Investigation of elliptically polarized injection locked states in VCSELs subject to orthogonal optical injection Hong Lin,1 Pablo Pérez,2,3 Angel Valle,2,* and Luis Pesquera2 1
Department of Physics and Astronomy, Bates College, Lewiston, Maine 04240, USA Instituto de Física de Cantabria (CSIC-Univ. Cantabria), Avda. Los Castros s/n, E39005 Santander, Spain 3 Dept. de Física Moderna, Fac. Ciencias, Univ. Cantabria, Avda. Los Castros s/n, E39005 Santander, Spain * [email protected] 2
Abstract: We demonstrate experimentally the existence of the elliptically polarized injection-locked (EPIL) state. This state is observed when a single-transverse mode VCSEL is subject to orthogonal optical injection. The spectral feature of the EPIL state is verified and the power of each polarization is measured. The regime of the EPIL state is identified in the parameter plane of frequency detuning and injection power for different bias currents. As current decreases the frequency detuning range for the EPIL to exist is narrower and shifts toward the negative frequency detuning. Periodic dynamics of the VCSEL is found in the neighborhood of the EPIL regime. ©2014 Optical Society of America OCIS codes: (140.7260) Vertical cavity surface emitting lasers; (140.3520) Lasers, injectionlocked; (190.3100) Instabilities and chaos.
References and links 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
K. Iga, “Surface-emitting laser: its birth and generation of new optoelectronic field,” IEEE J. Sel. Top. Quantum Electron. 6(6), 1201–1215 (2000). K. Panajotov and F. Prati, “Polarization dynamics of VCSELs,” in Fundamentals, Technology and Applications of Vertical-Cavity Surface-Emitting Lasers, Vol. 166 of Springer Series in Optical Sciences, R. Michalzik, ed. (Springer, 2012), Chap. 6. K. D. Choquette, R. P. Schneider, K. L. Lear, and R. E. Leibenguth, “Gain-dependent polarization properties of vertical-cavity lasers,” IEEE J. Sel. Top. Quantum Electron. 1(2), 661–666 (1995). J. Martin-Regalado, F. Prati, M. San Miguel, and N. B. Abraham, “Polarization properties of vertical-cavity surface-emitting lasers,” IEEE J. Quantum Electron. 33(5), 765–783 (1997). A. Valle, L. Pesquera, and K. A. Shore, “Polarization behavior of birefringent multitransverse mode verticalcavity surface-emitting lasers,” IEEE Photonics Technol. Lett. 9(5), 557–559 (1997). K. Panajotov, B. Ryvkin, J. Danckaert, M. Peeters, H. Thienpont, and I. Veretennicoff, “Polarization switching in VCSELs due to thermal lensing,” IEEE Photonics Technol. Lett. 10(1), 6–8 (1998). B. Ryvkin, K. Panajotov, A. Georgievski, J. Danckaert, M. Peeters, G. Verschaffelt, H. Thienpont, and I. Veretennicoff, “Effect of photon-energy-dependent loss and gain mechanisms on polarization switching in vertical-cavity surface-emitting lasers,” J. Opt. Soc. Am. B 16, 2106–2113 (1999). J. Kaiser, C. Degen, and W. Elsässer, “Polarization switching influence on the intensity noise of vertical-cavity surface-emitting lasers,” J. Opt. Soc. Am. B 19(4), 672–677 (2002). M. Virte, K. Panajotov, H. Thienpont, and M. Sciamanna, “Deterministic polarization chaos from a laser diode,” Nat. Photonics 7(1), 60–65 (2013). J. Ohtsubo, Semiconductor Lasers: Stability, Instability, and Chaos, Springer Series in Optical Sciences (Springer, 2007). H. Li, T. L. Lucas, J. G. McInerney, M. W. Wright, and R. A. Morgan, “Injection locking dynamics of vertical cavity semiconductor lasers under conventional and phase conjugate injection,” IEEE J. Quantum Electron. 32(2), 227–235 (1996). Z. G. Pan, S. Jiang, M. Dagenais, R. A. Morgan, K. Kojima, M. T. Asom, R. E. Leibenguth, G. D. Guth, and M. W. Focht, “Optical injection induced polarization bistability in vertical-cavity surface-emitting lasers,” Appl. Phys. Lett. 63(22), 2999–3001 (1993). M. Sciamanna and K. Panajotov, “Route to polarization switching induced by optical injection in vertical- cavity surface-emitting lasers,” Phys. Rev. A 73(2), 023811 (2006). I. Gatare, M. Sciamanna, M. Nizette, and K. Panajotov, “Bifurcation to polarization switching and locking in vertical-cavity surface-emitting lasers with optical injection,” Phys. Rev. A 76(3), 031803 (2007).
#204189 - $15.00 USD (C) 2014 OSA
Received 6 Jan 2014; revised 14 Feb 2014; accepted 17 Feb 2014; published 24 Feb 2014 10 March 2014 | Vol. 22, No. 5 | DOI:10.1364/OE.22.004880 | OPTICS EXPRESS 4880
15. A. Homayounfar and M. J. Adams, “Analysis of nonlinear dynamics and spin-flip parameters on elliptically polarized injection-locked VCSELs,” Proc. SPIE 7036, 70361E (2008). 16. K. Panajotov, I. Gatare, A. Valle, H. Thienpont, and M. Sciamanna, “Polarization-and transverse mode dynamics in optically injected and gain-switched vertical-cavity surface-emitting lasers,” IEEE J. Quantum Electron. 45(11), 1473–1481 (2009). 17. M. S. Torre, A. Hurtado, A. Quirce, A. Valle, L. Pesquera, and M. J. Adams, “Polarization switching in longwavelength VCSELs subject to orthogonal optical injection,” IEEE J. Quantum Electron. 47(1), 92–99 (2011). 18. A. A. Qader, Y. Hong, and K. A. Shore, “Role of suppressed mode in the polarization switching characteristics of optically injected VCSELs,” IEEE J. Quantum Electron. 49(2), 205–210 (2013). 19. A. Hurtado, A. Quirce, A. Valle, L. Pesquera, and M. J. Adams, “Nonlinear dynamics induced by parallel and orthogonal optical injection in 1550 nm vertical-cavity surface-emitting lasers (VCSELs),” Opt. Express 18(9), 9423–9428 (2010). 20. R. Al-Seyab, K. Schires, N. A. Khan, A. Hurtado, I. D. Henning, and M. J. Adams, “Dynamics of polarized optical injection in 1550-nm VCSELs: theory and experiments,” IEEE J. Sel. Top. Quantum Electron. 17(5), 1242–1249 (2011). 21. A. Hurtado, I. D. Henning, and M. J. Adams, “Wavelength polarization switching and bistability in a 1550-nm VCSEL subject to polarized optical injection,” IEEE Photonics Technol. Lett. 21(15), 1084–1086 (2009). 22. P. Guo, T. Sun, W. Yang, D. Parekh, C. Zhang, X. Xie, C. J. Chang-Hasnain, A. Xu, and Z. Chen, “Optical phase modulation based on directly modulated reflection-mode OIL-VCSEL,” Opt. Express 21(19), 22114– 22123 (2013).
1. Introduction The vertical-cavity surface-emitting laser (VCSEL) has many advantages such as single longitudinal mode operation, circular beam profile, low threshold, and high bandwidth of modulation [1]. These advantages make VCSEL a promising device in telecommunications and other optoelectronic applications. However, a linearly polarized VCSEL can switch to the orthogonal polarization due to changes in bias current or operating temperature [2–7]. Spontaneous polarization switching is unwanted in polarization-sensitive applications. Therefore, the physical mechanism and control of polarization switching (PS) in VCSELs has attracted considerable research interests [2–9]. It is well known that optical injection can improve performance of semiconductor lasers and induce rich dynamics [10]. Effects of optical injection have been extensively studied in VCSELs [11–21]. Depending on the polarization of the injected beam, optical injection can be classified into parallel, orthogonal or arbitrary polarized injection. The so-called parallel injection is that the polarization of the injected beam is parallel to that of the VCSEL [11]. For the orthogonal injection, the polarization of the injected beam is perpendicular to that of the VCSEL [12]. Optical injection of arbitrary polarization has included the case of elliptically polarized injection [20,21]. These schemes can induce polarization switching. Rich dynamics is observed inside and around PS regime, including stable frequency locking, periodic pulsations (P1) and period doubling (P2), bistability and chaos [13–17, 19]. For frequency locked states, the frequency of the linearly polarized slave laser has been observed to lock to that of master laser, and the polarization of the slave laser is the same as the injected beam [16]. Recently, Sciamanna and Panajotov predicted a new stationary state— elliptically polarized injection-locked (EPIL) state—induced by orthogonal optical injection in a single transverse mode, linearly polarized solitary VCSEL [13]. In the EPIL state, the two polarizations of the slave laser are frequency locked to the master laser. Homayounfar and Adams showed numerically that the stability of the EPIL state can be increased by reducing the spin relaxation or increasing the birefringence and pumping [15]. However, to our best knowledge, the EPIL state was not observed experimentally. In this paper we report the first observation of the EPIL state in a VCSEL. We describe our setup and method in Section 2, and present the evidence of the EPIL state in Sec. 3. Then we discuss some issues encountered in our experiment and give our conclusion in Sec. 4 and Sec. 5, respectively. 2. Experimental setup and method We search for the EPIL state using an all-fiber setup. A stabilized tunable laser (the master laser, TL) provides optical injection to a single-transverse-mode VCSEL (slave laser). The device is a commercially available quantum-well 1550 nm VCSEL (Raycan). The threshold #204189 - $15.00 USD (C) 2014 OSA
Received 6 Jan 2014; revised 14 Feb 2014; accepted 17 Feb 2014; published 24 Feb 2014 10 March 2014 | Vol. 22, No. 5 | DOI:10.1364/OE.22.004880 | OPTICS EXPRESS 4881
current of the VCSEL is 1.6 mA. From threshold to 6 mA, the free-running VCSEL emits a linearly polarized beam that is named parallel polarization. The polarization perpendicular to this state is termed orthogonal polarization, which is more than 30 dB weaker than the parallel polarization. In our experiment, the maximum bias current is set at 4 mA, well below the 6 mA at which the intrinsic PS of the VCSELoccurs. The output power and the relaxation oscillation frequency of the VCSEL at 4 mA are 0.32 mW and 2.8 GHz, respectively. Figure 1(a) shows the experimental setup. The output power from the master laser can be adjusted with a variable attenuator (VA). We use a polarization controller, PC1, to make the polarization of the injected beam orthogonal to the parallel polarization of the VCSEL. The beam from the master laser goes through an optical circulator, OC, and is split by a 90:10 fibre directional coupler. Approximate 90% of the incident beam is sent to the VCSEL, and ~10% of the incident beam is monitored by a power meter, PM. After taking the loss at fiber adaptors into account, we measured that the power of injection, Pinj, in front of the VCSEL is five times the reading of the power meter. That is, Pinj = 5PPM. The output of the VCSEL goes through a polarization controller, PC2, and is connected to a polarization beam splitter, PBS, with a nominal separation ratio of 26 dB. We use PC2 to maximize the contrast of two polarizations perpendicular to each other. The power of the strong polarization is around 30 dB stronger than that of the weak polarization. This agrees with the spectrum observed on the optical spectral analyzer (BOSA). Therefore, the strong beam from the PBS is the parallel polarization, and the weak beam is the orthogonal polarization. Wavelengths of the parallel and orthogonal polarizations are λ// = 1538.01 nm and λ⊥ = 1538.24 nm, respectively.
Fig. 1. (a) Schematic diagram of the experimental setup. (b) Optical spectrum of the freerunning VCSEL biased with a current of 4 mA.
We study the effect of the orthogonal optical injection around λ//. The power of each polarization of the VCSEL is measured with a power meter when the wavelength of the injection, λinj, is tuned with fine steps. Another method is to find the power of each polarization by using the power integral function of BOSA, an optical spectrum analyzer with resolution of 0.1 pm. Optical spectra of the VCSEL are measured with BOSA. An example of the optical spectrum of the free-running VCSEL is shown in Fig. 1(b). Figure 2 shows the dependence of the polarization resolved powers on λinj and frequency detuning, ∆ν, separately. The frequency detuning is defined as ∆ν≡νinj-ν//,free, where ν//,free is the frequency of the parallel polarization of the solitary VCSEL. For λinj
Department of Physics and Astronomy, Bates College, Lewiston, Maine 04240, USA Instituto de Física de Cantabria (CSIC-Univ. Cantabria), Avda. Los Castros s/n, E39005 Santander, Spain 3 Dept. de Física Moderna, Fac. Ciencias, Univ. Cantabria, Avda. Los Castros s/n, E39005 Santander, Spain * [email protected] 2
Abstract: We demonstrate experimentally the existence of the elliptically polarized injection-locked (EPIL) state. This state is observed when a single-transverse mode VCSEL is subject to orthogonal optical injection. The spectral feature of the EPIL state is verified and the power of each polarization is measured. The regime of the EPIL state is identified in the parameter plane of frequency detuning and injection power for different bias currents. As current decreases the frequency detuning range for the EPIL to exist is narrower and shifts toward the negative frequency detuning. Periodic dynamics of the VCSEL is found in the neighborhood of the EPIL regime. ©2014 Optical Society of America OCIS codes: (140.7260) Vertical cavity surface emitting lasers; (140.3520) Lasers, injectionlocked; (190.3100) Instabilities and chaos.
References and links 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
K. Iga, “Surface-emitting laser: its birth and generation of new optoelectronic field,” IEEE J. Sel. Top. Quantum Electron. 6(6), 1201–1215 (2000). K. Panajotov and F. Prati, “Polarization dynamics of VCSELs,” in Fundamentals, Technology and Applications of Vertical-Cavity Surface-Emitting Lasers, Vol. 166 of Springer Series in Optical Sciences, R. Michalzik, ed. (Springer, 2012), Chap. 6. K. D. Choquette, R. P. Schneider, K. L. Lear, and R. E. Leibenguth, “Gain-dependent polarization properties of vertical-cavity lasers,” IEEE J. Sel. Top. Quantum Electron. 1(2), 661–666 (1995). J. Martin-Regalado, F. Prati, M. San Miguel, and N. B. Abraham, “Polarization properties of vertical-cavity surface-emitting lasers,” IEEE J. Quantum Electron. 33(5), 765–783 (1997). A. Valle, L. Pesquera, and K. A. Shore, “Polarization behavior of birefringent multitransverse mode verticalcavity surface-emitting lasers,” IEEE Photonics Technol. Lett. 9(5), 557–559 (1997). K. Panajotov, B. Ryvkin, J. Danckaert, M. Peeters, H. Thienpont, and I. Veretennicoff, “Polarization switching in VCSELs due to thermal lensing,” IEEE Photonics Technol. Lett. 10(1), 6–8 (1998). B. Ryvkin, K. Panajotov, A. Georgievski, J. Danckaert, M. Peeters, G. Verschaffelt, H. Thienpont, and I. Veretennicoff, “Effect of photon-energy-dependent loss and gain mechanisms on polarization switching in vertical-cavity surface-emitting lasers,” J. Opt. Soc. Am. B 16, 2106–2113 (1999). J. Kaiser, C. Degen, and W. Elsässer, “Polarization switching influence on the intensity noise of vertical-cavity surface-emitting lasers,” J. Opt. Soc. Am. B 19(4), 672–677 (2002). M. Virte, K. Panajotov, H. Thienpont, and M. Sciamanna, “Deterministic polarization chaos from a laser diode,” Nat. Photonics 7(1), 60–65 (2013). J. Ohtsubo, Semiconductor Lasers: Stability, Instability, and Chaos, Springer Series in Optical Sciences (Springer, 2007). H. Li, T. L. Lucas, J. G. McInerney, M. W. Wright, and R. A. Morgan, “Injection locking dynamics of vertical cavity semiconductor lasers under conventional and phase conjugate injection,” IEEE J. Quantum Electron. 32(2), 227–235 (1996). Z. G. Pan, S. Jiang, M. Dagenais, R. A. Morgan, K. Kojima, M. T. Asom, R. E. Leibenguth, G. D. Guth, and M. W. Focht, “Optical injection induced polarization bistability in vertical-cavity surface-emitting lasers,” Appl. Phys. Lett. 63(22), 2999–3001 (1993). M. Sciamanna and K. Panajotov, “Route to polarization switching induced by optical injection in vertical- cavity surface-emitting lasers,” Phys. Rev. A 73(2), 023811 (2006). I. Gatare, M. Sciamanna, M. Nizette, and K. Panajotov, “Bifurcation to polarization switching and locking in vertical-cavity surface-emitting lasers with optical injection,” Phys. Rev. A 76(3), 031803 (2007).
#204189 - $15.00 USD (C) 2014 OSA
Received 6 Jan 2014; revised 14 Feb 2014; accepted 17 Feb 2014; published 24 Feb 2014 10 March 2014 | Vol. 22, No. 5 | DOI:10.1364/OE.22.004880 | OPTICS EXPRESS 4880
15. A. Homayounfar and M. J. Adams, “Analysis of nonlinear dynamics and spin-flip parameters on elliptically polarized injection-locked VCSELs,” Proc. SPIE 7036, 70361E (2008). 16. K. Panajotov, I. Gatare, A. Valle, H. Thienpont, and M. Sciamanna, “Polarization-and transverse mode dynamics in optically injected and gain-switched vertical-cavity surface-emitting lasers,” IEEE J. Quantum Electron. 45(11), 1473–1481 (2009). 17. M. S. Torre, A. Hurtado, A. Quirce, A. Valle, L. Pesquera, and M. J. Adams, “Polarization switching in longwavelength VCSELs subject to orthogonal optical injection,” IEEE J. Quantum Electron. 47(1), 92–99 (2011). 18. A. A. Qader, Y. Hong, and K. A. Shore, “Role of suppressed mode in the polarization switching characteristics of optically injected VCSELs,” IEEE J. Quantum Electron. 49(2), 205–210 (2013). 19. A. Hurtado, A. Quirce, A. Valle, L. Pesquera, and M. J. Adams, “Nonlinear dynamics induced by parallel and orthogonal optical injection in 1550 nm vertical-cavity surface-emitting lasers (VCSELs),” Opt. Express 18(9), 9423–9428 (2010). 20. R. Al-Seyab, K. Schires, N. A. Khan, A. Hurtado, I. D. Henning, and M. J. Adams, “Dynamics of polarized optical injection in 1550-nm VCSELs: theory and experiments,” IEEE J. Sel. Top. Quantum Electron. 17(5), 1242–1249 (2011). 21. A. Hurtado, I. D. Henning, and M. J. Adams, “Wavelength polarization switching and bistability in a 1550-nm VCSEL subject to polarized optical injection,” IEEE Photonics Technol. Lett. 21(15), 1084–1086 (2009). 22. P. Guo, T. Sun, W. Yang, D. Parekh, C. Zhang, X. Xie, C. J. Chang-Hasnain, A. Xu, and Z. Chen, “Optical phase modulation based on directly modulated reflection-mode OIL-VCSEL,” Opt. Express 21(19), 22114– 22123 (2013).
1. Introduction The vertical-cavity surface-emitting laser (VCSEL) has many advantages such as single longitudinal mode operation, circular beam profile, low threshold, and high bandwidth of modulation [1]. These advantages make VCSEL a promising device in telecommunications and other optoelectronic applications. However, a linearly polarized VCSEL can switch to the orthogonal polarization due to changes in bias current or operating temperature [2–7]. Spontaneous polarization switching is unwanted in polarization-sensitive applications. Therefore, the physical mechanism and control of polarization switching (PS) in VCSELs has attracted considerable research interests [2–9]. It is well known that optical injection can improve performance of semiconductor lasers and induce rich dynamics [10]. Effects of optical injection have been extensively studied in VCSELs [11–21]. Depending on the polarization of the injected beam, optical injection can be classified into parallel, orthogonal or arbitrary polarized injection. The so-called parallel injection is that the polarization of the injected beam is parallel to that of the VCSEL [11]. For the orthogonal injection, the polarization of the injected beam is perpendicular to that of the VCSEL [12]. Optical injection of arbitrary polarization has included the case of elliptically polarized injection [20,21]. These schemes can induce polarization switching. Rich dynamics is observed inside and around PS regime, including stable frequency locking, periodic pulsations (P1) and period doubling (P2), bistability and chaos [13–17, 19]. For frequency locked states, the frequency of the linearly polarized slave laser has been observed to lock to that of master laser, and the polarization of the slave laser is the same as the injected beam [16]. Recently, Sciamanna and Panajotov predicted a new stationary state— elliptically polarized injection-locked (EPIL) state—induced by orthogonal optical injection in a single transverse mode, linearly polarized solitary VCSEL [13]. In the EPIL state, the two polarizations of the slave laser are frequency locked to the master laser. Homayounfar and Adams showed numerically that the stability of the EPIL state can be increased by reducing the spin relaxation or increasing the birefringence and pumping [15]. However, to our best knowledge, the EPIL state was not observed experimentally. In this paper we report the first observation of the EPIL state in a VCSEL. We describe our setup and method in Section 2, and present the evidence of the EPIL state in Sec. 3. Then we discuss some issues encountered in our experiment and give our conclusion in Sec. 4 and Sec. 5, respectively. 2. Experimental setup and method We search for the EPIL state using an all-fiber setup. A stabilized tunable laser (the master laser, TL) provides optical injection to a single-transverse-mode VCSEL (slave laser). The device is a commercially available quantum-well 1550 nm VCSEL (Raycan). The threshold #204189 - $15.00 USD (C) 2014 OSA
Received 6 Jan 2014; revised 14 Feb 2014; accepted 17 Feb 2014; published 24 Feb 2014 10 March 2014 | Vol. 22, No. 5 | DOI:10.1364/OE.22.004880 | OPTICS EXPRESS 4881
current of the VCSEL is 1.6 mA. From threshold to 6 mA, the free-running VCSEL emits a linearly polarized beam that is named parallel polarization. The polarization perpendicular to this state is termed orthogonal polarization, which is more than 30 dB weaker than the parallel polarization. In our experiment, the maximum bias current is set at 4 mA, well below the 6 mA at which the intrinsic PS of the VCSELoccurs. The output power and the relaxation oscillation frequency of the VCSEL at 4 mA are 0.32 mW and 2.8 GHz, respectively. Figure 1(a) shows the experimental setup. The output power from the master laser can be adjusted with a variable attenuator (VA). We use a polarization controller, PC1, to make the polarization of the injected beam orthogonal to the parallel polarization of the VCSEL. The beam from the master laser goes through an optical circulator, OC, and is split by a 90:10 fibre directional coupler. Approximate 90% of the incident beam is sent to the VCSEL, and ~10% of the incident beam is monitored by a power meter, PM. After taking the loss at fiber adaptors into account, we measured that the power of injection, Pinj, in front of the VCSEL is five times the reading of the power meter. That is, Pinj = 5PPM. The output of the VCSEL goes through a polarization controller, PC2, and is connected to a polarization beam splitter, PBS, with a nominal separation ratio of 26 dB. We use PC2 to maximize the contrast of two polarizations perpendicular to each other. The power of the strong polarization is around 30 dB stronger than that of the weak polarization. This agrees with the spectrum observed on the optical spectral analyzer (BOSA). Therefore, the strong beam from the PBS is the parallel polarization, and the weak beam is the orthogonal polarization. Wavelengths of the parallel and orthogonal polarizations are λ// = 1538.01 nm and λ⊥ = 1538.24 nm, respectively.
Fig. 1. (a) Schematic diagram of the experimental setup. (b) Optical spectrum of the freerunning VCSEL biased with a current of 4 mA.
We study the effect of the orthogonal optical injection around λ//. The power of each polarization of the VCSEL is measured with a power meter when the wavelength of the injection, λinj, is tuned with fine steps. Another method is to find the power of each polarization by using the power integral function of BOSA, an optical spectrum analyzer with resolution of 0.1 pm. Optical spectra of the VCSEL are measured with BOSA. An example of the optical spectrum of the free-running VCSEL is shown in Fig. 1(b). Figure 2 shows the dependence of the polarization resolved powers on λinj and frequency detuning, ∆ν, separately. The frequency detuning is defined as ∆ν≡νinj-ν//,free, where ν//,free is the frequency of the parallel polarization of the solitary VCSEL. For λinj
