We have developed a time dependent model for the eye-safe laser emission at 1.6&mgr;m, representing transitions from
the manifolds 4I13/2 to 4I15/2 of trivalent Er-doped YAG (Y3Al5O12). The model is based on a set of coupled first-order
differential equations (rate equations) that describe the laser kinetics of this quasi-three level laser system.
Also called zero-dimensional (0-D) equations, these equations are time only dependent with no spatial dimension
dependency. The model is anchored to experimental results including the experimental Stark levels that are
populated according to a Boltzmann distribution at room temperature. Emission cross section parameters are
calculated using reciprocity methods from experimental absorption cross sections. A MATLAB code is written and
the equations are solved numerically for output power and slope efficiency and threshold. The results are useful
with significant progress towards predicting the published experimental laser data. This model can be optimized for
its parameters such as output coupler reflectivity, ion concentration, etc and used for other hosts.
Recent advances in the growth of rare earths doped into ceramic (poly-crystalline) materials have generated considerable interest for the next generation of tactical laser systems mainly because ceramics provide larger size, greater strength and lower cost factors in design than their single-crystalline counterparts. For many years, Nd:YAG has been the laser material choice for stability and high power Er has been an ion laser source of interest for defense due to its eye-safe emission at 1.5 μm and has applications in infrared counter-measures, illumination detection, remote sensing and communication technologies.
A model Hamiltonian including atomic and crystal-field terms is diagonalized within the complete 4f11 SLJMJ basis set which includes 364 states. Within the standard deviation obtained between 117 comparable calculated-to-observed Stark levels, one set of atomic and crystal-field parameters describes the splitting of the Nd3+ and Er3+ energy levels in either the ceramic or single-crystal host.
We report a detailed crystal-field splitting analysis for a number of multiplet manifolds of Nd3+ and Er3+ in both the ceramic and single-crystal form of YAG (Y3Al5O12). With few exceptions, analysis shows that the energy-level structure of Nd3+ and Er3+ is similar in the ceramic and single-crystal laser rods.
We demonstrated mutual injection locking and coherent beam combining of three individual Nd:YVO4 laser modules. A beam splitter couples three lasers as well as combines their outputs. In the free running state, the divergence of combined beams is large. Under mutual injection locking, the divergence of the combined beams becomes substantially smaller than that in the free-running state and is as small as that of the individual laser beam. Mutual injection locking was also realized without active stabilization with large individual laser cavity length difference and low individual laser Q-factor.
In order to develop an efficient eye-safe laser, operating in the 1.53 μm region, we have written software that models the performance of a passively Q-switched Er:Yb:glass laser with a divalent cobalt Co2+:spinel saturable absorber. At present a 0D model, which uses a plane-wave approximation, has been completed. The model is based on a set coupled first order differential equations that describe the laser dynamics. These equations represent a two-level Yb3+ diode pump scheme, a five-level Er3+ gain medium, and a four-level Co2+ Q-switch. The model takes into account cooperative upconversion and excited state absorption (ESA) in both the gain and absorber media. Solutions to the rate equations and optimization examples are presented.
Lasers have come a long way since the first demonstration by Maiman of a ruby crystal laser in 1960. Lasers are used as scientific tools as well as for a wide variety of applications for both commercial industry and the military. Today lasers come in all types, shapes and sizes depending on their application. The solid-state laser has some distinct advantages in that it can be rugged, compact, and self contained, making it reliable over long periods of time. With the advent of diode laser pumping a ten times increase in overall laser efficiency has been realized. This significant event, and others, is changing the way solid-state lasers are applied and allows new possibilities. One of those new areas of exploration is the high energy laser. Solid-state lasers for welding are already developed and yield energies in the 0.5 to 6 kilojoule range. These lasers are at the forefront of what is possible in terms of high energy solid-state lasers. It is possible to achieve energies of greater than 100 kJ. These sorts of energies would allow applications, in addition to welding, such as directed energy weapons, extremely remote sensing, power transfer, propulsion, biological and chemical agent neutralization and unexploded and mine neutralization. This article will review these new advances in solid-state lasers and the different paths toward achieving a high energy laser. The advantages and challenges of each approach will be highlighted.
A spectroscopic analysis is performed on Er3+ (4f11) ions doped in order to assess this material for its potential as a near infrared laser. The Judd-Ofelt model is applied to the room temperature absorption intensities of Er3+ (4f11) in NaBi(WO4)2 to obtain the three phenomenological intensity parameters: Ω2 = 5.50 x 10-20 cm2, Ω4 = 1.00 x 10-20 cm2, and Ω6 = 0.71 x 10-20 cm2. The intensity parameters are then used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios for the Er3+ transitions from the excited state multiplet manifolds to the lower-lying manifold states. Using the radiative decay rates for the Er3+ (4f11) transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states of Er3+ are determined in this host. Using the room temperature fluorescence lifetime and the radiative lifetime of the 4I13/2→4I15/2 (1.52 µm) transition of Er3+ in NaBi(WO4)2, the quantum efficiency is determined to be 84% for this laser material.
We have modeled the passive Q-switch performance of divalent cobalt and its spectroscopic parameters in various host media for the Er:Yb:Glass laser that operates near 1.534 micrometers . Our method involves the use of rate equations that assume a three-level gain medium and a four-level absorber medium including excited-state absorption. Numerical integration techniques are used where analytical functions are unobtainable to describe the dynamics within the systems that we have examined. Input into the rate equations is obtained from experimental data that include Co2+ ion concentrations, cross-sections, and lifetimes obtained by time-resolved spectroscopy. The calculated laser output in terms of pulse energies and pulsewidths in ns is compared with experimental results based on different Co2+ absorber host matricies and different cavity designs.
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.