Dynamics and Frequency Response of Microring-Based Optical Modulator Considering Nonlinear Effects

• Published in: Journal of lightwave technology Vol. 30; no. 23; pp. 3720 - 3726
• Main Authors: Mohammadi, F., Ahmadi, V., Gandomkar, M.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2012; Institute of Electrical and Electronics Engineers
• Subjects: All optical circuits; All-optical modulation; Applied sciences; Circuit properties; coupling factor modulation; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Finite difference methods; free-carrier (FC) plasma effect; Frequency response; Fundamental areas of phenomenology (including applications); Integrated optics. Optical fibers and wave guides; Laser optical systems: design and operation; microring resonator; Optical and optoelectronic circuits; Optical modulation; Optical resonators; Optical ring resonators; Optics; Physics; Resonators, cavities, amplifiers, arrays, and rings; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); two-photon absorption (TPA); GHz range; Refraction index; two-photon absorption (TPA); Frequency shift; Resonance frequency; Coupling factor; Frequency response; Two photon absorption; Optical modulation; Dynamic response; coupling factor modulation; Dynamic characteristic; Optical modulator; Finite difference time-domain analysis; All optical circuit; Free carrier; Ring resonator; Coupling coefficient; All-optical modulation; Waveguide junction; Timing; free-carrier (FC) plasma effect; Non linear effect; Intensity modulation; microring resonator
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2012.2227240

In this paper, we analyze dynamics and frequency response of GaAs-based microring modulators at the 1.55 μm using the finite-difference time-domain method. Two types of modulation are investigated: pump-probe configuration and modulation of the coupling coefficient. The pump-probe signals are tuned at separate resonance wavelengths of the microring. Change of effective refractive index of the microring by two-photon absorption is used to modulate the probe beam. By applying probe beam in four timing configurations, it is shown that the wavelength shift of the probe depends not only on the pump intensity but also on the interaction length over which the pump and probe pulses overlap. It is also shown that free-carrier absorption increases when the temporal width of pump signal is wide enough. Modulation bandwidth of microring in the presence of nonlinear effects is investigated and it is shown that the bandwidth is in 10 GHz range. In order to increase the bandwidth of the intensity modulator, controlled coupling is used. It is shown that in this case, modulation bandwidth of waveguide-ring coupling strength becomes three times wider.