High-Efficiency, High-Power OPO-based RGB Source

Dicky Lee, Peter F. MoultonQ-Peak, Inc. 135 South Road, Bedford, MA 01730

Support: AFRL (WPAFB) Phase I and II SBIRsContract F33615-99-C-6009, Reginald Daniels

Paper CTHJ2 - CLEO 2001May 10

Baltimore, MD

Outline

• Background

• Review of prior results

• Scaling to higher powers

OPO-based RGB source

1-um Laser SHG

1047 nm 523 nm

OPO

SHG

SHG Blue

Green

Red

898 nm

1256 nm

449 nm

628 nm

U.S. Patent #5,740,190

Relation between red and blue wavelengths

540

550

560

570580

590

600

610

620

630

640

650660

670

680

690

700

430 435 440 445 450 455 460 465 470 475 480 485 490

Doubled signal wavelength (nm)

Dou

bled

idle

r wav

elen

gth

(nm

)

1064 nm

1047 nm

1030 nm

1080 nm

RGB OPO provides large color gamut

610

PINK

PURPLISHPINK

RED

PURPLISHRED

REDDISHPURPLE

PURPLE

BLUE

GREENISHBLUE

BLUISHGREEN

GREEN

YELLOWISHGREEN

WHITE

YELLOWISH

PINK

20000

10000

6000

4000

30002000

B

E

CD

65

GREENISHYELLOW

YELLOWORANGE

PURPLISH BLUE

680650630

600590

570550530520

490

480

470

460

440

380-420 nm

700-780 nm

∞

LASE

R

CRT

LIQUI

D CRY

STAL

Δ SMPTE 240M

Δ

Δ

Δ

C.I.E. 1976 U.C.S.ChromaticityDiagram

GRA00001

OPO pump laser design is side-pumped

Diode laser

Diode laser

Lasercrystal

Cylinder lens Laserbeam

Pumpbeam

Multi-Pass Slab (MPS)US Patent 5,774,489

Photograph of Gain Module

With the side-pumped design, diode to laser conversion is in the 35-46% range

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

Prior RGB OPO Results

Old pump-laser configuration produced10W at a 10-kHz pulse rate

Nd:YLF Oscillator

A/O QS

10 W at1047 nm

AmplifierGain Module

20 W at1047 nm

Pulse rate: 10 kHz

SecondHarmonic

Crystal

NCPMLBO

10 W at523.5 nm

A temperature-tuned NCPM LBO OPO is the key element in the system

600700800900

1000110012001300140015001600170018001900

100 110 120 130 140 150 160 170 180

Temperature (C)

Sign

al, i

dler

wav

elen

gth

(nm

)

IdlerSignal

523.5-nm pump

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

OPO efficiency exceeded 60%

0

0.5

1

1.5

2

2.5

3

3.5

4

0 1 2 3 4 5 6 7 8 9 10Pump Power (W)

Out

put P

ower

(W)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

Effic

ienc

y

1256 nm

898 nmEfficiency

Watt-level doubled OPO outputs were generated

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

Latest RGB OPO Results

The new pump laser design generates30 W of power from 10 - 50 kHz

30 W @523.5 nm10-50 kHzM2 ≈ 1.1

Oscillator

Amplifier

Gain Modules

26 W (CW)

LBO doubler

52 W (CW)

Total pump power:128 W (optical)

Pump laser IR to green conversion is 60%

0

10

20

30

40

50

60

1000 10000 100000

Pulse rate (Hz)

Ave

rage

pow

er (W

)

1047 nm523.5 nm

Time

Inte

nsity

[A.U

.]

Before

After

OPO pump pulse time trace

~ 80% pump depletion

High-power operation - The numbers

Wavelength Power (W)1047 nm (MOPA output) 50.0524 nm (before OPO) 30.0898 nm (signal) 13.0524 nm (residual) 5.8628 nm (red) 6.0449 nm (blue) 3.4 - 4.0

Conversion process Efficiency (%)1047 nm to 524 nm (Green) 60Green to 628 (Red) 20Green to 898 nm 43898 nm to 449 nm (Blue) 27 - 31

RGB OPO in the laboratory

Luminosity of the RGB OPO

1000 lumens of D65-balanced white requires:

1.42 W @ 628 nm1.33 W @ 524 nm0.85 W @ 449 nm

Red: 6.0 W => 4219 lumensGreen: 5.8 W => 4347 lumensBlue: 3.4 W => 4009 lumens

Electrical luminous efficiency

Electrical power consumptionLaser diodes: 260 WQ-switch: 20 WOven: 40 WOthers: 45 WTotal: 365 W

=> 4000 lumens = 11.0 lumens/W360 W

Semi-packaged RGB-OPO Light Source

RGB optics (pump and OPO)packaged in 23” rack chassis

Pump oscillator

OPO andred SHG

BlueSHG

Pump amplifier

LBO doubler

RGB fiber outputs

Entire system package withcontroller, power supply and chiller

RGB optics

Controllerelectronics

Power supply

Cooler

Summary

• With 30 W of pump power,OPO-based RGB source has been scaled to generate:– 6 W at 628 nm– 3.4 - 4 W at 449 nm– 5.8 W of residual pump at 524 nm

• Optical power is equivalent to >4000 lumens• Efficiency is 11 lumens/W of electrical power• Power scalable to 8000 lumens?

– 40 W pump power per diode bar– additional amplifier– maximum output per OPO unit TBD