Self-referenced spectral interferometry for ultra-short infrared pulse characterization

Abstract

Abstract. Self-Referenced Spectral Interferometry is used for single shot pulse characterization over the 0.9-2.5 µm spectral range with a single spectrometer and an optimized optical setup. We characterize sub-55 fs pulses from 1.4 µm to 2 µm and broadband 2.5-cycle pulses at 1.65 µm (13 fs FWHM).The development of laser sources delivering tunable, ultra-broadband femtosecond pulses in the shortwavelength infrared (SW-IR) and mid-infrared (mid-IR) spectral ranges open-up the way for new laser pulse characterization devices. Recently developed laser systems make use of Optical Parametric amplification (OPA) [1] and Optical Parametric Chirped Pulse Amplification (OPCPA) [2] to produce sub-20 fs pulses covering bandwidth from 1.2 to 2.4 µm with a few milli-Joule energy per pulse. A broadband, single shot characterization technique is mandatory, since these sources are based on nonlinear parametric frequency conversion, and so intensity fluctuations in the pump lead to shot to shot phase fluctuations in the signal. Up to our knowledge, none of the usually used characterization techniques (like FROG or SPIDER) have been adapted yet to few-cycle pulse characterization in the SWIR [3].Self-Referenced Spectral Interferometry (SRSI) [4,5], discussed here, is a technique which offers intrinsically single-shot and frequency-conserving pulse reconstruction (i.e. the recorded signal is at the same wavelength as the input signal). It is thus possible to characterize both spectrum and phase with one single spectrometer. We demonstrate a SRSI based measurement device for ultra-short broadband SWIR pulse characterization with a single extended-InGaAS spectrometer. Single-shot measurement of sub-55 fs pulses in the 1.4 -2 µm spectral range is reported and attests to the broadband capability of the technique. In addition, we characterized few-cycle pulses (13 fs FWHM, λ 0 =1.65 µm) as an experimental confirmation of the device's capability to measure ultra-short pulses in the SWIR [3].