Table Of ContentOPTICS AND PHOTONICS
(fonnerly QuantumElectronics)
SERIESEDITORS
PAULF.LIAO
BellCommunicationsResearch,Inc.
RedBank,NewJersey
PAUL L. KELLEY
LincolnLaboratory
MassachusettsInstituteofTechnology
Lexington,Massachusetts
IVAN P. KAMINOW
AT&TBellLaboratories
Holmdel,NewJersey
Acompletelistoftitlesinthisseriesappearsattheendofthisvolume.
o
o
H A N D B K
Editedby
F. J. Duarte
EastmanKodakCompany
Rochester,NewYork
ACADEMIC PRESS
SanDiego NewYork Boston
London Sydney Tokyo Toronto
8
This book is printed on acid-free paper.
Copyright© 1995byACADEMICPRESS,INC.
AllRightsReserved.
Nopartofthispublicationmaybereproducedortransmittedinanyform orbyany
means, electronicormechanical, includingphotocopy, recording, orany information
storageandretrievalsystem,withoutpermissioninwritingfromthepublisher.
AcademicPress,Inc.
ADivisionofHarcourtBrace& Company
525BStreet,Suite1900,SanDiego,California92101-4495
UnitedKingdomEditionpublishedby
Academic PressLimited
24-28Oval Road, LondonNWI 7DX
LibraryofCongressCataloging-in-PublicationData
Duarte,F.J.(FrankJ.)
Tunablelasershandbook / F.J. Duarte.
p. em. - (Opticsandphotonicsseries)
Includesindex.
ISBN0-]2-222695-X
1. Tunablelasers. I. Title. II. Series.
TA1706.D83 1995
621.36'6-dc20 95-8165
CIP
PRINTEDINTHEUNITEDSTATESOFAMERICA
95 96 97 98 99 00 EB 9 8 7 6 5 4 3 2
Contributors
Numbersinparenthesesindicatethepagesonwhichtheauthors'contributionsbegin.
Norman P.Barnes (219, 293), NASA LangleyResearch Center, Hampton,Vir
ginia23681
StephenVincentBenson (443),AcceleratorDivision,ContinuousElectron
BeamAcceleratorFacility, NewportNews,Virginia23606
F.J. Duarte (1,9, 167),Eastman Kodak Company, Rochester, NewYork 14650
CharlesFreed (63), Lincoln Laboratoryand the DepartmentofElectrical
Engineering and ComputerScience, Massachusetts Institute ofTechnology,
Lexington, Massachusetts02173
D. G. Harris (33), Rockwell International, CanogaPark, California91309
R. C. Sze (33), LosAlamos National Laboratory, LosAlamos, New Mexico
87545
Paul Zorabedian (349), PhotonicTechnology Department, Hewlett-Packard
Laboratories,PaloAlto, California94303
xi
Preface
Light and colorare concepts that have always invoked thoughts ofjoy and won
der. Perhaps the essence of light is well captured in the realm of poetry where
light has been identified as a "changing entity of which we can never be sati
ated" (GabrielaMistral, 1889-1957).
This book is about changing light; it is about light sources that emit the
colors of the rainbow and beyond. Indeed, the central theme of this book is
changing light of high spectral purity or, as a physicist would say, tunable
coherentradiation.
Tunable lasers ar unique physical systems thatenjoy an abundance ofappli
cations ranging from physics to medicine. Given this utilitarian aspect, the sense
ofwonderin tunable lasersextends beyond beauty.
Tunable Lasers Handbook provides a broad and integrated coverage ofthe
field, including dispersive tunable laser oscillators, tunable excimer lasers, tun
able CO lasers, dye lasers, tunable solid-state lasers, optical parametric oscilla
2
tors, tunable semiconductorlasers, and free electron lasers. In this regard, the set
of coherent sources considered here spans the electromagnetic spectrum from
the near ultraviolet to the far infrared. Further features are the inclusion ofboth
discretely and broadly tunable lasers, pulsed and continuous wave lasers, and
gain mediain the gaseous, liquid, and solid state.
xiii
xiv Preface
Although the basic mission ofthis work is to offeran expeditious survey of
the physics, technology, and performance of tunable lasers, some authors have
ventured beyond the format of a handbook and have provided comprehensive
reVIews.
This project was initiated in 1990. Completion in late 1994 has allowed the
inclusion of several recent developments in the areas of solid-state dye lasers,
optical parametric oscillators, and external cavity tunable semiconductor lasers.
The editor is particularly grateful to all contributing authors for their hard work
andfaith in the visionofthis project.
F. J. Duarte
Rochester,NY
January1995
Introduction
F. J. Duarte
Eastman Kodak Company
Rochester, New York
1. INTRODUCTION
Tunable sources of coherent radiation are suitable for a wide range of appli-
cations in science, technology, and industry. For instance, the first broadly tun-
able laser source, the dye laser, is used for a plethora of applications in many
diverse fields [1] including physics [2-4], spectroscopy [5,6], isotope separation
[6-8], photochemistry [9], material diagnostics [9], remote sensing [9-11], and
medicine [ 12]. In addition to issues of physics, it is this utilitarian aspect of tun-
able lasers that motivates much of the interest in the field.
In recent years, new sources of tunable coherent radiation have become
available that have either extended spectral coverage or yielded appealing emis-
sion characteristics. Notable among these sources are optical parametric oscilla-
tors and tunable semiconductor lasers.
This field has several natural subdivisions. For instance, although most
sources of tunable coherent radiation are lasers, some sources such as the optical
parametric oscillator (OPO) do not involve population inversion. An additional
classification can be established between broadly tunable sources of coherent
radiation, including broadly tunable lasers, and discretely tunable lasers, and/or
line-tunable lasers. A subsequent form of classification can be the physical state
of the different gain media such as gaseous, liquid, and solid state. Further
Tunable Lasers Handbook
Copyright © 1995 by Academic Press, Inc. All rights of reproduction in any form reserved.
2 F.J. Duarte
avenues of differentiation can include the required method of excitation and the
mode of emission, that is, pulsed or continuous wave (cw). Moreover, sources of
tunable coherent radiation can be further differentiated by the spectral region of
emission and energetic and/or power characteristics. Also, in the case of pulsed
emission, pulse duration, and pulse repetition frequency (prf) are important.
The spectral coverage available from pulsed broadly tunable sources of
coherent radiation is listed in Table 1. The spectral coverage available from cw
broadly tunable lasers is given in Table 2 and emission wavelengths available
TABLE 1 Wavelength Coverage Available from Pulsed Broadly Tunable Sources
of Coherent Radiation
Source Wavelength range
Dye lasers 320-1200 nma [ 13]
Ti3+:A1203 laser 660-986 nm [14]
Cr3+:BeA1204 laser 701-818 nm [ 15]
OPO
BBO 0.41-2.7 ~am [16]
Free-electron lasers (FELs) 2 ~am-1 mm b [17]
aWavelength range covered with the use of various dyes.
bCombined wavelength range from several free-electron lasers.
TABLE 2 Wavelength Coverage Available from cw Broadly Tunable Lasers
Laser source Wavelength range
Dye lasers 320-1000 nma [ 18]
Ti3+:A1203 laser 710-870 nmb-[ 19]
Semiconductor lasers C
InGaAsP/InP 55 nm at 1500 nm [20]
InGaAsP/InP 1255-1335 nm [21]
GaA1As 815-825 nm [22]
GaAIAs 20 nm at 780 nm [23]
a Wavelength range covered with the use of various dyes.
bWavelength range of single-longitudinal-mode emission. Tuning range limited by coatings of
mirrors [ 19]. Commercial designs offer extended tuning ranges beyond 1000 nm.
c Wavelength tuning achieved using external cavity designs.
1 Introduction
from discretely tunable lasers are listed in Table 3 of Chapter 5. The information
provided in these tables indicates that broadly tunable sources of coherent radia-
tion span the electromagnetic spectrum from --300 nm to N1 mm. Excimer lasers
offer limited tunability in regions further into the ultraviolet around 193 and 248
nm. The tuning ranges quoted for ArF and KrF lasers are N17,000 GHz and
---10,500 GHz [24], respectively. An exception among excimer lasers is the XeF
laser with its C--->A transition, which has demonstrated broadly tunable emission
in the 466- to 512-nm range [25]. In Table 3 of Chapter 5 bandwidth and tuning
range information is included for a variety of discretely tunable lasers including
excimer, N 2, HgBr, and Cu lasers. Wavelength information on line-tunable cw
lasers such as Ar+ and the Kr+ lasers is included in Table 11 of Chapter 5. Ener-
getic and power characteristics of some tunable sources of coherent radiation are
listed in Table 3 of this chapter. Although the title of this book refers specifically
to tunable lasers, sources that do not involve population inversion in their gener-
ation of coherent radiation are included. This approach is justified because the
issue under consideration is the generation of tunable coherent radiation, which
is precisely what OPOs perform.
In the area of ultrashort-pulse generation, dye lasers have demonstrated
17 fs using intracavity pulse compression [36] and 6 fs using further extra
TABLE 3 Energy and Power Characteristics from Broadly Tunable Sources of
Coherent Radiation
Source Pulse regime cw regime
Energy Power Power
a a a
Dye lasers 400 jb [26] 2.5 kW at 13.2 kHzc [27] 43 Wd [28]
Ti3+:AI203 laser 6.5 jb,e [29] 5.5 W at 6.5 kHzc [30] 43 Wd~ [32]
220 W at 110 Hzb [31 ]
Cr3+:BeA1204 laser >100 Jb [33] 6.5 Wg [34]
OPOs
BBO >100 mJ [16]
LiNbO 3 10 mW [35]
FELs ---GW levels in short pulses [17]
aT hese values may represent the best published performance in this category.
bUnder flashlamp excitation.
cUnder copper-vapor-laser (CVL) excitation.
dUnder Ar+ laser excitation.
eUses laser dye transfer in the excitation.
fLiquid-nitrogen cooled.
gUnder Hg-lamp excitation.
4 F.J. Duarte
cavity compression [37]. Utilizing intracavity negative dispersion techniques,
Ti3+:A1203 lasers have yielded 11 fs [38]. Also, 62 fs have been reported in
OPOs using extracavity compression [39]. Emission from FELs is intrinsi-
cally in the short-pulse regime with pulses as short as 250 fs [17].
2. TUNABLE LASER COMPLEMENTARITY
From the data given previously it could be stated that tunable sources of
coherent radiation span the electromagnetic spectrum continuously from the near
ultraviolet to the far infrared. However, this claim of broad coverage is sustained
from a global and integrated perspective of the field. Further, a perspective of
complementarity is encouraged by nature, given that different sources of tunable
coherent radiation offer different optimized modes of operation and emission.
In this context, under ideal conditions, the application itself should deter-
mine the use of a particular laser [40,41]. This perspective should ensure the
continuation of the utilitarian function traditional of the early tunable lasers that
ensured their success and pervasiveness.
To determine an appropriate laser for a given application, the logic of selec-
tion should identify the simplest and most efficient means to yield the required
energy, or average power, in a specified spectral region. In practice, the issue
may be complicated by considerations of cost and availability. In this regard,
selection of a particular pulsed laser should include consideration of the follow-
ing parameters:
1. Spectral region
2. Pulse energy
3. Average power (or prf)
4. Cost (capital and operational)
5. Environment.
More subtle issues that are also a function of design include the following:
6. Emission linewidth
7. Wavelength and linewidth stability
8. Pulse length (femtoseconds, nanoseconds, or microseconds)
9. Physical and optical ruggedness
10. Amplified spontaneous emission (ASE) level.
A basic illustration of complementarity is the use of different types of lasers
to provide tunable coherent radiation at different spectral regions. For instance.
FELs can be recommended for applications in need of far-infrared emission,
whereas dye lasers are suitable for applications requiring high average powers in
the visible.
