23 research outputs found
Experimental Confirmation of the General Solution to the Multiple Phase Matching Problem
We recently described a general solution to the phase matching problem that
arises when one wishes to perform an arbitrary number of nonlinear optical
processes in a single medium [PRL 95 (2005) 133901]. Here we outline in detail
the implementation of the solution for a one dimensional photonic quasicrystal
which acts as a simultaneous frequency doubler for three independent optical
beams. We confirm this solution experimentally using an electric field poled
KTiOPO crystal. In optimizing the device, we find - contrary to common
practice - that simple duty cycles of 100% and 0% may yield the highest
efficiencies, and show that our device is more efficient than a comparable
device based on periodic quasi-phase-matching
Polychromatic solitons in a quadratic medium
We introduce the simplest model to describe parametric interactions in a
quadratically nonlinear optical medium with the fundamental harmonic containing
two components with (slightly) different carrier frequencies [which is a direct
analog of wavelength-division multiplexed (WDM) models, well known in media
with cubic nonlinearity]. The model takes a closed form with three different
second-harmonic components, and it is formulated in the spatial domain. We
demonstrate that the model supports both polychromatic solitons (PCSs), with
all the components present in them, and two types of mutually orthogonal simple
solitons, both types being stable in a broad parametric region. An essential
peculiarity of PCS is that its power is much smaller than that of a simple
(usual) soliton (taken at the same values of control parameters), which may be
an advantage for experimental generation of PCSs. Collisions between the
orthogonal simple solitons are simulated in detail, leading to the conclusion
that the collisions are strongly inelastic, converting the simple solitons into
polychromatic ones, and generating one or two additional PCSs. A collision
velocity at which the inelastic effects are strongest is identified, and it is
demonstrated that the collision may be used as a basis to design a simple
all-optical XOR logic gate.Comment: 9 pages, 8 figures, accepted to Phys. Rev.
Engineering of spatial solitons in two-period QPM structures
We report on a scheme which might make it practically possible to engineer
the effective competing nonlinearities that on average govern the light
propagation in quasi-phase-matching (QPM) gratings. Modulation of the QPM
period with a second longer period, introduces an extra degree of freedom,
which can be used to engineer the effective quadratic and induced cubic
nonlinearity. However, in contrast to former work here we use a simple
phase-reversal grating for the modulation, which is practically realizable and
has already been fabricated. Furthermore, we develop the theory for arbitrary
relative lengths of the two periods and we consider the effect on solitons and
the bandwidth for their generation. We derive an expression for the bandwidth
of multicolor soliton generation in two-period QPM samples and we predict and
confirm numerically that the bandwidth is broader in the two-period QPM sample
than in homogeneous structures.Comment: V1: 15 pages, 8 figures. V2: Accepted for publication in Optics
Communications.16 pages, 10 figures. New soliton content figures, confirming
the theoretically predicted peak splitting in 2-period QPM, have been
include
Multistep Parametric Processes in Nonlinear Optics
We present a comprehensive overview of different types of parametric
interactions in nonlinear optics which are associated with simultaneous
phase-matching of several optical processes in quadratic nonlinear media, the
so-called multistep parametric interactions. We discuss a number of
possibilities of double and multiple phase-matching in engineered structures
with the sign-varying second-order nonlinear susceptibility, including (i)
uniform and non-uniform quasi-phase-matched (QPM) periodic optical
superlattices, (ii) phase-reversed and periodically chirped QPM structures, and
(iii) uniform QPM structures in non-collinear geometry, including recently
fabricated two-dimensional nonlinear quadratic photonic crystals. We also
summarize the most important experimental results on the multi-frequency
generation due to multistep parametric processes, and overview the physics and
basic properties of multi-color optical parametric solitons generated by these
parametric interactions.Comment: To be published in Progress in Optic