Mathieu Charbonneau-Lefort

Optical parametric amplifiers using chirped quasi-phase-matching gratings I: practical design formulas

Optical parametric amplifiers using chirped quasi-phase-matching (QPM) gratings offer the possibility of engineering the gain and group delay spectra. We give practical formulas for the design of such amplifiers. We consider linearly chirped QPM gratings providing constant gain over a broad bandwidth, sinusoidally modulated profiles for selective frequency amplification and a pair of QPM gratings working in tandem to ensure constant gain and constant group delay at the same time across the spectrum. The analysis is carried out in the frequency domain using Wentzel-Kramers-Brillouin analysis.

Tandem chirped quasi-phase-matching grating optical parametric amplifier design for simultaneous group delay and gain control

We present a broadband optical parametric amplifier design using tapered gain and tandem chirped quasi-phase-matching gratings to obtain flat gain and group-delay spectra suitable for applications such as ultrashort-pulse amplification and fiber-optic communication systems. Although a tapered-gain amplifier consisting of a single chirped grating can provide constant gain over a wide frequency range, it cannot be used to control the group delay across the spectrum. We propose controlling both the gain and the group delay profiles using a two-stage amplifier configuration, in which the idler of the first is used as the input signal of the second.

Competing collinear and noncollinear interactions in chirped quasi-phase-matched optical parametric amplifiers

Chirped quasi-phase-matched optical parametric amplifiers (chirped QPM OPAs) are investigated experimentally. The measured collinear gain is constant over a broad bandwidth, which makes these devices attractive candidates for use in femtosecond amplifier systems. The experiment also shows that chirped QPM OPAs support noncollinear gain-guided modes. These modes can dominate the desired collinear gain and generate intense parametric fluorescence. Design guidelines to mitigate these parasitic processes are discussed.

Broadband quasi-phase-matched second-harmonic generation of ultrashort optical pulses with spectral angular dispersion

Noncollinear quasi-phase matching, in combination with spectral angular dispersion, can be used to broaden the bandwidth of second-harmonic generation (SHG) beyond the bandwidth for collinear, nondispersed interactions. A general theoretical treatment is presented, in addition to a solution that predicts the generated field for the case of a Gaussian input field; a comparison is made between this technique and others available for broadband SHG. An experiment in periodically poled lithium niobate demonstrates SHG of a 138 fs pulse at 1550 nm in a 1 cm length crystal (with a collinear acceptance bandwidth 13 times narrower than the first-harmonic bandwidth) with minimal spectral narrowing.

Theory and simulation of gain-guided noncollinear modes in chirped quasi-phase-matched optical parametric amplifiers

Chirped quasi-phase-matched (QPM) gratings offer essentially constant gain over wide bandwidths, making them promising candidates for short-pulse optical parametric amplifiers. However, we discovered that high-gain noncollinear processes can compete with the desired broadband gain of such amplifiers. Here, we investigate these noncollinear gain-guided modes both numerically and analytically, including longitudinal nonuniformity of the phase-matching profile, lateral localization of the pump beam, and the noncollinear propagation of the interacting waves.

Broadband optical parametric amplifier using chirped quasi-phase-matched gratings

We demonstrate operation of an optical parametric amplifier using a chirped quasi-phase-matching grating. Such devices enable engineering of gain spectra over wide bandwidths, applicable to femtosecond pulse amplification and other wide-band devices.

Variational and WKB Descriptions of Laterally Localized Eigenmodes in Non-Collinear Optical Parametric Amplifiers

With a finite lateral width pump, non-collinear interactions result in metastable or stable laterally localized bound states. The physical processes involved are group velocity walk-off, diffraction, chirped QPM gratings and different pump shapes.

Gain Enhancement Due to Transverse Effects in Chirped Quasi-Phase-Matched Optical Parametric Amplifiers

We investigate transverse effects in chirped QPM gratings such as cascaded phase shifts and non-collinear interactions. We find enhanced growth over a wide bandwidth with gains much larger than in the 1D limit.

Ultra-broadband second-harmonic generation using spectral angular dispersion in quasi-phase-matched nonlinear materials

We demonstrate the use of spectral angular dispersion in quasi-phase-matched second-harmonic generation (SHG) of 138 fs pulse at 1550 nm in a 1-cm-long crystal of periodically-poled lithium niobate (collinear acceptance bandwidth 13 times narrower than the first-harmonic bandwidth) with minimal spectral narrowing. In addition, we discuss the unique potential of quasi-phase-matched nonlinear materials in noncollinear SHG, and compare this technique to other methods for broadband frequency conversion.