We report a study of the effect of optical absorption on generation of coherent infrared radiation from mid-IR to THz region from GaSe crystal. The infrared-active modes of epsilon-GaSe crystal at 236 cm(-1) and 214 cm(-1) were found to be responsible for the observed optical dispersion and infrared absorption edge. Based upon phase matching characteristics of GaSe for difference-frequency gene...

We present a comprehensive study of second-order nonlinear difference frequency generation in triply resonant cavities using a theoretical framework based on coupled-mode theory. We show that optimal "quantum-limited" conversion efficiency can be achieved at any pump power when the powers at the pump and idler frequencies satisfy a critical relationship. We demonstrate the existence of a broad ...

Abstract We propose and numerically investigate integrated photonic crystal waveguides (PhC-WGs) formed in a semiconductor slab to realize an ultrasmall highly efficient terahertz (THz) wave source. The structure consists of straight PhC-WG with low-group-velocity low-dispersion (LVLD) for difference frequency generation (DFG) connected two PhC-WGs introduce fundamental lights into the LVLD PhC...

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generated mid-IR at 3 microns with a powers of ~2.5 microW and a spectral line...

We report on an improvement of idler beam quality in a singly resonant optical parametric oscillator (OPO), where the resonant signal is converted to the idler via an additional difference frequency generation (DFG) process. The two processes are phase matched simultaneously by a quasi-periodically poled nonlinear crystal. Whereas back-conversion of the signal and idler to the pump frequency di...

Cross-correlation frequency-resolved optical gating (XFROG) based on four-wave mixing (FWM) in a gas medium is shown to enable dispersion-free characterization of few-cycle mid-infrared (mid-IR) pulses tunable within a spectral range of more than two octaves. The FWMXFROG technique is used to measure spectra and pulse shapes, as well as to retrieve the phase of a few-cycle output of difference-...

A one-week in situ intercomparison campaign was completed on the Rice University campus for measuring HCHO using three different techniques, including a novel optical sensor based on difference frequency generation (DFG) operating at room temperature. Two chemical derivatization methods, 2,4-dinitrophenylhydrazine (DNPH) and o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA), were deployed d...

Abstract We explore background-free options to detect mid-infrared (MIR) electric transients. The MIR field and a near-infrared probe interact via sum- (SFG) difference-frequency generation (DFG) in an electro-optic crystal. An intuitive picture based on phasor representation rigorous numerical calculations are used for analysis. It turns out that separating photons generated either by SFG or D...

We report the experimental demonstration of all-optical format conversion by exploiting the cascaded second-harmonic generation and difference-frequency generation (cSHG/DFG) in a periodically poled lithium niobate (PPLN) waveguide assisted by the reflective semiconductor optical amplifier (RSOA)-based active mode-locking. 10 and 20 Gbit/s format conversions from non-return-to-zero (NRZ) to ret...

We use the combination of ultrafast gating and high parametric gain available with Difference-Frequency Generation (DFG) and Optical Parametric Amplification (OPA) to achieve the complete measurement of ultraweak ultrashort light pulses. Specifically, spectrally resolving such an amplified gated pulse vs. relative delay yields the complete pulse intensity and phase vs. time. This technique is a...