Development of PPLN waveguides for IR upconversion detection and imaging

Abstract

This thesis contains a series of experimental and numerical simulation work carried out for development of zinc-indiffused PPLN ridge waveguides at a range of wavelengths, spanning UV, visible and infrared light. First, the methodology for the characterisation and modelling of PPLN ridge waveguides is presented. The waveguides are fabricated via indiffusion of zinc into the crystal structure and ductile dicing, thus to create a good numerical model which will allow us to predict waveguide parameters for new wavelengths, an investigation of fabrication parameters is carried out.

Results for fabricated frequency doubling PPLN waveguides into the green/UV range are also presented. Preliminary results of the most efficient waveguides fabricated yielded a maximum conversion efficiency of 100.1%/W in a 20mm-long device, generating 532nm light, and in a different 20mm-long device, generating 378.3nm light with a 3.65%/W conversion efficiency. Experimental phasematching spectra and mode profile measurements are compared to those generated by the model. Numerical modelling of the effect of width variation along the length of the waveguide is carried out, as it is known to reduce efficiency.

Initial work towards building the existing model for MIR waveguides is presented. In optical experiments the fabricated MIR PPLN waveguides showed guidance up to 3.5μm in a 45μm wide ridge, and upconversion detection of pulsed 3.3μm light is achieved, generating 805nm light with a conversion efficiency of 0.11%.

An upconversion imaging system is built to demonstrate an application use for long wavelength zinc-indiffused PPLN waveguides developed during this thesis. The configuration uses Galvo mirrors to scan over an illuminated area, the collected light is coupled into a waveguide and upconverted to visible wavelengths for detection.

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Identifiers

ORCID for Noelia Palomar Davidson: orcid.org/0000-0002-6413-5858

ORCID for Peter G.R. Smith: orcid.org/0000-0003-0319-718X

ORCID for Corin Gawith: orcid.org/0000-0002-3502-3558

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