In this work, we present a commercial CMOS (Complementary Metal Oxide Semiconductor) Raspberry Pi camera implemented as a Near-Infrared detector for both spatial and temporal characterization of femtosecond pulses delivered from a femtosecond Erbium Doped Fiber laser (fs-EDFL) @ 1.55 µm, based on the Two Photon Absorption (TPA) process. The capacity of the device was assessed by measuring the spatial beam profile of the fs-EDFL and comparing the experimental results with the theoretical Fresnel diffraction pattern. We also demonstrate the potential of the CMOS Raspberry Pi camera as a wavefront sensor through its a nonlinear response in a Shack-Hartmann array and for the temporal characterization of the femtosecond pulses delivered from the fs-EDFL through TPA Intensity autocorrelation measurements. The direct pulse detection and measurement, through the nonlinear response with a CMOS, is proposed as a novel and affordable high-resolution and high-sensitivity alternative to costly detectors such as CCDs, wavefront sensors and beam profilers @ 1.55 µm. The measured fluence threshold, down to 17.5 µJ/cm2, and pJ/pulse energy response represents the lowest reported values applied as a beam profiler and a TPA Shack-Hartmann wavefront sensor, to our knowledge.
We present a Kerr-lens-modelocked, three-element, diode-pumped Ti:sapphire laser producing 111-fs pulses at a repetition frequency of 1.02 GHz. Self-starting soliton-modelocked operation with an output power of 106 mW was obtained when the laser was pumped at 1.0 W with a single 527-nm laser diode. The output exhibits a relative intensity noise of 0.06% (1 Hz – 1 MHz) and locking of the repetition rate to an external reference is demonstrated with a phase error of 1.7 mrad (1 Hz–1 MHz). The simplicity of the laser makes it an attractive candidate as a module for integration into larger systems.
Using coherent broadband mid-infrared light from a picosecond optical parametric oscillator we introduce a flexible, easy to use, high-resolution technique which can be utilized to conduct remote stand-off, or fiber delivered, multi-species spectroscopy in a spectroscopically cluttered environment. In particular, both narrow line-like and broad continuum-like species can be handled simultaneously. If only species with narrow line-like absorptions are present, this can be done without the need for an explicit reference spectrum. We demonstrate the approach by performing absorption spectroscopy of H2O, CH4, CH3OH and C2H7NO (MEA) at high optical resolution (≈0.033 cm−1) and via fiber delivery, opening the possibility of conducting multi-species spectroscopy in remote and hazardous environments. Spectral co-fitting of all absorption features and of the spectrum of the light-source provides a robust means of determining species concentrations, with detection limits of 290 ppb and 890 ppb obtained for CH4 and MEA respectively using a 10.5-m Herriott cell and 32 seconds measurement time.
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