Title of Paper: Robust, Single-Frequency Ring Oscillator

Principal Author: Dr. Floyd Hovis

Abstract: The Earth Science Enterprise Capability Matrix identifies space-based ozone differential absorption lidar (DIAL) as a high priority instrument in need of technology development. A critical component of the ozone DIAL system is a space-qualified 1Ám pump source that provides single frequency, high energy, and high beam quality pulses in a dual-pulse format. These pump requirements maximize conversion efficiency and minimize the risk of damage for the nonlinear processes used in the UV laser. Although 1Ám laboratory lasers can achieve the desired output, the technologies on which these lasers are based are not compatible with the requirement to operate in space. Common shortcomings include the inability to survive the vibrational environment of a launch, sensitivity to thermal variations, and liquid-based cooling for heat removal. The overall objective of our ESTO funded research is the demonstration of 1 Ám laser technology that is space-qualifiable and capable of achieving the following characteristics:

  1. >1 J single frequency pulses in a dual-pulse format
  2. True wall plug efficiencies of 10% electrical-to-optical
  3. Reduced package size and weight
  4. Conductively cooled
  5. Diode pumped

Our presentation will focus on the first phase of our ATIP sponsored work in which we built and characterized an innovative unstable ring oscillator that achieves both single-frequency operation and mechanical robustness. The ring design is an extension of unstable linear cavity designs developed and delivered in other Fibertek laser systems. It incorporates a diode-pumped, conductively cooled, zig-zag slab head. We will describe the design details that allowed us to achieve the following performance from the ring oscillator.

  1. >100 mJ/pulse of single frequency 1Ám output in dual pulse format at 10 Hz
  2. M2 < 1.5 in non-zigzag plane
  3. M2 < 2.5 in zigzag plane
  4. Unidirectional operation without feedback mirrors or Faraday rotators

< 5% energy loss for 500 Árad misalignment