Compact high-power eye safe fiber laser for LADAR

Abstract

We report on an eye safe fiber laser generating >5 Watts of average power at 50 kHz packaged in a cylinder measuring 6" in diameter and 3.75" in length to show compatibility with advanced seeker concepts. To our knowledge, this represents the highest average power per unit volume from an eye safe pulsed fiber laser generating multi-Watts of average power.Keywords: high power, eye safe, fiber laser, advanced seeker, LADAR IntroductionCompact, efficient, and cost effective short pulse laser sources that emit radiation in the eye safe wavelength region are required for imaging laser radar (LADAR) systems under development in the DoD. Conventional eye safe laser sources using diode-pumped solid-state laser (DPSSL) and optical parametric oscillator (OPO) technologies are too large, inefficient, and unreliable to be deployed on future autonomously-guided ground and air platforms. It has been demonstrated that pulsed eye safe fiber laser sources provide critical performance advantages for LADAR systems because they can generate short pulses (<10 ns) at high repetition rates (>20 kHz) that enable increased range resolution and rapid data collection, all in a very compact and robust package compared to other laser technologies [1]. Fiberbased laser transmitters also leverage known benefits of fiber-based sources for field deployment, which include high efficiency, small footprint, flexible form factor for packaging and the elimination of large bulk optics and their associated alignment / stability challenges.In this paper, we report a novel pulsed eye safe fiber-based laser transmitter in a package suitable for LADAR seekers in advanced munitions. It is packaged in a cylinder measuring 6" in diameter and 3.75" in length (106 cubic inches) and generates over 5 Watts of average power at a repetition rate of 50 kHz. The following section describes the laser architecture and the mechanical packaging of the unit. The final section shows the units performance at repetition rates of 20 and 50 kHz. This work represents the highest average power per unit volume from a Watt-level eye safe pulsed fiber-based laser and demonstrates the flexible, modular packaging possible when using a fiber laser transmitter.

1550 nm, (1-5) ns, (0.2-2) MHz, kW-Peak Power, Pulsed All-Fiber MOPA Source

“…Q-switched bulk [5] and fiber lasers [6], external modulated or direct modulated semiconductor lasers [7][8] can be used as seed sources. In case of Q-switched lasers it is impossible to adjust independently pulse parameters like duration and repetition rate, which results from the fact that each change of a repetition rate implies the change of pulse width.…”

Highly efficient, kW peak power, 1.55 µm all-fiber MOPA system with a diffraction-limited laser output beam

“…Pulsed laser sources operating in the ''eye-safe'' (k [1.4 lm) spectral range are desired for numerous applications, like remote sensing, range finding, material processing, area mapping, or mid-infrared super continuum generation [1][2][3][4]. Most of these applications require optical pulses of short duration, usually on the nanosecond-scale and with kW-level peak power.…”