of this laser system is taht the output energies can be varied widely (0.8-15 mJ), making a great numbers of applications in clinical ophthalmology possible.
An ophthalmic surgical instrument is presented. It contains a specific Q-switch YAG:Nd laser, an optical stereomicroscope, two red output laser diodes and a digital system for optical processing of the microscope images. As Q-switch, a Cr4+:YAG crystal is used. It works in monopulse or double pulse regime. Four red spots mark the optical object plane. The laser beam is sent in the central part, between four spots and is focused at 150 microns behind the optical plane to reduce the risk of pitting the lens when performing posterior capsulotomies. In order to obtain eleven different energy levels in the (2÷10)mJ domain, eleven attenuators are used. The laser ophthalmic system must fulfill many precautions. The energy level, the pulse length and the used attenuators must have such values to eliminate every undesired effect in the medical applications. This instrument has an important application in posterior capsulotomies and posterior membranectomies.
This paper presents some experimental results in order to give an interpretation of the action mechanism of laser radiation on biological tissue (especially vegetal tissue). Different types of woody plant tissue (Sequoia sp.) were irradiated with a low power 633 nm He-Ne laser beam. The laser power can be modified. The fresh weight of callus tissue increased about 70% as related to the untreated sample, when the laser's power was 10 mW. We observed that a 5 mW-laser power developed the bud differentiation. But, a significant promotion appeared for a higher laser powers (10 mW). The influence of laser radiation on the callus tissue growth process was detected also by the performing morphological and biochemical analysis.
For the low power laser therapy, the experiments show that better results are obtained when the laser beam is an overlapping of two radiations: one in the visible region of the spectrum and the other in IR region. Also, some experiments show that for good results in biostimulation it is important to have a high coherence length of laser beam; this is not the case of the laser diodes The He-Ne laser has the best coherence, being able to generate laser radiations in visible and IR. It has tow strong laser lines: 633 nm and 1.15 micrometers . Although their gains are about the same, the available power of the red radiation is 3-4 times higher because of its larger width, when they oscillate separately. Using special dichroic mirrors for simultaneous reflection of the both liens, the laser beam will consist of the two radiations, each of them having good coherence . A 420 mm active length, 1.8 mm inner diameter He-Ne laser tube and a special designed resonator has been developed. The mirrors reflect both radiations as follows: one reflects 99.9 percent and the other, the output mirror, reflects 98 percent. There is a competition between them because these lines have a common lower level. The output power of the laser beam as 6 mW for 633 nm and 4 mW for 1.15 micrometers , respectively.
A self-heating He-Se laser tube has been developed. It was all Pyrex, 60 cm active length, 2 mm ID. The laser beam consisted of seven green lines 28 mW total power. We have examined, by perturbation spectroscopy, the existence of amplification along the laser tube axis. The experimental set-up consisted of: laser tube, two laser mirrors dielectrically deposited for full reflection on 500 +/- 50 nm spectral region, a grating monochromator 0.2 nm resolution, a chopper, an EMI 9558QB photomultiplier and a lock-in amplifier. The spontaneously emitted light in the perpendicular direction to the tube axis has been monitored. The laser radiation field that exists in the active medium involves the decreasing of the upper laser level population and thus, the intensity of the corresponded spontaneously emitted line decreases too. Using the chopper, the laser beam is periodically interrupted so that, a modulation of the intensities of the spectral lines appears. The signal sign is opposite for amplification and absorption region, placed inside the metal reservoir, just where the metal vapors penetrate the discharge. Taking into account the energies of the involved levels, we have proposed reaction.
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