Using the Variable Pump Intensity method to measure optical gains and unveil photophysical and photonic phenomena in active waveguides

Place: conference room. 

Abstract: 

The last decades have witnessed the advent of a myriad of new solution-processed laser materials that can be implemented as low-cost, flexible, and/or integrated waveguide devices. This profusion makes necessary the development of reliable methods to delineate all their amplifying signatures and thus to open the door to appropriate cross-sample comparisons. In this sense, the generation of Amplified Spontaneous Emission (ASE) is routinely used to assess the performance of active materials prior to developing thin film lasers. In particular, the Variable Stripe Length (VSL) method has been profusely used for decades to measure the optical gain in these materials and devices, but experimental and theoretical evidence casts doubts upon its reliability. Seeking to alleviate those problems, I recently developed a new formalism to fully characterize the amplification properties of active waveguides based on the most common Variable Pump Intensity (VPI) method. This novel methodology allows retrieving from the ASE spectra of a single VPI experiment, the spectrally resolved losses coefficient α(λ) and net optical gains g(λ) at all pump values, as well as objectively calculating the ASE threshold. In this seminar, I will revisit the main fundaments of the VPI method and its implementation into the freely distributed software ASE gain Labs, and will highlight the potential of this methodology to unveil relevant information on the photonic properties of the waveguiding devices (mode confinement effects, leaky-modes, ...) and on the photophysics of the active materials (excited state absorption, aggregates, ...).