Mid-Infrared ZnS Ridge Waveguide Fabricated by Femtosecond Laser Ablation Combined With Ion Irradiation

Xinbin Zhang,Yazhou Cheng,Yongcheng Zhang

doi:10.3389/fphy.2021.731571

Abstract

We have experimentally studied the fabrication of ridge waveguides in zinc sulfide (ZnS) crystal by femtosecond laser ablation combined with Kr8+ ion irradiation. At the wavelength of 4 μm, the waveguide at TE mode shows better guiding properties than TM mode. The transmission performance of the waveguide is improved by using thermal annealing technology to reduce the color centers and point defects in the waveguide. The waveguide propagation loss at TE mode at 4 μm wavelength is reduced to as low as 0.6 dB/cm after annealing. Raman spectroscopy shows that Kr8+ ion irradiation does not cause large lattice damage to ZnS crystal.

Highlights

Infrared band can be divided into three bands: near-infrared (780–2,560 nm), mid-infrared (2,560–25,000 nm) and far-infrared (25,000–1,000,000 nm) [1, 2]
In this paper, we innovatively use ion irradiation combined with femtosecond laser ablation to fabricate ridge waveguides on zinc sulfide (ZnS) crystals, and study the transmission characteristics of ridge waveguides at midinfrared 4 μm wavelength
We carried out four steps of annealing treatments, and the annealing temperatures were set as 180°C, 240°C, 300°C, FIGURE 2 | Schematic diagram of end face coupling system of ZnS crystal ridge optical waveguides

Summary

INTRODUCTION

Infrared band can be divided into three bands: near-infrared (780–2,560 nm), mid-infrared (2,560–25,000 nm) and far-infrared (25,000–1,000,000 nm) [1, 2]. ZnS is inert and can be used in wet and dry environments It has excellent transmittance and high refractive index (2.2527 at wavelength of 4 μm), and can be used in photonic crystal devices working in mid-infrared band. Because of these excellent properties, ZnS crystals has been widely used in infrared windows, lasers, electroluminescence, light-emitting diodes, optical antireflection films and biodevices [12,13,14,15,16]. In this paper, we innovatively use ion irradiation combined with femtosecond laser ablation to fabricate ridge waveguides on ZnS crystals, and study the transmission characteristics of ridge waveguides at midinfrared 4 μm wavelength

EXPERIMENTS

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT

CONCLUSION