SLOWING LIGHT USING
4.4 EXPERIMENTAL RESULTS AND DISCUSSION
Fig. 4.3 and Fig. 4.4 show the relative amplitude response and the RF phase change response for various wavelength detuning values. Increasing wavelength detuning shifts the amplitude and phase response to higher RF frequency. RF phase change of nearly 2π can be achieved if the modulation frequency is high enough. It is observed that the dip in the amplitude response also accompanies a RF phase change about 200 degree.
Fig. 4.5 shows the optical spectrum at wavelength detuning of 0.1122nm, and the modulation frequency is 14 GHz, corresponding to a RF phase change of 200 degree.
Modulation frequency is 19 GHz, corresponding to RF phase change of 250 degree for the wavelength detuning.
According to the optical spectra, the upper sideband of the signal is amplified and is 10 dB larger than the lower sideband. Moreover, the slave VCSEL is mot in the stable locking regime, provided the slave laser and the master laser do not operate in the same lasing wavelength. Thus, the upper sideband is amplified because of the complex nonlinear dynamic phenomena and the slave VCSEL acts as a regenerative amplifier.
Compared with the VCSEL amplifier below its lasing threshold in chapter 3, although slow-light based on the injection-locking mechanism can have more optical delay, the amplified sideband may induce signal distortion (appendix) , which is not wanted for optical delay line use. Besides, the complexity of nonlinear dynamics largely increases difficulty in designing slow-light devices.
-30 -20 -10 0 10 20
0.074 nm 0.089 nm 0.099 nm 0.113 nm 0.129 nm 0.136 nm 0.144 nm
Relative Response (dB)
Figure 4.3. Measured relative amplitude response of an injection-locked VCSEL for various wavelength detuning values. The input signal power before entering the VCSEL is -14 dBm throughout the study.
5 10 15 20
-500 -400 -300 -200 -100 0 100
0.074 nm 0.089 nm 0.099 nm 0.113 nm 0.129 nm 0.136 nm 0.144 nm
RF Phase Change (degree)
Frequency (GHz)
Figure 4.4. Measured corresponding RF phase change response of an injection-locked VCSEL for various wavelength detuning values.
1276.9 1277.0 1277.1 1277.2 1277.3 -80
-70 -60 -50 -40 -30 -20
-10 Modulation frequency
=14 GHz Slave VCSEL
Carrier wave of the input signal Upper
sideband
Lower sideband
Optical Power (dBm)
Wavelength (nm)
Figure 4.5. Optical spectrum at wavelength detuning of 0.1122nm. Modulation frequency is 14 GHz, corresponding to RF phase change of 200 degree for the wavelength detuning.
1276.9 1277.0 1277.1 1277.2 1277.3 -80
-70 -60 -50 -40 -30 -20
-10 Slave VCSEL Upper sideband
Lower sideband Carrier wave of the input signal
Modulation frequency
=19 GHz
Optical Power (dBm)
frequency is 14 GHz, corresponding to RF phase change of 250 degree for the wavelength detuning.
4.5 SUMMARY
The chapter concludes the study of achieving RF delay or optical delay using injection-locking of the VCSEL. The amplitude response and phase response shift with increased wavelength detuning. The optical spectrum is studied, which reflects the slave laser does not operate in the stable locking regime.
Chapter 5
CONCLUSION
In this thesis, slowing light using vertical-cavity surface-emitting lasers (VCSELs) is explained and simulated using VCSEL amplifier model. Simulated results and result are qualitatively in a good agreement. With the aid of the filter phase analysis, the simulation explains that group delay increases with increased modal gain and decreases with increased modulation frequency. Besides, the simulations predict the VCSEL’s capability of delaying single-tone sinusoidal signal of 1 to 5 GHz.
Moreover, understanding the basic principle behind allow us to design optimized optical delay line using VCSEL amplifier scheme. Further, the principle should not be suitable for use in VCSELs only. It can be generalized to the general kinds of semiconductor lasers.
RF delay or optical delay using injection-locking of VCSELs is studied in the thesis.
Optical spectra show that the VCSEL is not in the stable-locking range. The VCSEL acts as a regenerative amplifier, making one of the signal side band much larger than
In summary, this thesis explores the novel use of semiconductor lasers as optical delay line and gives at least qualitative explanation. The functionality, compactness, and practicality nature will make semiconductor lasers promising candidates for the novel generation of optical delay lines in high-speed optical network in the future.
BIBLIOGRAPHY
[1] A. Yariv and P. Yeh, Photonics, 7th ed., Oxford University Press, 2007.
[2] A. Yariv, Quantum Electronics, 3d ed., Wiley, 1989.
[3] S. L. Chuang, Physics of Optoelectronic Devices, Wiley-Interscience, 1995.
[4] Zh. I. Alferov, “Double Heterostructure Lasers: Early Days and Future Perspectives,” IEEE J. Sel. Top. Quantum Electron. 6, 832-840, 2000.
[5] N. N. Ledentsov, M. Grundmann, F. Heinrichsdorff, D. Bimberg, V. M. Ustinov, A. E.
Zhukov, M. V. Maximov, Zh. I. Alferov, and J. A. Lott, “Quantum-Dot Heterostructure Lasers,” IEEE J. Sel. Top. Quantum Electron. 6, 439-451, 2000.
[6] M. Sugawara, N. Hatori, M. Ishida, H. Ebe, Y Arakawa, T. Akiyama, K. Otsubo, T. Yamamoto, and Y. Nakata, “Recent progress in self-assembled quantum-dot optical devices for optical telecommunication: temperature-insensitive 10Gbs−1 directly modulated lasers and 40Gbs−1 signal-regenerative amplifiers,” J. Phys. D:
Appl. Phys. 38, 2126–2134, 2005.
[7] D. Bimberg, “Quantum dots for lasers, amplifiers and computing,” J. Phys. D:
Appl. Phys. 38, 2055–2058, 2005.
[8] C. J. Chang-Hasnain and S. L. Chuang, “Slow and Fast Light in Semiconductor Quantum-Well and Quantum-Dot Devices,” J. Lightwave Technol. 24,
[10] S. Minin, M. Fisher, and S. L. Chuang, “Current-controlled group delay using a semiconductor Fabry–Pérot amplifier,” Appl. Phys. Lett., vol. 84, no. 17, pp.
3238–3240, 2004.
[11] X. Zhao, P. Palinginis, B. Pesala, C. J. Chang-Hasnain, and P. Hemmer, “Tunable ultraslow light in vertical-cavity surface emitting laser amplifier,” Opt. Express, vol. 13, no. 20, p. 7899, 2005.
[12] P. C. Peng, C. T. Lin, H. C. Kuo, W. K. Tsai, J. N. Liu, S. Chi, S. C. Wang, G. Lin, H. P. Yang, K. F. Lin, and J. Y. Chi, “Tunable slow light device using quantum dot semiconductor laser”, Optics Express, Vol. 14, Issue 26, pp. 12880-12886 , 2006.
[13] E. O. Kane, “The k.p method,” Chapter 3, in R. K. Willardson and A. C. Beer, Eds., Semiconductors and Semimetals, Vol.1, Academic, 1966.
[14] J. Singh, Electronic and Optoelectronic Properties of Semiconductor Structures, Cambridge University Press, 2003.
[15] L. A. Coldren and S. W. Corzine, Diode Lasers and Photonic Integrated Circuits, Wiley-Interscience, 1995.
[16] V. M. Ustinov, A. E. Zhukov, A. Y. Egorov, and N. A. Maleev, Quantum Dot Lasers, Oxford University Press, 2003.
[17] J. Singh, Semiconductor Optoelectronics – Physics and Technology, McGraw-Hill, Inc., 1995.
[18] Z. Mi and P. Bhattacharya, "Analysis of the Linewidth-Enhancement Factor of Long-Wavelength Tunnel-Injection Quantum-Dot Lasers," J. Quantum Electron.
43, 363-369, 2007.
[19] Joe T. Mok and Benjamin J. Eggleton, “Expect more delays”, Nature, Vol 433, 24 Feb 2005
[20] G. Lenz, B. J. Eggleton, C. K. Madsen, and R. E. Slusher, “Optical delay lines
2001.
[21] C. J. Chang-Hasnain, P.-C. Ku, J. Kim, and S. L. Chuang, “Variable optical buffer using slow light in semiconductor nanostructures,” Proc. IEEE, vol. 9, no.
11, p. 1884, Nov. 2003.
[22] L. V. Hau, S. E. Harris, Z. Dutton, and C. H. Behroozi, “Light speed reduction to 17 meters per second in an ultra cold atomic gas”, Nature, Vol. 397, Feb 1999.
[23] J. E. Field, K. H. Hahn and S. E. Harris, “Observation of electromagnetically induced transparency in collisionally broadened lead vapor,” Phys. Rev. Lett. 67 3062, 1991.
[24] M. S. Bigelow, N. N. Lepeshkin, and R. W. Boyd, “Observation of ultraslow light propagation in a ruby crystal at room temperature,” Phys. Rev. Lett., vol. 90, no. 11, p. 113 903, Mar. 2003.
[25] P.-C. Ku, F. Sedgwick, C. J. Chang-Hasnain, P. Palinginis, T. Li, H.Wang, S.-W.
Chang, and S. L. Chuang, “Slow light in semiconductor quantum wells,” Opt.
Lett., vol. 29, no. 19, pp. 2291–2293, Oct. 2004.
[26] P. Palinginis, F. Sedgwick, S. Crankshaw, M. Moewe, and C. J. Chang-Hasnain,
“Room temperature slow light in a quantum-well waveguide via coherent population oscillation,” Opt. Express, vol. 13, no. 24, pp. 9909–9915, Nov. 2005.
[27] H. Su and S. L. Chuang, “Variable optical delay using population oscillation and four-wave-mixing in semiconductor optical amplifiers,” Opt. Express, vol. 14, no.
11, pp. 4800–4807, May 2006.
[28] H. Su and S. L. Chuang, “Room temperature slow light with semiconductor quantum-dot devices,” Opt. Lett., vol. 31, no. 2, pp. 271–273, Jan. 2006.
[29] H. Su and S. L. Chuang, “Room temperature slow and fast light in quantum dot
[30] J. K. S. Poon, L. Zhu, G. Y. DeRose, and A. Yariv, “Transmission and group delay of microring coupled-resonator optical waveguides”, Opt. Lett. 31, 456-458, 2006.
[31] M. R. Fisher, S. Minin, and S. L. Chuang, “Tunable optical group delay in an active waveguide semiconductor resonator,” IEEE J. Sel. Topics Quantum Electron., vol. 11, no. 1, pp. 197–203, Jan./Feb. 2005.
[32] M. R. Fisher, and S. L. Chuang, “Variable Group Delay and Pulse Reshaping of High Bandwidth Optical Signals”, IEEE J. Quantum Electron. 41, 885-891, 2005.
[33] H. Altuga and J. Vuckovic, “Two-dimensional coupled photonic crystal resonator arrays”, Appl. Phys. Lett., Vol.84, 161-163, 2004.
[34] J. K. S. Poon, J. Scheuer, Y Xu, and A. Yariv, “Designing coupled-resonator optical waveguide delay lines”, J. Opt. Soc. Am. B 21, 1665-1673, 2004.
[35] Y. H. Chang, P. C. Peng, W. K. Tsai, G. Lin, F. I. Lai, R. S. Hsiao, H. P. Yang, H. C. Yu, K. F. Lin, J. Y. Chi, S. C. Wang, and H. C. Kuo, “Single-mode monolithic quantum-dot VCSEL in 1.3 um with sidemode suppression ratio over 30 dB,” IEEE Photon. Tech. Lett. 18, 847-849, 2006.
[36] N. Laurand, S. Calvez and M. D. Dawson, and A. E. Kelly, "Slow-light in a vertical-cavity semiconductor optical amplifier," Opt. Express 14, 6858-6863, 2006.
[37] X. Zhao, Y. Zhou, C. J. Chang-Hasnain, W. Hofmann, and M. C. Amann, “Novel modulated-master injection-locked 1.55-µm VCSELS,” Opt. Express 14, 10500-10507, 2006.
[38] M. R. Fisher and S. L. Chuang, “Asymmetric nonlinear transmission spectra of Fabry-Perot laser amplifiers,” IEEE Photon. Tech. Lett. 18, 409-411, 2006.
[39] A. Murakami, K. Kawashima, and K. Atsuki, ”Cavity Resonance Shift and Bandwidth Enhancement in Semiconductor Lasers With Strong Light Injection,”
IEEE J. Quantum Electron. QE-39, pp. 1196-1204, 2003.
[40] F. Mogensen, H. Olesen, and G. Jacobsen, "Locking Conditions and Stability Properties for a Semiconductor Laser with External Light Injection," IEEE J.
Quantum Electron. QE-21, 784-793, 1985.
[41] R. Lang, "Injection Locking Properties of a Semiconductor Laser," IEEE J.
Quantum Electron. QE-18, 976-983, 1982.
[42] C. H. Henry, N. A. Olsson, and N. K. Dutta, "Locking Range and Stability of Injection Locked 1.54 pm InGaAsP Semiconductor Lasers," IEEE J. Quantum Electron. QE-21, 1152-1156, 1985.
[43] X. Zhao, Y. Zhou, C. J. Chang-Hasnain, W. Hofmann, and M. C. Amann, "Slow and fast light using master-modulate injection-locked VCSELs," Conf. on Lasers and Electro-Optics/Quantum Electronics and Laser Science (CLEO/QELS, Long Beach, CA, USA) (Piscataway, NJ: IEEE), 2006.