Andrzej Zajac

The concept of the set to objectification of LLLT exposure

In this article authors present the developed optoelectronic set for controlled, repeatable exposure by electromagnetic radiation of biological structures in the spectral band of tissue transmission window 600-1000 nm. The set allows for an objective selection and control of exposure parameters and comparison of results for variable energetic, spectral and polarization parameters of radiation beam. Possibility of objective diagnostics of tissue state during laser treatment was provided in the presented optoelectronic set.

Digital controlling system to the set of high power LEDs

In the paper is described the concept and architecture of the multi-channel control system for set of high-power LEDs. The broadband source of radiation for prototype illuminator is dedicated to the investigation of Low Level Laser Therapy procedures. The general scheme of the system, detailed schemes, control algorithm and its implementation description in FPGA structure is presented. The temperature conditions and the opportunity to work with a microcomputer are characterized.

Laser radiation sources applied to HpD diagnosis and therapy

The paper presents laser sets, including forsterite laser, applicable for the HpD therapy. We describe the laser sets pumped by the Q-switched Nd:YAG laser pulse, generating radiation within a therapeutic range and diagnostic one as well as the set generating within the q-W regime. We discuss the results of investigations carried out with the laser set for diagnosis. The set comprises the KZnF3 laser with a ruby pump. The forsterite laser pumped by the q-CW Nd:YAG laser, at 20 W of a pump power, can generate radiation of average power of about 400 mW at wavelength of (lambda) equals 1270 nm or radiation of average power of 150 mW at wavelength of 630 nm. The tunable range of the set is (lambda) equals +/- 20 nm FH and (Delta) (lambda) equals +/- 10 nm for the SH of forsterite laser. We have also analyzed other laser sets fulfilling requirements of the HpD diagnosis and therapy.

Optoelectronic set for measuring the absorption spectrum of the thin biological media

In the paper the authors present the developed optoelectronic system for controlled, repetitive exposure by electromagnetic radiation of biological structures in the Low Level Laser (LED) Therapy procedures. The set allows for objective selection and control of the irradiation parameters by light from spectral range of the tissues transmission window. Measurements of optical parameters of thin biological medium – spectral absorption coefficient and the amount of absorbed energy – can be implemented in the measuring chamber during irradiation treatment. The radiation source is the broadband illuminator consists of set of selected high power LEDs. The maximum optical power of single source is from 80 mW to 800 mW. Illuminator is controlled and powered by the multi-channel prototype control system, which allows independently control a current of each emitter. This control allows shaping spectral emission characteristic of broadband source in range 600-1000 nm. Illuminator allows providing in the working area of 700 cm2 a uniform distribution of optical power density, of 10 mW/cm2 for maximum. Set ensure uniform distribution of the spectral power density of up to 40 mW/nm.

Effect of low level laser therapy and high intensity laser therapy on endothelial cell proliferation in vitro: preliminary communication

Background: The main purpose of this study was to analyze the influence of power intensity and wavelength of Low Level Laser Therapy (LLLT) and HILT (High Intensity Laser Therapy) on endothelial cell proliferation. Material and methods: The tests were done on human umbilical vein endothelial cells (HUVEC). Cultures were exposed to laser irradiation of 660 nm and 670 nm at different dosages, power output was 10 – 40 mW as well as 820 nm with power 100 mW and 808 nm with power 1500 mW. Energy density was from 0.28 to 11,43 J/cm2. Cell proliferation of a control and tested culture was evaluated with a colorimetric device to detect live cells. The tests were repeated 8 times. Results: We observed good effects of LLLT on live isolated ECs and no effects in experiments on previous deep-frozen cultures. Also HILT stimulated the proliferation of HUVEC. Conclusion: Endothelial cells play a key role in vascular homeostasis in humans. We observed the stimulatory effect of LLLT and HILT on proliferation of HUVEC. Many factors influence the proliferation of EC, so is it necessary to continue the experiment with different doses, intensity and cell concentration.

2.94 μm Electro-Optically Q-Switched Er:YAG Laser with High Output Energy

A Q-switched Er:YAG laser was developed. At 3Hz repetition rate, pulses of 91.2ns duration and 137mJ energy were obtained. For 10Hz repetition rate 30mJ of output energy in single pulse was achieved.

High-power diode-pumped Yb-doped silica fiber laser generating in near-infrared range

In this paper high power Yb-doped double-clad fiber laser is presented. A Yb3+-silica fiber laser has been cladding pumped at 937 nm by a InGaAs semiconductor laser diode and operated with the slope efficiency of 73 ± 3% with respect to the incident pump power. We obtained 4 W cw-output power when working with 20-m long fiber with laser core in 7 μm diameter (cut-off wavelength - 1 μm) and pump core in 120 x 120 μm (rectangle-shaped, NA = 0.6). Yb-doping concentration has been at the level 3 - 10 • 1019 cm-3 and attenuation in laser core has been 8 - 12 dB/km. The fiber laser operated at 1084 nm.

Colorimetric characterization of the tunable LED-based light source at the output of the homogenizing rod

The best method to obtain uniform spectral characteristic for multi-emitter sources is to use integrating sphere as mixing element. In each point of exit window of such sphere the luminance and spectral characteristic are uniform. However price of integrating spheres are disadvantageous and the output power decreases dramatically with the increase their diameters. For this reason sometimes homogenizing rods are used when LEDs are used. In the paper we present the results of colorimetric characterization of low cost homogenizing rectangular-shaped rod applied in the tunable LEDbased source for endoscopic system. For each correlated color temperature (CCT) value we investigated changes of spectral power distribution (SPD) on the output surface of the homogenizing rod and variation of CCT while increasing the distance from the output of the rod. Results of these measurements enable efficient lighting of the working area and proper placement of optical fibers used to guide light to difficult-access objects.

Tunable white light source for medical applications

Development of light-emitting diodes has brought new possibilities in many applications, especially in terms of flexible adjustment of light spectra. This feature is very useful in construction of many devices, for example for medical diagnosis and treatment. It was proved, that in some cases LEDs can easily replace lasers during therapy of cancer without reduction of efficiency of this process. On the other hand during diagnosis process LED-based constructions can provide unique ability to adjust the color temperature of the output light while maintaining high color rendering. It allows for optimum surface contrast and enhanced tissue differentiation at the operator site. In the paper we describe the construction of the tunable LED-based source designed for application in endoscopy. It was optimized from the point of view of the color rendition for 5 different correlated color temperatures (illuminant A, D55, D65, 3500K and 4500K) with the restriction of very high (>90) values of general and specific color rendering indexes (according to Ra method). The source is composed of 13 light-emitting diodes from visible region mounted on the common radiator and controlled by dedicated system. Spectra of the components are mixed and the spectra of output light is analyzed. On the basis of obtained spectra colorimetric parameters are calculated and compared with the results of theoretical analysis.

Semiconductor lasers vs LEDs in diagnostic and therapeutic medicine

Semiconductor emitters are used in many areas of medicine, allowing for new methods of diagnosis, treatment and effective prevention of many diseases. The article presents selected areas of application of semiconductor sources in UVVIS- NIR range, where in recent years competition in semiconductor lasers and LEDs applications has been observed. Examples of applications of analyzed sources are indicated for LLLT, PDT and optical diagnostics using the procedure of color contrast. Selected results of LLLT research of the authors are presented that were obtained by means of the developed optoelectronic system for objectified irradiation and studies on the impact of low-energy laser and LED on lines of endothelial cells of umbilical vein. Usefulness of the spectrally tunable LED lighting system for diagnostic purposes is also demonstrated, also as an illuminator for surface applications - in procedure of variable color contrast of the illuminated object.