Recent Breakthroughs in Solid‐State Mid‐IR Laser Technology

Abstract

Availability of compact and cost-efficient mid-infrared (MIR) laser sources with a broad range of parameters is of great interest for a number of current and emerging applications. For instance, femtosecond (fs) MIR sources with high average power and broad spectral span enable high dynamic range spectroscopy, sensing, and imaging in the molecular fingerprint region. On the other hand, few-optical-cycle MIR pulses with high energy are of particular importance for the development of EUV and X-ray sources based on strong field nonlinear optics, e.g. high harmonic generation. Furthermore, high-power mid-IR lasers are of interest for processing polymers, glasses and composites, surgical, dental and cosmetology procedures, as well as numerous defense-related applications.Introduced in 1970s, the first solid-state MIR lasers were based on alkali halide crystals with color centers or oxide and fluoride crystals doped with trivalent rare earth ions and required inconvenient cryogenic cooling of the gain medium. Transition-metal doped II-VI semiconductors (TM:II-VI) were introduced as a new class of gain media in the late 1990s by William Krupke's group at Lawrence Livermore National Laboratory, Livermore, CA [1]. By their design, TM:II-VI are effective MIR laser materials. Features of II-VI semiconductor hosts (wide bandgap, low phonon cutoff, tetrahedral coordination) are very favorable for doping by TM ions. Chemically stable divalent TM dopant ions provide the 'right' multiplet structure for broadly tunable MIR lasers, including broad absorption and emission bands, high cross-sections, and absence of excited state absorption.ZnS and ZnSe doped with Cr 2+ and Fe 2+ are typical and the best known representatives of the large TM:II-VI family, as reviewed in [2]. Advantages of Cr:ZnS and Cr:ZnSe lasers include room-temperature (RT) operation with close to 100 % quantum efficiency, very broad tuning over 1.9 -3.4 µm range, and convenient pumping by reliable erbium (Er) and thulium (Tm) fiber lasers with pump conversion efficiency in excess of 60 %. Broad emission bands of Crdoped ZnS and ZnSe are favorable for generation of ultra-short pulses; these materials are often referred to as the "Ti:sapphire of the middle IR". In many respects, Fe:ZnS and Fe:ZnSe lasers are complimentary to Cr-based sources. They are pumped in the 2.5 -3.3 µm range and tunable over 3.4 -5.2 µm range; they operate at RT in the nanosecond (ns) pulsed regime but require cooling to about 150 K in the continuous wave (cw) regime.Cr (or Fe) doped ZnS and ZnSe have very similar spectroscopic and laser parameters. Physical properties of ZnS, e.g. reduced thermal-optical effects and wider bandgap are advantageous in high power laser applications, while ZnSe has higher nonlinearity. The choice between ZnS and ZnSe hosts is usually defined by the specific laser parameter requirements. Both materials are available in single crystal and in polycrystalline forms. Single-crystals of high optical quality and sufficiently high dopant concentrations are difficult ...

Petawatt and exawatt class lasers worldwide

“…They allow the production of pulses as short as 380 fs [269] by themselves and can be used additionally as a pump for another ultra-broadband laser material, which will offer the two-step approach. Suitable materials for such a scheme are the transition-metal-doped zinc chalcogenides [270][271][272][273] . Since the pioneering work of DeLoach et al in 1996 [274] showing a slope efficiency of 22% with Cr:ZnSe, many promising results have been produced.…”

Применение ИК Микроскопии Для Прецизионного Контроля Диффузионных Профилей Распределения Примесей Железа И Хрома В Халькогенидах Цинка

“…Халькогениды цинка, легированные двухвалентными ионами хрома и железа, являются перспективными материалами для создания активных сред лазеров, излучающих в среднем ИК диапазоне (1.9−5 µm) [1][2][3][4][5]. Источники лазерного излучения данного диапазона широко используются в самых различных областях, включая молекулярную спектроскопию, мониторинг окружающей среды, медицину, дальнометрию, оптическую связь и др.…”

“…Выходные характеристики лазеров на ZnSe(S):Cr 2+ (Fe 2+ ) во многом зависят от способа введения допанта и структуры материала генерирующей среды [3,6]. Применяют различные способы изготовления лазерных сред: диффузионное легирование предварительно синтезированного материала, чаще всего полученного методом химического осаждения из газовой фазы (CVD), легирование в процессе выращивания из расплава, физическое осаждение из пара (PVD) [3,5].…”

Broadband mid‐infrared emission from Cr2+ in crystal‐in‐glass composite glasses by Hot Uniaxial Pressing

“…| 6619 XIA et Al. or femtosecond-pulsed lasers [6][7][8] . Cr 2+ can be stably present in tetrahedral coordinated ZnSe crystals to produce an effectively tunable MIR laser, but it is impossible in chalcogenide glasses.…”