Diode-pumped, High-Power Nd:YLF and Nd:YVO4 Lasers
D. Lee, K.J. Snell, J.G. Manni, K.F. Wall,Y. Isyanova and P.F. Moulton
Solid State & Diode Laser Technology Review 20008 June, 2000
Albuquerque, NM
Outline
• Laser materials choices• Basic Nd:YLF laser design and performance• Basic Nd:YVO4 laser design and performance• MOPA systems• Applications
Three Nd Laser Hosts As Choices
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
MPS Pumping Design
Diode laser
Diode laser
Nd:YLF Lasercrystal
Cylinder lensLaserbeam
Pumpbeam
MPS gain module with resonator (MPS-1047)
AOQ-switch
Gain module
Diode Laser bar
Nd:YLF slab
Production data on MPS gain module
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.01 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Gain module number
Pow
er o
utpu
t (W
)
Average: 12.1 WMedian: 12.1 WStandard deviation: 0.9 W
0
1
2
3
4
5
6
7
8
10.5 11 11.5 12 12.5 13 13.5 14 14.5
Power output (W)
Num
ber o
f mod
ules
MPS Q-switching produces high powers
100 1000 10000 100000
Pulse rate (Hz)
Peak
Pow
er
MPS-E
MPS
1 MW
100 kW
10 kW
1 kW
CW oscillator performance scales upward
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80
Pump Power (W)
Out
put P
ower
(W)
40 W, MM30 W, MM30 W, TEMoo20 W, TEMoo
TEMoo properties are power-independent
0
0.2
0.4
0.6
0.8
1
1.2
1.4
35 40 45 50 55 60 65
Pump Power (W)
Bea
m D
iam
eter
(mm
)
0.95
1
1.05
1.1
1.15
1.2
1.25
1.3
M2
Horizontal Plane
Vertical Plane
Q-switched average power is nearly doubled with 50% more pump power
0
5
10
15
20
25
30
0.1 1 10 100
Pulse rate (kHz)
Ave
rage
pow
er (W
)
63 W40 W
Pumppower
Higher gain yields shorter pulses
0
50
100
150
200
250
300
10 20 30 40 50 60 70 80 90 100
Pulse rate (kHz)
Puls
ewid
th (n
s)
40 W63 W
Pumppower
Peak power is increased at high PRR
0.1
1
10
100
10 20 30 40 50 60 70 80 90 100
Pulse rate (kHz)
Peak
pow
er (k
W)
63 W40 W
Pumppower
High-power, MPV (Nd:YVO4) gain module
HR
HR
Collimated 20 WLaser Diode Bars
Nd:YVO4 Slab
MPV (Nd:YVO4 ) Oscillator CW Efficiency
0
2
4
6
8
10
12
14
16
0 10 20 30 40
Pump Power (W)
Out
put P
ower
(W)
1064 nm MM1064 nm TEMoo1342 nm TEMoo
• 1064 nm, >15 W multimode, >13 W TEM00, 46.3% slope, 35.0% optical and 13% electrical efficiency.
• 1342 nm, >6 W TEM00, 26% slope, 15% optical and 6% electrical efficiency.
MPS CW Amplifier Performance
• Gain of 17 with 27 mW input at a pump power of 38.7 W. 3-pass small signal gain >30 based on later single-pass measurements.
0
2
4
6
8
10
12
14
16
18
0 1 2 3 4 5
Input Power (W)
Gai
n
0
1
2
3
4
5
6
7
8
9
10
11
12
Out
put P
ower
(W)
GPo
MPS and MPV pulsewidth vs. rate
1
10
100
1000
1000 10000 100000 1000000
Pulse rate (Hz)
Puls
ewid
th (n
s)
MPS
MPV
MPS MOPA system #2 generates 50 W cw
EOQ-switch
Two-module Nd:YLF Oscillator1st StageAmplifier
2nd StageAmplifier
Cylinderlens
Cylinderlens50 W CW
40 W Q-Sw @ 5 kHz14-ns pulsewidth
MOPA #2 laser head
MOPA design allows scaling to 60 W cw
(20-W pump lasers)
50 W QS@ 5 kHz
60 W cw
GM
18 W
11 W10 W
GMIsolator QS
GM GM GM
28 W 40 W
Q-Switched, Nd:YLF, Master Oscillator
GM Gain ModuleRelay Optics
QSMirrors AO Q Switch
MOPA generates 54 W cw with one amplifier
(40-W pump lasers)
54 W cwwith 128 W total pumpM2 ≈ 1.1
MPV Nd:YVO4 MOPA System
Osc
AO Amp1 Amp2 Amp3Is
olat
orAmp4
Output
• 5 Gain Modules; 1 Oscillator, 4 Power Amplifiers. Same design for both 1064 nm and 1342 nm.
• Relay-imaged between master oscillator and amplifiers to preserve optimum beam size throughout the MOPA chain.
Nd:YVO4 MOPA Results
1064 nm• Outputs CW/Q-Switched @ 50 kHz
Oscillator: 11.4 W /10.5 W, 10 ns FWHMOutput: 53.5 W / 50.7 W, 10 ns FWHM, 1.01 mJ/pulse
101.4 kW Peak• 200 W pump power → >25% optical, >10% electrical efficiency.
1342 nm• Outputs CW/Q-switched @ 50 kHz
Oscillator: 11 W /9.6 W, 22 ns FWHM (Double crystal)Output: 26.5 W / 25.0 W, 22 ns FWHM, 0.5 mJ/pulse
23 kW Peak 240 W pump power → 10.4% optical, 4% electrical efficiency.
Nd:YLF harmonic conversion generates high visible, UV powers (with Ushio)
5HGCLBO
4HGCLBOBBOSHG LBO
Oven
0
1
2
3
4
5
6
7
0 2 4 6 8 10 12 14 16
SHG Average power (W)
4HG
Ave
rage
pow
er (W
)
0
10
20
30
40
50
60
70
Con
vers
ion
effic
ienc
y(%
)FHG powerEfficiency
SHG (523.5 nm):30 W at 67 kHzand 60-68% conversionin LBO
3HG (349 nm):6 W at 10 kHz (30%)15 W at 5 kHz in LBO
4HG (262 nm): 10 W at 5 kHz with CLBO2.5 W at 10 kHz in BBO
5HG (207 nm):2 W (internal)at 5 kHz with CLBO
3HGLBO
MPS-based 349-nm commercial product
A/O QS
Nd:YLF Oscillator Amplifier Gain Module
SHGLBO
THGLBO
1047 nm10 Watt
1047 nm20 Watt
1047 nm10 Watt
523 nm10 Watt
349 nm
1047 nmand523 nm
6 Watt
Schematic of RGB OPO
Type-IISHG LBO
Pump524 nm
Signal 898 nm +Green 524 nm
Red628 nm
Idler1256 nm
f = 29 mm
SWP: HR@ 1256 nm;HT@ 524, 628, and 898 nm
Intracavity SHG
Singly Resonant OPO Green524 nm
SWP
Signal898 nm
LWP
Walk-Off compensated
Type-I SHG LBO
Blue449 nm
Type-I OPO LBO
Watt-level doubled OPO outputs at 10 kHz
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 2 4 6 8 10 12
Green power (W)
Pow
er (W
)
SignalRedBlue
IR parametric oscillator systems
Intracavity OPO1 W output
at 1507 nm
12.5 kHz PRR
6 ns pulsewidthAO
Q-switch
Gain module
Diode Laser bar
Nd:YLF slab KTA 25 mm
External OPO
0
1
2
3
4
5
6
0 2 4 6 8 10 12 14
Pump power (W)
Sign
al p
ower
(W)
43% conversion to 1507 nm
5 kHz PRRQ-SW Pump
Signal
KTA 75 mm
Tuning curve for MPS-driven KTA OPO
0
1
2
3
4
5
6
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2
Wavelength (um)
Pow
er (W
)
Tandem OPO design gives full IR coverage
MPS MOPAPump laser KTA OPO CdSe OPO
1.5 - 3.6 µm
3 - 12 µ m
Angle-Tuned NCPM
Results to date:(At 4 kHz pulse rate, 30-W pump power)
•KTA signal at 1514 nm: 6.5 W•KTA idler at 3450 nm: 5 W•CdSe signal at 5120 nm: threshold•CdSe idler at 10570 nm: threshold
MPS modules amplify a mode-locked laser
(Modules pumped by 20-W bars)
0.7 W,4.5 ps @100 MHz
Amplified ML laser converts efficiently
SecondHarmonic
Crystal
NCPMLBO
AmplifiedML laser
CPMCLBO
FourthHarmonic
Crystal
2.9 W at262 nm
15.0 W at1047 nmM2 < 1.1
8.4 W at523.5 nmM2 < 1.1
MPV amplifies a micro-chip laser
HR mirrorFaraday rotator3 mW at 2 kHz, 400 ps pulsewidth
650 mW MPV gain moduleNd:YAG / Cr:YAGmicrochip laser
at 1064 nmNCPM LBO
SHG
390 mW, 2 kHz PRR at 532 nm
Summary
• Side-pumped Nd:YLF MPS and Nd:YVO4 MPV designs combine simplicity, scalability of side pumping with the high-efficiency, TEM00-mode performance of fiber-coupled, end-pumping designs.
• Recent availability of 40-W bars has more than doubled the output of MPS Nd:YLF “gain module” to > 25 W and increased peak power at high pulse rates. Nd:YVO4performance may improve as well, but strong thermal lensing will be a challenge.
• CW-pumped, Q-switched systems can efficiently drive nonlinear optics to generate tunable, vis-UV and IR wavelengths.
• Systems designers should consider cw-diode-pumped systems instead of pulsed-pumped systems for cost and reliability reasons.
Diode-pumped, High-Power Nd:YLF and Nd:YVO4 LasersOutlineThree Nd Laser Hosts As ChoicesMPS Pumping DesignMPS gain module with resonator (MPS-1047)Production data on MPS gain moduleMPS Q-switching produces high powersCW oscillator performance scales upwardTEMoo properties are power-independentQ-switched average power is nearly doubled with 50% more pump powerHigher gain yields shorter pulsesPeak power is increased at high PRRHigh-power, MPV (Nd:YVO4) gain moduleMPV (Nd:YVO4 ) Oscillator CW EfficiencyMPS CW Amplifier PerformanceMPS and MPV pulsewidth vs. rateMPS MOPA system #2 generates 50 W cwMOPA #2 laser headMOPA design allows scaling to 60 W cwMOPA generates 54 W cw with one amplifierMPV Nd:YVO4 MOPA SystemNd:YVO4 MOPA ResultsNd:YLF harmonic conversion generates high visible, UV powers (with Ushio)MPS-based 349-nm commercial productSchematic of RGB OPOWatt-level doubled OPO outputs at 10 kHzIR parametric oscillator systemsTuning curve for MPS-driven KTA OPOTandem OPO design gives full IR coverageMPS modules amplify a mode-locked laserAmplified ML laser converts efficientlyMPV amplifies a micro-chip laserSummary