ZnSe Laser Research Articles

Temperature dependence of Fe:ZnSe mid-infrared spectral and laser output properties under ∼4 µm radiation excitation

This paper presents the temperature dependence of the spectroscopic and laser properties of the Fe2+:ZnSe single crystal under excitation by radiation at a wavelength of ∼4.04µm. Excitation was supported by the Er:YAG laser (∼2.94µm) operated in the Q-switched or free-running (FR) mode that pumped the Fe:ZnSe laser cooled by liquid nitrogen to 78 K. This system generated radiation at the wavelength of ∼4.04µm. Temperature dependence of absorption, fluorescence spectra, and fluorescence decay time of Fe2+ ions was measured. The optimal temperature that allows efficient Fe:ZnSe laser system operation with maximum laser output energy was sought in both regimes. It was characterized at a repetition rate of 1 Hz with pulse durations of ∼175ns and ∼155µs in both modes, respectively. The highest laser output energies obtained with the crystal placed in the cryostat in gain-switched (GS) and FR modes were ∼385µJ at 260 K and ∼374µJ at 190 K, respectively. Maximum optical-to-optical efficiencies in the same modes were ∼13% at 260 K and ∼32% at 170 K, respectively. Wide laser radiation oscillation spectra depending on the temperature ranging from ∼4.3µm at 140 K to ∼4.9µm at 340 K obtained with a Gaussian-like beam spatial profile were demonstrated. Under atmospheric conditions at RT, this laser system reached a pulse energy of over 0.5 mJ at ∼4.78µm in ∼135ns pulses, which corresponds to a peak power of ∼3.9kW.

High average power (105 W) Fe:ZnSe laser pumped by radiation of laser diode side-pumped Er:YAG lasers.

A high average power re-frequency operation Fe:ZnSe laser using laser diode side-pumped free-running Er:YAG lasers as activating sources is presented. Two pieces of subsurface layer doped Fe:ZnSe polycrystal are adoptive in a reflective resonator configuration and face-cooled by liquid nitrogen. A maximal Fe:ZnSe laser power of 105 W at a wavelength of 4.1 μm is achieved upon pumping by ten home-made Er:YAG lasers with fiber coupled output working at a frequency of 250 Hz and a pulse duration of ∼420 μs. Corresponding to the maximum Fe:ZnSe laser power, the optical-optical efficiency and slope efficiency with respect to the absorbed pump power are 43% and 44% respectively. The beam quality factor M2 is measured to be 3.4. To the best of our knowledge, it is the highest output average power of an Fe:ZnSe laser reported.

High-Repetition-Rate 2.3–2.7 µm Acousto-Optically Tuned Narrow-Line Laser System Comprising Two Master Oscillators and Power Amplifiers Based on Polycrystalline Cr2+:ZnSe with the 2.1 µm Ho3+:YAG Pulsed Pumping

High-average-power narrow-linewidth tunable solid-state lasers in the wavelength region between 2 and 3 μm are attractive light sources for many applications. This paper reports a narrow-linewidth widely tunable laser system based on the polycrystalline Cr2+:ZnSe elements pumped by repetitively pulsed 2.1 µm Ho3+:YAG laser operating at a pulse rate of tens of kilohertz. An advanced procedure of ZnSe element doping and surface improvement was applied to increase the laser-induced damage threshold, which resulted in an increase in the output power of the Cr2+:ZnSe laser system. The high-average-power laser system comprised double master oscillators and power amplifiers: Ho3+:YAG and Cr2+:ZnSe laser oscillators, and Ho3+:YAG and Cr2+:ZnSe power amplifiers. The output wavelength was widely tuned within 2.3–2.7 µm by means of an acousto-optical tunable filter inside a Cr2+:ZnSe master oscillator cavity. The narrow-linewidth operation at the pulse repetition rate of 20–40 kHz in a high-quality beam with an average output power of up to 9.7 W was demonstrated.

Deposition of Fe-doped CdS films by spray pyrolysis from various precursors

Iron-doped cadmium sulfide films (Fe–CdS) were produced by spray pyrolysis using iron nitrate, chloride and sulfate as iron precursors. Based on experimental analysis data and thermodynamic calculations, it was found that the composition, uniformity and surface morphology of the films significantly depend on the nature of the iron precursor. It has been found that all synthesized Fe–CdS films can be used as master alloys for the manufacture of Fe:ZnSe laser elements.

5 µm CW Ce3+-doped chalcogenide glass fiber laser with 17% slope efficiency.

Efficient room temperature mid-infrared laser action in a Ce3+-doped chalcogenide fiber was demonstrated. The fiber had a doped selenide glass core in an undoped sulfide glass cladding. The pump source was a CW Fe2+:ZnSe laser emitting at 4.14 µm. The optimized fiber length allowed obtaining up to 7 mW of 5.06 µm output with 17% slope efficiency at room temperature.

ZnSe:(Cr,Fe) laser crystal matrices: Challenges related to doping

We investigate co-doped ZnSe: (Cr, Fe) laser crystals with an approach that includes both optical spectroscopy and theoretical modelling. We found that concentrations of chromium and iron up to 1018 cm−3 are optimal for obtaining a homogeneous solid solution in designing laser crystals. Higher dopant concentrations lead to the formation of clusters with spinel structure in the ZnSe matrix. The optimal effectiveness of ZnSe laser media with active Cr2+ and Fe2+ elements is achieved at temperatures of around 100 K. Heating induces charge transfers like Fe2+→Fe3+ and Cr2+→Cr3+, while cooling results in phonon freezing. A theoretical model has been developed to explain the observed temperature evolution of the absorption spectrum. The types and values of distortions of the Cr- and Fe-based coordination complexes are determined. We have found that the Jahn-Teller distortions are crucial for modelling the temperature-dependent changes of the absorption spectra.

Optimizing the beam quality of high-energy pulse mid-IR Fe:ZnSe laser

The mid-IR Fe:ZnSe laser has gained widespread attention due to its enormous potential with high-energy output. However, applications of Fe:ZnSe laser are limited by the beam quality. To optimize the beam quality of high-energy pulse Fe:ZnSe laser, this study presents a method of using spatial filtering in the resonator. Based on the theory of the ABCD transfer matrix and simulation of resonator stability and beam radius properties, the structure of the resonator was designed. Additionally, we study the output properties of Fe:ZnSe laser with different aperture diameters. We demonstrate when the aperture diameter D = 0.5 mm, the Fe:ZnSe laser output energy is 45.7 mJ and the beam quality is Mx2=2.11, My2=2.29, which is the best beam quality of using a pulse-pumped source to our knowledge. This method will guide for optimizing the beam quality of high-energy pulse mid-IR laser.

Quasi-collinearly Pumped Fe:ZnSe Laser by ~4 µm Radiation

Radiation with a wavelength of ~4 µm was used for quasi-collinear excitation of the Fe:ZnSe laser. The highest output energy was achieved at the optimal crystal temperature of 230 K with the generated radiation wavelength of ~4.5 µm.

High-power compact continuous-wave Fe:ZnSe laser at 4 µm with >50% overall conversion efficiency

High-power compact continuous-wave Fe:ZnSe laser at 4 µm with >50% overall conversion efficiency

Continuous-wave and broadly tunable Cr:ZnSe laser pumped by a short wavelength Tm:YLF bulk laser

Continuous-wave and broadly tunable Cr:ZnSe laser pumped by a short wavelength Tm:YLF bulk laser

Study on Electrically Modulated Quasi-Continuous Wave Fe: ZnSe Solid-State Laser with Hundred-Hertz.

Iron-doped binary chalcogenide crystals are very promising for tunable solid-state lasers operating over the 3~5 μm spectral range. Fe: ZnSe is one of the most important gain crystals with the obvious advantages of material characteristics and conversion efficiency. By adjusting the output mode of the pump source, an Fe: ZnSe laser can operate in two modes at liquid nitrogen temperatures: continuous wave (CW) and pulse output. In terms of CW output, the Fe: ZnSe laser obtained a maximum 2.63 W continuous power output which was confined to the power of the pump source. An optical-to-optical efficiency of 47.05% was acquired. Direct electrical modulation was applied to the pump source. The highest average power of the quasi-CW laser, whose central wavelength is 4.02 μm, has a value of 253 mW with an optical-to-optical efficiency of 42.88% and a full width at half maximum (FWHM) of 23 nm when the pulse frequency is 100 Hz of 10% duty factor. The output waveform is consistent with the modulation waveform applied to the pump source. We report to the first of our knowledge an electrically modulated quasi-CW Fe: ZnSe laser in the pulse regime, equipped with features of compactness in structure, ignoring additional modulators, convenience in control, high efficiency, and sustainable operation, of great interest for solving numerous scientific and applied problems.

Mid-infrared self-difference frequency generation via random quasi-phase-matching in Cr:ZnSe laser

This study presents the first ever demonstration of self-difference frequency generation (DFG) under random quasi-phase-matching (RQPM) in a polycrystalline Cr:ZnSe gain medium. An RQPM-based self-DFG Cr:ZnSe laser was developed with broad vibronic spectroscopic properties along with a wide phase-matching spectral bandwidth, offering ultrabroad tunability of nanosecond mid-infrared pulses in the 7.6–16 µm spectral range by pumping with a Tm:YAG laser at 2.013 µm. Trace detection of N2O was performed by multi-pass absorption spectroscopy using an electronically tuned self-DFG output, controlled by an acousto-optic tunable filter. The proposed laser source is expected to find applications in the real-time monitoring of volatile organic compounds through differential absorption spectroscopy.

Five-micron Ce 3+ ion fiber laser

The spectral and temporal characteristics of a Ce 3+ -doped chalcogenide fiber laser pumped by a continuous Fe 2+ :ZnSe laser were investigated in this work.

Modeling and analysis of actively Q-switched Fe: ZnSe laser pumped by a 2.8 µm fiber laser

Modeling and analysis of actively Q-switched Fe: ZnSe laser pumped by a 2.8 µm fiber laser

Characteristics of a CW ∼5 μm Ce3+-doped chalcogenide glass fiber laser

Energy, spectral and temporal characteristics of a Ce3+-doped chalcogenide glass fiber laser continuously pumped by a 4.16 μm Fe2+:ZnSe laser were investigated. Milliwatt level output power was obtained. In case of low Q-factor of the resonator the laser operated at λ = 4.62 μm corresponding to the narrow peak in Ce3+ emission spectrum. At higher Q-factor, the lasing wavelength changed to 5.0–5.1 μm corresponding to the plateau in the gain spectrum. In contrast to Tb3+-doped mid-infrared fiber lasers, Ce3+-doped fiber laser had no tendency to non-relaxing spike operation.

Study of Fe:ZnSe Laser Exited by Diode Side-Pumped Er:YAG Laser

The performance of a Fe:ZnSe laser was investigated in different schemes of excitation by a pulsed diode side-pumped Er:YAG laser. At the temperature of liquid nitrogen, the Fe:ZnSe laser, pumped by a free running 360-μs Er:YAG laser and demonstrated a pulse energy of 53 mJ with a slope efficiency of 42% relative to absorbed pump energy. When operating at room temperature, two optical schemes were considered. In the first one, the Fe:ZnSe laser crystal was pumped by a Q-switched Er:YAG laser with a passive shutter based on an additional Fe:ZnSe crystalline plate, and the cavities of both lasers were independent. In the second scheme, the cavities of the Fe:ZnSe and Er:YAG lasers were coupled, and the Fe:ZnSe crystal simultaneously served as an active element of the Fe:ZnSe laser and a passive shutter of the Er:YAG laser. Pulses with a duration of less than 200 ns and an energy of ~1 mJ were obtained from the Fe:ZnSe laser with a repetition rate of up to 50 kHz. The experimental waveforms of the laser pulses were approximated by rate equations.

Pulse high energy Fe: ZnSe laser pumped by Q-switched Er: YAG laser.

We report a pulse Fe: ZnSe laser pumped by an optical chopper Q-switched Er: YAG laser. By analyzed the spatial and temporal match of the gain and chopper, the maximum energy of the optical chopper Q-switched Er: YAG laser is 31mJ with the pulse width of 165 ns. By employing this Er: YAG laser as pump laser of Fe: ZnSe crystal, the maximum output energy of Fe: ZnSe laser is 10mJ with the pulse width of 80 ns at room temperature, that is the maximum energy of Fe: ZnSe laser at this Q-switched system to the best of our knowledge. We also study the directly Q-switched Fe: ZnSe laser, and the 2.7mJ mid-infrared laser with the pulse width of 200 ns is obtained at 80 K.

A Review of Cr2+ or Fe2+ Ion-Doped Zinc Sulfide and Zinc Selenide Ceramics as IR Laser Active Media

Zinc chalcogenides doped with Cr2+ or Fe2+ ions are of considerable interest as active media for IR lasers operating in the 2–5 µm wavelength range. Such lasers are in demand in various fields of medicine, remote sensing and atmospheric monitoring, ranging, optical communication systems, and military applications. In recent years, however, the rate of improvement in the characteristics of zinc chalcogenide laser sources has slowed considerably. Unwanted thermally induced effects, parasitic oscillations, and laser-induced damage of the active element have hindered the scaling of output power and efficiency. However, the physical and chemical properties of the materials leave ample room for further improvements. In particular, the control of the dopant concentration profile in the active element is of great importance. Zero concentration of Cr2+ or Fe2+ ions on the radiation input/output surfaces can significantly increase the laser-induced damage threshold; the designed concentration distribution in the element volume allows regulation of heat dissipation and reduction of parasitic oscillations. The zinc chalcogenide ceramic technology seems to be the most suitable to solve this challenge. This review presents and discusses the state of the art in ZnS and ZnSe optical and laser ceramics and the directions for further development of their technology.

High-resolution mid-infrared spectroscopy based on ultrafast Cr:ZnSe laser.

High-resolution broadband direct frequency comb spectroscopy in the mid-infrared spectral region is an extremely powerful and versatile experimental technique that allows study of the molecular structure of gaseous compounds with multiple applicative and scientific implications. Here we present the first implementation of an ultrafast Cr:ZnSe mode-locked laser covering more than 7 THz at around the emission wavelength of 2.4 μm, for direct frequency comb molecular spectroscopy with a frequency sampling of 220 MHz and a frequency resolution of ∼100 kHz. This technique is based on a scanning micro-cavity resonator with a Finesse of ∼12,000 and a diffraction reflecting grating. We demonstrate its application in high-precision spectroscopy of the acetylene molecule by retrieving line center frequencies of more than 68 roto-vibrational lines. Our technique paves the way for real time spectroscopic studies as well as for hyperspectral imaging techniques.

Intensity Noise and Pulse Repetition Frequency Stability Measurements of a Passive Mode-Locked Cr:ZnSe Laser

Intensity Noise and Pulse Repetition Frequency Stability Measurements of a Passive Mode-Locked Cr:ZnSe Laser