new high-power, diode- pumped solid state laser · 2014. 11. 6. · research division seo has been...
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![Page 1: NEW HIGH-POWER, DIODE- PUMPED SOLID STATE LASER · 2014. 11. 6. · RESEARCH DIVISION SEO HAS BEEN BUILDING DIODE-PUMPED LASERS SINCE 1986 n Single-frequency sources – 1-W, Nd:YAG](https://reader033.vdocuments.net/reader033/viewer/2022060921/60acb341b2a8fb412524f439/html5/thumbnails/1.jpg)
RESEARCHDIVISION
NEW HIGH-POWER, DIODE-PUMPED
SOLID STATE LASER
InterOpto '95, Makuhari Messe, Japan
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RESEARCHDIVISION OUTLINE
Introduction to SEO
Review of diode-pumped lasers
Prior SEO experience
Design goals
Laser performance
Product description
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RESEARCHDIVISION
SCHWARTZ ELECTRO-OPTICS (SEO) HAS FOUR DIVISIONS
CEO
ResearchDivision
Solid StateLasers Sensors Weapons
Simulation
l Advanced solid state lasers
l Lidar systemsl Diode-pumped
lasers
l Ti:sapphire lasersl Medical solid
state lasers
l Diode-laser-based ladar systems
l Diode-laser-based training systems
Dr. William C. Schwartz
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RESEARCHDIVISION
SEO HAS OFFERED COMMERCIAL LASER PRODUCTS SINCE 1987
n Laser 1-2-3– Multi-wavelength-capability, lamp-pumped solid state laser– 0.75, 1.06, 2.1, 2.9 μm wavelengths, others available
n Titan-CW– Tunable CW Ti:sapphire laser, 680-1100 nm– Standing-wave or single-frequency ring
n Titan-P– Pulsed, 100-mJ, Ti:sapphire laser, Nd:YAG pump included
n Titan-ML– Mode-locked Ti:sapphire laser, 100-fs pulses
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RESEARCHDIVISION
DIODE-LASER OPTICAL PUMPING SOURCES HAVE MANY ADVANTAGES
n High power densityn Precise control of pumped
volumen Long lifetimen High efficiencyn Low-voltage power supplyn Reduced heat load in laser
crystal
Opticalpump
Laser crystal
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RESEARCHDIVISION
SEO HAS BEEN BUILDING DIODE-PUMPED LASERS SINCE 1986
n Single-frequency sources– 1-W, Nd:YAG ring laser– 50-mW, Tm,Ho:YLF laser at 2.06 μm– 40-mW, tunable Cr:LiSAF ring laser, 810-850 nm
n Pulsed, Q-switched (2.5 mJ) miniature Nd:YAG laser
n Pulsed, 90-mJ Nd:YAG rod laser
n High-power, bar-pumped cw lasers– 1.6 W, 523-nm doubled CW Nd:YLF system– 6 W CW Nd:YVO4 fiber-pumped laser– Microlaser arrays in Nd:YAG, Tm,Ho:YLF and Er:YSGG– 4.5 W CW Tm,Ho:YLF laser at 2.06 μm
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RESEARCHDIVISION END-PUMPED LASER
Diode laser,side view
Pump optics
Laser crystal
Output mirrorDichroic coating
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RESEARCHDIVISION
HIGH-POWER DIODE LASERS ARE AVAILABLE IN SINGLE APERTURE AND LINEAR ARRAYS
w
w, Aperture
(μm)
Pout (W)
780-870 nm3 0.2
50 0.5100 1.2200 2.0370 3.0500 4.0
Single aperture Linear array
Pout = 5, 10, 15, 20 W
1 cm
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RESEARCHDIVISION
OPTICS CONVERT LINEAR ARRAYS TO END-PUMPING SOURCES
Diode Asphere Nd:YLF
CylinderLens
MicrolensArray
Lens ArrayMicrolensCylinder
SDLP6
0.5 mm, 0.2 NA (SDL)1.1 mm, 0.11 NA (OP)
OROPTOPWR
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RESEARCHDIVISION
SEO HAS BUILT EFFICIENT END-PUMPED Nd:YVO4 LASERS
4
5
0 2 4 6 8 10 120
1
2
3
9.7, 3.5
9.8, 4.2
1064
-nm
Out
put P
ower
(W)
Diode Power to Crystal (W)
Fiber-coupled pump
Microlens-coupled pump
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RESEARCHDIVISION
n >10 W of power output
n High TEM00 -mode beam quality, M² < 1.2
n Minimal effect of pump power on beam parameters
n Polarized
n High energies, peak powers in Q-switching
n Low cost
n No external cooling water
SEO SET DESIGN GOALS FOR THE NEXT LEVEL IN HIGH-POWER LASERS
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RESEARCHDIVISION SEO THEN SET DESIGN APPROACHES
n High efficiency in TEM00 mode– Reduces pump-power requirements, cost
n Simple optics for coupling bars to laser crystal– More reliable– Lower cost
n High gain– More tolerant to cavity losses– Generates short Q-switched pulses
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RESEARCHDIVISION THREE LASER HOSTS ARE AVAILABLE
Crystal Thermalconductivity
(W/m K)
Expansioncoeff.(10-6)
Thermalshock(W/m)
dn/dT(10-6)
Lensing
YAG 13 6.7 1450 +7.3 moderateYLF 5.8 (c)
7.2 (a)8 (c)13(a)
240 -4.3 (e)-2.0 (o)
weak
YVO4 5.2 7.3 (a)?? (c)
? +2.9 (e)+8.5 (o)
strong
Crystal Wavelength (nm)
Gain cross section
(10-19 cm2)
Lifetime(μs)
Peak absorption
(cm-1)YAG 1065 3.3 240 10YLF (π)YLF (σ)
10471053
1.9-2.3π / 1.5
480-520 11
YVO4 (π) 1064 9.8-15.6 97 40
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RESEARCHDIVISION SEO CHOSE YLF AS THE LASER CRYSTAL
Advantages
– Weak thermal lensing reduces connection between beam properties and pump power
– Natural birefringence eliminates depolarization from stress-induced birefringence
– Long lifetime maximizes energy in Q-switched pulse
Challenge– Fracture a greater concern than with YAG
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RESEARCHDIVISION
SEO HAS DEVELOPED A SIDE-PUMPED, MULTIPASS GAIN ELEMENT
Nd:YLF right parallelpiped, transversely pumpedby a pair of 20-W diode-laser bars.
Bars (coupled through fiber lenses) to establishplanar gain region.
Segmented coatings or external mirrors for multiplepasses through gain region.
1047 nm, linear polarization (c-axis perpendicular toplane of propagation
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RESEARCHDIVISION MULTI-PASS SLAB DESIGN IS SIMPLE
20-W linear array
20-W linear array
Cylinder lens
Cylinder lens
Nd:YLFcrystal
Cavitymode
l Multi-pass design extracts large fraction of available power in TEM00
mode, has high gainl Low average excitation density minimizes stress, beam distortionl Simple, single-element pump optics
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RESEARCHDIVISION
CAVITY DESIGN FILLS GAIN REGION WITH TEM00
MODE
50% ROutputmirror
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RESEARCHDIVISION
LASER OUTPUT EXCEEDS 10 W IN A HIGH-QUALITY BEAM
0
3
6
9
12
15
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0
INCIDENT PUMP POWER (W)
OU
TPU
T PO
WER
(W)
0
0.25
0.5
0.75
1
1.25
1.5
1/e2
MO
DE
DIA
MET
ER (m
m)
tangential plane
sagittal plane
M² =1.1M² =1.1
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RESEARCHDIVISION
AN ACOUSTO-OPTIC Q-SWITCH CAN BE ADDED TO THE SYSTEM
AO Q-switch
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RESEARCHDIVISION
Q-SWITCHING PRODUCES >3 mJ PULESAT 2 kHZ, >10 W AVERAGE POWER
0
1
2
3
4
5
6
7
1 10 100
PULSE RATE (kHz)
PULS
E EN
ERG
Y (m
J)
7
8
9
10
11
12
13
14
AVE
RA
GE
POW
ER (W
)
PULSE ENERGY DATATHEORY (450 us)AVERAGE POWER DATA
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RESEARCHDIVISION
Q-SWITCHING GENERATES 100 kW OF PEAK POWER, < 40 ns PULSEWIDTH
0
20
40
60
80
100
120
1 10 100
PULSE REPETITION RATE (kHz)
PEA
K P
OW
ER (k
W)
0
75
150
225
300
375
450
FWH
M P
ULS
EWID
TH (n
s)
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RESEARCHDIVISION
EXTERNAL DOUBLING OF Q-SWITCHEDLASER PRODUCES 6.8 W AVERAGE POWER
Nd:YLF Q-switched laserNd:YLF Q-switched laser LBO
15-mm-long crystalNCPM Type I172 C
6.8 W at 523.5 nm10 kHz rate
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RESEARCHDIVISION SUMMARY OF LASER PERFORMANCE
Typical performance (5-pass, 1047 nm): 13 W, M² =1.1.
70% of theoretical slope efficiency with M² <1.2.
>3 mJ (>100 kW) Q-switched at 2 kHz.
SHG demonstration (523.5 nm): 6.8 W (61%) at 10 kHz.
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RESEARCHDIVISION
SEO HAS DEVELOPED A POWER SUPPLY/ COOLING SYSTEM FOR LASER HEAD
Power supply/cooler Laser headl Diode powerl Cooling water for
diodes, Nd:YLFl Q-switch drivel Interlocks
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RESEARCHDIVISION
n ReliableNo mechanical refrigerator
n Compact
n Universal-voltage operation
n Constant-temperature coolingMaintain stable operating point for laser
DESIGN GOALS FOR POWER SUPPLY/COOLER
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RESEARCHDIVISION
SEO USES SWITCHING POWER SUPPLIES AND THERMOELECTRIC COOLING
n Switching power supplies– Universal power (90-250 VAC, 47-63 Hz)– Power-factor corrected– Lightweight
n Thermoelectric coolers for water– Solid state, no compressor– Excellent water temperature control, no cycling– Hot side of thermoelectric cooler is forced-air cooled
n DC motor on water pump, cooling fans– Powered by switching supply
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RESEARCHDIVISION
MPS-1047Q Laser Head– Pulse rate: 2 - 100 kHz– Pulse energy:
> 3 mJ at 2 kHz> 1 mJ at 10 kHz
– Pulsewidth:< 40 ns at 2 kHz< 75 ns at 10 kHz
PRODUCT SPECIFICATIONS
MPS-1047 Laser Head– CW power output : > 10 W– Mode: TEM00 , M² < 1.2– Wavelength: 1047 nm– Linear polarization: > 100:1
SSC-40 Controller– Operating voltage: 90-235 VAC at
47-63 Hz– Power consumption: 1 kW for 25
C ambient
Note: Specifications subject to change without notice
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RESEARCHDIVISION DRAWING OF SSC-40 CONTROLLER/COOLER
20.00017.000
Coolant
Set Point
LASER CONTROL UNIT
SSC-40
Power
OffOn
On/Off
Laser
Fault
On
Off
Cold
Hot
14.000
Dimensions in inchesSpecifications subject to change without notice
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RESEARCHDIVISION OEM VERSIONS
SEO will be happy to discuss custom versions of this laser systems and other diode-pumped lasers in general with interested customers. Please contact us with your requirements.