Laser Line Generator Research Articles

Signal intensity enhancement of μ-LIF by using ultra-thin laser sheet illumination and aqueous mixture with ethanol/methanol for micro-channel applications

Measurement of concentration distributions of suspended particles in a micro-channel is one of the most crucial necessities in the area of Lab-on-a-chip to be used for various bio-chemical applications. One most feasible way to measure the concentration field in the micro-channel is using μ-LIF (micro-scale laser-induced fluorescence) method. However, an accurate concentration field at a given cross-plane in a micro-channel has not been successfully achieved so far due to various limitations in the light illumination and fluorescence signal detection. The present study demonstrates a novel method to provide an ultra-thin laser sheet beam having 5 μm thickness using a micro-focus laser line generator. The laser sheet beam illuminates an exact plane of concentration measurement field to increase the signal-to-noise ratio and considerably reduce the depth uncertainty. Nile Blue A was used as fluorescent dye for the present LIF measurement. The enhancement of the fluorescent intensity signals was performed by a solvent mixture of water (95%) and ethanol (EtOH)/methanol (MeOH) (5%) mixture. To reduce the rms errors resulting from the CCD electronic noise and other sources, an expansion of grid size was attempted from 1×1 to 3×3 or 5×5 pixel data windows and the pertinent signal-to-noise level has been noticeably increased accordingly.

PH—Postharvest Technology: Automatic Jalapeño Chilli Grading by Width

Jalapeño chilli is a variety grown extensively in Mexico consumed by almost all the population. It has a high processing demand and proper sorting is required before filling or canning. A sorter that classifies chilli by three different width sizes was built. The conveyor used baby suckers to align each chilli during sensing. Chilli width was determined by means of a photodiode scanner, which detected the incoming radiation sent by a laser line generator. Chillies presenting necrosis were detected with a radiometer and removed to increase product quality. The accuracy on the necrosis detection and width classification was of 96·3 and 87%, respectively.

CHD/sub 2/OH optically pumped by a waveguide CO/sub 2/ laser: new far-infrared laser lines from the CD/sub 2/ wagging vibrational mode

For the first time, a wide tunability waveguide CO/sub 2/ laser was used to pump the CHD/sub 2/OH molecule for the generation of new FIR laser lines with a large offset. Optoacoustic signals associated with the infrared absorbing transitions of the CD/sub 2/ wagging vibrational mode served as a guide for finding new laser lines. All lines were characterized in wavelength, relative polarization, intensity, optimum pressure of operation, and precise offset measurements.

OPTICAL SENSOR FOR GRANULAR FERTILIZER FLOW RATE MEASUREMENT

An optical sensor to measure granular fertilizer flow in an airstream was designed, built, and laboratory tested. The sensor components included a laser line generator that transmitted light across a trapezoidal chamber to a 32-element photodiode array. The air-suspended granules would break the light, causing a count to be recorded. The counts were translated into a mass flow rate. Static tests of five materials and six mass flow rates were performed in a replicated block design. Dynamic tests of one material with six step changes in mass flow rate were performed. Results of the static tests showed a strong linear, repeatable relationship between sensor output and mass flow rate. For maximum accuracy, individual calibrations were required for different fertilizer products. Dynamic test results showed that the sensor followed step changes in mass flow rate well, but indicated some limitations in the data analysis algorithm. The optical sensor system showed potential as a first step to a real-time granular fertilizer flow rate sensor.

Standardization of the definition and measurement of the line length and fan angle of laser line generators

Three different commonly used methods of measuring the length and fan angle of a light line or a light fan produced by a laser line generator were analyzed, tested, and compared. One measurement method is proposed as the standard method, and the resultant 1/e(2) intensity fan angle is proposed as the standard parameter to describe the line generator.

Technique for the continuous measurement of projectile velocities in plate impact experiments

This paper describes a simple yet accurate technique for the continuous measurement of projectile velocities in plate impact experiments (the impact velocity is a critical parameter in the interpretation of such experiments). The technique, known as the laser line velocity sensor (LLVS), uses a laser line generator to generate a laser sheet of uniform intensity that is incident on a photodiode at the focus of a collecting lens. The amount of light reaching the photodiode diminishes as the projectile intersects the laser sheet, and so a simple calibration procedure in conjunction with a high-bandwidth optoelectronic system provides a measure of the projectile velocity. Since the measurement is continuous, both the projectile velocity and acceleration can be obtained. The LLVS is very stable, does not need reconstruction after impact, does not need frequent recalibration, and is insensitive to rigid body motions. An example of the application of the technique is provided.

The Tunable, Narrow-Bandwidth Excimer Laser, the New Workhorse for Photochemistry in the UV and VUV

Excimer lasers are powerful sources of radiation in the UV, providing several laser lines between 157 and 353 nm. The excimer laser transition is bound-free, and thus the emitted wavelengths are broad-band (up to 200 cm−1). In addition the high gain (0.15 cm−1) of the laser gas causes a rather large divergence (>1 mrad) in conventional excimer lasers.A new excimer laser concept is described which improves the spectral brightness in terms of watt/(rad × bandwidth) by three orders of magnitude. This allows, through non-linear processes such as Raman shifting the fundamental output and four-wave-mixing in gases, the generation of new laser lines in the UV and VUV.

Continuous 40-W UV laser

A low-pressure Ar arc discharge (length = 1.7 m, diameter = 12 mm) was used for continuous high-power generation of UV laser lines ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda = 351.1</tex> nm, 363.8 nm). Low-loss mirror coatings and stabilization of the discharge with a magnetic field enabled a maximum output power of 40 W to be achieved from the combined lines.

Second-harmonic generation of several argon-ion laser lines

Second-harmonic generation of the 496.5-nm, 501.7-nm, and 514.5-nm lines of the argon laser has been achieved. This was done by 90° phase matching in an ADP crystal at temperatures of -93.2°C, -68.4°C, and -10.2°C, respectively.