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Publication list, including conference papers, is available on Google Scholar.
- Ali Eshaghian Dorche, Sajjad Abdollahramezani, Hossein Taheri, Ali Asghar Eftekhar, and Ali Adibi. "Extending chip-based Kerr-comb to visible spectrum by dispersive wave engineering." Optics Express 25, no. 19 (2017): 22362-22374.
Abstract: Anomalous group velocity dispersion is a key parameter for generating bright solitons, and thus wideband Kerr frequency combs. Extension of the frequency combs spectrum to visible wavelengths has been a major challenge because of the strong normal dispersion of conventional photonic materials at these wavelengths. In this paper, we numerically demonstrate a wideband frequency comb extending from near-infrared to visible wavelengths (∼1200 nm to 650 nm). The proposed frequency comb micro-resonator takes advantage of a wideband blue-shifted anomalous dispersion, achieved in an optimized over-etched silicon nitride waveguide and strong power transfer to shorter wavelengths through radiative dispersive waves, achieved by modulating the dispersion in a coupled resonator architecture. We show the possibility of obtaining a close to visible dispersive Cherenkov radiation peak that is only 10 dB below the overall comb peak and can be tuned by adjusting the coupling structure in the coupled resonator architecture.
- Hossein Taheri, Pascal Del'Haye, Ali A. Eftekhar, Kurt Wiesenfeld, and Ali Adibi. "Self-synchronization phenomena in the Lugiato-Lefever equation." Physical Review A 96, no. 1 (2017): 013828.
Abstract: The damped driven nonlinear Schrödinger equation (NLSE) has been used to understand a range of physical phenomena in diverse systems. Studying this equation in the context of optical hyperparametric oscillators in anomalous-dispersion dissipative cavities, where NLSE is usually referred to as the Lugiato-Lefever equation, we are led to a reduced nonlinear oscillator model that uncovers the essence of the spontaneous creation of sharply peaked pulses in optical resonators. We identify attracting solutions for this model, which correspond to stable cavity solitons and Turing patterns, and study their degree of stability. The reduced model embodies the fundamental connection between mode synchronization and spatiotemporal pattern formation and represents a class of self-synchronization processes in which coupling between nonlinear oscillators is governed by energy and momentum conservation.
- Hossein Taheri, Andrey B. Matsko, and Lute Maleki. "Optical lattice trap for Kerr solitons." The European Physical Journal D 71, no. 6 (2017): 153.
Abstract: We show theoretically and numerically that dichromatic pumping of a nonlinear microresonator by two continuous wave coherent optical pumps creates an optical lattice trap that results in the localization of intra-cavity Kerr solitons with soliton positions defined by the beat frequency of the two pumps. This phenomenon corresponds to the stabilization of the comb repetition rate. The locking of the second pump, through adiabatic tuning of its frequency, to the comb generated by the first pump allows transitioning to single-soliton states, manipulating the position of Kerr solitons in the cavity, and tuning the frequency comb repetition rate within the locking range. It also explains soliton crystal formation in resonators supporting a dispersive wave emitted as a result of higher-order group velocity dispersion or avoided mode crossing. We show that dichromatic pumping by externally stabilized pumps can be utilized for stabilization of microresonator-based optical frequency combs when the comb span does not cover an octave or a significant fraction thereof and standard self-referencing techniques cannot be employed. Our findings have significant ramifications for high-precision applications of optical frequency combs in spectrally pure signal generation, metrology, and timekeeping.
- Hossein Taheri, Ali A. Eftekhar, Kurt Wiesenfeld, and Ali Adibi. "Anatomy of phase locking in hyperparametric oscillations based on Kerr nonlinearity." IEEE Photonics Journal 9, no. 3 (2017): 1-11.
Abstract: We investigate the dynamical origin of synchronization and phase locking of hyperparametric oscillations in Kerr-nonlinear media. These oscillations occur in the presence of parametric gain and, although arising from modulational instability of random vacuum fluctuations with arbitrary phases, lead to phase-locked states in the form of pulse trains. Using few-mode approximations of the Lugiato-Lefever equation (LLE), we find that the pumped mode injection-locks to the driving laser pump following the Adler equation. Based on experimentally motivated assumptions, we derive analytical expressions, which reveal the essence of phase locking in frequency combs and confirm them through numerical integration of the LLE. Clear understanding of the phenomenon of phase locking in optical microresonators can lead to devising novel techniques for achieving phase-locked states or improving the coherence properties of frequency combs. Our results are mathematically generic and apply to other systems described by an externally driven damped nonlinear Schödinger equation.
- Changjing Bao, Hossein Taheri, Lin Zhang, Andrey Matsko, Yan Yan, Peicheng Liao, Lute Maleki, and Alan E. Willner. "High-order dispersion in Kerr comb oscillators." JOSA B 34, no. 4 (2017): 715-725.
Abstract: We numerically investigate the effect of high-order dispersion on Kerr frequency comb generation in optical microresonators characterized with anomalous group velocity dispersion (GVD) using realistic slot-waveguide-based silicon nitride microring and spheroidal crystalline magnesium fluoride resonators. Our numerical simulations indicate that all orders of GVD should be taken into account to obtain the correct envelope shape of the generated Kerr frequency comb. High-order GVD affects the 3 dB comb bandwidth, nonlinear conversion efficiency, and frequency recoil of the comb spectrum (i.e., spectral shift effect), as well as pulse peak power and the power dependence of the pulse timing. Additionally, high-order dispersion terms affect the spectral position of a dispersive wave generated in a microresonator. Our results emphasize the influence of the pump power on the dispersive wave radiation frequency as well as the repetition rate of the generated frequency comb. The latter has significant practical ramifications, for instance, for the use of resonator-based frequency combs in optical clocks. We also observe competition in the generation of two different pulses corresponding to nearly the same spectral envelope. These mode-locked combs appear in the presence of a strong negative fourth-order GVD; one of them takes a hyperbolic-secant soliton shape, while the other resembles a Gaussian pulse superimposed on a modulated pedestal. The appearance and stability of the latter pulse depend on the numerical integration technique utilized.
- Sara Hassanpour‐Tamrin, Hossein Taheri, Mohammad Mahdi Hasani‐Sadrabadi, S. Hamed Shams Mousavi, Erfan Dashtimoghadam, Mahdi Tondar, Ali Adibi, Alireza Moshaverinia, Amir Sanati Nezhad, and Karl I. Jacob. "Nanoscale Optoregulation of Neural Stem Cell Differentiation by Intracellular Alteration of Redox Balance." Advanced Functional Materials 27, no. 38 (2017): 1701420.
Abstract: Regulation of stem cell (SC) fate, a decision between self‐renewal and differentiation, is of immense importance in regenerative medicine and has been proven to be a powerful stimulus regulating many cell functions influencing the SC fate. This study uses triphenylphosphonium‐functionalized gold nanoparticles (TPP‐AuNPs) to explore the interplay of intracellular electromagnetic (EM) exposure and the SC fate. Localized EM waves are generated inside neural stem cells (NSCs) to stimulate TPP‐AuNPs (AuNPs), targeting the mitochondria through inducing reactive oxygen species and differentiating these cells into neurons. Following laser irradiation of TPP‐AuNPs‐transfected NSCs, their differentiation to neurons is monitored by tracing the relevant markers both at the genetic and protein levels. The electrophysiology technique is further used to examine the functionality of neurons. The results confirm that TPP‐AuNPs subjected to electromotive forces have the potential to regulate cellular fate, although further investigations are still required to shed light on the mechanisms underlying the interaction of EM‐stimulated TPP‐AuNPs on cellular fate to design highly adjustable cell differentiation and reprogramming methods.
- Hossein Taheri, Ali A. Eftekhar, Kurt Wiesenfeld, and Ali Adibi. "Soliton formation in whispering-gallery-mode resonators via input phase modulation." IEEE Photon. J. 7, no. 2 (2015).
Abstract: We propose a systematic method for soliton formation in whispering-gallery-mode (WGM) resonators through input phase modulation. Our numerical simulations of a variant of the Lugiato-Lefever equation suggest that modulating the input phase at a frequency equal to the resonator free-spectral-range and at modest modulation depths provides a deterministic route towards soliton formation in WGM resonators without undergoing a chaotic phase. We show that the generated solitonic state is sustained when the modulation is turned off adiabatically. Our results support parametric seeding as a powerful means of control, besides input pump power and pump-resonance detuning, over frequency comb generation in WGM resonators. Our findings also help pave the path towards ultra-short pulse formation on a chip.
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