8/13/2019 Comparison of 671/1342 nm generation with 532/1064 nm
in Nd: WO microchip lasers
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FRIDAY AR fRN OO N CLE0 97 521
sible way. We have ob tained efficient intracav-ity frequency
doubling with the N d3+ groun d-state transition in Nd:YAG and
Nd:YAlO usingthe nonlinear crystals LBO, BBO, KNbO,, andLiJO,. Un
til now, the maximum cw out pu t of0.5 W a t 473 nm was achieved
with the combi-nation of Nd:YAG and LiJO, in a folded cavitywhen
pumping with about 20 W of diode laserpower. Because of the
internal reabsorptionlosses of the Nd3+-grou nd-state transition th
eapplication of high brightness pump sourceslike beam-shaped laser
diodes is required.For the red spectral region (620-630 nm )we have
investigated sum frequency mixing ofdiode pumped Nd-lasers
operating near 1.06p m and 1.44 pm . In the fundamental mode,both
lasers are able to deliver a few watts ou t-put po wer at a pum p
level of 10 W. A doubleresonant cavity was constructed with a m
ixingresonator that consisted of tw separate armsfor each laser
crystal (1.06 p,m- an d 1.44 p,m-Nd:YAG) and one shared ar m (with
the LBOmixing crystal). So far the maximum cw-outpu t was 210 mW at
10 W p um p power ofeach laser.In add ition, we have operated a Pr,
Yb-fiberupconversion laser with 1.1 W o utp ut power at635 nm. This
device was pumped with 55 WTksapphire-laser radiation. However,
diodepumping of a fiber system with such high in -tensity seems to
be very difficult. Similar argu-ments apply for upconversion
crystalline la-sers.All realized lasers have a large potential
forminaturization, which is an important featurefor commercial
applications in laser TV andprojection devices.We acknowledge the
sup port of the Ger-man governm ent under contract 16SV094 andthe
support by Daimler Benz AG, Forschungund Technik, Miinchen.
CF05 2:15 pmVisible laser applications of Nd3+-dopedX. X. Zhang,
W.-L. Zhou, P. Hong, D. B.Darby, B. H. T. Chai,* Melles G riot
Inc.ew Laser Products Division A ubu rn Massa-chusetts 01501;
E-mail: 10 [email protected]
Neodymium-doped strontium fluorapatite,Sr,(PO,),F, or NdSFAP,
was first dem on -strated, along with o ther ap atite crystals, as
apromising laser material in the late 1960s.'However, because of
the inadequate crystalquality, its application as a laser crystal
wasneglected for many years. Interest in Nd:SFAPhas been renewed
recently in the search formore efficient materials for diode laser
pump -ing, thanks to the availability of large size, highquality
crystals.324 FAP has been ~ h o w n ~ . ~obe one of the best hosts
for Nd3+ dopingamon g the apatite crystals as demonstra ted
byexcellent laser performance resulting from su-perior
spectroscopic proper tie^.^ ^SFAP can be grown by the
Czochralskimethod. High optical quality and low scatter-ing loss
SFAP crystals can now be grown inlarge boules (on e inch in
diameter by six inchesin length) consistently.The emission spectra
of Nd:SFAP are
Sr, PO,),F
a
800 900 1 1100 1200 1300 1400 1500wavelenglh nm)
CF05 Fig 1 Polarized emission spectra ofNd3 +-do ped Sr,(PO,),F.
Arrows indicated thelasing wavelengths demon strated so far.
shown in Fig. 1 for .sr-polarization (E c-axis) and
o-polarization (E -axis). The ar-rows indicate the lasing
wavelengths (i.e., 945,1059, 1129, and 1328 nm) we have
demon-strated so far. Nonlin ear frequency conversiontechniques
have been applied to generategreen, red, yellow, and b lue lasers.
With a 1Wcw diode, more than 100,30 ,50, and 5 mw ofpowers have
been g enerated in 530, 664, 565,and 47 3 nni, respectively.Nd:SFAP
is characterized by its long fluorescence lifetime, large emission
cross section,low loss, strong absorption, and naturally lin-ear
lasing polarization. It is ideal for diode-pumped intracavity
frequency doubled appli-cations. Since the crystals with
excellentquality can be grown in large size, NdSFAPwill be very
cost effective in large quantitymanufacturing. The wavelength
diversity alsomakes NdSFAP an unique choice for manylaser
applications.TRE OL- Cen ter or Research and Education inOptics and
Lasers University of Central FloridaOrlando Florida 328161.
2.
34.
5.
6.
7.
K. B. Steinbruegge, T. Henningsen, R. H.Hopkins, R. Mazelsky, N.
T. Melamed,E. P. Riedel, G. W. Rola nd, Appl. Op t. 11,999
(1972).X. X. Zhang, P. Hong, G. B. Loutts, J. Le-fauch eur, M.
Bass, B. H. T. Ch ai, Appl.Phys. Lett. 64, 3205 (1994).G. B.
Loutts, B. H. T. Ch ai, SPIE Pro c.1863,31 (1993).X. X. Zhang, G.
B. Loutts, M. Bass,B. H. T. Chai, Appl. Phys. Lett. 64, 101994).P.
Hong, X. X. Zhang, M. Bass, B. H. T.Chai, in Conference on Lasers
and Electro-Optics Vol. 8 1994 OSA Technical DigestSeries (Optical
Society of America, Wash-ington, DC 1994 , p. 159.B. H. T. Chai, G.
Loutts, J. Lefaucheur,X.X. Zhang, P. Hong, M. Bass, I. A.Shcherbako
v, A. I. Zagum ennyi, OSAProc. Advanced Solid-State Lasers, T.
Y.Fan, B. H. T . Chai, eds. (Optical SocietyofAmerica, Washington,
DC, 1994), 20, 41(1994).X. X. Zhang, M. Bass, B. H. T. Chai, P.
J.Johnson, J. C. Oles, J. Appl. Phys. 80,12801996).
2:30 pmFO6~ ~Comparison o f 671 1342 nmgenerat ion w ith 532
1064 nm in Nd:WO, microchip lasers
R. S. Conroy, A. Kemp, N. MacKinno n,*B. D. Sinclair, J F Alle n
Physics ResearchLaboratories School of Physics and
AstronomyUniversity of St. Andrews St. Andrews FqeScotland KY16
9SS. United K ingdom;E-mail: [email protected] lasers are
typically formed by apply-ing dielectric mirrors directly to two
near-parallel surfaces of a thin slice of laser gainmaterial.
NdYVO, is a commonly used gainmaterial because of its short
absorption depthand high stimulated emission cross section,'with
the m ain Nd 3+ transitions from the 4F3,,level occurring at 1064
nm and 1342 nm.We have observed monolithic devices tohave low
thresholds (17 mW at 1342 nm, 12mW at 1064 nm) and high slope
efficiencies(48 at 1342 nm , 51 at 1064 nm ) in a TEM,,mod e from
laser diode pumping. The maxi-mu m single frequency power at 1342
nm (5outpu t coupling) was 84 mW, with 120 mWobtained at 1064 nm
(10 outpu t coupling)being limited by the pum p power available.The
intensity stability of these devices un-der diode pumping was found
to be limited toaround 1 (1342 nm ) and 0.7 (1064 nm) byrelaxation
osc illations around 2-5 MHz. Fre-quency stability of these devices
was deter-mined by hetrodyne beating of two free run-ning microchip
lasers on a photodiode. Thelinewidth was found to be less than 300
kHz atboth 1342 nm and 1064 nm, but poo r environ-mental control
limited the frequency stabilityof the devices to tens of megahertz
over oneminute.
Simple intensity modulation of these de-vices by gain-switching
has produced pulses asshort as 5.5 ns at 1342 and 1.85 ns at 1064
nmwith peak powers of 8.4 W (1342 nm ) and 24W (1064 nm). We will
report on theQ-switched operation of these devices.By forming a com
posite cavity with a pieceof nonlinear material it is possible to
frequencydouble these transitions. P revious work in St.Andrews has
shown a sandwich of Nd:WO,and KTP produced 132 mW at 532 nm
fromsuch a device with 650 mW from a laser diode.'671 nm can be
produced by use of LBO cut foreither type I or type I1 noncritical
phase-matching (NCPM)., Our initial work withtype I material has
shown 11 pW at 671 nmgenerated from single pass of220 mW at 1342nm.
O ur latest results on intracavity doublinginto the red will be
presented and comparedwith the green generation in
Nd:WO,/KTPchipsets.
Currently with Uniphase Lasers UK Lid,Newn ham United Kingdom1.
G. J. Kintz, T. Baer, J. Quan tum Electron.
269 (1990).2. MacKinno n, Sinclair, Opt. Comm un. 105(1994);
MacKinnon, Sinclair, Sibbett,Jenny, Jenks, Craven, Piehler, Proc
CLEO'94.G. R. Morrison, M. Ebrahimadeh, C. F.Rae, M. H. D unn, Opt.
Comm un. 118,3.55-60 (1995).
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