Abstract

Telecentric beam scanning using f-θ lenses offers nearly uniform spot size, linear beam displacement, and normal incidence angle over a planar surface. These unique properties allow for the minimization of imaging distortion over a wide field-of-view. In this article, we present a numerical method for designing custom f-θ lenses in the THz regime. We fabricated three lenses made from different commonly used polymer materials in the THz optics. We demonstrated their optical performance metrics compared to a conventional plano-convex lens over the broadband 0.3 THz–1 THz range. We find that the f-θ lens designed using the optical properties of high-density polyethylene achieved superior performance by maintaining a constant phase over a wide field of view of about 34°. We demonstrate this isophase property by measuring a constant time of arrival of the THz time-domain pulses over a reference mirror with a standard deviation of ∼19 fs, in excellent agreement with simulation predictions. This work will pave the way for the design and implementation of highly precise and fast telecentric imaging systems in the THz frequencies.

Highlights

  • F-θ lenses have found many diverse applications in highly accurate laser beam scanning over the entire electromagnetic spectrum

  • The final criterion for which the lenses were evaluated is the consistency of the time of arrival (TOA) as a function of the deflection angle

  • In comparison to the drift measurements, the TPX and high-density polyethylene (HDPE) f-θ lenses show a close to theoretically ideal isophase performance up to 10○ and 17○, respectively

Read more

Summary

INTRODUCTION

F-θ lenses have found many diverse applications in highly accurate laser beam scanning over the entire electromagnetic spectrum. Using conventional spherical lenses results in significant image distortions from a planar target Alternative scanning optics, such as flat-field lenses, have been used to address this problem.. F-θ lenses are designed to provide a linear beam displacement as a function of the deflection angle (θ; see Fig. 1), resulting in a constant scan rate on a planar surface. When used in a telecentric system, f-θ lenses produce constant spot size and imaging resolution as a function of the deflection angle, eliminating distortions at the edges of the fieldof-view.. When used in a telecentric system, f-θ lenses produce constant spot size and imaging resolution as a function of the deflection angle, eliminating distortions at the edges of the fieldof-view.9 These properties ensure a broadband THz constant phase over the scanning plane, i.e., the planar focal surface is an isophase. We find that the HDPE f-θ scanning lens can achieve isophase behavior over a wide 34○ field of view, as measured by a constant sub-cycle time of arrival (TOA) ∼1/4 of the pulse duration of the femtosecond probe beam

LENS DESIGN
LENS CHARACTERIZATION
Beam profiles
Time of arrival
CONCLUSION
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call