Newport Corporation has introduced the WEU-02, a wavelength extension unit designed to expand the capability of femtosecond lasers. Through a series of user controls, the WEU-02 can be configured for use in various spectroscopy, imaging, and pump-probe applications. It can also be integrated into two-photon microscope set-ups to add modalities for enhanced imaging capabilities.
The design of the WEU-02 allows the fundamental beam to pass through, preserving the beam path and tuning range of the pump source. A portion of the fundamental can be sent to a photonic crystal fibre (PCF) to be converted to a broadband supercontinuum. This light can then be recombined with the remaining fundamental for use in pump-probe and multimodal spectroscopy and microscopy experiments. This supercontinuum can be used as a Stokes beam to add broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy capabilities around 3,000cm-1 in existing set-ups utilising two-photon excited fluorescence (TPEF) and second harmonic generation (SHG).
User controls include a thumbwheel to either maintain the fundamental for two-photon imaging, or selectively split to add pump-probe and multimodal capability. Thumbwheels are also used to independently control the attenuation of the fundamental beam, the input to the PCF, and the output Stokes beams. Two-position slide controls allow the user to narrow the bandwidth to 3nm around an 800nm pump, or select whether or not to recombine the pump and Stokes. A micrometer is used to fine-tune the timing of the two beams in order to overlap them temporally.