Parametric oscillator directly pumped by a 1.55-mum erbium-fiber laser

Single-step sub-200 fs mid-infrared generation from an optical parametric oscillator synchronously pumped by an erbium fiber laser

We demonstrate the single-step generation of mid-infrared femtosecond laser pulses in a AgGaSe₂ optical parametric oscillator that is synchronously pumped by a 100 MHz repetition rate sub-90 fs erbium fiber laser. The tuning range of the idler beam in principle covers ∼3.5 to 17 μm, only dependent on the choice of cavity and mirror design. As an example, we experimentally demonstrate idler pulse generation from 4.8 to 6.0 μm optimized for selective vibrational resonant molecular spectroscopy. We find an oscillation threshold as low as 150 mW of pump power. At 300 mW pump power and a central wavelength of ∼5.0  μm, we achieve an average infrared power of up to 17.5 mW, with a photon conversion efficiency of ∼18%. A pulse duration of ∼180  fs is determined from a nonlinear cross-correlation with residual pump light. The single-step nonlinear conversion leads to a high power stability with <1% average power drift at <0.5%  rms noise over 1 h.

Highly efficient tunable mid-infrared optical parametric oscillator pumped by a wavelength locked, Q-switched Er:YAG laser

A highly efficient and stable mid-infrared optical parametric oscillator is demonstrated, pumped by an electro-optic Q-switched Er:YAG laser with operating wavelength locked at 1645 nm by a volume Bragg grating. The oscillator, based on MgO-doped periodically poled lithium niobate (MgO:PPLN) crystal, yields a maximum overall average output power in excess of 1 W, corresponding to a conversion efficiency of 35.5% and a slope efficiency of 43.6%. The signal and idler wavelengths of the OPO are around ~2.7 μm and ~4.3 μm, respectively, corresponding to the two peak absorption bands of CO(2). Lasing characteristics of the oscillator, including the time evolution of the pump, signal and idler pulses at different pump power levels, are also investigated. Temperature tuning of the MgO:PPLN crystal gives signal and idler ranges of 2.67 to 2.72 μm and 4.17 to 4.31 μm, respectively.

Efficient all-solid-state mid-infrared optical parametric oscillator based on resonantly pumped 1.645 μm Er:YAG laser

We first report an all-solid-state tunable mid-infrared singly resonant optical parametric oscillator based on a 1532 nm laser diode resonantly pumped, Q-switched 1.645 μm Er:YAG laser. An MgO-doped periodically poled lithium niobate was used as the nonlinear material. At the pulse repetition frequency of 2 KHz, a maximum overall average output power of 0.95 W with pump power of 2.8 W was achieved, corresponding to a conversion efficiency of 34% and a slope efficiency of 38%. The temperature tuning was performed giving signal and idler ranges of 2.67 to 2.71 μm and 4.18 to 4.31 μm, respectively.

Mid-infrared optical parametric oscillator synchronously pumped by an erbium-doped fiber laser

A mid-infrared synchronously pumped optical parametric oscillator pumped by a femtosecond erbium-doped fiber laser is demonstrated and characterised. The idler is tunable from 3.7-4.7 μm, with a maximum average power of 37 mW and a pulse length of ∼ 480 fs at 4 μm. We compare the experimental results with numerical results based on an extensive simulation model.

Watt-level, high-repetition-rate, mid-infrared pulses generated by wavelength conversion of an eye-safe fiber source

We report on a mid-infrared (mid-IR) source consisting of an approximately 10 W average-power, linearly polarized 1.54 microm wavelength pulsed fiber source pumping an optical parametric oscillator. From this source, we obtained average power in excess of 1 W in the 3.8-4.0 microm wavelength range at a pulse repetition frequency of 100 kHz. With a slightly different setup, we also achieved an average power of 0.25 W at 4.5 microm wavelength. To our knowledge, these values represent the highest mid-IR power obtained through wavelength conversion of an eye-safe fiber source.

Direct ultraviolet writing of channel waveguides in congruent lithium niobate single crystals

We report the fabrication of optical channel waveguides in congruent lithium niobate single crystals by direct writing with continuous-wave ultraviolet frequency-doubled Ar+ laser radiation (244 nm). The properties and performance of such waveguides are investigated, and first results are presented.

Polarization-maintaining, double-clad fiber amplifier employing externally applied stress-induced birefringence

We report a new approach to obtaining linear-polarization operation of a rare-earth-doped fiber amplifier in which the gain fiber is coiled under tension to induce birefringence. We demonstrated this method by constructing an Er/Yb-doped, double-clad, single-mode fiber amplifier with an output power of 530 mW and a polarization extinction ratio of >17 dB (when seeded with linearly polarized light) at a wavelength of ~1.5 microm . The technique is achromatic, permits single- or multiple-pass operation of the amplifier, requires no additional components in the optical path, leaves the fiber ends unobstructed, and is inexpensive to implement.