Optical results concerning the generation of laser and optical gain by using an Er3+-doped tellurite
micro-structured fiber are reported for the first time. For this purpose a scheme that consist of two 980 nm
diode pump lasers (simultaneously in the co-propagating and the counter-propagating directions) and short
Er3+-doped tellurite micro-structured fibers (fabricated by using the stack-and-draw technique and a soft glass
drawing tower) was used. The laser produced here was obtained within the range 1530 to 1565 nm, and the
maximum optical gain obtained was higher than 8 dB.
We report the fabrication of PbTe quantum dots grown under inert gas (Ar and He) atmosphere by
pulsed laser deposition using the second harmonic of a Q-Switched Quantel Nd:YAG laser. For
characterization, samples were prepared onto a 40Å carbon film deposited on a copper grid. The
influence of background pressure, and number of laser pulses on the size distribution of the PbTe
nanoparticles was investigated by transmission electron microscopy using a 200 kV TECNAI G2
F20 electron microscope with 0.27 nm point resolution. The size distribution was obtained by
manually outlining the particles from several dozens of low- and high-resolution TEM images. Once
digitized and saved in a proper format, the image was processed using the J-image software.
Characterizations reveal an increase of the nanoparticle size both with the amount of material
deposited (number of laser pulses) and the background pressure. Furthermore, measurements reveal
a narrower nanoparticle size distribution by increasing the number of laser pulses or by decreasing
the background pressure. HRTEM studies of the influence of different ambient gases on the
structural properties of the PbTe nanoparticles are being conducted.
An algorithm for the analysis of the double clad fiber design is presented. The algorithm developed in the MATLAB
computing language, is based on ray tracing method applied to three-dimensional graphics figures which are composed
of a set of plans. The algorithm can evaluate thousands of ray paths in sequence and its corresponding pump absorption
in each of the elements of the fiber according to the Lambert-Beer law. The beam path is evaluated in 3 dimensions
considering the losses by reflexion and refraction in the faces and within the fiber. Due to its flexibility, the algorithm
can be used to study the ray propagation in single mode or multimode fibers, bending effects in fibers, variable
geometries of the inner clad and the core, and could also be used to study tappers.
A method is proposed for the design of fundamental mode high power resonators, with joined stability zones. A
parameter is created which gives the minimum length a laser resonator should have while having at the same time the
broadest stabilities zones. For multimode and large mode volume resonators, a configuration is introduced for
maximizing the laser overall efficiency due to the compensation of the astigmatism induced by the flash lamp pumping
heating. The later configuration proposes a dual-active medium resonator, with 90 degree rotation around the optical axis
between the astigmatic thermal lenses of the mediums. The reliability of this configuration is corroborated
experimentally using a Nd:YAG dual-active medium resonator. It is found that in the pumping power range where the
astigmatism compensation is possible, the overall efficiency is constant, even when increasing the excitation power with
the consequent increase of the thermal lens dioptric power.
An experimental measurement by using Laser Induced Breakdown Spectroscopy (LIBS) and Photoacoustic
Induced by Laser Ablation (PILA), in order to monitoring the microcraks formation inside the
glass induced by laser pulses is presented in this work. The laser was operated in both single pulse and
multi-pulse Q:Switched regime using a passive Cr:YAG crystal as switching element. The LIBS spectra
captured inside the glass avoid identifying the sample composition without influence of surrounding
atmosphere like occurs if the spectra are obtained on the surface. On the other hand, the PILA signal
permits to monitor the process and its dependence from the number and intensity of micro-pulses.
The potential of Nd:YAG pulsed laser to processing PVC sheets minimizing HCl gases emission is investigated. We
studied the gas emission when the PVC is cut by either CO2 or Nd:YAG pulsed laser by using FTIR Spectroscopy.
Optical microscopy of laser treated PVC samples was performed in order to demonstrate the carbonization. On the other
hand, LIBS spectroscopy for two different ranges of pulse duration was employed in order to investigate the plume
composition during the Nd:YAG pulsed laser ablation process. The experiments shows that Cl atoms are emitted during
the Nd:YAG pulsed laser ablation although the HCl gases are produced at low levels. In order to explain the sub-surface
irregularities detected for Nd:YAG laser irradiation, a one-dimensional model is developed to study the temperature
evolution inside the sample. We demonstrate that the ablation mechanisms prevail on thermally drive emission until 70
μm, afterwards the thermal expansion process is already observed.
We report the fabrication of glass multilayer doped with semiconductor nanoparticles. The glass
matrix was fabricated by Plasma Enhanced Chemical Deposition (PECVD using tetramethoxysilane
(TMOS) as precursor. The RF power was supplied by a RF-150 TOKYO HI-Power operating at
13.56 MHz and coupled to the RF electrodes through a matching box. The nanoparticles were
grown by pulsed laser deposition (PLD) of a PbTe target using the second harmonic of a Q-Switched
Quantel Nd:YAG laser in high purity inert gas atmosphere.
The influence of gas and background pressure and in the nanoparticle size and size distribution is
studied. The morphological properties of the nanostructured material were studied by means of High
Resolution Transmission Electron Microscopy(HRTEM), grazing-incidence smallangleX-ray
scattering (GISAXS).
Semiconductor quantum dots [QD] have shown a great number of applications from fluorescent markers to solar cell
devices. Colloidal systems have been usually obtained through chemical synthesis, that have to be devoleped for each
material. The best quality QDs have been obtained with non-aqueous solution and non-physiological pH, requiring a
posterior processing to be used in biology, for example. In contrast, the same physical synthetic method, such as laser
ablation, would be applied to any semiconductor, metallic or dielectric material. Colloidal QD can be obtained by laser
ablation of a target inside any solvent, given this method a very large flexibility. The fluorescence efficiency, however,
depend on the surface traps and stability of colloids. The usual method to avoid surface traps is to grow a cap layer to
passivate its surface and, at the same time, stabilize the colloid, sterically or electrostatically.
In this work we report a novel technique for obtain thiol capped CdTe colloidal quantum dots in one step. A
target immerse in a solution of ethanol and 3-mercaptopropyltrimethoxysilane (MPS), or thiol, was hit by a nanosecond
532 nm laser. With this assembly CdTe luminescent QDs were obtained. The colloid photoluminescence and other
optical and structural properties are studied.
In this work we report a novel technique for obtain thiol capped CdTe colloidal
quantum dots in one step. These nanoparticles are compatible for silica capping indicating their
possible use as fluorescent markers.
Laser ablation (LA) is a thin film fabrication technique which has generated a lot
of interest in the past few years as one of the simplest and most versatile methods for the
deposition of a wide variety of materials. With the rapid development experienced in the
generation of ultra short laser pulses, new possibilities were opened for the laser ablation
technique, using femtosecond lasers as ablation source. It is commonly believed that
when the temporal length of the laser pulse became shorter than the several picoseconds
required to couple the electronic energy to the lattice of the material, thermal effects
could not play a significant role. Since the pulse width is too short for thermal effects to
take place, with each laser pulse a few atom layers of material are direct vaporized away
from the target surface and a better control in the quantum dots (QDs) fabrication could
be achieved.
In this work we report the fabrication of PbTe QDs by femtosecond laser ablation of a
PbTe target in argon atmosphere. Experiments were carried out using a typical LA
configuration comprising a deposition chamber and an ultra short pulsed laser (100 fs; 30
mJ) at a central wavelength of 800 nm. PbTe was chosen because its QDs absorption
band can be controlled by its size to fall in the spectral window of interest for optical
communications (1.3-1.5 μm). This, together with the QD high optical nonlinearity,
makes this material an excellent candidate for development of photonic devices.
It was investigated the influence of the number of laser pulses in the formation of the
nanoparticles. The structural parameters and the surface density of the nanoparticles were
studied by high resolution transmission electron microscopy (HRTEM).
In the past it was observed that buck ball doped glasses showed enhanced optical
nonlinearities. However, carbon nanotubes are much more stable than buck ball and
should be a better choice for that purpose. Therefore we decided to investigate the
possibility to produce carbon nanotubes doped tellurite glasses and measured their
optical nonlinearities. Tellurite glasses already have a larger nonlinearity compared to
silica, and other, glasses. We produced TeO2-ZnO tellurite family glasses doped with
multi wall Carbon Nanotube (CNT). The CNTs acquired from Carbolex were
vigorously mechanically mixed with the tellurite glass precursors and melted in
platinum crucible around 650°C in a controlled atmosphere inside an electrical induction
furnace. We used the lowest temperature possible and controlled atmosphere to avoid
the CNT oxidation. The glass melt was cast in a stainless steel and thermally treated at
300°C for 5 hours to relieve internal stresses. The samples were than cutted and
polished to perform the optical characterization. We measured refractive index and
thermo physical properties, such as vitreous transition Tg, crystallization onset Tx and
melting Tf temperatures. Raman spectroscopy showed the possible presence of CNTs.
In this work we report the fabrication of PbTe quantum dots multilayers embedded in SiO2 by
alternatively use of Laser Ablation and Plasma Enhanced Chemical Vapor Deposition
techniques. The quantum dots were grown by pulsed laser deposition (PLD) of a PbTe target
using the second harmonic of a Q-Switched Quantel Nd:YAG laser in high purity argon
atmosphere. The glass matrix was fabricated by PECVD using tetramethoxysilane (TMOS) as
precursor. The RF power was supplied by a RF-150 TOKYO HI-Power operating at 13.56 MHz
and coupled to the RF electrodes through a matching box. The deposition rates as well as the best
growth parameters for both the nanoparticles and the glass matrix were obtained from a previous
work. The morphological properties of the nanostructured material were studied by means of igh
Resolution Transmission Electron Microscopy(HRTEM), grazing-incidence small-angle X-ray
scattering (GISAXS) and X-ray reflectometry . Unlike HRTEM, which extracts information of a
submicron region of the sample and only a few thousand particles are observed, GISAXS signal
is obtained through an average over orders of magnitude larger number of particles (perhaps 1012
particles) distributed over an area of tens of square millimeters. This fact means that GISAXS
sampling is much more representative of the sample as whole.
Finally, multilayers were grown inside a Fabry-Perot cavity. The complete system operates as
an optical switching device for the infrared region. The device was characterized by Scanning
Electron Microscopy and optical absorption.
PbTe thin films were grown on BK7 glass and Si(100) substrates using femtosecond pulsed laser deposition at room temperature. The influence of the background pressure and the laser fluence on the structural and optical characteristics of the PbTe films was
studied. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the surface and structural properties of the deposited PbTe thin films, respectively. Transmission spectroscopy measurements in the visible and infrared region
(VIS-IR) were used to investigate the optical properties of the PbTe thin films.
A new polymeric open optical fiber with a star cross section from extruded PMMA grains was
developed. We have painted the external surface of this fiber with the Europium chelate or
Antracene. We have observed the typical luminescence of these compounds when excited with
nanosecond 355 nm pulsed laser. These results show that the developed fiber presents potentialities
for optical sensing.
We have been able to produce soft glass conventional core-clad and micro-structured fibers using rod-and-tube and stack-and-draw method respectively. The stack-and-draw technique shows several difficulties when used with soft glasses, that we managed to avoid using two different lead and alkaline glasses. Non commercial glasses and fibers were thermo-mechanically and optically characterized.
Tellurite glasses are important as a host of Er3+ ions because of their great solubility and because they present broader
gain bandwidths than Er3+-doped silica, with promise to increase the bandwidth of communication systems. However,
the small glass stability range (GSR) of tellurite glasses compromises the quality of the optical fibers. We show that the
addition of CsCl to tellurite glasses can increase their GSR, making it easier to draw good quality optical fibers. CsCl
acts as a network modifier in glass systems, weakening the network by forming Te-Cl bonds. We show that the thermal
expansion coefficient mismatch is in the right direction for optical fiber fabrication purposes and that the Bi2O3 content can be used to control the refractive index of clad and core glasses. Single-mode and multi-mode Er3+-doped optical
fibers were produced by the rod-in-tube method using highly homogeneous TeO2-ZnO-Li2O-Bi2O3-CsCl glasses. Far infrared spectra of the glass samples exhibit absorption bands of the Te-Cl bond.
Multilayers of PbTe quantum dots embedded in SiO2 were fabricated by alternatively use of Laser
Ablation and Plasma Enhanced Chemical Vapor Deposition techniques. A set o samples containing
different PbTe nanoparticles sizes was prepared for the study. The morphological properties of the
nanostructured material were studied by means of grazing-incidence small-angle X-ray scattering
(GISAXS) and x-ray reflectometry (XRR) techniques. A preliminary analysis of the GISAXS
spectra provided information about the multilayer periodicity and its relationship to the size of the
deposited PbTe nanoparticles.
Multilayers of PbTe quantum dots embedded in SiO2 were fabricated and characterized by
means of Fourirer transform infrared and x-ray spectrometry and transmission electron
microscopy. The quantum dots were grown by laser ablation of a PbTe target using the second
harmonic of a Q-Switched Quantel Nd:YAG laser under high purity argon atmosphere. The
glass matrix was fabricated by Plasma Enhanced Chemical Vapor Deposition using
tetramethoxysilane as precursor. The reason for choosing PbTe was the absorption bands this
material exhibits in the region of interest for optical communications 1.3-1.5μm making this
material an excellent candidate for development of optical devices.
For the glass matrix, it was studied the influence of growing parameters like RF power,
distance between the RF electrodes and the total pressure in the properties of the SiO2 films. The
parameters for the PbTe ablation were assumed from a previous work. FTIR and refractive index
measurements were used to estimate the best growth parameters for the dielectric host.
TMOS partial pressure proved to be an important parameter to diminish the nanoparticle
coalescence during the multilayer fabrication. Multilayer X-ray diffraction patterns were used to
estimate the nanoparticles diameter. Morphological properties of the nanostructured material
were studied using transmission electron microscopy.
Micro-structured Er3+ - Tm3+ co-doped tellurite fiber with three rings of holes was
fabricated using a soft glass drawing tower by a stack-and-draw technique. Amplified
spontaneous emission (ASE) around 1550nm band were observed when pumped with both,
980nm and 790nm, lasers.
This work reports the fabrication of planar and channel waveguides by Ag+ → Na+ ion exchange in an Er3+ doped tellurite glass with a composition of 75TeO2-2GeO2-10Na2O-12ZnO-1Er2O3 (mol %). The glass was chemically stable during the ion-exchange process. We have been able to produce single and multi-mode planar waveguides controlling the depths of the waveguides by varying ion-exchange temperatures, from 250 to 280 °C, and times, from 3 to 12 h. We also show preliminary results of channel waveguide fabrication with the same technique. The waveguide effective refractive index curves and attenuation (11 dB/cm) at 1536 nm were measured with a Metricom prism coupler. The Amplified Spontaneous Emission (ASE) spectra showed a 152 nm bandwidth when pumped with 120 mW laser pump at 980 nm.
Thermal Lens (TL) and spectroscopic characterizations were performed in 70TeO2-19WO3-7Na2O-4Nb2O5 (mol%) tellurite glasses. TL measurements were accomplished in Er3+ /Tm3+ co-doped tellurite glasses in function of the Tm2O3 concentration (0.4-1.6 x1020 ions/cm3). Fluorescence spectra at 488 nm showed that Er3+ /Tm3+ co-doped tellurite glasses present several emission bands between (500-1800) nm. However, the more intense emission bands correspond to the Tm3+ and Tm3+ transitions (4I13/2 → 4I15/2 and 3F4 → 3H6), respectively. The absolute nonradiative quantum efficiency (φ) was determined by TL method. Higher values of φ were obtained with the increase of Tm2O3 concentration inside of the Er3+/Tm3+ co-doped tellurite glasses. These results are corroborated by the Judd-Ofelt calculations.
In this work we used a Thermal Mechanic Analysis equipment to produce the channel FOG waveguides by pressing an Er3+ doped tellurite glass optical fiber against one Er3+ ion doped tellurite glass substrate kept under Tc ± 30 oC (Tc = soft point). The luminescence and waveguide refractive index were measured. Scanning electron microscopy was used to observe the obtained structure. The objective is to produce a new concept in components of integrated optical circuits. Then this work report the production of Er3+-doped tellurite glass channel waveguides using the novel concept of Benson et al[1] of fiber on glass (FOG). To succeed with this technique it is important to correlate the main thermo-physical characteristics of the substrate and the fiber, which are the transition temperature Tg, the temperature of the onset of crystallization Tx, the maximum crystallization temperature Tc and the thermal expansion coefficient. The Tg, Tx and Tc values were determined by Differential Thermal Analysis (DTA), while the thermal expansion coefficient was determined by Thermal Mechanical Analysis (TMA). For the FOG purpose the thermal stability range, Tx - Tg, is an important temperature region which defines if the glass will have enough viscosity to shape in the FOG concept.
Er3+-Tm3+ co-doped tellurite photonic crystal fiber was fabricated via a stack-and-draw procedure and without using extrusion in any stage. The final fiber presents a 187 nm bandwidth of amplified spontaneous emission (ASE) intensity around 1550nm when pumped with 790nm. In this manuscript a soft-glass tube fabrication technique, using the centrifugation method, is also shown.
Multilayer of PbTe quantum dots embedded in SiO2 were fabricated by alternatively use of Plasma Enhanced Chemical Vapor Deposition and Laser Ablation techniques. The optimal growing parameters for both the SiO2 films and the PbTe quantum dots were obtained. The refractive index and optical absorption of the sample were studied. Multilayer X-ray diffraction patterns were used to estimate the nanoparticles diameter. Morphological properties of the nanostructured material were studied using Transmission Electron Microscopy. Both absorption spectra and X-ray diffraction patterns reveled the nanoparticles are 6-8 nm in diameter, consequently appropriate for developing optical devices in the infra red region. Finally the multilayer was grown inside a Fabry Perot cavity. The transmittance of the one-dimensional photonic crystal was measured.
In this work we present the fabrication of tellurite glass photonic crystal fiber doped with a very large erbium concentration. Tellurite glasses are important hosts for rare earth ions due to its very high solubility, which allows up to 10,000 ppm Er3+ concentrations. The photonic crystal optical fibers and tellurite glasses can be, therefore, combined in an efficient way to produce doped fibers for large bandwidth optical amplifiers. The preform was made of a 10 mm external diameter tellurite tube filled with an array of non-periodic tellurite capillaries and an erbium-doped telluride rod that constitute the fiber core. The preform was drawn in a Heathway Drawing Tower, producing fibers with diameters between 120 - 140 μm. We show optical microscope photography of the fiber’s transverse section. The ASE spectra obtained with a spectra analyzer show a red shift as the length of the optical fiber increases.
Thin films of glass doped with PbTe quantum dots were successfully fabricated. The semiconducting quantum dots were grown by laser ablation of a PbTe target (99.99%) using the second harmonic of a Q-Switched Quantel Nd:YAG laser under high purity argon atmosphere. The glass matrix was fabricated by a plasma chemical vapor deposition method using vapor of tetramethoxysilane (TMOS) as precursor. The QD's and the glass matrix were alternately deposited onto a Si (100) wafer for 60 cycles. Cross-section TEM image clearly showed QD's layer well separated from each other with glass matrix layers. The influence of the ablation time on the size distribution of the quantum dots is studied. HRTEM revealed anisotropy in the size of the QD's: they were about 9nm in the high and 3-5 in diameter. Furthermore HRTEM studies revealed that the QD's basically growth in the (200) and (220) directions. The thickness of the glass matrix layer was about 20 nm. Absorption, photo luminescence and relaxation time of the multilayer were also measured.
Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility. One of the most important parameter for optical amplification is the lifetime of the excited states, which strongly depends on the crystal field around the ions. That crystal field changes dramatically with the host glass and with rare earth concentration. Excited state lifetime studies have been performed on Er3+-doped-TeO2-WO3-Na2O-Nb2O5 glass system. Therefore, we decided to study the Er3+ excited states lifetimes and compared with the Judd-Ofelt theory predictions. We measured only the 4I13/2 to 4I15/2 transitions lifetimes. The other transitions lifetimes can be inferred by knowing the Ω2, Ω4, Ω6 Judd-Ofelt parameters. These parameters were calculated with the electric-magnetic dipole transition oscillator strength for the desired excited levels and ground state obtained from the optical absorption spectra. After performing this calculation we estimated that maximum quantum efficiency (η), measured/calculated lifetimes ratio, would be achieved at 7500ppm (%wt) Er3+ content.
Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility and very large amplification bandwidth. Among several tellurite glasses the TeO2-WO3-Na2O-Nb2O5 system show one of the largest bandwidth. Our previous characterization of lifetime using the omega2, omega4, omega6, Judd-Ofelt parameters indicate a quantum efficiency maximum for 7500ppm Er3+ concentration. Therefore we decided to produce jointed Er3+ and Tm3+ single mode optical fibers with this glass system keeping the 7500ppm Er3+ concentration and varying the Tm3+ concentration from 2500ppm to 15000ppm. This single mode fiber was pumped by 120mW of the semiconductor laser at 790nm and we observed a flat ASE bandwidth from 1400 to 1570nm for the 5000ppm Tm3+ concentration.
In the present work Bi thin films were obtained by Pulsed Laser Deposition, using Nd:YAG lasers. The films were characterized by optical microscopy. Raman spectroscopy and X-rays diffraction. It was accomplished the real time spectral emission characterization of the plasma generated during the laser evaporation process. Highly oriented thin films were obtained.
The research projects at the Laser Technology Laboratory of Havana University are devoted to Nd:YAG lasers development and to the implementation of new laser applications in different fields. Relative to the lasers research the objective is the development of compact, light and relative low-cost lasers. This development is based on a vertical integration strategy that establishes the own elements production as pumping cavities, multilayer mirrors and filters, power supplies control units and others. Several investigations are carried out using these lasers: thin film deposition of semiconductor, ferroelectric and magnetic materials by laser ablation, subsurface laser marking of transparent materials, pulse laser surface silicon texturing and laser cleaning of art works.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.