790nm-pumped Tm-doped fibre lasers provide a number of distinct benefits for integration into next generation DIRCM
systems. Incorporation of Tm-doped fibre technology into mid-IR laser systems has been demonstrated in two main
architectures to date; in early works the fibre laser was used as a low quantum defect pump source for Q-switched solidstate
holmium laser which was subsequently shifted to the mid-IR using a ZnGeP2 OPO  and more recently, a pulsed
fibre laser systems was used for directly pumping the OPO . He we present two fibre laser systems for integration into
DIRCM systems. Firstly we present a 70W MOPA system (pump power limited) operating at 1908nm with 53% slope
efficiency from the amplifier stage for pumping Ho:YAG. Secondly we present a pulsed fibre laser system producing
over 4kW peak power at 1910nm using all single-mode fibres.
Most system analyses of CW high-power lasers propagating in the atmosphere assume a simple additive linear relation of the impact of thermal blooming and optical turbulence in the atmosphere to the propagated laser beam spreading. In other words, both effects are treated as if they would follow Gaussian statistics in an RMS sense.
While the statistics of optical propagation in a turbulent atmosphere can be modeled as Gaussian to first order, thermal blooming is a deterministic nonlinear optical phenomenon. To the best of our knowledge, there is no reason for adding linearly the beam spreading due to these two optical effects. In fact, assuming no interplay in the presence of a strong nonlinear optical interaction is
counter-intuitive. As a result, we have performed extensive numerical Monte-Carlo optical wave-propagation simulations, >50,000 realizations, in the presence of thermal-blooming and
atmospheric turbulence to varying degrees. During the propagation, the amplitude and the phase of a high power laser
field are coupled by the interplay of diffraction, refractive turbulence and thermal blooming. In some cases, we have
observed in our numerical experiments a strong coupling between turbulence and nonlinear thermal blooming.
An analysis of the parametric interaction and the initial fiber geometry to achieve wavelength conversion
from common laser sources operating in the 1030-1064nm spectral band into the 900-950nm wavelength range has
been performed. The preliminary analysis shows that new fiber designs involving fibers with cores engineered with
crystal-like shapes and also pulsed fiber sources operating at wavelengths in the 1030-1064nm will be required to
achieve efficient emission within the desired wavelength range. Both the fiber required for phase-matching the
parametric nonlinear process and the pulsed fiber laser pump source are within reach of current technology. They both
require engineering efforts to produce a packaged, rugged and compact source.
We have developed a fiber laser system capable of producing over 100W of average power. We have achieved
1.5mJ/pulse/fiber resulting in peak powers in excess of 2MW with 0.6ns pulses and near diffraction limited beams. In
another fiber, we have achieved over 0.5mJ/pulse with pulses of 700ps exceeding 500kW of peak power in polarization
maintaining Ytterbium doped fiber. In both cases, wall-plug efficiencies, excluding cooling of the pump diode lasers, in
excess of 15% were also achieved. The system we have developed is based in an all fiber design except for the last high
peak power isolator requiring free space optics. With the advent of such a component, a scalable 1.5MW/arm all fiber
laser system is proven to be possible.
Coherent Laser Radar is a powerful remote sensing tool, which can be applied to range-finding, target
discrimination, vibrometric monitoring, air pollution monitoring, aircraft wake-vortex and clear-air turbulence
analysis. A high power, highly efficient, near diffraction limited and highly reliable pulsed coherent laser source is a
key sub-system required in a coherent Lidar sensor. When humans are involved, eye safe laser emission is also
typically required. Therefore a highly efficient fiber laser system based on a coherent Master-Oscillator followed by
a chain of Erbium (EDFA) and Erbium co-doped with Ytterbium fiber amplifiers (EYDFA) is ideally suited for this
In this paper, we are presenting an all polarization-maintaining fiber architecture and experimental results on
such a high peak power fiber laser system allowing for versatile modulation strategies at a wavelength of 1563nm
commensurate with a clear atmospheric transmission window and eye-safe operation. The system is constituted by
three amplification stages, all based on Polarization-Maintaining fiber. With 660ns and 20Kpps, over 500W peak
power pulses have been experimentally demonstrated with near diffraction limited performance with this all PM
KEYWORDS: Signal to noise ratio, Fiber amplifiers, Optical filters, Optical amplifiers, Phase modulation, Digital filtering, Interference (communication), Lab on a chip, Signal detection, Bandpass filters
We report on a novel fiber based coherent detection system employing an optical preamplifier, a spectrum bandpass filter, and a time-domain filter. The time-domain filter, a synchronous time gate, reduces the in-band Amplified Spontaneous Emission (ASE ) beat noise, which cannot be achieved by the spectrum bandpass filter alone. In preliminary experiments with a 100 GHz bandpass filter, no degradation is observed from the optically preamplified coherent detection compared to pure coherent detection. With a 10 ns pulse width, 500 kHz repetition rate, and 10 pW input power, 2.78 dB and 1 dB signal-to-noise (SNR) improvement has been achieved, respectively, when 5% and 50% time gating duty cycle is used.
We have tested a series of Ytterbium doped large core fibers operating near 10Kpps and producing pulses of approximately 1ns. We have achieved 0.85mJ/pulse resulting in peak powers in excess of 2MW with 0.4ns pulses and near diffraction limited beams. In another fiber, we have achieved over 1.5mJ/pulse with pulses of 900ps corresponding to 1.65MW of peak power and M2 of 2.5. In the latter case, wall-plug efficiencies, excluding cooling of the pump diode lasers, in excess of 15% were also achieved. This fiber amplifier has operated for 2 months without any degradation or observed optical damage.
In this paper we present advances made in the development and fabrication of highly efficient, large-mode area fibers for eye-safe wavelengths (1.55 μm, 2.0 μm). LMA Er/Yb co-doped and Tm doped fibers have been successfully fabricated, with 25 μm core and 250 to 300 μm clad diameters, that are suitable for nanosecond pulsed amplification in LIDAR applications as well as high power CW amplification. Manufacturing challenges for these novel fibers are discussed. Measured and modeled data, for both types of fibers, are presented. The development of non-PM and PM-LMA fibers for eye-safe applications is expected to spur rapid progress in power scaling at these wavelengths, similar to that witnessed by the industry at 1.06 μm.
N-on-1 LIDT measurements were performed on ytterbium doped preforms used to make high peak power fiber amplifiers. Damage measurements were complicated by large index of refraction changes across the preforms. These difficulties were overcome by monitoring the beam profile before and after the samples and by only taking data where the transmitted beam was not significantly distorted. Single and 1000 shot data suggest slight laser conditioning of the preforms and rule out laser fatigue in the doped cores and surrounding fused silica. At 1064 nm, inside the emission spectra, there seemed to be little influence of the Yb dopant concentration on the measured LIDT.
Various military lidar applications such as underwater mine detection, obstacle avoidance, IRCM, and 3 D lidar incorporate high repetition rate solid-state lasers to accomplish the mission. The recent advances and demonstrations in high power Ytterbium (Yb) fiber lasers/amplifiers make the fiber media a viable alternative to bulk lasers for these applications. The fiber laser geometry maximizes the pump absorption and mode matching for overall high efficiency, (factor-of-two over bulk laser sources) while minimizing thermal effects. In this presentation we will show experimental and modeling results on various master oscillator Yb doped polarization maintaining (PM) fiber amplifiers being developed for high repetition rate applications. We have demonstrated >20 W of average output power with M2 <1.3, repetition rates up to 75 kHz and pulse widths ranging from <1 ns to 250 ns. Results of a pulsed PM MOFA efficiently pumping a Periodically Poled Lithium Niobate (PPLN) optical parametric oscillator (OPO) and KTP doubler will also be presented.
New developments in the semiconductor industry are driven by two trends: reducing the device dimensions and further increase of the switching speeds or electrical bandwidths. The electronics industry average feature sizes of integrated circuits (ICs) will be of the order of 100 nm by the year 2010. For instance, currently produced MOS field-effect transistors support electrical fields between the source and the drain that are greater than 105 V/micrometer with switching speeds of 10 - 100 psec. Techniques which would resolve such electrical fields, with the appropriate resolutions in time and in space, are of paramount interest both at the industrial level and in basic research. Initial experiments performed on samples consisting of two metallic electrodes deposited on fused silica substrates covered by thin polymer films show that with only 1 (mu) W of average optical power, a second harmonic signal triggered by an AC/DC field could easily be detected with a spatial resolution of less than 1 micrometer. We anticipate electrical field detection sensitivity of less than 1 mV/micrometer with our technique with 100 nm resolution spatially and less than 1 psec resolution in time.
Since the early work of Kelley in 1965, self-focusing in transparent dielectric materials was recognized as one of the mechanisms of optical induced damage in laser materials. Recently the experimental demonstration of stable solitary waves in Quadratic materials has shown that the catastrophic collapse of laser beams can be arrested in materials with a pure second order response. New ways to solve the self- focusing damage mechanism in laser materials can result from such an experimental discovery. Indeed choosing host laser materials with a quadratic nonlinearity can considerably delay the appearance of the laser beam collapse. We present theoretical considerations and numerical calculations on materials design concepts which can in practice resolve the self-focusing collapse in the presence of a quadratic nonlinearity.
A novel switch is introduced which has the capability of interconnecting 1 input channel to N output channels in a single device, without crosstalk. It is based on the unique properties of spatial solitons which propagate without diffracting in space and create index channels which can be used to guide signals at the same or different frequencies. Angular scanning of the soliton channels is achieved by chirping the phase of the input wavefront. Some properties of the switch and the initial demonstration of soliton scanning in an AlGaAs planar waveguide at 1550 nm are discussed.
The third order susceptibility of a polydiacetylene polymer was investigated by three different nonlinear spectroscopic techniques in order to test two existing microscopic theories which predict the nonlinear response of such molecular systems. We previously found good agreement between a four essential state model and the THG spectra of (pi) -electron conjugated backbone polymers. However, when such a model was extended to two additional third order susceptibility spectra, poor agreement was found. In contrast the recently developed anharmonic oscillator model fitted well all four experimentally obtained spectra of the third order susceptibility.
We demonstrate that the Maker fringe technique can be applied to third order frequency mixing experiments designed to measure the electronic (chi) (3)(-(omega) 3;(omega) 1,(omega) 1,-(omega) 2) dispersion with (omega) 1 for a poly[3-tetradecylthiophene] thin film. Both the magnitude and the phase of the (chi) (3) were obtained. In the magnitude spectrum there was a strong three-photon resonance where the output frequency ((omega) 3equals2(omega) 1-(omega) 2) corresponds to the energy level of the first one photon state. We also found a peak which could be either a 2(omega) 1 or a (Delta) (omega) (equals(omega) 1-(omega) 2) resonance. Since this method is considered to be more sensitive to two-photon resonances that third harmonic generation, it can be used as a powerful tool to probe two photon states in the case of thin film polymer samples.
Fiber Lasers VIII: Technology, Systems, and Applications
24 January 2011 | San Francisco, California, United States
Fiber Lasers VII: Technology, Systems, and Applications
25 January 2010 | San Francisco, California, United States
Fiber Lasers VI: Technology, Systems, and Applications
26 January 2009 | San Jose, California, United States
Nonlinear Optical Materials
1 November 1999 | Bellevue, WA, United States
SC784: Fiber Lasers for Defense Applications: Fibers, Components and System Design Considerations
Fiber laser technology has the potential to make a significant impact in many defense applications, from LIDAR and remote sensing to high energy laser weapons systems. This emerging laser technology offers many intrinsic advantages over traditional DPSSLs. Widespread publications in the research community have demonstrated an impressive array of power scaling results, both CW and pulsed and at wavelengths from 1um to the eyesafe 1.5um and 2um wavelengths. Advantages associated with the technology are high wallplug efficiency leading to reduced electrical power requirements and easier system cooling, but also robustness, good beam quality and highly flexible system performance. These, coupled with (remote) fiber delivery options make the technology unique in certain applications.
The topics to be covered include: an explanation of the basic fiber parameters, double-clad fiber designs and covering such concepts such as large mode area fibers, modal/beam quality, PM fibers etc.; rare earth doping and spectroscopy of Yb-1um, Yb:Er-1550 and Tm-2um; component specifications and availability (couplers, isolators, seed laser diodes etc); limitations to scaling fiber devices, non-linear limitations, damage thresholds, etc.; design rules and concepts for pulsed fiber lasers and amplifier chains, recent results from the literature; and system specifications and possible application areas, comparison and advantages over other laser technologies.
This tutorial will cover the major aspects of designing and building a fiber laser, from the fiber itself through the various state of the art fiber components and discuss the system parameter space that best makes use of the intrinsic advantages of the technology.