Compositional Tuning of Photoluminescence Properties in Nd-Doped YAG YSGG Mixed Structures

IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 42, NO. 6, JUNE 2006 563

Compositional Tuning of PhotoluminescenceProperties in Nd-Doped YAG–YSGG

Mixed StructuresAlberto Anedda, Carlo Maria Carbonaro, Daniele Chiriu, Pier Carlo Ricci, Mahmoud Aburish-Hmidat,

Maurilio Guerini, Pier Giorgio Lorrai, and Emery Fortin

Abstract—The photoluminescence (PL) properties ofneodymium-doped yttrium aluminum garnet and yttriumscandium gallium garnet mixed structures were investigated as afunction of the relative concentration of the two garnets. The blueshift of the emission bands in the 930–950-nm range is ascribedto compositional tuning effect. An analytical model to estimatethe variation of the PL position as a function of the compositionalhost structure is proposed.

Index Terms—Compositional tuning, mixed garnet, photolumi-nescence, yttrium aluminum garnet (YAG), yttrium scandium gal-lium garnet (YSGG).

I. INTRODUCTION

THE development of new solid-state lasers, especiallythose operating from 0.9 to 3.0 m, has renewed general

interest in the optical properties of rare-earth ions ingarnet structure [1]–[3]. The energy levels of severalions inserted as dopants in different garnet compounds, likeyttrium aluminum garnet (YAG) or yttrium scandium galliumgarnet (YSGG), were successfully analyzed over the pastyears [4], [5]. Neodymium-doped YAG, for example, is oneof the most important available laser systems for researchand technological applications. The prospective of enhancingefficiency and tunability of solid-state lasers boosted the studyof new materials able to meet specific technological purposes.Among the possible sources, mixed garnet host materials, likeY Al O (YAG), Y Sc Ga O (YSGG), Gd Sc Ga O(GSGG), and Y Sc Al O (YSAG), doped with lanthanidesallow the so-called compositional tuning. By changing thematerial composition, the lattice parameters can be modifiedleading to a variation of the strength of the crystal field. Asa consequence, the emission wavelengths of a selectedion can be tuned at request. Recently, Walsh et al. obtainedover 100 mJ at 0.9441 m in the -switched mode from

Manuscript received August 4, 2005; revised February 23, 2006.A. Anedda is with the Diparimento di Fisica and the Laboratorio Laboratorio

Interdisciplinare di Microscopie e Nanoscopie, Università di Cagliari, CittadellaUniversitaria, I-09042 Monserrato, Italy (e-mail: [email protected]).

C. M. Carbonaro, D. Chiriu, and P. C. Ricci are with the Diparimentodi Fisica, Università di Cagliari, Cittadella Universitaria, I-09042 Monser-rato, Italy (e.mail: [email protected]; [email protected];[email protected]).

M. Aburish-Hmidat, M. Guerini, and P. G. Lorrai are with Scientific MaterialsEurope, I-08048 Tortolì, Italy (e-mail: [email protected]).

E. Fortin is with the Department of Physics, University of Ottawa, Ottawa,ON K1N 6N5, Canada (e-mail: [email protected]).

Digital Object Identifier 10.1109/JQE.2006.874061

Nd:YAG YSAG [6]. One of the main applicationsof mixed garnet materials is related to the remote sensing ofthe atmosphere. As an example, light detection and ranging(LIDAR) or differential absorption lidar (DIAL) techniques canbe applied to determine molecular constituent concentrationspresent in the atmosphere, such as water vapor H O [7].The possibility of tuning the laser system to the right wave-length and investigating the desired molecule easily explainsthe growing interest in compositional tuning of mixed garnetmaterials [8], [9].

In case of the mixed structure from Y Al O (YAG) andY Sc Ga O (YSGG) garnets, Ga occupies tetrahedral sites,Sc is in octahedral positions, and Al can occupy both tetrahedraland octahedral sites. These mixed structures, doped with Nd ,generates a blue shift in the photoluminescence (PL) emissionof Nd with respect to the observed emission of the ion inYAG [10]. The aim of this paper is to investigate the PL emissionof Nd in samples with the mixed structure YAG YSGGas a function of the concentration of YSGG. An analytical modelto estimate the variation of the PL position as a function of thecompositional host structure is proposed.

II. EXPERIMENTAL SETUP AND SAMPLES

PL measurements were performed with a single-pass spec-trometer (Dilor XY800). An argon ion laser operating at514.5 nm (Coherent Innova 90C-4) provided the excitation.The signal, dispersed with a 600-grooves/mm grating, wasdetected by a 1024 256 LN2 cooled charge coupled detector(CCD). All PL measurements were performed at room temper-ature with a spectral resolution of 0.1 nm.

Mixed garnet samples, doped with 1% at. of Nd, were grownby Scientific Materials Europe, Tortolì, Italy, by the Czochralskimethod with a different composition of YAG YSGG hostmaterials. The stoichiometric term was used as a simplifica-tion of the formula Y Al Sc Al Ga O and it repre-sents the relative concentration of Al, Sc, and Ga in the melt.The stoichiometric composition of samples was controlled bychanging the amount of Ga O and Sc O oxides in the meltin order to obtain the desired relative concentration of YAGand YSGG. Table I summarizes the compositional structure ofanalyzed samples. Prime oxides of Al O , Y O , Ga O , andSc O (all with 99.999% purity) were mixed and pre-sinteredunder pressure of 140 MPa and processed at 1400 C for 24 h.Sintered tablets, with a first composition of YAG YSGG ,were melted at 1970 C in iridium crucible and pulled at 0.8

0018-9197/$20.00 © 2006 IEEE

564 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 42, NO. 6, JUNE 2006

TABLE IRELATIVE MATERIAL COMPOSITIONS AND RESULTS OF VOIGT PROFILE FITTING. ENTRIES BELONGING TO PURE YAG AND

SAMPLES A–G WERE ANALYZED IN THIS STUDY, WHILE THE REMAINING ENTRIES BELONG TO SAMPLES FROM [6]

mm/h with r/min in an Ar atmosphere. The obtainedundoped boule was used as a seed for pulling an Nd-doped melt.

III. RESULTS AND DISCUSSION

InFig.1, thePLspectrumofNd:YAGin the860–950-nmrangeis compared with the spectra of samples with mixed composition.It is worth noting that the emissions in mixed structures cannotbe related to separate contributions of Nd:YAG and Nd:YSGG[10], excluding the presence of separated phases of different gar-nets. Due to the broadening and overlapping of the PL bands inthe 860–920-nm region, the analysis of the PL modifications, asthe relative concentration of YSGG in the mixed structure in-creases, was performed on the luminescence peaks at 946 and938 nm. It is well known that the observed bands in Nd:YAG inthe 860–950-nm range involve the stark components ofthe manifold and the stark components of the fun-damental level [1]. The and transitions(946 and 938.5 nm) of Nd:YAG were considered as referencesto estimate the wavelength shift and band broadening of the an-alyzed samples as a function of YSGG concentration (Fig. 2). Itcan be observed that the compositional variation of the host ma-terials shifts toward the blue region, the Nd emission bandsof about 3 nm, as summarized in Table I. In addition, the fullwidth at half maximum (FWHM) of the analyzed bands increasesas the YSGG relative concentration approaches 0.5; above thisthreshold, the PL-FWHM decreases as the YSGG relative con-centration increases (Table I). The inset of Fig. 2 shows the varia-tion of the peak position for the and transitionsas a function of the doping process: the rigid blue shift of bothemissions, at least within the experimental error, allows to hy-pothesize that the compositional tuning is related to the variationof the energy position of the ground level .

The luminescence properties of Nd ions in the YAG host inthe range from 750 to 1100 nm are well known. In this region,the emission bands are due to the recombinations betweenand stark components of the level and the

stark components of the fundamental level or to the YY stark components of the level [11]. The PL spectrumof Nd:YAG in the spectral range of 860–910 nm is comparedto that of a mixed-structure sample (sample A in Table I) inFig. 3. The spectrum of sample A was deconvoluted by means ofVoigt profiles, assuming the spectral properties of the Nd:YAGsample as references. The fitting curve reproduces very well theexperimental data, confirming the previously discussed mixednature of the investigated structures. Voigt profiles of the emis-sion bands were chosen because of the mixed contribution ofhomogeneous and inhomogeneous broadening of the spectrallines. It is well known that a physical process that has the sameprobability of occurrence for all the atoms in the system pro-duces a Lorentzian line shape (homogeneous broadening), whilea physical process that has a random distribution of occurrencefor each atom produces a Gaussian line shape (inhomogeneousbroadening). If both types of broadening processes are present,the line shape is the convolution of Lorentzian and Gaussiancontributions represented by a Voigt profile. The recombinationprocesses due to Nd levels in garnet structures strongly de-pend on the neighbor atoms and their contribution to the localcrystalline field [6], [12], suggesting the Voigt profile choice.The fitting procedure was successfully carried out on the

and recombination lines of each sample. Fitting pa-rameters are reported in Table I. Fig. 4 shows the Voigt profileFWHM of the transition as a function of the YSGG rel-ative concentration. The variation of the Voigt width indicatesthat the Gaussian and Lorentzian components, i.e., the homo-geneous and inhomogeneous broadening, depend on the YSGGconcentration. As reported in Fig. 4, the FWHM shows a max-imum at 50% of YSGG relative concentration. In these condi-tions, half of the Y sites of the elementary cells belongs tothe YSGG structure (A sites) and the other half belongs to theYAG structure (B sites). The dopant ions have a 50% probabilityto occupy both sites, causing the largest inhomogeneous broad-ening. If the YAG structure is predominant, the probability tooccupy B sites is higher, causing a decrease of FWHM because

ANEDDA et al.: COMPOSITIONAL TUNING OF PL PROPERTIES IN ND-DOPED YAG–YSGG MIXED STRUCTURES 565

Fig. 1. PL spectra of Nd:YAG and Nd:YAG YSGG mixed garnet at different ratios YSGG/YAG.

of the larger contribution of homogeneous behavior. The anal-ysis is confirmed by the variation of the Gaussian and Lorentzianwidths and , as functions of the YSGG relative con-centration (see the inset in Fig. 4). The Gaussian width increaseswith the increase of YSGG relative concentration and reaches amaximum when the relative concentration of YSGG is 0.5. Onthe contrary, the Lorentzian width decreases with an increaseof the YSGG relative concentration and shows a minimum atthe Gaussian width maximum. The analysis of the Voigt shapeparameter , defining the relative weight of a Lorentzian con-tribution to the linewidth with respect to a Gaussian one [6], is afurther confirmation of the just discussed broadening trend. Theequation describing the Voigt shape is given as

indicating the predominance of Gaussian orLorentzian nature of the emission band. The calcu-lated parameters are reported in Table I.

As shown in Figs. 1 and 2, and as previously discussed, theobserved emission bands are related to the transitions of Ndions hosted in the mixed garnet structure. The number of starkcomponents reported in the spectra is in good agreement withthe group theory and the stark effect analyzed by Kaminskii andPowell in Nd:YAG [10], [12]. The Hamiltonian of an ion in acrystal field is given by

(1)

where the first term, describing the interaction of each elec-tron with the nucleus, is the unperturbed Hamiltonian. The otherthree terms are treated as successive perturbations and describe,respectively, the Coulomb interaction of the electrons with each

566 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 42, NO. 6, JUNE 2006

Fig. 2. PL spectra of R � Z and R � Z transitions in different samples.A: Nd:YAG. B: Nd:YAG YSGG . C: Nd:YAG YSGG . Inset:peak position of the R �Z , R �Z transitions as a function of the dopingratio.

Fig. 3. PL spectrum of Nd:YAG and of the Nd:YAG YSGG mixedgarnet (sample A). The spectrum of the sample A was deconvoluted by meansof Voigt profiles.

other, the spin–orbit interaction, and the interaction of the elec-tron with the crystal field of the ligands. In the case of shielded

-electrons of trivalent rare-earth ions, the perturbations can betreated in the weak-field approximation where the strength ofthe crystal field is smaller than the Coulomb interaction of theelectrons with each other and the spin-orbit coupling interac-tion [10], [12]. The Stark splitting is due tothe local symmetry of the activator center related to the struc-ture of the host material, while the number of Stark componentsdepends on the quantum number in the weak-field approxi-mation. The garnet crystal structure belongs to the space group

Fig. 4. Voigt profile FWHM of theR �Z transition as function of the YSGGrelative concentration in the mixed garnet. The inset reports the widths of theLorentzian (�E ) and Gaussian (�E ) component of the Voigt profile as afunction of the YSGG relative concentration.

O , a body-centered cubic Bravais lattice and a memberof the cubic O crystal class [13]. The unit cell is composedof eight molecules of O [13]. Cations , , andhave, respectively, 8, 6, and 4 nearest neighbor oxygens, and aresituated at the , , and Wyckoff positions in the unitcell [13]. The position of the sites of the oxygen anions de-pends upon three more parameters , , and . The Yttrium ionsoccupy the sites and are surrounded by eight oxygen ions inthe shape of a distorted cube. The Nd ions occupy Y sitesin YAG and YSGG as isovalent substitutional defects. The sitelocal symmetry is and the Stark components related to thiscenter, for an electron in the configuration, are two and fivefor and , respectively [10], [12]. As previ-ously discussed, the deconvolution of the PL bands in sampleswith different YSGG relative concentration can be successfullyperformed assuming the PL spectrum of Nd:YAG as a reference.Thus, we can hypothesize that the symmetry related to the Ndions in these samples is the same as that of the sites in garnetswith symmetry and that it does not change as the YSGG con-centration increases. Therefore, the shift of the PL bands can beinterpreted by a variation of the crystalline field due to modifi-cations of the reticular parameters associated with the presenceof Sc and Ga atoms in and sites. The term , that describesthe crystalline field contribution in (1) can be expressed by ex-panding the crystalline field potential with spherical harmonics[12]

(2)

The subscript indicates the optical electrons and the areexpansion coefficients that depend on the specific lattice struc-ture giving rise to the local crystal field. In the case ofsymmetry, by assuming all the -charged ligand ions as point

ANEDDA et al.: COMPOSITIONAL TUNING OF PL PROPERTIES IN ND-DOPED YAG–YSGG MIXED STRUCTURES 567

charges, the electrostatic field at the sites occupied by Ndions is given by

(3)

where the standard multipole expansion has been used for[12]. In the present case, is somewhere near the central

ion and is the position of the th ligand. and are the polarcoordinates of the ligands and the distance . Bycomparing (2) and (3), one can obtain

and (4)

By assuming that the progressive introduction of Ga and Scatoms in the YAG elementary cell affects the crystalline fieldterm in (1), the energy eigenvalues of (1) can be expressed as

(5)

where the term indicates the “unperturbed” energy eigen-values before the introduction of Sc and Ga atoms andindicates the energy variation due to the modification aftertheir introduction. The energy variation can be expressed in dif-ferential form as

(6)

As previously discussed, Sc and Ga atoms occupy and sitesin garnet structure. The progressive introduction of Sc and Gaatoms changes the dimensions of the coordination polyhedramodifying the mixed garnet lattice parameters without changingthe coordination symmetry of sites. Due to unchanged sitesymmetry, the modification of lattice parameters can be ascribedto a variation of the distance, leading to the following expres-sion for the energy variation:

(7)

By introducing the crystalline field expressed in (3) and (4), oneobtains

(8)

where and are constants. The coefficients derive fromthe expression

(9)

Fig. 5. Fitting procedure applied to the PL peak shift ofR �Z Neodymiumtransition as a function of YSGG relative concentration in the mixed garnet ( :this study; �: [6]).

where are independents from the distance. Moreover,the distance does not depend upon a specific oxygen atom, thusit is independent from the sum over the subscript. If the pro-posed model is applied to the electrons of Nd , (1) can besolved for even values of the quantum number with upper valueof 6 [12]. The resulting expression can be used to fit the energyshift of the peak position of the emission bands as a functionof the distance. The latter can be finally related to the rela-tive concentration of YSGG in the mixed structure. Indeed, bymeans of a computer simulation of the YAG and YSGG purestructure, the distance can be evaluated in the pure garnets.By assuming the value of 12.01 and 12.45 Å for the reticularconstant of YAG and YSGG [10], [12], the distance is 2.5 and2.7 Å in YAG and YSGG hosts, respectively. It can then be de-duced that the distance increases as the YSGG relative concen-tration increases. As previously discussed, the mixed structure isrealized by gradually substituting the Al cations of YAG struc-ture with the Sc and Ga cations of the YSGG without changingthe crystalline structure and the unit cell symmetry. Thus, in themixed structure, the distance can be expressed as a linear com-bination of the values in the pure garnets

(10)

where the terms and represent the Y-O distance in YSGGand YAG, respectively, and is the relative concentration ofYSGG. In Fig. 5, the fitting procedure is successfully applied tothe experimental data: the shift of the peak position of the PLband due to the transition is fitted by using (8) with the

distance given by (10). The very good agreement between theanalytical model and experimental data allows us to predict theeffect of compositional tuning in mixed garnet structures.

IV. CONCLUSIONS

The PL properties of Nd-doped YAG and YSGG mixed struc-tures has been reported. As the relative concentration of theYSGG increases, a blue shift of the and transi-tions is observed. The reported data were successfully explained

568 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 42, NO. 6, JUNE 2006

by hypothesizing a mixed garnet structure where the two crys-talline phases are mixed at the unit cell level. We proposed ananalytical model based upon the modification induced on thelocal crystalline field by the substitution of the Al cations ofYAG structure with the Sc and Ga cations of the YSGG. Themodel successfully predicts the observed effect of the composi-tional tuning. In addition, the proposed model does not dependon the mixed garnet of choice, but could be exported to a similargarnet structure.

REFERENCES

[1] W. Koechner, Solid-State Laser Engineering. Berlin, Germany:Springer-Verlag, 1996.

[2] G. S. Pomrenke, P. B. Klein, and D. W. Langer, Rare Earth DopedSemiconductors. Pittsburgh, PA: MRS, 1993.

[3] V. Lupei, G. Aka, and D. Vivien, “Quasi-three-level 946 nm CW laseremission of Nd:YAG under direct pumping at 885 nm into the emittinglevel,” Opt. Commun., vol. 204, pp. 399–405, 2002.

[4] J. B. Gruber, M. E. Hills, T. H. Allik, C. K. Jayasankar, J. R. Quagliano,and F. S. Richardson, “Comparative analysis of Nd + (4f ) energylevels in four garnet hosts,” Phys. Rev. B, Condens. Matter, vol. 41, pp.7999–8012, 1990.

[5] B. M. Walsh, N. P. Barnes, R. L. Hutchenson, R. W. Equall, and B.Di Bartolo, “Spectroscopy and lasing characteristics of Nd-dopedY Ga Al O materials: Application toward a compositionallytuned 0.94-�m laser,” J. Opt. Soc. Amer. B, Opt. Image Sci., vol. 15,pp. 2794–2801, 1998.

[6] B. M. Walsh, N. P. Barnes, R. L. Hutchenson, and R. W. Equall, “Com-positionally tuned 0.94-�m lasers: A comparative laser material studyand demonstration of 100-mJ Q-switched lasing at 0.946 and 0.9441�m,” IEEE J. Quantum Electron., vol. 37, no. 9, pp. 1203–1209, Sep.2001.

[7] W. B. Grant, “Lidar for atmospheric and hydrospheric studies,” in Tun-able Laser Application, F. J. Duarte, Ed. New York: Marcel Dekker,1995, pp. 241–250.

[8] N. P. Barnes, B. M. Walsh, and R. L. Hutchenson, “Compositionallytuned solid state lasers,” Adv. Solid State Laser, vol. 1, pp. 522–525,1996.

[9] F. S. Ermeneux, R. W. Equall, R. L. Hutchenson, R. L. Cone, R. Mon-corge, N. P. Barnes, H. G. Gallagher, and T. P. Han, “Nd-doped mixedscandium garnets for compositional tuning to 944.1 nm and improvedlaser performance around 945 nm,” Adv. Solid State Lasers, vol. 26, p.248, 1999.

[10] A. A. Kaminskii, Laser Crystals—Their Physics and Proper-ties. New York: Springer, 1981.

[11] S. Singh, R. G. Smith, and L. G. Van Uiter, “Stimulated-emission crosssection and fluorescent quantum efficiency of Nd in yttrium alu-minum garnet at room temperature,” Phys. Rev B, Condens. Matter,vol. 10, pp. 2566–2572, 1974.

[12] R. C. Powell, Physics of Solid State Laser Materials. New York:Springer, 1998.

[13] J. P. Hurrel, S. P. S. Porto, I. F. Chang, S. S. Mitra, and R. P. Bauman,“Optical phonons of yttrium aluminum garnet,” Phys. Rev., vol. 173,pp. 851–856, 1968.

Alberto Anedda is currently a Full Professorof experimental physics with the Department ofPhysics, University of Cagliari, Monserrato, Italy,and Vice-Rector for the university campus of Mon-serrato. Since the 1970s, his research has mainlyfocused on the optical properties of semiconductors,and dielectric materials in collaboration with na-tional and international research groups. He has beenin charge of numerous research projects supportedby the European Community and by the ItalianMinistry of Education, University and Research.

Carlo Maria Carbonaro was born in Cagliari, Italy,in 1971. He received the Ph.D. degree in physics fromthe University of Cagliari, Monserrato, Italy, in 2000.His thesis concerned deep defects in SiO : theory andexperiments.

He is currently a Full-Time Researcher with thePhysics Department, University of Cagliari. Hisresearch is focused on the optical characterization ofwide bandgap dielectrics and semiconductors withboth bulk and porous structures. He has participatedin research projects supported by the European

Community and the Italian Ministry of Education, University and Research.

Daniele Chiriu was born in Lagonegro, Italy, in1978. He received the M.S. degree in physics fromthe University of Cagliari, Monserrato, Italy, in 2003,and is currently working toward the Ph.D. degree inphysics at the University of Cagliari. His doctoralthesis concerns the study of optical and structuralproperties of mixed oxides Nd:YAG, Yb:YAG, andNd:YVO technologically oriented toward industrialapplication (solid-state lasers).

His main research areas are laser crystals, growthmethods, and optical and structural characterizations.

Pier Carlo Ricci was born in 1974. He received theM.S. and Ph.D. degrees in physics from the Univer-sity of Cagliari, Monserrato, Italy, in 2002.

He is currently involved with different researchprojects with the Optical Spectroscopy Group,Physics Department, University of Cagliari. Hisscientific activity is mainly devoted to the opticalproperties of wide bandgap materials like nanos-tructured oxides (SiO , TiO , WO , SnO IrOboron-doped diamond), as well as III–V semi-conductors such as compounds. He is currently in

collaboration with the Department of Physics, University of Ottawa, Ottawa,ON, Canada, and the Institute of Physics National Academy of Sciences ofAzerbaijan.

Mahmoud Aburish-Hmidat was born in Sourif,Palestine, in 1970. He received the B.Sc. degreein physics from Bethlehem University, Bethlehem,Palestine, in 1996, and the Ph.D. degree in physicsfrom the University of Cagliari, Monserrato, Italy, in2004.

He is currently working under a full-time contractwith Scientific Materials Europe, Tortolì, Italy, wherehe is in charge of quality control and QA of crystalsand optical components, and conducts research anddevelopment programs. His main interests are con-

cerned with optical fibers and guided wave optics, evanescent wave sensors,crystal growth, thin films, optical coating and material processing, spectroscopy,and optical quality control. His additional research activities include optical de-sign and illumination.

Maurilio Guerini was born in Fiorano Al Serio,Italy, in 1957. He received the Industrial Electronicsdiploma from the Electronics Institute of Bergamo,Bergamo, Italy, in 1973.

In 1978, he founded Elettronica Valseriana (cur-rently the leader in the laser industry and marker sys-tems). Two years later, he began a collaboration toengineer Nd:YAG laser systems. This research con-cerns the design and development of lasers based onalexandrite, holmium, and Nd:YAG for industrial andmedical applications. He has been involved with in-

ternational research in the U.S., Switzerland, and South Africa. In 1999, heco-founded Scientific Materials Europe, Tortolì, Italy, which is a leader in crystalgrowth and optical components.

ANEDDA et al.: COMPOSITIONAL TUNING OF PL PROPERTIES IN ND-DOPED YAG–YSGG MIXED STRUCTURES 569

Pier Giorgio Lorrai was born in Nuoro, Italy, in1958. He received the B.Sc. degree in medicine (witha specialization in dentistry) from the University ofMilan, Milan, Italy, in 1985.

His awareness of the importance of solid-statelasers for medical applications and the interest insynthetic crystals had led to his co-founding ofScientific Materials Europe (SCIMEX), Tortolì,Italy, which is a leader in laser crystal and opticalcomponent production. His main research interestsare concerned with the growth of synthetic crystals

derived from the YAG garnet matrix doped with Nd, Er, Yb, Cr, Ce, andcrystalline oxides with mixed structures.

Emery Fortin was born in Chicoutimi, QC, Canada.He is Professor Emeritus with the Department ofPhysics, University of Ottawa, Ottawa, ON, Canada.His research activity includes Bose–Einstein conden-sate to classical optical properties and photo-electricfeatures of semiconductors. He has participated innumerous international research projects and hascollaborated with worldwide scientific groups in theoptical spectroscopy research field.

Dr. Fortin was the recipient of the 1999 Award forExcellence in Research.