Supercontinuum Generation over 2 µm

Effective supercontinuum generation in fiber mediain spectral range over 2 μm was experimentallydemonstrated. Supercontinuum generation wasobserved in passive optical fibers. Maximumspectral broadening was obtained in germaniumdopedfibers with longest wavelength near 2.7 μm.To provide high spectral density we used opticalfiber amplifiers. Thus supercontinuum generationwas obtained in holmium optical fiber amplifiersmedium with spectral density 10 W/nm, in therange from 2 to 2.5 μm. In thulium fiber amplifiersobserved amplification not only in conventionalrange near 1.8 μm, but in spectral range from 2.3 to2.5 μm, that corresponds to 3H4→ 3H5 opticaltransition possibility in thulium-doped opticalfibers

Импульсный волоконный гольмиевый лазер с внутрирезонаторным интерферометром Маха-Цандера

A scheme of a fully fiber holmium (Ho) laser with active Q-switching and lasing at wavelength of 2100 nm was realized. The effect of changing the reflection coefficient of the output mirror of the resonator (4, 10, 20 %) on the laser pulse duration is shown. A minimum pulse duration of 0.64 μs was obtained in a scheme with an output Bragg grating having a reflection coefficient of 20 %.Реализована схема полностью волоконного гольмиевого лазера с активной модуляцией добротности и генерацией на длине волны 2100 нм. Показано влияние изменения коэффициента отражения выходного зеркала резонатора (4, 10, 20 %) на длительность импульса. Получена минимальная длительность импульса 0,64 мкс в схеме с коэффициентом отражения выходной брэгговской решетки 20 %

Comparison of Continuous Wave and Ultrashort Pulsed Holmium-doped Fiber Lasers Exposure on Ex-vivo Tissue

Holmium (Ho 3+ ) laser systems emitting in the spectral range of 2-2.1m are widely used in many medical fields: urology, dermatology, surgery, and etc. This is due to the high absorption of laser radiation by water contained in soft tissues. It is of interest to compare the efficiency of soft tissue ablation using 2m lasers operating in continuous wave (CW) and ultrashort pulsed modes. In previous studies the Tm-doped fiber laser [1], Tm:YLF and Ho:YAG lasers [2] exposure have compared. © 2021 IEEE

РАЗРАБОТКА УНИВЕРСАЛЬНОГО ОПТИЧЕСКОГО СТЕНДА ДЛЯ ИЗМЕРЕНИЯ ДИНАМИКИ НАСЫЩЕНИЯ ПОГЛОЩЕНИЯ ОПТИЧЕСКИХ ПОГЛОТИТЕЛЕЙ

A universal stand for measuring the saturation absorption dynamics of optical absorbers has been created. The presented setup allows to carry out real-time measurements, as well as adjusting the heat load on the sample by changing the duty cycle and frequency of complex pulses.Создан универсальный стенд для измерения динамики насыщения поглощения оптических поглотителей. Представленная установка позволяет проводить измерения в реальном времени, а также регулировать тепловую нагрузку на образец изменением скважности и частоты импульсов сложной формы

Temporal Dynamics of Holmium-doped Fiber Laser with an Intracavity Mach-Zehnder Interferometer

An all-fiber scheme of Holmium laser with active Q-switching, implemented by an intracavity Mach-Zehnder interferometer, was realized. Influence of the cavity output mirror reflection coefficient (4 and 20%), modulation voltage and different pump power levels on the pulse duration was investigated. The minimum pulse duration of 0.62 µs was obtained in a scheme with an output Bragg grating reflection coefficient of 20%. Wherein the peak power was 13 W. © 2020 IEEE

Numerical simulation and experiment on generation dynamics of a Ho³⁺-doped fiber laser with an intracavity Mach–Zehnder modulator

We present the numerical simulation and experimental results on generation dynamics of an all-fiber holmium laser with an intracavity modulator based on a Mach–Zehnder interferometer. The experimental data were compared with numerical simulation results in a wide range of parameters. An explanation for the observed increase in the pulse repetition rate from 5.8 to 11.6 kHz, as well as the transition to the chaotic pulsations mode, was given. A numerical variation of the unknown or difficult-to-measure losses in the experiment was carried out. The obtained set of parameters allowed us to implement the correct numerical optimization of an active medium and cavity. As a result, the peak powers of about 9.5 and 13 W were obtained during the experiments, as well as in the numerical simulation

Numerical simulation and experiment on generation dynamics of a Ho3+-doped fiber laser with an intracavity Mach-Zehnder modulator

We present the numerical simulation and experimental results on generation dynamics of an all-fiber holmium laser with an intracavity modulator based on a Mach-Zehnder interferometer. The experimental data were compared with numerical simulation results in a wide range of parameters. An explanation for the observed increase in the pulse repetition rate from 5.8 to 11.6 kHz, as well as the transition to the chaotic pulsations mode, was given. A numerical variation of the unknown or difficult-to-measure losses in the experiment was carried out. The obtained set of parameters allowed us to implement the correct numerical optimization of an active medium and cavity. As a result, the peak powers of about 9.5 and 13 W were obtained during the experiments, as well as in the numerical simulation. (C) 2020 Optical Society of Americ

Ex Vivo Exposure to Soft Biological Tissues by the 2-μm All-Fiber Ultrafast Holmium Laser System

We present the results of ex vivo exposure by an ultrafast all-fiber Holmium laser system to porcine longissimus muscle tissues. A simple Ho-doped laser system generated ultrashort pulsed radiation with less than 1 ps pulse width and a repetition rate of 20 MHz at a central wavelength of 2.06 μm. Single-spot ex vivo experiments were performed at an average power of 0.3 W and different exposure times of 5, 30 and 60 s, varying the total applied energy in the range of 1.5–18 J. Evaluation of laser radiation exposure was performed according to the depth and diameter of coagulation zones, ablation craters and thermal damage zones during the morphological study. Exposure by ultrashort pulsed radiation with an average power of 0.3 W showed destructive changes in the muscle tissue after 5 s and nucleation of an ablative crater. The maximum ablation efficiency was about 28% at the ablation depth and diameter of 180 μm and 500 μm, respectively. The continuous-wave radiation impact at the same parameters resulted only in heating of the near-muscular tissue, without ablation and coagulation traces. Exposure to tissue with an average power at 0.3 W of ul-trashort pulsed radiation led, within 30 and 60 s, to similar results as caused by 0.5 W of continuous-wave radiation, although with less carbonization formation. © 2022 by the authors. Licensee MDPI, Basel, Switzerland