Development of a wavefront sensor for terahertz pulses.

Emmanuel Abraham,Eric Freysz,Jérôme Degert,Takeshi Yasui,Harsono Cahyadi,Mathilde Brossard

doi:10.1364/oe.24.005203

Abstract

Wavefront characterization of terahertz pulses is essential to optimize far-field intensity distribution of time-domain (imaging) spectrometers or increase the peak power of intense terahertz sources. In this paper, we report on the wavefront measurement of terahertz pulses using a Hartmann sensor associated with a 2D electro-optic imaging system composed of a ZnTe crystal and a CMOS camera. We quantitatively determined the deformations of planar and converging spherical wavefronts using the modal Zernike reconstruction least-squares method. Associated with deformable mirrors, the sensor will also open the route to terahertz adaptive optics.

Highlights

The Hartmann sensor was invented more than a century ago for optical beam analysis [1]
We report on the wavefront measurement of terahertz pulses using a Hartmann sensor associated with a 2D electro-optic imaging system composed of a ZnTe crystal and a CMOS camera
This will provide a real advance for time-domain (imaging) spectrometers which require a perfect focalization of the THz beam or any other THz devices sensitive to wavefront distortions

Summary

Introduction

The Hartmann sensor was invented more than a century ago for optical beam analysis [1] It makes it possible to locally measure the wavefront slopes of an incoming optical radiation by using a mask composed of a circular holes array placed just in front of a 2D sensor. In the visible spectral region, commercially available Shack-Hartmann sensors can perform wavefront characterization for adaptive optics and a wide variety of applications including astronomy, ophthalmology and microscopy. These sensors are widely used to measure optical aberrations such as astigmatism, coma, spherical aberration, etc [3]. In the terahertz (THz) spectral domain, it is still challenging to fully measure the spatial profile and wavefront of a THz beam due to the lack of effective THz cameras

Methods

Results

Conclusion