Broadband OPO spans the mid-IR, no tuning needed

• Published in: Laser focus world Vol. 48; no. 7; pp. 62 - 65
• Main Authors: Leindecker, Nick, Vodopyanov, Konstantin
• Format: Magazine Article
• Language: English
• Published: Tulsa Endeavor Business Media 01.07.2012
• Subjects: Bandwidth; Broadband; Gallium arsenide; Lasers; Optical Parametric Oscillators; Spectrum allocation; Tuning
• ISSN: 1043-8092

When used to synchronously pump our systems, the "comb" of modes of the NIR pump laser is rigorously translated into the mid-IR by phase- and frequency-locked downconversion, with extensive spectral broadening, a characteristic of doubly resonant degenerate OPOs.2 So far, we have demonstrated broadband mid-IR generation in a number of systems using both periodically poled lithium niobate (PPLN) and orientation-patterned gallium arsenide (OP-GaAs) as the nonlinear optical material, with pump sources including erbium-fiber (1.5 pm) thulium-fiber (2.05 pm) and CnZnSe (2.45 pm) modelocked lasers.3"5 In our most recent system (see Fig. 1), the pump laser is a Tm-fiber oscillator-amplifier system provided by IMRA America (Ann Arbor, MI) with 600 mW average power at a center wavelength of 2.05 pm. OP-GaAs crystal provides gain Broadband gain centered at 4.1 pm is provided by a 0.5-mmlong quasi-phase-matched (QPM) OP-GaAs crystal, grown at BAE Systems (Nashua, NH) by a combination of molecularbeam epitaxy and hydride vapor-phase epitaxy, resulting in a QPM "film" thickness of greater than 1 mm. The samples have a usable aperture of 1 ? 4 mm. The QPM period was 60.5 pm, which amounts to only eight domain reversal periods over the full length of the 0.5 mm crystal.