ZnSe Laser Research Articles

Gain-switched Fe:ZnSe laser pumped by a coupled-cavity Q-switched Er:ZrF4 fiber laser.

We report on a gain-switched operation of single-crystal Fe2+:ZnSe pumped by a coupled-cavity Q-switched Er3+:ZrF4 fiber laser. With this approach, we use a continuous wave Er-doped ZrF4 fiber laser whose cavity is coupled with the Fe:ZnSe laser cavity. A stable Q switching operation of the Er-doped fiber laser was achieved in this case and, as a result, a gain-switched operation of the Fe:ZnSe laser was obtained. The highest repetition rate was 79 kHz, the pulse duration of the pump Er-doped laser was ∼1.6 μs, and the pulse duration of the Fe:ZnSe was 62 ns. The maximum output power achieved from gain-switched Fe:ZnSe was 63 mW.

Diode-Pumped Intracavity OPO KTP/YAG:Nd3+ laser for Cr2+:ZnSe pumping

Electro-optically Q-switched side-pumped diode-pumped KTP/YAG:Nd3+ nanosecond laser system with an intracavity collinear optical parametric oscillation was proposed as a pump source for Cr2+:ZnSe laser. Energy parameters of Cr2+:ZnSe laser were investigated with respect to the wavelength of the pump laser. Under optimal conditions, pumping with laser pulses with an energy of 10.5 mJ and a duration of 7.2 ns at a wavelength of 1950 nm allowed to obtain 3.2 ns pulses at a wavelength of 2494 nm with slope optical-to-optical conversion efficiency of 5.5%.

Lasing and luminescence characteristics of Fe:CdTe single crystal at room temperature

A technology for obtaining high-quality single-crystal active elements for a Fe:CdTe laser was described, which includes growing a single crystal from a melt using a modified vertical gradient freeze method followed by high-temperature treatment to remove free charge carriers. The room-temperature lasing and luminescence characteristics of a Fe:CdTe single crystal with a Fe2+ ions concentration of 6.1 × 1018 cm−3 were studied. The upper laser level lifetime, the output energy and a slope efficiency with respect to absorbed energy of the Fe:CdTe laser excited by the Fe:ZnSe laser were 340 ns, 13.5 mJ and 32%, respectively. The lasing spectrum of the Fe:CdTe laser with a nonselective cavity was located within the range 5.63–6.02 μm. It was noted the possibility to control the lasing spectrum by changing the pump laser spectrum (shifting the Fe:ZnSe laser spectrum to the short- or long-wavelength region by changing the quality factor of the cavity). Ways are discussed for further increasing the output energy of a Fe:CdTe laser at room temperature of the active element, in particular, by using a nonchain electric-discharge DF laser for pumping.

DF laser pumped single-crystal Fe:CdTe laser operating at room temperature

The operation at room temperature of a single-crystal Fe:CdTe laser excited by a nonchain electric-discharge DF laser was studied. The output energy of 29 mJ was obtained with a slope efficiency in terms of absorbed energy of 30%. The development of transverse parasitic oscillation at large pump spot sizes on the crystal surface limited the laser output energy. The laser with a nonselective cavity operated in the range of 5.3–5.9 μm; the total width of the generation spectrum was about 600 nm. Comparison of the Fe:CdTe generation spectra, obtained by pumping the crystal with DF and Fe:ZnSe lasers, confirmed the shift of the generation spectrum to the long wavelength region with increasing pump wavelengths. The maximum generation wavelength of the Fe:CdTe laser with a nonselective resonator excited by the Fe:ZnSe laser was 6.02 μm with a total width of the generation spectrum of about 370 nm. Ways are discussed for further increasing the room-temperature output energy of a Fe:CdTe laser.

Diffuse reflectance spectroscopy of the cartilage tissue in the fourth optical window.

Studies of the optical properties of biological tissues in the infrared range have demonstrated significant potential for diagnostic tasks. One of the insufficiently explored ranges for diagnostic problems at the moment is the fourth transparency window, or short wavelength infrared region II (SWIR II). A Cr2+:ZnSe laser with tuning capability in the range from 2.1 to 2.4 µm was developed to explore the possibilities in this region. The capability of diffuse reflectance spectroscopy to analyze water and collagen content in biosamples was investigated using the optical gelatin phantoms and the cartilage tissue samples during their drying process. It was demonstrated that decomposition components of the optical density spectra correlated with the partial content of the collagen and water in the samples. The present study indicates the possibility of using this spectral range for the development of diagnostic methods, in particular, for observation of the changes in the content of cartilage tissue components in degenerative diseases such as osteoarthritis.

Effect of the Length and Pressure of a Gas Jet on Optical Harmonics Generation by 4.5-μm Femtosecond Laser Radiation of a Fe:ZnSe Laser System

The effect of the length and pressure of an argon gas jet on low-order harmonics (5th, 7th, 9th, and 11th) generation by 4.5-μm femtosecond laser radiation of a Fe:ZnSe laser system has been studied experimentally. It has been shown that an increase in the length of the generation medium up to the waist length allows one to increase the generation efficiency by a factor of 12. It has also been demonstrated that a change in the length of the gas medium changes the pressure dependence of the energy of the generated radiation because of change in the phase matching conditions, whose correct simulation requires the inclusion of nonlinear propagation effects for pump pulse and generated harmonics.

A hybrid quantum cascade laser/Fe:ZnSe amplifier system for power scaling of CW lasers at 4.0–4.6 µm

A hybrid continuous-wave Fe:ZnSe laser amplifier seeded with a mid-infrared quantum cascade laser is demonstrated. A maximum output power of 870 mW with an extraction efficiency of 30 % was achieved from the Fe:ZnSe amplifier seeded by a 200-mW laser at 4.0 µm, corresponding to a gain of approximately 4.4. When the amplifier was seeded by a 150-mW laser at 4.6 µm, an effective gain of approximately 1.4 was obtained. Additionally, we present a theoretical analysis to provide possible routes for further optimization of this Fe:ZnSe amplifier system.

Mid-infrared electronic wavelength tuning through intracavity difference-frequency mixing in Cr:ZnSe lasers

Mid-infrared tunable coherent light sources are used in various laser applications, such as trace gas detection, laser processing, and biomedical diagnostics. This study demonstrates mid-infrared generation in the 8.3–11 µm (i.e., 900–1200 cm−1) spectral range by configuring intracavity difference-frequency generation (DFG) using ZnGeP2 (ZGP) in an electronically tuned Cr:ZnSe laser. The broad tunability is achieved with the maximum pulse energies exceeding 100 μJ by combining the electronic wavelength tuning with sligh angle adjustments (Δθ < 0.5°) of ZGP under the spectral noncritical phase-matching condition of the nonlinear material. The proposed DFG method is generalized to give access to a significant fraction of the molecular fingerprint region by utilizing selenide compounds (e.g., AgGaSe2, CdSe) in addition to ZGP, revealing the remarkable potential of ultrabroadband electronic mid-infrared scanning for numerous spectroscopic applications.

Second and third-order dispersion compensating mirror pairs for the spectral range from 1.2-3.2µm.

We demonstrate the design, production, characterization and application of two dispersive complementary mirror pairs compensating second- and third-order dispersion, respectively. Both mirror pairs operate in the spectral range from 1.2-3.2µm. This is an unprecedented bandwidth of over 1.4 octaves which can drive further improvements in Cr:ZnS, Cr:ZnSe and other laser systems with a central wavelength around 2µm. The first pair provides a constant group delay dispersion of -100fs2, while the second one enables the compensation of the third-order dispersion that is introduced by a TiO2 crystal.

Mid-Infrared Laser Generation of Zn1-xMnxSe and Zn1-xMgxSe (x ≈ 0.3) Single Crystals Co-Doped by Cr2+ and Fe2+ Ions-Comparison of Different Excitation Wavelengths.

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr, Fe:ZnMnSe and Cr, Fe:ZnMgSe with similar amounts of manganese or magnesium ions of x ≈ 0.3 were investigated at cryogenic temperatures for three different excitation wavelengths: Q-switched Er:YLF laser at the wavelength of 1.73 m, Q-switched Er:YAG laser at 2.94 m, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 m. The temperature dependence of spectral and laser characteristics was measured. Depending on the excitation wavelength and the selected output coupler, both laser systems were able to generate radiation by Cr or by Fe ions under direct excitation or indirectly by the Cr→ Fe energy transfer mechanism. Laser generation of Fe ions in Cr, Fe:ZnMnSe and Cr, Fe:ZnMgSe (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 m at a temperature of 78 K was achieved, respectively. The excitation of Fe ions in both samples by direct 2.94 m as well as ∼4.05 m radiation or indirectly via the Cr→ Fe ions’ energy transfer-based mechanism by 1.73 m radiation was demonstrated. Based on the obtained results, the possibility of developing novel coherent laser systems in mid-IR regions (∼2.3–2.5 and ∼4.4–4.9 m) based on AB matrices was presented.

Hot-isostatic-pressed Cr:ZnSe ultrafast laser at 2.4 [formula omitted

We report on a room temperature Kerr-lens mode-locked chromium-doped zinc selenide (Cr:ZnSe) laser emitting four optical-cycles pulses in the mid-infrared spectral region in which the laser polycrystal has been treated by hot isostatic pressing (HIP). The laser emits 34 fs pulses at 2.4 μm, with a repetition rate of 171 MHz and average output power capabilities of up to 150 mW. This is the first mode-locking investigation conducted using the HIP treated material and to our knowledge, is the shortest pulse width demonstrated, to date, from polycrystalline Cr:ZnSe. The experimental comparison with respect to an untreated polycrystal indicates that HIP treatment is advantageous for mode-locking action of this active material.

Mid-infrared-scanning cavity ring-down CH2F2 detection using electronically tuned Cr:ZnSe laser

The development of mid-infrared (mid-IR) tunable lasers has been driving various laser spectroscopic technologies. Herein, we report wavelength-scanning cavity ring-down spectroscopy (WS-CRDS) in the mid-IR region using an electronically tuned Cr:ZnSe (ET-Cr:ZnSe) laser, which could achieve a nanosecond pulse operation, with broad wavelength tuning of 2–3 µm. This allowed WS-CRDS-induced trace detection of the refrigerant, CH2F2. A CH2F2 detection limit of 0.66 ppm (3σ), and the detection of trace H2O in CH2F2 was realized using the broad wavelength-tuning range feature, demonstrating the effectiveness of the ET-Cr:ZnSe laser in WS-CRDS. We believe that our method would accelerate the development of various trace-gas detection technologies.

Theoretical characteristics of mid-infrared gain switched pulsed iron-doped ZnSe laser

We report a four-level theoretical model revealing the laser kinetics of a gain-switched pulsed Fe2+:ZnSe laser that is established for the first time, to the best of our knowledge. The experimental results agree with the theoretical primary spike pulse and relaxation oscillation phenomenon of pulse. Furthermore, the effects of temperature, doping concentration, and the output coupler reflectivity on the performance of the pulsed Fe2+:ZnSe laser are simulated using the proposed model. The simulated results indicate that the laser efficiency is higher at low temperature and high Fe2+ concentrations, and the optimal output coupler reflectivity is ∼23% at 77 K.

Optical Harmonics Generation under the Interaction of Intense (up to 1014 W/cm2) Mid-Infrared Femtosecond Laser Radiation of a Fe:ZnSe Laser System with a Dense Laminar Gas Jet

Optical Harmonics Generation under the Interaction of Intense (up to 1014 W/cm2) Mid-Infrared Femtosecond Laser Radiation of a Fe:ZnSe Laser System with a Dense Laminar Gas Jet

Burst pulse generation in Cr:ZnSe laser with mid-infrared tunability

We demonstrated a nanosecond pulsed Cr:ZnSe laser with both wavelength tunability and burst pulse operation in the mid-infrared (IR) region. The burst pulse operation of the Cr:ZnSe laser was achieved using a pulse-on-demand Tm:YAG laser as a pump source. The number of pulse shots and the repetition rate in a packet were controlled. A tuning range of 2.32 to 2.56 μm was also achieved using a birefringent filter. Our results show that the pulse-on-demand Tm:YAG laser is an attractive pump source for the burst-pulse-operated Cr:ZnSe laser, which paves the way for various mid-IR laser applications.

Direct electric-field reconstruction of few-cycle mid-infrared pulses in the nanojoule energy range.

Amid the increasing potential of ultrafast mid-infrared (mid-IR) laser sources based on transition metal doped chalcogenides such as Cr:ZnS, Cr:ZnSe, and Fe:ZnSe lasers, there is a need for direct and sensitive characterization of mid-IR mode-locked laser pulses that work in the nanojoule energy range. We developed a two-dimensional spectral shearing interferometry (2DSI) setup to successfully demonstrate the direct electric-field reconstruction of Cr:ZnS mode-locked laser pulses with a central wavelength of 2.3 µm, temporal duration of 30.3 fs, and energies of 3 nJ. The reconstructed electric field is in reasonable agreement with an independently measured intensity autocorrelation trace, and the quantitative reliability of the 2DSI measurement is verified from a material dispersion evaluation. The presented implementation of 2DSI, including a choice of nonlinear crystal as well as the use of high-throughput dispersive elements and a high signal-to-noise ratio near-IR spectrometer, would benefit future development of ultrafast mid-IR lasers and their applications.

Hot-pressed Fe2+:ZnSe transparent ceramics with different doping concentrations

In this study, Fe 2+ :ZnSe transparent ceramics with different doping concentrations were prepared from annealed FeSe and ZnSe powders by hot pressing. The as-prepared ceramics consisted of a cubic ZnSe phase and compact microstructures. Doping concentrations of Fe 2+ ions in the range 0.66–3.05 at.% were accurately realised, which could influence the absorption intensity of Fe 2+ :ZnSe transparent ceramics. An absorption peak was observed at ∼3 μm, and its intensity could be controlled by the concentration of Fe 2+ ions. Fe x Zn 1- x Se (0.0066 ≤ x ≤ 0.0305) ceramics with Fe 2+ ions concentrations in the range 0.66–3.05 at.% exhibited significant absorption cross sections from 0.6676 × 10 −19 to 0.1075 × 10 −18 cm 2 . The specimen doped with 1.55 at.% Fe 2+ ions displayed the highest transmittance of 67% at a wavelength of 14 μm and a carbonate absorption peak at 9 μm. The proposed transparent ceramic technique appears promising for preparing Fe 2+ :ZnSe laser gain media because of its advantage of allowing control over Fe 2+ concentration.

Intensity noise and pulse repetition frequency stability measurements of a passive mode-locked Cr:ZnSe laser

The results on intensity noise and repetition frequency stability measurements for a passively mode-locked Cr : ZnSe laser pumped by a thulium-doped fiber laser at a wavelength of 1.94 μm are presented. The stability parameters and intensity noise are compared for three different generation regimes of the Cr:ZnSe laser. The laser operated at a repetition rate of 129.5 MHz and a central wavelength of 2.45 μm. Keywords: optical frequency comb, mode-locking, relative intensity noise, repetition frequency stability.

Измерение шумов интенсивности и стабильности частоты повторения импульсов Сr:ZnSe-лазера с пассивной синхронизацией мод

The results on intensity noise and repetition frequency stability measurements for a passive mode-locked Cr:ZnSe laser pumped by a thulium-doped fiber laser at a wavelength of 1.94 µm are presented. The stability parameters and intensity noise are compared for three different generation regimes of the Cr:ZnSe laser. The laser operated at a repetition rate of 129.5 MHz and a central wavelength of 2.45 µm.

High-efficiency, continuous-wave Fe:ZnSe mid-IR laser end pumped by an Er:YAP laser

Fe:ZnSe lasers operating in the mid-IR spectral region have gained widespread attention due to their numerous potential applications. This study presents a high-efficiency, continuous-wave Fe:ZnSe laser end pumped by an Er:YAP laser at 2920 nm. The Er:YAP laser was home-constructed and generated an output power of 3.6 W and an average slope efficiency of 36.6% with a good beam quality (M2 ≤ 2). The Fe:ZnSe laser produced a maximum output power of 1 W at 4.06 µm for 2.1 W of absorbed pump power, corresponding to an average slope efficiency of 48%. Theoretical modeling of the continuous-wave Fe:ZnSe laser is presented to determine the prospects for further power scaling.