This PDF file contains the front matter associated with SPIE Proceedings Volume 9834, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

L-3 ALST has developed a Generalized Laser and Optics Simulation Suite (GLOSS) to quickly and reliably design high performance laser transmitters. GLOSS uses state of the art wave propagation based algorithms to rigorously simulate the dynamics of laser oscillation. Laser pulse energy, pulse width, beam size, beam shape, and divergence are among the many key performances parameters GLOSS models have the capability to predict. The GLOSS modeling methodology will be discussed and examples of its powerful capability will be demonstrated. Model predictions within 10-15% of actual laser performance data from a sample of experimental lasers will also be shown.

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 investigation of a novel ceramic Tm:Lu₂O₃ amplifier lasing at around 2-μm and offering efficient generation of high-energy pulses with high-peak power at high repletion rate, high efficiency, and with near-diffraction-limited beam quality (BQ). The amplifier has a bandwidth of over 300 nm, which offers broad tunability. The bandwidth also supports generation of ultrashort pulses in the femtosecond regime. The “2-for-1” pump architecture of the Tm ion enables high optical-to-optical efficiency while pumping at around 800 nm. High thermal conductivity of the Lu₂O₃ host supports operation at high-average power. The ceramic nature of the Lu₂O₃ host overcomes the scalability limits of single crystal sesquioxides.

Future astrobiology missions will focus on planets with significant astrochemical or potential astrobiological features, such as small, primitive bodies and the icy moons of the outer planets that may host diverse organic compounds. We have made significant progress in the laser desorption/ionization mass spectrometry area with advancement in the two-step laser tandem mass spectrometer (L2MS) instrument to deconvolve complex organic signatures. In this paper we will describe our development effort on a new laser architecture for the L2MS instrument. The laser provides two discrete mid-infrared and ultraviolet wavelengths on a single laser bench with a straightforward path toward space deployment.

We present the results of a three-year operational-aging test of a specially designed prototype flight laser operating at 1064 nm, 10 kHz, 1ns, 15W average power and externally frequency-doubled. Fibertek designed and built the q-switched, 1064nm laser and this laser was in a sealed container of dry air pressurized to 1.3 atm. The external frequency doubler was in a clean room at a normal air pressure. The goal of the experiment was to measure degradation modes at 1064 and 532 nm separately. The external frequency doubler consisted of a Lithium triborate, LiB₃O₅, non-critically phase-matched crystal. After some 1064 nm light was diverted for diagnostics, 13.7W of fundamental power was available to pump the doubling crystal. Between 8.5W and 10W of 532nm power was generated, depending on the level of stress and degradation. The test consisted of two stages, the first at 0.3 J/cm² for almost 1 year, corresponding to expected operational conditions, and the second at 0.93 J/cm² for the remainder of the experiment, corresponding to accelerated optical stress testing. We observed no degradation at the first stress-level and linear degradation at the second stress-level. The linear degradation was linked to doubler crystal output surface changes from laser-assisted contamination. We estimate the expected lifetime for the flight laser at 532 nm using fluence as the stress parameter. This work was done for NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) LIDAR at Goddard Space Flight Center in Greenbelt, MD with the goal of 1 trillion shots lifetime.

Optical systems of modern high-power lasers require control of irradiance distribution: round or square–shaped flat-top or super-Gaussian irradiance profiles are optimum for amplification in MOPA lasers and for thermal load management while pumping of crystals of solid-state ultra-short pulse lasers to control heat and minimize its impact on the laser power and beam quality while maximizing overall laser efficiency, variable profiles are also important in irradiating of photocathode of Free Electron lasers (FEL). It is suggested to solve the task of irradiance re-distribution using field mapping refractive beam shapers like piShaper. The operational principle of these devices presumes transformation of laser beam intensity from Gaussian to flat-top one with high flatness of output wavefront, saving of beam consistency, providing collimated output beam of low divergence, high transmittance, extended depth of field, negligible residual wave aberration, and achromatic design provides capability to work with ultra-short pulse lasers having broad spectrum. Using the same piShaper device it is possible to realize beams with flat-top, inverse Gauss or super Gauss irradiance distribution by simple variation of input beam diameter, and the beam shape can be round or square with soft edges. This paper will describe some design basics of refractive beam shapers of the field mapping type and optical layouts of their applying in optical systems of high-power lasers. Examples of real implementations and experimental results will be presented as well.

We report on a Yb:YAG laser amplifier for ultrashort pulse applications at kW-class average power. The laser uses two large-aperture, disk-type gain elements fabricated from composite ceramic YAG material, and a multi-pass extraction architecture to obtain high gain in a chirped-pulse amplification system. The disks are edge-pumped, thus allowing for reduced doping of the host material with laser ions, which translates to lower lasing threshold and lower heat dissipation in the Yb:YAG material. The latter makes it possible to amplify a near diffraction-limited seed without significant thermo-optical distortions. This work presents results of testing the laser amplifier with relay optics and passive polarization switching configured for energy extraction with up to 40 passes through the disks. Applications for the ultrashort pulse laser amplifier include producing a laser-induced plasma channel, laser material ablation, and laser acceleration of atomic particles.

A Tm/Ho co-doped mode-locked soliton fiber laser design is presented with stable and low noise single-pulsing operation at a repetition rate of 135.2 MHz and a transform limited pulse duration of 375 fs. The fiber laser is directly core pumped at a wavelength of 790 nm. In single-pulsing operation, the fiber laser is centered at a wavelength of 1983 nm and can be continuously tuned over an 8 nm bandwidth. The fiber laser consists of a linear cavity which allows scaling of the repetition rate further by reducing the cavity length and utilizing the high pump absorption at 790 nm and efficient absorption/emission dynamics without photodarkening. In addition, co-doping with Tm/Ho increases the efficiency of the lasing with enhanced cross-relaxation rates. Stable mode-locked operation with reduced ripples in the optical spectrum and high signal-to-background ratios in the RF spectrum is observed. A low relative intensity noise with an rms fluctuation level of 0.13 % (frequency interval of 10 Hz to 1 MHz) and a low phase noise with a timing jitter of 20 fs (frequency range of 100 Hz to 1 MHz) characterizes the mode-locked laser.

We numerically study the broadband mid-infrared supercontinuum generation in a non-uniform SF57 microstructured fiber. The dispersion of the fiber is tailored by linearly varying the air hole diameters along the propagation distance. The fiber has zero dispersion at two wavelengths. This allows a continuous shift of the higher zero dispersion wavelength to a longer wavelength. Results show this scheme can significantly broaden the generated spectrum.

The size reduction of a laser cavity is highly desirable during the process of designing a laser system, as it allows reducing the weight and size of the laser system as a whole, as well as increasing the robustness of the system’s operation under severe environmental conditions. This cavity length reduction should be achieved without sacrificing the output laser beam quality, especially in the far field region. One approach to reducing the laser cavity length is based on the selective generation of single higher order transverse radiation modes. We show that a single transverse mode generation is essential for producing high radiance, high beam quality far field distributions with short length laser cavities. In the past, the selection of a single high order transverse mode was performed by employing amplitude masks or localized, non-uniform pumping of the gain medium. Both approaches resulted in significant cavity losses, and an associated increase in the laser oscillation threshold, as well as a reduction in laser efficiency. In this work, we provide details of a “lossless” intra-cavity mode formation technique employing circular-shaped diffractive phase structures. The radial size of the diffractive structures can be optimized for the selection of specific transverse higher order laser cavity modes. We also define a lossless external-cavity transformation of the selected output transverse higher order laser cavity modes with diffractive phase plates that results in the formation of far field distributions containing high intensity on-axis peaks. Spatial characteristics of the transformed output laser cavity modes were analyzed, including encircled beam powers, as well as encircled power M² functions. Results of this work can be applied to reducing cavity lengths of various laser systems.

Specifically optimized for both high efficiency and low SWaP, DILAS Diode Laser, Inc. continues to improve and optimize high-brightness fiber-laser pump modules. Starting with a <53% electrical-optical efficient 330W module in full production, power-scaled versions capable of 625 W and 900 W will also be covered. Utilizing a 225um/0.22 NA fiber output, these pumps enable single-mode kW-class fiber amplifiers ranging from 1 kW to 3kW. Designed for low SWaP, these modules are produced using mounted diode laser bars from a standard manufacturing line and commercial, off-theshelf optics. Cooling is accomplished through macro channel coolers that eliminate the need for micro-channels and the associated coolant issues. This innovative macro channel cooler is specifically designed to reduce both weight and thermal resistance, and also provides an ideal substrate for power-scaling the diode module while maintaining efficiency. Utilizing AuSn hard solder on CTE matched substrates eliminates the problems associated with Indium-based diode solder joints and permits hard pulsing of the laser diodes with any pulse width/duty cycle parameter set. Optional VBG stabilization is available on all versions for applications requiring wavelength stability over a wide temperature range.

Targeted at the 793nm absorption band, DILAS Diode Laser, Inc. offers a range of products specifically designed for Thulium fiber laser pumping, spanning from 12 W to <300W of pump power and coupled into fiber sizes starting at 105um and upwards. A variety of different diode architectures are utilized, ranging from single-emitters, conduction-cooled bars, and DILAS's T-bar structure extended to the 793nm range, resulting in a wide variety of power levels and packaging options to support different applications. As IRCM for airborne platforms is a major application for Tm fiber lasers, packages optimized for low SWaP will be presented, which utilize a combination of the T-bar structure and macrochannel coolers specifically designed for compact, lightweight applications. Examples and results of Tm fiber lasers pumped using DILAS diodes will also be presented and discussed.

Laser diodes fabricated from the AlGaInN material system is an emerging technology for defence and security applications. The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well, giving rise to new and novel applications including displays and imaging systems, atomic clock and quantum information, free-space and underwater telecom and lidar.

We are currently developing a laser transmitter to remotely measure Sodium (Na) by adapting existing lidar technology with space flight heritage. The developed instrumentation will serve as the core for the planning of a Heliophysics mission targeted to study the composition and dynamics of Earth’s mesosphere based on a spaceborne lidar that will measure the mesospheric Na layer. We present performance results from our laser transmitter development effort with emphasis on wavelength tuning and power scaling of a diode-pumped Q-switched self-Raman c-cut Nd:YVO₄ laser with intra-cavity frequency doubling that could produce multi-watt 589 nm wavelength output. We will review technologies that provide strong leverage for the sodium lidar laser system with strong heritage from past and current space flight missions.

Lasers intended for application to man-portable and hand-held laser target designators are subject to significant constraints on size, weight, power consumption and cost. These constraints must be met while maintaining adequate performance across a challenging environmental specification. One of the challenges of operating a Nd³⁺:YAG laser over a broad ambient temperature range is that of diode-pump-tuning. This system is specified to operate over an ambient temperature range of –46°C to +71°C, and the system electrical power consumption requirements preclude active temperature control. As a result the laser must tolerate a 32.8nm pump wavelength range. The optical absorption of Nd³⁺:YAG varies dramatically over this wavelength range. This paper presents a laser that minimizes the effect of this change on laser output. A folded U-shaped geometry laser resonator is presented, made up of a corner cube at one end and a plane mirror substrate at the other. The action of the corner cube coupled with this configuration of end mirrors results in a resonator that is significantly less sensitive to misalignment of the end mirror and/or the corner cube. This Ushaped resonator is then further folded to fit the laser into a smaller volume. Insensitivity of this compact folded resonator to mirror misalignments was analyzed in Zemax via a Monte-Carlo analysis and the results of this analysis are presented. The resulting laser output energy, pulse duration and beam quality of this athermally pumped, misalignment insensitive folded laser resonator are presented over an ambient temperature range of –46°C to +71°C.

A selection of 2 μm lasers and amplifiers developed at the CSIR National Laser Centre in South Africa is presented. A diverse range of near diffraction-limited 2 μm lasers and amplifiers were developed which varied from high-energy, single-frequency oscillators and amplifiers, to compact and efficient MOPA systems delivering high average powers. This was made possible by exploiting various advantageous properties of holmium-doped YLF while mitigating its detrimental properties through the use of novel pump and laser design approaches.

The actual combat effectiveness of weapon equipment is restricted by the performance of Inertial Navigation System (INS), especially in high reliability required situations such as fighter, satellite and submarine. Through the use of skewed sensor geometries, redundant technique has been applied to reduce the cost and improve the reliability of the INS. In this paper, the structure configuration and the inertial sensor characteristics of Skewed Redundant Strapdown Inertial Navigation System (SRSINS) using dithered Ring Laser Gyroscope (RLG) are analyzed. For the dither coupling effects of the dither gyro, the system measurement errors can be amplified either the individual gyro dither frequency is near one another or the structure of the SRSINS is unreasonable. Based on the characteristics of RLG, the research on coupled vibration of dithered RLG in SRSINS is carried out. On the principle of optimal navigation performance, optimal reliability and optimal cost-effectiveness, the comprehensive evaluation scheme of the inertial sensor configuration of SRINS is given.

High power, high energy pulsed fiber laser with precise control of individual pulse width and wavelength is an enabling source for coherent imaging and communication applications. Here a turn-key 1550 nm PM fiber amplifier generating 22 μJ pulse energy with near transform limited linewidth (600 MHz) is presented. Individual pulse wavelengths and pulse widths can be controlled with 30-120 pm wavelength separation and 2-10 nsec pulse width. The 22 W average power laser, based on COTS Er and ErYb doped LMA PM-fibers is optimized for high peak power (< 4 kW), low duty cycle (~0.1%) operation while maintaining diffraction limited beam quality (M² < 1.1). High wall plug efficiency (<10%) for the FPGA controlled system is maintained by temporal and spectral ASE suppression. Pulse energies are limited by Stimulated Brillion Scattering and Four Wave Mixing. Dependence of the fiber nonlinearities on pulse width and wavelength separation is characterized.

Fiber optic systems are deployed in a variety of settings as strain sensors to locate small disturbances along the length of the optical fiber cable, which is often tens of kilometers long. This technology has the advantages of low cost and design simplicity, as the sensor is its own source of telemetry and may be easily repaired or replaced. One of the limitations of current technology is noise from optical backscatter events in the fiber resulting in a degraded signal in individual spatial zones leading to signal fading. Detection within these zones along the length of the fiber is then obscured. Signal multiplexing may be used to increase sensitivity and signal-to-noise ratio and reduce signal fading. In such an architecture, multiple channels are multiplexed together and transmitted along the fiber. In this article, we report on results from two different systems that were tested using such techniques. Results are then compared with a single channel system.