The first demonstration of a compact all-fiber figure-9 double-clad erbium-ytterbium laser working in the dissipative soliton resonance (DSR) regime is presented. Mode-locking was achieved using a nonlinear amplifying loop (NALM) resonator configuration. The laser was assembled with an additional 475 m long spool of SMF28 fiber in the NALM loop in order to obtain large net-anomalous cavity dispersion ($-10.4{\mathrm{ps}}^2$), and therefore ensure that DSR would be the dominant mode-locking mechanism. At maximum pump power (4.78 W) the laser generated rectangular-shaped pulses with 455 ns duration and an average power of 950 mW, which at a repetition frequency of 412 kHz corresponds to a record energy of 2.3 μJ per pulse.

In this work, we present for the first time a laser-based dual gas sensor utilizing a silica-based Antiresonant Hollow-Core Fiber (ARHCF) operating in the Near- and Mid-Infrared spectral region. A 1-m-long fiber with an 84-µm diameter air-core was implemented as a low-volume absorption cell in a sensor configuration utilizing the simple and well-known Wavelength Modulation Spectroscopy (WMS) method. The fiber was filled with a mixture of methane (CH₄) and carbon dioxide (CO₂), and a simultaneous detection of both gases was demonstrated targeting their transitions at 3.334 µm and 1.574 µm, respectively. Due to excellent guidance properties of the fiber and low background noise, the proposed sensor reached a detection limit down to 24 parts-per-billion by volume for CH₄ and 144 parts-per-million by volume for CO₂. The obtained results confirm the suitability of ARHCF for efficient use in gas sensing applications for over a broad spectral range. Thanks to the demonstrated low loss, such fibers with lengths of over one meter can be used for increasing the laser-gas molecules interaction path, substituting bulk optics-based multipass cells, while delivering required flexibility, compactness, reliability and enhancement in the sensor’s sensitivity.

First demonstration of exploiting Dissipative Soliton Resonance (DSR) effects for generating high energy square-shaped pulses in an all-fiber mode-locked Double Clad (DC) erbium-ytterbium (Er-Yb) figure-8 laser (F8L) is presented. The laser was capable of generating 170 ns pulses with an average power of 1.7 W at 800 kHz repetition rate, which corresponds to a record pulse energy of 2.13 μJ, achieved directly from the resonator, without Q-switching, cavity dumping or additional amplifiers. Unique circulator-based out-coupling of high energy pulses in the directional loop is proposed as a method of preventing damage to the all-fiber setup. Appropriate laser design allowed utilizing Peak Power Clamping (PPC) effect for linear pulse duration tuning via changing the pump power.

Photothermal spectroscopy (PTS) is a technique used for determining the composition of liquids, solids and gases. In PTS, the sample is illuminated with a radiation source, and the thermal response of the analyte (e.g., refractive index) is analyzed to gain information about its content. Recent advances in this unique method of detecting gaseous samples show that photothermal gas spectroscopy can be an interesting alternative to commonly used absorption techniques. Moreover, if designed properly, sensors using PTS detection technique can not only reach sensitivities comparable with other, more complex techniques, but can significantly simplify the design of the sensor. In this review, recent developments in photothermal spectroscopy of gases will be summarized and discussed.

Laser-based gas sensors utilizing various light-gas interaction phenomena have proved their capacity for detecting different gases. However, achieving reasonable sensitivity, especially in the mid-infrared, is crucial. Improving sensor detectivity usually requires incorporating multipass cells, which increase the light-gas interaction path length at a cost of reduced stability. An unconventional solution comes with the aid of hollow-core fibers. In such a fiber, light is guided inside an air-core which, when filled with the analyte gas can serve as a low-volume and robust absorption cell. Here we report on the use of a borosilicate antiresonant hollow-core fiber for laser-based gas sensing. Due to its unique structure and guidance, this fiber provides low-loss, single-mode transmission > 5 µ m . The feasibility of using the fiber as a gas cell was verified by detecting nitrous oxide at 5.26 µm with a minimum detection limit of 20 ppbv.

A laser-based spectrometer exploiting a novel Kagome-type hollow core photonic crystal fiber, which serves as a gas cell is demonstrated. Low attenuation of this silica-based fiber in the 3.4 µm wavelength region enables accessing strong, fundamental transitions of methane, which was used as a target analyte in the presented experiment. With an all-fiber differential frequency generation source combined with wavelength modulation spectroscopy technique detection limit at single parts-per-million by volume level was obtained. These results show potential for developing compact and sensitive Kagome-fiber-based mid-infrared laser spectrometers.