He-Ne Gas Laser Research Articles

Out-put Characteristics of Low Power He-Ne Laser Efficiency Determination

        It is known that any laser has a pumping source, an amplifying medium and a resonator that oscillates the active mode representing the out-put wavelength of the laser. The suitable value for this ratio is 7:1 He/Ne in volume. These were to prepare under an ideal mixture of these gases as treated before by many experiment lists. The aim of this study to specify is to the basic portions of low power He-Ne gas lasers available in laboratories, and to test them in order to look for a probable factor of the efficiency as the whole. All calculations were performed, using calculators. The results were unique for all of them that the laser aperture also plays an important role in this criteria. The best fitting ratio between the radius of laser aperture and that of laser beam was determined and connected to the other parts of the efficiency, also the ratio of(ρ/ω) was fixed at 1.55.

A He-Ne gas laser with tunable wavelength and stable output intensity based on photon tunneling

In this paper, we report on a wavelength modulation He-Ne gas laser with stable output intensity. Wavelength modulation of the laser is achieved by modulating the length of the resonator cavity. And photon tunneling is used to change the loss of the cavity, namely, to modulate the laser output intensity. Then, the closed-loop feedback control technique is adopted to ensure the output intensity is stable when the laser wavelength is being modulated. Photon tunneling shows a significant control effect on the output light intensity of the laser. Finally, compared to a laser without feed-back control, the output stability of the wavelength modulation laser with feed-back control is an order higher in magnitude than that of the former, as average standard deviation of the output intensity decreases to a thirtieth of the original. In addition longitudinal mode characteristics and beam quality of the laser is measured. The measuring results show that it has two longitudinal modes and an excellent beam quality as the value of M2 factor is 1.029.

Frequency stabilized HeNe gas laser with 3.5 mW from a single mode

This paper describes an optical frequency stabilization technique using a three-mode Helium Neon laser at 632.8 nm. Using this configuration, a maximum frequency stability relative to an iodine stabilized laser of 6×10 -12 (71 s integration time) was achieved. Two long term measurements of 62 h and 40 h showed fractional frequency fluctuations of 6.2×10 -10 (2?) and 1.6×10 -10 (2?) when correcting for known frequency fluctuations outside the controller bandwidth, respectively. This stabilization scheme maximizes the available optical power (1.7 mW in this instance) because the output mode is in the center of the HeNe gain curve. This stabilization technique was also verified for a larger HeNe laser with a lower free spectral range. While not optimized for this configuration and laser, we demonstrated fractional frequency fluctuations below 1×10 -8 with 3.5 mW of usable output power. This is useful for multi-axis systems or systems employing fiber coupling. In this paper, the overall system is described and data containing the frequency locking signal sensitivity, profile during laser warm up, sensitivity to environmental fluctuations, and optical power of the locking signal is shown. © 2011 Elsevier Inc. All rights reserved.

Determination of blood glucose concentration by back propagation neural network

This paper presents a supervised backpropagation neural (BPN) network for the determination of blood glucose in diabetic patients. Non- invasive measurement of blood glucose concentration based on reflected laser beam from the index finger has been reported in this paper. This method depends on Helium-Neon (He-Ne) gas laser operating at 632.8 nm wave length. During measurement the index finger is placed in the laser beam transceiver unit, the reflected optical signal is converted into its corresponding electrical signal and the obtained signal is processed by the neural network which presents the results in the form of blood glucose concentration. Diabetes database used for empirical comparisons and the results are shown that BPN network performs better. Keywords: Artificial neural network, diabetes mellitus, non-invasive measurement, supervised learning.

Determination of blood glucose concentration by back propagation neural network

This paper presents a supervised backpropagation neural (BPN) network for the determination of blood glucose in diabetic patients. Non- invasive measurement of blood glucose concentration based on reflected laser beam from the index finger has been reported in this paper. This method depends on Helium-Neon (He-Ne) gas laser operating at 632.8 nm wave length. During measurement the index finger is placed in the laser beam transceiver unit, the reflected optical signal is converted into its corresponding electrical signal and the obtained signal is processed by the neural network which presents the results in the form of blood glucose concentration. Diabetes database used for empirical comparisons and the results are shown that BPN network performs better.

Gelation mechanism of ultra-high-molecular-weight polyethylene (UHMWPE) chains in dispersion solutions containing multiwall carbon nanotubes (MWNTs) analyzed in terms of liquid-liquid phase separation

Abstract Gelation mechanisms of ultra-high-molecular-weight polyethylene (UHMWPE) in dispersion solutions containing multiwall carbon nanotubes (MWNTs) were investigated in terms of liquid-liquid phase separation mechanisms. When an incident beam of He-Ne gas laser was directed to the dispersion solution quenched to a desired temperature, the logarithm of scattered intensity increased linearly with elapsing time and tended to deviate from this linear relationship. The two different increasing behaviors of the scattered intensity were termed as initial and latter stages, respectively, of the phase separation. The linear increase in logarithmic light-scattered intensity was analyzed within the framework of the linear theory of spinodal decomposition in terms of the viewpoint that the quenched solution becomes thermodynamically unstable and tends to incur phase separation to resolve the unstable state. The growth rate of the concentration fluctuation of neat UHMWPE solution (without MWNTs) calculated from the slope of linear increase was faster than that of the dispersion solution. In spite of the rapid growth rate, however, the gelation time of the dispersion solution was much shorter than that of the neat UHMWPE solution and the gelation and quasi-spinodal temperatures were slightly higher. These phenomena were in contradiction with the result of the concentration fluctuation. This contradiction was thought to be due to the fact that diffused UHMWPE chains in the dispersion solution were gelled easily on the MWNT surface rather than the gelation by self-coagulation.

Development of Miniaturized Fiber-Optic Laser Doppler Velocimetry Sensor for Measurement of Local Blood Velocity (Measurement of Human Whole Blood Velocity in Modeled Blood Vessel Using Fiber-Optic Sensor Having Convex Lens-like Tip)

In order to measure local blood velocity in artery and vein, a miniaturized fiber-optic LDV sensor has been newly developed. In the present fiber-optic sensor, laser beam emitted from the fiber tip can be focused at any position from about 0.1 to 0.5 mm distant from the fiber tip, and moreover a stray light or an unfavorable reflected light inside the light transmission system is remarkably decreased. Consequently the present sensor has a sufficiently high signal-to-noise ratio, and is capable of measuring the local velocity in almost all semi-opaque and opaque fluids including blood. The sensor head, i.e. the optical fiber is incorporated into either a injection needle or a catheter tube. In the former case, it is inserted inclinatorily from the wall into the vessel, and is made a tilted scan across the vessel to measure a velocity distribution. In the latter case, it is kept parallel to the flow in the vessel. In all the flows of whole human blood, whole caprine blood and a RC-MAP (red cell / Mannitol-Adenine-Phosphate) of bovine, of which hematocrit is 69%, the volocity distribution across the vessel can be very accurately measured. The insertion angle of the fiber to the flow has a significant effect on the measurement accuracy, and the appropriate angle is about 100 degree in the injection needle type. In the catheter type, the insertion direction adverse to the flow is better than that parallel to the flow because of an effect of wake behind the fiber tip. The influence of light source, i.e. a He-Ne gas laser and a He-Ne laser diode on the measurement accuracy is small.

Phase Separation of Several Kinds of Polyethylene Solution under the Gelation/Crystallization Process

The gelation mechanism of polyethylene solutions was investigated by using light scattering and X-ray diffraction techniques in terms of the liquid-liquid phase separation. Three kinds of polyethylene, ultrahigh molecular weight polyethylene (UHMWPE), low molecular weight linear polyethylene (L-LMWPE), and low molecular weight branched polyethylene (B-LMWPE), were used as test specimens. When an incident beam of He-Ne gas laser was directed to the UHMWPE and B-LMWPE solutions quenched to a desired temperature, the logarithm of scattered intensity increased linearly in the initial stage and tended to deviate from this linear relationship in the latter stage. If the linear increase in the initial stage can be analyzed within the framework of the linear theory of spinodal decomposition proposed by Cahn, the gelation is obviously attributed to the phase separation leading to the concentration fluctuation of the solution. Furthermore, in the later stage showing the deviation from the linear relationship, light scattering from the UHMWPE solution with 0.5% concentration under Hv polarization condition showed an X-type pattern, indicating the appearance of optically anisotropic rods. On the other hand, the scattering from the B-LMWPE solution with 3% concentration showed a four-leaf clover pattern, indicating the appearance of optically anisotropic spherulites. No crystallite was confirmed by the X-ray diffraction measurements, when the rods and spherulites appeared. With further lapse of time, the Hv patterns became clearer and the corresponding X-ray diffraction intensity curves showed a very small diffraction peak from the (110) plane. In contrast, for the L-LMWPE solutions, the logarithm of scattered intensity against time showed a rapid increase and tended to level off because of rapid change from slightly transparent to whiten gels. In such a process, any quantitative analysis of the scattered light intensity was impossible. The corresponding X-ray diffraction revealed the strong reflections from the (110) and (200) planes, indicating the rapid formation of stable crystallites. Through a series of experiments for the three kinds of polyethylene solution, it turned out that gelation mechanism of polyethylene solutions is strongly affected by molecular weight and the degree of branching.

Density Fluctuation of the Amorphous Region of Poly(ethylene terephthalate) Films by Quasi-Spinodal Decomposition

Crystallization of polymers was studied in terms of density fluctuation of amorphous phase by using amorphous poly(ethylene terephthalate) (PET) films in disoriented and oriented states. When the amorphous film was put into a hot oven with desired temperature and an incident beam of He-Ne gas laser was directed to the film, the scattered intensity against time was classified into three regions. In the first stage, the scattered intensity hardly changed. In the second stage, the logarithm of scattered intensity increased linearly. This tendency was apparently in accordance with concentration fluctuation of linear theories of spinodal decomposition (SD) originally proposed by Cahn for small molecules and that modified by de Gennes for the polymer system which describe the initial stage in the phase separation process. In the third stage, the increase in intensity started to deviate from the linear relationship and tended to level off. The scattering maximum increased with time and maintained at the same scattered vector in stage II and then tended to shift toward a lower angle in stage III, characterizing SD. Surprisingly, the above phenomenon indicates that the observation scale of the density fluctuation associated with the driving force of the crystallization process was several thousand nanometers. Such behavior was quite different from the density fluctuation at smaller scales detected by X-ray diffraction and scattering. On the basis of the second stage, the apparent spinodal temperatures (T s ) could be estimated from the dynamics measured as a function of temperature for undrawn and drawn PET films. The growth rate maximum of the density fluctuation was independent of the scattered vector q and increased with annealing temperature. This indicates that the phase separation due to density fluctuation occurs in thermodynamic unstable state and crystallization takes place partially in the higher density region of amorphous chains. This mechanism is different from crystallization associated with nucleation and growth. To demonstrate this concept in detail, further analysis was done by using wide-angle X-ray diffraction, differential scanning calorimetry, and small-angle light scattering under polarization conditions and density measurement.

Acousto-optic modulator for IR diode laser radiation

A new amorphous Si20Te80 glass alloy with high optical transparency has been synthesized and investigated. A modulator based on the amorphous Si-Te acousto-optic cell and operating in the mid-IR region has been manufactured and tested using CO2 (10.6 µm), He-Ne (3.39 µm) gas lasers and 3.3 µm (based on InGaAsSb/InAsSbP double heterostructure), and 1.87 µm (based on GaInAsSb) diode lasers. The modulator response time appeared to be not more than 0.3 µs which together with the high modulation efficiency (up to 90%) make possible use in many applications, e.g. for modulation of CW laser radiation, for optical gas sensor applications, for diode laser spectroscopy to make mode selection of wavelength selection within a lasing pulse.

Response Characteristics of the Particle Measuring Systems Active Scattering Aerosol Spectrometer Probes

Predictions of the size response of various light-scattering aerosol counters manufactured by Particle Measuring Systems are reported. Models that exploit the high intensity of light available within the cavity of a He-Ne gas laser (generically referred to by the manufacturer as ''active scattering aerosol spectrometer probes'') are considered. The new response function properly averages over particle trajectories through nodes, antinodes, and intermediate regions of the intracavity laser beam. Our studies address probes having two basic scattering geometries: those that collect light scattered over a relatively narrow solid angle (subtending angles between 4° and 22° from the laser beam axis, as in the model ASASP-300 and ASASP-300X probes) and those that collect light over a rather large solid angle (between 35° and 120° , as in the ASASP-X, ASASP-100X, LAS-250X, LAS-X, and HS-LAS probes). The theoretical response predictions for both narrow-angle and wide-angle probes are compared to previous measurements of monodisperse test aerosols of polystyrene latex, dyoctylphthalate, nigrosin dye, and carbon black. The new response function predicts smoother dependence on particle size than the previous response function of Pinnick and Auvermann (1979) and is in better agreement with measurement. Response calculations for common atmospheric aerosol (water, sulfuric acid, ammonium sulfate, and black carbon) reveal the considerable sensitivity of the response to particle dielectric properties. Response functions for internal mixtures (black carbon inclusions in water droplets, quartz in sulfuric acid, carbon in ammonium sulfate, and metal in sulfuric acid) are somewhat different than those for homogeneous particles. Comparison of response calculations with the manufacturer's calibration reveal conditions for which the manufacturer's calibration is most appropriate and the potential for errors (as much as a factor of two in sizing) when it is blindly applied. Finally, response functions for multiline laser operation, as the manufacturer suggests might be appropriate for the HS-LAS and LAS-X probes, are nearly the same as for single-line lasing. These results should help the user of these instruments to more realistically interpret size distribution measurements.

Killing of the Yeast and Hyphal Forms of Candida albicans Using a Light-Activated Antimicrobial Agent

Oral infections due to Candida albicans are a common occurrence in patients with acquired immunodeficiency syndrome (AIDS). The purpose of this investigation was to determine whether the yeast and hyphal forms of the organism could be killed using the light-activated antimicrobial agent toluidine blue O (TBO). Three variables were investigated: TBO concentration, laser light dose and pre-irradiation time (PIT). Irradiation with light from a helium neon (HeNe) gas laser used in conjunction with the photosensitiser TBO resulted in substantial kills of both the yeast and hyphal forms. Killing was light dose-dependent with 42 J being the most effective dose. The optimum PIT for the yeast form was 5 min, whereas killing of the hyphal form was not affected by PIT. The results of this study have shown that both forms of C. albicans are susceptible to lethal photosensitisation using TBO in conjunction with HeNe laser light, suggesting the possibility that this approach could be useful for eliminating the organism from diseased lesions in vivo.

635 nm 20 mW DFB laser

The shortest wavelength room temperature operation in an electrically pumped DFB laser is demonstrated. The InGaAlP device emits up to 20 mW in a single spatial and longitudinal mode under CW conditions. Such lasers can substitute for bulky He-Ne gas lasers for meteorological and spectroscopic applications.

Compatibility of mixtures of deoxyribonucleic acid with hydroxypropylcellulose in concentrated aqueous solutions

In order to obtain information about the compatibility between biopolymeric substances and water-soluble polymers, the phase states of mixtures of DNA with hydroxypropylcellulose (HPC) in concentrated aqueous solutions were studied by simultaneous measurement of differential thermal analysis (DTA) and laser transmittance (He-Ne gas laser; λ 0 = 633 nm), and by means of a polarization microscope and a refractometer. From the results obtained, the phase states in mixture I exhibit an isotropic phase. Mixture II exhibits an anisotropic phase with a slight birefringence from the measurement of the refractive index at 298 K, suggesting that an anisotropic phase in this region corresponds to a quasi-liquid crystal similar to that found previously in the concentration range 3.00–5.00 wt.% of DNA solutions. The phase states in mixture III exhibit birefringence from the measurement of refractive index at 298 K, suggesting that these phase states form stable liquid crystals which are essentially different from an already known liquid crystal of HPC or DNA in concentrated solutions. It is suggested that these liquid crystals are formed by the interaction between DNA and HPC. In order to obtain information about the enthalpy change associated with the liquid crystal formation, the phase states of mixtures I, II and III were also studied using a DTA instrument equipped with a laser, under the same experimental conditions as observed with the polarization microscope. From the thermal and optical properties obtained, the degree of formation α of liquid crystal phases of the mixture formed by the interaction between DNA and HPC is estimated, making use of the degree of precipitation accompanying the phase separation of HPC corresponding to the difference in intensity Δ Iof the transmitted laser light before and after the change in the laser with increasing temperature. From the α value, the net heat of fusion of liquid crystal phases of the mixture formed by the interaction of DNA with HPC is estimated to be about 2.4 kJ per mol of nucleotide.

Structural aspects of silicon diffusion in quaternary III-V thin-film semiconductors

The InGaAlP quaternary system allows the production of semiconductor lasers emitting light in the visible range of the spectrum. Recent advances in the visible semiconductor diode laser art have established the viability of diode structures with emission wavelengths comparable to the He-Ne gas laser. There has been much interest in the growth of wide bandgap quaternary thin films on GaAs, a substrate most commonly used in optoelectronic applications. There is particular interest in compositions which are lattice matched to GaAs, thus avoiding misfit dislocations which can be detrimental to the lifetime of these materials. As observed in Figure 1, the (AlxGa1-x)0.5In0.5P system has a very close lattice match to GaAs and is favored for these applications.In this work, we have studied the effect of silicon diffusion in GaAs/InGaAlP structures. Silicon diffusion in III-V semiconductor alloys has been found to have an disordering effect which is associated with removal of fine structures introduced during growth. Due to the variety of species available for interdiffusion, the disordering effect of silicon can have severe consequences on the lattice match at GaAs/InGaAlP interfaces.

Polarization instability in lasers with weakly anisotropic cavities

A theoretical study is made of the influence of the active medium and the cavity parameters, as well as that of an external magnetic field, on the properties of spontaneous pulsation regimes of lasers with weakly anisotropic cavities. Our results provide a physical interpretation of recently reported experimental data for spontaneous intensity pulsations of orthogonal components of the electromagnetic field generated by a single-mode, Fabry-Perot, HeNe gas laser at λ = 3.3922 μm and by a HeXe laser at λ = 3.51 μm.

Laser Holographic Measurements of Tidal Deformation of A Tunnel

A new technique based on holographic interferometry has been developed for measuring crustal deformations. the holographic recording system, consisting of an He-Ne gas laser and associated optical elements, was first installed in a tunnel at the Amagase Crustal Movement Observatory in 1984. Tunnel deformations caused by tidal and tectonic forces have been precisely determined using the ‘real-time’ technique of holographic interferometry. In this procedure, a hologram of the tunnel wall within a section 1–2 m in diameter is directly recorded on a photographic plate and then the plate is carefully reset in the position at which the hologram was taken. When the reconstructed image of the hologram is superimposed on the current image of the tunnel wall, many interference fringes can be seen through the hologram. the fringe displacement, formed by the deformation of the tunnel, is continuously recorded on a video-cassette tape using a video camera and a time-lapse video recorder. the change in the fringe patterns is analysed using the image-processing system. Tidal deformations obtained from the holographic method are consistent with the strain changes observed with laser extensometers in the same tunnel. These observational results substantiate the tunnel deformation estimated by finite-element calculations.

Long time relaxation effect of liquid castor oil under high pressure conditions

Abstract The relaxation times of Liquid castor oil have been investigated by observing the scattered light of a He-Ne gas laser during the slow or rapid application of pressure up to 0.7 GPa at 293 K. For the application of pressure above 0.36 GPa the strong increase of the scattered light intensity approximately by a factor of 102 has been observed 12 hours after an application of pressure. This pressure effect is also observed for subsequent pressure cycles, i.e., the pressure effect is reversible. Experimental results are interpreted according to a model of a liquid of long rod molecules.

Feature Extraction of 3-D Object by Circular Range Sensing - Circular Range Acquisition and It’s Application to Polyhedra -

A method of feature extraction for 3-D objective surface by circular range acquisition is proposed and investigated. In the experimental system, circular range acquisition is realized by moving an optical range sensor mechanically along a circular path. A prototype of an optical range sensor, which adopting a 2.OmW He-Ne gas laser as a light source, 342(length) × 130(width) × 174mm(height) body size and 5kg weight was manufactured. This range sensor is mounted on the wrist of a SCARA robot (A3020, Hitachi). The range sensor is positioned sequentially at a point along the circular path with a given radius around the axis passing through the target point and detects the range to the corresponded point on the surface of an object. The surface feature around the target point is identified by investigating the variation of the acquired range data along the circular path. Applying the above operation to the surface of an object to be tested, surface features of an object can be extracted. Surface features, such as planes, vertices and edges, are represented as a polar coordinates representation of the range variation along the circular path. Thus, the circular range acquisition and the features extraction of the surface are applied to the different types of vertices on a polyhedra. Moreover, the circular range acquisitions tracing on the edge line are carried out over the surface of an object and experimental results are reported.

Operating conditions and failure mechanisms in He-Ne hollow cathode glow discharge laser cavities

A series of life test measurements has been performed in He-Ne gas laser discharges using several different types of laser discharge cells. These studies have explored the mechanisms that lead to the failure of the discharges in these cells. Specifically, the dependence of the life of the discharge on the operating parameters (discharge current, cell temperature, gas composition and total and partial gas pressures) and on the materials used to construct the cathodes and discharge cells have been studied. The gas removal rates for He and Ne have been found to be very different from each other, and to depend on the operating conditions and cell construction materials. Positive ion-molecule reaction studies have been performed in a separate drift-tube-mass-spectrometer system in which the mechanisms leading to molecular impurity gas clean-up in these He-Ne discharges have been explored.