In this blog post, we highlight a couple of laser applications for which we recently have developed novel gratings.
The first relates to pulse front tilting for THz generation, where our new fused silica transmission gratings provide a simple, efficient way to tilt the phase front. We encourage you to read our application note and our online calculator to learn more about this application.
Secondly, we have developed a low loss, high extinction ratio grating polarizer for variable attenuation of Ti:sapphire lasers. Read more about the product below and on our website, where you can also find the released Product Sheet.
Pulse Front Tilting
Pulse front tilt is a term that describes the phenomenon of an ultrashort pulse having a pulse front that is tilted relative to the propagation direction of the beam. Tilted pulse fronts have a notable application being phase-matched Terahertz (THz) generation by optical rectification of femtosecond laser pulses in LiNbO3. Diffraction gratings – and especially transmission gratings – provide an efficient method to generate the required pulse front tilt.
Ibsen has written a technical note that aims to explain the concept of optical rectification, the requirement for pulse front tilting, and derive practical equations to calculate the pulse front tilt of a grating configuration. You can read the full tech note here and also try our online calculator.
For high energy, ultrafast laser applications, common polarizer technologies used for variable attenuation do not fulfill the complete set of requirements to extinction ratio, transmission level, bandwidth, transmitted wavefront distortion, GDD ripple, and energy handling capability. For these applications, and initially developed solely for Ti:sapphire wavelengths, Ibsen offers a unique, grating-based polarizer.
The polarizer is 100% fused silica, with the polarizing grating being a surface relief, etched grating structure with no thin-film coatings of any kind. The grating polarizer transmits close to 100% of the incoming TM (p) polarized light, while the TE(s) polarized light is diverted into other diffraction orders (primarily -1T but also a few percent into reflected orders.)
In order to use the grating polarizer as a variable attenuator, either rotate the grating or the incoming, linearly polarized light so that the ratio of TM:TE provides the wanted attenuation.