Simple shearing interferometer measures wavefront of femtosecond laser pulses
A beamsplitter cube with one wedged entrance face produces an almost zero path-length difference for shearing interferometry.
|At left is the basic design of a traditional interferometer, and at right the more compact design of the interferometer created in the lab of University of Rochester optics professor Chunlei Guo. The new wedge-reversal shearing interferometer has the added advantage of being able to measure the wavefront of high-energy ultrafast laser pulses. (University of Rochester illustration / Michael Osadciw)|
Using an interferometer to characterize the spatial information of a continuous-wave (CW) laser beam can be done straightforwardly using a shearing interferometer, where the test wavefront is interfered with a positionally shifted duplicate of itself. However, measuring ultrafast laser pulses using this method is more difficult, because, given the short duration of a femtosecond pulse, traditional interferometers lose their functionality.
"A simple interferometer like the shear plate, where the beams reflected from the front and back surfaces interfere, no longer works," says, Chunlei Guo, a professor of optics at the University of Rochester (Rochester, NY).
Now, Guo and his associate, Billy Lam, have come up with a simple shearing-interferometer setup that works well with ultrafast pulses of sub-100-fs duration.1 In fact, the setup can characterize amplitude, phase, polarization, wavelength, and duration of the pulse.
The interferometer contains a single beamsplitter cube with one wedged entrance face, producing an almost zero path-length difference between unsheared and sheared beams, and a very stable interference pattern.
1. Billy Lam and Chunlei Guo, Nature Light: Science and Applications (2018); https://doi.org/10.1038/s41377-018-0022-0