Abstract

We report on large energy pulse generation in an erbium-doped fiber laser passively mode-locked with atomic layer graphene. Stable mode locked pulses with single pulse energy up to 7.3 nJ and pulse width of 415 fs have been directly generated from the laser. Our results show that atomic layer graphene could be a promising saturable absorber for large energy mode locking.

© 2009 OSA

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. A. Ruehl, V. Kuhn, D. Wandt, and D. Kracht, “Normal dispersion erbium-doped fiber laser with pulse energies above 10 nJ,” Opt. Express 16(5), 3130–3135 (2008).
    [CrossRef] [PubMed]
  2. A. Chong, W. H. Renninger, and F. W. Wise, “All-normal-dispersion femtosecond fiber laser with pulse energies above 20 nJ,” Opt. Lett. 32, 2408–2410 (2007).
    [CrossRef] [PubMed]
  3. Y. S. Set, H. Yaguchi, Y. Tanaka, and M. Jablonski,“Laser Mode Locking Using a Saturable Absorber Incorporating Carbon Nanotubes,” J. Lightwave Technol. 22(1), 51–56 (2004).
    [CrossRef]
  4. K. Kieu and M. Mansuripur, “Femtosecond laser pulse generation with a fiber taper embedded in carbon nanotube/polymer composite,” Opt. Lett. 32(15), 2242–2244 (2007).
    [CrossRef] [PubMed]
  5. Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
    [CrossRef]
  6. S. Yamashita, Y. Inoue, S. Maruyama, Y. Murakami, H. Yaguchi, M. Jablonski, and S. Y. Set, “Saturable absorbers incorporating carbon nanotubes directly synthesized onto substrates and fibers and their application to mode-locked fiber lasers,” Opt. Lett. 29(14), 1581–1583 (2004).
    [CrossRef] [PubMed]
  7. F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
    [CrossRef] [PubMed]
  8. T. R. Schibli, K. Minoshima, H. Kataura, E. Itoga, N. Minami, S. Kazaoui, K. Miyashita, M. Tokumoto, and Y. Sakakibara, “Ultrashort pulse-generation by saturable absorber mirrors based on polymer-embedded carbon nanotubes,” Opt. Express 13(20), 8025–8031 (2005).
    [CrossRef] [PubMed]
  9. Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
    [CrossRef]
  10. K. Kieu and F. W. Wise, “All-fiber normal-dispersion femtosecond laser,” Opt. Express 16(15), 11453–11458 (2008).
    [CrossRef] [PubMed]
  11. Y. W. Song, S. Yamashita, and S. Maruyama, “Single-walled carbon nanotubes for high-energy optical pulse formation,” Appl. Phys. Lett. 92(2), 021115 (2008).
    [CrossRef]
  12. A. H. C. Neto, “Graphene. Phonons behaving badly,” Nat. Mater. 6(3), 176–177 (2007).
    [CrossRef]
  13. Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
    [CrossRef]
  14. K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
    [CrossRef] [PubMed]

2009

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

2008

K. Kieu and F. W. Wise, “All-fiber normal-dispersion femtosecond laser,” Opt. Express 16(15), 11453–11458 (2008).
[CrossRef] [PubMed]

Y. W. Song, S. Yamashita, and S. Maruyama, “Single-walled carbon nanotubes for high-energy optical pulse formation,” Appl. Phys. Lett. 92(2), 021115 (2008).
[CrossRef]

A. Ruehl, V. Kuhn, D. Wandt, and D. Kracht, “Normal dispersion erbium-doped fiber laser with pulse energies above 10 nJ,” Opt. Express 16(5), 3130–3135 (2008).
[CrossRef] [PubMed]

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

2007

K. Kieu and M. Mansuripur, “Femtosecond laser pulse generation with a fiber taper embedded in carbon nanotube/polymer composite,” Opt. Lett. 32(15), 2242–2244 (2007).
[CrossRef] [PubMed]

Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
[CrossRef]

A. Chong, W. H. Renninger, and F. W. Wise, “All-normal-dispersion femtosecond fiber laser with pulse energies above 20 nJ,” Opt. Lett. 32, 2408–2410 (2007).
[CrossRef] [PubMed]

A. H. C. Neto, “Graphene. Phonons behaving badly,” Nat. Mater. 6(3), 176–177 (2007).
[CrossRef]

2005

2004

Ahn, J. H.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Bao, Q. L.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Choi, J. Y.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Chong, W. H.

Ferrari, A. C.

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Hennrich, F.

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

Hong, B. H.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Inoue, Y.

Itoga, E.

Jablonski, M.

Jang, H.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Kataura, H.

Kazaoui, S.

Kieu, K.

Kim, J. M.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Kim, K. S.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Kim, P.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Kracht, D.

Kuhn, V.

Lee, S. Y.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Loh, K. P.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Mansuripur, M.

Maruyama, S.

Milne, W. I.

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Minami, N.

Minoshima, K.

Miyashita, K.

Morimune, K.

Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
[CrossRef]

Murakami, Y.

Neto, A. H. C.

A. H. C. Neto, “Graphene. Phonons behaving badly,” Nat. Mater. 6(3), 176–177 (2007).
[CrossRef]

Ni, Z. H.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Renninger,

Rozhin, A. G.

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Ruehl, A.

Sakakibara, Y.

Scardaci, V.

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Schibli, T. R.

Set, S. Y.

Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
[CrossRef]

S. Yamashita, Y. Inoue, S. Maruyama, Y. Murakami, H. Yaguchi, M. Jablonski, and S. Y. Set, “Saturable absorbers incorporating carbon nanotubes directly synthesized onto substrates and fibers and their application to mode-locked fiber lasers,” Opt. Lett. 29(14), 1581–1583 (2004).
[CrossRef] [PubMed]

Set, Y. S.

Shen, Z. X.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Song, Y. W.

Y. W. Song, S. Yamashita, and S. Maruyama, “Single-walled carbon nanotubes for high-energy optical pulse formation,” Appl. Phys. Lett. 92(2), 021115 (2008).
[CrossRef]

Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
[CrossRef]

Sun, Z.

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Tanaka, Y.

Tang, D. Y.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Tokumoto, M.

Wandt, D.

Wang, F.

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Wang, Y.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

White, I. H.

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

Wise, F. W.

Yaguchi, H.

Yamashita, S.

Y. W. Song, S. Yamashita, and S. Maruyama, “Single-walled carbon nanotubes for high-energy optical pulse formation,” Appl. Phys. Lett. 92(2), 021115 (2008).
[CrossRef]

Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
[CrossRef]

S. Yamashita, Y. Inoue, S. Maruyama, Y. Murakami, H. Yaguchi, M. Jablonski, and S. Y. Set, “Saturable absorbers incorporating carbon nanotubes directly synthesized onto substrates and fibers and their application to mode-locked fiber lasers,” Opt. Lett. 29(14), 1581–1583 (2004).
[CrossRef] [PubMed]

Zhang, H.

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Zhao, Y.

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Adv. Func. Mat

Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh, and D. Y. Tang, “Atomic layer graphene as saturable absorber for ultrafast pulsed lasers,” Adv. Func. Mat .: DOI: (Published online Aug 25 2009).
[CrossRef]

Appl. Phys. Lett.

Y. W. Song, K. Morimune, S. Y. Set, and S. Yamashita, “Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers,” Appl. Phys. Lett. 90(2), 021101 (2007).
[CrossRef]

Y. W. Song, S. Yamashita, and S. Maruyama, “Single-walled carbon nanotubes for high-energy optical pulse formation,” Appl. Phys. Lett. 92(2), 021115 (2008).
[CrossRef]

Z. Sun, A. G. Rozhin, F. Wang, V. Scardaci, W. I. Milne, I. H. White, F. Hennrich, and A. C. Ferrari, “L-band ultrafast fiber laser mode locked by carbon nanotubes,” Appl. Phys. Lett. 93(6), 061114 (2008).
[CrossRef]

J. Lightwave Technol.

Nat. Mater.

A. H. C. Neto, “Graphene. Phonons behaving badly,” Nat. Mater. 6(3), 176–177 (2007).
[CrossRef]

Nat. Nanotechnol.

F. Wang, A. G. Rozhin, V. Scardaci, Z. Sun, F. Hennrich, I. H. White, W. I. Milne, and A. C. Ferrari, “Wideband-tuneable, nanotube mode-locked, fibre laser,” Nat. Nanotechnol. 3(12), 738–742 (2008).
[CrossRef] [PubMed]

Nature

K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, and B. H. Hong, “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature 457(7230), 706–710 (2009).
[CrossRef] [PubMed]

Opt. Express

Opt. Lett.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig. 1
Fig. 1

Schematic of the fiber laser. PC: polarization controller. WDM: wavelength division multiplexer. EDF: erbium doped fiber. SMF: single mode fiber.

Fig. 2
Fig. 2

Characterization of graphene thin film covering on the fiber core. (a) Raman spectra of the graphene film. (b) Raman image around the fiber core plotted by the intensity of the Raman peak of SiO2. The scale bar is 3 µm. (c) Raman images around the fiber core plotted by the intensity of G band of graphene. The scale bar is 3 µm. (d) Normalized power dependent absorption of atomic layer graphene. Insert: the UV-VIS-NIR absorption spectra of graphene.

Fig. 3
Fig. 3

Pulse operation of the fiber laser. (a) Pulse spectra measured. Insert: long-term fluctuation of the FWHM. (b) Autocorrelation traces of the pulses. (c) An oscilloscope trace of the single pulse emission. Insert: pulse train of CW mode-locking in millisecond time scale. (d) The fundamental radio-frequency (RF) spectrum of the laser output. Insert: wideband RF spectrum up to 100 MHz.

Fig. 4
Fig. 4

the single pulse energy in respect to the pump power.

Metrics