Femtosecond seeded 150 nm-bandwidth optical parametric amplifier for active imaging applications at 1550 nm

Karl A. Tillman; Derryck T. Reid

doi:10.1117/12.630687

7 November 2005 Femtosecond seeded 150 nm-bandwidth optical parametric amplifier for active imaging applications at 1550 nm

Karl A. Tillman, Derryck T. Reid

Author Affiliations +

Proceedings Volume 5989, Technologies for Optical Countermeasures II; Femtosecond Phenomena II; and Passive Millimetre-Wave and Terahertz Imaging II; 59890R (2005) https://doi.org/10.1117/12.630687
Event: European Symposium on Optics and Photonics for Defence and Security, 2005, Bruges, Belgium

Abstract

Laser ranging and burst illumination imaging (BIL) in the atmospheric transmission window at 1.5μm are made difficult by speckle effects which are observed when a rough surface is illuminated by a laser beam with a coherence length greater than the characteristic surface feature size. For the narrowband pulsed lasers currently used, this length is of the order of a few millimetres which leads to observable speckle effects for many common surfaces. In this context we describe progress towards the development a short-coherence length laser source operating at 1.5μm and based on optical parametric amplification of broadband seed pulses from a modelocked femtosecond erbium-doped fibre laser. Our optical parametric amplifier (OPA) system comprises a compact actively Q-switched 1047nm Nd:YLF laser, operating at ~1kHz repetition frequency, to which a 54MHz femtosecond 1.55μm Er:fibre laser is synchronised. The fibre laser produces bandwidth-limited 100fs pulses which are stretched by chromatic dispersion in a spool of SMF28 fibre to match the 3.5ns duration of the Q-switched pulses. Pulses from the Nd:YLF and Er:fibre lasers act as the pump and seed respectively for an OPA based on an aperiodically-poled crystal of MgO:PPLN containing a single linearly chirped grating. The chirp grating enables broadband parametric amplification across a wavelength range comparable with the spectral bandwidth of the seed pulses, amounting to ~150nm in the wings of the spectrum. Early results from this system have demonstrated output energies of 2.55μJ and a single-pass gain ~51dB and are expected to be increased with continued development of the project.

Citation Download Citation

Karl A. Tillman and Derryck T. Reid "Femtosecond seeded 150 nm-bandwidth optical parametric amplifier for active imaging applications at 1550 nm", Proc. SPIE 5989, Technologies for Optical Countermeasures II; Femtosecond Phenomena II; and Passive Millimetre-Wave and Terahertz Imaging II, 59890R (7 November 2005); https://doi.org/10.1117/12.630687

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