Timing and Recombination Unit, Dual Output Laser Sources

The TRU Timing and Recombination Unit was developed by research scientists in Newport’s Technology and Applications Center, and is engineered to synchronize the two output beams of dual output laser sources, facilitating a large variety of single and dual beam, ultrafast spectroscopy and imaging applications, such as:

• pump-probe
• single- and multi-color two-photon fluorescence (TPF)
• second harmonic generation (SHG)
• third harmonic generation (THG)
• stimulated Raman scattering (SRS)
• coherent anti-Stokes Raman scattering (CARS)
• fluorescence resonance energy transfer (FRET)
• two-photon uncaging

Inside the TRU box, each beam is conveniently equipped with a Newport VA-BB-4 manual ultrafast variable attenuator for precise power control of the transmitted output. A specially designed, high accuracy, dual position manual slider assembly allows switching from a single to a dual beam collinear setup without affecting alignment. In the single beam regime, both the fixed (1041 nm) and/or tunable (680 – 1300 nm) beams of InSight DS+ Dual are separately available. In the dual beam, collinear regime, it is possible to select the tunable laser wavelength from 760 - 940 nm, which when overlapped with the fixed 1041 nm output, corresponds to a Raman shift range of 1000 – 3500 cm^-1 for CARS and SRS. This range is limited by the dichroic beamsplitter used to recombine the beams, and the geometry of the optical layout. The beam paths and variable delay line are optimized to temporally and spatially overlap the fixed and tunable beams. The TRU compensates for the optical delay introduced by downstream optics and the DeepSee^TM pre-compressor inside the laser, ensuring that transform-limited pulses arrive at the focal plane of the objective. The system includes silver mirrors throughout, but the tunable output can be upgraded to broadband, ultrafast dielectric mirrors for higher throughput. Both versions provide temporally and spectrally distortion-free outputs.