U.S. patent application number 09/748976 was filed with the patent office on 2001-08-02 for self-frequency doubled nd-doped ycob laser.
This patent application is currently assigned to University of Central Florida. Invention is credited to Chai, Bruce H.T., Eichenholz, Jason, Hammons, Dennis Allen, Richardson, Martin, Ye, Qing.
Application Number | 20010010700 09/748976 |
Document ID | / |
Family ID | 26816198 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010010700 |
Kind Code |
A1 |
Eichenholz, Jason ; et
al. |
August 2, 2001 |
Self-frequency doubled Nd-doped ycob laser
Abstract
Neodymium-doped yttrium calcium oxyborate (Nd:YCOB) is the
single active gain element for a solid-state laser device capable
of achieving both lasing and self-frequency doubling optical
effects. A pumping source for optically pumping Nd:YCOB can
generate a laser light output of approximately 400 mW at
approximately 1060 nm wavelength and a self-frequency doubled
output of approximately 60 mW at approximately 530 nm wavelength.
Thus, a laser device can be designed that is compact, less
expensive and a high-powered source of visible, green laser
light.
Inventors: |
Eichenholz, Jason; (Oviedo,
FL) ; Ye, Qing; (Coroing, NY) ; Hammons,
Dennis Allen; (Orlando, FL) ; Chai, Bruce H.T.;
(Oviedo, FL) ; Richardson, Martin; (Geneva,
FL) |
Correspondence
Address: |
LAW OFFICES OF BRIAN S STEINBERGER
101 BREVARD AVENUE
COCOA
FL
32922
US
|
Assignee: |
University of Central
Florida
|
Family ID: |
26816198 |
Appl. No.: |
09/748976 |
Filed: |
December 27, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09748976 |
Dec 27, 2000 |
|
|
|
09495770 |
Feb 1, 2000 |
|
|
|
6185236 |
|
|
|
|
60118301 |
Feb 2, 1999 |
|
|
|
Current U.S.
Class: |
372/41 |
Current CPC
Class: |
H01S 3/1095 20130101;
H01S 3/1611 20130101; H01S 3/1666 20130101; H01S 3/16 20130101 |
Class at
Publication: |
372/41 |
International
Class: |
H01S 003/16 |
Claims
We claim:
1. A solid-state laser device wherein the single active gain
element is trivalent neodymium-doped yttrium calcium oxyborate
crystal [Nd.sup.3+:YCa.sub.4O(BO.sub.3).sub.3].
2. A solid-state laser device of claim 1, wherein the host crystal
is YCOB.
3. A solid-state laser device of claim 2, wherein Nd-doping is in a
range from approximately 2 weight % to about 4 weight % of the YCOB
crystal.
4. A solid-state laser device of claim 2, wherein Nd-doping is
approximately 5 weight % of the YCOB crystal.
5. A solid-state laser device of claim 2, wherein Nd-doping is in a
range from approximately 6 weight % to about 20 weight % of the
YCOB crystal.
6. A solid-state laser device of claim 5, wherein Nd-doping is
approximately 10 weight % of the YCOB crystal.
7. A solid-state laser device with optical components comprising:
a) one single element combining the active gain medium and the
frequency doubler; and b) a pumping source for optically pumping
said single element of said device to generate a laser light output
of approximately 400 mW at approximately 1060 nm wavelength and a
self-frequency doubled output of approximately 60 mW at
approximately 530 nm wavelength, said pumping source being selected
from one of a coherent pumping source and an incoherent pumping
source.
8. The laser device of claim 7, wherein said single active gain
element is a crystal of Nd.sub.xYCa.sub.4O(BO.sub.3).sub.3 where
(x=0.02-0.10) and serves as a self-frequency doubling crystal
capable of performing a frequency conversion process within the
crystal.
9. The laser device of claim 8, wherein the Nd:YCOB gain medium is
antireflective coated at approximately 1060 nm, approximately 520
nm and approximately 812 nm.
10. The laser device of claim 7, 8 or 9, wherein said incoherent
pumping source is selected from the group consisting of a
straight-shaped lamp, a spiral-shaped lamp, and an annuloid
lamp.
11. The laser device of claim 10, wherein said incoherent pumping
source is pulsed.
12. The laser device of claim 10, wherein said incoherent pumping
source is continuous.
13. The laser device of claim 10, 11, or 12, wherein said
incoherent pumping source is selected from the group consisting of
a xenon lamp, a krypton lamp, and optical spectrum matched laser
diodes.
14. The laser device of claim 7, wherein said coherent pumping
source is selected from the group consisting of a semi-conductor
diode laser and an array of diode lasers.
15. The laser device of claim 14, wherein said coherent pumping
source is pulsed.
16. The laser device of claim 14, wherein said coherent pumping
source is continuous.
17. The laser device of claim 16, wherein said coherent pumping
source comprises Titanium:Sapphire radiation.
18. The laser device of claim 17, wherein the optical radiation
from said coherent pumping source is tuned to a wavelength that
provides energy to said Nd:YCOB crystal.
19. The laser device of claim 17, wherein the optical radiation
from said coherent pumping source is tuned to a wavelength from
approximately 760 nm to approximately 800 nm.
20. The laser device of claim 17, wherein the optical radiation
from said coherent pumping source is tuned to a wavelength of
approximately 792 nm.
21. The laser device of claim 17, wherein the optical radiation
from said coherent pumping source is tuned to a wavelength between
approximately 800 nm to approximately 805 nm.
22. The laser device of claim 17, wherein the optical radiation for
said coherent pumping source is tuned to a wavelength between
approximately 805 nm to approximately 808 nm.
23. The laser device of claim 17, wherein the optical radiation for
said coherent pumping source is tuned to a wavelength between
approximately 808 nm to approximately 815 nm.
24. The laser device of claim 17, wherein the optical radiation for
said coherent pumping source is tuned to a wavelength of
approximately 812 nm.
25. The laser device of claim 17, wherein the optical radiation for
said coherent pumping source is tuned to a wavelength between
approximately 815 nm to approximately 840 nm.
26. A method for producing a fundamental beam and self-frequency
doubling said fundamental beam to produce green laser light,
comprising the steps of: (a) emitting optical radiation from a pump
source selected from one of a coherent pumping source and an
incoherent pumping source; (b) pumping an active gain medium in a
laser cavity with the optical radiation of step (a), wherein the
gain medium consists of trivalent neodymium-doped yttrium calcium
oxyborate crystal, NdxYCa.sub.4O(BO.sub.3).sub.3 where
(x=0.02-0.10); and (c) generating a fundamental beam that is
self-frequency doubled to produce green laser light.
27. The method of claim 26, wherein said oxyborate crystal of step
(b) is anti-reflective coated at approximately 1060 nm,
approximately 530 nm and approximately 812 nm.
28. The method of claim 26, wherein said green laser light of step
(c) has a wavelength of approximately 530 nm.
29. The method of claim 26, wherein green laser light is produced
in a process comprising: a) emitting optical radiation from a
coherent pumping source being tuned to a wavelength that provides
energy to said Nd:YCOB crystal; b) pumping an active gain medium in
laser cavity with optical radiation of step (a); c) producing a
fundamental beam of approximately 1060 nm; and d) self-frequency
doubling the fundamental beam of step (c) to produce green laser
light at a wavelength of approximately 530 nm.
30. The method of claim 26, wherein the optical radiation from said
coherent pumping source is tuned to a wavelength from approximately
760 nm to approximately 800 nm.
31. The method of claim 26, wherein the optical radiation for said
coherent pumping source is tuned to a wavelength of approximately
792 nm.
32. The method of claim 26, wherein the optical radiation for said
coherent pumping source is tuned to a wavelength between
approximately 800 nm to approximately 805 nm.
33. The method of claim 26, wherein the optical radiation for said
coherent pumping source is tuned to a wavelength between
approximately 805 nm to approximately 808 nm.
34. The method of claim 26, wherein the optical radiation for said
coherent pumping source is tuned to a wavelength between
approximately 808 nm to approximately 815 nm.
35. The method of claim 26, wherein the optical radiation for said
coherent pumping source is tuned to a wavelength of approximately
812 nm.
36. The method of claim 26, wherein the optical radiation for said
coherent pumping source is tuned to a wavelength between
approximately 815 nm to approximately 840 nm.
Description
[0001] This invention relates to solid-state laser devices, and in
particular to a new type of compact, high-power laser with
frequency doubling capabilities to generate coherent visible light,
and claims priority to U.S. Provisional Patent Application S. N.
60/118,301, filed Feb. 2, 1999.
BACKGROUND AND PRIOR ART
[0002] The laser is a device for the generation of coherent, nearly
single-wavelength and single-frequency, highly directional
electromagnetic radiation emitted somewhere in the range from
submillimeter through ultraviolet and x-ray wavelengths. The word
laser is an acronym for the most significant feature of laser
action: light amplification by stimulated emission of
radiation.
[0003] There are many different kinds of laser, but they all share
a crucial element: each contains material capable of amplifying
radiation. This material is called the gain medium, because
radiation gains energy passing through it. The physical principle
responsible for this amplification is called stimulated emission.
It was widely recognized that the laser would represent a
scientific and technological step of the greatest magnitude, even
before T. H. Maiman constructed the first one in 1960. Laser
construction generally requires three components for its operation:
(1) an active gain medium with energy levels that can be
selectively populated; (2) a pumping process to produce population
inversion between some of these energy levels; and usually (3) a
resonant electromagnetic cavity structure containing the active
gain medium, which serves to store the emitted radiation and
provide feedback to maintain the coherence of the electromagnetic
field.
[0004] In a continuously operating laser, coherent radiation will
build up in the cavity to a level set by the decrease in inversion
required balancing the stimulated emission process with the cavity
and medium losses. The system is then said to be lasing, and
radiation is emitted in a direction defined by the cavity.
[0005] A common approach to converting the laser wavelength to half
its value (for example, from 1064 nm to 532 nm), often used to
convert infra-red lasers to lasers emitting in the visible part of
the spectrum, is to use intra-cavity frequency up conversion (IC).
The most common IC approach is to incorporate a second crystal, a
non-linear optical crystal, correctly oriented for phase matching,
inside the laser resonator, and to adjust the reflectivity of the
cavity mirrors to maximize the wavelength converted laser light
emission.
[0006] The lasers of the present invention use a new crystal
material as the active gain medium. The new gain medium is
trivalent neodymium-doped yttrium calcium oxyborate referred to
herein as Nd.sup.3+:YCa.sub.4O(BO.s- ub.3).sub.3 or Nd:YCOB for
easier reference. Patent Corporation Treaty (PCT) application
numbered WO 96/26464 reports the growth of calcium gadolinium
oxyborate, GDCOB, as the first element of a new family of borate
crystals. The abstract for WO 96/26464 states, "The crystals are
prepared by crystallising a congruent melting, composition of
general formula: M.sub.4LnO(BO.sub.3).sub.3, wherein M is Ca or Ca
partially substituted by Sr or Ba, and Ln is a ianthanide from the
group which includes Y, Gd, La and Lu. Said crystals are useful as
frequency doublers and mixers, as an optical parametric oscillator
or, when partially substituted by Nd.sup.3+, as a frequency
doubling laser." Although, the general formula might be interpreted
to include various Nd-doped crystals, the PCT application, WO
96/26464, only demonstrates and claims Nd-doped GdCOB or LaCOB.
Additionally, the subject inventors have discovered that the
orientation of axes and angles for the demonstrated crystals
disclosed in WO 96/26464 are not efficient for a self-frequency
doubling laser. More importantly, WO 96/26464 does not demonstrate
nor claim any method nor apparatus for using Nd-doped YCOB as a
self-frequency doubling laser.
[0007] In the prior art, there are no disclosures of Nd:YCOB as an
active gain medium or as the gain medium in a harmonic generation
laser. As a member of the oxyborate family of crystals, the
non-hygroscopic YCOB crystal possesses nonlinear optical properties
and when doped with Nd.sup.3+ ions, the new crystals have the
advantage of combining the active gain medium and the nonlinear
frequency conversion medium in a single element. Self-frequency
doubled (SFD) lasers are an attractive alternative to conventional
intra-cavity frequency doubling with a separate nonlinear crystal
such as potassium titanyl phosphate (KTP), as disclosed in U.S.
Pat. No. 4,942,582. A SFD laser incorporates lower reflection,
absorption and scattering losses and leads to a simpler and more
robust resonator design. With the addition of diode-pumping, the
Nd:YCOB laser provides a new type of compact, high-powered, visible
laser light source.
[0008] Trivalent neodymium-doped crystalline laser systems
producing optical radiation are reported. U.S. Pat. No. 4,942,582
supra, discloses a single frequency solid state laser having an
active gain medium which comprises a block of neodymium doped
crystals of vanadium oxide (YVO.sub.4), garnet (YSGG) and borate
(YAB) in combination with a separate frequency doubling crystal of
KTP (potassium titanyl phosphate, or KTiOPO.sub.4); this invention
overlooked the self-frequency doubling possibilities of the Nd:YAB
crystal. U.S. Pat. No. 5,058,118 disclosed that a single crystal of
neodymium doped borate (Nd:YAB) was useful as a self-frequency
doubling minilaser generating a 0.532 .mu.m (green light) and 0.660
.mu.m (red light) laser beam. However, this laser configuration
suffers from poor optical quality and self-absorption at 530 nm as
disclosed in J. Appl. Phys., Vol. 66, pp. 6052-6058, 1989.
[0009] More recently, the approach to generating high power,
visible laser light has been to use nonlinear optical crystals to
convert near-infrared radiation to the visible portion of the
spectrum via second harmonic generation (SHG) (sometimes termed
frequency doubling and used interchangeably, herein). This process
generates a harmonic wavelength that doubles the frequency of the
fundamental wavelength. Since the SHG conversion efficiency is a
function of the fundamental laser beam intensity, the nonlinear
crystal is often placed inside the cavity of a low-power continuous
wave laser to benefit from the higher intracavity fundamental beam
intensity. This technique is discussed in U.S. Pat. No. 5,610,934
and U.S. Pat. No. 5,751,751 which provides an example of frequency
doubling when neodymium doped crystals of vanadium oxide
(YVO.sub.4) or (GdVO.sub.4) are bonded to non-linear crystals of
potassium niobate (KNbO.sub.3) or .beta. barium borate (BBO). A
fundamental beam of about 914 nm is frequency doubled to produce
blue laser light at about 457 nanometers (nm) or (0.457 .mu.m).
[0010] U.S. Pat. No. 5,802,086 discloses a continuous wave (cw)
microlaser with a highly absorbing solid-state gain material,
preferably neodymium-doped yttrium orthovanadate (Nd:YVO.sub.4)
that lases at two fundamental wavelengths and are frequency-mixed
in a nonlinear crystal oriented within the cavity to generate a
third wavelength which maybe difficult to generate directly or by
frequency doubling.
[0011] Popular host crystals including garnet, especially yttrium
aluminum garnet (YAG) and yttrium orthovanadate (YVO4) are
discussed in the prior art. However, the search for smaller, less
expensive, more powerful, multifunctional lasers continues. The
discovery of a new class of laser hosts, the oxyborates, makes
possible the combination of linear and nonlinear optical properties
in a single active medium. More particularly, the neodymium-doped
oxyborate crystal (Nd:YCOB) of the present invention generates a
near infrared fundamental light which can be self-frequency doubled
to provide a compact, efficient, source of visible green laser
light.
SUMMARY OF THE INVENTION
[0012] The first objective of this invention is to use Nd:YCOB as
an active gain medium for a laser.
[0013] The second objective of this invention is to provide a
self-frequency doubled (SFD) laser using the oxyborate family
of-crystals as the host crystal.
[0014] The third objective of the present invention is to provide a
visible light laser that combines the active gain medium and
frequency doubler in one single element.
[0015] The fourth objective of this invention is to provide a
compact efficient source of visible laser light.
[0016] A preferred embodiment of the invention provides a
neodymium-doped oxyborate crystal (Nd:YCOB) pumped with either
tunable or continuous wave (cw) coherent, diode pumped, or
titanium:Sapphire laser radiation or near infrared light in a range
from approximately 760 nanometer (nm) to approximately 840 nm, with
highest absorption at approximately 792 nm and approximately 812
nm. The preferred embodiment efficiently generates 530 nm of green
laser light.
[0017] The optical pumping means which provides energy to the
crystal can be selected from one of a coherent or incoherent light
pumping source. The incoherent pumping source may be xenon or
krypton lamps or light emitting diodes (LED) or laser diodes, which
can be of pulsed or continuous wave output. The coherent pumping
source may be a laser light source, such as a single laser diode or
a matrix laser diode series, which can also be of pulsed or
continuous wave output.
[0018] Further objects and advantages of this invention will be
apparent from the following detailed description of a presently
preferred embodiment, which is illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0019] FIG. 1 is an experimental laser cavity design. F. I.,
Faraday isolator; HWP, half-wave plate; lens, 8.8-cm PL/CX lens;
HR, 5-mROC mirror; X-tal, 2% Nd:YCOB; OC, 10-cm ROC output
coupler.
[0020] FIG. 2 is Fundamental output power at wavelength vs.
absorbed Ti:Sapphire pump power for 2% Nd:YCOB.
[0021] FIG. 3 is Self frequency-doubled (SFD) output power vs.
absorbed pump power with 5% Nd:YCOB active gain medium.--3a)
Ti:Sapphire pumped; 3b) Diode pumped.
[0022] FIG. 4 shows Orientation of X, Y, Z optical indicatrix axes
relative to the crystallographic axes and planes of Nd:YCOB. The
typical boule cross-section is also indicated.
[0023] FIG. 5 is crystal orientation for optimum self-frequency
doubling (SFD) laser action.
[0024] FIG. 6 is the absorption spectrum for 5% Nd:YCOB for light
polarized parallel to the X, Y, Z axes shown in FIG. 5 supra.
[0025] FIG. 7 is Emission spectrum for 5% Nd:YCOB as a function of
polarization relative to X, Y and Z axes.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Before explaining the disclosed embodiments of the present
invention in detail it is to be understood that the invention is
not limited in its application to the details of the particular
arrangement shown since the invention is capable of other
embodiments. Also, the terminology used herein is for the purpose
of description and not of limitation.
[0027] The Czochralski method, as reported by Qing Ye and Bruce H.
T. Chai in the Journal of Crystal Growth 197 (1999) 228-235;
"Crystal growth of YCa.sub.4O(BO.sub.3).sub.3 and its orientation"
is used to grow the oxyborate crystal for the present invention.
When rare-earth elements, such as, neodymium are added during the
crystal growing process, the crystal is said to be "doped" with the
rare-earth ions. Doping changes the function of the crystal into an
active gain medium, since undoped YCOB crystal is a nonlinear
optical medium, doping of the crystal with an impurity converts the
crystal into a nonlinear optical laser crystal.
[0028] When the newly formed crystal is grown from the melt, it is
generally in a cylindrical shape called a crystal "boule." The
boule can be cut into a cylindrical rod or other geometric shapes.
To make it into a laser crystal it generally requires two flat
ends. The flat ends are polished and given an appropriate
reflective coating or anti-reflective coating. One end is more
reflective than the other; laser light is emitted through the end
that is less reflective--the output coupler.
[0029] Undoped YCOB has been shown to have a nonlinear coefficient,
d.sub.eff of 1.1 pm/V, which is between that of other nonlinear
crystals KDP (0.37) and BBO (1.94 pm/V). See J. Appl. Phys. 36, 276
(1997) and W. Koechner, Solid State Laser Engineering, 4th ed.
(Springer-Verlag New York, 1996), p. 579.
[0030] A concentration of Nd exceeding 5% or more of the doping
changes the refractive indices of the crystal; which in turn,
changes the optimum angle for phase matching. Nd doping for the
present invention is preferably in a range from approximately 2 to
approximately 20 weight % of the YCOB crystal, with optimum doping
at approximately 10%.
[0031] Initial experiments were performed to investigate the
potential of Nd:YCOB as a laser medium. A simple hemispherical
laser system pumped by a tunable cw Ti:sapphire laser centered
either at 792 nm or 812 nm was constructed as shown in FIG. 1. The
linear cavity layout 10, consisting of a 5-meter radius of
curvature (ROC) high reflective rear mirror, 11 and a 10-cm radius
of curvature output coupler, 12. An uncoated 5 mm.times.5
mm.times.13 mm long 2% Nd:YCOB crystal, 13, with the Z axis along
the laser axis, was placed next to the high reflector, 11. The pump
laser polarization was rotated for maximum absorption (along the
Z-axis) in the crystal and focused into the crystal with an 8.8-cm
plano/convex lens, 14, through the rear mirror which was
approximately 82% transparent at 792 nm and 812 nm. The tunable
Ti:sapphire pumping source 15, passed through the Faraday isolator
16, and traveled through the half-wave plate, 17. The half-wave
plate can be used to rotate the polarization of the pump
radiation.
[0032] The required optical components for the solid state laser
device of this invention are the active gain medium and a pumping
source. Equipment items 16 and 17 are optional. The high reflector,
11 is preferably flat and does not need the 5% radius of curvature
(ROC). Focusing of the laser diode can be with any optical element,
such as a lens.
[0033] The experimental cavity was used to generate fundamental and
self-frequency doubled laser wavelengths for both 2% Nd:YCOB and 5%
Nd:YCOB. It is theoretically possible for Nd-doping to be in a
range up to 50 weight %; however, it is most preferred that doping
be in a range from 2 to 10 weight % of the YCOB crystal. The
inventors have discovered that Nd-doping concentration of
approximately 10 weight % is most efficient; above 10% quenching
and degradation of the crystal starts. Preferably, the YCOB crystal
can be anti-reflective coated. The output power at both the
fundamental and self-frequency doubled laser wavelengths were
measured for 0, 1% and 2% output coupling.
[0034] FIG. 2 shows the fundamental output power for 2% output
coupling versus absorbed pump power in a 2% Nd:YCOB laser. The
minimum pump threshold for lasing at 530 nm was determined to be 97
mW for the lowest transmission output coupler. Slope efficiencies
of 44% with fundamental output powers exceeding 400 mW for 1 W of
absorbed pump power was observed for 2% output coupling. Green
self-frequency doubled output powers of over 0.7 mW were measured
for 1 W of absorbed pump power in this experimental laser
system.
[0035] In another embodiment, efficient self-frequency doubling was
demonstrated utilizing a 3 mm.times.3 mm.times.5 mm rotated Z-plate
of 5% Nd:YCOB. Utilizing the cavity design identical to the linear
cavity in FIG. 1, various pumping means were employed. The
measurements shown in FIG. 3 confirm the potential efficiency of a
5% Nd:YCOB laser system when pumped by Ti:Sapphire radiation 3a)
and diode laser 3b).
[0036] To maximize the SFD output, the output coupler was highly
reflecting at 1060 nm (R>99.9%) and highly transmitting
(T>94%) at 530 nm. The SFD output was optimized by adjusting the
angle and hence phase matching of the crystal, by varying the mode
size in the crystal, and changing the cavity length. The SFD power
as a function of absorbed Ti:Sapphire pump power for a laser having
an active medium of 5% Nd:YCOB is shown in FIG. 3a. Nearly 60 mW of
530 nm laser light was obtained with 900 mW of pump power absorbed
in the crystal. The laser threshold for SFD output was only 23 mW
of power absorbed in the crystal. No additional elements were
inserted into the cavity to narrow the linewidth of the laser.
[0037] Utilizing the same configuration as above, but with single
diode-pumping, 62 mW of 530 nm SFD light was generated for pump
power up to 860 mW absorbed power. See FIG. 3b.
[0038] Properties, orientation and structure of the host crystal
were examined. YCOB has a monoclinic crystal structure belonging to
the space group Cm (point group m).
[0039] The optical indicatrix axes (X, Y and Z) are defined
relative to the crystallographic axes (a, b and c) and planes as
shown in FIG. 4. by adopting the traditional refractive index
convention n.sub.x<n.sub.y<n.sub.z. The b and Y axes are
colinear but opposite in direction, which is denoted by the cross
and dot signs. The crystal was cut with polished faces aligned at
an angle of approximately 34.degree. to the X-axis as shown in FIG.
5. The crystal surfaces were coated with an anti-reflective coating
that had less than 1% reflection at 1060, 530 and 812 nm. The
crystal absorbed approximately 80% of the pump light. Measurements
of the polarized absorption and emission spectra of 5% Nd:YCOB for
light polarized parallel to the X, Y, and Z axes were taken. The
results are shown in FIGS. 6 and 7; confirming that the strongest
absorption and emission of light occurs for light polarized
parallel to the Z-axis. Referring to FIG. 6, the several strong
absorption peaks in the vicinity of 800 nm make this material
attractive for laser diode pumping. It is again noted that with the
addition of diode pumping, the Nd:YCOB laser provides a type of
compact, high-power visible green laser light source.
[0040] From the foregoing experiments it was observed that diode
pumped self-frequency doubling in a Nd:YCOB laser system can be
demonstrated with a dichroic mirror coated directly on the face of
one of the polished crystal surfaces. SFD laser emission has been
observed with modest pump powers from a low brightness laser diode.
It is shown that the new material, Nd:YCOB, is a promising laser
crystal for development of the next generation of compact,
diode-pumped, solid-state, visible laser systems.
[0041] While the invention has been described, disclosed,
illustrated and shown in various terms of certain embodiments or
modifications which it is presumed in practice, the scope of the
invention is not intended to be, nor should it be deemed to be,
limited thereby and such other modifications or embodiments as may
be suggested by the teachings herein are particularly reserved
especially as they fall within the breadth and scope of the claims
here appended.
* * * * *