Amplified Stimulated Emission Research Articles

LASER assisted soft tissue procedures for orthodontic treatment.

Light Amplified Stimulated Emission of Radiation (LASER) therapy has been the subject of numerous researches as an auxiliary method in orthodontic practice. Therefore, it is of interest to assess the clinical evaluation of laser assisted soft tissue procedures for orthodontic treatment. The soft tissue surgical procedures carried out were aestheticre-contouring, gingivectomy, maxillary frenectomy, operculectomy and surgical exposure of impacted canines. The clinical outcomes evaluated in each patient were post-operative pain, bleeding during surgical procedure. In our study, clinical evaluation of outcomes in both categories revealed reduced pain at 1 hour and 24 hour after surgical procedures in patients who underwent surgery with LASER.. Soft tissue Laser can be an alternative to conventional surgery for soft tissue surgeries in orthodontics with better pain relief and reduced bleeding.

Antimicrobial activity of laser assisted endodontic therapy in disinfecting root canals.

Light Amplified Stimulated Emission of Radiation (LASER) is nowadays widely studied regarding their use in endodontics and restorative dentistry. Therefore, it is of interest to evaluate the antibacterial activity of three types of LASERs namely CO2 LASER.Er, Cr:YSGG LASER and Diode LASER in disinfection of root canals. 70 patients (105 single rooted teeth) were included in the study. There was application of 2% Sodium Hypochlorite (NaOCl), 2780 nm Er,Cr:YSGG LASER, 900 nm Diode LASER and CO2 LASER. Microbial samples were collected from root canals both before and after the interventions through paper points. These parameters were evaluated in microbiology laboratory to obtain Log10 Colony Forming Units (CFUs). There was significant reduction in CFUs of microorganisms inside root canal in all three LASERs evaluated and NaOCl. The reduction in CFUs in LASERs was comparable to NaOCl. Then secondly we applied each LASER in combination with NaOCl. It was observed that reduction in CFU was greater when combination of LASER with NaOCl was applied as compared when applied alone. It can be inferred that LASER when applied with NaOCl can have significant role in disinfection of root canals.

Graph wavelets for fault localization in optical mesh networks

• Real-time fault detection and localization mechanism in Elastic Optical Networks (EONs). • Alarm correlation strategies fail in the face of static threshold settings. • Detects and localizes silent network failures. • Multi-resolution analysis based on graph wavelets to address fault detection and localization problems. • Exceeds alarm based engines for fault detection and localization accuracy. EONs (Elastic Optical Networks) form the backbone of web-scale cloud infrastructure. These networks should deal with network faults and restoration in real-time with high accuracy and scalability. Thus, fault management functions to detect and localize such failures, play a critical role in modern day EONs. Network impairments are complex in nature in optical networks such as fiber losses, NLI (Non Linear Impairments) and ASE (Amplified Stimulated Emission). Currently, pre-engineered thresholds are used to detect failures in optical networks. Traditional alarm correlation strategies fail in the face of these static threshold settings. In this work, we introduce a real-time fault detection and localization mechanism, which is agnostic to such pre-engineered threshold settings. We apply multi-resolution analysis based on graph wavelets to address fault detection and localization problems. Thus, we propose to use spectrograms and wavelet coefficients to identify the irregularities in an otherwise smooth graph signal. We present a real-time fault localization analysis based on a novel Wavelet Coefficients Trail (WCT) algorithm to root-cause a client signal failure due to OSNR (Optical Signal to Noise Ratio) degradation. We apply the proposed techniques and algorithms to simulated and actual network data. Our results indicate that the proposed methods can root-cause OSNR degradation to major/minor deviations in received power on optical spans. In conclusion, we present a fault localization framework based on graph wavelets in optical mesh networks.

Picosecond two-photon absorption laser-induced fluorescence (ps-TALIF) in krypton: The role of photoionization on the density depletion of the fluorescing state Kr 5p′[3/2

The present study focuses on the application of a picosecond (ps) two-photon absorption laser-induced fluorescence (TALIF) technique in krypton (Kr) at variable pressure (0.1–10 mbar). The laser intensity (I, units W cm−2) is tuned between 1 and 480 MW cm−2, and the depletion of the density of the Kr 5p′[3/2]2 fluorescing state through photoionization (PIN) and amplified stimulated emission (ASE) is investigated. This is done by combining TALIF experiments with a simple 0D numerical model. We demonstrate that for a gas pressure of 3 mbar and 15 <I≤ 480 MW cm−2, a saturated fluorescence signal is obtained, which is largely attributed to PIN, ASE being negligible. Also, a broadening of the two-photon absorption line (i.e., 4p6 1S0 →→ 5p′[3/2]2) is recorded due to the production of charged species through PIN, inducing a Stark effect. For I ≤ 15 MW cm−2, though, PIN is significantly limited, the absorption line is noticeably narrowed, and the quadratic dependence of the TALIF signal intensity vs the laser energy is obtained. Thus, in this case, the investigated Kr TALIF scheme, using the 5p′[3/2]2 → 5s[3/2]1 fluorescence channel, can be used for calibration purposes in ps-TALIF experiments. These results are of interest for fundamental research since most ps-TALIF studies performed in Kr do not investigate in detail the role of PIN and ASE on the depletion of the Kr 5p′[3/2]2 state density. Moreover, this work contributes to the development of ps-TALIF for determining absolute densities and quenching coefficients of H and N atoms in plasmas. The use of ps-TALIF can allow sub-ns measurements of quenching rates that are necessary for absolute atomic densities determination in atmospheric pressure plasmas. Thus, the present study is linked to many experimental works focused on plasma physics and applications. In fact, the investigation of the application of ps-TALIF in Kr and the definition of regimes where the TALIF signal intensity scales quadratically with the laser energy is essential to calibrate H and N atom densities in reactive plasmas.

Low-threshold laser medium utilizing semiconductor nanoshell quantum dots.

Colloidal semiconductor nanocrystals (NCs) represent a promising class of nanomaterials for lasing applications. Currently, one of the key challenges facing the development of high-performance NC optical gain media lies in enhancing the lifetime of biexciton populations. This usually requires the employment of charge-delocalizing particle architectures, such as core/shell NCs, nanorods, and nanoplatelets. Here, we report on a two-dimensional nanoshell quantum dot (QD) morphology that enables a strong delocalization of photoinduced charges, leading to enhanced biexciton lifetimes and low lasing thresholds. A unique combination of a large exciton volume and a smoothed potential gradient across interfaces of the reported CdSbulk/CdSe/CdSshell (core/shell/shell) nanoshell QDs results in strong suppression of Auger processes, which was manifested in this work though the observation of stable amplified stimulated emission (ASE) at low pump fluences. An extensive charge delocalization in nanoshell QDs was confirmed by transient absorption measurements, showing that the presence of a bulk-size core in CdSbulk/CdSe/CdSshell QDs reduces exciton-exciton interactions. Overall, present findings demonstrate unique advantages of the nanoshell QD architecture as a promising optical gain medium in solid-state lighting and lasing applications.

Recent Advances on Amplified Stimulated Emission of Lead Halide Perovskite Micro/Nanostructures

Recent Advances on Amplified Stimulated Emission of Lead Halide Perovskite Micro/Nanostructures

1018 nm Yb-doped high-power fiber laser pumped by broadband pump sources around 915 nm with output power above 100 W.

We demonstrate a 1018nm ytterbium-doped all-fiber laser pumped by tunable pump sources operating in the broad absorption spectrum around 915nm. In the experiment, two different pump diodes were tested to pump over a wide spectrum ranging from 904 to 924nm by altering the cooling temperature of the pump diodes. Across this so-called pump wavelength regime having a 20nm wavelength span, the amplified stimulated emission (ASE) suppression of the resulting laser was generally around 35dB, showing good suppression ratio. Comparisons to the conventional 976nm-pumped 1018nm ytterbium-doped fiber laser were also addressed in this study. Finally, we have tested this system for high power experimentation and obtained 67% maximum optical-to-optical efficiency at an approximately 110W output power level. To the best of our knowledge, this is the first 1018nm ytterbium-doped all-fiber laser pumped by tunable pump sources around 915nm reported in detail.

Spectroscopic Study on Ultrafast Carrier Dynamics and Terahertz Amplified Stimulated Emission in Optically Pumped Graphene

This paper reviews recent advances in spectroscopic study on ultrafast carrier dynamics and terahertz (THz) stimulated emission in optically pumped graphene. The gapless and linear energy spectra of electrons and holes in graphene can lead to nontrivial features such as negative dynamic conductivity in the THz spectral range, which may lead to the development of new types of THz lasers. First, the non-equilibrium carrier relaxation/recombination dynamics is formulated to show how photoexcited carriers equilibrate their energy and temperature via carrier-carrier and carrier-phonon scatterings and in what photon energies and in what time duration the dynamic conductivity can take negative values as functions of temperature, pumping photon energy/intensity, and carrier relaxation rates. Second, we conduct time-domain spectroscopic studies using an optical pump and a terahertz probe with an optical probe technique at room temperature and show that graphene sheets amplify an incoming terahertz field. Two different types of samples are prepared for the measurement; one is an exfoliated monolayer graphene on SiO2/Si substrate and the other is a heteroepitaxially grown non-Bernal stacked multilayer graphene on a 3C-SiC/Si epi-wafer.

Method to correct the distortion caused by amplified stimulated emission as motivated by LIF-based flow diagnostics

Amplified stimulated emission (ASE) represents a significant issue in two-photon laser-induced fluorescence (TPLIF). The ASE effects are nonlinear and nonlocal, i.e., the ASE effects distort the LIF signal nonlinearly, and the distortion at one location depends on conditions at other locations. In this sense, the ASE effects pose a greater challenge to quantitative TPLIF than quenching and ionization. This work therefore seeks a method to correct such distortion. The method uses two LIF measurements, one with low signal-to-noise ratio (SNR) and negligible ASE distortion and another with high SNR but significant distortion, to generate a faithful measurement with high SNR. Extensive simulations were performed to evaluate the performance of this method for practical applications.

Highly Efficient Amplified Stimulated Emission from CdSe‐CdS‐ZnS Quantum Dot Doped Waveguides with Two‐Photon Infrared Optical Pumping

The process of two-photon optical pumping at 800 nm t, which allows for the generation of highly stable, amplified stimulated emission from a variety of CdSe-CdS-ZnS sized nanocyrstals was investigated. The process was found to be as efficient as conventional excitation mechanisms in the 1-photon excitation region. The CdSe cores were prepared by the method describe by Van Embden et al. The CdSe-CdS-ZnS quantum dots were prepared through adapted synthetic protocols of Li et al. A zinc rich surface was created to ensure the resulting nanoparticles,which possessed both high PL yield and photostability. The nanocrystal were rendered soluble in ethanol through 5-aminopentanol and tris-hydroxyphosphine surface exchange and further incorporated into Zirconia sol-gel matrix by using a protocol. The post synthesis of the nanocrystal surface chemistry was tailored to ensure homogenous nanocrystal, which incorporate into zirconia based waveguides.

Luminescence and Amplified Stimulated Emission in CdSe–ZnS‐Nanocrystal‐Doped TiO2 and ZrO2 Waveguides

AbstractA reproducible route for the preparation of high‐quality CdSe–ZnS‐doped titania and zirconia waveguides is presented. The optical properties of the resultant composite materials are found to be sensitive to the semiconducting properties of the host matrix. Titania‐based composites are seen to be inherently photounstable because of photoelectron injection into the bulk matrix and subsequent nanocrystal (NC) oxidation. In comparison, zirconia composites are significantly more robust with high photoluminescence (PL) retained for annealing temperatures up to 300 °C. Both titania and zirconia composite waveguides exhibit amplified stimulated emission (ASE); however only zirconia‐based waveguides exhibit long‐term photostability (loss of less than 30 % ASE intensity after more than 40 min continuous excitation). We conclude that the low electron affinity of zirconia and its inherent high refractive index makes it an ideal candidate for NC‐based optical waveguides.

Dynamics of cavityless lasing generated by ultrafast multiphoton excitation

A dynamical theory is developed with the purpose of explaining recent experimental results on multiphoton-excited amplified stimulated emission (ASE). Several conspicuous features of this experiment are analyzed, like the threshold dependence of the spectral profile on the pump intensity, and spectral shifts of the ASE pulses co- and counterpropagating relative to the pump pulse. Two models are proposed and evaluated, one based on the isolated molecule and another which involves solvent interaction. The spectral shift between the forward and backward ASE pulses arises in the first model through the competition between the ASE transitions from the pumped vibrational levels and from the bottom of the excited-state well, while in the solvent-related model the dynamical solute-solvent interaction leads to a relaxed excited state, producing an additional ASE channel. In the latter model the additional redshifted ASE channel makes the dynamics of ASE essentially different from that in the molecular model because the formation of the relaxed state takes a longer time. The variation of the pump intensity influences strongly the relative intensities of the different ASE channels and, hence, the spectral shape of ASE in both models. The regime of ASE changes character when the pump intensity crosses a threshold value. Such a phase transition occurs when the ASE rate approaches the rate of vibrational relaxation or the rate of solute-solvent relaxation in the first excited state.

Inherently gain flattened L+ band TDFA based on W-fiber design

We present here a detailed theoretical analysis for realizing an inherently gain flattened L+ band thulium doped fiber amplifier (TDFA), based on a depressed inner-clad (W-fiber) design, wherein the inherent gain flattening is achieved by an optimized bend induced leakage loss. The leakage loss characteristics of W-fiber have been used to suppress higher wavelength amplified stimulated emission (ASE) in the designed TDFA, which otherwise depletes the population inversion in the amplifier, making it almost impossible to obtain high gain for wavelengths in and close to the conventional L-band. It has been shown through simulations that 20dB net gain (±0.3dB ripple) is achievable over 32nm bandwidth (1604–1636nm), using this design pumped with 160mW of power. We also show that inherent gain flattening leads to redistribution of power among signal wavelengths, and hence an inherently gain-flattened TDFA is much more efficient as compared to a configuration that uses discrete filters for gain flattening. The net gain value and gain flattening of the designed TDFA module have been tested against tolerance with respect to fiber parameters as well as bend radius. This is for the first time to the authors knowledge that inherently gain flattened L+ band operation has been shown using TDFAs.

Random laser action in organic film during the photopolymerization process

We report on transient laser action during the photopolymerization process in organic thin films of acrylate monomers doped with a laser dye. The emission spectrum was monitored over a period of time in the direction orthogonal to the incident laser beam which is kept at a constant intensity during the experiments. The emission spectra display the signature of laser action after a certain amount of polymerization. We have also recorded the intensity of fluorescence as well as of the amplified stimulated emission (ASE) using a photodiode. Our results confirmed that all the emission is guided by an increase of the refractive index resulting from the photopolymerization process. The spatial fluctuations in the density of the material are thought to act as micro-cavities leading to a random laser effect.

Backscattering-induced crosstalk in WDM optical wireless communication

The crosstalk effect of aerosol backscatter on the performance of a wavelength-division-multiplexed (WDM) optical wireless communication (OWC) system is investigated, analyzed, and quantified. An OWC link could be a segment within a metropolitan area network (MAN) or a ground-station-to-space link of a satellite communication system. In these cases, a WDM transmitter and receiver are housed in one transceiver unit with parallel, or near-parallel, optic axes. The crosstalk at the receiver is caused by light from the transmitted signal of the same transceiver, which has been backscattered by molecules and aerosols in the atmosphere. This is exacerbated in the presence of fog and haze, in which case both the desired signal from another transceiver is attenuated by scattering and the backscatter-induced crosstalk increases. A bit-error-rate (BER) model is derived that takes into consideration the dominant noise sources, including backscatter-induced crosstalk and signal mixing with amplified stimulated emission (ASE) from an optical preamplifier at the receiver. The numerical calculations in this paper indicate that, in moderate fog, the BER may increase by an order of magnitude or more due to backscatter, depending upon the atmospheric extinction coefficient.

ASE and photodegradation of two benzimidazole derivatives proton transfer dyes in polymeric matrices

Abstract We report the preparation and spectral characteristics of solid polymeric hosts doped with proton-transfer dyes 2-(2′-hydroxyphenyl)benzimidazole (HPBI) and 2-(2′-hydroxy-5′-chlorphenyl)benzimidazole (Cl-HPBI). The material shows amplified stimulated emission (ASE) under 337 nm pulse excitation. In comparing with PMMA, PS and a 1:1 PS/PMMA copolymer as host material the latter shows improved properties relating to efficiency and photo stability. For all samples we observed a shortening in ASE pulse width during emission due to photo degradation.

Observation of ASE effect for Ne-like Ar in a capillary discharge driven by inductive storage with plasma erosion opening switch

Inductive storage with plasma erosion opening switch was used as a current driver for capillary discharge. A discharge current of 40-50 kA was reached with current time derivative higher than 10 12 A/sec. At the moment 50 - 60 nsec from beginning of a discharge time gated off-axis VUV imaging of a plasma has shown an appearance of a bright spot corresponding to the position of a center of a far end of a capillary. Simultaneously an enhanced intensity of 469 A line of 3p-3s transition of Ar IX was detected. We consider these observations as a proof of an effect of amplified stimulated emission (ASE).

Long-wavelength erbium-doped fiber amplifier gain enhanced by ASE end-reflectors

We use for what we believe is the first time narrow-band end-reflectors to reduce losses through short-wavelength amplified stimulated emission (ASE) in silica-based erbium-doped fiber amplifiers operating at wavelengths above 1570 mm. The end-reflectors feed a small fraction of the ASE, up to a few tenths of a milliwatt, back into the amplifying fiber. The reflected ASE compresses the short-wavelength gain and thus reduces the ASE-losses, from, e,g., 50 mW for a launched pump power of 110 mW at 980 nm without end-reflector to 10 mW with an optimized end-reflector. We investigate possible improvements of gain (around 5 dB) and output power (up to 17 mW), and the influence of the amount and wavelength of the feedback.

Electron Transfer, Solvation, and Amplified Stimulated Emission of Pyrene-DMA and Anthracene-DMA

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron Transfer, Solvation, and Amplified Stimulated Emission of Pyrene-DMA and Anthracene-DMAA. Wiessner, G. Huettmann, W. Kuehnle, and H. StaerkCite this: J. Phys. Chem. 1995, 99, 41, 14923–14930Publication Date (Print):October 1, 1995Publication History Published online1 May 2002Published inissue 1 October 1995https://doi.org/10.1021/j100041a005RIGHTS & PERMISSIONSArticle Views316Altmetric-Citations57LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

High-pressure amplified stimulated emission effect in a N2 laser produced plasma with axicon lenses

An axicon is used to focus a CO2-TEA laser pulse in a high pressure preionized mixture of He-N2. An amplified stimulated emission (ASE) effect at 337.1 nm (N2) is obtained. The dependence of inversion population on the electron density is shown. Also presented is the electron temperature as a function of the CO2 pulse intensity for different mixtures of He-N2.