Diode Laser System Research Articles

Simple high-precision diode laser system with digital control.

A simple wavelength tunable diode laser system has been designed and fabricated for laboratory use. Both the current and temperature controllers are based on an AVR microcontroller, and the experimental controls have been implemented with the help of daemon programs running in a message passing interface environment, which allows the users to run the control server and client programs on separate computers. The stability of the controllers has been tested using a distributed feedback (DFB) diode laser with a central wavelength of 852.3nm. A noise spectral analysis of the current controller with and without the use of the diode laser as the active load has been demonstrated. The absorption spectra of 6S 1/2→6P 3/2 transition of 133 C s, as recorded by using the DFB laser system developed, are also presented.

Efficacy of Dental Bleaching with Diode Laser, Led Irradiation and Chemical Activation System: a Comparative Study

Aim: To compare the effectiveness and safety of various methods of professional teeth bleaching using light and chemical activation systems in an in vivo study. Materials and Methods: Teeth whitening was performed on 48 patients aged 20 to 35, divided into 4 groups. In patients of group 1 for dental bleaching a diode laser activation was used, group 2 – LED/gel activation, group 3 – chemical whitening with the following remineralization therapy, group 4 – chemical whitening without remineralization therapy. The study of the effect of bleaching systems on the hard tooth tissues was carried out by index assessment, determination of biochemical parameters of an oral fluid. Results: Laser bleaching of the vital teeth was significantly more effective than the other methods with 95% confidence level and did not affect the structure of hard dental tissues and mineral exchange of the oral fluid. LED irradiation has a high whitening effect, but leads to dentin hypersensitivity and a decrease in phosphorus and alkaline phosphatase of oral fluid. Chemical bleaching causes a decrease in enamel resistance, the occurrence of tooth sensitivity, violation of mineral exchange of oral fluid, therefore; it requires combined use with local remotherapy. Conclusions: Laser teeth bleaching is the effective and safe method in management of discolored teeth. A positive result of its use can be considered an improvement of color change of the teeth by 3.33 shades compared to chemical bleaching, enamel stability, low values of dental hypersensitivity indices, no changes in biochemical parameters of the oral fluid.

Microcontroller-Based Thermoelectrically Stabilized Laser Diode System

This work aims to describe the development of a prototype laser diode system along with its driver circuit and a stable microcontroller-based thermo-electric cooling system. The laser diode driver circuit was designed and simulated by using NI Multisim. The driver circuit was built using two LM317 ICs to control the voltage across the laser diode and current through the laser diode. The laser diode output power varies by varying the current across the laser diode through the driver circuit. The temperature of the laser diode rises with time, affecting the output power of the laser diode during a long period of operation. A microcontroller-based cooling system was designed and fabricated using thermoelectric coolers. The microcontroller controls the cooling system ON/OFF period to maintain the laser diode at a particular temperature by removing the excess heat produced during the lasing action. The laser diode with a microcontroller-based cooling system shows that the laser diode output power remains stable during a long period of operation.

Watt-level beam combined diode laser systems in a chip-scale hybrid photonic platform.

Scaling up the power of on-chip diode lasers is of great importance for many emerging applications, such as integrated nonlinear optics, remote sensing, free space communication, infrared countermeasure, and light detection and ranging (LIDAR). In this manuscript, we introduce and demonstrate photonic integrated circuits (PIC) based beam combining methods to create power scalable, integrated direct diode laser systems. Traditional laser beam combining, including coherent beam combining (CBC) and wavelength beam combining (WBC), usually requires free space or fiber optical components, leading to bulky and complex systems. Instead, PIC based beam combining methods can greatly reduce the cost, size, weight, and power consumption (CSWaP) of next generation direct diode laser systems. We experimentally demonstrate four channel chip-scale CBC and WBC with watt-level on-chip power by using III/V-Si3N4 hybrid integration. Our results show that PIC based beam combining is very suitable for power scaling in a chip-scale platform.

Wideband current modulation of diode lasers for frequency stabilization.

We present a current modulation technique for diode laser systems, which is specifically designed for high-bandwidth laser frequency stabilization and wideband frequency modulation with a flat transfer function. It consists of a dedicated current source and an impedance matching circuit both placed close to the laser diode. The transfer behavior of the system is analyzed under realistic conditions employing an external cavity diode laser (ECDL) system. We achieve a phase lag smaller than 90° up to 25 MHz and a gain flatness of ±3 dB in the frequency range of DC to 100 MHz, while the passive stability of the laser system is not impaired. The potential of the current modulation scheme is demonstrated in an optical phase-locked loop between two ECDL systems with a phase noise of 42 mradrms. The design files are available as an open-source project.

Deep-Learning-Based Algorithm for the Removal of Electromagnetic Interference Noise in Photoacoustic Endoscopic Image Processing.

Despite all the expectations for photoacoustic endoscopy (PAE), there are still several technical issues that must be resolved before the technique can be successfully translated into clinics. Among these, electromagnetic interference (EMI) noise, in addition to the limited signal-to-noise ratio (SNR), have hindered the rapid development of related technologies. Unlike endoscopic ultrasound, in which the SNR can be increased by simply applying a higher pulsing voltage, there is a fundamental limitation in leveraging the SNR of PAE signals because they are mostly determined by the optical pulse energy applied, which must be within the safety limits. Moreover, a typical PAE hardware situation requires a wide separation between the ultrasonic sensor and the amplifier, meaning that it is not easy to build an ideal PAE system that would be unaffected by EMI noise. With the intention of expediting the progress of related research, in this study, we investigated the feasibility of deep-learning-based EMI noise removal involved in PAE image processing. In particular, we selected four fully convolutional neural network architectures, U-Net, Segnet, FCN-16s, and FCN-8s, and observed that a modified U-Net architecture outperformed the other architectures in the EMI noise removal. Classical filter methods were also compared to confirm the superiority of the deep-learning-based approach. Still, it was by the U-Net architecture that we were able to successfully produce a denoised 3D vasculature map that could even depict the mesh-like capillary networks distributed in the wall of a rat colorectum. As the development of a low-cost laser diode or LED-based photoacoustic tomography (PAT) system is now emerging as one of the important topics in PAT, we expect that the presented AI strategy for the removal of EMI noise could be broadly applicable to many areas of PAT, in which the ability to apply a hardware-based prevention method is limited and thus EMI noise appears more prominently due to poor SNR.

Comparative study between great saphenous vein endovenous laser ablation (EVLA) and modified haemodynamic correction (CHIVA) as a treatment for varicose veins

Varicose veins (VV) could be a handicapping condition which may lead to limb swelling, pain and venous stasis ulcer. Prevalence of VV could present from 1% to 73% and from 2% to 56% at women and men respectively. CHIVA has been developed through the last two decades and is currently the second most common surgical procedure for the operative management of VV. Endovenous laser treatment of GSV was approved by FDA in 2002 and SSV was approved in 2003. EVLT allows delivery of Laser energy directly into the blood vessel lumen. EVLT with a 1470-nm diode Laser system is clinically safe, feasible and well-tolerated technique without scar and allows people to return to their normal daily activities rapidly. In a prospective comparative study between January 2018 and January 2020, 40 patients from those attended the outpatient departments complaining from VV were assessed according to the CEAP classification and ultrasonic duplex and arranged into group I (CHIVA) and group II (EVLA). Both CHIVA operation and EVLA were performed under local anesthesia. Cases were reviewed regularly at the outpatient clinic for 6 months for recurrence and complications. The recurrence occurred at 2/20 and 0/20 at CHIVA and EVLA respectively.

Clinical experience of transbronchoscopic laser ablation for central airway stenosis using a high-power diode laser-ten years' experience at a single institute.

High-power diode (GaAlAs) laser systems have been used for transbronchoscopic laser ablation for central airway stenosis. Such diode laser systems show a similar clinical effect to a conventional Nd-YAG laser, but the instrument is more compact with easier handling. We use a high-power diode laser system with a non-contact probe for endobronchial ablative therapy. The present study reviewed our experience with transbronchoscopic laser ablation to explore a better clinical approach for managing central airway lesions. We retrospectively reviewed the patients who were treated for central airway lesions by transbronchial laser ablation using the non-contact-type probe from January 2005 to December 2015 at Chiba University Hospital. We investigated the cause of stenosis, number of treatments, laser setting, total amount of energy, complications, and simultaneously performed modality. Thirty-three patients underwent treatment a total of 72 times. There were 23 males, with an average age of 60.3 years old (range, 18-80 years old). The primary causes of the central airway stenosis were neoplastic disease in 22 (16 malignant tumors, 6 benign tumors) and non-neoplastic disease in 11. Among malignant tumors, there were eight tracheal cancer and five lung cancer patients as well as three patients with esophageal cancer. Among benign tumors, there were three hamartomas and one patient each with papilloma, smooth muscle tumor, and glomus tumor. The non-neoplastic causes of airway stenosis were intubation or tracheotomy in four patients, tuberculosis and granulation in two each, and trauma, burn, and surgery in one each. The numbers of treatments were 30 times (1.36 times/patient) for neoplastic diseases and 42 times (3.82 times/patient) for non-neoplastic disease. The total amount of energy was 1,936 J on average (1,674 J for neoplastic diseases and 2,098 J for non-neoplastic disease). There were no major complications related to transbronchial laser ablation therapy. Transbronchoscopic laser ablation using a diode laser system with a non-contact probe can be safely performed and is useful for endobronchial treatment of both neoplastic and non-neoplastic central airway lesions.

High-power external cavity diode laser with narrow linewidth emission and adjustable polarization state at 445 nm

A high-power external cavity diode laser (ECDL) system at 445 nm is proposed that has narrow-band linewidth emission and adjustable polarization state and can be used for nonlinear frequency conversion in deep ultraviolet spectrum. By introducing a half-wave plate to control the polarization state of the laser source, the first-order diffraction (R1st) efficiency is changed. The relationship between the linewidth and the first-order diffraction efficiency is discussed through simulation and experiment. In addition, the tunable ranges of the ECDL are measured. Finally, a continuous-wave output with the spectral width of 72 pm at 445 nm and a maximum optical output power of 1.52 W can be obtained when R1st is 25%, of which the tunable range has a minimum of 2.3 nm.

Micro-integrated high-power narrow-linewidth external-cavity tapered diode laser at 762 nm for daylight imaging

Solar radiation is a challenge for laser-based daylight imaging since it decreases the signal-to-noise ratio (SNR) of the imaging. Here we demonstrate a micro-integrated external-cavity tapered diode laser system for daylight imaging. It emits light at a wavelength of 762 nm, chosen because of its overlap with an oxygen absorption band in the solar radiation spectrum. The integrated laser system consists of a tapered diode amplifier as gain medium and an external volume Bragg grating for spectrum stabilization and narrowing, thus a narrow bandpass optical filter can be used to improve the SNR further. The laser system can be operated in both continuous wave (CW) mode and pulsed mode by modulating the injected current to the amplifier. In CW mode operation, 1.3 W of output power is obtained with an emission spectral linewidth of 4 pm, and a beam propagation factor in the slow axis, M2, of 1.7 (4σ). In pulsed mode operation with a trigger signal of a 50μs pulse width and a 10 kHz repetition rate, 2.0 W of peak output power is achieved with an emission spectral bandwidth of 0.2 nm, and an M2 in the slow axis of 1.9 (4σ). The modulation depth is almost 100%.

Influence of helium metastable states on the E-H mode transition in an inductively coupled plasma

A helium (He) inductively coupled plasma (ICP) source combined with two diode laser systems with the wavelengths of 396.5 nm (21S–41P) and 1082.9 nm (23S–23P) was configured to investigate the influence of He metastable states on the E-H mode transition. The population densities of 21S and 23S states were measured by laser absorption spectroscopy as the functions of RF power, He pressure, and the distance from RF antenna. Correlations between the E-H mode transition and the population density ratio of the 23S metastable state to the 21S metastable state as well as the line intensity ratio (LIR) of the 33D-23S transition to the 31P–21S transition were investigated. The E-H mode transition of He ICP was analyzed by the electron impact ionization rate and it was confirmed that the 23S metastable state plays a key role in the E-H mode transition.

Antimicrobial efficacy of photosensitized nanoparticles, diode laser, conventional, and sonic irrigation systems against enterococcus faecalis in root canals – An in vitro study

Aim: This study aims to evaluate and compare the antimicrobial effect of Photosensitized Nanoparticles, Diode Laser (DL), and Conventional and Sonic Irrigation Systems against Enterococcus faecalis in root canals – An in vitro Study.Materials and Methods: The root canals of 104 extracted human single-rooted teeth were prepared, and E. faecalis was incubated in the root canals for 1 week. The teeth were randomly divided into four experimental groups and one control group (n = 20): No treatment was done, sodium hypochloride (NaOCl) group (n = 20): Canals irrigated with5 ml of 2.5% NaOCl for 60 s, NaOCl and Endoactivator group (n = 20): Canals irrigated with 5 ml of 2.5% NaOCl for 60 s followed by activation of NaOCl with Endoactivator for 30 s, NaOCl and 910 nm DL group (n = 20): (1 W 5 times for 5 s) canals irrigation with5 ml of 2.5% NaOCl for 60 s followed by Photodynamic Therapy (PDT) with 910 nm DL, silver nanoparticles (AgNPs)/Indocyanine green (ICG)/DL group (n = 20): DL modified PDT with 5 min of irrigation with 5 mL AgNPs (100 ppm)/ICG/910 nm DL (200 mW, 30 s). A reduction in colony count was assessed by counting colony-forming units by Digital Colony Counter.Results: Significant reductions were noted in E. faecalis colony counts in all groups (P < 0.05). The greatest reduction in colony count (99.93%) was noted in the NaOCl and DL group followed by NaOCl and Endoactivator group; however, the differences in this respect between the AN/ICG/DL group and NaOCl group were not significant (P > 0.05).Conclusions: NaOCl and 910 nm DL were more successful in reducing the number of E. faecalis colony counts followed by NaOCl and Endoactivator group but it can also be concluded that PDT with ICG, an 910 nm DL, and AgNPs has the potential to be used as an adjunct for disinfection of the root canal system.

A clinical trial comparing BiVap (Richard Wolf®) saline vaporization of the prostate vs. TwisterTM Diode Laser System in the treatment of benign prostatic obstruction between prostate volume 90 to 150 ml.

To evaluate the efficacy, safety and postoperative outcomes of the BiVap and Twister systems with benign prostatic obstruction (BPO) in prostate volüm between 90-150 ml. In total, we included 131 patients treated with BiVap system (n = 68) and Twister system (n = 63). Postoperative complications including urinary tract infection, transient hematuria, severe dysuria and fever >38° C, urinary incontinence and urethral stricture were also noted. All patients were evaluated at the postoperative 1st, 3rd, 6th and 12th month and preoperative and postoperative values of IPSS score, QoL score, total PSA, IIEF 15, PVR, Qmax and Qave were compared. Preoperative demographic characteristics were similar in the 2 groups. There was observed significant improvement for IPSS, Qmax, Qave, PVR, and QoL score by the postoperative first month compared to the preoperative values in both groups. Maximum improvement in the IPSS, Qmax, Qave, QoL score and PVR were achieved at postoperative 6, 3, 12, 3 and 12th months respectively in group 1. In group 2 maximum improvement in the same parameters were achieved at postoperative 6, 3, 6, 6 and 12th months, respectively. BiVap and Twister systems are safe, effective, and useful technique, which can be used in the surgical treatment of BPO between 90-150 ml.

IR-Photometry Method for Measuring Glucose Concentration in Peritoneal Dialysis Fluid

Introduction. The transition of glucose into the blood during automated peritoneal dialysis with regeneration of the dialysis fluid leads to a decreased removal of excess fluid from the body and corresponding violations of the water-salt balance.Aim. To consider a system for automatically maintaining the concentration of glucose in the dialysate solution, which provides effective ultrafiltration, as well as to propose a non-contact photometric feedback sensor.Materials and methods. The sensor is an optical system of an IR laser diode with a power of 30 mW and a wavelength of 1600 nm, a photodiode and a quartz tube, through which the test solution circulates. The sensor measures the attenuation of the radiation passing through the solution in a pulsed mode and calculates the glucose concentration. The selected combination of digital filters provides compensation for the noise of the optical system. Experimental studies of the efficiency of the sensor were carried out on peritoneal dialysis solutions with various concentrations of urea, creatinine, uric acid and glucose. At the beginning of the experiments, the sensor was calibrated in a pure solution.Results. It was shown that the developed sensor makes it possible to measure the concentration of glucose in a solution for peritoneal dialysis in the range of 42…220 mmol / l with a relative error of about 15%. The time of one measurement is about 1 minute, which makes it possible to obtain up-to-date information on the current concentration of the solution.Conclusion. This combination of characteristics will allow the sensor to be used in artificial kidney wearable devices for assessing the glucose content in the solution, calculating the time to change the solution and as a feedback sensor in a system for maintaining the concentration of the osmotic agent.

Analysis of Thermal Effect in Thin Disk Laser: A Review

Since its first invitation in 1993, solid-state diode end-pumped thin-disk laser attracts much attention due to its significant improvements in the solid-state laser system. It had many advantages; it has high optical and electrical efficiency, high produced peak power, a simple cooling system, and high beam quality more than the usual solid-state diode laser system. The thin-disk laser (TDL) permits an effective pulse mode, which permits a new type of very short-pulsed laser system that could be used in the industry. Due to the influence of the many factors such as effective cooling system, the type of pumping, and the used thin crystal, a one-dimensional heat flow through thin-disk laser could be achieved which permits excellent enhancement in the beam quality. Finally, in this work, a review is made to the works devoted to discussing the basic principle and the solutions used to analyze the thermal effect in the thin disk laser.

Laser Technology for the Formation of Bioelectronic Nanocomposites Based on Single-Walled Carbon Nanotubes and Proteins with Different Structures, Electrical Conductivity and Biocompatibility

A laser technology for creating nanocomposites from alternating layers of albumin/collagen proteins with two types of single-walled carbon nanotubes (SWCNT) at concentrations of 0.001 and 0.01 wt.% was proposed. For this purpose, a setup with a diode laser (810 nm) and feedback system for controlling the temperature of the area affected by the radiation was developed. Raman spectroscopy was used to determine a decrease in the defectiveness of SWCNT with an increase in their concentration in the nanocomposite due to the formation of branched 3D networks with covalent bonds between nanotubes. It was revealed that adhesion of proteins to branched 3D networks from SWCNT occurred. The specific electrical conductivity of nanocomposites based on large SWCNT nanotubes was 3.2 and 4.3 S/m compared to that for nanocomposites based on small SWCNT with the same concentrations—1.1 and 1.8 S/m. An increase in the concentration and size of nanotubes provides higher porosity of nanocomposites. For small SWCNT-based nanocomposites, a significant number of mesopores up to 50 nm in size and the largest specific surface area and specific pore volume were found. Nanocomposites with small SWCNT (0.001 wt.%) provided the best cardiac fibroblast viability. Such technology can be potentially used to create bioelectronic components or scaffolds for heart tissue engineering.

New evidence from hyperspectral imaging analysis on the effect of photobiomodulation therapy on normal skin oxygenation.

The aim of this study was to assess the changes induced by photobiomodulation therapy in oxygenation of normal skin and underlying tissue using hyperspectral imaging combined with a chemometric regression approach. Eleven healthy adult volunteers were enrolled in this study. The dorsal side of the left hand of each subject was exposed to photobiomodulation therapy, while the correspondent side of the right hand was used as a control (placebo effect). Laser irradiation was performed with a laser diode system (635nm, 15mW, 9J/cm2) for 900s. Changes in skin oxygenation were assessed before and after applying the photobiomodulation therapy and placebo using the hyperspectral imaging. Hyperspectral data analysis showed that variations of oxyhemoglobin and deoxyhemoglobin concentrations had no statistical significance in both groups. In conclusion, photobiomodulation therapy does not induce changes in oxyhemoglobin and deoxyhemoglobin concentrations in the normal skin measured from hyperspectral images, at least at λ = 635nm and 900-s exposure time.

Laparoscopic treatment of deep endometriosis with a diode laser: our experience

PurposeTo evaluate whether laparoscopic treatment with a diode laser is feasible, safe, and effective in symptomatic patients affected by deep endometriosis (DE).MethodsThis retrospective study was performed using medical record data. The surgical reports, chronic pain scores, and quality of life (QoL) data were evaluated for 50 patients who had undergone laparoscopic surgery between November 2017 and March 2019 at two university hospitals (Monserrato (CA) and Foggia, Italy). Indications for surgery were chronic pelvic pain and/or infertility in patients who wished to conceive spontaneously. Endometriosis lesions/nodules were excised using a diode laser (Leonardo®, Biolitec® DUAL 45) that can combine 980 and 1470 nm wavelengths transmitted through a 1000 µm conical optical fibre.ResultsThe median patient age was 32 years (range 21–44), with a body mass index (BMI) mean of 21.7 ± 2.9 kg/m2. The mean operation time was 147 min (range 106–190). No intraoperative or early complications (< 30 days) were reported. All patients left the hospital, on average, within 3 days (range 2–9 days) after surgery. A significant improvement in pain was observed at the 3-, 6-, and 12-month follow-up (p < 0.01) in all patients. Moreover, patients reported a significant QoL improvement at the 12-month follow-up.ConclusionThe diode laser confirmed its feasibility and safety for treating endometriosis. During the shaving surgical procedure, the diode laser system ensures a safe and effective laparoscopic dissection of deep endometriotic lesions. Further comprehensive randomized trials are necessary to confirm these preliminary data in terms of efficacy, recurrence rates, and pregnancy outcomes.

Micro-optics assembly for fast axis collimation by means of convolutional neural network.

The manufacture of high-power diode laser systems highly depends on the quality of the collimation of semiconductor laser diodes. The collimation process is conducted by precise alignment of micro-optics, where the first and the most critical step is the placement of the fast axis collimator (FAC) lens. The sub-micron positioning of the FAC lens is conventionally conducted with an active alignment strategy by monitoring changes in the laser beam profile with an external sensitive camera. The optimization of the beam profile characteristics is controlled by a specifically programmed motorized robotic aligner. However, active alignment, a very accurate method, often results in a higher cycle time than the passive approach, where the lens is placed in a pre-measured position. Here, we developed a new active approach, without closed loop control to position the micro-optics, that relies on the use of a pretrained convolutional network (CNN). We trained and evaluated three CNNs that can predict the optimal lens position using the single camera image of the laser beam. We predict that implementation of the best performing CNN-based model would lead to a decrease in alignment time from tens of seconds to hundreds of milliseconds and will be broadly applied in a high-volume manufacturing environment.

Adaptive High-Power Laser-Based Simultaneous Wireless Information and Power Transfer System With Current-Fed Boost MPPT Converter

A laser beam is an effective power and data carrier that offers inherent advantages in terms of the simultaneous transfer of wireless information and power, which is widely used in both the Internet of Things and the Internet of Energy. This paper proposes an adaptive high-power and high-efficiency laser-based simultaneous wireless information and power transfer system. This is achieved through the use of adjusted and modulated laser diode systems at the transmitter and multiplexed photovoltaic cells, a coupler, a filter, and a maximum power point tracking (MPPT) converter at the receiver. The interaction between the converter and the communication component is investigated theoretically and experimentally using a current-fed boost MPPT converter with the MPPT algorithm of perturbation and observation. The results indicate a maximum DC output power of 7.3 W at the receiver and a maximum MPPT converter efficiency of 84%. Additionally, at a data rate of 495 kbit/s, with a DC output power of 5.11 W, the bit error ratio is 2.62 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> for the binary amplitude shift keying modulation format, the MPPT converter efficiency is 88%, and the corresponding loss of communication is about 1% of the total transmitted power.