An oscillator-driven, time-resolved optical pump/NIR supercontinuum probe spectrometer

Abstract

We present a novel, to the best of knowledge, time-resolved, optical pump/NIR supercontinuum probe spectrometer suitable for oscillators. A NIR supercontinuum probe spectrum (850–1250 nm) is generated in a photonic crystal fiber, dispersed across a digital micromirror device (DMD), and then raster scanned into a single element detector at a 5 Hz rate. Dual modulation of pump and probe beams at disparate frequencies permits simultaneous measurement of both the bare reflectance R and its photoinduced change ΔR through lock-in detection, allowing for continuously self-normalized measurement of ΔR/R. Example data are presented on a germanium wafer sample that demonstrate for signals of order ΔR/R ∼ 10−3, a 2.87 nm spectral resolution and ≲ 400  fs temporal resolution pre-recompression, and comparable sensitivity to standard time-resolved, amplifier-based pump–probe techniques.