Unmanned aerial vehicle (UAV) reconnaissance is very stealthy and can break through enemy air defense system to conduct close-in reconnaissance. In particular, small and micro tactical UAVs are light in structure and have low requirements on operating environment. Besides, they are not afraid of casualties, flexible and highly intelligent in operational styles, and have derived many new combat methods and operational styles. Laser can effectively interfere or blind photoelectric sensor, is an important means to counter reconnaissance UAV. In this paper, laser damage research is carried out for typical reconnaissance UAVs, its weakness is analyzed, and the main methods of laser countermeasure reconnaissance UAVs are summarized.
Supercontinuum generation directly from a nonlinear fiber amplifier, especially from a nonlinear ytterbium-doped fiber amplifier, attracts more and more attention due to its all-fiber structure, high optical to optical conversion efficiency, and high power output potential. However, the modeling of supercontinuum generation from a nonlinear fiber amplifier has been rarely reported. In this paper, the modeling of a tapered Ytterbium-doped fiber amplifier for visible extended to infrared supercontinuum generation is proposed based on the combination of the laser rate equations and the generalized nonlinear Schrödinger equation. Ytterbium-doped fiber amplifier generally can not generate visible extended supercontinuum due to its pumping wavelength and zero-dispersion wavelength. However, appropriate tapering and four-wave mixing makes the visible extended supercontinuum generation from an ytterbium-doped fiber amplifier possible. Tapering makes the zero-dispersion wavelength of the ytterbium-doped fiber shift to the short wavelength and minimizes the dispersion matching. Four-wave mixing plays an important role in the visible spectrum generation. The influence of pulse width and pump power on the supercontinuum generation is calculated and analyzed. The simulation results imply that it is promising and possible to fabricate a visible-to-infrared supercontinuum with low pump power and flat spectrum by using the tapered ytterbium-doped fiber amplifier scheme as long as the related parameters are well-selected.
Supercontinuum has great potential in defense applications due to its wide spectrum, high coherence and high brightness, and it has attracted more and more attention across the world especially in the visible and mid-infrared region like 3-5μm which is the atmospheric transparency window. Higher power, wider spectrum, and better spectrum flatness will be the dominant pursuit for the future development of supercontinuum. Currently silica based fiber are the dominant host for visible to near-infrared supercontinuum generation, and soft glass like fluoride fiber, chalcogenide fiber and tellurite fiber are widely used for mid-infrared supercontinuum generation due to their lower loss in the mid-infrared region. In this paper, the generalized non-linear Schrödinger equation is used to simulate the visible to mid-infrared supercontinuum generation in a tellurite fiber. A femtosecond laser at 1064 nm worked as the pump source. 1.5 μm and 2 μm lasers are generally first pump candidates to generate mid-infrared supercontinuum in tellurite glass because the zero-dispersion wavelength of the tellurite glasses is around 2.15 μm. However, 1064 nm laser has more advantages in application in terms of cost, structure, and power scaling, so it is meaningful to investigate whether 1064 nm laser can pump tellurite fiber to generate supercontinuum with wide bandwidth. The simulation results show that 500 nm-5000 nm supercontinuum can be generated in a tellurite fiber with less than 10 kW peak power for the pump laser, and the length of the tellurite fiber is only several millimeter. The simulation results provide important guidance for future supercontinuum development.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.