Optical NIR Research Articles

Bi Cluster Engineering for Tunable Broadband NIR Optical Response

AbstractNear‐infrared (NIR) broadband active photonic materials play a crucial role in various domains such as optical communication, phototherapy, and medical imaging. However, the construction of NIR photonic materials with tunable optical response still remains a great challenge. This manuscript proposes a topological structure engineering strategy in Bi‐activated glass for the realization of the controllable NIR emission. By manipulating the topological structure of glass, the Bi cluster configuration can be precisely control, with the cluster size from 2.78 to 1.64 nm. Correspondingly, various optical properties including broadband emission, excited state absorption (ESA), and even unsaturable loss (UL) can be rationally switched. Based on the above findings, Bi cluster‐activated bulk glasses, optical fibers, and the derived NIR active devices with notably improved performance can be successfully fabricated. Their application potentials in optical communication and NIR imaging are also demonstrated. The study highlights the promise of Bi cluster‐activated materials in advancing NIR photonic materials and devices. Furthermore, the topological‐mediated cluster regulation strategy may also provide new insights into the fundamental science and cutting technology of other cluster‐activated materials.

Erbium-Ion-Doped Bismuth Borate Glasses for High Optical Gain NIR Fiber Laser Applications

The study focused on investigating the thermal, structural, and luminescent properties of bismuth borate glasses doped with erbium (Er3+) ions and modified with Gd2O3, K2O, and Li2O (BBGKL: Erx) aiming for fiber lasers. Two glass transition temperatures were observed at 381 (Tg1) and 471 K (Tg2) for BBGKL glass. O1s de-convolution spectrum bridging oxygens for BBGKL glass, including B-O, Bi-O, Li2O, and K2O, were discovered by XPS. Both the photoluminescence (PL) 4I13/2→4I15/2 NIR and the absorption bands from the UV-visible-NIR spectrum were found to occur at 1531 nm for BBGKL: Er. The luminescence quenching was not noticed up to 3.0 mol% of Er3+ ion concentration. The BBGKL: Er0.5 glass has a remarkable connection between its absorbance and emission cross-sections of 0.77 and 0.82 × 10−20 cm2, respectively. The longest lifetime of green emission for the 4S3/2→4I15/2 transition was found for BBGKL: Er2.0 glass at 10.6 μs and 1531 nm NIR emission for the 4I13/2→4I15/2 transition of BBGKL: Er0.5 glass was 0.77 ms. In the 1413–1728 nm NIR band region for BBGKL:Er3.0, high optical gain cross-section G(λ) was promising for the population inversion at γ = 0.6. These findings suggested that the BBGKL: Er0.5 glass would prove helpful in NIR fiber laser applications.

Optical properties and NIR Photoluminescence of Dy3+ doped CdS Q-dots dispersed in borosilicate glass for biophotonics applications

We synthesised CdS Q-dots and Dy3+ doped CdS Q-dots dispersed in borosilicate glasses and evaluated their optical and NIR photoluminescence properties. When excited with an 800nm source, new strong photoluminescence emissions from 850 to 1150 nm were observed in the NIR are reported. These new find states may be attributed to NIR virtual or trap states of the CdS S-Qdot. The strong photoluminescence emission spectrum observed from 850 to 950 nm corresponds to electron–hole recombination for as-prepared CdS-Q-dot glasses. However, this photoluminescence emission disappeared upon heat treatment due to photoluminescence emission from defect states.

Structural and spectroscopic studies of Er3+ in different fluorophosphate glasses for green laser and fibre amplifier operations

Erbium activated fluorophosphate glasses were synthesized with conceived characteristic combination, 59.5NH4H2PO4+15ZnO+15BaF2+10X+0.5Er2O3(X = LiF, NaF, CaF2, SrF2, AlF3) by melt quenching route. Based on the mass densities, and refractive indices, other physical properties i.e., dielectric constant (ε), reflection losses, molar refraction, internuclear distance and molar volume are determined. XRD has confirmed the non-crystalline character of the prepared glass samples. FTIR, FT-Raman have been employed to study the structural characteristics. Various radiative properties have been inferred through optical absorption measurements by standard Judd–Ofelt procedure. By excitation at 379 nm, all the glass hosts doped with constant concentration 0.5 mole% of Er3+have yielded intense green emission peak due to the transition 4S3/2 → 4I15/2 at 545 nm. Characteristic emission transition 4I13/2 → 4I15/2 at wavelength 1.53 μm has been studied extensively. Particularly the parameters related to that transition namely, stimulated emission cross-sections (σ e) and optical gains (G) are calculated from emission spectra. Among all the fluorophosphate glasses, the one which has shown higher σ e, and G values is sodium fluorophosphate (NFPE) glass. It is recommended for optical fiber amplification and NIR laser usage.

Optical Helicity and Polarization Dependent NIR Negative Photocurrent in the 2D Magnetic Semiconductor CrI3

AbstractTwo‐dimensional magnetic semiconductors provide a fascinating platform for studying magneto‐optoelectronic properties at the atomically thin limit and have potential in developing novel devices. In this paper, the superior negative photoconductivity (NPC) characteristics of graphene‐CrI3‐graphene van der Waals heterostructure in light detection, such as a broader detection range (650–1250 nm) and faster response time (<0.32 ms), as well as light helicity and polarization sensitivity are reported. Under near‐infrared (NIR) light illumination, the NPC‐related photoresponsivity R and specific detectivity D* are 1.18 A W−1 and 1.26 × 109 Jones, respectively. Under magnetic field conditions, the NPC and positive photoconductivity (PPC) show opposite optical helicity dependence. The photoresponsivity helicity of the NPC‐dominated photocurrent can reach 16.01%. Besides, NPC and PPC show obvious and similar linear polarization dependence, independent of magnetic fields. It is demonstrated that NPC is superior to PPC in some aspects, such as fast detection of red and NIR lights as well as their helicity and polarization, especially in the NIR region. This work explores many unique phenomena of NPC, further revealing the interplay between magnetic and optoelectronic properties in CrI3, and paves the way for expanding traditional photoelectric detection and optical communication with higher data transmission rates.

OPTICAL BASED NON INVASIVE GLUCOMETER WITH IOT

Diabetes mellitus (DM) nicknamed as sugar is becoming one of incurable and critical challenge to medical field. Serious illness such as premature mortality even cause of death, which can be identified by continuous monitoring from a remote location. The traditional and conventional method such as finger pricking's demerits such as pain and damage to tissues that cause infection. Such type of infections can be overcome by non-invasive technique. The objective of this paper is to monitor glucose level using non-invasive technique by optical and IoT technology. The proposed sensor circuit consists of IR LED's of wavelength 650–2500nm for optical blood glucose measurement and NIR photodiodes (InGaAs) to receive the reflected light from body parts to determine the glucose level. The Beer-Lambert law is used for signal processing along with WIFI based IoT real time information transmission. The project is implemented using Arduino IDE for finding the performance matrix of the system as well as various analytical studies. With the rapid development of wearable technology and transdermal biosensors, non-invasive blood glucose monitoring will become more efficient, affordable, robust, and more competitive on the market. Key Words: Diabetes mellitus, blood glucose measurement, WIFI based IoT, wearable technology

Constraining the SN Ia host galaxy dust law distribution and mass step: hierarchical BayeSN analysis of optical and near-infrared light curves

ABSTRACT We use the BayeSN hierarchical probabilistic SED model to analyse the optical–NIR (BVriYJH) light curves of 86 Type Ia supernovae (SNe Ia) from the Carnegie Supernova Project to investigate the SN Ia host galaxy dust law distribution and correlations between SN Ia Hubble residuals and host mass. Our Bayesian analysis simultaneously constrains the mass step and dust RV population distribution by leveraging optical–NIR colour information. We demonstrate how a simplistic analysis where individual RV values are first estimated for each SN separately, and then the sample variance of these point estimates is computed, overestimates the RV population variance $\sigma _R^2$. This bias is exacerbated when neglecting residual intrinsic colour variation beyond that due to light curve shape. Instead, Bayesian shrinkage estimates of σR are more accurate, with fully hierarchical analysis of the light curves being ideal. For the 75 SNe with low-to-moderate reddening (peak apparent B − V ≤ 0.3), we estimate an RV distribution with population mean μR = 2.59 ± 0.14, and standard deviation σR = 0.62 ± 0.16. Splitting this subsample at the median host galaxy mass (1010.57 M⊙) yields consistent estimated RV distributions between low- and high-mass galaxies, with μR = 2.79 ± 0.18, σR = 0.42 ± 0.24, and μR = 2.35 ± 0.27, σR = 0.74 ± 0.36, respectively. When estimating distances from the full optical–NIR light curves while marginalizing over various forms of the dust RV distribution, a mass step of ≳0.06 mag persists in the Hubble residuals at the median host mass.

Near-infrared photoluminescence studies of neodymium ions doped SrO-Al2O3-BaCl2-B2O3-TeO2 glasses for laser and fiber amplifier applications

This paper reports, preparation and characterization of Neodymium (Nd3+) ions doped Oxy Chloro Boro Tellurite (OCBT) glasses. The influence of Nd3+ ions concentration on physical, absorption, emission, and decay properties of OCBT glasses were studied in detailed using spectroscopic techniques. The experimental oscillator strengths measured from the absorption spectral data were subjected for Judd-Oflet (JO) analysis to estimate the best fit JO parametes and the dependent radiative properties of the as prepared glasses. The photoluminescence (PL) spectra recorded under 824 nm laser diode excitation reveal three emission peaks positioned at 887, 1064 and 1340 nm pertaining to 4F3/2→4I9/2, 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions respectively. Correlation of radiative parameters information with PL spectral data allows to estimate various lasing parameters like emission cross section (σsec), gain bandwidth (σsec×ΔλP) and optical gain (σsec×τR). The PL decay spectra recorded for the as prepared glasses for 4F3/2→4I11/2 intense emission transition (observed at 1064 nm) reveal single exponential nature. The experimental lifetimes (τexp) measured from the PL decay profiles are correlated with the radiative lifetimes (τR) measured from the JO analysis to estimate quantum efficiency (η%) of the titled glasses. Among all the as prepared OCBTNd samples, 1 mol% of Nd3+ ions doped OCBTglass sample flourishes highest quantum efficiency. From the productive results obtained, it can be suggested that OCBTNd1.0 glass grabs plenty of applications in solid state lasers technology, fabrication of optical fiber amplifiers and NIR laser applications.

Looking for Obscured Young Star Clusters in NGC 1313

Abstract Using recently acquired Hubble Space Telescope NIR observations (J, Paβ, and H bands) of the nearby galaxy NGC 1313, we investigate the timescales required by a young star cluster to emerge from its natal cloud. We search for extincted star clusters, potentially embedded in their natal cloud as either (1) compact sources in regions with high Hα/Paβ extinctions or (2) compact H ii regions that appear as point-like sources in the Paβ emission map. The NUV–optical–NIR photometry of the candidate clusters is used to derive their ages, masses, and extinctions via a least-χ 2 spectral energy distribution broad- and narrowband fitting process. The 100 clusters in the final samples have masses in the range and moderate extinctions, E(B − V) ≲ 1.0 mag. Focusing on the young clusters (0–6 Myr), we derive a weak correlation between extinction and age of the clusters. Almost half of the clusters have low extinctions, E(B − V) < 0.25 mag, already at very young ages (≤3 Myr), suggesting that dust is quickly removed from clusters. A stronger correlation is found between the morphology of the nebular emission (compact, partial or absent, both in Hα and Paβ) and cluster age. Relative fractions of clusters associated with a specific nebular morphology are used to estimate the typical timescales for clearing the natal gas cloud, resulting in between 3 and 5 Myr, ∼1 Myr older than what was estimated from NUV–optical-based cluster studies. This difference hints at a bias for optical-only-based studies, which James Webb Space Telescope will address in the coming years.

Energy transfer induced enhancement in NIR luminescence characteristics of Yb3+/Er3+ co-doped sodium zinc bismuth fluorophosphate glasses

The results pertaining to the energy transfer-based photoluminescence characteristics of Er3+-doped and Yb3+/Er3+ co-doped NaF–ZnO–BiF3–NH4H2PO4 (NZBFP) glasses prepared through melt-quench technique were demonstrated here. By applying McCumber's theory, the absorption, stimulated emission cross-sections and optical gain have been estimated for Yb3+ (0.97 μm) and Er3+ (1.54 μm) ions. Yb3+-doped glass exhibited a sharp emission at 979 nm at 808 nm excitation while Er3+-doped glass displayed a broad NIR emission band at/around 1545 nm for 980 nm excitation. The presence of Yb3+ absorption band along with the Er3+ absorption bands in the co-doped glass suggests the energy transfer (ET) possibility within these ions. On pumping Er3+-doped &yYb3+/Er3+ co-doped NZBFP glasses with 980 nm Laser Diode, a broad Er3+ emission at 1545 nm attributed to 4I13/2 → 4I15/2 is observed in the NIR region. The increasing of Yb3+concentration with respect to Er3+ (fixed to 1 mol%) in co-doped glasses have resulted in enhancement of Er3+ NIR emission because of the resonant energy transfer (ET) process from Yb3+→Er3+. The energy transfer (ET) mechanism has been illustrated from the spectral overlap of Yb3+ emission and Er3+ absorption, Er3+ decay lifetime curves, and partial energy level diagram. Further, the nature of interaction responsible for the energy transfer process (ET) has been explained using Forster-Dexter theory and I–H fitting. In addition, the suitability of the present synthesized fluorophosphate glasses for optical amplifier and NIR laser applications were explored in terms of optical amplification and gain parameters, like effective band-width (Δλeff), stimulated emission cross-section (σe), optical gain (G), and gain bandwidth (ΔG).

Stellar population properties of individual massive early-type galaxies at 1.4 < z < 2

ABSTRACT We analyse publicly available, individual spectra of four massive ($M\gt 10^{11}\, \mathrm{M}_{\odot }$) early-type galaxies with redshifts in the range 1.4 ≤ z ≤ 2 to determine their stellar content, extending our previous work up to z ∼ 2. The wide wavelength range of the VLT/X-Shooter spectroscopic data in the UV–Optical–NIR arms along with the availability of spectro-photometry allows us to explore different techniques to obtain the stellar population properties, namely through age/metallicity-sensitive spectral indices, full spectral fitting, and broad-band photometric fitting. Moreover, together with the widely used optical Lick indices, we consider further indices in the UV rest frame, and demonstrate that UV indices significantly help the accuracy of the resulting population parameters. We find galaxy ages ranging from 0.2 to 4 Gyr, where the oldest galaxy is found at the lowest redshift, with an excellent agreement between ages determined via indices, full spectral fitting, or broad-band colours. These ages are in perfect agreement with ages of local galaxies at the same velocity dispersion when we assume pure passive evolution. Total metallicities derived from indices show some scatter (between less than half-solar to very high values, [Z/H] ∼ 0.6). We speculate on possible mechanisms explaining these values, but given the sample size and low S/N of the spectra no conclusion can be made. Indices in the UV rest frame generally lead to similar conclusions as optical indices. For the oldest galaxy (4 Gyr), we show that its UV indices can only be explained by stellar population models including a UV contribution from old stellar populations, suggesting that old, UV bright populations start to inhabit mature galaxies of a few Gyr of age. This is the highest redshift (z ∼ 1.4) detection of the UV upturn up to date.

Investigations on the physical, structural, optical and photoluminescence behavior of Er3+ ions in lithium zinc fluoroborate glass system

Family of lithium zinc fluoroborate glasses with 15ZnF2-10BaO-8Al2O3–12Li2O-(55-x) B2O3-xEr2O3 (x = 0.5, 0.7, 1.1, 1.3 and 1.5 mol%) composition were prepared by conventional melt-quench method. The glasses were characterized to study their structural, physical, optical and radiative properties. The amorphous characteristic of glass was noticed in X-Ray Diffraction pattern. A modification in structure was observed as density values increased with Er2O3 content. UV–Vis–NIR transitions of Er3+ in the host matrix were identified through absorption spectra. Covalent nature of bonding between Er3+ ions and their surrounding ligands was observed through bonding parameter and Judd-Ofelt parameters. Red shift of the fundamental absorption edge in the absorption spectra and decreasing indirect and direct band gaps with increasing Er3+ concentration jointly confirmed the role of Er3+ ions as network modifier. Hypersensitive transitions of Er3+ ion namely 4I15/2 → 2H11/2 &4I15/2 → 4G11/2 were interpreted through their higher oscillator strengths when compared to other transitions. Emission spectra recorded at 980 nm excitation showed a peak corresponding to 4I13/2 → 4I15/2 NIR transition of erbium ion. Stimulated emission cross section of Er0.5 sample, gain bandwidth and Figure of Merit were found to be 16.79 × 10−21 cm2, 1225.83 × 10−28 cm3 and 37.36 × 10−24 cm2 s respectively. Photoluminescence decay curve of Er0.5 sample was well-fitted to single exponential first order function. The experimental decay lifetime τexp for the 4I13/2 level was measured to be 0.34 ms. The wide frequency range of FWHM (1.02–1.67 × 1013 Hz) and high values of radiative parameters make the glass a suitable candidate as optical amplifier and NIR laser material.

Assessment of polyethylene degradation after aging through anaerobic digestion and composting

Impurities in bio-waste enter biogas and compost facilities during bio-waste treatment. The plastic fraction is usually separated and sent for incineration. This study is aimed at evaluating the quality of low density polyethylene after being exposed to anaerobic digestion, composting or both processes sequentially, in order to assess for the optimum post-processing of these plastic fractions, eventually undergoing recycling processes. The alteration in the polymer's quality was first analyzed by non-destructive optical methods, including FTIR, NIR, SEM and EDX. These tests were followed by thermal and mechanical properties' assessment.The surface of the specimens showed signs of degradation, yet the extent of the changes was microscopic. The FTIR and NIR spectra showed higher intensities for C-H bonds in treated samples, which might be an indication of shorter polymer's chain length and/or higher chain scissoring. FTIR showed weak transmission spectral changes at regions representing C-O and O-H bonds for anaerobically digested and sequentially anaerobically digested and composted samples, indicating the existence of oxidized products, which was confirmed by the EDX analysis, where slightly higher oxygen content on the surface of specimens underwent the anaerobic digestion process was observed. However, NIR spectra did not show conforming spectra. It was accordingly concluded that the oxidized products are contaminants (residues on the specimens' surfaces), which was as well confirmed by the DSC analysis. The thermal analysis indicated a decrease in the polymer's crystallinity after being treated, where the decrease effect was the highest by anaerobic digestion, however, the mechanical properties (including tensile strength, elastic modulus and strain at break) pointed out minor quality alteration in treated samples, especially for samples underwent both processes successively. Based on the provided assessment, the general properties of LDPE plastic specimens are acceptable to be recycled, even after undergoing accelerated aging conditions, such as anaerobic digestion and composting. Further analyses are needed to evaluate plastics with additives as well as bags and films.

P066] History of medical physics – A project tracing the development of the profession

Purpose The International Organization for Medical Physics (IOMP) exists over 50 years. It collects information from all medical physics societies, thus collating a picture of the professional global development. While during the mid-1960 there were c.6000 medical physicists in the world, in 2017 these are c.26,000. However there is a huge challenge in front of the profession. The recently published report of the Global Task Force on Radiotherapy for Cancer Control predicts that by 2035 the existing number of medical physicists has to triple in order to support the needs of the global healthcare provision. The lessons from the past 20 years show that to achieve such goal the profession has to firmly invest in education and training activities, with special emphasis on e-learning and international collaboration. In order to support this global effort of the profession, IOMP launched a new project “History of Medical Physics”, which will trace the professional development in various countries, showing specific models which could be useful for other countries. Methods This large international project will not only focus on the medical physics professional development. It will also show the development of the various branches in our profession. This way the project will create a Compendium of independent Volumes/Parts, which will reflect the main areas of development of medical physics, including: Diagnostic Radiology (X-ray) Imaging; Computed Tomography; Radiotherapy (External beam); Radiotherapy (Brachytherapy); Nuclear Medicine Imaging; Ultrasound Imaging; Magnetic Resonance Imaging; Optical Systems and NIR in Medicine; Medical Informatics; Radiation Measurement and Protection in Medicine; Professional Development; EducationT EducationT Diagnostic Radiology (X-ray) Imaging. These will be presented at ECMP together with their outcomes, aiming to expand the project and invite more colleagues from EFOMP to take part in this unique international activity. Conclusions The project results will be a very useful source of information for future new developments and will provide a canvas for future updates. Very importantly, the project results will be a written proof of the significant role played by medical physicists in contemporary medicine.

On the Use of the Main-sequence Knee (Saddle) to Measure Globular Cluster Ages

Abstract In this paper, we review the operational definition of the so-called main-sequence knee (MS-knee), a feature in the color-magnitude diagram (CMD) occurring at the low-mass end of the MS. The magnitude of this feature is predicted to be independent of age at fixed chemical composition. For this reason, its difference in magnitude with respect to the MS turn-off (MS-TO) point has been suggested as a possible diagnostic to estimate absolute globular cluster (GC) ages. We first demonstrate that the operational definition of the MS-knee currently adopted in the literature refers to the inflection point of the MS (which we here more appropriately named MS-saddle), a feature that is well distinct from the knee and which cannot be used as its proxy. The MS-knee is only visible in near-infrared CMDs, while the MS-saddle can be also detected in optical–NIR CMDs. By using different sets of isochrones, we then demonstrate that the absolute magnitude of the MS-knee varies by a few tenths of a dex from one model to another, thus showing that at the moment stellar models may not capture the full systematic error in the method. We also demonstrate that while the absolute magnitude of the MS-saddle is almost coincident in different models, it has a systematic dependence on the adopted color combinations which is not predicted by stellar models. Hence, it cannot be used as a reliable reference for absolute age determination. Moreover, when statistical and systematic uncertainties are properly taken into account, the difference in magnitude between the MS-TO and the MS-saddle does not provide absolute ages with better accuracy than other methods like the MS-fitting.

RATIR Follow-up of LIGO/Virgo Gravitational Wave Events

Abstract We have recently witnessed the first multi-messenger detection of colliding neutron stars through gravitational waves (GWs) and electromagnetic (EM) waves (GW 170817) thanks to the joint efforts of LIGO/Virgo and Space/Ground-based telescopes. In this paper, we report on the RATIR follow-up observation strategies and show the results for the trigger G194575. This trigger is not of astrophysical interest; however, it is of great interest to the robust design of a follow-up engine to explore large sky-error regions. We discuss the development of an image-subtraction pipeline for the six-color, optical/NIR imaging camera RATIR. Considering a two-band (i and r) campaign in the fall of 2015, we find that the requirement of simultaneous detection in both bands leads to a factor ∼10 reduction in false alarm rate, which can be further reduced using additional bands. We also show that the performance of our proposed algorithm is robust to fluctuating observing conditions, maintaining a low false alarm rate with a modest decrease in system efficiency that can be overcome utilizing repeat visits. Expanding our pipeline to search for either optical or NIR detections (three or more bands), considering separately the optical riZ and NIR YJH bands, should result in a false alarm rate ≈1% and an efficiency ≈90%. RATIR’s simultaneous optical/NIR observations are expected to yield about one candidate transient in the vast 100 deg2 LIGO error region for prioritized follow-up with larger aperture telescopes.

Metal-rich, Metal-poor: Updated Stellar Population Models for Old Stellar Systems

Abstract We present updated stellar population models appropriate for old ages (>1 Gyr) and covering a wide range in metallicities (−1.5 ≲ [Fe/H] ≲ 0.3). These models predict the full spectral variation associated with individual element abundance variation as a function of metallicity and age. The models span the optical–NIR wavelength range (0.37–2.4 μm), include a range of initial mass functions, and contain the flexibility to vary 18 individual elements including C, N, O, Mg, Si, Ca, Ti, and Fe. To test the fidelity of the models, we fit them to integrated light optical spectra of 41 Galactic globular clusters (GCs). The value of testing models against GCs is that their ages, metallicities, and detailed abundance patterns have been derived from the Hertzsprung–Russell diagram in combination with high-resolution spectroscopy of individual stars. We determine stellar population parameters from fits to all wavelengths simultaneously (“full spectrum fitting”), and demonstrate explicitly with mock tests that this approach produces smaller uncertainties at fixed signal-to-noise ratio than fitting a standard set of 14 line indices. Comparison of our integrated-light results to literature values reveals good agreement in metallicity, [Fe/H]. When restricting to GCs without prominent blue horizontal branch populations, we also find good agreement with literature values for ages, [Mg/Fe], [Si/Fe], and [Ti/Fe].

Investigation of Green and 1.53 μm emission characteristics of Er3+ doped bismuth phosphate glasses for laser applications

Erbium (Er3+) ion doped bismuth phosphate (BiP) glasses were fabricated by melt quenching technique. In the current project, studied the influence of bismuth content and Er3+ ion doping concentration on photoluminescence (PL) performance and therefore find out the most qualified combination of bismuth and Er3+ for developing compact optical fibre lasers and amplifiers operating at 1.53 μm. Optical absorption measurements are carried out and analysed through Judd-Ofelt (JO) and Mc-Cumber theories from which JO parameters, absorption and stimulated emission cross-sections are determined. The studied glasses show intense and broad visible emission at 545 nm (green) for 4S3/2 → 4I15/2 transition with the excitation 379 nm might be useful for green laser applications. The luminescence behaviour of 4I13/2 → 4I15/2 transition in the wavelength region 1400–1700 nm and its suitability for optical amplifier applications and also for NIR laser have been discussed with parameters such as stimulated emission cross-section (σe), gain bandwidth (ΔG) and optical gain (G). The decay curves for both 4S3/2 (visible) and 4I13/2 (NIR) levels are discussed and they are exhibiting non-exponential nature for all the studied BiP glasses. Among all the BiP glasses, Er-1.0 glass exhibited higher σe, ΔG and G values suggesting the suitability for optical amplifier and NIR laser applications.

Investigations on structural and luminescence behavior of Er3 + doped Lithium Zinc borate glasses for lasers and optical amplifier applications

Trivalent Erbium doped Lithium Zinc borate glasses were prepared with the chemical composition (55–x)H3BO3+20Li2CO3+20ZnO+5LiF+xEr2O3 (where x=0.01, 0.05, 0.1, 0.5, 1.0 and 2.0mol%) following the melt quenching technique. The different BO vibrational bands and the change in coordination number of the boron with the addition of Er3+ ions in the prepared glasses were analyzed through FTIR and Raman spectra. The decreasing ionic nature was confirmed through Nephelauxetic ratios (β) and bonding parameter values (δ) from the absorption spectral measurements. The oscillator strengths and Judd-Ofelt parameters (Ω2, Ω4, Ω6) were calculated on the basis of Judd-Ofelt theory. The dependency of Ω2 parameter on the oscillator strengths of the hypersensitive transition has been studied. The radiative parameters such as transition probability (A), branching ratio (βR) and radiative lifetime (τ) which characterizes the luminescence behavior were determined from the JO parameters and refractive index values. The luminescence from the thermally coupled energy level 2H11/2+4S3/2→4I15/2 was observed under 379nm excitation and is inhomogeneously broadened (Δλeff=14nm) due to the structural disorder in the prepared glasses. The stimulated emission cross-section corresponding to the 4S3/2→4I15/2 transition is found to be higher for the LZB0.5E glass compared to the other reported literature thus it is suggested for suitable green laser applications. The luminescence behavior in the wavelength region 1400–1700nm corresponding to the 4I13/2→4I15/2 transition at 980nm excitation was also observed and its suitability for optical amplifier applications and NIR laser have been discussed with parameters such as optical gain bandwidth (ΔG), Figure of Merit (FOM) and stimulated emission cross-section (σe). Of all the studied glasses, LZB0.5E glass possesses higher values of ΔG=613.8×10−28cm3, FOM=40.9×10−24cm2s and σe=93×10−22cm2 compared to the reported literature thus suggesting its suitability for optical amplifier and NIR laser applications.

CHANDRA COUNTERPARTS OF CANDELS GOODS-S SOURCES

ABSTRACT Improving the capabilities of detecting faint X-ray sources is fundamental for increasing the statistics on faint high-z active galactic nuclei (AGNs) and star-forming galaxies (SFGs). We performed a simultaneous maximum likelihood point-spread function fit in the [0.5–2] keV and [2–7] keV energy bands of the 4 Ms Chandra Deep Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected galaxies. For each detected source we provide X-ray photometry and optical counterpart validation. We validated this technique by means of a ray-tracing simulation. We detected a total of 698 X-ray point sources with a likelihood (i.e., >2.7σ). We show that prior knowledge of a deep sample of optical–NIR galaxies leads to a significant increase in the detection of faint (i.e., ∼10−17 cgs in the [0.5–2] keV band) sources with respect to “blind” X-ray detections. By including previous X-ray catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. Our results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the new detected sources are likely SFGs or faint, absorbed AGNs. We identified a few sources with putative photometric redshift z > 4. Despite the low number statistics and the uncertainties on the photo z, this sample significantly increases the number of X-ray-selected candidate high-z AGNs.