OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 9 — Apr. 23, 2012
  • pp: 10095–10099
« Show journal navigation

Chalcogenide optical parametric oscillator

Raja Ahmad and Martin Rochette  »View Author Affiliations


Optics Express, Vol. 20, Issue 9, pp. 10095-10099 (2012)
http://dx.doi.org/10.1364/OE.20.010095


View Full Text Article

Acrobat PDF (985 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We demonstrate the first optical parametric oscillator (OPO) based on chalcogenide glass. The parametric gain medium is an As2Se3 chalcogenide microwire coated with a layer of polymer. The doubly-resonant OPO oscillates simultaneously at a Stokes and an anti Stokes wavelength shift of >50 nm from the pump wavelength that lies at λP = 1,552 nm. The oscillator has a peak power threshold of 21.6 dBm and a conversion efficiency of >19%. This OPO experiment provides an additional application of the chalcogenide microwire technology; and considering the transparency of As2Se3 glass extending far in the mid-infrared (mid-IR) wavelengths, the device holds promise for realizing mid-IR OPOs utilizing existing optical sources in the telecommunications wavelength region.

© 2012 OSA

1. Introduction

Among the common third order nonlinear optical materials, arsenic triselenide (As2Se3) chalcogenide glass boasts one of the highest nonlinear refractive index coefficient in a glass n2 = 2.3 × 10−13 cm2/W [16

16. J. M. Harbold, F. Ö. Ilday, F. W. Wise, J. S. Sanghera, V. Q. Nguyen, L. B. Shaw, and I. D. Aggarwal, “Highly nonlinear As-S-Se glasses for all-optical switching,” Opt. Lett. 27(2), 119–121 (2002). [CrossRef] [PubMed]

], that is up to 1000 × that of silica, 20 × that of Bi2O3, 4 × that of As2S3, and 3 × that of Si [16

16. J. M. Harbold, F. Ö. Ilday, F. W. Wise, J. S. Sanghera, V. Q. Nguyen, L. B. Shaw, and I. D. Aggarwal, “Highly nonlinear As-S-Se glasses for all-optical switching,” Opt. Lett. 27(2), 119–121 (2002). [CrossRef] [PubMed]

18

18. G. W. Rieger, K. S. Virk, and J. F. Young, “Nonlinear propagation of ultrafast 1.5 μm pulses in high-index-contrast silicon-on-insulator waveguides,” Appl. Phys. Lett. 84(6), 900–902 (2004). [CrossRef]

]. Despite the large value of n2 in As2Se3, the material exhibits a large normal material chromatic dispersion in the 1,550 nm wavelength band, where there is an abundance of lasers that could be utilized for OPO pumping. This chromatic dispersion prevents efficient parametric gain close to the pump wavelength, thereby rendering it difficult to realize OPOs from As2Se3 in bulk or in an optical fiber format. One way to overcome this limitation is to use As2Se3 microwires for which the anomalous waveguide dispersion overcomes the normal material dispersion. Such microwires in addition, exhibit large values of waveguide nonlinear coefficient γ ( = n2ωP/cAeff, ωP being the pump angular frequency, c being the speed of light and Aeff being the effective mode area in the microwire) which lowers the required power threshold for nonlinear applications including the realization of OPO. The highest γ value reported in such microwires is more than 5 orders of magnitude larger than that of silica fibers [19

19. C. Baker and M. Rochette, “Highly nonlinear hybrid AsSe-PMMA microtapers,” Opt. Express 18(12), 12391–12398 (2010). [CrossRef] [PubMed]

]. However, to our knowledge, no chalcogenide OPO in any configuration has yet been reported in the literature.

In this paper, we report an OPO based on an As2Se3 microwire coated with poly-methyl meth-acrylate (PMMA) cladding. The PMMA cladding in addition to providing physical strength to the thin microwire [20

20. R. Ahmad and M. Rochette, “Photosensitivity at 1550 nm and Bragg grating inscription in As2Se3 chalcogenide microwires,” Appl. Phys. Lett. 99(6), 061109 (2011). [CrossRef]

], serves to optimize phase-matching conditions towards efficient and broadband parametric gain [21

21. R. Ahmad and M. Rochette, “High efficiency and ultra broadband optical parametric four-wave mixing in chalcogenide-PMMA hybrid microwires,” Opt. Express . 20, 9572–9580 (2012). [PubMed]

]. The OPO oscillates simultaneously at two wavelengths: at a Stokes and anti-Stokes wavelength shifts of + 53 nm and −50 nm respectively from the pump laser. The large nonlinearity, the reduced chromatic dispersion from a PMMA cladding and the long effective length (due to the low absorption loss α < 1 dB/m) of As2Se3 hybrid microwires allows the OPO to oscillate at a low peak pump power threshold of 21.6 dBm (pulse energy = 3.15 pJ) and with a total conversion efficiency of > 19%.

2. Experimental results and discussion

The hybrid As2Se3-PMMA microwire is prepared following the procedure detailed in Ref [19

19. C. Baker and M. Rochette, “Highly nonlinear hybrid AsSe-PMMA microtapers,” Opt. Express 18(12), 12391–12398 (2010). [CrossRef] [PubMed]

,21

21. R. Ahmad and M. Rochette, “High efficiency and ultra broadband optical parametric four-wave mixing in chalcogenide-PMMA hybrid microwires,” Opt. Express . 20, 9572–9580 (2012). [PubMed]

]. The microwire has an As2Se3 core diameter of 1.01 µm and is 10 cm long, with a total insertion loss of 5 dB. This includes a loss of ~0.8 dB due to the Fresnel reflection of 0.4 dB on each end of the microwire, an As2Se3 and PMMA absorption loss of <1 dB, and the remaining loss is attributed to the mode mismatch between the microwire and the single-mode silica fiber at both ends of the microwire. Figure 1
Fig. 1 Experimental setup for the OPO operation. BPF: band-pass filter; Att: optical attenuator; PC: fiber polarization controller; FC: fiber coupler; OSA: optical spectrum analyzer; DUT: device-under test; CIR: optical circulator; FBG: silica fiber bragg grating; ODL: optical (tunable) delay line.
shows the experimental setup for the OPO operation. A mode-locked laser emitting pulses of full-width at half maximum (FWHM) duration of ~450 fs, with a repetition rate of 20 MHz and spectrally centered at around λ = 1,551 nm, is used as the pump laser. The pump is filtered spectrally with a ~0.25 nm bandpass filter (BPF) centered at 1,552 nm to lengthen pulses to a FWHM duration ~22ps [20

20. R. Ahmad and M. Rochette, “Photosensitivity at 1550 nm and Bragg grating inscription in As2Se3 chalcogenide microwires,” Appl. Phys. Lett. 99(6), 061109 (2011). [CrossRef]

]. The resulting pump pulses are then delivered to the microwire via the 10% output port of a 90/10 fiber coupler (FC). This results in the optical parametric amplification on both sides of the pump wavelength in an almost symmetric manner, determined precisely by the dispersion profile of the microwire. In order to realize OPO, the parametric gain obtained is fed-back to the microwire via the second input port of the FC, thus completing the laser cavity. The residual pump pulse is filtered out from the fed-back signal using a fiber Bragg grating resonant at the pump wavelength combined with an optical fiber circulator (CIR). This avoids any unfavourable interference of the incoming pump pulse with the preceding residual one. A fiber-coupled tunable optical delay line (ODL) is introduced for a precise control of the cavity length so that the amplified Stokes and anti-Stokes signals that resonate in the loop cavity are precisely synchronized with the incoming pump pulse. It is noted that the dispersive walk-off effect can be ignored since the walk-off length of ~2.2 m [22

22. G. P. Agrawal, Nonlinear Fiber Optics, 4th ed. (Academic Press, New York, 2007).

], resulting from the wavelength separation between the pump and the Stokes/anti-Stokes signals is considerably longer than the length of the parametric gain medium i.e., the 10 cm long microwire. Finally, afiber polarization controller is inserted in the cavity to align the polarization state of the two amplified signals with that of the incoming pump pulse. The operation of the OPO is observed on an optical spectrum analyzer (OSA) connected to the 90% output port of the fiber coupler.

When the total single-pass parametric gain exceeds the round-trip cavity loss of 8 dB, the OPO oscillates at Stokes and anti-Stokes wavelengths of 1,605 nm and 1,502 nm respectively. This represents the conversion of a C-band pump laser to L-band (Stokes) and S-band (anti-Stokes) OPOs. Figures 2 (a)
Fig. 2 Output spectra of the (a) Stokes and (b) anti-Stokes OPO signals for the increasing values of input peak pump power. (Inset) The pulse energy in the Stokes and the anti-Stokes output signals are plotted against the input pump pulse energies and are included as inset in (a) and (b) respectively.
and 2(b) show the spectra of the output Stokes and anti-Stokes OPO signals with increasing peak pump power. The spectral FWHMs of the two OPO outputs are 0.44 nm and 0.43 nm for the Stokes and the anti-Stokes signals respectively. The Stokes signal carries 3.3 dB more energy than the anti-Stokes one. This can be explained from the additional Raman gain at the Stokes wavelength that almost coincides with the Raman shift wavelength for the As2Se3 microwire [21

21. R. Ahmad and M. Rochette, “High efficiency and ultra broadband optical parametric four-wave mixing in chalcogenide-PMMA hybrid microwires,” Opt. Express . 20, 9572–9580 (2012). [PubMed]

]. Both the Stokes and the anti-Stokes OPO signals have a threshold peak pump power of ~21.6 dBm, corresponding to pulse energy of 3.15 pJ. The slope efficiency of the Stokes OPO exceeds 13%, with the Stokes output pulses carrying >0.3 pJ of energy. The slope efficiency of the anti-Stokes OPO is >6% corresponding to a pulse energy ~0.15 pJ, providing a total internal conversion efficiency of >19%. This represents high conversion efficiency OPO considering its compactness and the low-power operation.

Figure 3
Fig. 3 Output of the OPO as observed on an OSA for various delay values on the oscillating Stokes and anti-Stokes signals. The calculated parametric gain spectrum under the experimental conditions is also included.
shows the output spectra of the OPO as recorded on the OSA. The spectra show the simultaneous oscillation of the doubly-resonant OPO at the Stokes and anti-Stokes wavelengths. After setting up the OPO, we study the effect of adding a delay or advance on the oscillating Stokes and anti-Stokes signals which compromises their precise synchronization with the pump pulse. The OPO continues to operate for a wide temporal detuning of approximately ± 5 ps beyond which there is no output signal. This temporaldetuning allows OPO Stokes and anti-Stokes wavelengths tuning by up to 8 nm. The wavelength tuning results from a natural minimization of the group velocity mismatch between the pump wavelength and the Stokes/anti-Stokes oscillating wavelengths. In order to compare the experimental results with theory, the single-pass parametric gain in the microwire of the same dimensions as used in the experiment is calculated for a 24.1 dBm peak pump power. The calculated parametric gain profile is included in the Fig. 3. It is noted that the oscillating wavelengths precisely match the wavelengths where the parametric gain is maximum in agreement with theory.

3. Conclusion

In conclusion, we have demonstrated the first optical parametric oscillator in chalcogenide glass. The parametric gain medium is a 1.01 µm thick and 10 cm long As2Se3-PMMA hybrid microwire. The OPO oscillates simultaneously at Stokes and anti-Stokes wavelengths in the L- and the S- telecommunications frequency bands respectively, with the pump lying in the C-band. The OPO has a total internal conversion efficiency of ~19%, with a threshold peak pump power of 21.6 dBm. The wavelength conversion bandwidth of this device can be further extended to the mid-infrared wavelengths region by adjusting the wire diameter to have a net, small value of normal dispersion at the pump wavelength.

Acknowledgments

The authors would like to acknowledge Mr. Chams Baker for the technical support. We also thank Coractive High-Tech inc. for providing the chalcogenide fiber used in the experiments. This work was financially supported by FQRNT (Le Fonds Quebecois de la Recherche sur la Nature et les Technologies) and the Natural Sciences and Engineering Research Council of Canada (NSERC).

References and links

1.

L. E. Myers, R. C. Eckardt, M. M. Fejer, R. L. Byer, W. R. Bosenberg, and J. W. Pierce, “Quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO3,” J. Opt. Soc. Am. B 12(11), 2102–2116 (1995). [CrossRef]

2.

L. E. Myers and W. R. Bosenberg, “Periodically poled lithium niobate and quasi-phase-matched optical parametric oscillators,” IEEE J. Quantum Electron. 33(10), 1663–1672 (1997). [CrossRef]

3.

C. Canalias and V. Pasiskevicius, “Mirrorless optical parametric oscillator,” Nat. Photonics 1(8), 459–462 (2007). [CrossRef]

4.

M. Ghotbi, A. Esteban-Martin, and M. Ebrahim-Zadeh, “BiB3O6 femtosecond optical parametric oscillator,” Opt. Lett. 31(21), 3128–3130 (2006). [CrossRef] [PubMed]

5.

G. K. Samanta, G. R. Fayaz, and M. Ebrahim-Zadeh, “1.59 W, single-frequency, continuous-wave optical parametric oscillator based on MgO:sPPLT,” Opt. Lett. 32(17), 2623–2625 (2007). [CrossRef] [PubMed]

6.

K. O. Hill, B. S. Kawasaki, Y. Fujii, and D. C. Johnson, “Efficient sequence‐frequency generation in a parametric fiber‐optic oscillator,” Appl. Phys. Lett. 36(11), 888 (1980). [CrossRef]

7.

J. E. Sharping, M. Fiorentino, P. Kumar, and R. S. Windeler, “Optical parametric oscillator based on four-wave mixing in microstructure fiber,” Opt. Lett. 27(19), 1675–1677 (2002). [CrossRef] [PubMed]

8.

Y. Deng, Q. Lin, F. Lu, G. P. Agrawal, and W. H. Knox, “Broadly tunable femtosecond parametric oscillator using a photonic crystal fiber,” Opt. Lett. 30(10), 1234–1236 (2005). [CrossRef] [PubMed]

9.

B. Kuyken, X. Liu, R. M. Osgood, R. Baets, G. Roelkens, and W. M. J. Green, “Widely tunable silicon mid-infrared optical parametric oscillator,” in Proc. IEEE Group IV Photonics, 8th Int. Conf., London, U.K., 338–340 (2011).

10.

T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Kerr-nonlinearity optical parametric oscillation in an ultrahigh-Q toroid microcavity,” Phys. Rev. Lett. 93(8), 083904 (2004). [CrossRef] [PubMed]

11.

A. A. Savchenkov, A. B. Matsko, D. Strekalov, M. Mohageg, V. S. Ilchenko, and L. Maleki, “Low threshold optical oscillations in a whispering gallery mode CaF(2) resonator,” Phys. Rev. Lett. 93(24), 243905 (2004). [CrossRef] [PubMed]

12.

P. Del’Haye, A. Schliesser, O. Arcizet, T. Wilken, R. Holzwarth, and T. J. Kippenberg, “Optical frequency comb generation from a monolithic microresonator,” Nature 450(7173), 1214–1217 (2007). [CrossRef] [PubMed]

13.

J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, and M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics 4(1), 37–40 (2010). [CrossRef]

14.

I. H. Agha, Y. Okawachi, M. A. Foster, J. E. Sharping, and A. L. Gaeta, “Four-wave mixing parametric oscillations in dispersion-compensated high-Q optical microspheres,” Phys. Rev. A 76(4), 043837 (2007). [CrossRef]

15.

L. Razzari, D. Duchesne, M. Ferrera, R. Morandotti, S. Chu, B. E. Little, and D. J. Moss, “CMOS-compatible integrated optical hyper-parametric oscillator,” Nat. Photonics 4(1), 41–45 (2010). [CrossRef]

16.

J. M. Harbold, F. Ö. Ilday, F. W. Wise, J. S. Sanghera, V. Q. Nguyen, L. B. Shaw, and I. D. Aggarwal, “Highly nonlinear As-S-Se glasses for all-optical switching,” Opt. Lett. 27(2), 119–121 (2002). [CrossRef] [PubMed]

17.

N. Sugimoto, H. Kanbara, S. Fujiwara, K. Tanaka, Y. Shimizugawa, and K. Hirao, “Third-order optical nonlinearities and their ultrafast response in Bi2O3–B2O3–SiO2 glasses,” J. Opt. Soc. Am. B 16(11), 1904–1908 (1999). [CrossRef]

18.

G. W. Rieger, K. S. Virk, and J. F. Young, “Nonlinear propagation of ultrafast 1.5 μm pulses in high-index-contrast silicon-on-insulator waveguides,” Appl. Phys. Lett. 84(6), 900–902 (2004). [CrossRef]

19.

C. Baker and M. Rochette, “Highly nonlinear hybrid AsSe-PMMA microtapers,” Opt. Express 18(12), 12391–12398 (2010). [CrossRef] [PubMed]

20.

R. Ahmad and M. Rochette, “Photosensitivity at 1550 nm and Bragg grating inscription in As2Se3 chalcogenide microwires,” Appl. Phys. Lett. 99(6), 061109 (2011). [CrossRef]

21.

R. Ahmad and M. Rochette, “High efficiency and ultra broadband optical parametric four-wave mixing in chalcogenide-PMMA hybrid microwires,” Opt. Express . 20, 9572–9580 (2012). [PubMed]

22.

G. P. Agrawal, Nonlinear Fiber Optics, 4th ed. (Academic Press, New York, 2007).

OCIS Codes
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(190.4410) Nonlinear optics : Nonlinear optics, parametric processes
(190.4970) Nonlinear optics : Parametric oscillators and amplifiers

ToC Category:
Nonlinear Optics

History
Original Manuscript: March 14, 2012
Revised Manuscript: April 9, 2012
Manuscript Accepted: April 10, 2012
Published: April 18, 2012

Citation
Raja Ahmad and Martin Rochette, "Chalcogenide optical parametric oscillator," Opt. Express 20, 10095-10099 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-9-10095


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. L. E. Myers, R. C. Eckardt, M. M. Fejer, R. L. Byer, W. R. Bosenberg, and J. W. Pierce, “Quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO3,” J. Opt. Soc. Am. B12(11), 2102–2116 (1995). [CrossRef]
  2. L. E. Myers and W. R. Bosenberg, “Periodically poled lithium niobate and quasi-phase-matched optical parametric oscillators,” IEEE J. Quantum Electron.33(10), 1663–1672 (1997). [CrossRef]
  3. C. Canalias and V. Pasiskevicius, “Mirrorless optical parametric oscillator,” Nat. Photonics1(8), 459–462 (2007). [CrossRef]
  4. M. Ghotbi, A. Esteban-Martin, and M. Ebrahim-Zadeh, “BiB3O6 femtosecond optical parametric oscillator,” Opt. Lett.31(21), 3128–3130 (2006). [CrossRef] [PubMed]
  5. G. K. Samanta, G. R. Fayaz, and M. Ebrahim-Zadeh, “1.59 W, single-frequency, continuous-wave optical parametric oscillator based on MgO:sPPLT,” Opt. Lett.32(17), 2623–2625 (2007). [CrossRef] [PubMed]
  6. K. O. Hill, B. S. Kawasaki, Y. Fujii, and D. C. Johnson, “Efficient sequence‐frequency generation in a parametric fiber‐optic oscillator,” Appl. Phys. Lett.36(11), 888 (1980). [CrossRef]
  7. J. E. Sharping, M. Fiorentino, P. Kumar, and R. S. Windeler, “Optical parametric oscillator based on four-wave mixing in microstructure fiber,” Opt. Lett.27(19), 1675–1677 (2002). [CrossRef] [PubMed]
  8. Y. Deng, Q. Lin, F. Lu, G. P. Agrawal, and W. H. Knox, “Broadly tunable femtosecond parametric oscillator using a photonic crystal fiber,” Opt. Lett.30(10), 1234–1236 (2005). [CrossRef] [PubMed]
  9. B. Kuyken, X. Liu, R. M. Osgood, R. Baets, G. Roelkens, and W. M. J. Green, “Widely tunable silicon mid-infrared optical parametric oscillator,” in Proc. IEEE Group IV Photonics, 8th Int. Conf., London, U.K., 338–340 (2011).
  10. T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, “Kerr-nonlinearity optical parametric oscillation in an ultrahigh-Q toroid microcavity,” Phys. Rev. Lett.93(8), 083904 (2004). [CrossRef] [PubMed]
  11. A. A. Savchenkov, A. B. Matsko, D. Strekalov, M. Mohageg, V. S. Ilchenko, and L. Maleki, “Low threshold optical oscillations in a whispering gallery mode CaF(2) resonator,” Phys. Rev. Lett.93(24), 243905 (2004). [CrossRef] [PubMed]
  12. P. Del’Haye, A. Schliesser, O. Arcizet, T. Wilken, R. Holzwarth, and T. J. Kippenberg, “Optical frequency comb generation from a monolithic microresonator,” Nature450(7173), 1214–1217 (2007). [CrossRef] [PubMed]
  13. J. S. Levy, A. Gondarenko, M. A. Foster, A. C. Turner-Foster, A. L. Gaeta, and M. Lipson, “CMOS-compatible multiple-wavelength oscillator for on-chip optical interconnects,” Nat. Photonics4(1), 37–40 (2010). [CrossRef]
  14. I. H. Agha, Y. Okawachi, M. A. Foster, J. E. Sharping, and A. L. Gaeta, “Four-wave mixing parametric oscillations in dispersion-compensated high-Q optical microspheres,” Phys. Rev. A76(4), 043837 (2007). [CrossRef]
  15. L. Razzari, D. Duchesne, M. Ferrera, R. Morandotti, S. Chu, B. E. Little, and D. J. Moss, “CMOS-compatible integrated optical hyper-parametric oscillator,” Nat. Photonics4(1), 41–45 (2010). [CrossRef]
  16. J. M. Harbold, F. Ö. Ilday, F. W. Wise, J. S. Sanghera, V. Q. Nguyen, L. B. Shaw, and I. D. Aggarwal, “Highly nonlinear As-S-Se glasses for all-optical switching,” Opt. Lett.27(2), 119–121 (2002). [CrossRef] [PubMed]
  17. N. Sugimoto, H. Kanbara, S. Fujiwara, K. Tanaka, Y. Shimizugawa, and K. Hirao, “Third-order optical nonlinearities and their ultrafast response in Bi2O3–B2O3–SiO2 glasses,” J. Opt. Soc. Am. B16(11), 1904–1908 (1999). [CrossRef]
  18. G. W. Rieger, K. S. Virk, and J. F. Young, “Nonlinear propagation of ultrafast 1.5 μm pulses in high-index-contrast silicon-on-insulator waveguides,” Appl. Phys. Lett.84(6), 900–902 (2004). [CrossRef]
  19. C. Baker and M. Rochette, “Highly nonlinear hybrid AsSe-PMMA microtapers,” Opt. Express18(12), 12391–12398 (2010). [CrossRef] [PubMed]
  20. R. Ahmad and M. Rochette, “Photosensitivity at 1550 nm and Bragg grating inscription in As2Se3 chalcogenide microwires,” Appl. Phys. Lett.99(6), 061109 (2011). [CrossRef]
  21. R. Ahmad and M. Rochette, “High efficiency and ultra broadband optical parametric four-wave mixing in chalcogenide-PMMA hybrid microwires,” Opt. Express. 20, 9572–9580 (2012). [PubMed]
  22. G. P. Agrawal, Nonlinear Fiber Optics, 4th ed. (Academic Press, New York, 2007).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1 Fig. 2 Fig. 3
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited