Ultrafast Third-Order Nonlinear Optical Response Excited by fs Laser Pulses at 1550 nm in GaN Crystals.

Adrian Petris,Tudor Braniste,Petronela Gheorghe,Ion Tiginyanu

doi:10.3390/ma14123194

Abstract

The ultrafast third-order optical nonlinearity of c-plane GaN crystal, excited by ultrashort (fs) high-repetition-rate laser pulses at 1550 nm, wavelength important for optical communications, is investigated for the first time by optical third-harmonic generation in non-phase-matching conditions. As the thermo-optic effect that can arise in the sample by cumulative thermal effects induced by high-repetition-rate laser pulses cannot be responsible for the third-harmonic generation, the ultrafast nonlinear optical effect of solely electronic origin is the only one involved in this process. The third-order nonlinear optical susceptibility of GaN crystal responsible for the third-harmonic generation process, an important indicative parameter for the potential use of this material in ultrafast photonic functionalities, is determined.

Highlights

From the fitting of the experimental dependence I3ω (L) = f (I ω (0)) with a third grade polynomial, I3ω = CTHG · I ω 3, we determined the coefficient CTHG = I3ω /I ω 3, from the Equation (5) we calculated the third-order NL optical susceptibility corresponding to the third-harmonic generation (THG) process, χ(3), in the c-plane Gallium nitride (GaN) crystal
The fastest third-order optical nonlinearity of solely electronic origin was measured for the first time, to the best of our knowledge, in c-plane GaN crystal by the thirdharmonic generation excited by high-repetition-rate ultrashort laser pulses at the telecommunications wavelength of 1550 nm
The very low average power of the third harmonic beam generated in GaN (~pW) in non-phase-matching conditions was measured by image processing, following a method recently introduced by us for the use of a common camera as an ultrasensitive power-meter

Summary

Introduction

Gallium nitride (GaN) is a III-V semiconductor with properties that make it an excellent material for high-power, high-voltage, high-frequency electronics [1,2,3]. It is an important material for electro-optic and integrated-photonic devices [4]. GaN possesses a large transparency, covering the visible and the near and mid infrared spectral domains [8]. It is chemically stable, has a high optical damage threshold, a weak material dispersion, and a low thermo-optic coefficient [9]. Electromagnetic interference shielding in an ultra-broad range of frequencies, distributed Bragg reflectors and UV-light driven fluorescent microengines are among the emergent applications of this compound when engineered in three-dimensional nanoarchitectures [10,11,12,13,14,15]

Methods

Results

Conclusion