Upconversion of optical signals with multi-longitudinal-mode pump lasers

TL;DR

This paper presents a semi-classical model showing that fluctuations in multi-longitudinal-mode pump lasers limit optical frequency conversion efficiency, supported by experimental results achieving 70% efficiency in lithium niobate waveguides.

Contribution

The study introduces a theoretical model for multimode pump laser frequency conversion and experimentally demonstrates its limitations and potential applications.

Findings

Fluctuations in pump power reduce conversion efficiency.

Maximum observed efficiency was 70%.

Multimode pumping is less stable than single-mode for high-efficiency conversion.

Abstract

Multi-longitudinal-mode lasers have been believed to be good candidates as pump sources for optical frequency conversion. However, we present a semi-classical model for frequency conversion of optical signals with a multimode pump laser, which shows that fluctuations of the instantaneous pump power limit the conversion efficiency. In an experiment, we upconverted a 1550 nm optical signal in a periodically poled lithium niobate waveguide using with a multi-longitudinal-mode laser, an observed a maximum conversion efficiency of 70%, in good agreement with our theoretical model. Compared to single-mode pumping, multimode pumping is not a suitable technique for attaining stable near-unity-efficiency frequency conversion. However, the results obtained here could find application in characterization of the spectral or temporal structure of multi-longitudinal-mode lasers.