Laser Diode Parameters Research Articles

A Variable Carrier Generation for Heterodyne LDV with an Optical Phase-locked Loop

A heterodyne laser Doppler vibrometer (LDV) requires a frequency shifter to generate a carrier for the vibration information in the detector signal. The carrier frequency should be carefully selected in order to obtain the intended measurement range with a demodulation bandwidth that avoids existing noise sources. The traditional frequency shift in heterodyne LDV is realized with an acoustooptical modulator, which can only generate a fixed carrier frequency. In this paper, a variable carrier generation method based on an optical phase locked loop (OPLL) is demonstrated. Our setup implements a feedback loop to control the phase of the second laser to synchronize a reference laser. In lock-in status the carrier for the vibration information associated with a local oscillator signal. In this paper, we obtain the laser diode parameters relevant to performance and on the design of the photodetector and loop filter. Finally, the performance of the lock-in OPLL, variable carrier as well as velocity measurement is reported and the reliability of the proposed method is evaluated.

Er,Cr:YSGG and 980nm diode lasers influence dentin surface volume after cariogenic challenge: in vitro study.

This study aimed to evaluate the influence of the Er,Cr:YSGG irradiation and 980-nm diode lasers on the surface roughness (SR) and volume loss (VL) of dentin subjected to cariogenic challenge. Subsequently, 130 specimens of bovine dentin were divided into the following 13 groups: NT: no treatment; FG: fluoride gel; FV: fluoride varnish; Di: 980-nm diode; Di + FG; Di + FV; FG + D; FV + Di; Er: Er,Cr:YSGG; Er + FG; Er + FV; FG + Er and FV + Er. Er,Cr:YSGG laser parameters were as follows: 0.25 W; 5.0 Hz; 4.46 J/cm2 without water and 55% air. Furthermore, the 980-nm diode laser parameters were 2.0 W; 2.0 Hz; 21.41 J/cm2. The samples from each group were subjected to pH cycling. A confocal laser scanning microscope was used to evaluate SR and VL. Difference between the volume of the reference and treated areas + DES/RE was used to determine SR and VL. The mean values of the different groups were subjected to analysis of variance and Tukey's post-hoc test. The VL values were analyzed using the Kruskal-Wallis and Dunn post-hoc test (p < 0.05). The SR of the reference area did not show a statistically significant 1807-3107-bor-38-e025treatment and cariogenic challenge (p > 0.05). Moreover, VL in the FV + Di and FV + Er groups showed a statistically significant difference compared with areas submitted to different types of treatment and cariogenic challenge (p > 0.05). Er,Cr:YSGG and 980-nm diode lasers associated with fluoride varnishes decreased dentin VL in bovine teeth submitted to cariogenic challenge.

Preparation of blue-light diode lasers for pumping applications: cooling system, characterization, and beam shaping

ABSTRACT This study seeks to characterize and modify some of the major parameters of blue-light diode lasers and indicate the significance of developing this field of technology. Our diode begins to work at the threshold current of 650 mA with the output wavelength of 463 nm. By designing an efficient cooling system, a current of 5.8 (even further) Amperes can pass safely through the diode at a voltage of 6.3 V., to produce a stable 3.5 Watts output power. With an optical arrangement for the shaping of the beam emitted from the diode, the M2 factor is decreased from the value of 11.27 × 2.34 before the beam shaping to the value of 1.38 × 1.59 after the beam shaping with the beam spot size of 240.30 × 232.45 μm2. The major parameters such as laser stability in time, voltage–current-power diagram, slope efficiency, external quantum efficiency, power conversion efficiency, and the polarization degree were also measured.

Influence of ion cleaning of front facet of 9xx nm InGaAs/AlGaAs/GaAs diode lasers on their maximal output power

This paper reports on the study of the effect of ion cleaning of emitting cleaved facet of 9xx nm laser diodes based on InGaAs/AlGaAs/GaAs on their limiting radiation power. Measured maximal power and the percentage of laser diodes with a visual manifestation of catastrophic optical damage in the active region were analyzed. It was found that short-term (1 min) low-energy treatment with argon and hydrogen ions does not lead to changes in the parameters of laser diodes, while treatment with nitrogen ions results in a decrease in the maximal output power and an increase in the probability of catastrophic optical damage. It is also shown that the use of an ion source based on electron cyclotron resonance leads to better results compared to a End Hall source or radiofrequency source with inductively coupled plasma, due to the lower energy of the ions. Keywords: Ion cleaning, laser diode, catastrophic optical damage, maximal output power, passivation, nitridization.

Влияние ионной очистки поверхности излучающего скола 9хх нм лазерных диодов на основе InGaAs/AlGaAs/GaAs на их предельную мощность излучения

This paper reports on the study of the effect of ion cleaning of emitting cleaved facet of 9xx nm laser diodes based on InGaAs/AlGaAs/GaAs on their limiting radiation power. Measured maximal power and the percentage of laser diodes with a visual manifestation of catastrophic optical damage in the active region were analyzed. It was found that short-term (1 min) low-energy treatment with argon and hydrogen ions does not lead to changes in the parameters of laser diodes, while treatment with nitrogen ions results in a decrease in the maximal output power and an increase in the probability of catastrophic optical damage. It is also shown that the use of an ion source based on electron cyclotron resonance leads to better results compared to a End Hall source or radiofrequency source with inductively coupled plasma, due to the lower energy of the ions.

Review of laser‐diode pumped Ti:sapphire laser

AbstractTi:sapphire laser has an important position in ultrashort pulse generation and wavelength tuning. The use of expensive frequency‐doubled diode‐pumped solid‐state laser as the pump source limits the promotion of its application to a certain extent. With the maturity of high‐power blue‐green laser diodes (LDs), low‐cost LD directly pumped Ti:sapphire laser becomes possible. After more than 10 years of development, the output parameters of LD pumped Ti:sapphire lasers have been greatly improved. Moreover, the lasers have been applied to optical frequency combs, multiphoton microscopy imaging, and so forth, both of which have achieved impressive results.

Microresonator and Laser Parameter Definition via Self-Injection Locking

Self-injection locking to a high-quality-factor microresonator is a key component of various up-to-date photonic applications, including compact narrow-linewidth lasers and microcomb sources. For optimal construction of such devices it is necessary to know the parameters of the locking mode, which is a challenging task. We developed and verified experimentally an original technique based on the fundamentals of the self-injection locking effect, which allows determining the key parameters of the mode of the microresonator (quality factor, vertical index) as well as laser diode parameters. We demonstrated that this method can be used in the spectral ranges where conventional methods are not applicable, for example, in the mid-IR. We stabilized a 2.64 $\mu$m laser diode by a high-Q whispering gallery mode microresonator made of crystalline silicon. Using the elaborated technique, the quality factor of the microresonator was determined to be $5\cdot10^8$.

Photobiomodulation enhances the Th1 immune response of human monocytes

This study aims to evaluate the effects of photobiomodulation (PBM) on human monocytes, assessing the oxidative burst and ultimate fungicidal potential of these cells, as well as the gene expression at the mRNA level of CD68, CD80, CD163, CD204, IL-6, TNF-α and IL-10 in derived macrophages. Primary cultures of human monocytes were irradiated with an InGaAlP (660nm)/GaAlAs (780nm) diode laser (parameters: 40mW, 0.04cm2, 1W/cm2; doses: 200, 400 and 600J/cm2). Cells were submitted to the chemiluminescence assay, and a microbicidal activity assay against Candida albicans was performed. Reactive oxygen species (ROS) and nitric oxide (NO) production were measured, and cell viability was assessed by the exclusion method using 0.2% Trypan blue reagent. Irradiated monocytes were cultured for 72h towards differentiation into macrophages. Total RNA was extracted, submitted to reverse transcription and real-time PCR. The results were analysed by ANOVA and the Tukey test (α = 0.05). Irradiated monocytes revealed a significant increase in their intracellular and extracellular ROS (P < 0.001). The 660nm wavelength and 400J/cm2 dose were the most relevant parameters (P < 0.001). The fungicidal capacity of the monocytes was shown to be greatly increased after PBM (P < 0.001). PBM increased the expression of TNF-α (P = 0.0302) and the production of NO (P < 0.05) and did not impair monocyte viability. PBM induces a pro-inflammatory Th1-driven response in monocytes and macrophages.

Numerical investigation of longitudinal spatial hole burning (LSHB) in high-power semiconductor lasers

Longitudinal spatial hole burning (LSHB) and its effect on output power of broad-area semiconductor lasers are examined using one-dimensional rate equations. It is shown that direct LSHB can be separated into two mechanisms – an increase in the effective threshold current and a decrease in the output efficiency. The LSHB dependence on laser diode parameters is analysed. In particular, a large optical confinement factor Γ is shown to suppress the LSHB-induced power decrease.

Evaluation method for the optical feedback factor and linewidth enhancement factor using phase discontinuities in self-mixing interferometry signals.

Self-mixing interferometry (SMI) is a reliable method that has been applied to measuring displacements, absolute distances, and velocities of remote targets. Evaluating the optical feedback factor C and the linewidth enhancement factor α is a vital step in calculating laser diode parameters and in processing SMI signals using phase unwrapping. This paper proposes an evaluation method for the optical feedback factor and the linewidth enhancement factor of arbitrary waveforms by investigating the slopes of phase discontinuity distribution in the optical feedback regime of 1<C. First of all, the effects that the slope of phase discontinuity distribution has on the prediction of the optical feedback factor and the linewidth enhancement factor are clarified. Next, an algorithm is proposed to evaluate the optical feedback factor and the linewidth enhancement factor using the slope variation of phase discontinuity distribution, along with a method to select discontinuities in order to improve measurement accuracy using the cumulative effect of discontinuity distribution. The proposed method is verified through simulations as well as experiments with a low-cost semiconductor laser.

Optical chimera in light polarization

Light polarization is an inherent property of the coherent laser output that finds applications, for example, in vision, imaging, spectroscopy, cosmology, and communications. We report here on light polarization dynamics that repeatedly switches between a stationary state of polarization and an irregularly pulsating polarization. The reported dynamics is found to result from the onset of chimeras. Chimeras in nonlinear science refer to the counterintuitive coexistence of coherent and incoherent dynamics in an initially homogeneous network of coupled nonlinear oscillators. The existence of chimera states has been evidenced only recently in carefully designed experiments using either mechanical, optomechanical, electrical, or optical oscillators. Interestingly, the chimeras reported here originate from the inherent coherent properties of a commercial laser diode. The spatial and temporal properties of the chimeras found in light polarization are controlled by the laser diode and feedback parameters, leading, e.g., to multistability between chimeras with multiple heads and to turbulent chimeras.

CD31 expression in human primary teeth treated with photobiomodulation therapy

This study aimed to evaluate the effects of photobiomodulation (PBM) on CD31 expression in pulp tissue repair of human primary teeth. Fifteen mandibular primary molars were divided into the following groups: GI—calcium hydroxide (CH), GII—PBM + CH, and GIII—PBM + zinc oxide/eugenol (ZOE). In the GII and GII groups, an indium–gallium–aluminum phosphide (InGaAlP) diode laser was used for the irradiation through 320-μm diameter optical fiber in contact with pulp tissue. The red laser diode parameters were set at 660-nm wavelength, 10-mW power output, 2.5-J/cm2 energy density, 50–60-Hz frequency, output beam area of 0.04 cm2, and irradiation time of 10 s in continuous mode. After pulpotomy treatment, clinical and radiographic follow-ups were accomplished until the teeth achieved regular exfoliation period. Teeth were extracted for histological analysis and immunolocalization of CD31. Histopathological statistical analyses were performed by Kruskal-Wallis followed by Dunn test to determine statistically significant differences (p < 0.05). Although GII showed no inflammation or discreet inflammatory cells, the comparison among the groups using a score system revealed no statistically significant differences regarding inflammation and the amount of blood vessels. The immunohistochemistry analysis revealed positive CD31 expression in the blood vessels of all the studied groups. Immunostaining was observed in large blood vessels associated with inflammatory cells on GI and GIII, whereas GII showed discreet immunostaining predominantly in small blood vessels scattered throughout the pulp tissue with none or rare inflammatory cells. The CD31 expression was greater in the group PBM when associated with calcium hydroxide. Photobiomodulation therapy followed by calcium hydroxide helped in repairing and seemed to regulate angiogenesis and leukocyte migration processes in the remaining pulp tissue after primary teeth pulpotomy.

Temperature elevation investigations on the external root surface during irradiation with 940 nm diode laser in root canal treatment

Background: The root canal system is complex. Eliminating the microorganisms from it is not easy. Diode laser is proposed as one of the effective methods to sterilize the canal. Aims: The aim of this work was to evaluate the diode laser parameters to be used as an adjunct for root canal sterilization to avoid any increase in temperature to prevent any thermal collateral damage to the periodontal tissue. Materials and Methods: A total of 24 single-canal premolars were used; they were divided randomly into two groups (n = 12). Group 1 was irradiated with 1.5 W continuous wave mode of diode laser and Group 2 with 2.5 W/2 5 Hz pulsed mode of the diode laser. The temperature was measured using thermometer and thermal camera at the apical part of the root. Post hoc test, Student's t-test, and paired t-test were used in the study. Results: The results showed a modest increase in temperature at the external root surface for Group 1, with maximum increase of 6.7°C in apical portion, and 8.5°C for Group 2. Conclusions: Within the present parameters, the laser is safe for use as an adjunct for root canal sterilization.

Electrical Derivative Measurement of High‐Power InGaAs LDs Under Scanning Current with Variable Step

For the large driving current of high-power semiconductor Laser diodes (LDs), a modified method to measure the electrical derivative of LDs under scanning driving current with variable step length is proposed, which is to achieve the fast and accurate measurement of optical and electrical characteristic parameters of LDs with a relatively small data acquisition. The experimental results show that, with fewer measurements, this method can effectively and accurately measure and extract the LDs corresponding parameters including threshold current (Ith ), voltage-current characteristic (V-I ), luminous power-current relation (P-I ), electrical derivative curve (IdV/dI-I ). The wavelet transformation singularity testing results of the threshold current also verify the accuracy, reliability, and advantage of this method.

Diode Laser for Laryngeal Surgery: a Systematic Review.

Introduction The diode laser has been frequently used in the management of laryngeal disorders. The portability and functional diversity of this tool make it a reasonable alternative to conventional lasers. However, whether diode laser has been applied in transoral laser microsurgery, the ideal parameters, outcomes, and adverse effects remain unclear. Objective The main objective of this systematic review is to provide a reliable evaluation of the use of diode laser in laryngeal diseases, trying to clarify its ideal parameters in the larynx, as well as its outcomes and complications. Data Synthesis We included eleven studies in the final analysis. From the included articles, we collected data on patient and lesion characteristics, treatment (diode laser's parameters used in surgery), and outcomes related to the laser surgery performed. Only two studies were prospective and there were no randomized controlled trials. Most of the evidence suggests that the diode laser can be a useful tool for treatment of different pathologies in the larynx. In this sense, the parameters must be set depending on the goal (vaporization, section, or coagulation) and the clinical problem. Conclusion: The literature lacks studies on the ideal parameters of the diode laser in laryngeal surgery. The available data indicate that diode laser is a useful tool that should be considered in laryngeal surgeries. Thus, large, well-designed studies correlated with diode compared with other lasers are needed to better estimate its effects.

980-nm, 15-W cw laser diodes on F-mount-type heat sinks

We have studied the key optical emission parameters of laser diodes (emission wavelength, ; stripe contact width, ) mounted directly on F- and C-mount-type copper heat sinks, without intermediate elements (submounts). When effectively cooled by a thermoelectric microcooler, the lasers on the F-mount operated stably at output powers up to . The lasers were tested for reliable operation at an output power of for , and no decrease in output power was detected to within measurement accuracy. The experimentally determined maximum total efficiency is 71.7 % and the efficiency at a nominal output power of is 61 %. We compare parameters of the laser diodes mounted on C- and F-mounts and discuss the advantages of the F-mounts.

Study of somesthesis according to change in pulse diode laser parameters.

Laser can precisely deliver quantitative energy to a desired region in a non-contact way. Since it can stimulate regions and minutely control parameters such as the intensity, duration and frequency of stimulus, laser is often used for the areas such as low power laser treatment and clinical physiology. This study proposes simulation using pulse diode laser with reliable output and identifies laser parameters that can present a variety of somesthesis. It is found that typically, as frequency and energy increase, the ratio of feeling senses increases, and dominant sense moves from the sense of heat through tactile sense to pain. This study will be baseline data for studies of the sense of heat, tactile sense and pain, contribute to studying neurophysiology sector and be applied to basic clinical research.

Thermal modelling of high-power laser diodes mounted using various types of submounts

Using three-dimensional thermal modelling of a high-power laser diode with a stripe contact width of as an example, we analyse the thermal parameters of high-power laser diodes mounted using submounts. We consider a range of thermal conductivities of submounts that includes parameters of widely used thermal compensators based on AlN, BeO and SiC, as well as on CuW and CuMo composites and polycrystalline and single-crystal synthetic diamond with high thermal conductivity. Taking into account experimental overall efficiency vs. pump current data, we calculate the temperature of the active layer as a function of the width, thickness and thermal conductivity of the submount at thermal loads corresponding to cw output powers of 10, 15 and .

Sympathetic ophthalmia following diode laser cyclophotocoagulation

BackgroundSympathetic ophthalmia is a rare form of bilateral uveitis that develops following an ocular penetrating injury to one eye. Several cases of sympathetic ophthalmia have been reported after non-penetrating cyclodestructive...

Emission parameters and thermal management of single high-power laser diodes

We report emission parameters of high-power cw laser diodes (LDs) with a stripe contact width of . On copper heat sinks of the C-mount type, a reliable output power of is obtained at a pump current of . Using a heat flow model derived from analysis of calculated and measured overall efficiencies at pump currents up to , we examine the possibility of raising the reliable power limit of a modified high-power LD mounted on heat sinks of the F-mount type using submounts with optimised geometric parameters and high thermal conductivity. The possibility of increasing the maximum reliable cw output power to with the use of similar laser crystals is discussed.