Control of signal coherence in parametric frequency mixing with incoherent pumps: narrowband mid-infrared light generation by downconversion of broadband amplified spontaneous emission source at 1550 nm

Abstract

We study, with numerical simulations using the generalized nonlinear envelope equation, the processes of optical parametric and difference-and sum-frequency generation (SFG) with incoherent pumps in optical media with both quadratic and third-order nonlinearity, such as periodically poled lithium niobate. With ultrabroadband amplified spontaneous emission pumps or continua (spectral widths >10 THz), group-velocity matching of a near-IR pump and a short-wavelength mid-IR (MIR) idler in optical parametric generation may lead to more than 15-fold relative spectral narrowing of the generated MIR signal. Moreover, the SFG process may also lead to 6-fold signal coherence improvements. When using relatively narrowband filtered noise pumps (e.g., spectral widths < 1 THz), the signal from optical parametric, sum-frequency, and difference-frequency generation has nearly the same spectral width as that of the incoherent pump.

Demonstration of a frequency spectral compression effect through an up-conversion interferometer

“…The use of a broad pump spectrum is mandatory to obtain the frequency spectral compression effect. Indeed, with a monochromatic pump, the slope b num is not defined and there is no frequency compression, as it has been investigated in [9] and [11].…”

“…This interferometric configuration has two main goals. The first one is to experimentally demonstrate the frequency spectral compression [9]. Indeed, the line frequency separation change between the input and converted doublets can be extracted from the analysis of the fringe pattern envelopes [11].…”

“…As a long term goal we intend to study a SFG process powered by a pump frequency comb to increase the spectral bandwidth to be analyzed while preserving signal coherence information. Wabnitz et al have recently demonstrated numerically that the use of a non-monochromatic pump source to power a SFG process, converting a large spectral bandwidth infrared signal, leads to a frequency spectral compression of the converted wave through the non-linear process [9].…”

Incoherent Fermi-Pasta-Ulam Recurrences and Unconstrained Thermalization Mediated by Strong Phase Correlations

“…For this purpose, we develop a nonequilibrium kinetic theory that accounts for the existence of phase correlations among the random waves. Phase correlations are known to play a role in different cases [7][8][9][49][50][51][52][53][54][55][56][57][58]; in particular, they lead to the formation of large-scale coherent structures (solitons or condensates) emerging from a strongly nonlinear turbulent regime [38][39][40][41][42][43][44][45][46]59-65]-a coherent structure being inherently a phase-correlated object. Also note that stochastic recurrences of random waves have been predicted recently for water waves governed by Alber's equation when nonlinear effects are stronger than linear dispersive effects [66].…”

Single envelope equation modeling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearities

“…In this work, we present a more general model of ultrabroadband frequency comb generation in cavities where several nonlinearities may act simultaneously, based on the single envelope equation (SEE) [23][24][25][26][27][28]. Compared to previous models where a single dominant nonlinear process (e.g., singly or doubly resonant cavity SHG) is involved [21,22], the SEE model has its relative strength in its greater generality, as all nonlinear processes are simultaneously included.…”