Difference-frequency Generation Technique Research Articles

Confinement of generated terahertz waves between two metal surfaces by a nanowaveguide

In this study, a new nanowaveguide is designed and modeled. Light confinement by the nanowaveguide generates a 1-terahertz (THz) wave with narrow bandwidth. A difference-frequency generation (DFG) technique based on the nonlinear property of a gallium arsenide crystal is used in the model for generation of the THz wave. All calculations are based on the method of finite difference time domain. The feasible conditions of phase matching are evaluated, and the structural parameters of the nanowaveguide are optimized. It was found that the simultaneous use of two parallel plasmonic surfaces in the structure improves THz output power of the nanowaveguide in comparison with that of other similar waveguides. The nanowaveguide output power is several times larger than the output power of the other waveguides based on DFG technique in all scales.

Difference-frequency combs in cold atom physics

Optical frequency combs provide the clockwork to relate optical frequencies to radio frequencies. Hence, combs allow to measure optical frequencies with respect to a radio frequency where the accuracy is limited only by the reference signal. In order to provide a stable link between the radio and optical frequencies, the two parameters of the frequency comb must be fixed: the carrier envelope offset frequency $f_{\rm ceo}$ and the pulse repetition-rate $f_{\rm rep}$. We have developed the first optical frequency comb based on difference frequency generation (DFG) that eliminates $f_{\rm ceo}$ by design - specifically tailored for applications in cold atom physics. An $f_{\rm ceo}$-free spectrum at 1550 nm is generated from a super continuum spanning more than an optical octave. Established amplification and frequency conversion techniques based on reliable telecom fiber technology allow generation of multiple wavelength outputs. In this paper we discuss the frequency comb design, characterization, and optical frequency measurement of Sr Rydberg states. The DFG technique allows for a compact and robust, passively $f_{\rm ceo}$ stable frequency comb significantly improving reliability in practical applications.

High-power solid-state 4-μm laser based on Nd:YAG technology and difference-frequency generation

We present an analysis of difference-frequency generation techniques used to produce laser output in the 4-μm atmospheric window. A numerical model is developed for investigation of the mixing of 1.44- and 1.06-μm Nd:YAG lasers to produce 4.04-μm radiation in a LiNbO3 crystal. The results indicate that output energies of 40–50 mJ at 4.04 μm can be obtained from a realistic laser system.