33 W Average-Power Optical Parametric Oscillator

Mark S. Webb, Glen A. Rines1), Henry H. Zenzie2), Tom S. Kaffenberger, and Peter F. Moulton3)

Schwartz Electro-Optics, Aerospace Sensors Division

3404 North Orange Blossom Trail Rd., Orlando, FL 32804

Jeffrey J. Kasinski and Ralph L. Burnham

Fibertek Inc., 510 Herndon Parkway, Herndon, VA 22070

  1. Currently with: IR Sources, 28 Old Milford Rd., Brookline, NH 03033
  2. Currently with: Palomar Medical Technologies, 66 Cherry Hill Drive, Beverly, MA 01915
  3. Schwartz Electro-Optics, Research Division, 45 Winthrop St., Concord, MA 01742

 

Abstract

We present the development of a 33 W eye-safe OPO utilizing KTA crystals and a ring resonator cavity. A 130 W multi-mode near flat-top diode pumped Nd:YAG laser operating at 100 Hz provides 107 W of pump power to the OPO.

 

We report the development of, to the best of our knowledge, the highest-average-power optical parametric oscillator (OPO) yet demonstrated. A 130 W, 100-Hz Nd:YAG diode-pumped solid state laser operating at 1064 nm serves as the pump source for a non-critically phase-matched OPO utilizing multiple KTA nonlinear crystals. After isolation and transfer optics, a 107 W of pump light is available at the OPO input. A maximum 33 W of signal power is extracted from the OPO at a measured wavelength of 1534.7 nm and a measured bandwidth of 0.6 nm. We determined that the beam quality parameter, M2, for the signal beam was 40.

The pump laser is a diode-pumped Nd:YAG rod Master Oscillator - Power Amplifier (MOPA) system operating at 100 Hz, which utilizes a crossed-porro multimode resonator and two stages of amplification to obtain 1.3 J (130W) at 1.06 mm in a military-hardened package; thermal distortion is compensated with aspheric elements as described previously[1]. The pump laser is both spatially and longitudinally multi-mode, and the output pulse has a Gaussian-like temporal profile with a 16.4 ns FWHM duration. The output beam has a near flat-top spatial profile with a 0.8-cm beam diameter and a measured M2 of 5.

The OPO configuration is shown in Figure 1. In contrast to previous high-energy OPO designs [2], we utilized a ring OPO configuration with TIR prism. In addition, we employ KTA instead of KTP to minimize thermal effects in the nonlinear crystals due to absorption of the idler beam at 3469 nm. Figure 2 shows the OPO signal power output as a function of pump laser power input. We experimentally determined that 30% was the optimal output coupling reflectivity for the signal wavelength. The total round-trip cavity length (physical not optical) is 52.2 cm. For experimental convenience we did not bond the crystals onto a thermal heat sink. Therefore, we expect better results when thermal management is incorporated into the OPO design.

Figure 1 - TIR Ring OPO configuration.

Figure 2 - OPO signal output power vs. pump laser input power.

 

References:

  1. J. Kasinski and R. Burnham, Near-diffraction-limited, high-energy, high-power, diode-pumped laser using thermal aberration correction with aspheric diamond-turned optics, Appl. Optics, Vol. 35, pp: 5949 - 5954, 1996.
  2. G. A. Rines, D.M. Rines and P. F. Moulton, CLEO ’93 Postdeadline Paper CDP16.

Ackowledgements:

This work was performed under contract to Chemical and Biological Defense Command, Aberdeen Proving Grounds, Edgewood Area. Excellent technical support was provided by Gail Scott of Winchester Design Engineering, and Elias Fakhoury of Fibertek.

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