Abstract
An approach to reconstruct a quasi-phase-matching grating by using a discrete layer-peeling algorithm is presented. Experimentally measured output spectra of Šolc-type filters, based on uniform and chirped QPM structures, are used in the discrete layer-peeling algorithm. The reconstructed QPM structures are in agreement with the exact structures used in the experiment and the method is verified to be accurate and efficient in quality inspection on quasi-phase-matching grating.
Highlights
Quasi-phase-matching (QPM) nonlinear devices, such as periodically poled lithium niobate (PPLN) and lithium tantalite (PPLT), have been widely studied in the field of nonlinear optical interactions because of their capability of achieving the desired phase-matching condition by spatially modulating the quadratic nonlinearities [1]
Recent attention has been given from uniform structure to Fibonacci optical superlattice [2], linearly chirped [3], apodized [4, 5], multi-segmented [6], and aperiodically QPM gratings [7, 8], which can provide more spatial reciprocal vectors to compensate for nonlinear phase mismatch in the broadband nonlinear process and multi-wavelength second harmonic generation (SHG)
We show an approach to reconstruct quasi-phase-matching gratings by using a discrete layerpeeling (DLP) algorithm
Summary
Quasi-phase-matching (QPM) nonlinear devices, such as periodically poled lithium niobate (PPLN) and lithium tantalite (PPLT), have been widely studied in the field of nonlinear optical interactions because of their capability of achieving the desired phase-matching condition by spatially modulating the quadratic nonlinearities [1]. Recent attention has been given from uniform structure to Fibonacci optical superlattice [2], linearly chirped [3], apodized [4, 5], multi-segmented [6], and aperiodically QPM gratings [7, 8], which can provide more spatial reciprocal vectors to compensate for nonlinear phase mismatch in the broadband nonlinear process and multi-wavelength second harmonic generation (SHG). DLP method was proven to be a simple, accurate and efficient approach to reconstruct the local structure of refractive index of fiber bragg grating [13,14,15,16] and other optical devices [17]. The ordinary and extraordinary waves propagating in QPM gratings are phase-matched due to the reciprocal vectors from the modulation of electro-optical (EO) coefficient in Solc-type filters, which can be considered as a grating-assisted co-directional coupler, such as long period fiber grating based on refractive index modulation in the coupling region. We successfully use DLP algorithm to reconstruct the poling structure of QPM gratings in this work
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