We present comprehensive numerical models of the cladding pumped Raman laser and cladding pumped amplifier inclusive of random distributed feedback due to Rayleigh scattering. Useful analytical approximations to the numerical models of laser and amplifier shall be presented and compared to experiment.
Coaxial fiber lasers, consisting of a Ho-doped core surrounded by a Tm-doped ring, are studied via experiments and numerical simulations. Previous simulations indicated that coaxial fiber lasers have the potential to reach power conversion efficiencies of up to 54%, but experiments have yielded much lower efficiencies. To understand this difference, a wavelength dimension is added to the standard model and simulations are compared to experiments. An output coupler is designed to optimize the efficiency of coaxial fiber systems, and a path towards realizing the predicted 54% efficiency is presented.
Recent progress in development of Mid–IR lasers at ~2.8 µm and ~3.5 µm based on commercial Er:ZBLAN fibers has enabled variety of environmental sensing, defense and medical applications. This development faces a few major challenges, among which are relatively low laser efficiency (stemming from the naturally high quantum defect of laser operation) and power scaling limitation due to output self-pulsing (perceived to be coming from presence of clustering or ion pairs in a highly doped fiber, which act as saturable absorbers).We report on a study of the power scaling of a 976 nm diode-pumped double-clad Er:ZBLAN fiber laser at the ~2.8 µm, 4I11/2-4I13/2 transition. The passively cooled 7% Er-doped fluoride fiber laser was shown to achieve slope efficiency over 25% and 50 W with respect to launched pump power in both CW and Quasi-CW regimes of free-running operation. Laser power scaling was found to be limited by available 976 nm diode pump power.
We compare the laser performance of a low Tm3+-doped silica fiber laser as pumped at 800 nm to one as pumped at 1620 nm. Using 800 nm non-resonant (3H6→3H4) pumping, 5.5 W of 1940 nm at 32% optical slope efficiency was demonstrated while 1620 nm resonant pumping (3H6→3F4) yielded 13 W with 55% slope efficiency from the same Tm-doped fiber. We also include experimental results our first demonstration of 1620 nm resonant pumping of a Tm-doped fiber with 15.5 W and 67% slope efficiency using an optimized fiber coupled source.
We report on the use of a 976 nm diode pumped Er:YVO4 slab for the amplification of 1603 nm laser radiation with a small signal gain of 2.1. To the best of our knowledge, this represents the first use of Er:YVO4 as a non-resonantly pumped amplifier.
We report on the performance of an eye-safe laser based on a Er:YVO4 single crystal, diode-pumped at 976 nm (4I15/2→4I11/2 transition) and operating at 1603 nm (4I13/2→4I15/2 transition) with good beam quality. A 10 mm long Er3+:YVO4 slab, cut with its c-axis perpendicular to the laser cavity axis, was pumped in σ-polarization and lased in π-polarization. The laser operated in a quasi-continuous wave (Q-CW) regime with nearly 9 W output power, and with a slope efficiency of about 39% with respect to absorbed power. This is believed to be the highest efficiency and highest power achieved from an Er3+:YVO4 laser pumped in the 970-980 nm absorption band.
We have demonstrated a new form of Nd:YVO4 amplifier operating at 1064 nm based on a 800 µm thick Nd:YVO4 gain layer bonded to a 4H-SiC prism. The amplifier was tested in the ‘master oscillator - power amplifier’ (MOPA) configuration, where both the seed source and the single pass amplifier were operated in a quasi-continuous wave (Q-CW) regime: pulse duration 500 µs, pulse repetition frequency (PRF) - 100 Hz. The Nd:YVO4gain element was pumped by a 808 nm laser diode bar stack to amplify seed inputs in the power range of 1 to 55 W with a gains of 4 to 2.6, respectively, with 25% optical-to-optical extraction efficiency. The temperature distribution of the gain medium was measured under operational conditions using thermography.
The spectroscopic properties of Ho3+-doped YVO4 were studied at cryogenic and room temperatures in the 2 μm spectral region to clarify recent observations of efficient dual-wavelength laser operation in this material. Polarized absorption cross sections were measured, and stimulated emission cross sections were determined using the reciprocity method coupled with Füchtbauer-Ladenburg calculations. The observed laser emission wavelengths were at 2041.7 nm, 2054.2 nm, and 2068.5 nm; the first two corresponding to pi transitions and the third to a sigma transition. Gain cross section calculations were used to predict which of the three wavelengths would lase for a given output coupler reflectivity. In depth analysis of the gain cross section in the region between 80 K and 100 K showed that the laser output wavelength is very susceptible to minor changes in temperature.
We report what is believed to be the first laser operation based on Ho3+-doped YVO4.
The Ho+3: YVO4 was resonantly diode-pumped at ~1.93 μm to produce up to 1.6 W of continuous
wave (CW) output power at ~2.054 μm. The laser had a slope efficiency of ~38% with respect to
absorbed power. We have measured the absorption and stimulated emission cross sections of The
Ho+3: YVO4 at 77 K and present the calculated gain cross section spectrum at 77 K for different
excited state inversion levels.
We present spectroscopic properties and lasing results of Ho3+-doped Yttria (Y2O3), LuAG
(Lu3Al5O12), and YAG (Y3Al5O12) at wavelengths beyond 1.6 μm. High resolution
measurements of absorption and stimulated emission cross sections of Ho3+ in these hosts from
77K to 300K are reported. Laser operation based on 5I7 to
5I8 transitions of Ho3+ in these hosts is
demonstrated.
We have measured upconversion fluorescence resulting from the excitation of room temperature 1% and
5% Er:YAG by a 1532 nm nanosecond pump source. Measurements of the fluorescence decay from the
4I13/2, 4I11/2,
4F9/2
and
4S3/2 manifolds to the 4I15/2 ground state manifold were observed over a wide range of
excitation pulse fluence values. A unique set of upconversion parameters were extracted from the
measurements using a modification of the traditional rate equation model. Results of calculation are
compared to measurement.
Remote monitoring of carbon dioxide (CO2) is becoming increasingly
important for homeland security needs as well as for studying the CO2
distribution in the atmosphere as it pertains to global warming problems.
So, efficient solid-state lasers emitting in the 1.55 - 1.65 μm spectral
range, where CO2 absorption lines are, (i), plentiful and, (ii), carry
significant relevant information, are in great demand. Reported here is the
first laser performance of resonantly pumped Er3+-doped scandia (Sc2O3)
ceramic. The laser was operated in the cryogenically-cooled regime with
the quantum defect (QD) of only 4.5%, which, along with superior thermal
conductivity of scandia, offers significant eye-safe power scaling potential
with nearly diffraction limited beam quality. Slope efficiency of 77% and
Q-CW output power of 2.35 W were obtained at 1605.5 nm which has
significant utility for counter-IED applications.
Efficient ultra-low-photon-defect resonantly diode-pumped Er:YAG cryogenically-cooled laser is demonstrated for
the first time. Quasi-CW diode pumping by InGaAsP/InP 10-diode bar stack (without spectral narrowing) was
implemented. Laser performance at ~80°K in this first experiment was found to be 71.5% efficient (output power
versus power absorbed in the cavity mode, slope). Er:YAG laser output variations with the gain medium
temperature was investigated. Maximum quasi-CW power of ~65 W was achieved by optimization the gain
medium operating temperature. and to photon number
splitting attacks, thus resulting in a high efficiency in terms of distilled secret bits per qubit. After having successfully tested the feasibility of the system [3], we are currently developing a fully integrated and automated prototype within the SECOQC project [4]. We present the latest results using the prototype. We also discuss the issue of the photon detection, which still remains the bottleneck for QKD.
We present lasing results of a SiC face cooled 4% Nd:YAG ceramic in an unstable cavity mode configuration (slope
efficiency 35%) under quasi-CW pump conditions. This work demonstrates the first time lasing of a high temperature
bonded, anti-reflection (AR) coated bonded SiC/Nd:YAG assembly. Finite Element Analysis (FEA) modeling of the
temperature, stress, thermal lensing and polarization loss of the SiC/Nd:YAG stack under lasing conditions are presented.
We have demonstrated for the first time, to the best of our knowledge, that Silicon Carbide (SiC) may be used as an efficient heat sinking material for face cooling of gain media in solid-state lasers. Comparative thermal modeling and temperature distribution measurements of diode-pumped 4 at.% Nd:YAG ceramic laser medium face cooled by undoped YAG (as a baseline), Diamond and SiC lead to the conclusion that SiC is an effective replacement for much more expensive diamond as an intracavity face cooling material. Laser performance of a SiC face-cooled 4 at.% Nd:YAG ceramic press-fit stack was demonstrated with a 24% slope efficiency with no AR coatings between the SiC and YAG.
We have performed a laser evaluation of the Yb3+-doped Y2O3 ceramic laser material. The Q-CW output power in excess of 30 W was obtained with the slope efficiency of 47.3%. This output power is, to the best of our knowledge, the highest reported so far for diode-pumped Yb3+-doped Y2O3 laser.
The need for tunable optical transmitters in optical networking is growing at a rapid rate. A tunable optical transmitter is the combination of a tunable laser, an isolator, and a modulator. Although today lasers and modulators could be integrated together on a single chip, an integrated component of this type would not be useful because the absence of an isolator between the two elements would cause optical reflections to reach the laser, leading to a high level of frequency chirp and relaxation oscillations. Therefore discrete external modulators are used, and lasers are coupled to them through discrete optical isolators. We report on recent developments in integrated active, thermo-optic, magneto-optic and electro-optic technologies that enable the production of a fully integrated tunable transmitter. This transmitter consists of a planar polymer waveguide circuit that is built on a silicon chip and in which films of a variety of materials are embedded. This subsystem on a chip includes a laser chip coupled to a thermo-optically tunable planar polymeric filter resulting in a tunable external cavity laser; an integrated magneto-optic isolator consisting of a planar polymer waveguide with inserted thin films of yttrium iron garnet for Faraday rotation, crystal ion sliced LiNbO3 for half-wave retardation, and polarizers; and an electro-optic modulator consisting of a crystal ion sliced LiNbO3 thin film patterned with a Mach-Zehnder interferometer and grafted into the polymer circuit, capable of operating with less than 5 Volts at modulation speeds up to 40 Ghz.
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