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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 2 — Jan. 17, 2011
  • pp: 1228–1235
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16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers

André Müller, Deepak Vijayakumar, Ole Bjarlin Jensen, Karl-Heinz Hasler, Bernd Sumpf, Götz Erbert, Peter E. Andersen, and Paul Michael Petersen  »View Author Affiliations


Optics Express, Vol. 19, Issue 2, pp. 1228-1235 (2011)
http://dx.doi.org/10.1364/OE.19.001228


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Abstract

Up to 16 W output power has been obtained using spectral beam combining of two 1063 nm DBR-tapered diode lasers. Using a reflecting volume Bragg grating, a combining efficiency as high as 93.7% is achieved, resulting in a single beam with high spatial coherence. The result represents the highest output power achieved by spectral beam combining of two single element tapered diode lasers. Since spectral beam combining does not affect beam propagation parameters, M2-values of 1.8 (fast axis) and 3.3 (slow axis) match the M2- values of the laser with lowest spatial coherence. The principle of spectral beam combining used in our experiments can be expanded to combine more than two tapered diode lasers and hence it is expected that the output power may be increased even further in the future.

© 2011 OSA

1. Introduction

Since their development, it has always been a goal to increase the output power of diode lasers. Although a lot of efforts have been put into diode laser technology, there are still some fundamental issues that limit the output power. One major problem, especially for CW lasers, is the heat generated [1

1. O. Svelto, S. Longhi, G. Della Valle, S. Kück, G. Huber, M. Pollnau, H. Hillmer, S. Hansmann, R. Engelbrecht, H. Brand, J. Kaiser, A. B. Peterson, R. Malz, S. Steinberg, G. Marowsky, U. Brinkmann, D. Lot, A. Borsutzky, H. Wächter, M. W. Sigrist, E. Saldin, E. Schneidmiller, M. Yurkov, K. Midorikawa, J. Hein, R. Sauerbrey, and J. Helmcke, “Lasers and Coherent Light Sources,” in Springer Handbook of Lasers and Optics, F. Träger, ed. (Springer Science and Business Media, New York, 2007).

]. The output power is mostly limited by heat effects causing degradation and optical damage. One way of increasing the output power while maintaining the beam quality, is to use beam combining [2

2. U. Brauch, P. Loosen, and H. Opower, “High-Power Diode Lasers for Direct Applications,” in High Power Diode Lasers: Fundamentals, Technology, Applications, R. Diehl, ed. (Springer, Berlin, 2000).

]. This principle basically describes the combination of two or more moderately operated lasers by an external optical element without affecting the beam quality. This allows for high-power laser systems with increased brightness.

There are two techniques, coherent and incoherent beam combining [2

2. U. Brauch, P. Loosen, and H. Opower, “High-Power Diode Lasers for Direct Applications,” in High Power Diode Lasers: Fundamentals, Technology, Applications, R. Diehl, ed. (Springer, Berlin, 2000).

,3

3. T. Y. Fan, “Laser beam combining for high-power, high-radiance sources,” IEEE J. Sel. Top. Quantum Electron. 11(3), 567–577 (2005). [CrossRef]

]. In both cases the beams are combined using different optical elements. Power scaling is simply done by increasing the number and/or the output power of the individual lasers. In coherent beam combining a precise control of wavelengths and relative phases of the gain elements are required. Only if single frequency operation and phase stabilization are achieved, the individual fields will add constructively in the near and far-field. This of course becomes more challenging the more elements that have to be combined. However, several hundreds of watts have been reported by several groups based on coherent beam combining of fiber laser arrays [4

4. T. H. Loftus, A. M. Thomas, M. Norsen, J. Minelly, P. Jones, E. Honea, S. A. Shakir, S. Hendow, W. Culver, B. Nelson, and M. Fitelson, “Four-Channel, High Power, Passively Phase Locked Fiber Array,” in Advanced Solid-State Photonics, OSA Technical Digest Series (CD) (Optical Society of America, 2008), paper WA4.

,5

5. G. Goodno, C. Asman, J. Anderegg, S. Brosnan, E. Cheung, D. Hammons, H. Injeyan, H. Komine, W. Long, M. McClellan, S. McNaught, S. Redmond, R. Simpson, J. Sollee, M. Weber, S. Weiss, and M. Wickham, “Brightness-Scaling Potential of Actively Phase-Locked Solid-State Laser Arrays,” IEEE J. Sel. Top. Quantum Electron. 13(3), 460–472 (2007). [CrossRef]

]. Beam combining efficiencies, representing the ratio of the combined power to the sum of power emitted from the individual gain elements, of more than 90% can be reached using this technique [6

6. A. Shirakawa, T. Saitou, T. Sekiguchi, and K. Ueda, “Coherent addition of fiber lasers by use of a fiber coupler,” Opt. Express 10(21), 1167–1172 (2002). [PubMed]

,7

7. A. A. Ishaaya, N. Davidson, and A. A. Friesem, “Passive laser beam combining with intracavity interferometric combiners,” IEEE Sel. Top. Quantum Electron. 15(2), 301–311 (2009). [CrossRef]

]. When looking for an alternative to sophisticated fiber lasers, diode lasers offer lower optical output powers but very high optical conversion efficiencies [8

8. A. Knigge, G. Erbert, J. Jonsson, W. Pittroff, R. Staske, B. Sumpf, M. Weyers, and G. Trankle, “Passively cooled 940 nm laser bars with 73% wall-plug efficiency at 70 W and 25°C,” Electron. Lett. 41(5), 250–251 (2005). [CrossRef]

,9

9. M. Kanskar, T. Earles, T. Goodnough, E. Stiers, D. Botez, and L. Mawst, “73% CW power conversion efficiency at 50 W from 970 nm diode laser bars,” Electron. Lett. 41(5), 245–247 (2005). [CrossRef]

]. Moreover, due to their reduced dimensions such lasers allow for compact combining systems with increased cost-effectiveness. In this regard 12.8 W of output power was achieved when coherently adding a 47 emitter array [10

10. B. Liu, Y. Liu, and Y. Braiman, “Coherent beam combining of high power broad-area laser diode array with a closed-V-shape external Talbot cavity,” Opt. Express 18(7), 7361–7368 (2010). [CrossRef] [PubMed]

].

When coherence is not the important issue, incoherent beam combining can be used [3

3. T. Y. Fan, “Laser beam combining for high-power, high-radiance sources,” IEEE J. Sel. Top. Quantum Electron. 11(3), 567–577 (2005). [CrossRef]

]. The biggest advantages here are the reduced tolerance requirements allowing for much simpler setups. One example is polarization coupling [11

11. B. Thestrup, M. Chi, B. Sass, and P. M. Petersen, “High brightness laser source based on polarization coupling of two diode lasers with asymmetric feedback,” Appl. Phys. Lett. 82(5), 680–682 (2003). [CrossRef]

]. With this method, two orthogonally polarized laser beams are combined using components like a thin film polarizer, polarizing beam splitters and others. The resulting beam is a single unpolarized beam with the added power of the individual lasers. But due to the requirements of orthogonal polarizations, power scaling just by increasing the number of comparable lasers is not possible.

An example suitable for power scaling is spectral beam combining (SBC) [2

2. U. Brauch, P. Loosen, and H. Opower, “High-Power Diode Lasers for Direct Applications,” in High Power Diode Lasers: Fundamentals, Technology, Applications, R. Diehl, ed. (Springer, Berlin, 2000).

,3

3. T. Y. Fan, “Laser beam combining for high-power, high-radiance sources,” IEEE J. Sel. Top. Quantum Electron. 11(3), 567–577 (2005). [CrossRef]

]. Here, two or multiple lasers at slightly different wavelengths are combined. The spectrum then consists of multiple peaks corresponding to the individual laser emissions. As for coherent beam combining the highest output powers are achieved using fiber lasers. In this respect 522 W of average output power with a combining efficiency of 93% was reported when using a surface grating [12

12. T. H. Loftus, A. Liu, P. R. Hoffman, A. M. Thomas, M. Norsen, R. Royse, and E. Honea, “522 W average power, spectrally beam-combined fiber laser with near-diffraction-limited beam quality,” Opt. Lett. 32(4), 349–351 (2007). [CrossRef] [PubMed]

]. With a reduced combining efficiency of 61% even 2 kW of power was shown [13

13. C. Wirth, O. Schmidt, I. Tsybin, T. Schreiber, T. Peschel, F. Brückner, T. Clausnitzer, J. Limpert, R. Eberhardt, A. Tünnermann, M. Gowin, E. ten Have, K. Ludewigt, and M. Jung, “2 kW incoherent beam combining of four narrow-linewidth photonic crystal fiber amplifiers,” Opt. Express 17(3), 1178–1183 (2009). [CrossRef] [PubMed]

]. Reaching these high output powers makes the combination of fiber lasers very attractive for certain applications. However, when focusing on applications requiring only several tens of Watts, e.g. welding of polymers and metal foils [14

14. W. Schulz and R. Poprawe, “Manufacturing with novel high-power diode lasers,” IEEE J. Sel. Top. Quantum Electron. 6(4), 696–705 (2000). [CrossRef]

], bending of glass and ceramics [15

15. D. Wu, Q. Zhang, G. Ma, Y. Guo, and D. Guo, “Laser bending of brittle materials,” Opt. Lasers Eng. 48(4), 405–410 (2010). [CrossRef]

], soldering of electric circuit boards [16

16. C. Roychoudhuri, “Desk-top manufacturing using diode lasers,” Proc. SPIE 3274, 162–170 (1998). [CrossRef]

], marking of plastics [16

16. C. Roychoudhuri, “Desk-top manufacturing using diode lasers,” Proc. SPIE 3274, 162–170 (1998). [CrossRef]

] or sintering of metal powders [16

16. C. Roychoudhuri, “Desk-top manufacturing using diode lasers,” Proc. SPIE 3274, 162–170 (1998). [CrossRef]

,17

17. H. Shabir, B. Lal, and M. Rafat, “A comparative study of the properties of terbium aluminum garnet powder sintered in air, vacuum and by laser irradiation,” Ceram. Int. 36(1), 365–369 (2010). [CrossRef]

], using high power fiber lasers would not fully exploit their potentials. In this regard diode lasers represent a suitable alternative. Besides their advantages mentioned above, diode lasers also offer a wider range of wavelengths due to their material compositions [18

18. M. Behringer, “High-Power Diode Laser Technology and Characteristics,” in High Power Diode Lasers: Technology and Applications, F. Bachmann, P. Loosen, and R. Poprawe, ed. (Springer, Berlin, 2007)

]. This might provide additional advantages for certain applications and even enable new applications not accessible using laser emissions based on atomic transitions. Furthermore, these applications may benefit from the possibility of power scaling using diode lasers.

When combining single lasers instead, the resulting beam quality matches the value of the individual lasers. This immediately increases the chance of achieving a combined near diffraction limited beam just by choosing the proper lasers. Regarding SBC of individual lasers with smaller wavelength separations, volume Bragg gratings (VBG) have been shown to be a suitable alternative [22

22. O. Andrusyak, V. Smirnov, G. Venus, and L. Glebov, “Beam combining of lasers with high spectral density using volume Bragg gratings,” Opt. Commun. 282(13), 2560–2563 (2009). [CrossRef]

,23

23. A. Sevian, O. Andrusyak, I. Ciapurin, V. Smirnov, G. Venus, and L. Glebov, “Efficient power scaling of laser radiation by spectral beam combining,” Opt. Lett. 33(4), 384–386 (2008). [CrossRef] [PubMed]

]. In these experiments five diode lasers as well as five fiber lasers emitting at around 1060 nm and spectrally spaced 0.5 nm were successfully combined. Written in photo-thermo-refractive (PTR) glass such gratings offer excellent thermo-mechanical properties, high transmittance in the visible and near-infrared, polarization insensitivity and diffraction efficiencies exceeding 99% [24

24. O. Andrusyak, V. Smirnov, G. Venus, V. Rotar, and L. Glebov, “Spectral Combining and Coherent Coupling of Lasers by Volume Bragg Gratings,” IEEE Sel. Top. Quantum Electron. 15(2), 344–353 (2009). [CrossRef]

]. These characteristics make volume Bragg gratings (VBG) suitable for compact and robust high power, high brightness, beam combining systems. In this respect a maximum of 770 W was achieved coupling 5 fiber lasers with a combining efficiency of 91.7% [24

24. O. Andrusyak, V. Smirnov, G. Venus, V. Rotar, and L. Glebov, “Spectral Combining and Coherent Coupling of Lasers by Volume Bragg Gratings,” IEEE Sel. Top. Quantum Electron. 15(2), 344–353 (2009). [CrossRef]

]. Comparable combining efficiencies of 92% - 94% were achieved coupling 5 low power fiber-pigtailed diode lasers [22

22. O. Andrusyak, V. Smirnov, G. Venus, and L. Glebov, “Beam combining of lasers with high spectral density using volume Bragg gratings,” Opt. Commun. 282(13), 2560–2563 (2009). [CrossRef]

]. This also proofs the reliability of such gratings within a large power range. The increase in combining efficiency compared to the combining of diode laser arrays [21

21. D. Vijayakumar, O. B. Jensen, R. Ostendorf, T. Westphalen, and B. Thestrup, “Spectral beam combining of a 980 nm tapered diode laser bar,” Opt. Express 18(2), 893–898 (2010). [CrossRef] [PubMed]

] might result from an increased flexibility in terms of optical alignments and adjustments of laser parameters.

In this paper, we present spectral beam combining of high-power 1060 nm DBR-tapered diode lasers using a volume Bragg grating. Previously, such lasers have been demonstrated to emit 12 W of output power with nearly diffraction limited beam qualities measured up to 10 W [25

25. B. Sumpf, K.-H. Hasler, P. Adamiec, F. Bugge, F. Dittmar, J. Fricke, H. Wenzel, M. Zorn, G. Erbert, and G. Tränkle, “High-Brightness Quantum Well Tapered Lasers,” IEEE Sel. Top. Quantum Electron. 15(3), 1009–1020 (2009). [CrossRef]

]. By combining two lasers, spectrally separated by 0.5 nm, we achieve a single beam with 16 W of output power and a beam quality of 1.8 (fast axis) and 3.3 (slow axis). To the best of our knowledge this represents the highest output power in spectral beam combining of single emitter diode lasers. The corresponding combining efficiency of 93.7% is comparable to the values reported above and even slightly increased to 95.4% at low powers.

These results clearly indicate the feasibility of simple, high-efficient, compact diode laser based light sources. By combining multiple high-power DBR-tapered diode lasers, future systems could then offer several tens of Watts with single, near diffraction limited output beams. As a consequence, this would make these light sources interesting for applications within materials processing as mentioned above.

2. Experimental setup

The configuration of the setup for spectral beam combining is shown in Fig. 1
Fig. 1 Sketch of the spectral beam combining setup based on two DBR-tapered diode lasers and a reflecting volume Bragg grating. The beam transmitting the grating is indicated by dashes, the diffracted beam by dots. The arrow signifies the propagation of the combined beam.
. A detailed description of the structure and layout of the 1060 nm DBR-tapered diode lasers can be found in [25

25. B. Sumpf, K.-H. Hasler, P. Adamiec, F. Bugge, F. Dittmar, J. Fricke, H. Wenzel, M. Zorn, G. Erbert, and G. Tränkle, “High-Brightness Quantum Well Tapered Lasers,” IEEE Sel. Top. Quantum Electron. 15(3), 1009–1020 (2009). [CrossRef]

,26

26. K.-H. Hasler, B. Sumpf, P. Adamiec, F. Bugge, J. Fricke, P. Ressel, H. Wenzel, G. Erbert, and G. Tränkle, “5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality,” IEEE Photon. Technol. Lett. 20(19), 1648–1650 (2008). [CrossRef]

]. Each of the 6 mm long lasers is mounted p-side up on a CuW heat spreader, which itself is mounted on a 25 x 25 mm2 conduction cooled package (CCP) mount allowing for efficient cooling. The current to the ridge and the tapered section of both lasers are controlled individually. Each laser is collimated in both axes using AR-coated lenses to avoid optical feedback. Collimating the fast axes is done by aspheric lenses with a focal length of 3.1 mm and a numerical aperture of 0.68. The slow axes are collimated by cylindrical lenses with a 15 mm focal length. This generates a nearly circular beam around 2 mm in diameter and compensates for astigmatism, originating from the tapered diode laser. Since the astigmatism of these lasers changes with current, the setup allows for correcting the position of the cylindrical lenses when changing the injection currents.

The grating (OptiGrate) is a reflecting VBG, meaning the planes of constant refractive index are parallel to the surface of the PTR glass [22

22. O. Andrusyak, V. Smirnov, G. Venus, and L. Glebov, “Beam combining of lasers with high spectral density using volume Bragg gratings,” Opt. Commun. 282(13), 2560–2563 (2009). [CrossRef]

]. Therefore the transmitting beam (dashes) passes through and the diffracted beam (dots) reflects back to the same side of the grating as the incoming beam. Due to the unique performance of such Bragg gratings, having diffraction efficiencies close to unity when the Bragg condition is fulfilled and close to zero at multiple points offset from this condition, optimum SBC is achieved by adjusting the angles of incidence and wavelengths properly. The spectral spacing between maximum diffraction and zero diffraction depends on the spatial frequency of the grating [28

28. I. V. Ciapurin, L. B. Glebov, and V. I. Smirnov, “Modeling of phase volume diffractive gratings, part 1: transmitting sinusoidal uniform gratings,” Opt. Eng. 45(1), 015802 (2006). [CrossRef]

]. According to the specification sheet the VBG used in this setup (L x W x H = (3.4 x 10 x 10) mm3) has an average diffraction efficiency of 99.2% at 1062 nm and a spectral selectivity of 0.3 nm (FWHM).

3. Individual laser characterization

As discussed above, the injection currents for the ridge and the tapered section of both lasers are controlled individually. For all experiments, the DBR ridge sections are operated constantly at 300 mA. Therefore the term injection current in the following text and figures refers to the tapered sections only. Additionally, the laser whose beam is transmitted by the grating hereinafter is referred to as transmitted laser, the laser whose beam is diffracted as diffracted laser. Figure 2a
Fig. 2 (a) Power current characteristics of DBR-tapered diode lasers at 300 mA to the ridge section and operating temperatures of 20 °C. (b) Optical spectra of the lasers at 14 A to the tapered section.
shows the power-current characteristics of both lasers at laser temperatures of 20 °C. At 14 A, the diffracted laser emits 8.46 W of output power and the transmitted laser 8.92 W. The slope efficiencies are 0.71 W/A and 0.74 W/A, respectively. Within the measured current range both lasers show no signs of thermal roll over.

At maximum current the centre wavelengths are 1062.92 nm for the diffracted laser and 1063.01 nm for the transmitted laser (Fig. 2b). All spectra are measured with an Advantest Q8347 optical spectrum analyzer. Due to the intrinsic wavelength stabilization DBR-tapered diode lasers emit light in single longitudinal modes, resulting in spectral widths below 10 pm (FWHM). In both cases side mode suppression above 25 dB is achieved limited by the dynamic range of the optical spectrum analyzer.

The optimum SBC requires a proper adjustment of wavelengths. There are different ways of tuning the emission wavelengths of diode lasers. One of them is by changing the injection current (Fig. 3a
Fig. 3 (a) Wavelength versus injection current of DBR-tapered diode lasers at 300 mA to the ridge section and operating temperatures of 20 °C. (b) Wavelength versus temperature of the lasers at 14 A to the tapered section.
). Assuming a linear dependence at higher currents a shift towards longer wavelengths of 0.02 nm/A is measured. Another and more effective way is by changing the laser temperature (Fig. 3b). At maximum current a shift of 0.09 nm/K is observed. With the given spectral characteristics and the wavelengths being tunable, both lasers are suited for spectral beam combining with the specified grating.

Additionally, the beam propagation parameters (M2 1/e 2) are calculated by measuring the beam widths along the beam waists of the focused beams. This is done using an additional spherical lens with a focal length of 120 mm and a Photon, Inc. beam scanner. The measured widths are then fitted to a hyperbolic equation. At maximum current, the values for the diffracted laser are 1.4 (fast axis) and 3.2 (slow axis). The transmitted laser shows 1.5 (fast axis) and 2.1 (slow axis). In comparison, the decrease in beam quality for the diffracted laser could be explained by side lobes in the beam profile, therefore increasing the measured beam widths using the 1/e2 criteria.

A more thorough characterization of comparable lasers including the beam profiles, astigmatism and power current characteristics at different current settings can be found in [25

25. B. Sumpf, K.-H. Hasler, P. Adamiec, F. Bugge, F. Dittmar, J. Fricke, H. Wenzel, M. Zorn, G. Erbert, and G. Tränkle, “High-Brightness Quantum Well Tapered Lasers,” IEEE Sel. Top. Quantum Electron. 15(3), 1009–1020 (2009). [CrossRef]

].

4. Spectral beam combining of two tapered diode lasers

The optimum SBC is obtained only by the proper adjustment of the angles of incidence and the emission wavelengths. Figure 4a
Fig. 4 (a) Output power of the individual lasers and the combined beam at 300 mA to the ridge section and different injection currents to the tapered section. The angles of incidence and the laser temperatures are adjusted for maximum diffraction and transmission at each current value. Star symbols indicate the corresponding combining efficiency achieved at each current. (b) Optical spectrum of the combined output beam at 14 A to the tapered section.
shows the measured output power achieved with spectral beam combining at various injection currents.

At each current value, the angles of incidence and wavelengths are adjusted for maximum transmission and diffraction. The highest combined output power at maximum current is 16.08 W corresponding to an electro-optical efficiency of about 25%. At this current, the transmitted laser is operated at 15.47 °C, emitting 9.11 W at 1062.65 nm and the diffracted laser is operated at 23.0 °C, emitting 8.05 W at 1063.17 nm, resulting in a combining efficiency of 93.7%. A slight increase in combining efficiency is measured at lower currents. Observations with lower efficiencies in high-power regimes are usually associated with a slight degradation of laser parameters rather than deteriorating grating parameters [27

27. I. V. Ciapurin, L. B. Glebov, L. N. Glebova, V. I. Smirnov, and E. V. Rotari, “Incoherent combining of 100-W Yb-fiber laser beams by PTR Bragg grating,” Proc. SPIE 4974, 209–219 (2003). [CrossRef]

]. Losses in general can be linked to finite divergences [28

28. I. V. Ciapurin, L. B. Glebov, and V. I. Smirnov, “Modeling of phase volume diffractive gratings, part 1: transmitting sinusoidal uniform gratings,” Opt. Eng. 45(1), 015802 (2006). [CrossRef]

] and grating vector non-uniformities across the large aperture. However, the results ranging between 93% and 96% are comparable to the values achieved by others [22

22. O. Andrusyak, V. Smirnov, G. Venus, and L. Glebov, “Beam combining of lasers with high spectral density using volume Bragg gratings,” Opt. Commun. 282(13), 2560–2563 (2009). [CrossRef]

24

24. O. Andrusyak, V. Smirnov, G. Venus, V. Rotar, and L. Glebov, “Spectral Combining and Coherent Coupling of Lasers by Volume Bragg Gratings,” IEEE Sel. Top. Quantum Electron. 15(2), 344–353 (2009). [CrossRef]

]. The temperature tuning of both lasers for optimum performance results in a wavelength separation of 0.5 nm (Fig. 4b).

The beam propagation parameters (M2 1/e 2) of the combined beam at maximum current are 1.8 (fast axis) and 3.3 (slow axis). The corresponding beam caustics for both axes of the combined beam are shown in Fig. 5
Fig. 5 Beam caustics of the combined beam at 300 mA to the ridge section and 14 A to the tapered section.
. The resulting values are comparable to the laser with lowest beam quality. A similar behavior is observed at low currents. While measuring the beam widths along the beam waist of the focused beam, the beam profiles of the combined beam are recorded simultaneously. Figure 6
Fig. 6 Beam profiles of the combined beam at 300 mA to the ridge section and 14 A to the tapered section. (a) Near field profile in the fast axis. (b) Near field profile in the slow axis. (c) Far field profile in the fast axis (d) Far field profile in the slow axis.
shows the corresponding near field and far field profiles measured at injection currents of 14 A. In the near field the combined beam shows beam widths of 97.0 µm (fast axis) and 88.7 µm (slow axis). The divergence angles are measured to be 1.4° (fast axis) and 2.9° (slow axis). At 6 A the beam widths of the near field are more or less comparable. The divergence angles are reduced, improving the beam propagation parameters to 1.6 (fast axis) and 2.4 (slow axis) at that current value.

5. Conclusion

Spectral beam combining of two DBR-tapered diode lasers is demonstrated with a combined output power of 16 W. Both DBR-tapered diode lasers emit around 1063 nm and are spectrally separated by 0.5 nm. Using a reflecting volume Bragg grating we obtain combining efficiencies of 93% - 96%. As expected, the beam propagation parameters are not affected by this technique. Therefore the values of 1.8 (fast axis) and 3.3 (slow axis) match the tapered diode laser with lowest beam quality.

Power scaling using multiple high-power DBR-tapered diode lasers should be possible in the future. This could lead to efficient, cost-effective and compact systems offering single, near diffraction limited output beams with multiple tens of Watts.

References and links

1.

O. Svelto, S. Longhi, G. Della Valle, S. Kück, G. Huber, M. Pollnau, H. Hillmer, S. Hansmann, R. Engelbrecht, H. Brand, J. Kaiser, A. B. Peterson, R. Malz, S. Steinberg, G. Marowsky, U. Brinkmann, D. Lot, A. Borsutzky, H. Wächter, M. W. Sigrist, E. Saldin, E. Schneidmiller, M. Yurkov, K. Midorikawa, J. Hein, R. Sauerbrey, and J. Helmcke, “Lasers and Coherent Light Sources,” in Springer Handbook of Lasers and Optics, F. Träger, ed. (Springer Science and Business Media, New York, 2007).

2.

U. Brauch, P. Loosen, and H. Opower, “High-Power Diode Lasers for Direct Applications,” in High Power Diode Lasers: Fundamentals, Technology, Applications, R. Diehl, ed. (Springer, Berlin, 2000).

3.

T. Y. Fan, “Laser beam combining for high-power, high-radiance sources,” IEEE J. Sel. Top. Quantum Electron. 11(3), 567–577 (2005). [CrossRef]

4.

T. H. Loftus, A. M. Thomas, M. Norsen, J. Minelly, P. Jones, E. Honea, S. A. Shakir, S. Hendow, W. Culver, B. Nelson, and M. Fitelson, “Four-Channel, High Power, Passively Phase Locked Fiber Array,” in Advanced Solid-State Photonics, OSA Technical Digest Series (CD) (Optical Society of America, 2008), paper WA4.

5.

G. Goodno, C. Asman, J. Anderegg, S. Brosnan, E. Cheung, D. Hammons, H. Injeyan, H. Komine, W. Long, M. McClellan, S. McNaught, S. Redmond, R. Simpson, J. Sollee, M. Weber, S. Weiss, and M. Wickham, “Brightness-Scaling Potential of Actively Phase-Locked Solid-State Laser Arrays,” IEEE J. Sel. Top. Quantum Electron. 13(3), 460–472 (2007). [CrossRef]

6.

A. Shirakawa, T. Saitou, T. Sekiguchi, and K. Ueda, “Coherent addition of fiber lasers by use of a fiber coupler,” Opt. Express 10(21), 1167–1172 (2002). [PubMed]

7.

A. A. Ishaaya, N. Davidson, and A. A. Friesem, “Passive laser beam combining with intracavity interferometric combiners,” IEEE Sel. Top. Quantum Electron. 15(2), 301–311 (2009). [CrossRef]

8.

A. Knigge, G. Erbert, J. Jonsson, W. Pittroff, R. Staske, B. Sumpf, M. Weyers, and G. Trankle, “Passively cooled 940 nm laser bars with 73% wall-plug efficiency at 70 W and 25°C,” Electron. Lett. 41(5), 250–251 (2005). [CrossRef]

9.

M. Kanskar, T. Earles, T. Goodnough, E. Stiers, D. Botez, and L. Mawst, “73% CW power conversion efficiency at 50 W from 970 nm diode laser bars,” Electron. Lett. 41(5), 245–247 (2005). [CrossRef]

10.

B. Liu, Y. Liu, and Y. Braiman, “Coherent beam combining of high power broad-area laser diode array with a closed-V-shape external Talbot cavity,” Opt. Express 18(7), 7361–7368 (2010). [CrossRef] [PubMed]

11.

B. Thestrup, M. Chi, B. Sass, and P. M. Petersen, “High brightness laser source based on polarization coupling of two diode lasers with asymmetric feedback,” Appl. Phys. Lett. 82(5), 680–682 (2003). [CrossRef]

12.

T. H. Loftus, A. Liu, P. R. Hoffman, A. M. Thomas, M. Norsen, R. Royse, and E. Honea, “522 W average power, spectrally beam-combined fiber laser with near-diffraction-limited beam quality,” Opt. Lett. 32(4), 349–351 (2007). [CrossRef] [PubMed]

13.

C. Wirth, O. Schmidt, I. Tsybin, T. Schreiber, T. Peschel, F. Brückner, T. Clausnitzer, J. Limpert, R. Eberhardt, A. Tünnermann, M. Gowin, E. ten Have, K. Ludewigt, and M. Jung, “2 kW incoherent beam combining of four narrow-linewidth photonic crystal fiber amplifiers,” Opt. Express 17(3), 1178–1183 (2009). [CrossRef] [PubMed]

14.

W. Schulz and R. Poprawe, “Manufacturing with novel high-power diode lasers,” IEEE J. Sel. Top. Quantum Electron. 6(4), 696–705 (2000). [CrossRef]

15.

D. Wu, Q. Zhang, G. Ma, Y. Guo, and D. Guo, “Laser bending of brittle materials,” Opt. Lasers Eng. 48(4), 405–410 (2010). [CrossRef]

16.

C. Roychoudhuri, “Desk-top manufacturing using diode lasers,” Proc. SPIE 3274, 162–170 (1998). [CrossRef]

17.

H. Shabir, B. Lal, and M. Rafat, “A comparative study of the properties of terbium aluminum garnet powder sintered in air, vacuum and by laser irradiation,” Ceram. Int. 36(1), 365–369 (2010). [CrossRef]

18.

M. Behringer, “High-Power Diode Laser Technology and Characteristics,” in High Power Diode Lasers: Technology and Applications, F. Bachmann, P. Loosen, and R. Poprawe, ed. (Springer, Berlin, 2007)

19.

V. Daneu, A. Sanchez, T. Y. Fan, H. K. Choi, G. W. Turner, and C. C. Cook, “Spectral beam combining of a broad-stripe diode laser array in an external cavity,” Opt. Lett. 25(6), 405–407 (2000). [CrossRef]

20.

B. Chann, R. K. Huang, L. J. Missaggia, C. T. Harris, Z. L. Liau, A. K. Goyal, J. P. Donnelly, T. Y. Fan, A. Sanchez-Rubio, and G. W. Turner, “Near-diffraction-limited diode laser arrays by wavelength beam combining,” Opt. Lett. 30(16), 2104–2106 (2005). [CrossRef] [PubMed]

21.

D. Vijayakumar, O. B. Jensen, R. Ostendorf, T. Westphalen, and B. Thestrup, “Spectral beam combining of a 980 nm tapered diode laser bar,” Opt. Express 18(2), 893–898 (2010). [CrossRef] [PubMed]

22.

O. Andrusyak, V. Smirnov, G. Venus, and L. Glebov, “Beam combining of lasers with high spectral density using volume Bragg gratings,” Opt. Commun. 282(13), 2560–2563 (2009). [CrossRef]

23.

A. Sevian, O. Andrusyak, I. Ciapurin, V. Smirnov, G. Venus, and L. Glebov, “Efficient power scaling of laser radiation by spectral beam combining,” Opt. Lett. 33(4), 384–386 (2008). [CrossRef] [PubMed]

24.

O. Andrusyak, V. Smirnov, G. Venus, V. Rotar, and L. Glebov, “Spectral Combining and Coherent Coupling of Lasers by Volume Bragg Gratings,” IEEE Sel. Top. Quantum Electron. 15(2), 344–353 (2009). [CrossRef]

25.

B. Sumpf, K.-H. Hasler, P. Adamiec, F. Bugge, F. Dittmar, J. Fricke, H. Wenzel, M. Zorn, G. Erbert, and G. Tränkle, “High-Brightness Quantum Well Tapered Lasers,” IEEE Sel. Top. Quantum Electron. 15(3), 1009–1020 (2009). [CrossRef]

26.

K.-H. Hasler, B. Sumpf, P. Adamiec, F. Bugge, J. Fricke, P. Ressel, H. Wenzel, G. Erbert, and G. Tränkle, “5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality,” IEEE Photon. Technol. Lett. 20(19), 1648–1650 (2008). [CrossRef]

27.

I. V. Ciapurin, L. B. Glebov, L. N. Glebova, V. I. Smirnov, and E. V. Rotari, “Incoherent combining of 100-W Yb-fiber laser beams by PTR Bragg grating,” Proc. SPIE 4974, 209–219 (2003). [CrossRef]

28.

I. V. Ciapurin, L. B. Glebov, and V. I. Smirnov, “Modeling of phase volume diffractive gratings, part 1: transmitting sinusoidal uniform gratings,” Opt. Eng. 45(1), 015802 (2006). [CrossRef]

OCIS Codes
(140.2020) Lasers and laser optics : Diode lasers
(140.3298) Lasers and laser optics : Laser beam combining

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: November 9, 2010
Revised Manuscript: December 22, 2010
Manuscript Accepted: January 3, 2011
Published: January 11, 2011

Citation
André Müller, Deepak Vijayakumar, Ole Bjarlin Jensen, Karl-Heinz Hasler, Bernd Sumpf, Götz Erbert, Peter E. Andersen, and Paul Michael Petersen, "16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers," Opt. Express 19, 1228-1235 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-2-1228


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References

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  11. B. Thestrup, M. Chi, B. Sass, and P. M. Petersen, “High brightness laser source based on polarization coupling of two diode lasers with asymmetric feedback,” Appl. Phys. Lett. 82(5), 680–682 (2003). [CrossRef]
  12. T. H. Loftus, A. Liu, P. R. Hoffman, A. M. Thomas, M. Norsen, R. Royse, and E. Honea, “522 W average power, spectrally beam-combined fiber laser with near-diffraction-limited beam quality,” Opt. Lett. 32(4), 349–351 (2007). [CrossRef] [PubMed]
  13. C. Wirth, O. Schmidt, I. Tsybin, T. Schreiber, T. Peschel, F. Brückner, T. Clausnitzer, J. Limpert, R. Eberhardt, A. Tünnermann, M. Gowin, E. ten Have, K. Ludewigt, and M. Jung, “2 kW incoherent beam combining of four narrow-linewidth photonic crystal fiber amplifiers,” Opt. Express 17(3), 1178–1183 (2009). [CrossRef] [PubMed]
  14. W. Schulz and R. Poprawe, “Manufacturing with novel high-power diode lasers,” IEEE J. Sel. Top. Quantum Electron. 6(4), 696–705 (2000). [CrossRef]
  15. D. Wu, Q. Zhang, G. Ma, Y. Guo, and D. Guo, “Laser bending of brittle materials,” Opt. Lasers Eng. 48(4), 405–410 (2010). [CrossRef]
  16. C. Roychoudhuri, “Desk-top manufacturing using diode lasers,” Proc. SPIE 3274, 162–170 (1998). [CrossRef]
  17. H. Shabir, B. Lal, and M. Rafat, “A comparative study of the properties of terbium aluminum garnet powder sintered in air, vacuum and by laser irradiation,” Ceram. Int. 36(1), 365–369 (2010). [CrossRef]
  18. M. Behringer, “High-Power Diode Laser Technology and Characteristics,” in High Power Diode Lasers: Technology and Applications, F. Bachmann, P. Loosen, and R. Poprawe, ed., (Springer, Berlin, 2007)
  19. V. Daneu, A. Sanchez, T. Y. Fan, H. K. Choi, G. W. Turner, and C. C. Cook, “Spectral beam combining of a broad-stripe diode laser array in an external cavity,” Opt. Lett. 25(6), 405–407 (2000). [CrossRef]
  20. B. Chann, R. K. Huang, L. J. Missaggia, C. T. Harris, Z. L. Liau, A. K. Goyal, J. P. Donnelly, T. Y. Fan, A. Sanchez-Rubio, and G. W. Turner, “Near-diffraction-limited diode laser arrays by wavelength beam combining,” Opt. Lett. 30(16), 2104–2106 (2005). [CrossRef] [PubMed]
  21. D. Vijayakumar, O. B. Jensen, R. Ostendorf, T. Westphalen, and B. Thestrup, “Spectral beam combining of a 980 nm tapered diode laser bar,” Opt. Express 18(2), 893–898 (2010). [CrossRef] [PubMed]
  22. O. Andrusyak, V. Smirnov, G. Venus, and L. Glebov, “Beam combining of lasers with high spectral density using volume Bragg gratings,” Opt. Commun. 282(13), 2560–2563 (2009). [CrossRef]
  23. A. Sevian, O. Andrusyak, I. Ciapurin, V. Smirnov, G. Venus, and L. Glebov, “Efficient power scaling of laser radiation by spectral beam combining,” Opt. Lett. 33(4), 384–386 (2008). [CrossRef] [PubMed]
  24. O. Andrusyak, V. Smirnov, G. Venus, V. Rotar, and L. Glebov, “Spectral Combining and Coherent Coupling of Lasers by Volume Bragg Gratings,” IEEE Sel. Top. Quantum Electron. 15(2), 344–353 (2009). [CrossRef]
  25. B. Sumpf, K.-H. Hasler, P. Adamiec, F. Bugge, F. Dittmar, J. Fricke, H. Wenzel, M. Zorn, G. Erbert, and G. Tränkle, “High-Brightness Quantum Well Tapered Lasers,” IEEE Sel. Top. Quantum Electron. 15(3), 1009–1020 (2009). [CrossRef]
  26. K.-H. Hasler, B. Sumpf, P. Adamiec, F. Bugge, J. Fricke, P. Ressel, H. Wenzel, G. Erbert, and G. Tränkle, “5-W DBR Tapered Lasers Emitting at 1060 nm With a Narrow Spectral Linewidth and a Nearly Diffraction-Limited Beam Quality,” IEEE Photon. Technol. Lett. 20(19), 1648–1650 (2008). [CrossRef]
  27. I. V. Ciapurin, L. B. Glebov, L. N. Glebova, V. I. Smirnov, and E. V. Rotari, “Incoherent combining of 100-W Yb-fiber laser beams by PTR Bragg grating,” Proc. SPIE 4974, 209–219 (2003). [CrossRef]
  28. I. V. Ciapurin, L. B. Glebov, and V. I. Smirnov, “Modeling of phase volume diffractive gratings, part 1: transmitting sinusoidal uniform gratings,” Opt. Eng. 45(1), 015802 (2006). [CrossRef]

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