This paper examines several characteristics and phenomenon associated with the optimization of diode pumped erbium ytterbium glass microlasers. Test results indicate that within an erbium ytterbium glass gain element, the excited erbium (laser) ion effective pump depth is larger than the excited ytterbium (sensitizer) ion effective pump depth. Designed specifically for diode pumping, JD phosphate laser glass host material exhibits high rare earth and sensitizer ion solubility. This enhanced doping capability allows the JD glass to be used in a variety of diode pump architectures that are not possible with most conventional crystal & glass laser materials. Our study has shown that new small gain element composite laser glass architectures & designs may be made used to more efficiently capture, contain and uniformly distribute the diode laser pump light. We expect this work to will lead to the next generation of high peak & average power "eye-safe" diode pumped microlasers for use in rangefinding, imaging, illumination tracking and targeting applications.
Ytterbium only and erbium-ytterbium co-doped phosphate glass Double Clad (DC) cladding pumped Large Mode Area (LMA) core fibers are manufactured at Kigre by the “rod-in-tube” method. The ytterbium and erbium doping concentration levels in phosphate glass are as much as two orders of magnitude higher than the doping concentrations found in fused silica fiber manufactured by Modified Chemical Vapor Deposition (MCVD) method. The background loss of the fiber’s core and cladding measured ~ 0.01 dB/per cm at 1310nm. The measured absorption coefficient at 974 nm is 0.3 dB/per cm for the ytterbium-erbium co-doped fiber. Greater than 4.6 Watts CW laser output was demonstrated from the Er:Yb:glass fiber at 1535nm with a 37.4% slop efficiency and 36.3% optical efficiency. The Yb:glass fiber produced a maximum output power of 1.6 Watts in a 14cm gain length.
Kigre is developing new rare-earth-doped glass fiber laser materials specifically for use in multiple clad and multiple core LMA and super mode (guided wave) fiber laser constructs. In this work we describe new end-pump double clad fiber laser designs fabricated from high performance phosphate laser glass compositions. One DC LMA fiber is doped with erbium/ytterbium for 1.54μm laser emission. Another DC LMA fiber is doped with ytterbium for 1.03μm laser emission. A third DC multiple core "supermode" fiber is doped with neodymium for 1.053μm laser emission. Initial fiber laser performance data is presented. The rebium/ytterbium & ytterbium only doped fibers are end-pumped at 940/975nm with 40-Watt fiber coupled laser diodes. The neodymium-doped fiber is end-pumped with an 808nm 40-Watt fiber coupled laser diodes. Design and performance data for new side-pumped, highly doped phosphate DC LMA fiber laser architectures are presented.
Phosphate glasses are attractive laser oscillator/amplifier materials because unlike fluoride, silicate, and other laser glass materials it combines attractive properties such as good chemical durability, ion-exchangeability, high gain, low concentration quenching, and low upconversion losses. Phosphate glasses also exhibit very high solubility for rare earth ions. This feature permits the introduction of large concentrations of active ions into relatively small volumes resulting in smaller laser devices with high-energy storage capabilities. These high dopant concentrations also result in very rapid and efficient energy transfer between rare earth ions. This allows for the effective use of Yb3+ as a sensitizer for the Er3+ laser ion.
Effective Er:Yb:Glass pumping, energy storage, and energy extraction involves the population of the 2F5/2 level of Yb3+ (~2ms fluorescence lifetime) and transferring energy to the 4I11/2 level of Er3+ (~500μsec transfer time); and a very rapid (< 1μsec) nonradiative decay of the Er3+ from the 4I11/2 state (with an 8ms fluorescence lifetime). In this study we measured the fluorescence lifetime for the 4I13/2 level of Er+3 on different glass samples with various concentrations of erbium. The data indicates that for doping levels up to 7% (wt.%) Er2O3 the lifetime remains above 7.0ms. Theoretically, this highly doped glass may produce greater than 20dB gain in 1cm path length.
In additional fluorescence lifetime testing, ytterbium doped and erbium/ytterbium co-doped glasses samples were evaluated for concentration quenching and energy transfer rate as function of the Er3+ concentration rates. The effect on teh energy transfer efficiency and laser efficiency was analyzed.
We established a new diode array pumped Er:Yb:Glass test setup for evaluation of the laser performance and q-switch characteristics of various saturable absorber materials at 1.54micrometers . Pumping distribution and maximum gain was analyzed. Passive q-switched laser operation was demonstrated with both U2+:CaF2 and CO2+:MgAl2O4. TEMoo Q-switch pulses with energy of 0.5mJ and pulse width of 10ns was obtained.
We established a new diode array pumped Er:Yb:Glass test setup for evaluation of the laser performance and q-switch characteristics of various saturable absorber materials at 1.54um. Pumping distribution and maximum gain was analyzed. Passive q-switched laser operation was demonstrated with both U2+:CaF2 and Co2+:MgAl2O4. TEMoo Q-switch pulses with energy of 0.5mJ and pulse width of 10ns was obtained.
High power, high brightness fiber lasers have numerous potential commercial and military applications. These lasers offer unique flexibility as they may be coherently combined to provide a potential multi-kilowatt laser source and integrated delivery system. Fiber lasers with cladding pump designs represent a new generation of diode pumped configurations that are extremely efficient, have single mode output and may be operated with or without active cooling. They have a number of novel or unusual attributes, stemming from the fact that they represent the extreme case of a long gain length thin laser cavity. Reports indicate that over 100 watts of TEMoo CW output power are readily demonstrated from current cladding pumped fiber laser designs.
Passive Q-Switch characteristics of Co2+:MgAl2O3 sample were evaluated in a diode pumped QX/Er Erbium glass laser at 1535 nm, a flashlamp pumped Nd:YAG laser at 1.44 micrometers and Nd3+:KGd(WO4)2 laser at 1.34 micrometers .
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.
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.
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.
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.
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.