Cu2Te-PVA as saturable absorber for generating Q-switched erbium-doped fiber laser

Abstract

A passively Q-switched erbium-doped fiber laser (EDFL) using copper telluride-polyvinyl alcohol (Cu2Te-PVA) thin film as saturable absorber (SA) was proposed and demonstrated. The generated Q-switched pulses could be tuned over a tuning range of 44 nm from 1530 nm to 1574 nm, with the addition of a tunable bandpass filter (TBPF) into the C-band laser cavity. The pump power of 130.1 mW to 221.0 mW was used to observe the output pulses, which had repetition rates from 51.3 kHz to 61.7 kHz, with a minimum pulse width of around 1.84 µs and highest pulse energy of 7 nJ. The generated pulses were stable with a constant signal to noise ratio (SNR) value of around 51 dB when tested under continuous operation over a period of 60 minutes. To the best of our knowledge, this is the first demonstration of Q-switched pulses induced by a Cu2Te-PVA based SA in an EDFL.

Simple synthesis and photoelectric properties of Cu2Te nanotubes

“…Among them, α is the molar absorption coefficient, h is the Planck constant, ν is the frequency of the incident photon, A is the scale constant, and E g is the optical band gap value of the semiconductor material. Since Cu 2 Te is a direct band gap semiconductor, 40 the value of n is taken as 1/2. The Tauc curve in the figure shows ( αhν ) 2 and ( hν ).…”

Analysis of the Passive Stabilization Methods of Optical Frequency Comb in Ultrashort-Pulse Erbium-Doped Fiber Lasers

“…Carbon nanostructures [138,139]; • Two-dimensional materials, such as bismuthine [140], black phosphorus (BP) [141], topological insulator (TI) [142,143], and others [144][145][146].…”

“…The main characteristics of saturable absorbers are: • Modulation depth is maximum change in nonlinear absorption (or reflection) caused by radiation incident on the absorber; • Saturation energy is the energy required to clear the absorber by a factor of 1/𝑒𝑒 (≈37%); • The recovery (relaxation) time is the time during which the absorption is restored 𝑒𝑒 times (2.718 times) after the passage of the pulse; • Non-saturable losses are unwanted losses that do not participate in the nonlinear absorption process; • Service life is the time during which the saturable absorber provides the required modulation depth and other properties; •Moreover, note such characteristics as the optical damage threshold and GVD. The following types of saturable absorbers are most commonly used in fiber lasers: • An absorber using nonlinear polarization evolution (NEP) in a fiber[127,128]; • Nonlinear active loop mirror[129][130][131] or nonlinear optical loop mirror[132,133]; • Graded index multimode fiber (GIMF) as saturable absorber induced by nonlinear multimodal interference (NL-MML)[134,135]; • Semiconductor saturable-absorber mirror[136,137];•Carbon nanostructures[138,139]; • Two-dimensional materials, such as bismuthine[140], black phosphorus (BP)[141], topological insulator (TI)[142,143], and others[144][145][146].…”

L-band femtosecond fiber laser with Cu2Te-PVA thin film

“…Cu2Te, for example, has an optical band gap of 1.1 eV [63]. In previous work, the Cu2Te thin-film SA has been successfully generated passively Q-switched pulse in erbium-doped fiber laser (EDFL) (C-band) [64] and thuliumfluoride fiber laser (S-band) [65]. In [66], the mode-locked pulse was successfully generated using Cu2Te solution coated with tapered fiber SA in thulium-doped fiber laser (2 µm band).…”