OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 10 — May. 11, 2009
  • pp: 7750–7755
« Show journal navigation

Single-wavelength fiber laser with 250 mW output power at 1.57 µm

Gautam Das and Zachary J. Chaboyer  »View Author Affiliations


Optics Express, Vol. 17, Issue 10, pp. 7750-7755 (2009)
http://dx.doi.org/10.1364/OE.17.007750


View Full Text Article

Acrobat PDF (243 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

A novel single-wavelength fiber ring laser with 250 mW output power is reported. A double-clad polarization-maintaining erbium-ytterbium co-doped fiber was used in a unidirectional ring cavity as an active medium to eliminate spatial hole-burning effect in the cavity. The output of the laser was single-longitudinal mode. A fiber Fabry-Perot filter was used in the cavity to increase the longitudinal-mode spacing which eliminated the mode hopping. The maximum output power produced by the laser without mode hopping was 250 mW. The optical signal to noise ratio (OSNR) of the laser was more than 40 dB.

© 2009 OSA

1. Introduction

A high power single-wavelength, single-longitudinal-mode fiber ring laser operating at room temperature is attractive because of its applications in optical communication, interferometers, and sensing. Several methods were reported to produce a high power single frequency fiber laser. One of the techniques adopted was Master-Oscillator-Power-Amplifier (MOPA) configuration [1

1. K. H. Yla-Jarkko and A. B. Grudinin, “Performance limitations of high-power DFB fiber lasers,” IEEE Photon. Technol. Lett. 15(2), 191–193 (2003). [CrossRef]

3

3. S. U. Alam, R. Wixey, L. Hickey, K. H. Yla-Jarkko, and M. N. Zervas, “High power, single-mode, single-frequency DFB fibre laser at 1550 nm in MOPA configuration," in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference and Photonic Applications Systems Technologies, Technical Digest (CD) (Optical Society of America, 2004), paper CMK7.

]. Although lasers produced high output power, application of the systems is limited due to complexity in design, lower noise performance compared to a stand-alone high power laser, and the stability. A unidirectional ring cavity configuration using erbium-doped fiber as a gain medium is suitable for developing a fiber laser, because it eliminates spatial hole-burning effect in the gain medium. However, the practical difficulty in developing a single-wavelength, single-longitudinal-mode, high power fiber laser arises due to the need for a longer gain medium (longer cavity) and this leads to instability of the laser wavelength due to smaller longitudinal-mode spacing. A few articles have been reported on high power single-frequency fiber laser in the ring cavity configuration with more than 700 mW output power [4

4. X. X. Yang, L. Zhan, Q. S. Shen, and Y. X. Xia, “High-power single-longitudinal-mode fiber laser with a ring Fabry-Perot resonator and a saturable absorber,” IEEE Photon. Technol. Lett. 20(11), 879–881 (2008). [CrossRef]

,5

5. A. Polynkin, P. Polynkin, M. Mansuripur, and N. Peyghambarian, “Single-frequency fiber ring laser with 1W output power at 1.5 mu m,” Opt. Express 13(8), 3179–3184 (2005). [CrossRef] [PubMed]

]. In Ref. 4

4. X. X. Yang, L. Zhan, Q. S. Shen, and Y. X. Xia, “High-power single-longitudinal-mode fiber laser with a ring Fabry-Perot resonator and a saturable absorber,” IEEE Photon. Technol. Lett. 20(11), 879–881 (2008). [CrossRef]

, a high power erbium-doped fiber amplifier was used inside the ring cavity to generate high output power from the laser. To eliminate mode hopping, an unpumped erbium-doped fiber was used inside the cavity as a saturable absorber [6

6. Y. Cheng, J. T. Kringlebotn, W. H. Loh, R. I. Laming, and D. N. Payne, “Stable single-frequency traveling-wave fiber loop laser with integral saturable-absorber-based tracking narrow-band-filter,” Opt. Lett. 20(8), 875–877 (1995). [CrossRef] [PubMed]

]. In Ref. 5

5. A. Polynkin, P. Polynkin, M. Mansuripur, and N. Peyghambarian, “Single-frequency fiber ring laser with 1W output power at 1.5 mu m,” Opt. Express 13(8), 3179–3184 (2005). [CrossRef] [PubMed]

, an erbium-ytterbium co-doped phosphate glass fiber was used as an active medium in a unidirectional ring cavity. The active fiber was cladding pumped by four diode lasers using a contact side-pumping scheme. A tunable sub-cavity filter was used to eliminate mode hopping [7

7. S. V. Chernikov, J. R. Taylor, and R. Kashyap, “Coupled-cavity erbium fiber lasers incorporating fiber grating reflectors,” Opt. Lett. 18(23), 2023–2025 (1993). [CrossRef] [PubMed]

]. The filter was formed by two gratings, where the fiber separating two gratings was mounted on a PZT stretcher, and adjusted the cavity length by applying a DC voltage to the PZT. Further, a polarizing fiber (PZ- fiber) was used to ensure single-polarization mode operation of the laser. The use of a high power EDFA, saturable absorber, the contact side-pumping scheme, and PZT fiber stretcher to control the FP cavity length dynamically make systems complex and expensive.

In this article, a novel and simple medium power single-wavelength, single-longitudinal-mode fiber laser in a ring cavity configuration is demonstrated. A single-mode, polarization-maintaining, double-clad, erbium-ytterbium co-doped fiber (DC-EYDF, CorActive, Canada) of length 1 m was used as an active medium. The advantages of using a DC-EYDF are; (i) the large optical absorption cross-section and broader absorption band (910 nm −980 nm) of the ytterbium ions increase the efficiency of the pump power absorption; (ii) the double-clad structure of the fiber gives large pump wavelength guiding region and thus an inexpensive multimode laser diode can be used as a pump source; (iii) the polarization-maintaining property of the gain fiber provides better control of the polarization states of the light inside the cavity, otherwise, it can cause the instability of the laser output. To increase the longitudinal-mode spacing a Fabry-Perot filter (etalon) with large free spectral range (FSR), formed by two fused fiber couplers was used inside the cavity. The wider longitudinal-mode spacing eliminated mode hopping of the laser wavelength.

The novelty of the reported laser design are: i) use of conventional optical components; ii) no dynamic control was required to eliminate mode hopping; iii) a multimode diode laser together with a multimode fused fiber coupler (Gooch & Housego, UK) was used to pump the active fiber.

2. Results and discussion

The fiber ring laser is shown in Fig. 1
Fig. 1 Experimental fiber laser. OI: Polarization independent optical isolator.
. A three port polarization independent optical circulator (CIR) guaranteed the unidirectional propagation of light waves, and the fiber polarization controller (PC) controlled the polarization state of the light inside the cavity. A fiber Bragg grating (FBG of band width, center wavelength, and reflectivity, 0.27 nm, 1570.26 nm, and 56%, respectively) selected the lasing wavelength. It is to be noted that the above grating was chosen after a series of experiments with gratings having different parameters. A Fabry-Perot filter (FP Filter) based on two 2 × 2 single-mode fused fiber couplers (split ratio 99:1) increased the effective FSR of the cavity. A DC-EYDF of length 1 m as the gain medium with core/clad dimensions, cladding ytterbium absorption at 915 nm, and numerical aperture of 9.8/134 μm, 2.9 dB/m, and 0.47, respectively. A multimode pigtailed laser diode at 976 nm (CPM-II, Alfalight, USA) was used to pump the active fiber through a multimode fused fiber coupler, which acts as a 976/1550 nm wavelength division multiplexing coupler. Output of the laser was measured simultaneously with an optical spectrum analyzer (OSA) of resolution 1.25 GHz, a scanning Fabry-Perot spectrum analyzer (SFPSA) of resolution 6.7 MHz, and a power meter. In order to protect the OSA from damage due to the high output power of the laser, 99% of the output power was fed into the power meter.

Figure 2
Fig. 2 Fabry-Perot filter formed by fused fiber couplers, where K1 and K2 are intensity coupling ratios. Ein, Ereflec. and Etrans are incident, reflected and transmitted electric fields, respectively. LFP = L1 + L2 is the cavity length.
shows the Fabry-Perot (FP) filter formed by two fused fiber couplers [8

8. A. Gloag, N. Langford, K. McCallion, and W. Johnstone, “Continuously tunable single-frequency erbium ring fiber laser,” J. Opt. Soc. Am. B 13(5), 921–925 (1996). [CrossRef]

]. The expressions for the transmitted and reflected fields are given by:

EtransEin=(1K1)(1K2)exp(JβLFP)1+K1K2exp(JβLFP)EreflecEin=J(K1+K2exp(JβLFP))1+K1K2exp(JβLFP)(EtransEin)2+(EreflecEin)2=1}.
(1)

The expressions for transmitted and reflected intensities of the resonator obtained from Eq. (1) are given by

ItransIin=(1K1)(1K2)(1+K1K2)24K1K2sin2(βLFP2)IreflecIin=1(1K1)(1K2)(1+K1K2)24K1K2sin2(βLFP2)}.
(2)

To obtain the resonance phase condition for the filter, we considered the reflected intensity to be zero. Thus, from Eq. (1),

J(K1+K2cos(βLFP))K2sin(βLFP)=0.
(3)

When the real part of Eq. (3) is zero, sin(βLFP)=0 or cos(βLFP)=±1. Since K1 and K2 are both positive, only cos(βLFP)=1 can make the imaginary part of Eq. (3) zero, when K1 = K2. The resonance phase condition is then,βLFP=(2m+1)π, where β is the propagation constant, LFP is the filter cavity length and m is an integer. The separation between two transmission peaks which corresponds to the free spectral range (FSR) of the Fabry-Perot filter is given by:
FSRFP=ΔυFP=cnLFP,
(4)
where c is the speed of light in free space and n is the refractive index ( = 1.46). Further, the expression for the transmitted field, resonance phase condition, and free spectral range for the ring cavity (Fig. 1, without the filter) are given by
EtransRingEin=RFBG+exp(α0Leffective+JβLeffective)1+RFBGexp(α0Leffective+JβLeffective)βLeffective=(2m+1)πFSRcavity=Δυcavity=cnLeffective},
(5)
where Leffective (>LFP) is the effective length of the ring cavity, RFBG is the reflectivity of the Bragg grating, and α0is the loss per meter of the fiber. In the experiment, the effective length (Leffective) of the ring cavity and the length (LFP) of the Fabry-Perot filter were ≈4 m and ≈0.4 m, respectively and the corresponding free spectral ranges (From Eq. (5) and Eq. (4)) were FSRcavity ≈52 MHz, FSRFP ≈514 MHz.

It is evident from Figs. 3(a)
Fig. 3 Theoretical output of the (a) ring cavity (obtained from Eq. (5)) for RFBG = 56% and Leffcetive = 4.0 m. (b) FP filter (Eq. (2)) for K1 = K2 = 0.99 and LFP = 0.4 m.
and 3(b) that the presence of the Fabry-Perot filter inside the cavity provided the Vernier effect [9

9. P. Urquhart, “Compound optical-fiber-based resonators,” J. Opt. Soc. Am. A 5(6), 803–812 (1988). [CrossRef]

], i.e. some of the spectral orders of the ring cavity were suppressed, giving wider separations between transmission peaks. In other words, the output of the ring cavity was modulated by the Fabry-Perot filter. Thus, the separation between the two longitudinal-mode of the cavity changed to ~514 MHz. The theoretical resonance linewidth (FWHM) of the ring cavity and the FP filter were ~13 MHz and ~2 MHz, respectively. The optimum cavity lengths determined by simulation were verified experimentally. The longitudinal mode corresponding to the lasing mode satisfied the resonance conditions for the ring cavity and the FP cavity simultaneously (i.e. the transmission peak of the FP filter exactly matched with one of the transmission peaks of the ring cavity. It is to be noted that the accuracy of the FP cavity length should be within ± 0.02 m). Therefore, fluctuations of the ambient conditions did not destroy the stability of the laser.

Figure 5
Fig. 5 Input-Output characteristics of the laser at 1570.27 nm. Length of the active fiber 1 m.
shows the output of the laser at 1570.27 nm vs. input pump power at 976 nm (The nonlinear behavior of the output could be due to the variation of pump wavelength with input pump current). The threshold pump power of the laser was 345 mW and a slope efficiency of ~7% was achieved. The maximum cavity loss was at the fusion splices between the DC-EYDF and the single-mode fiber. The slope efficiency can be increased by improving the quality of the fusion splices. The maximum output power of the laser was 250 mW due to the limited power handling capacity of the circulator (500 mW). The laser showed the tendency to oscillate in multimode beyond 250 mW output power. The threshold pump power for multimode oscillation was ~4 W. We could eliminate the extra mode from oscillation by adjusting the polarization controller plates. Figure 6
Fig. 6 Output of the laser oscillated in multimode, prior to adjusting the polarization controller plates.
shows the output of the laser prior to the adjustment of the polarization controller. In Fig. 6, the small peak corresponds to the second longitudinal-mode of the laser cavity (~514 MHz apart). The polarization-maintaining property of the active fiber helped to control the polarization state of the wave inside the cavity. It may be possible to produce a linearly polarized output by using polarization-dependent optical components.

The application of an unpumped erbium-doped fiber as a saturable absorber is a well established technique to reduce mode hopping form environmental fluctuations such as temperature variation. The above experiment was repeated with an unpumped erbium-doped fiber as a saturable absorber instead of the FP filter inside the cavity. Though the laser was free from mode hopping, the output power of the laser was low (<100 mW for the same input pump power as the laser reported in this article) due to the presence of the saturable absorber which produced high insertion loss. When the saturable absorber and FP filter were removed the laser produced high output power but suffered from severe mode hopping. The presence of a FP filter eliminated the mode hopping by increasing the longitudinal-mode spacing and keeping the high output power.

The 3-dB linewidth (FWHM = Full width at half maximum) of the lasing wavelength was ≈12 MHz, measured using a scanning Fabry-Perot spectrum analyzer (FSR = 2GHz) of resolution 6.7 MHz and Nuview software, developed by EXFO. The laser linewidth was very large compared to the theoretical value based on Schawlow-Townes formula [10

10. A. L. Schawlow and C. H. Townes, “Infrared and optical masers,” Phys. Rev. 112, 1940–1949 (1958). [CrossRef]

]. Recent investigation shows that the wider linewidth in the erbium-ytterbium co-doped fiber laser is due to the temperature fluctuations induced by the pump intensity noise inside the core of the fiber [11

11. N. Y. Voo, P. Horak, M. Ibsen, and W. H. Loh, “Anomalous linewidth behavior in short-cavity single-frequency fiber laser,” IEEE Photon. Technol. Lett. 17(3), 546–548 (2005). [CrossRef]

,12

12. P. Horak, N. Y. Voo, M. Ibsen, and W. H. Loh, “Pump-noise-induced linewidth contributions in distributed feedback fiber lasers,” IEEE Photon. Technol. Lett. 18(9), 998–1000 (2006). [CrossRef]

]. We believe this might be the cause of broader linewidth of our laser.

3. Conclusions

A medium power single-wavelength single-mode fiber laser is reported. We achieved single-longitudinal mode oscillation by using an all fiber Fabry-Perot filter in the cavity. The laser output was modulated by the output of the filter. A polarization-maintaining, erbium-ytterbium co-doped fiber was used as the gain medium to increase pump power absorption efficiency. The high pump power increased the temperature of the core and this lead to fluctuation of polarization. The polarization-maintaining property of the active fiber provided better polarization control of the wave inside the cavity and increased the stability of the laser wavelength. The maximum output power of the laser was 250 mW.

Acknowledgments

The research is supported financially by the Natural Sciences and Engineering Research Council of Canada.

References and links

1.

K. H. Yla-Jarkko and A. B. Grudinin, “Performance limitations of high-power DFB fiber lasers,” IEEE Photon. Technol. Lett. 15(2), 191–193 (2003). [CrossRef]

2.

C. Alegria, Y. Jeong, C. Codemard, J. K. Sahu, J. A. Alvarez-Chavez, L. Fu, M. Ibsen, and J. Nilsson, “83-W single-frequency narrow-linewidth MOPA using large-core erbium-ytterbium co-doped fiber,” IEEE Photon. Technol. Lett. 16(8), 1825–1827 (2004). [CrossRef]

3.

S. U. Alam, R. Wixey, L. Hickey, K. H. Yla-Jarkko, and M. N. Zervas, “High power, single-mode, single-frequency DFB fibre laser at 1550 nm in MOPA configuration," in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference and Photonic Applications Systems Technologies, Technical Digest (CD) (Optical Society of America, 2004), paper CMK7.

4.

X. X. Yang, L. Zhan, Q. S. Shen, and Y. X. Xia, “High-power single-longitudinal-mode fiber laser with a ring Fabry-Perot resonator and a saturable absorber,” IEEE Photon. Technol. Lett. 20(11), 879–881 (2008). [CrossRef]

5.

A. Polynkin, P. Polynkin, M. Mansuripur, and N. Peyghambarian, “Single-frequency fiber ring laser with 1W output power at 1.5 mu m,” Opt. Express 13(8), 3179–3184 (2005). [CrossRef] [PubMed]

6.

Y. Cheng, J. T. Kringlebotn, W. H. Loh, R. I. Laming, and D. N. Payne, “Stable single-frequency traveling-wave fiber loop laser with integral saturable-absorber-based tracking narrow-band-filter,” Opt. Lett. 20(8), 875–877 (1995). [CrossRef] [PubMed]

7.

S. V. Chernikov, J. R. Taylor, and R. Kashyap, “Coupled-cavity erbium fiber lasers incorporating fiber grating reflectors,” Opt. Lett. 18(23), 2023–2025 (1993). [CrossRef] [PubMed]

8.

A. Gloag, N. Langford, K. McCallion, and W. Johnstone, “Continuously tunable single-frequency erbium ring fiber laser,” J. Opt. Soc. Am. B 13(5), 921–925 (1996). [CrossRef]

9.

P. Urquhart, “Compound optical-fiber-based resonators,” J. Opt. Soc. Am. A 5(6), 803–812 (1988). [CrossRef]

10.

A. L. Schawlow and C. H. Townes, “Infrared and optical masers,” Phys. Rev. 112, 1940–1949 (1958). [CrossRef]

11.

N. Y. Voo, P. Horak, M. Ibsen, and W. H. Loh, “Anomalous linewidth behavior in short-cavity single-frequency fiber laser,” IEEE Photon. Technol. Lett. 17(3), 546–548 (2005). [CrossRef]

12.

P. Horak, N. Y. Voo, M. Ibsen, and W. H. Loh, “Pump-noise-induced linewidth contributions in distributed feedback fiber lasers,” IEEE Photon. Technol. Lett. 18(9), 998–1000 (2006). [CrossRef]

OCIS Codes
(060.2420) Fiber optics and optical communications : Fibers, polarization-maintaining
(140.3500) Lasers and laser optics : Lasers, erbium
(140.3560) Lasers and laser optics : Lasers, ring
(140.3570) Lasers and laser optics : Lasers, single-mode
(060.3735) Fiber optics and optical communications : Fiber Bragg gratings

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: February 9, 2009
Revised Manuscript: March 29, 2009
Manuscript Accepted: April 13, 2009
Published: April 27, 2009

Citation
Gautam Das and Zachary J. Chaboyer, "Single-wavelength fiber laser with 250 mW output power at 1.57 µm," Opt. Express 17, 7750-7755 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-10-7750


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. K. H. Yla-Jarkko and A. B. Grudinin, “Performance limitations of high-power DFB fiber lasers,” IEEE Photon. Technol. Lett. 15(2), 191–193 (2003). [CrossRef]
  2. C. Alegria, Y. Jeong, C. Codemard, J. K. Sahu, J. A. Alvarez-Chavez, L. Fu, M. Ibsen, and J. Nilsson, “83-W Single-Frequency Narrow-Linewidth MOPA Using Large-Core Erbium-Ytterbium Co-Doped Fiber,” IEEE Photon. Technol. Lett. 16(8), 1825–1827 (2004). [CrossRef]
  3. S. U. Alam, R. Wixey, L. Hickey, K. H. Yla-Jarkko, and M. N. Zervas, “High power, single-mode, single-frequency DFB fibre laser at 1550 nm in MOPA configuration," in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference and Photonic Applications Systems Technologies, Technical Digest (CD) (Optical Society of America, 2004), paper CMK7.
  4. X. X. Yang, L. Zhan, Q. S. Shen, and Y. X. Xia, “High-power single-longitudinal-mode fiber laser with a ring Fabry-Perot resonator and a saturable absorber,” IEEE Photon. Technol. Lett. 20(11), 879–881 (2008). [CrossRef]
  5. A. Polynkin, P. Polynkin, M. Mansuripur, and N. Peyghambarian, “Single-frequency fiber ring laser with 1W output power at 1.5 mu m,” Opt. Express 13(8), 3179–3184 (2005). [CrossRef] [PubMed]
  6. Y. Cheng, J. T. Kringlebotn, W. H. Loh, R. I. Laming, and D. N. Payne, “Stable Single-Frequency Traveling-Wave Fiber Loop Laser with Integral Saturable-Absorber-Based Tracking Narrow-Band-Filter,” Opt. Lett. 20(8), 875–877 (1995). [CrossRef] [PubMed]
  7. S. V. Chernikov, J. R. Taylor, and R. Kashyap, “Coupled-Cavity Erbium Fiber Lasers Incorporating Fiber Grating Reflectors,” Opt. Lett. 18(23), 2023–2025 (1993). [CrossRef] [PubMed]
  8. A. Gloag, N. Langford, K. McCallion, and W. Johnstone, “Continuously tunable single-frequency erbium ring fiber laser,” J. Opt. Soc. Am. B 13(5), 921–925 (1996). [CrossRef]
  9. P. Urquhart, “Compound Optical-Fiber-Based Resonators,” J. Opt. Soc. Am. A 5(6), 803–812 (1988). [CrossRef]
  10. A. Schawlow, “L and Townes, C. H., “Infrared and Optical Masers,” Phys. Rev. 112, 1940–1949 (1958). [CrossRef]
  11. N. Y. Voo, P. Horak, M. Ibsen, and W. H. Loh, “Anomalous Linewidth behavior in short-cavity single-frequency fiber laser,” IEEE Photon. Technol. Lett. 17(3), 546–548 (2005). [CrossRef]
  12. P. Horak, N. Y. Voo, M. Ibsen, and W. H. Loh, “Pump-noise-induced linewidth contributions in distributed feedback fiber lasers,” IEEE Photon. Technol. Lett. 18(9), 998–1000 (2006). [CrossRef]

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.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited