Use Of Laser Diode Research Articles

Demonstration of Power-over-Fiber with Watts of Output Power Capabilities over Kilometers or at Cryogenic Temperatures

We demonstrate the use of laser diodes and multijunction photovoltaic power converters to efficiently deliver watts of electrical power for long-distance or cryogenic applications. Transmission through single-mode and multi-mode fibers at the wavelengths of 808 nm and 1470/1550 nm are studied. An electrical output power of ~0.1 W is obtained after a 5 km transmission through a standard single-mode SMF28 fiber fed with 0.25 W of optical power. An electrical output power of ~1 W is demonstrated after a 5 km transmission with a standard OM1 multi-mode fiber fed with ~2.5 W. Photovoltaic conversion efficiencies reaching Eff ~49% are obtained with an output voltage of ~5 V using commercial multijunction laser power converters. For low-temperature applications, an ultra-sensitive silicon photomultiplier (SiPM) is used to detect the residual light leaked from fibers as the temperature is decreased. Our study demonstrates that specific fiber types enable low-loss transmission compatible with cryogenic requirements and without light leakage triggering of the SiPM. A cryogenic power-over-fiber system at ~1470 nm is demonstrated with ~2 W of electrical power converted over a 10 m distance having a conversion efficiency of Eff > 65% at 77 K.

Thermal weed control technologies for conservation agriculture—a review

AbstractResearch and development activities on non‐chemical weed control methods to date have mainly focused on mechanical and thermal applications. Selectivity in mechanical weed control is obtained using dynamically actuated harrows. Selectivity in thermal weed control is obtained through a certain heat tolerance of the crop. In conservation agriculture (CA), weed emergence is partially suppressed by constant soil cover with crops or cover crops. Large amounts of plant residues therefore remain on the soil, which make mechanical methods inefficient or difficult to implement. And thermal methods need to prevent not only crop damage but also fire from situationally dry plant residues. In this review, technologies that can potentially be used for in‐crop weed control in CA are discussed. The technologies reviewed include spot‐flaming, electric resistance heating, electromagnetic irradiation and steam/hot water application. Their evaluation focuses on efficiency and specificity (spatial precision). This review indicates that existing equipment does not fulfil the spatial precision required in CA and that further research and development is required on this topic. In particular, the authors suggest further research on the use of laser diodes, micro‐flames and capacitive coupling of electric fields. It seems that the use of automated imaging systems for weed/crop differentiation is a prerequisite in CA to enable automatisation of weed control.

The quality of sperm post-immobilization at some parts of FH sperm using laser diodes

The aim of this study was to find the proper method for sperms immobilization without reducing DNA integrity and damaging the shape of bovine sperms. Sperm immobilization was carried out by double shots using laser Octax MTG with wavelength of 1.48 μm and Eye Ware 3.0 software. A total of 20 sperms were shoot at 4 points, which was the tail end, the mid-tail, the neck and the head of the sperms. The shooting of 1.48 μm laser had the highest effect on immobility reaching 100% on the head and the DNA integrity of the sperms reached up to 90%, the shape of sperms was remained normal (100%) and did not showing significant effect. The results of this study indicated that (1) the laser diode with a wavelength of 1.48 μm at the mid-tail section of the sperm was most effective for sperm immobilization; (2) the use of laser diodes with a wavelength of 1.48 μm can be used to immobilize the sperms before intracytoplasmic sperm injection (ICSI). The diode laser shooting with a wavelength of 1.48 μm at the tail was the most effective in immobilizing the sperms with an immobility of 95.00 %± 5.98 and DNA integrity of 85.00% ± 11.65.

Machine ability on Leather using Co2 Laser and Power Diode Laser

Leather is a versatile, robust and trendy material and therefore its applications are nearly endless. The conventional method of leather cutting takes a lot of man power. Power diode-based Laser technology has grown significantly during recent years due to numerous advantages over conventional cutting methods. The conventional Lasers also have some drawbacks in cutting such as Geometrical inaccuracies, Carbonization, Overcut etc. This can be reduced by the use of Laser diodes. The main purpose of using Laser diode is to reduce power consumption. In the present study, an attempt has been made to develop laser diode-based Laser beam machining (LBM) and CO2 based LBM, to compare the performance measures of Carbonization and Geometrical inaccuracy. The main objective of this work is to enhance the machining process using Laser diode, to make it eco-friendly through the different duty cycles of Pulse Width Modulation (PWM) which can be used to control the intensity of the Laser beam.

Transmission Spectroscopy in Noninvasive Blood Glucose Measurement

The use of laser diodes and photodiodes in transmission spectroscopy has some effects (temperature, time, spectral, and spatial) reducing the accuracy of glucose measurement. These effects can be reduced by using a (1600 ± 3) nm laser in combination with fixation and occlusion of the tissue area under examination. In this work, a method is suggested that allows spatial displacements of the system to be taken into account. A number of methods for reducing the effect of the thermal drift of the diodes are also suggested. A portable noninvasive optical glucose meter implemented using these methods provides high clinical performance: more than 97% of the measurements are in the A and B zones of the Parkes error grid.

Mobile Multi-Gigabit Visible Light Communication System in Realistic Indoor Environment

The main challenges facing high data rate visible light communication (VLC) are the low-modulation bandwidth of the current transmitters (i.e., light emitting diodes), the intersymbol interference (ISI) caused by the multipath propagation and cochannel interference (CCI) due to multiple transmitters. In this paper, for the first time, to the best of our knowledge, we propose, design, and evaluate the use of laser diodes (LDs) for communication as well as illumination. In addition, we propose an imaging receiver for a mobile VLC system to mitigate ISI. A novel delay adaptation technique is proposed to mitigate CCI, maximize the signal to noise ratio, and reduce the impact of multipath dispersion under user mobility. The proposed imaging system is able to provide data rates of 5 Gb/s in the worst-case scenario. The combination of a delay adaptation approach with an imaging receiver (DAT imaging LD-VLC system) adds a degree of freedom to the link design, which results in a VLC system that has the ability to provide higher data rates (i.e., 10 Gb/s) in the considered harsh indoor environment. The proposed technique (delay adaptation) achieves significant improvements in the VLC channel bandwidth (more than 16 GHz) over an imaging system in the worst-case scenario. The VLC channel characteristics and links were evaluated under diverse situations including an empty room and a room with very strong shadowing effects resulting from minicubicle offices.

System efficiency of laser-based white light

Abstract For many lighting applications, light-emitting diodes (LEDs) are replacing traditional light sources providing the possibility for smart and efficient systems as well as a reduction in the product weight. A next step in this development is the integration of laser-based light sources to increase luminance and to further scale down the optics possibly leading to a reduction of necessary resources. This article reviews the possibilities and challenges arising from the use of laser diodes especially compared to current high-power LED systems in terms of efficiency, color-rendering properties, and thermal management.

The temperature effects of diode laser on pulpal tissues for the teeth whitening treatment

Teeth are important organ of human body. Nowadays, people are more interested in dental care, especially, with teeth whitening. The latest development in this treatment is the use of laser diode. The laser process provides many advantages include a shorter treatment time, the reduction of tooth sensitivity and gingival irritation. However, a critical concern still exists, i.e. the destruction of the pulpal tissues due to the heat generated during the treatment. So the purposes of this research then include not only the changing of teeth color but also the temperature changing in pulpal tissues as a function of the power density of the laser diode. In the experiment, human-extracted teeth samples coated by 38 hydrogen peroxide were stimulated with 10.9, 16.1 and 36.7W/cm2 of a 808nm laser diode. The exposure time of 60seconds for a single-exposure and two of 30seconds for double-exposure of were studied. The teeth color before and after the treatment were described by the CIE L*a*b* system. The results showed that the high power density (36.7W/cm2) had given more luminous teeth than the low power density. However, the high power density of the laser also created the high temperature in the pulpal tissue. The power density of 16.1W/cm2 was the highest power allowable before reaching the temperature safety limit for pulpal tissue. In addition, irradiation of laser diode with the double-exposure of 30seconds created more luminous and less heat than that of the single exposure of 60seconds.

High-accuracy small-angle measurement of the positioning error of a rotary table by using multiple-reflection optoelectronic methodology

To improve upon and provide a methodological alternative to published optoelectronic angle measurement systems, the paper performs high-accuracy angle measurement by use of laser diodes, dual-axis position sensing detectors, and a series of reflections between two first-surface mirrors. Measurement accuracy improves from 0.5 to 0.05 arc sec as the light ray is reflected back and forth several times between the mirrors. Analytic ray tracing is used to model the reflected light ray so as to determine the system equations implicitly in terms of the measured angles. The first-order Taylor series expansion provides a linear form of the system equations. To validate the system, a prototype is built. Calibration and stability experiments are performed. Experimental results show the resolution, accuracy, and measurement range are, respectively, 0.008, 0.05, and ±250 arc sec. Compared with traditional optical angle measurement systems, this method has many merits such as low cost, simple configuration, high sensitivity, and high linearity.

Optical Generation of mm-Wave Signal with Wide Linewidth Lasers for Broadband Communications

In future generation space based phased array antennas, pico-cellular broadband communication systems and antenna remoting, optical techniques using optical flber, laser diodes and photo-detectors for transport electrical signals are widely used. Interest in the deployment of optical flbers arises from the low transmission loss compared to electrical media. Aside this, optical flbers are small, ∞exible, lightweight, and they have good phase accuracy and very large bandwidth. In view of the use of laser diodes and photo-detectors in the link, it is expected that the system costs can be considerably reduced if these optical devices are used for the generation of mm-wave signals so that no mm-wave oscillator and modulator are required. The problem is to use large linewidth lasers to generate mm-wave signal with desired spectral purity. This paper suggests a solution. DOI: 10.2529/PIERSxxxxxxxxxxxx

Use of laser diode in joint transform correlator

The use of a laser diode in a joint transform correlator (JTC) is proposed. Effects of temporal coherence, spatial coherence, astigmatism, and elliptical beams are analyzed. Laser diodes can be used in JTC, and also can be used for the correlation process in a Vander Lugt correlator and reading a hologram. Even a light-emitting diode (LED) may be used for the purposes mentioned, if its exit facet is sufficiently small. Two methods for correcting a laser diode beam using a cylindrical lens or a pair of cylindrical lenses are also reviewed. A corrected laser diode can be used in JTC to totally eliminate the effect of astigmatism.

Optical neuron by use of a laser diode with injection seeding and external optical feedback

We present an all-optical neuron by use of a multimode laser diode that is subjected to external optical feedback and light injection. The shape of the threshold function, that is needed for neural operation, is controlled by adjusting the external feedback level for two longitudinal cavity modes of the laser diode individually. One of the two modes corresponds to the output of the neuron, light injection at the wavelength of this mode provides excitatory input. Light injection in the other mode provides inhibitory input. When light corresponding to two input signals is injected in the same mode, summation of input signals can be achieved. A rate-equation model is used to explain the operating principle theoretically. The proposed injection seeding neuron is built using free-space optics to demonstrate the concept experimentally. The results are in good agreement with the predictions from the rate-equation model. Some experimental results show threshold functions that are preferable from a neural-network point of view. These results agree well with injection locking theory and experiments reported in literature.

MECHANICAL ALIGNMENT USING LASER DIODES AND SINGLE ELEMENT PHOTO-DETECTORS; RESOLUTION ENHANCEMENT

This paper studies the use of laser diodes and single element photo-detectors in mechanical alignment. Considering Gaussian beam theoretical model, the effect of laser beam diameter is studied using computer simulation. Optimum conditions that give the highest sensitivity are proved to be where:(i) the laser beam diameter matches the diameter of the sensitive area of the detector.(ii) the laser beam waist is located at the sensitive area of the detector.The photo-detector with two-complement sensitive area has been studied as a better replacement of a single area photodetector. It was proved that the use of this type of detectors , with all of the other parameters unchanged, doubles the alignment sensitivity. Finally, an experimental verification has been performed which gives a good agreement with the results obtained by computer simulation, where an alignment sensitivity of ± 0.3558 ttm was obtained.

A Multichannel Diode Laser Interferometer for Displacement Measurements on a CMM

The increasing demands in the manufacturing measuring technique concerning the accuracy of the production components and the precision of the manufacturing measuring progress make it necessary to find a precise and rapid measuring method that can be integrated into the production machine. The use of laser diodes in the measuring technique has advantages as well as disadvantages. This paper describes the setup, performance and testing of a Fabry Perot Interferometer-stabilized diode laser (FPI) as a light source in an interferometer as well as a transportable lambdameter, and a weather station for calibration of the laser wavelength in air. For length measurements in two axis on a coordinate measuring machine, a two-axis multi function laser interferometer using the FPI-stabilized diode laser was developed and tested under respectively laboratory and workshop conditions.

Generation of short laser pulses

Progress in the technology of ultrashort pulse generation during the last years is outlined. After a short reminder of the basic active/passive mode locking processes and the combined pulse forming action of passive mode locking and gain saturation in the colliding-pulse mode locking arrangement (CPM), the recently developed coupled cavity/additive pulse mode locking (CCM/APM) configurations are reviewed. The Kerr lens mode locking (KLM) process constitutes an important advance towards simplicity and reliability. Its lack of a self-starting property has been of concern, but can finally be overcome by custom-built semiconductor nonlinear absorbers. Reduction of the thermal load of the active materials, higher output efficiencies and much enhanced beam quality result from the use of laser diodes to pump solid state lasers. Synchronisation of the process of picosecond laser pulse generation with an external signal with subpicosecond phase jitter is an important subject. As an illustration the CERN synchro laser system in use at the CLIC test facility for the generation of short electron bunches is presented. Possibilities for future improvements in this system as a consequence of recent technological advances are indicated.

High frequency thermal modulation of superconducting NbTi thin film by use of laser diode

Continuous modulation of the temperature of a fraction of a sputtered NbTi thin film has been performed around its critical temperature at frequencies up to 900 kHz using a pigtailed laser diode to provide the optical power. The high frequency chopping was achieved on a low thermal conductivity substrate. Possible applications of this type of switching in the areas of sensitive electronic and magnetic measurements are discussed.

Use of laser diodes in the circuit of an optical detector of ignition sites

Use of laser diodes in the circuit of an optical detector of ignition sites

Triggering GaAs lock-on switches with laser diode arrays

Progress toward the triggering of high-power photoconductive semiconductor switches (PCSSs) with laser diode arrays, is reported. An 850-W optical pulse from a laser diode array was used to trigger a 1.5-cm-long switch that delivered 8.5 MW to a 38.3- Omega load. Using 166-W arrays, it was possible to trigger a 2.5-mm-long switch delivering 1.2 MW with 600-ps rise-times at pulse repetition frequencies of 1 kHz. These 2.5-mm-long switches survived 10/sup 5/ pulses at 1.0 MW levels. In single-pulse operation, up to 600 A was switched with laser diode arrays. The goal is to switch up to 5 kA in a single-shot mode and up to 100 MW repetitively at up to 10 kHz. At electric fields below 3 kV/cm GaAs switches are activated by creation of one electron-hole pair per photon. This linear mode demands high laser power and, after the light pulse, the carriers recombine in nanoseconds. At higher electric fields GaAs acts as a light-activated Zener diode. The laser light generates carriers as before, but the field induces gain such that the amount of light required to trigger the switch is reduced by a factor of up to 500. The gain continues until the field across the sample drops to a material-dependent lock-on field. The gain in the switch allows for the use of laser diodes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Determination of Rubipium Using Laser Diode Excited Atohic Fluorescence

Abstract The use of laser diodes to excite atomic fluorescence for chemical analysis is investigated. Operating conditions for the laser diode, optical schematic, results, and calibration curve are provided.

Use of laser diodes locked to atomic transitions in multiwavelength coherent communications

The possibility of building multiwavelength coherent communication systems based on low-cost semiconductor lasers in the 0.8µm range locked to rubidium linear absorption is investigated. The values of frequency offset between the resonances of both the D2 (780 nm) and D, (794.7 nm) lines are considered. A simple two-carrier FDM set-up using three resonances of the D2 line is presented and the optical frequency offsets are measured.