Diode Laser System Research Articles

Effects of Gain Saturation on Orbital Instability of Chaotic Laser Diode with External Pseudorandom Signal

In a laser diode (LD) system with optical injection, the effects of gain saturation of the LD on the orbital instability of the system are analyzed numerically. For the optical injection LD system without signal application, it is shown that the effect of optical injection is suppressed in the system with gain saturation and small optical injection, and that a higher amount of optical injection is necessary to obtain similar dynamics. Next, in the optical injection LD system with a pseudo-random signal applied to the LD drive current, it is confirmed that when the dynamics are a periodic window between chaotic and chaotic regions, chaotic dynamics are actualized as the standard deviation of the applied signal becomes larger. Furthermore, it is suggested that this phenomenon can be explained by linear stability analysis, and it is shown by introducing randomly varying tentative gain coefficients that gain fluctuations that lead to an expansion of the chaotic region. Hence, the results of this study provide research on the effects of gain saturation on chaotic oscillation in LDs with pseudo-random signals applied and contribute to the generation of more complex chaotic signals, chaotic secure communication, and random number generation.

Dynamic regimes of time—delay signature of a semiconductor laser subjected to incoherent optical feedback

The effect of incoherent optical feedback to a semiconductor diode laser is numerically investigated using Lang-Kobayashi rate equations. The model constitutes for diode laser systems in which the feedback loop length is longer than the coherence length of the laser. The time delay signature (TDS) of the external cavity is found to exhibit dynamical regimes corresponding to the incoherent feedback. The occurrence of time delay signature and its characteristics such as temporal spread exhibit a definite relation to the regimes of incoherent optical feedback. Lasing efficiency, threshold current and turn-on-delay characteristics also exhibit concurring regimentation of incoherent optical feedback to a semiconductor diode laser.

Ultra-low frequency noise external cavity diode laser systems for quantum applications

We present two distinct ultra-low frequency noise lasers at 729 nm with a fast frequency noise of 30 Hz2/Hz, corresponding to a Lorentzian linewidth of 0.1 kHz. The characteristics of both lasers, which are based on different types of laser diodes, are investigated using experimental and theoretical analysis with a focus on identifying the advantages and disadvantages of each type of system. Specifically, we study the differences and similarities in mode behavior while tuning frequency noise and linewidth reduction. Furthermore, we demonstrate the locking capability of these systems on medium-finesse cavities. The results provide insights into the unique operational characteristics of these ultra-low noise lasers and their potential applications in quantum technology that require high levels of control fidelity.

Effectiveness of KTP lasers in tooth bleaching, by comparing tooth color change after bleaching with KTP, Nd:YAG, Er:YAG, and diode laser system: A systematic review.

This systematic review evaluated the role of Potassium-titanyl-phosphate (KTP) lasers in dental bleaching by comparing tooth color change and rise in intrapulpal temperature after bleaching with KTP, Neodymium-doped yttrium aluminum garnet (Nd:YAG), Er:YAG, and diode laser system. Following were the inclusion criteria: in vitro studies in English available in full text. Articles published between 2000 and 2021 were selected. The search for was conducted on PubMed, Cochrane library/CENTRAL, Wiley online library, ProQuest, Science Direct, and Hand searching/specialized registers. Keywords were used: "Lasers" [Mesh] and "Tooth bleaching" [Mesh] using Boolean operators. A total of four articles fulfilled the inclusion criteria. The quality assessment of studies included was undertaken independently as part of data extraction process. KTP lasers demonstrated more effectiveness in attaining color change in stained teeth and showed the lowest rise in intrapulpal temperature. Based on the data obtained in the present review, the choice of bleaching treatment is directly related to the type of discoloration, activation of the bleaching agent, and esthetic requirement. Although all bleaching procedures were effective in color change, the KTP laser showed better results when compared to other laser activation. The bleaching treatment protocol is directly related to the type of discoloration, activation of the bleaching agent, and esthetic requirement. It has been demonstrated that a faster change in color can be obtained when bleaching is performed in combination with a light source, i.e., power bleaching aiming for a more in-depth change of color.

Simple Characterization of Cylindrical Diffuser Fibers With a Fluorescent Layer.

A fast, simple, versatile, and reliable method to record light emission intensity profiles of cylindrical light diffusers (CDFs) in air and transparent liquids has been developed. A fluorescent color glass filter (RG695) converts red light emitted by a cylindrical diffuser fiber into near-infrared light in an emission angle-independent manner. The red light was provided from a diode laser system at 635 nm. Near-infrared fluorescence from the RG695 was imaged with a camera. Images from this camera were processed to obtain emission intensity profiles. Cylindrical diffuser fiber profiles of four different manufacturers were compared. The proposed method provides angle-independent intensity profiles of cylindrical diffuser fibers with a single camera shot. It could be demonstrated that dependent on the underlying principle of how the diffuser fiber tips emit light, the emission profile can change significantly in media with different refractive indices. By converting the light emitted by a diffuser fiber tip into fluorescence light one can eliminate the dependence of the recorded profile on the emission angle from the diffusor. This approach allows for easily taking into account refraction-index (mis)matching by placing the equipment into a suitable liquid. The proposed measurement principle bears potential for quality assurance measurements of CDFs used for interstitial laser thermotherapy or photodynamic therapy.

Low phase noise cavity transmission self-injection locked diode laser system for atomic physics experiments

Lasers with high spectral purity are indispensable for optical clocks and for the coherent manipulation of atomic and molecular qubits in applications such as quantum computing and quantum simulation. While the stabilization of such lasers to a reference can provide a narrow linewidth, the widely used diode lasers exhibit fast phase noise that prevents high-fidelity qubit manipulation. In this paper, we demonstrate a self-injection locked diode laser system that utilizes a high-finesse cavity. This cavity not only provides a stable resonance frequency, it also acts as a low-pass filter for phase noise beyond the cavity linewidth of around 100 kHz, resulting in low phase noise from dc to the injection lock limit. We model the expected laser performance and benchmark it using a single trapped 40Ca+-ion as a spectrum analyzer. We show that the fast phase noise of the laser at relevant Fourier frequencies of 100 kHz to >2 MHz is suppressed to a noise floor of between −110 dBc/Hz and −120 dBc/Hz, an improvement of 20 to 30 dB over state-of-the-art Pound-Drever-Hall-stabilized extended-cavity diode lasers. This strong suppression avoids incoherent (spurious) spin flips during manipulation of optical qubits and improves laser-driven gates when using diode lasers in applications involving quantum logic spectroscopy, quantum simulation, and quantum computation.

Laser Exposure Systems for Multiwell Plate Photodynamic Therapy (PDT) Treatments: Reactive Oxygen Species Generation and Photocytotoxicity

SignificanceThe study demonstrated the development of two low-cost custom laser diode exposure systems for early-stage PDT studies that provide homogenous output power at the target regions at specific wavelengths, during the duration of treatment. ApproachTwo custom laser diode exposure systems were built and optimized for high-throughput PDT applications. The power output for tested laser diodes was quantified and the photosensitizer induced photochemistry was evaluated using a cell-free and an in-vitro assay. ResultsThe experimental results showed that the laser exposure system was suitable for PDT experiments up to 10mW/cm2. The laser power was homogenous for the 4- and 6-well illumination with variable irradiation exposure time. The photoactivation of photosensitizers showed consistent results with the cell-free SOSG and in-vitro NRU assay. ConclusionsThe laser diode systems developed by the authors for use in high throughput PDT experiments, provided uniform and stable output up to 10mW/cm2. Variation between the output power was less than 10%The results obtained using the cell-free SOSG and in-vitro NRU assay were consistent and in agreement with the literature.

Light emitting diode and laser diode system behaviour description and their performance signature measurements

Abstract This paper has clarified the light emitting diode and laser diode system behaviour description and their external quantum efficiency measurements. Light output of LED spontaneous emission and laser diode stimulated emission are clarified. Stimulated and amplified spontaneous emission of laser diode and LED system configuration are demonstrated. The management of hybrid light sources spectrum illumination interaction for efficient solar cells light intensity and short circuit current density enhancement. The laser diode has presented better performance in the light output power especially under the same temperature effects. It is ensured that the dramatic effects of the temperature on both laser diode performance efficiency.

Growth of β-Ga2O3 crystal with a diameter of 30 mm by laser-diode-heated floating zone (LDFZ) method

To investigate the effect of high-power laser heating on the floating zone (FZ) method, a crystal of β-Ga2O3 was grown by the LDFZ method using a newly developed optical system equipped with a 20-kW laser diode (LD) system as a heat source. The growth started from a twin-free seed crystal with a diameter of 7 mm and the diameter of the crystal was increased gradually up to 30 mm. With increasing the diameter of the crystal, three patterns of the beam intensity profile were switched to heat the whole of the molten zone locally and intensively. The intensity profile of the five beamlets irradiating the sample was adjusted with a combination of the zooming by the optical system and the partial blocking by the alumina cylinder. By the proper tuning of the beam profile and the proper selection of the diameter of the feed rod, the molten zone was kept stable against gravity. The obtained crystal has a layer texture without clear facets or cracks. It almost conserves the crystallographic direction of the seed crystal but is twinned except for a twin-free region near the seed crystal.

Feasibility analysis for the application of conduction tracks on textiles by means of laser radiation

Textiles are not only used for clothing but also have found applications in many other areas. Textiles fulfilling functional or technical properties are called “technical textiles.” Incorporation of conductive components, sensors, or materials reacting to environmental influences convert those into so-called “smart textiles.” Common methods of applying conductive tracks to textiles are embroidery, which can cause damage to the textile, or printing of a low-conductivity paste that may include toxic chemicals. A new method of applying electrical conductors to textiles for contacting is laser welding. In this process, a thin metal foil is welded on locally with an absorber placed above the metal foil to ensure that sufficient energy is applied to partially melt the textile underneath the metal foil. One variant for welding conductive tracks is the use of a globo-optics and a diode laser system with a wavelength of 975 nm. With these optics, the glass sphere focuses the laser beam and serves as a mechanical pressure tool for achieving a zero gap between fabric and foil. Parameters that are varied are the processing speed and the laser power receiving different track widths, as well as the type of textile. In this work, their influence is evaluated by microscopy, electrical resistance measurements during Martindale tests for abrasion resistance, and tensile tests. The investigations clarify the durability and utility of welded conductive tracks on textiles. It is possible to produce conductive tracks out of beaten copper joined on textiles using laser radiation showing conductivity after 10,000 abrasion cycles. The tensile strength of textiles totally made of thermoplastics is more influenced by the heat input of the laser than blended textiles, but their abrasion resistance is worse. Furthermore, an outlook on the possibility of welding using a laser source with a wavelength of 450 nm (blue laser) and a scanner as optics will be given.

Hysteroscopic metroplasty using a dual-wavelength diode laser system: A single center experience

Hysteroscopic metroplasty using a dual-wavelength diode laser system: A single center experience

Simple three-stage frequency-stabilized diode laser system using injection-locking and tapered amplifier

Simple three-stage frequency-stabilized diode laser system using injection-locking and tapered amplifier

Development of a blue-violet high-power single-frequency diode laser system for 48Ca isotope separation

Development of a blue-violet high-power single-frequency diode laser system for ⁴⁸Ca isotope separation

Comparative Efficacy of Diode Laser System versus Intense Pulse Light (Ipl) In Management of Unwanted Hair

Unwanted hair growth can be caused by several factors, including genetics, systemic illness, and even drug reactions. According to the underlying medical condition, excessive hair growth was labelled as either hirsutism or hypertrichosis. Objective: To compare the efficacy of diode laser system versus intense pulse light in the management of unwanted hair among female patients. Methods: Patients in this randomized controlled study had hirsutism. Group A received powerful pulse light therapy for three sessions, one month apart, while Group B received diode laser treatment. To determine the effectiveness and side effects in both groups, patients were monitored for four months and subsequently assessed clinically. Results: Out of these total 60 patients, intense pulse light system was more efficacious in achieving patient satisfaction (73.3%) at the end of three months as compared to diode laser (26.7%) (p value < 0.001). Conclusions: This randomized controlled trial showed that intense pulse light therapy was more efficacious in management of unwanted hair compared to diode laser therapy.

Development of a high‐power blue diode laser for precision vaporization of prostate tissue for the surgical management of benign prostatic hyperplasia

AbstractThis paper explores the advancement and application of high‐power blue diode lasers in treating benign prostatic hyperplasia (BPH). Addressing the challenges posed by existing techniques, the study focuses on optimizing tissue removal methods. Energy platform for BPH should balance a range of factors, such as operative time, patient conditions, urinary functions, complications, durability, accessibility, and cost, all while prioritizing patient care. Blueray Medical's innovation of high‐power blue diode laser systems for BPH surgery is explored, with emphasis on achieving a balance among these considerations. By illustrating the biomedical effects of lasers and their interaction with soft tissues, particularly emphasizing the role of photon absorption by biomolecules and proteins in tissue behavior, this study outlines the advantages of the high‐power blue diode laser system. The initial laboratory experiments and clinical results consistently align with our theoretical predictions, especially in terms of tissue vaporization efficiency, tissue coagulation, and bleeding control. In conclusion, blue diode lasers hold potential to enhance surgical outcomes for BPH. Their unique properties offer benefits like improved tissue removal rate and reduced thermal damages. Integrating blue laser technology into BPH protocols could lead to shorter hospital stays, cost savings, and expanded patient eligibility, although rigorous clinical studies are needed to fully understand their benefits and limitations.

High-brightness green laser diode that uses a multi-order half-wave plate to realize twice-combined polarized beams

In this paper, we describe a method for realizing twice-combined polarized beams by selectively changing the polarization state of lasers with different wavelengths. This improves the output power and brightness of a green laser diode system. A multi-order half-wave plate plays a significant part in combining the polarization states of the first-combined polarized beam by changing the polarization state from orthogonal to approximately parallel. We obtained a maximum output power of 2.85 W and a laser brightness of 25.36 MW/cm2·sr with an optical–optical conversion efficiency of 82.85% and a spectral width of 15.48 nm. Compared with traditional methods for combining polarized beams, the output power is improved by 22.85% and the brightness by 8.65%. This structure provides a new technology for achieving high output power and high brightness from a green laser diode system, and it breaks through the limit of the number of laser units that can be used in combining polarized beams.

Formation of emission in diode lasers with evaporation of various impurities on the main semiconductor crystal having affinity to electron

The introduction contains a summary of modern provisions that make it impossible to interpret many phenomena occurring in diode laser systems on the basis of commonly accepted physical conceptions. The work demonstrates their inadequacy. The goal and tasks of studies have been formulated. Analysis of a solid and its internal structure (crystal) is provided. It is demonstrated that interaction of plane surface clusters determines the surface structure of solids, while the interaction between three-dimensional clusters determines the internal structure of solids (crystals). Each atom inside the crystal interacts with the first, second and third coordination layer. The value of conduction band energy is determined by displacement of the ionization boundary. For implementation of diode lasers, the distribution of electrons by Fermi-Dirac energies must have a sufficiently diffused maximum. N-conductivity emerges when ionization of negative ions occurs, the energy of affinity of which is located near the conduction band. Р-conductivity is determined by ionization of negative ions, the energy of affinity of which is located near the valence band. Р-n junction is mostly formed when two-atom molecules enter the band gap. In this case, some of the atoms have an affinity for an electron with the value of such affinity located is near the conduction band, while other atoms have an affinity for an electron near the valence band. Interband transition energy contains three components: 1 – Fermi level position energy; 2 – energy of external applied electrical field, and 3 – induced energy formed by positive charge in the valence band. Generation of laser emission takes place when two-atom molecules are adsorbed on the surface of the semiconductor crystal, in which atoms have an affinity to the electron for some of the atoms near the conduction band and for other atoms near the valence band. Maximum emission intensity occurs when external applied electrical voltage fully compensates the energy of affinity to the electron located near the conduction band.

The Effect of Hyrax-Type Rapid Maxillary Expansion with or without Laser Biostimulation on Mid Palatal Suture in Children with Posterior Crossbite

Purpose: The aim of the following study was to evaluate the use of low-level laser application on the width of the Mid palatal suture (MPS) after rapid maxillary expansion. Materials and methods: patients age range 10 ± 2.5 years were prospectively selected from outpatient clinic of the Orthodontic Department, Faculty of Dental Medicine for Girls, Al-Azhar University (Girls’ Branch). Each patient was examined, full diagnostic records and cone beam computed tomography (CBCT) were taken before appliance cementation (T0), after six months and at the end of retention phase (T1). The hyrax appliance was used for rapid maxillary expansion (RME). The activation protocol of the expansion screw was 2 full turns daily. The laser type used was the e Epic™ X diode laser system, 940 nm wavelength, 40 mW power, and 10 J/cm2 density. Results: No significant differences were found in the two areas between the control and the laser group. Conclusions: The mid palatal suture width showed no statistical significant differences between the control and laser group in anterior and posterior region.

The Effect of Hyrax-Type Rapid Maxillary Expansion with or without Laser Biostimulation on Mid Palatal Suture in Children with Posterior Crossbite

Purpose: The aim of the following study was to evaluate the use of low-level laser application on the width of the Mid palatal suture (MPS) after rapid maxillary expansion. Materials and methods: patients age range 10 ± 2.5 years were prospectively selected from outpatient clinic of the Orthodontic Department, Faculty of Dental Medicine for Girls, Al-Azhar University (Girls’ Branch). Each patient was examined, full diagnostic records and cone beam computed tomography (CBCT) were taken before appliance cementation (T0), after six months and at the end of retention phase (T1). The hyrax appliance was used for rapid maxillary expansion (RME). The activation protocol of the expansion screw was 2 full turns daily. The laser type used was the e Epic™ X diode laser system, 940 nm wavelength, 40 mW power, and 10 J/cm2 density. Results: No significant differences were found in the two areas between the control and the laser group. Conclusions: The mid palatal suture width showed no statistical significant differences between the control and laser group in anterior and posterior region.

Beam Shaping Technique for 5-mm Fiber-coupled Laser Diode Bars with Lens Group

In the last few years, fiber-coupled diode lasers have shown massive applications in many fields of communication and scientific research. Particularly, the pumping of solid-state lasers is a key application for more powerful diode lasers enabling good solutions in various laser micro methods like metal cutting, sintering, structuring as well as drilling. In this work, a simple beam shaping method is demonstrated for coupling a high-power semiconductor laser diode into multi-mode fiber optic using optical lenses. The optical lenses as beam transformation components are utilized to reshape the asymmetrical irradiation of the diode laser bar and to circularize the laser beam. Using this simple method, compact, high-output-power, and high-brightness fiber-coupled laser diode systems are achieved. The obtained results show that the entire optical coupling efficiency of the system is more than 65%.