## High power wavelength linearly swept mode locked fiber laser for OCT imaging

Optics Express, Vol. 16, Issue 18, pp. 14095-14105 (2008)

http://dx.doi.org/10.1364/OE.16.014095

Acrobat PDF (488 KB)

### Abstract

We report a long coherence length, high power, and wide tuning range wavelength linearly swept fiber mode-locked laser based on polygon scanning filters. An output power of 52.6 mW with 112 nm wavelength tuning range at 62.6 kHz sweeping rate has been achieved. The coherence length is long enough to enable imaging over 8.1 mm depth when the sensitivity decreases by 8.7 dB (1/*e*^{2}). The Fourier components are still distinguishable when the ranging depth exceeds 15 mm, which corresponds to 30 mm optical path difference in air. The parameters that are critical to OCT imaging quality such as polygon filter linewidth, the laser coherence length, output power, axial resolution and the Fourier sensitivity have been investigated theoretically and experimentally. Since the wavelength is swept linearly with time, an analytical approach has been developed for transforming the interference signal from equidistant spacing in wavelength to equidistant spacing in frequency. Axial resolution of 7.9 µm in air has been achieved experimentally that approaches the theoretical limit.

© 2008 Optical Society of America

## 1. Introduction

1. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical coherence tomography,” Science **254**, 1178–1181 (1991). [CrossRef] [PubMed]

3. B. E. Bouma, G. J. Tearney, I. P. Bilinsky, B. Golubovic, and J. G. Fujimoto, “Self-phase-modulated Kerr-lens mode-locked Cr:forsterite laser source for optical coherence tomography,” Opt. Lett. **21**, 1839–1841 (1996). [CrossRef] [PubMed]

4. X. Li, T. H. Ko, and J. G. Fujimoto, “Intraluminal fiber-optic Doppler imaging catheter for structural and functional optical coherence tomography,” Opt. Lett. **26**, 1906–1908 (2001). [CrossRef]

5. S. H. Yun, G. J. Tearney, J. F. deBoer, N. Iftimia, and B. E. Bouma “High-speed optical frequency-domain imaging,” Opt. Express: **11**, 2953–2963 (2003). [CrossRef]

11. R. Huber, M. Wojtkowski, K. Taira, J. G. Fujimoto, and K. Hsu, “Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles,” Opt. Express **13**, 3513–3528 (2005). [CrossRef] [PubMed]

12. R. Huber, M. Wojtkowski, and J. G. Fujimoto, “Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography,” Opt. Express **14**, 3225–3237 (2006). [CrossRef] [PubMed]

10. W. Y. Oh, S. H. Yun, G. J. Tearney, and B. E. Bouma, “115 kHz tuning repetition rate ultrahigh-speed wavelength-swept semiconductor laser,” Opt. Lett. **30**, 3159–3161 (2005). [CrossRef] [PubMed]

13. S. H. Yun, C. Boudoux, G. J. Tearney , and B. E. Bouma, “High-speed wavelength-swept semiconductor laser with a polygon-scanner-based wavelength filter,” Opt. Lett. **28**, 1981–1983 (2003). [CrossRef] [PubMed]

14. R. Huber, D. C. Adler, and J. G. Fujimoto, “The publication were buffering is introduced to increase sweep rate is: Title: Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s,” Opt. Lett. **31**, 2975–2977 (2006). [CrossRef] [PubMed]

11. R. Huber, M. Wojtkowski, K. Taira, J. G. Fujimoto, and K. Hsu, “Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles,” Opt. Express **13**, 3513–3528 (2005). [CrossRef] [PubMed]

12. R. Huber, M. Wojtkowski, and J. G. Fujimoto, “Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography,” Opt. Express **14**, 3225–3237 (2006). [CrossRef] [PubMed]

12. R. Huber, M. Wojtkowski, and J. G. Fujimoto, “Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography,” Opt. Express **14**, 3225–3237 (2006). [CrossRef] [PubMed]

15. D. C. Adler, R. Huber, and J. G. Fujimoto, “Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers,” Opt. Lett. **32**, 626 (2007). [CrossRef] [PubMed]

## 2. Theory for OCT signal processing

### 2.1 Coherence length of Laser sources

*z*is the optical path difference, Δ

*λ*

_{fwhm}and

*f*(

*δλ*) are the instantaneous laser linewidth and its spectral profile,

*λ*is the light wavelength in vacuum,

*δλ*=

*λ*-

*λ*

_{0}is the wavelength detuning,

*λ*

_{0}is the filter center wavelength and

*ϕ*is the initial phase. For a tophat spectral profile

*f*(

*δλ*)=1 when |

*δλ*|≤Δ

*λ*

_{fwhm}/2 and

*f*(

*δλ*)=0 when |

*δλ*|>Δ

*λ*

_{fwhm}/2, Eq. (1) reduces to

*ϕ*have been neglected for simplicity,

*λ*

_{FSR}is the spectral tuning range and

*f*

_{sweep}is the sweep frequency. Since Δ

*λ*

_{fwhm}≪

*λ*, the sinc function is a slow varying term that is superimposed on the first fast term that produces the interference fringes. When

*z*=

*d*

_{0}, the interference fringes disappear and the corresponding path difference 2

*d*

_{0}=

*λ*

^{2}/Δ

*λ*

_{fwhm}is called the coherence length (

*d*

_{0}is called coherence depth). For a filter with a Gaussian spectral profile exp⌊-4ln(2)(

*δλ*/Δ

*λ*

_{fwhm})

^{2}⌋, this coherence depth is usually expressed as

*d*

_{0}[17

17. B. Bouma, G. J. Tearney, S. A. Boppart, M. R. Hee, M. E. Brezinski, and J. G. Fujimoto, “High-resolution optical coherence tomographic imaging using a mode-locked Ti:Al_{2}O_{3} laser source,” Opt. Lett. **20**, 1486–1488 (1995). [CrossRef] [PubMed]

18. M. Wojtkowski, V. J. Srinivasan, T. H. Ko, J. G. Fujimoto, A. Kowalczyk, and J. S. Duker, “Ultrahigh-resolution, high-speed, Fourier domain optical coherence tomography and methods for dispersion compensation,” Opt. Express, **12**, 2404–2422 (2004). [CrossRef]

### 2.2 k-space

11. R. Huber, M. Wojtkowski, K. Taira, J. G. Fujimoto, and K. Hsu, “Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles,” Opt. Express **13**, 3513–3528 (2005). [CrossRef] [PubMed]

**14**, 3225–3237 (2006). [CrossRef] [PubMed]

*t*

^{′}to replace the time variable t in Eq. (2) as

*f*=(

*z*/Δ

*z*

_{0})

*f*

_{sweep}is the frequency of the k-spaced signal, Δ

*z*

_{0}=

*λ*

^{2}

_{0}/2(2Δ

*λ*

_{FSR}), the constant phase has been ignored for simplicity. To obtain an equal frequency spaced signal

*i*=1,2,…

*N*requires only to re-map the signal with a new time stream of

*N*is the total number of samples of the signal, and

*i*

^{’}that can be solved by Eq. (3) is usually not an integer and an interpretation operation may be required. Since this is an analytical calculation and interpretation, the processing time is negligible compared to the time required for Fourier transformation. We will demonstrate that this analytical technique can provide a signal with an accurate equidistant spacing in frequency, and therefore, the resolution of the point spread function (PSF) is in good agreement with theoretical calculation.

### 2.3 Fourier detectable range, sensitivity, and axial resolution

*k*=0,1,2,… For a total acquisition time of

*T*

_{sweep}=1/

*f*

_{sweep}, the Fourier frequency is given by

*F*

_{k}=

*kf*

_{sweep}, equal to the signal frequency

*f*in Eq. (4). The depth is then obtained as

*z*=

*k*Δ

*z*

_{0}. Clearly, Δz0 represents the axial step, corresponding to the axial resolution.

*z*

_{max}) corresponds to the maximum detectable Fourier frequency that can be obtained when these two opposite Fourier frequencies superimpose at

*k*=

*N*/2 as

*z*

_{max}=

*N*Δ

*z*

_{0}/2. This maximum detectable range corresponds to the signal sampling rate of two samples every interference period, which is generally not sufficient to describe a periodical signal accurately, thus resulting in a low signal-to-noise ratio. For

*N*=1024, this Fourier detectable range is about 3.97 mm.

*t*as

*a*(

*z*,

*t*)=

*a*

_{0}(

*z*), (the top-hat evolution profile), the peak of Fourier sensitivity (or strength) is thus obtained as |

*X*(

*k*)|

^{2}max≈

*a*

^{2}

_{0}(

*z*)(

*N*/2)

^{2}. This results in peak sensitivities of 94 and 54 dB, respectively for

*N*=10

^{5}and 1024 samples when the signal amplitude

*a*

_{0}(

*z*)=1.0. By measuring this peak sensitivity as a function of the depth

*z*, the profile of

*a*

_{0}(

*z*) or the coherence length of the light source can be determined.

*u*=4ln2/

*π*,

*z*

_{F}is depth variable converted from the Fourier frequency

*F*, and

*q*is the parameter to describe the width of the Gaussian shaping profile. The sinc function is the Fourier transform of signal with a top-hat profile. Note that when

*q*→∞, Eq. (5) reduces to top-hat profile as sinc

^{2}[(

*z*

_{F}-

*z*)/Δ

*z*

_{0}]. The axial resolution is thus the axial step Δ

*z*

_{0}, given by Eq. (4). Simulation shows the side lobes of the sinc profile can be suppressed by the operation of the convolution at the expense of degrading the depth resolution, which is in good agreement with our experimental results.

## 3. Experiments and results

*f*

_{1}=75mm and

*f*

_{2}=40 mm were used to construct the confocal telescope system. An 830 line/mm diffraction grating (Newport 53004BK) was the dispersion component. A 72-facet polygon mirror (Lincoln Laser, SA34) was used to sweep the wavelength. By inserting a 3.3 km fiber delay line into a 7 m long ring laser cavity, we could alternate between mode-locked and short cavity lasers operation, respectively, as shown in Fig. 1(a).

*λ*

_{FSR}) that is determined by the number of the polygon facets (

*N*), focal lengths of the two lenses and the grating period (Λ) as Δ

*λ*

_{FSR}=(4

*π*/

*N*)Λ

*f*

_{2}/

*f*

_{1}[10

10. W. Y. Oh, S. H. Yun, G. J. Tearney, and B. E. Bouma, “115 kHz tuning repetition rate ultrahigh-speed wavelength-swept semiconductor laser,” Opt. Lett. **30**, 3159–3161 (2005). [CrossRef] [PubMed]

*L*is the fiber physical length and

*n*

_{eff}is the effective refractive index of the fiber core,

*c*is the light velocity in vacuum, and

*M*is the order of the harmonic. In order to reduce the fiber loss and potential dispersion effect, the fundamental mode (

*M*=1) was used in our experiments. Obviously, when the sweeping frequency is tuned around the center mode-locked frequency, the returned photons will mismatch the exact filter wavelength. When this mismatched wavelength is out of the filter wavelength range, no returned photons can pass the filter and the laser is not lasing. The relationship between the sweeping frequency and the filter linewidth is then obtained as

*f*

_{0}is the center mode-locked frequency,

*δf*is FWHM of the laser output power profile with respect to the detuning of frequency. For

*n*

_{eff}=1.45,

*L*=3.3 km, Eq. (7) gives the mode-locked frequency as

*f*

_{0}=62.70 kHz, which is agreement with our experimental result of 62.57 kHz. Detuning the sweeping frequency from

*f*

_{0}results in the decrease of the output power, as shown in Fig. 2. For

*δf*=0.11 kHz and Δ

*λ*

_{FSR}=112 nm, Eq. (7) gives the filter linewidth as

*δλ*=0.197 nm, which agrees well with the experimental value of 0.2 nm. The linewidth was measured at the circulator port 3 using an optical spectrum analyzer when the polygon is stationary, where the SOA acted as a wideband light source. Note that the free spectral range is used to represent the wavelength tuning range. This provides a useful way to determine the linewidth of spinning polygon filters. The asymmetry profile as shown in Fig. 2 indicates the wavelength sweeping direction. On average, higher power on the long wavelength side was observed. When the sweeping frequency of the polygon mirror is slightly faster than the center mode-locked frequency

*f*

_{0}, the polygon filter will catch up with the wavelength in advance, and thus sweeping direction from short to long wavelength will result in a slow power decrease on average.

*L*=3.3 km fiber with

*σ*=3.1 ps/nm/km dispersion coefficient at 1300 nm band [18

18. M. Wojtkowski, V. J. Srinivasan, T. H. Ko, J. G. Fujimoto, A. Kowalczyk, and J. S. Duker, “Ultrahigh-resolution, high-speed, Fourier domain optical coherence tomography and methods for dispersion compensation,” Opt. Express, **12**, 2404–2422 (2004). [CrossRef]

*λ*spectral width is expressed as

*dt*=

*σL*Δ

*λ*, 2.05 ps and 1.15 ns, respectively for instantaneous filter linewidth of 0.2 nm and wavelength tuning range of 112 nm, corresponding to the filter wavelength mismatches of 1.4×10

^{-5}nm and 8.0×10

^{-3}nm at a 62 kHz (

*f*) sweeping frequency (Δ

*λ*

_{FSR}

*fdt*). This is about two orders of magnitude lower than the filter linewidth and hence can be neglected. Note that the second order dispersion with coefficient of 0.085ps/km/nm^2 has the same order magnitude effect compared with the first order.

*λ*

_{FSR}) centered at 1320 nm was obtained, which agrees well with the theoretical calculation of 111.7 nm. The full width at half maximum width is approximately 95 nm.

*e*,

*t*) evolution profiles, respectively, the theoretical and experimental PSFs at this depth are shown in Fig. 6(a) and (b). The insert figures in Fig. 6(a) and (b) are used to indicate the signal evolution profiles. The interference frequency in the insert figures is reduced for visual purposes. The FWHM at this depth for top-hat profile is about 7.9 µm, which closes to the 7.8 µm, the theoretical derived limit for a light source with a tuning range of 112.2 nm centered at 1320 nm wavelength. For the Gaussian shaping evolution profile, the signal-to-noise ratio can be improved due to the suppression of the side lobes while the axial resolution degrades to 13.4 µm. The mechanism of this resolution degradation results from the reduced effective tuning range. For a shaping profile of Gaussine(0.5,

*t*), experimental results show the axial resolution is ~10.0 µm. Experimental results are in good agreement with the theoretical calculation.

*e*

^{2}) decrease in sensitivity has been achieved in our experiments. Note that the depth is ~7.3 mm for a 7.5 dB sensitivity decrease. The Fourier components are still distinguishable when the ranging depth exceeds 15 mm.

^{4}, which is large enough to analyse tens of millimeters in ranging depth for a sweeping frequency of 62.6 kHz. When the signal sampling rate reduces to 100MS/s, the samples reduce to ~1600, corresponding to a maximum Fourier measurable range of ~6.2 mm. When the ranging depth closes to this depth, the signalnoise ratio will be degraded dramatically.

## 4. Conclusion

*e*

^{2}decrease in sensitivity have been achieved from a single semiconductor optical gain medium and 3.3 km fiber cavity. The Fourier components are still distinguishable at the reflection depth of 15 mm. For a 7 m long short-cavity, the corresponding power and depth drop to 35 mW and 3.4 mm, respectively when the sweeping frequency is 42.9 kHz. The laser thresholds for mode-locked and short-cavity are ~100 mA and ~250 mA while the slope efficiencies are ~0.134 mW/mA. An analytical expression has been developed for calculating of the polygon filter linewidth from the measurement of the power profile width with respect to the sweeping frequency. The asymmetry of this power profile indicates the wavelength sweeping direction. By taking the merit of linear wavelength tuning, an analytical method has been demonstrated to provide an accurate equidistant k-spaced signal. Axial resolution of 7.9 µm in air, approaching the theoretical limit, has also been achieved.

## References and links

1. | D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, “Optical coherence tomography,” Science |

2. | W. Drexler, U. Morgner, F. X. Kartner, C. Pitris, S. A. Boppart, X. D. Li, E. P. Ippen, and J. G. Fujimoto, “ |

3. | B. E. Bouma, G. J. Tearney, I. P. Bilinsky, B. Golubovic, and J. G. Fujimoto, “Self-phase-modulated Kerr-lens mode-locked Cr:forsterite laser source for optical coherence tomography,” Opt. Lett. |

4. | X. Li, T. H. Ko, and J. G. Fujimoto, “Intraluminal fiber-optic Doppler imaging catheter for structural and functional optical coherence tomography,” Opt. Lett. |

5. | S. H. Yun, G. J. Tearney, J. F. deBoer, N. Iftimia, and B. E. Bouma “High-speed optical frequency-domain imaging,” Opt. Express: |

6. | S. R. Chinn, E. A. Swanson, and J. G. Fujimoto, “Optical coherence tomography using a frequency-tunable optical source,” Opt. Lett. |

7. | S. H. Yun, G. J. Tearney, J. F. deBoer, and B. E. Bouma, “Removing the depth-degeneracy in optical frequency domain imaging with frequency shifting,” Opt. Express |

8. | M. A. Choma, M. V. Sarunic, C. Yang, and J. A. Izatt, “Sensitivity advantage of swept source and Fourier domain optical coherence tomography,” Opt. Express |

9. | R. Huber, M. Wojtkowski, and J. G. Fujimoto, “Three-dimensional and C-mode OCT imaging with a compact, frequency swept laser source at 1300 nm,” Opt. Express |

10. | W. Y. Oh, S. H. Yun, G. J. Tearney, and B. E. Bouma, “115 kHz tuning repetition rate ultrahigh-speed wavelength-swept semiconductor laser,” Opt. Lett. |

11. | R. Huber, M. Wojtkowski, K. Taira, J. G. Fujimoto, and K. Hsu, “Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles,” Opt. Express |

12. | R. Huber, M. Wojtkowski, and J. G. Fujimoto, “Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography,” Opt. Express |

13. | S. H. Yun, C. Boudoux, G. J. Tearney , and B. E. Bouma, “High-speed wavelength-swept semiconductor laser with a polygon-scanner-based wavelength filter,” Opt. Lett. |

14. | R. Huber, D. C. Adler, and J. G. Fujimoto, “The publication were buffering is introduced to increase sweep rate is: Title: Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s,” Opt. Lett. |

15. | D. C. Adler, R. Huber, and J. G. Fujimoto, “Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers,” Opt. Lett. |

16. | R. Huber, D. C. Adler, V. J. Srinivasan, and J. G. Fujimoto, “Fourier domain mode locking at 1050 nm for ultra-high-speed optical coherence tomography of the human retina at 236,000 axial scans per second,” Opt. Lett. |

17. | B. Bouma, G. J. Tearney, S. A. Boppart, M. R. Hee, M. E. Brezinski, and J. G. Fujimoto, “High-resolution optical coherence tomographic imaging using a mode-locked Ti:Al |

18. | M. Wojtkowski, V. J. Srinivasan, T. H. Ko, J. G. Fujimoto, A. Kowalczyk, and J. S. Duker, “Ultrahigh-resolution, high-speed, Fourier domain optical coherence tomography and methods for dispersion compensation,” Opt. Express, |

19. |

**OCIS Codes**

(110.4500) Imaging systems : Optical coherence tomography

(140.3600) Lasers and laser optics : Lasers, tunable

**ToC Category:**

Imaging Systems

**History**

Original Manuscript: May 21, 2008

Revised Manuscript: August 13, 2008

Manuscript Accepted: August 17, 2008

Published: August 26, 2008

**Virtual Issues**

Vol. 3, Iss. 11 *Virtual Journal for Biomedical Optics*

**Citation**

George Y. Liu, Adrian Mariampillai, Beau A. Standish, Nigel R. Munce, Xijia Gu, and I. Alex Vitkin, "High power wavelength linearly swept mode locked fiber laser for OCT imaging," Opt. Express **16**, 14095-14105 (2008)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-18-14095

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### References

- D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, "Optical coherence tomography," Science 254, 1178-1181 (1991). [CrossRef] [PubMed]
- W. Drexler, U. Morgner, F. X. Kartner, C. Pitris, S. A. Boppart, X. D. Li, E. P. Ippen, and J. G. Fujimoto, "In vivo ultrahigh-resolution optical coherence tomography," Opt. Lett. 24, 1221-1223 (1999).
- B. E. Bouma, G. J. Tearney, I. P. Bilinsky, B. Golubovic, and J. G. Fujimoto, "Self-phase-modulated Kerr-lens mode-locked Cr:forsterite laser source for optical coherence tomography," Opt. Lett. 21, 1839-1841 (1996). [CrossRef] [PubMed]
- X. Li, T. H. Ko, and J. G. Fujimoto, "Intraluminal fiber-optic Doppler imaging catheter for structural and functional optical coherence tomography," Opt. Lett. 26, 1906-1908 (2001). [CrossRef]
- S. H. Yun, G. J. Tearney, J. F. deBoer, N. Iftimia and B. E. Bouma "High-speed optical frequency-domain imaging," Opt. Express: 11, 2953-2963 (2003). [CrossRef]
- S. R. Chinn, E. A. Swanson, and J. G. Fujimoto, "Optical coherence tomography using a frequency-tunable optical source," Opt. Lett. 22, 340-342 (1997). [CrossRef] [PubMed]
- S. H. Yun, G. J. Tearney, J. F. deBoer, and B. E. Bouma, "Removing the depth-degeneracy in optical frequency domain imaging with frequency shifting," Opt. Express 12, 4822-4828 (2004). [CrossRef] [PubMed]
- M. A. Choma, M. V. Sarunic, C. Yang, and J. A. Izatt, "Sensitivity advantage of swept source and Fourier domain optical coherence tomography," Opt. Express 11, 2183-2189 (2003). [CrossRef] [PubMed]
- R. Huber, M. Wojtkowski, and J. G. Fujimoto, "Three-dimensional and C-mode OCT imaging with a compact, frequency swept laser source at 1300 nm," Opt. Express 13, 10523-10538 (2005). [CrossRef] [PubMed]
- W. Y. Oh, S. H. Yun, G. J. Tearney, and B. E. Bouma, "115 kHz tuning repetition rate ultrahigh-speed wavelength-swept semiconductor laser," Opt. Lett. 30, 3159-3161 (2005). [CrossRef] [PubMed]
- R. Huber, M. Wojtkowski, K. Taira, J. G. Fujimoto, and K. Hsu, "Amplified, frequency swept lasers for frequency domain reflectometry and OCT imaging: design and scaling principles," Opt. Express 13, 3513-3528 (2005). [CrossRef] [PubMed]
- R. Huber, M. Wojtkowski, J. G. Fujimoto, "Fourier Domain Mode Locking (FDML): A new laser operating regime and applications for optical coherence tomography," Opt. Express 14, 3225-3237 (2006). [CrossRef] [PubMed]
- S. H. Yun, C. Boudoux, G. J. Tearney and B. E. Bouma, "High-speed wavelength-swept semiconductor laser with a polygon-scanner-based wavelength filter," Opt. Lett. 28, 1981-1983 (2003). [CrossRef] [PubMed]
- R. Huber, D. C. Adler, J. G. Fujimoto, "The publication were buffering is introduced to increase sweep rate is: Title: Buffered Fourier domain mode locking: unidirectional swept laser sources for optical coherence tomography imaging at 370,000 lines/s," Opt. Lett. 31, 2975-2977 (2006). [CrossRef] [PubMed]
- D. C. Adler, R. Huber, and J. G. Fujimoto, "Phase-sensitive optical coherence tomography at up to 370,000 lines per second using buffered Fourier domain mode-locked lasers," Opt. Lett. 32, 626 (2007). [CrossRef] [PubMed]
- R. Huber, D. C. Adler, V. J. Srinivasan, and J. G. Fujimoto, "Fourier domain mode locking at 1050 nm for ultra-high-speed optical coherence tomography of the human retina at 236,000 axial scans per second," Opt. Lett. 32, 2049-2051 (2007). [CrossRef] [PubMed]
- B. Bouma, G. J. Tearney, S. A. Boppart, M. R. Hee, M. E. Brezinski, and J. G. Fujimoto, "High-resolution optical coherence tomographic imaging using a mode-locked Ti:Al2O3 laser source," Opt. Lett. 20, 1486-1488 (1995). [CrossRef] [PubMed]
- M. Wojtkowski, V. J. Srinivasan, T. H. Ko, J. G. Fujimoto, A. Kowalczyk, and J. S. Duker, "Ultrahigh-resolution, high-speed, Fourier domain optical coherence tomography and methods for dispersion compensation," Opt. Express 12, 2404-2422 (2004). [CrossRef]
- http://www.pofc.com/english/Telecom%20Fiber.htm

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