Home RISTRA OPO Demonstrated Performance
RISTRA Demonstrated Performance

RISTRA can produce highly symmetric beams of high quality, even with a very high Fresnel number - a common culprit of poor beam quality in other OPOs.

Our OPO can also very efficiently produce high quality beams. A 90% pump depletion with RISTRA, using pulsed pump seeding and a flat-topped spatial profile with a pump beam of 803 nm and cavity Fresnel number of around 400 was achieved in Armstrong and Smith (2006) [2]. The careful selection of operating parameters enabled the RISTRA to produce a signal beam with RMS fluctuation of ≤ 2.5 μrad of horizontal and vertical tilt (or < 1% of the diffraction limit), while 60% of the signal beam's far-field energy fell within the first Airy null (where 84% would be ideal).

The superior beam quality produced by RISTRA is demonstrated in Smith and Armstrong (2002) [1]. Figure 1 shows a comparison between the fluence profiles of an image-inverting 3-mirror ring cavity OPO and the RISTRA, both pumped at 4 times the threshold using a large-diameter pump beam and injection seeding, with the idler beam parallel to the Poynting vector.

RISTRA produces the highest quality resonated signal beam when both the pump laser and OPO are seeded, the pulse duration is 10-15 ns, the OPO is pumped at two or three times threshold, and the pump and idler Poynting vectors are parallel. The most efficient conversion occurs when the spatial profile is flat topped. Use our free model for optimizing your conditions.

Less complicated and costly setups can still produce acceptable results, outperforming more conventional OPOs. In Dergachev et al. (2007) [3], a Thulium fiber laser driving a Ho:YLF laser cavity (2.05 μm) pumped a mid-IR ZGP crystal with Gaussian spatial profile, and no injection seeding, to produce a clean 3.4 μm signal beam. The signal beam had an approximate M2 value of 1.8, and the pump pulse energy of 55 mJ produced 10 mJ signal output.

 

Fluence Profile: 3 Mirror Ring vs. RISTRA

Figure 1: Far-field fluence profile of (a) an image-inverting 3 mirror ring and (b) RISTRA. Both were pumped at 4 times the threshold with a large-diameter pump beam and were injection seeded, with parallel pump and idler Poynting vectors. The contours are exponentially spaced, such that the lowest contour is at 0.01 of the maximum fluence, and each contour is at 1.31 times the previous. The highest contour corresponds to 0.88 of the maximum fluence. From [1].

 

References
  1. A. V. Smith and D. J. Armstrong, “Nanosecond optical parametric oscillator with 90° image rotation: design and performance,” J. Opt. Soc. Am. B 19, 1801-1814 (2002).
  2. D. J. Armstrong and A. V. Smith, “90% pump depletion and good beam quality in a pulse-injection-seeded nanosecond optical parametric oscillator,” Opt. Lett. 31, 380-382 (2006).
  3. A. Dergachev, D.J. Armstrong, A.V. Smith, T. Drake and M. Dubois, “3.4-μm ZGP RISTRA nanosecond optical parametric oscillator pumped by a 2.05-μm Ho:YLF MOPA system,” Opt. Exp 15, 14404-14413 (2007).
  4. D. J. Armstrong and A. V. Smith, “Demonstration of improved beam quality in an image-rotating optical parametric oscillator,” Opt. Lett. 27, 40-42 (2002).
  5. D. J. Armstrong and A. V. Smith, “All Solid-State High-Efficiency Tunable UV Source for Airborne or Satellite-Based Ozone DIAL Systems,” IEEE J. Select Top. Quant. Electron. 13, 721-731 (2007).