Diode Lasers

T he dynamics of the injection-locking architecture with semiconductor lasers on photonic integrated circuits or on a tabletop configuration with discrete devices have been investigated analytically, numerically, and experimentally for the past 45 years. Today, this simple-looking optical system, which involves only one slave and one master diode laser, keeps delivering surprising physics results and spinning out radical engineering applications. In this article, we review the legacy results of its intricate behavior and articulate a set of forwardlooking applications, spanning from tunable oscillators and ultrafast transmitters to dynamically empowered metamaterials and photonic quantum processors.

Dental implant surgery has developed to a widely used procedure for dental rehabilitation and is a secure and predictable procedure. But, some local and systemic risk factors can result in higher failure rates and affect implant survival. Peri-implant disease, namely peri-implantitis, have been extensively studied in present era as a major cause of implant failure. There are various treatment modalities to treat peri-implantitis, which give satisfactory results and improve survival rate of implant. Though it is difficult to determine what approach will improve implant survival, present case report is an attempt to treat peri-implantitis with implantoplasty and diode laser followed by regenerative peri odontal therapy.

We present a novel implementation of the “phase reconstruction using optical ultra fast differentiation” (PROUD) technique and apply it to characterize the time resolved chirp of a gain switched semiconductor laser. The optical temporal differentiator is a fiber based polarization interferometer. The method provides a fast and simple recovery of the instantaneous frequency from two temporal intensity measurements, obtained by changing the spectral response of the interferometer. Pulses with different shapes and durations of hundreds of picoseconds are fully characterized in amplitude and phase. The technique is validated by comparing the measured pulse spectra with the reconstructed spectra obtained from the intensity and the recovered phase.

A laser safety analysis for liquid-crystal–on–silicon (LCOS) based imaging projection systems
utilizing laser light sources is presented. It is shown that a typical laser-based imaging projector
is capable of providing a D65 white-balanced luminous flux in excess of 20 lm while remaining Class
1 eye safe. By considering a Class 2 classification, it is shown that the same architecture is capable of
providing several hundred lumens, a performance level which could potentially be applicable to a
new class of high-brightness miniature projection systems.

In any wavelength sensitive application, extensive care should be taken in addressing the wavelength drift issues. In the case in which laser tuning is conducted by using thermoelectric cooler, an accurate expression is needed to describe transient characteristics of the Peltier device to achieve maximum controllability. In addition, thermal tuning issues are of particular relevance to the field of photonic integration. In this paper, the exact solution of the governing equation is presented, considering Joule heating, heat conduction, heat flux of the laser diode, and the thermoelectric effect in one dimension. In addition, the variable separation method and the Sturm–Liouville theorem, along with the completeness features of eigenfunctions, are used to obtain time-dependent electrical potential and temperature distribution of the Peltier device. Additionally, steady-state sensitivity analysis is performed in order to demonstrate the impacts of physical parameters on its thermoelectric characteristics. Transient temperature is also considered that, for a specific case, revealed fast transition to steady-state condition with time constant lower than 400 ms. Lower heat capacity, as well as laser diode heat flux, might lead to faster Peltier response times, such that the effect of heat flux on response time becomes negligible in low heat capacity Peltier.

We report a new simple and inexpensive sub-micrometer two dimensional patterning technique. This technique combines a use of a photomask featured with self-organized particles in the micro-to nanometer size range and a photoresist-covered substrate. The photomask was prepared by depositing monodispersed silicon dioxide (SiO 2 )-or polystyrene-spheres on a quartz substrate to form a close-packed pattern. The patterning technique can be realized in two configurations: a hardcontact mode or a soft-contact mode. In the first configuration, each sphere acts as a micro ball-lens that focuses light and exposes the photoresist underneath the sphere. The developed pattern therefore reproduces exactly the same spatial arrangement as the close-packed spheres but with a feature size of developed hole smaller than the diameter of the sphere. In the softcontact mode, an air gap of few micrometers thick is introduced between the 2D array of self-organized spheres and the photoresist-covered substrate. In this case, a phase mask behavior is obtained which results in an exposure area with a lattice period being half of the sphere diameter. A 2D lattice structure with period and feature size of a developed hole as small as 750 nm and 420 nm, respectively, was realized in this configuration. We further applied this technique to host the deposition of organic films into the 2D nanostructure and demonstrated the realization of green and red nanostructured OLEDs.

Lasers are a relatively new addition to the orthodontist's armamentarium. This article reviews the fundamental basic science of available soft-tissue lasers, with an emphasis on diode lasers, and discusses various adjunct applications of the diode laser for soft-tissue orthodontic procedures. Diode lasers function by cutting with an initiated hot tip and produce minimal to no interaction with healthy dental hard tissue, making them suitable for soft-tissue procedures. The contact cutting mode provides enhanced bloodless site visibility and facility to perform delicate soft tissue procedures, which is important in areas with difficult access. Such adjunctive uses include laser gingivectomy to improve oral hygiene or bracket positioning, esthetic laser gingival recontouring, and laser exposure of superficially impacted teeth. Selected cases treated with a 940-nm indium-gallium-arsenide-phosphide (InGaAsP) diode laser will be presented.

The effect of built-in polarization on the performance characteristics of green InGaN single quantum well (SQW) laser diode (LD) structures with ternary AlGaN or quaternary AlInGaN electron blocking layer (EBL) having the same bandgap energy, was investigated numerically. Simulation results indicated that using quaternary AlInGaN EBL effectively improves the performance characteristics of green InGaN SQW LDs. Using AlInGaN EBL significantly reduces the built-in polarization and fixed polarization charge densities at the EBL and the last InGaN barrier interface. Furthermore, using quaternary AlInGaN EBL increases the radiative recombination and decreases the non-radiative recombination in the well. The laser structure with AlInGaN EBL has lower threshold current, and higher output power, differential quantum efficiency (DQE) and slope efficiency compared with the laser structure with conventional AlGaN EBL.

Continuous-wave ultraviolet radiation has been generated by frequency doubling the output of a 15-mW, 634-nm diode laser with a rubidium dihydrogen phosphate (RDP) crystal inside an external resonant cavity. Singlefrequency operation (2 MHz linewidth) of the diode laser is obtained by employing weak optical feedback from a microlens. By using the resonant cavity, a power buildup factor of 60 is achieved and up to 30 µW of tunable ultraviolet radiation around the wavelength of 317 nm has been produced. PACS: 42.65.Ky; 42.55.Px Compact, reliable, and efficient ultraviolet (UV) lasers are essential for many applications ranging from optical data storage to spectroscopic analysis. Diode lasers would be almost ideal light sources for these applications, except that their available wavelength range covers only the red and infrared part of the spectrum. Generation of shorter wavelength radiation is, however, possible by frequency conversion in a nonlinear crystal. Previous demonstrations [1-3] have shown that efficient generation of continuous-wave UV radiation can be achieved by second-harmonic generation (SHG) of red diode lasers with a nonlinear crystal placed in a resonant cavity. Ultraviolet powers of 18 µW at 370 nm [1], 35 µW at 369 nm [2], and 260 µW at 344 nm have been reported. In related work, two successive resonant cavities have been used to quadruple the frequency of a high-power nearinfrared diode laser to generate 2.1 mW of UV radiation at 243 nm . Generation of UV radiation using quasi-phase matching (QPM) to enhance the conversion efficiency has also been demonstrated . Applying QPM in a periodically poled bulk crystal and a diode laser pump, Mizuuchi et al. reported UV power of 30 µW at 340 nm [6]. However, efficient generation of shorter wavelengths using QPM technique is presently limited by difficulties in poling dense (∼ 1 µm) first-order periods with high optical quality . * Corresponding author Our work is primarily motivated by the need for lasers in radiometric characterization of detectors in the biologically interesting solar UV band 300-320 nm . It should be noted that laser sources are not readily available in this narrow UV band. The importance of high-accuracy detector characterization near 300 nm has been emphasized by the increase of biologically harmful solar UV radiation due to depletion of stratospheric ozone. For this purpose a continuouswave laser with an output power of a few tens of microwatts is required. The recent development of 635-nm diode lasers has made frequency doubling to this UV band possible.

Haemangioma is the most common benign tumor of vascular origin of the head and neck region. This paper reports the management of a 39 year old female patient with capillary haemangioma on the ventral surface of the tongue and the floor of the mouth using 980 nm diode laser.

Compact, tunable, low-power consumption coupled-cavity lasers are designed and experimentally demonstrated. Single-mode operation with an SMSR >24 dB and >11 nm tuning range are achieved, being suitable as on-chip local oscillators in low-power integrated optical coherent receivers.

This paper deals with the simulation and implementation of boost Converter with the need for power factor correction, the utilization of active clamping technique in the boost converter, this circuit incorporation of compound active clamping boost converter, its modes of operation and analysis of step of chopper. This analysis involves the simulation analysis of the compound active clamping boost PFC converter. It gives the details about the circuit implementation. The laboratory model is implemented and the experimental results are obtained. These experimental results are correlated with the simulation results.

The aim of this study is to evaluate and compare the clinical efficiency of gingival depigmentation procedure with conventional scalpel and diode laser techniques. Materials and methods: This study was carried out as a randomized controlled clinical trial, split mouth design, in which fifteen patients having diffuse continuous physiologic pigmentation of the gingiva involving facial aspect of maxillary right to left premolar area were selected. The maxilla was divided into two halves and randomly allotted for "study site" for depigmentation with diode laser technique, and "control site" for depigmentation with scalpel technique. The studied variables were the degree of pain, bleeding, duration of the procedure, wound healing, and level of melanin repigmentation. The follow-up period was twelve months. For statistical analysis, Wilcoxon signed-rank test were conducted. Results: The diode laser technique showed better results regarding pain during the first three days, duration of the procedure, and bleeding. There was no significant difference between diode laser technique and scalpel technique regarding the wound healing and pain experienced by the patient after one week of surgery. Both sites showed recurrence of pigmentation, yet it was after a shorter period on the scalpel site. Conclusion: The findings of the present study suggest that gingival depigmentation was effective with both

Multilevel inverters have already gained high popularity among research teams as well as in production of high and medium-voltage applications for industrial purposes over the period of twenty years. Moreover, multilevel inverters are able to generate switched waveforms with reduced levels of harmonic sag compared to a conventional converter. Recent increased interest in multilevel inverters is due to their ability to generate high quality output waveforms at lower switching frequencies; the multilevel topology used in dynamic voltage restorer works towards the reduction of the total harmonic distortion counting all of the losses at the output end. This paper provides a new topology for the modulation in the multilevel inverter using switched capacitor. The self-balancing capability for the capacitor voltage and the SC connected in parallel so as to provide the voltage setup. The methodology presented works towards minimizing the THD by implementing the 9 level MLI and comparing the same to the other level in terms of distortion. The factors like cost are also considered in the design for which half bridge is being used.

A frenum is a soft tissue attachment of the labial, buccal and lingual mucosa to the jaw bones. Abnormalities in development of this soft tissue fold may present as a very short lingual frenum limiting the mobility of the tongue. This condition is termed as ankyloglossia or tongue tie. The surgical technique is used to reposition the frenum and correct the functional impairments caused by ankyloglossia. This case report presents a 30 years old male patient with impairment of speech due to the short lingual frenum. 980 nm diode laser was used for frenectomy which showed minimal pain and healing with no complications. Surgical procedures like frenectomy and biopsy of oral lesions can be effectively carried out using Diode laser.

Aim: This study aims to evaluate the bacterial reduction after conventional root canal treatment using 5.25% sodium hypochlorite. Materials and Methods: The study criteria included 100 patients requiring root canal treatments due to pulpitis. The diagnosis was made based on objective clinical signs (examination, probing, percussion, palpation) and X-ray investigation. The clinical procedures were carried out under strict aseptic precautions. All patients were subjected to biomechanical preparation followed by irrigation using sodium hypochlorite at a concentration of 5.25% which is considered the highest concentration without causing any toxic effect on the patient. All microbiological samples were taken immediately after the access preparation baseline (S1) and after the completion of the root canal instrumentation and disinfection with 5.25% sodium hypochlorite (S2) and sent for microbiological analysis. Results: One hundred patients with infected root canal were selected for this in vivo study. All S1 samples were positive for microbial isolates, 71 samples harbored cultivable bacterial isolates, 22 were fungus (Candida albican), and 7 samples showed no growth so in total adding up to 151 isolates identified from 100 patients. Bacterial isolates before chemomechanical treatment showed the highest prevalence belonging to Enterococcus faecalis followed by Streptococci, Staphylococci and Candida albican. After the chemomechanical treatment with 5.25% of sodium hypochlorite no cultivable bacteria were isolated from 38 patients root canals, and therefore the treatment managed to eradicate 54% of the 151 isolated bacterial species from the 71 infected root canals. Conclusion: The antimicrobial effect of 5.25% sodium hypochlorite was effective in eradicating a high number of the bacterial isolates along with the fungus identified in infected root canals. This high concentration of sodium hypochlorite presented no toxic damage to the root canal or the area around it when handled with care.

LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. Over the years, lasers have advanced imperceptibly in our day to day life from recording price of groceries to laser guided warfare. Lasers saw the light of day due to Ted Maiman in 1960 but it was not until 1980’s that lasers saw their use in dental clinical practice. This article reviews the uses of diode lasers in dentistry.

In this paper we study laser diode parameters in fiber optic communication system and we study the relationship between them. The capacity of optical communication systems is rising exponentially in order to follow the rapidly increasing demand for data traffic. Limitations due to dispersion and nonlinearity in the optical fiber become more stringent for higher bit rates.. In optical communication transmitters are light sources, receivers are light detectors and the channels are optical fibers. In optical communication the channel i.e., optical fiber plays an important role because it carries the data from transmitter to the receiver. Laser is a powerful source of light having extraordinary properties which are not found in the normal light sources like tungsten lamps, mercury lamps, etc..Laser surgery has also provided itself to be a preferred tool of operation over standard tools in a lot of the cases.