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New Monocrystals with Rare Earthes

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Development of a Technology of Growing New Single Crystalline Media on the Basis of Rare Earth Scandium Borates - Er, Yb:LSB, Pr:LSB, Pr, Er, Yb: LSB for 1.56 mkm Diode Pumped Lasers and a New Polyfunctional Crystal Nd:CSB Possessing the Properties of an

Tech Area / Field

  • MAT-SYN/Materials Synthesis and Processing/Materials
  • PHY-OPL/Optics and Lasers/Physics

Status
3 Approved without Funding

Registration date
27.01.1999

Leading Institute
NPO Firn, Russia, Krasnodar reg., Krasnodar

Collaborators

  • Universität Hamburg / Institut für Laser Physik, Germany, Hamburg\nBremlas Lasertechnik Bremen GmbH, Germany, Bremen

Project summary

On the basis of crystalline host of lanthanum scandium borate (LaSc3(BO3)4 — LSB), doped with Er, Yb ions SPA «Firn» has developed a single crystalline medium for diode pumped lasers radiating in the vicinity of 1.56 mm. First generation tests in a continuos wave mode pumped by 3.5 W diode laser radiation allowed to reach 150 mW of stimulated radiation power. Slope efficiency was 10%. This is the first host showing such high energy parameters. Obtaining 1 W output power and higher in CW mode on Er,Yb:LSB crystals is technically possible but it requires both additional optimization of the crystal concerning Er-Yb dopants and perfection of the technology of growth of optically homogenous crystals.

Passive Q-switches using the effect of spectroscopic saturation are used for pulse mode of operation of 1.5 mm lasers. Such Q-switches for the 1.5-1.6 mm region are known - Er:CaF2, U:CaF2, Co:ZnSe. However, crystalline hosts on the basis of fluorides are hygroscopic and crystalline hosts on the basis of chalcogenides have low laser damage threshold (1 MW/cm2).

It is possible to make a passive Q-switch without mentioned drawbacks operating in the 1.56 mm region on the basis of lanthanum scandium borate doped with praseodymium (Pr:LSB). Pr:LSB single crystal has a wide absorption peak in the 1.4-1.6 mm region stipulated by electron transitions from ground state 3H4 to an excited state 3F3. Preliminary experimental evaluations of the density of power of spectroscopic saturation for the said transition give a value of about 1 MW/cm2.

The proposed new single crystalline medium Pr:LSB will serve a passive Q-switch for 1.56 mm lasers and the new single crystalline medium Pr,Er,Yb:LSB will combine the functions of an active medium for a 1.56 mm laser with a passive Q-switch.

Many scientific centers are experimenting with polyfunctional laser media of the «two-in-one» type which combine the properties of an active and non-linear media in one laser elements. Creation of such media is a step to a new generation of optical devices. Cerium scandium borate doped with neodymium developed in SPA «Firn» is one of such new active-non-linear media.

In the experiments with active-non-linear element Nd:CSB oriented for SHG process of oo—>e type second harmonic generation obtained as a result of self frequency doubling of stimulated radiation had power 4 mW (diode pumping power - 0.7 W) . Taking into consideration the fact that experimentally measured value of the effective non-linear susceptibility in Nd:CSB crystal is 1.8ґ10-12 m/V we may state that the obtained power is by an order lower than the expected one. This is stipulated by the fact that optical quality of the Nd:CSB as a non-linear element is not satisfactory which is, probably, a result of defects of crystalline lattice where a displacement of atoms from their positions in one tightly packed layer or a group of layers takes place. As it follows from model calculations in realization of scalar SHG or self frequency doubling of stimulated radiation on optically homogeneous crystals conversion efficiency into the second harmonic increases by more than an order. That’s why searching compositions for growing high quality Nd:CSB crystals seems to be a topical problem.

Continuation of the works in the sphere of investigation of properties and perfection of the technology of growing rare earth scandium borate single crystals allows to create a new element basis for diode pumped lasers radiating in the 1.56 and 0.53 mm and will result in simplification of diode pumped laser designs and make them commercially available.

The companies which have agreed to participate in the Project will receive samples of the grown crystals for more detailed optical and generation tests with the purpose of evaluation of perspectivity of their use in diode pumped lasers on the basis of the new media developed under the Project.


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