Near-infrared Solid-state Lasers Research Articles

Terawatt-class femtosecond long-wave infrared laser

We utilized a nonlinear post-compression technique to generate 675-fs, 9.2-μm CO2 laser pulses with a peak power of 1.6 TW. This achievement represents the highest peak power ever attained in the femtosecond pulse format within the long-wave infrared (LWIR) spectral range. The successful implementation of this post-compression technique opens avenues for the development of few-cycle, multi-terawatt 9–10 μm lasers, crucial for applications currently relying on near-infrared solid-state lasers, and which stand to benefit from the scaling of laser wavelengths into the long-wave infrared region.

Oxygen vacancies in LiB3O5 crystals and their role in nonlinear absorption

LiB3O5 (LBO) crystals are used to generate the second, third, and fourth harmonics of near-infrared solid-state lasers. At high power levels, the material’s performance is adversely affected by nonlinear absorption. We show that as-grown crystals contain oxygen and lithium vacancies. Transient absorption bands are formed when these intrinsic defects serve as traps for “free” electrons and holes created by x rays or by three- and four-photon absorption processes. Trapped electrons introduce a band near 300 nm and trapped holes produce bands in the 500-600 nm region. Electron paramagnetic resonance (EPR) is used to identify and characterize the electrons trapped at oxygen vacancies (the unpaired electron is localized on one neighboring boron). Self-trapped holes and lithium vacancies with the hole trapped on an adjacent oxygen are also observed with EPR. At room temperature, we predict that most of the unwanted defect-related ultraviolet absorption created by a short laser pulse will decay with a half-life of 29 µs.

Passively Q-switched 914 nm microchip laser for lidar systems.

Passively Q-switched microchip lasers enable great potential for sophisticated lidar systems due to their compact overall system design, excellent beam quality, and scalable pulse energies. However, many near-infrared solid-state lasers operate at >1000 nm which are not compatible with state-of-the-art silicon detectors. Here we demonstrate a passively Q-switched microchip laser operating at 914 nm. The microchip laser consists of a 3 mm long Nd3+:YVO4 crystal as a gain medium while Cr4+:YAG with an initial transmission of 98% is used as a saturable absorber. Quasi-continuous pumping enables single pulse operation and low duty cycles ensure low overall heat generation and power consumption. Thus, thermally induced instabilities are minimized and operation without active cooling is possible while ambient temperature changes are compensated by adjustment of the pump laser current only. Single-emitter diode pumping at 808 nm leads to a compact overall system design and robust setup. Utilization of a microchip cavity approach ensures single-longitudinal mode operation with spectral bandwidths in the picometer regime and results in short laser pulses with pulse durations below 10 ns. Furthermore, beam quality measurements show that the laser beam is nearly diffraction-limited. A 7% output coupler transmittivity is used to generate pulses with energies in the microjoule regime and peak powers of more than 600 W. Long-term pulse duration, pulse energy, and spectral wavelength measurements emphasize excellent system stability and facilitate the utilization of this laser in the context of a lidar system.

Tellurium as the saturable absorber for the passively Q-switched laser at 1.34 µm.

The novel two-dimensional (2D) elementary tellurium is currently of great interest in optoelectronic and photonic applications. In this contribution, 2D tellurium nanosheets were successfully created by using the liquid-phase exfoliation method. With the as-prepared tellurium nanosheets as the saturable absorber (SA), we realized a passively $ Q $Q-switched ${\rm Nd} \text:{{\rm YVO}_4}$Nd:YVO4 laser operating at 1342 nm with a pulse width of 947 ns and single pulse energy of 2.25 µJ. Our work indicated the tellurium SA could be an efficient $ Q $Q-switcher for a near-infrared solid-state laser.

Near-Infrared Solid-State Lasers Based on Small Organic Molecules

Organic solid-state lasers (OSSLs) have undergone great progresses in the past two decades and will boost the society development since the realization of electrically pumped OSSLs in 2019. Signifi...

Electrical and optical properties of glasses and glass-ceramics

In this work, the electrical and optical properties of glasses and glass-ceramics are presented and discussed in details. Several electrical and optical parameters for glasses and glass-ceramics were determined. The conduction activation energy and DC conductivity depend on temperature, glass composition and concentration of glass modifiers. The optical properties of glasses and glass-ceramics containing Er3+ (or Er3+/Yb3+) ions have been analyzed for near-infrared luminescence centered at about 1.5 μm and up-conversion applications. In particular, luminescence bandwidths and lifetimes for the 4I13/2 → 4I15/2 transition of Er3+ were determined as a function of host-matrices and then examined for near-infrared solid-state lasers and broadband optical amplifiers. The green up-conversion luminescence spectra for Er3+ and Er3+/Yb3+ doped systems are temperature-dependent and can be used to optical sensors.

Luminescence Properties of Nd-Doped Strontium Aluminate with Six Coordination Sites

Neodymium-doped phosphors have been applied to laser materials due to their potential for high efficiency and compactness. Among them, neodymium-doped yttrium aluminum garnet (Nd:YAG) was widely used as a medium material for near-infrared solid-state lasers. In this study, we focused on a novel neodymium-doped strontium aliminate phosphor, Nd:Sr3Al2O6. This crystal, which has cubic system (Pa-3), has the potential as a transparent polycrystalline ceramic. Additionally, the phosphor contains six Sr2+ sites that neodymium ions substitute. We prepared this phosphor by conventional solid state reaction using SrCO3 (99.9%), γ-Al2O3 (99.9%), and Nd(NO3)3・6H2O (99.9%). These starting materials were mixed in an alumina mortar, and all mixtures were sintered under air atmosphere. The crystal structure of a prepared sample was characterized by using X-ray diffraction. The diffraction pattern of the sample agreed with that of JCPDS for Sr3Al2O6 (24-1187). Luminescence properties were estimated by using emission spectrum and lifetime. The 4f-4f emission of Nd3+ was broad compared with that of Nd:GdVO4, which has a broader emission band than that of Nd:YAG. Nd:Sr3Al2O6 is potentially applicable to Nd-doped solid-state laser with a broad emission band.

Spectroscopic Investigation on BaSO4:(Mn6+, Mn5+) Crystal

BaSO4:(Mn6+, Mn5+) crystal was grown using MnCO3 as manganese source at high temperature from 650 to 750°C by the NaCl-KCl flux method in air and its spectroscopic properties were investigated. The experimental results indicate that Mn6+ and Mn5+ ions coexisted in the crystal. A broadband emission band peaking at ∼1060 nm due to the 2T2 → 2E transition of Mn6+ ion and a sharp emission band peaking at ∼1183 nm due to the 1E → 3A2 transition of Mn5+ ion were observed. Mn-doped BaSO4 single crystal may be a promising candidate as tunable near-infrared solid-state laser material.

Semiconductor-doped glass saturable absorbers for near-infrared solid-state lasers

A survey of results on use of semiconductor-doped glass saturable absorbers for near-infrared passively mode-locked and Q-switched solid-state lasers is presented. Nanosized semiconductor particles (quantum dots) belong to quantum confined systems where motion of an electron and a hole is defined by the finite size of the nanoparticle. Dependence of the excitonic transition energy on the QDs size provides the possibility to tune the absorption of the glasses embedded with such particles to wavelength of specific light source. IV-VI semiconductor QDs (PbS, PbSe) are of interest for IR application due to their narrow band gap and large exciton Bohr radii. These allow for exciton absorption band at the wavelength through 1–3μm. Nonlinear optical properties of PbS, PbSe, and CuxSe nanoparticles embedded in glass matrices necessary for saturable absorber applications are analyzed. It is shown that these materials can be efficiently used for passive mode locking and Q switching of solid-state lasers based on Nd3+, Yb3+, Cr4+, Tm3+, and Ho3+ ions emitting through 1–2.1μm spectral range.

An accurate comparison of lineshape models on H 2O lines in the spectral region around 3 μm

In this paper we present the main results concerning lineshape analysis on ν 1 and ν 3 water vapor lines in the region around 3 μm. Narrow-bandwidth radiation used in this experiment was produced by difference-frequency generation in a periodically poled crystal between two near-infrared solid state lasers. We have investigated pressure broadening and shift for five H 2O absorption lines induced by collisions with Xe atoms and water vapor itself. From an accurate lineshape analysis we have obtained information on the influence of Dicke narrowing as well as correlations between velocity-changing and dephasing collisions and of speed-dependent effects. Finally, the self-broadening and pressure broadening and shift coefficients in presence of the buffer gas are furnished.

Analysis of a potassium lidar system for upper-atmospheric wind–temperature measurements

We report a detailed analysis of wind-temperature (W/T) lidar systems based on mesospheric potassium as the tracer. Currently, most narrow-band (W/T) systems use sodium (Na) as the tracer because of its relatively large natural abundance, large cross section, and the ability to use Doppler-free Na spectroscopy to generate accurate absolute frequency markers. We show that a potassium-based system with existing near-infrared solid-state laser technology operating at the potassium D lines has the potential to make W/T measurements that are more accurate than current Na narrow-band systems and can be far simpler technically.