Direct diode lasers with comparable beam quality to fiber, CO 2, and solid state lasers

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1 Direct diode lasers with comparable beam quality to fiber, CO 2, and solid state lasers Robin K. Huang, Bien Chann, James Burgess, Michael Kaiman, Robert Overman, John D. Glenn, and Parviz Tayebati Presented by Jay Liebowitz May 25, 2012

2 Outline Introduction and Wavelength Beam Combination Scaling the brightness of diode lasers 2-kW Fiber-Coupled Direct Diode Laser High brightness 500-W-class laser modules 2-kW direct diode laser Summary 1

3 Outline Introduction and Wavelength Beam Combination Scaling the brightness of diode lasers 2-kW Fiber-Coupled Direct Diode Laser High brightness 500-W-class laser modules 2-kW direct diode laser Summary 2

4 Introduction High power, high brightness laser sources are key to both the industrial and defense laser markets Industrial lasers are dominated by CO 2, bulk solid-state, and fiber lasers 1-10 kw with beam quality < 10 mm-mrad Diode lasers lack good beam quality State-of-art: at 10 kw, beam quality ~500 to 1000 mm-mrd Our approaches to high-power with comparable beam quality as CO 2, bulk solid-state, and fiber lasers Wavelength beam combining (WBC)- MIT LL invention Commercial off the shelf diode bars and stacks TeraDiode: multi-kw class direct diode lasers are more compact, more efficient and less expensive and more reliable! 3

5 Beam Quality (mm-mrad) High Power Industrial Lasers: Beam Quality versus Power Lamp pumped SSL CO 2 lasers 1 Disk lasers Fiber lasers Power (kw)

6 WBC Enables Material Processing using Direct Diode Lasers TDI s direct diode lasers Diode laser pumps Gas laser Fiber laser Doped fiber gain medium Nd:YAG laser Doped rod gain medium Disk laser Doped disk gain medium Welding, annealing, cutting and drilling of ferrous and nonferrous Rod Sheet Tubing Bar Semifinished parts CO 2 filled discharge tube Our direct diode lasers are simpler and more efficient while being comparable in brightness to best in class lasers 5

7 Wavelength Beam Combining Technology 1 Invented at MIT Lincoln Laboratory for defense applications Lens Diffraction Grating Diode laser brightness scaling TeraDiode improvements enable high efficiency and low cost Diode Laser Array Output Coupler 6

8 Wavelength Beam Combining Technology 2 Laser element: Power = P 0, Beam Quality= M 2 #1 #2 #n Dispersive Optics Single element output Input: Power = n P 0 Beam quality = n M 2 /ff (n=number of elements, ff=fill-factor) Output: Power = n P 0 ( =efficiency>0.80) Beam quality = M 2 Output power: sum of all input laser power Output beam quality: single element, single bar, or stack Brightness enhancement: n/ff Example: 30 elements with fill-factor 0.5 then brightness enhancement is 60x 7

9 Outline Introduction and Wavelength Beam Combination Scaling the brightness of diode lasers 2-kW Fiber-Coupled Direct Diode Laser High brightness 500-W-class laser modules 2-kW direct diode laser Summary 8

10 Wavelength-stabilized diode laser bar characteristics V PCE P L-I-V of passively cooled diode laser bar Power Conversion Efficiency at 50 A = 51% Diode laser efficiency above 55% WBC efficiency as high as 90% Wavelength stabilized to nm 9

11 High efficiency from many WBC diode lasers WBC Bar Power (W) Voltage (V) PCE (%) I = 85 A Statistics of seven diode laser bars Consistent, efficient WBC lasers

12 Relative Intensity (dbm) Wavelength is constant versus power W 52 W 36 W 19 W 2 W Wavelength (nm) 980 Diode laser bar Wavelength stabilized to nm Change in wavelength versus power = nm/w 11

13 Wavelength is constant versus temperature Diode laser bar Wavelength stabilized to nm in external cavity Change in wavelength versus temperature = nm/ C 12

14 Relative Intensity (dbm) Very broad tuning range, useful for pumps I=85 A I=50 A -50 I=50 A Wavelength (nm) 1000 Diode laser bar I = 50 A and 85 A Large wavelength tuning range Excellent 976 nm operation for fiber laser pumping 13

15 470 W direct diode laser with 100 mm output fiber PCE P V Maximum power >470 W Maximum PCE 35% Output fiber 100 mm/0.12 NA Brightness 130 MW/cm 2 -str 14

16 370 W direct diode laser with 50 mm output fiber PCE P V Maximum power 370 W Maximum PCE 36% Output fiber 50 mm/0.15 NA Brightness 257 MW/cm 2 -str 15

17 High efficiency laser module PCE P V Free-space output laser module with >540 W Beam quality suitable for coupling into 50 mm or 100 mm fiber PCE at 60 A = 52% PCE at 85 A = 48% (operation level, 540 W) 16

18 2000 W fiber-coupled direct diode laser >2,000 W out of processing fiber (LLK-D compatible) Processing output fiber (95% power content) 100 mm/0.11 NA 50 mm/0.11 NA Beam Parameter Product of 2.75 mm-mrad Comparable power and brightness to fiber laser Suitable for kw-class industrial laser cutting of sheet metal 17

19 TeraDiode s 2-kW fiber-coupled diode laser Fiber-coupled direct-diode laser > 2000 W in 50 mm/0.11 NA fiber (95% power content) 967 nm center wavelength 18

20 TeraDiode s industry leading brightness Company Power (W) Fiber (mm/na) - Stabilized Brightness (MW/cm 2 -sr) TDI 2000 W 2,030 50/0.11 Yes 2730 TDI 1000 W /0.14 Yes 778 TDI 450 W /0.10 Yes 194 Commercial Diode Laser 1 Commercial Diode Laser 2 2, /0.10 No /0.12 No 28 Over 50x higher brightness than the state-of-the-art in direct diode lasers Comparable brightness to kw-class industrial fiber lasers 19

21 Summary Direct diode lasers with the same brightness as fiber lasers Technology is scalable to higher brightness and power levels Potential enabler for Department of Defense applications 20

Simply Brighter: High Brightness Direct Diode Industrial Lasers. Fabtech 2012

Simply Brighter: High Brightness Direct Diode Industrial Lasers Fabtech 2012 Introduction: wavelength beam combining Our TeraDrive direct diode technology has the unique competitive advantage of high brightness