He-Ne Gas Laser Research Articles

Some student experiments with a laser

Three simple experiments on the photometric, gaussian and image-forming properties of a He-Ne gas laser are described, with full details of the experimental method and typical calculations.

レーザを用いた噴霧粒子の計測

A basic knowlege for laser speckle photography (LSP) and in-line holographic interferometry is highly essential to obtain two-dimensional velocity distribution of particle jet impinged by the nozzle. LSP can measure the velocity distribution for the entire impinging field. However it is rather difficult to apply this LSP for the high-speed or unsteady flow using CW lasers like Ar-ion or He-Ne gas lasers with the optical chopper due to the intensity of palusive laser light.From this point of view the effort was made to obtain two dimentional velocity field of high-speed particle jet by the giant double pulsed ruby laser in this paper. It is clarified from the results that LSP using double pulsed laser can be masured with high accuracy in the renge of 51-10(m/sec). Parallel with this LSP method, double pulsed holographic interferometry technice is also carried out in order to visualize the two dimensional velocity field of particle, jet. This result agree well with the ones obtained by the LSP method. Through these total considerations, this LSP method is proved to be highly effective for the flow mesurement in a high speed particle jet.

Measurement and visualization of a two-dimensional velocity distribution by laser speckle photography using a He-Ne gas laser. (2nd report. The application to the coaxial cylindrical couette flow and the measuring accuracy of the two-dimensional velocity field).

The laser speckle photography technique has the advantage of obtaining a whole instantaneous two-dimensional velocity distribution as the vector quantity. However, there have been few reports on the measuring accuracy of this technique. Furthermore, most of these reports employed a high-power laser, e.q. an argon laser or a ruby pulse laser, as a light source. In this study, a He-Ne gas laser is employed in order to enhance the validity of the technique. This technique is applied to the coaxial cylindrical Couette flow to discuss the measuring accuracy of the velocity vector, especially the velocity direction. The measuring results agree with the analytical solution within ±10 % at the local scalar quantity of the velocity νθ(γ)=0.01∼0.40 m/s, and within ±2 degrees in the velocity direction.

Simple Laser-Light Modulator with Acrylic Plate Faraday Rotator for Educational Use

He-Ne and other gas lasers, which were once expected to become the major tools of optical communications in the future, now seem to be very far from practical application in communications technology. But the beauty and excellent rectilinear propagation of a gas laser is very moving, and it is still attractive as an educational material in optical communications. The author constructed a simple optical communication system using a He-Ne gas laser for educational use. In this system, a commercially available acryl plate (cut to square bar, 10 × 10 × 20 mm in size) was used as the Faraday rotator to modulate the laser beam, because it is easy to process, highly transparent, lightweight, and easy to obtain.

Measurement and visualization of two-dimensional velocity distribution by the laser speckle photography using a He-Ne gas laser. 1st Report. Application to the free convection field around a vertical plate in air and measuring accuracy.

The speckle photography technique is one of the novelest velocity measurement methods. This study examines the possibility that this technique will become practically applicable. In this study this technique is applied to the laminar-free convection field around an uniformly heated vertical plate in air. Moreover, a He-Ne gas laser is employed as the light source in order to enhance the validity of this technique. The measuring results agree with a similar solution within ±10% at the local velocity u(y)=0.057∼0.185 m/s. It becomes clear that this technique using a He-Ne gas laser can obtain a whole instantaneous two-dimensional velocity distribution with fair accuracy.

低出力レーザーの基礎的研究

Using low-power Ga-Al-As diode and He-Ne gas lasers, cell DNA synthesis of mouse fibroblast cells ( NIH/3T3, MEF/NFS) were examined. As the results, lasers didn't stimulate the cell DNA synthesis.

621 nm CW operation (0%C) of AlGaInP visible semiconductor lasers

Continuous-wave (CW) operation (0°C at 621 nm has been achieved for the first time by an AlGaInP mesa stripe laser, grown by metalorganic vapour-phase epitaxy. The lasing wavelength is shorter than the He-Ne gas laser's wavelength, 633 nm. The CW threshold current is 60 mA (4.8 kA/cm2).

開水路流れにおける縦渦の可視化

An open channel flow is three dimensional because of a coherent motion which is originated in a bursting phenomenon or a depth-scale longitudinal eddy. In this paper the three dimensional turbulent structure of these phenomena were investigated by a flow visualization technique. A tracer method was used to visualize a flow in a cross section, a horizontal section and a vertical section. Neutral tracers were illuminated by a laser light sheet which was obtained from a 5 mW He-Ne gas laser. A video camera and a 35 mm still camera were used in a moving shot or a fixed shot, and many attractive pictures were obtained. To visualize a flow in a cross section, a bore scope shown in Fig. l was used with a image intensifier. Based on these results, the three dimensional turbulent structure of an opn channel flow was illustrated.

9 開水路隅角部における流れの挙動について

Tracer method was used to visualize longitudinal eddies near the edge of a flood plain in an open channel flow. Neutral particle tracers were illuminated by a laser light sheet which was obtained from a 5mW He-Ne gas laser. Set the laser light sheet on a cross section, a vertical section or a horizontal section, pass lines of neutral tracers were observed by a 35 mm still camera or a video camera. Many attractive pictures were taken by a moving camera or a fixed one. Based on these pictures, the three dimensional model of longitudinal eddies near the edge is illustrated.

A simple fibre Fabry-Pérot sensor

A simple fibre Fabry-Pérot sensor is described in which the uncoated cleaved ends of a lenght of single mode fibre are employed as the mirror surfaces to produce high visibility near perfect cosine-squared fringes in the back-reflected light. The experimentally observed signal-to-noise performance of the interferometer illuminated by a HeNe gas laser and a semiconductor diode laser is reported. In an accelerometer configuration the device displayed a below resonance sensitivity of ≥200 rad g -1.

Tracking control system using image sensor for arc welding

A highly accurate and widely applicable tracking control system which guides a welding torch along a joint line is described. The control system includes a servomechanism, a solid-state image sensor, and an image processor. The solid-state image sensor detects the cross-sectional pattern of the welding groove with a He-Ne gas laser. The image processor, consisting mainly of a microcomputer, processes video information and estimates the position of the welding groove center using a statistical technique. This method of tracking control has been employed in the welding apparatus for penstocks with good practical results.

Response Characteristics of the Particle Measuring Systems Active Scattering Aerosol Spectrometer Probe (ASASP–X)

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 measureme...

Fibre-Optic Gyroscope

Comparative study of mechanical, ring-laser and fibre-optic gyroscopes has been made. The single mode fibre-optic gyroscope having a large number of turns of the optical fibre in the spool, replacing He-Ne gas laser by a GaAs laser diode, there by reducing the noise level, and using fully integrated fibre-optics, works out to be the best in the final analysis, for safe navigation and homing of the guided missiles.

Tracking Control System for ARC Welding Using Image Sensor

This paper details a highly accurate and widely applicable tracking control system which guides a welding torch along a joint line. The control system includes a servomechanism, a solid-state image sensor and an image processor. The solid-state image sensor detects the cross sectional pattern of the welding groove with a He-Ne gas laser. The image processor, consisting mainly of a micro-computer, processes video information and estimates the position of the welding groove center on a statistical basis. This method of tracking control has been employed in the welding apparatus for penstocks with advantageous practical results

All-round holograms-A simple procedure

All-round holograms of small objects can be made easily with a minimum of apparatus, no special vibration isolation system and at small unit cost. The procedure described in this note has been found to be very successful and could be repeated by teachers with access to a small He-Ne gas laser. The results dramatically illustrate the full three-dimensional nature of the holographic image.

An investigation of equilibrium and dynamic aspects of starch gelatinisation using a small-angle light-scattering photometer with a solid state photodetector

The equilibrium and dynamic aspects of the gelatinisation of starch granules in a variety of aqueous dispersive media have been investigated by recording the concomitant loss of birefringence of the starch using a small-angle light-scattering photometer. An inexpensive photometer was developed which employed a solid state photodetector and a He-Ne gas laser light source. A directed airflow temperature-control system was also developed to enable both the equilibrium and dynamic aspects of the gelatinisation process to be studied. Equilibrium measurements require long-term temperature stability, whereas dynamic measurements require a rapid increase in the sample temperature without any overshoot. The temperature and time dependences of the gelatinisation process are presented for typical starch dispersions investigated using the integrated, anisotropic light-scattering system.

Information scanning technology: applications of cw AlGaAs injection lasers

The suitability of cw room-temperature injection iasers for information retrieval systems was investigated experimentally. The results indicate that in such applications AlGaAs injection lasers compare favorably with He-Ne gas lasers.

Electron excitation cross section of the He2S1state from diffraction losses in a He-Ne gas laser

Diffraction losses in the optical cavity of a He-Ne gas laser are experimentally studied for the $\mathrm{TE}{\mathrm{M}}_{q00}$, $\mathrm{TE}{\mathrm{M}}_{q10}$, and $\mathrm{TE}{\mathrm{M}}_{q01}$ transverse modes by changing the size of a square aperture placed in front of one of the laser mirrors. By measuring the threshold oscillation current ${I}_{s}$ as a function of the aperture size $2a$, the total losses in the cavity can be determined. These losses are related to the electronic excitation rate of the He $2^{1}S$ metastable state at the threshold of oscillation current and are used to evaluate the inelastic electron excitation cross section of the He $2^{1}S$ state. The experimentally determined cross section is in very close agreement with the published absolute cross-section measurements.

Detection of salts of 2,4-D in aqueous solution by laser raman spectroscopy

Laser Raman spectroscopy is used to detect a salt of a herbicide, 2,4-dichlorophenoxy acetic acid, in water solution at concentrations as low as 500 ppm. The Raman spectrum of the powder is substantially different from the spectrum of the pollutant in aqueous solution. The spectrum of the potassium and sodium salts are the same for the powder or aqueous solution. Five strong bands exist in aqueous solution, and four of these bands are detectable at concentrations as low as 500 ppm. A plausible assignment to group frequencies for some of the Raman bands is given. All spectra were excited with a 50 mW He-Ne gas laser at 6328 Å. Lower concentrations should be detectable with a more powerful laser at a higher frequency because: (1) the intensity of the scattered radiation is proportional to the product of the intensity of the electric field perturbing the molecule and the fourth power of the scattered frequency; (2) the attenuation coefficient of water is less; (3) the photocathode used is more efficient at higher frequencies and (4) the monochromator grating used is blazed at 5000 Å. The resonance Raman effect is discussed as a possible method for the detection and identification of small optimal concentrations of pollutant in water.

Stabilized and Calibrated Michelson Interferometer

The integral value of the refractive index of a plasma in a toroidal device is measured by a stabilized Michelson interferometer with a HeNe gas laser (λ = 0.63 μ) as light source. A calibrated phase modulator enhances the accuracy with which small phase shifts are measured, and automatically indicates phase shifts exceeding π/2.