Efficient Octave Sapnning Super-continuum Generation from Novel Ta2O5 Nonlinear Waveguide

Chao-Kuei Lee^1*

¹Department of Photonics, National Sun Yat-sen University, Kaohsiung, Taiwan

* Presenter:Chao-Kuei Lee, email:chuckcklee@yahoo.com

Supercontinuum generation (SCG) represents the generation of ultra-broadband optical spectrum by injecting a short pulse into a nonlinear optical material. SCG involves complex nonlinear optical processes related to c of nonlinear medium, including self-phase modulation (SPM), crossphase modulation (XPM), four-wave-mixing (FWM), soliton fission, Raman self-frequency shift, and dispersive wave generation. Such broadband optical spectrum shows great optical coherence within the full optical bandwidth and can be utilized in frequency metrology, optical coherence tomography, coherent Raman and anti-stokes Raman spectroscopy. For application in optical communication, a SCG spectrum can offer high power and coherent multi-channel light sources by spectrally sliced the broadband spectrum by using the wavelength division multiplexing (WDM) systems. With such configuration, one pulse laser source can replace lots of semiconductor lasers and no need of precisely controlling the temperature as well as polarization within several laser sources.
In this work, anomalous dispersion Ta2O5 based waveguide was designed for SCG due to its nature of two photon absorption free and high optical nonlinearity. The e-beam lithography and reactive ion etching are utilized to fabricate the waveguide structure. A 5mm length air cladding Ta2O5 waveguide with dimension of 800nm x 700nm was fabricated for fulfilling anomalous dispersion requirement which is crucial for SCG. By injecting a 100-fs pulse laser at central wavelength of 1-um, the output spectrum of Ta2O5 waveguide shows an octave spanning (at -30dB). For excitation laser wavelength of 1056nm, with excitation peak power of around 400W, the 1.5 octave spanning was demonstrated. In addition, the SCG from various dimension Ta2O5 waveguide was investigated and discussed. Beside the air-cladding structure, the SCG from Ta2O5 higher order mode channel waveguide will be discussed in the talk as well. Our primary result shows that Ta2O5 has great potential in developing visible to infrared broadband light source, which can be applied in optical coherence tomography and frequency metrology

Keywords: Supercontinuum generation, Si Photonics, Comb, nonlinear waveguide