Background-free quasi-steady-state photoinduced absorption spectroscopy by dual optical modulation

• DOI: 10.48550/arxiv.1007.3035
• Publication Date: 2010-01-01
• Authors: Houssem Kallel; Gianluca Latini; Francis Paquin; R. Rinfret; Natalie Stingelin; Carlos Silva
• Keywords: Chopper; Monochromatic color

We present a simple and inexpensive means to measure background-free photoinduced absorption spectra by implementing dual optical modulation scheme. Our objective is quasi-steady-state of long-lived photoexcitations, such as polarons triplet excitons in organic semiconductors, when the photoluminescence sample strong compared signal. In our instrument, we modulate continuous-wave laser at frequency $f_{pu}$ with mechanical chopper before exciting material. fractional change transmission tuneable monochromatic probe source modulated $f_{pr}$, digital lockin amplifier reference $f_{ref} = f_{pu} + f_{pr}$. generate sinusoidal wave for using home-built electronic circuit that generates their sum-frequency This scheme allows measurement transmittance induced pump $f_{pu} f_{pr}$ without parasitic signal $f_{pu}$, or pump-laser scatter. demonstrate power this approach measuring cleanly spectrum highly luminescent semiconductor polymer, poly(9,9-dioctylfluorene-co-benzothiadiazole), 10\,K. compare favourably obtained after subtraction dominant background.