3-μm mid-infrared pulse generation using topological insulator as the saturable absorber

TLDR

The authors demonstrate a 1150‑nm diode‑pumped Ho³⁺‑doped ZBLAN fiber laser passively Q‑switched with a Bi₂Te₃ topological‑insulator saturable absorber. The Bi₂Te₃ saturable absorber was fabricated by hydrothermal intercalation/exfoliation and deposited on a CaF₂ substrate for free‑space use. The device produced a 2.12 MW cm⁻² saturable peak intensity, 51.3 % modulation depth, and yielded stable 2.98‑µm Q‑switched pulses at 81.96 kHz with 1.37 µs duration, 327.4 mW output power, 3.99 µJ pulse energy, and 11.6 % slope efficiency, confirming TI as a reliable 3‑µm saturable absorber.

Abstract

We report an 1150-nm diode-pump passively Q-switched Ho3+-doped ZBLAN fiber laser using topological insulator (TI): Bi2Te3 as the saturable absorber (SA). The TI: Bi2Te3 prepared using the cost-effective hydrothermal intercalation/exfoliation method was dropped onto a CaF2 substrate to fabricate the free-space SA component. It has a low saturable peak intensity of 2.12 MW/cm2 and a high modulation depth of 51.3% measured at 2 μm. Inserting this component into a linear-cavity Ho3+-doped ZBLAN fiber laser, stable Q-switched pulses at 2979.9 nm were obtained with the repetition rate of 81.96 kHz and pulse duration of 1.37 μs. The achieved maximum output power and pulse energy were 327.4 mW at a slope efficiency of 11.6% and 3.99 μJ, respectively, only limited by the available pump power. Our work reveals that the TIs are absolutely a class of promising and reliable SAs for pulse generation at 3-μm mid-infrared waveband.