We report 3.8-5.0 μm tunable three-stage double-pass Fe:ZnSe solid-state MOPA with approximately 30-fold overall amplification coefficient operating at RT and pumped by EO Q-switched Cr:Er:YSGG laser system radiation. EO Q-switched Cr:Er:YSGG MOPA with the Q-switch based on a La3Ga5SiO14 crystal providing 90 ns pulses with energy up to 350 mJ at a 3 Hz repetition rate was used as a pump source. The maximum output energies of Fe:ZnSe system in 90 ns pulses exceeded 55 mJ at 4.4 μm under 220 mJ of pumping. The pulse jitter was measured to be ⪅8 ns and was limited by the Er:Cr:YSGG laser jitter.
We report on developing two flashlamp-pumped electro-optically Q-switched Cr:Er:YSGG lasers with the Q-switch based on La3Ga5SiO14 crystal. The “short” laser cavity was optimized for applications requiring high peak power. In this cavity, the 300 mJ output energy in 15 ns pulses at 3Hz repetition rate was demonstrated under pump energy below 52 J. However, several applications, such as Fe:ZnSe pumping in a gain-switched regime, requiring longer (~ 100 ns ) pump pulse duration. We developed a 2.9 m long laser cavity capable of delivering 190 mJ of output energy in 85 ns pulses for these applications.
Flashlamp pumping of heavily doped Er:YAG is an economical method of obtaining relatively high pulse energy and average power for medical and other applications. We will present results from our investigation into the effects of gain media configurations, resonator geometries, and operating parameters on energy per pulse, slope efficiency, thermal lensing, and beam divergence.
Metastable intermolecular composites (MIC) consisting of nanometer-scale aluminum and molybdenum trioxide have been proposed as fast initiators. A compound of this class of material was evaluated as a potential environmentally friendly replacement pyrotechnic material for lead styphnate for use in the primer of the M230 medium-caliber automatic cannon. In addition to removing the lead hazard, laser ignition would also reduce or remove certain hazards due to electrostatic or radio frequency radiation. This study was conducted with both a flashlamp-pumped Nd+3:YAG laser and a fiber-coupled diode laser. The measured threshold ignition energies of the MIC and two other inorganic pyrotechnic compounds are presented. The low ignition threshold, advances in diode laser technology, and compact size of the diode laser indicated that laser diode technology could be an ideal candidate ignition source for the M230 cannon. The candidate pyrotechnic compounds were also evaluated for suitability in laser initiation via measurement of time-to-first-light. This metric provided a measurement of the potential for achievement of the necessary action time required for proper cannon operation.
Medium caliber cannons, such as the Army's M230 chain gun, currently utilize a high current electrical pulse to initiate the propellant. While electrical ignition is reliable, electrical based primers are susceptible to premature ignition from EMI, EMP, or other stray or directed electromagnetic sources. Laser ignition of medium-caliber cannon systems has several advantages over the current electrically initiated ignition system. In addition to removing hazards due to electrostatic or radiated electromagnetic energy, lasers are an ideal ignition source for new primer compounds, such as Metastable Intermolecular Composites (MIC), that are potentially environmentally friendly replacements for lead styphnate containing compounds. This paper will describe our efforts to develop a laser source suitable for the M230 medium-caliber automatic cannon as used on the Apache AH-64 helicopter. We will describe early proof of concept laser systems including a fiberoptic-coupled flashlamp-pumped Nd:YAG source, direct Nd:YAG laser sources, and a full rate of fire demonstration laser that was mounted directly on the M230 housing. We will also discuss our plans and designs for a direct semiconductor laser ignition source for the M230.
A miniature diode pumped Er,Yb:glass laser has been developed at the Night Vision and Electronic Sensors Directorate, U. S. Army CECOM (NVESD) for soldier applications. This device uses a single laser diode at 925 nm to end pump a 200µm x 3 mm volume of Er,Yb:glass gain media. A Co2+:MgAl2O4 passive Q-switch is used to produce 2 nanosecond pulses at a repetition rate from single shot to 20 Hertz. A nominal pulse energy of 100 microjoules is emitted, corresponds to a peak power of 50 kilowatts, which is sufficient for ranging to over 2 kilometer. The Eyesafe Microlaser was designed and demonstrated to operate over a wide temperature range without temperature control of the pump laser, a feature important for soldier applications. An desirable feature of Er,Yb:glass lasers is that they emit directly at 1.54 microns, which is important for eye safe operation and low cost fabrication.
Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper presents a review of a multifunction laser radar system developed and tested for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.
Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper is the second in a series of papers describing the progress toward a multifunction laser radar system under construction for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.
Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper presents a review of a multifunction laser radar system under construction for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.
BBO is a popular nonlinear optical crystal typically used for frequency conversion. Recently, BBO was also used as electro- optic Q-Switch material. BBO was chosen as a good candidate material for use as an E-O Q-Switch for Er:Glass lasers because of its low insertion losses at 1.54 micrometer and high laser damage threshold (5GW/cm2, 10 ns). Traditional materials such as KD*P or LiNbO3 exhibit high insertion losses and/or low damage thresholds at 1.54 micrometer. As an added benefit, BBO does not exhibit a piezoelectric effect. All of these advantages make BBO an attractive Er:Glass E/O Q- switch for high peak and high average power applications.
A high repetition rate 10Hz diode side pumped erbium glass laser transmitter for rangefinder and radar applications was demonstrated. Without cooling it was operated at 10Hz for more than 30 seconds. With forced air it was run continuously at 10Hz with an output of 5-10mj and 25-30nsec pulsewidth.
Physical, spectral and laser properties of anew Yb3+ doped phosphate laser glass, QX/Yb, has been developed. This glass exhibits a low thermal expansion coefficient and a negative temperature coefficient of refractive index, resulting in an acceptable athermal behavior and an excellent thermal loading capability. The peak absorption and emission cross sections of Yb3+ were measured to be 1.06 X 10-20 cm2 and 0.903 X 10-20 cm2, respectively. The concentration quenching and the influence of the OH- content on fluorescence lifetimes were examined. Excellent laser performance with a slope efficient of 49 percent and a maximum output power of 400 mW was demonstrated.
The various aspects of erbium glass laser characteristics were carefully examined, including the influences of pumping pulsewidth, dopant concentration, output wavelength, relaxation oscillation and energy transfer processing between Yb3+ and Er3+.
The basic research and engineering work for developments of eyesafe radar transmitter are reviewed. The characteristics of two model transmitters are introduced. Laser output at 1.54 micrometers with 5 mJ of energy and a 60 ns pulse width was demonstrated at 15 Hz using a rotating prism Q-switch. The laser media is an experimental Er:Glass, designated QX/ER.
Basic laser performance data for the 4F3/2 - 4I13/2 transition of Nd3+ in phosphate, silicate, and germanate glasses with various doping concentrations are presented. A slope efficiency of 1.1% was achieved in Q-100 phosphate laser glass. The resonator loss analysis indicates that there is no significant excited state absorption at 1.355 micrometer for phosphate glasses. Simultaneous operation of both the 4F3/2 - 4I13/2 and the 4F3/2 - 4I11/2 transitions of Nd3+ in phosphate, silicate, and germanate glasses have been achieved using two different methods. Laser output from these two transitions demonstrate good temporal and spatial overlap under the tested conditions.
Significant enhancement of the thermal loading capability has been achieved with both Er3+ and Nd3+ doped inherently strong glasses by an ion-exchange chemical strengthening process. A free running laser with an average output power of 6.5 W and a Q-switched single mode laser with an energy of 5 mJ at a repetition rate of 15 Hz have been demonstrated at the 1.54 micrometers eye safe wavelength with strengthened QX/Er glass. An average output power of 110 W at 1.05 micrometers has been obtained employing a strengthened QX/Nd glass rod.
Divalent uranium doped CaF2 Q-switch has been tested as a saturable absorbing Q-switch. Laser output at 1535 nm with 10 mJ of energy and a 60 ns pulse width was demonstrated at 8.5 Hz by using U2+:CaF2 as a saturable absorbing Q-switch. The laser media is QE7S and experimental Er:glass, designated QX/ER.
New erbium doped glass base compositions and sensitizer ion concentrations have been investigated. Laser, spectral, and thermo-mechanical properties have been tested. This study has resulted in a new erbium doped phosphate laser glass that exhibits improved thermal shock resistance and superior laser performance.
Many applications exist for eye safe laser operating at high repetition rates. This paper will discuss the operation of Q-switched Er:glass lasers at high repetition rates with peak powers in the megawatt range.
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