5,698 research outputs found
Shuttle/GPSPAC experimentation study
The utilization is discussed of the GPSPAC, which is presently being developed to be used on the low altitude host vehicle (LAHV), for possible use in the shuttle avionics system to evaluate shuttle/GPS navigation performance. Analysis and tradeoffs of the shuttle/GPS link, shuttle signal interface requirements, oscillator tradeoffs and GPSPAC mechanical modifications for shuttle are included. Only the on-orbit utilization of GPSPAC for the shuttle is discussed. Other phases are briefly touched upon. Recommendations are provided for using the present GPSPAC and the changes required to perform shuttle on-orbit navigation
Scaling laws for soliton pulse compression by cascaded quadratic nonlinearities
We present a detailed study of soliton compression of ultra-short pulses
based on phase-mismatched second-harmonic generation (\textit{i.e.}, the
cascaded quadratic nonlinearity) in bulk quadratic nonlinear media. The
single-cycle propagation equations in the temporal domain including
higher-order nonlinear terms are presented. The balance between the quadratic
(SHG) and the cubic (Kerr) nonlinearity plays a crucial role: we define an
effective soliton number -- related to the difference between the SHG and the
Kerr soliton numbers -- and show that it has to be larger than unity for
successful pulse compression to take place. This requires that the phase
mismatch be below a critical level, which is high in a material where the
quadratic nonlinearity dominates over the cubic Kerr nonlinearity. Through
extensive numerical simulations we find dimensionless scaling laws, expressed
through the effective soliton number, which control the behaviour of the
compressed pulses. These laws hold in the stationary regime, in which
group-velocity mismatch effects are small, and they are similar to the ones
observed for fiber soliton compressors. The numerical simulations indicate that
clean compressed pulses below two optical cycles can be achieved in a
-barium borate crystal at appropriate wavelengths, even for picosecond
input pulses.Comment: 11 pages, 8 figures, resubmitted version, to appear in October issue
of J. Opt. Soc. Am. B. Substantially revised, updated mode
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