Ultrafast Frequency Conversion Research Articles

Demonstration of coherent time-frequency Schmidt mode selection using dispersion-engineered frequency conversion

Time-frequency Schmidt (TFS) modes of ultrafast quantum states are naturally compatible with high bit-rate integrated quantum communication networks. Thus they offer an attractive alternative for the realization of high dimensional quantum optics. Here, we present a quantum pulse gate based on dispersion-engineered ultrafast frequency conversion in a nonlinear optical waveguide, which is a key element for harnessing the potential of TFS modes. We experimentally retrieve the modal spectral-temporal structure of our device and demonstrate a single-mode operation fidelity of 80\%, which is limited by experimental shortcomings. In addition, we retrieve a conversion efficiency of 87.7\% with a high signal-to-noise ratio of 8.8 when operating the quantum pulse gate at the single-photon level.

Yb-Fiber-Laser-Pumped Ultrafast Frequency Conversion Sources From the Mid-Infrared to the Ultraviolet

We describe the development of versatile, practical, and high-power ultrafast optical sources based on second-order nonlinear frequency conversion in bulk materials pumped by the mode-locked Yb-fiber laser at 1064 nm, and covering spectral regions from the near- to mid-infrared (mid-IR) to the visible and ultraviolet (UV). By exploiting synchronously-pumped optical parametric oscillators (SPOPOs) based on quasi-phase-matched nonlinear materials of MgO:PPLN and MgO:sPPLT, in combination with internal and external single-pass harmonic generation in birefringent crystals of BiB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> and β-BaB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , we have generated tunable picosecond pulses in spectral regions from above ~4 μm in the mid-IR, into the visible, and down to 317 nm in the UV. The demonstrated sources can deliver average output powers of up to 11.7 W in the near- to mid-IR, 3.5 W in the visible, and 30 mW in the UV, in picosecond pulses at ~80 MHz repetition rate, with high passive stability, excellent output characteristics, and the potential for further power scaling with increased fiber laser pump power. The described sources represent an effective approach for the extension of fiber laser technology across the entire wavelength range from the UV to mid-IR spectrum, and ultimately the THz spectral range.

Soliton dynamics in velocity matched ultrafast frequency conversion processes

We consider ultrafast second order frequency conversion processes, under group velocity matching conditions. The three wave interaction equations, describing velocity matched ultrafast optical frequency conversion processes, can be reduced to Sine-Gordon equation. In this way, the well known Sine-Gordon solitons can be mapped into three wave soliton solutions. Here, we report the numerical dynamics of three wave simultons, two-solitons and breathers in ultrafast second order frequency conversion processes.

Femtosecond nonlinear frequency conversion based on BiB3O6

AbstractWe review the physical properties, linear and nonlinear optical characteristics, and phase‐matching configurations of BiB3O6 (BIBO), the first low‐symmetry (monoclinic) inorganic nonlinear crystal that has found broad applications for frequency conversion of laser sources from the UV, across the visible, to the near‐IR based on three‐wave interactions. We describe in detail the most relevant optical properties that make this material an attractive candidate for nonlinear frequency conversion of laser light in general, and ultrafast femtosecond laser sources in particular. With special focus on ultrafast frequency conversion, characteristics such as group‐velocity mismatch and spectral acceptance, parametric gain bandwidth, group‐velocity dispersion, as well as angular acceptance and spatial walk‐off are evaluated and optimum configurations for the attainment of maximum conversion efficiency, minimum pulse duration, and highest spatial beam quality are identified and compared with the most widely established alternative borate crystal, β‐BaB2O4. Experimental results are presented on both parametric up‐ and down‐conversion of femtosecond pulses, from the high‐energy, low‐repetition‐rate (1 kHz) to the low‐energy, high‐repetition‐rate (56–76 MHz) regime, demonstrating the unique versatility of BIBO for efficient frequency conversion of femtosecond pulses with broad tunability from 250 nm in the UV, throughout the visible, up to ∼ 3000 nm in the IR.