Modelocking and femtosecond pulse generation in chip-based frequency combs

Abstract

Abstract:We investigate simultaneously the temporal and optical and radio-frequency spectral properties of parametric frequency combs generated in silicon-nitride microresonators and observe that the system undergoes a transition to a mode-locked state. We demonstrate the generation of sub-200-fs pulses at a repetition rate of 99 GHz. Our calculations show that pulse generation in this system is consistent with soliton modelocking. Ultimately, such parametric devices offer the potential of producing ultrashort laser pulses from the visible to mid-infrared regime at repetition rates from GHz to THz.

New CMOS-compatible platforms based on silicon nitride and Hydex for nonlinear optics

“…Further studies [70] of the optical and radio-frequency properties of parametric frequency combs in SiN microresonators show a transition to a modelocked state where ultrashort pulse generation is possible. From a 25-nm filtered section of the 300-nm comb spectrum, sub-200-fs pulses were observed with calculations indicating that the pulse generation process is consistent with soliton modelocking.…”

“…The last two years have seen significant breakthroughs in understanding the dynamics and coherence behavior associated with frequency comb formation [65][66][67][68][69][70]. These reports have revealed complex and distinct paths to comb formation that can result in widely varying degrees of coherence, wavelength spacing, and RF stability of these sources.…”

“…Since the demonstration of OFCs in SiN [57] and Hydex [58] in 2010, this field has proliferated. Extremely wide-band frequency combs [64 -66], sub 100-GHz combs [67], line-by-line arbitrary optical waveform generation [68], ultrashort pulse generation [15,70], and dual frequency combs [71] have been reported. In addition, OFC harmonic generation [72] has been observed.…”

Mode-locked dark pulse Kerr combs in normal-dispersion microresonators

“…Experiments have revealed transitions from low coherence, high noise states to highly coherent mode-locked states accompanied by a sudden drop in the comb noise [14]- [18]. It has been found in simulations and experiments that the mode locking of broadband Kerr combs is usually related to soliton formation in the cavity [15], [17]-[28]. These dissipative cavity solitons are localized structures stabilized by a balance between Kerr nonlinearity and dispersion.…”

“…In time domain they exist as bright or dark pulses, depending on whether the cavity dispersion is anomalous or normal, respectively. Bright microresonator solitons in the anomalous dispersion region have been observed in experiments and well studied through simulations [15], [17]-[27]. Reference [17] reported a method of tuning the pump laser frequency to an effectively red-detuned regime (pump laser wavelength longer than resonant wavelength) which is typically difficult to achieve due to thermal instability [29].…”